Engineering Encyclopedia: Commissioning Low-Voltage Switchgear And Circuit Breakers

Engineering Encyclopedia Saudi Aramco DeskTop Standards

Commissioning Low-Voltage Switchgear And Circuit Breakers

Note: The source of the technical material in this volume is the Professional Engineering Development Program (PEDP) of Engineering Services. Warning: The material contained in this document was developed for Saudi Aramco and is intended for the exclusive use of Saudi Aramco’s employees. Any material contained in this document which is not already in the public domain may not be copied, reproduced, sold, given, or disclosed to third parties, or otherwise otherwise used in whole, or in part, without the written written permission permission of the Vice President, Engineering Services, Saudi Aramco.

Chapter : Electrical File Reference: EEX30208

For additional information on this subject, contact W.A. Roussel on 874-6160

Engineering Encyclopedia

Electrical Commissioning Low-Voltage Switchgear and Circuit Breakers

Content

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INTRODUCTION................................................................................................................ INTRODUCTION................................................................................................................ 1 SAUDI ARAMCO ARAMCO COMMI COMMISSION SSIONING ING REQUIRE REQUIREMENTS MENTS ................................................ 2 Switchgear Switchgear ................................................................................................................ 2 Circuit Circuit Breakers Breakers ........................................................................................................ 5 EVALUATING LOW-VOLTAGE SWITCHGEAR AND CIRCUIT CIRCUIT BREAKERS BREAKERS UPON UPON RECEIPT RECEIPT ................................................................... 9 Visual Visual Inspe Inspecti ction....................................................................................................... on....................................................................................................... 9 Verifi Verificat cation ion Agains Againstt Specifi Specificat cations ions ............................................................................ 9 Low-Voltage Low-Voltage Switchgea Switchgearr Nameplat Nameplate.............................................................10 e.............................................................10 Circuit Circuit Breaker Breaker Nameplat Nameplate............................................................................11 e............................................................................11 EVALUATING LOW-VOLTAGE SWITCHGEAR AND CIRCUIT BREAKER INSTALLATI INSTALLATION ON AND TESTING......................................................................................13 TESTING......................................................................................13 Visual Visual Inspect Inspection......................................................................................................13 ion......................................................................................................13 Suitab Suitabil ility ity .....................................................................................................14 Physi Physical cal Damage...........................................................................................15 Damage...........................................................................................15 Alignment.....................................................................................................15 Clean Cleanli lines ness....................................................................................................15 s....................................................................................................15 Arc Chute Chute Assemb Assembly ly .....................................................................................17 Contacts Contacts .......................................................................................................17 Mechani Mechanism/ sm/Lin Linkag kagee ......................................................................................18 Lubricat Lubrication ion ...................................................................................................18 Mechanic Mechanical al Inspect Inspection ion ..............................................................................................18 Bolt Torque..................................................................................................19 Door Operation Operation ............................................................................................19 Rack In - Rack Out.......................................................................................19 Open/Clos Open/Closee Operatio Operation...................................................................................20 n...................................................................................20 Electri Electrical cal Inspect Inspection ion .................................................................................................21 Insulat Insulation ion Resist Resistance.....................................................................................2 ance.....................................................................................22 2 Contact Contact Resistanc Resistance........................................................................................23 e........................................................................................23

Saudi Aramco DeskTop Standards



Function Functional al Operatio Operation n ....................................................................................23 Auxili Auxiliary ary Equipm Equipment ent .....................................................................................24 SYSTEM PRE-OPERATIO PRE-OPERATIONAL NAL CHECK-OUT PHASE REQUIREMENTS REQUIREMENTS .....................25 Point-toPoint-to-Point Point Wiring Check ....................................................................................25 Subsystem Subsystem Checkout Checkout ................................................................................................25 Interlocks Interlocks.................................................................................................................25 .................................................................................................................25 SYSTEM OPERATIONAL OPERATIONAL TESTING TESTING PHASE REQUIREMENTS....................................26 REQUIREMENTS....................................26 WORK WORK AID 1: 1: REFERENCES REFERENCES FOR FOR EVALUAT EVALUATING ING LOW-VO LOW-VOLTAG LTAGE E SWITCHGEAR AND CIRCUIT CIRCUIT BREAKERS UPON RECEIPT RECEIPT ............ ...... ........27 ..27 Low-Voltage Switchgear Switchgear and Circuit Circuit Breaker Breaker Applicati Applications ons Checklist Checklist ............ ...... ............ ...........34 .....34 WORK WORK AID 2: 2: REFERENCES REFERENCES FOR FOR EVALUAT EVALUATING ING LOW-VO LOW-VOLTAG LTAGE E SWITCHGEAR AND CIRCUIT BREAKER INSTALLATION AND TESTING.........................................................................................35 TESTING.........................................................................................35 NETA Checklists......... Checklists............... ............ ............. ............. ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ........35 ..35 Information, Formulas, and Tables for Use in Evaluating the Results of Insulati Insulation on Resista Resistance nce (Megger) (Megger) Tests .......................................................................44 Saudi Aramco Pre-Commissioning Forms.................................................................45 GLOSSARY........................................................................................................................56

-----------------------------------------------------------------------------------------------------------------Table of Figures

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Figure Figure 1: Westingho Westinghouse use Type Type DS Low-Volt Low-Voltage age Switchge Switchgear ar Section Section ......................... 3 Figure Figure 2: GE AKR Manual Manual Low-Vol Low-Voltage tage Circuit Circuit Breaker......................................... Breaker......................................... 6 Figure 3: GE AKR Low-Volta Low-Voltage ge Circuit Circuit Breaker Breaker Contact Struct Structure......................... ure......................... 7 Figure 7: Saudi Aramco Low-Voltage Power Switchgear Switchgear Requirements Requirements (From 16-SAM 16-SAMSS-502 SS-502)) ..........................................................................28 Figure 8: Low-Voltage Switchgear Buyer Data Sheet........ Sheet.. ............ ............ ............ ............ ............ ............ ........29 ..29 Figure 8: Low-Voltage Switchgear Buyer Data Sheet (Cont'd) ............ ...... ............ ............ ............ ........30 ..30 Figure Figure 9: Low-Volta Low-Voltage ge Switchgear Switchgear Vendor Vendor Data Sheet Sheet ...........................................31




Figure 10: Low-Voltage Power Circuit Breaker Rating, Rating, Design, Construction, Construction, and Auxiliary Auxiliary Device Installation Installation Requirements Requirements ............ ...... ...........32 .....32 Figure 10: Low-Voltage Power Circuit Circuit Breaker Rating, Design,Construction, Design,Construction, and Auxiliary Auxiliary Device Device Installa Installation tion Requireme Requirements nts (Cont'd) ............ ...... ............ ............ .......33 .33 Figure 11: Low-Voltage Switchgear Construction Construction General General Requirements ............ ...... ..........39 ....39 Figure 12: Low-Voltage Switchgear Stationary Structure Requirements....... Requirements. ............ ...........40 .....40 Figure 13: Low-Voltage Switchgear Bus Construction Construction Requirements ............ ...... ............ ..........41 ....41 Figure 14: Low-Voltage Switchgear Switchgear Bus Connection Connection and Cable Termination Termination Construct Construction ion Requireme Requirements nts .....................................................................42 Figure 15: Low-Voltage Switchgear Switchgear Nameplate Nameplate Construction Construction Requirements............43 Requirements........ ....43 Figure 16: Dielectric Absorption Ratio Chart........ Chart.. ............ ............ ............ ............ ............ ............ ............ ............ .........44 ...44 Figure 17: Saudi Aramco Pre-Commis Pre-Commissioning sioning Form, Form, P-023, Switchgear-General... Switchgear-General.....46 ..46 Figure 17: Saudi Aramco Pre-Commissioning Form, P-023, Switchgea Switchgear-Ge r-General neral (Cont'd) (Cont'd) ...................................................................47 Figure 17: Saudi Aramco Pre-Commissioning Form, P-023, Switchgea Switchgear-Ge r-General neral (Cont'd) (Cont'd) ...................................................................48 Figure 17: Saudi Aramco Pre-Commissioning Form, P-023, Switchgea Switchgear-Ge r-General neral (Cont'd) (Cont'd) ...................................................................49 Figure 18: Saudi Aramco Pre-Commissioning Form, P-008, Low-Voltage Low-Voltage Power Circuit Circuit Breakers......................................................50 Breakers......................................................50 Figure 18: Saudi Aramco Pre-Commissioning Form, P-008, Low-Voltage Low-Voltage Power Circuit Circuit Breakers Breakers (Cont'd)........................................51 (Cont'd)........................................51 Figure 18: Saudi Aramco Pre-Commissioning Form, P-008, Low-Voltage Low-Voltage Power Circuit Circuit Breakers Breakers (Cont'd)........................................51 (Cont'd)........................................51 Figure 18: Saudi Aramco Pre-Commissioning Form, P-008, Low-Voltage Low-Voltage Power Circuit Circuit Breakers Breakers (Cont'd)........................................52 (Cont'd)........................................52 Figure Figure 19: GI 2.l710 2.l710 Excerpt...................................................................................54 Excerpt...................................................................................54 Figure Figure 19: GI 2.l710 2.l710 Excerpt Excerpt (Cont'd) (Cont'd) .....................................................................55




INTRODUCTION

The selection of the type and size of switchgear and the associated power circuit breakers are based on the technical, installation, installation, and economic economic requirements requirements of a facility. facility. Facility Facility switchgear and circuit breaker technical requirements include the system voltage level, fault current, and the number and type of loads. Once the type of switchgear and circuit breakers for a given installation are chosen, the switchgear switchgear is assembled and the circuit breakers are installed. The commissioning process for low-voltage switchgear and circuit breakers in Saudi Aramco facilities ensures that a safe and cost-effective system is installed and that this system will perform to the specifications of the facility for the projected operating lifetime of the facility. Experience has shown that the time and effort that is expended up front to ensure safety, quality control, and adherence to Saudi Aramco and industry standards minimizes subsequent equipment failure. The commissioning process for low-voltage switchgear and circuit breakers involves evaluations, verifications, and checks that determine whether the proper switchgear and circuit breaker specifications and installation requirements are met. Tests are also performed that determine whether the electric power distribution system will operate properly and safely after installation. When the low-voltage switchgear and circuit breakers are inspected and tested satisfactorily during the commissioning process, the system should operate in accordance with manufacturer's specifications for its maximum useful life. This Module provides information on the following topics and subtasks that are pertinent to commissioning low-voltage switchgear and circuit breakers for Saudi Aramco installations: •

Saudi Aramco Commissioning Requirements

•

Evaluating Low-Voltage Switchgear and Circuit Breakers Upon Receipt

•

Evaluating Low-Voltage Switchgear and Circuit Breaker Installation and Testing

•

System Pre-Operational Check Out Phase Requirements

•

System Operational Testing Phase Requirements


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SAUDI ARAMCO COMMISSIONING REQUIREMENTS

Large process and process support equipment in industrial facilities requires electric power to function. Also, the operations, maintenance, and support personnel who work in an industrial facility require electric power for lights, fans, computers, and other support equipment. The electric power that is required to run equipment is passed through a distribution system that routes the electric power to the correct equipment. equipment. The distribution system system also provides electric power control capabilities capabilities,, as well as rapid fault fault isolation isolation and protection. protection. Low-voltage switchgear and the circuit breakers that are contained in the switchgear are a small but important part of the distribution distribution system. Low-voltage switchgear and circuit breakers generally supply power to support ancillary loads, such such as a cooling fan. This section of the Module contains information on Saudi Aramco applications and requirements for low-voltage switchgear and circuit breakers. Switchgear

Saudi Aramco uses compartmentalized, metal-enclosed, low-voltage switchgear assemblies in three-phase electric power systems that have a maximum of 600 V ac (rms) at a nominal frequency of 60 Hertz. When low-voltage power switchgear is received from the manufacturer, it is generally a finished product that is complete in all respects. respects. A finished low-voltage switchgear that is complete in all respects is factory assembled, wired, adjusted, and it includes power circuit breakers, buses, instruments, instruments, switches, wiring, space heaters, terminations, terminations, painting, nameplates, and tests (as required) so that the low-voltage switchgear is ready for operation when it is set in place. The low-voltage switchgear switchgear bus connections and cable terminations terminations must be in accordance with Saudi Aramco and industry requirements and standards. The minimum mandatory requirements for the design and construction of an indoor metal-enclosed low-voltage switchgear assembly are provided in Work Aid 1. Figure 1 shows a Westinghouse-Type DS low-voltage switchgear section. The basic construction of distribution switchgear is a stationary enclosure that contains buses, circuit breakers, and control equipment. The stationary stationary part part of low-voltage switchgear switchgear must must be a ventilated ventilated and verminproof NEMA Type 1 enclosure. To reduce future facility modification costs, the enclosure must permit future extension at each end unless specified otherwise. For example, additional switchgear can be connected to the main buswork and the ground bus that are shown in Figure 1. The stationary structure structure will have the required number of compartments to house removable air or vacuum circuit breakers. Each circuit breaker must be provided with a breaker cover (safety barrier) and latch that closes the compartment completely whether the breaker is racked in or removed. Meters for system monitoring must also be provided along with the associated indicating lights and selector switches. Each switchgear segment and circuit breaker compartment must have a nameplate that describes the associated electrical design parameters.


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Figure 1: Westinghouse Type DS Low-Voltage Switchgear Section

Metal-enclosed low-voltage switchgear assemblies must be furnished from the manufacturer with three-phase three-ph ase main and feeder buses, neutral bus (if specified), and ground bus. The incoming power supply (with an associated isolation isolation breaker) is connected to a three-phase three-phase main bus and a neutral bus (if specified). The incoming power supply is sometimes sometimes called the "incomer." The main bus supplies power to a feeder bus (and associated feeder breakers) that feeds multiple lowvoltage loads. Some switchgear may have multiple power supplies, in which case, the two power supplies are joined by a "tie" bus (and an associated tie breaker) that can connect the two power supplies. Each incoming or tie power circuit breaker must be located in a separate section of the switchgear.


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To facilitate future system expansion and to minimize expansion modification costs, spare switchgear compartments must be provided. The following following unused compartments should be provided at the end of each metal-enclosed metal-enclosed low-voltage switchgear switchgear assembly assembly and as specified specified in the Engineering Drawings: •

SPARE

A completely developed compartment (including a power circuit breaker, protective protective relays, control switches, switches, and indicating indicating lights) that is ready for operation when the feeder and control cables are connected to a load.

•

SPACE SPACE

A compa compart rtmen mentt that that is is devel develope oped d simi similar larly ly to to the the SPARE SPARE compar compartm tment ent but without an installed power circuit breaker.

•

FUTURE FUTURE A compartm compartment ent that that is develope developed d with statio stationary nary elemen elements ts such such as primary primary studs, current transformers, safety shutters, sliding rail, rail guides, levering mechanism, safety interlocks, secondary disconnects, and circuit breaker control devices and wiring.

For installation and maintenance, a circuit breaker lifting device and manual circuit breaker racking lever or ratchet handle must be provided with each switchgear assembly. assembly. Device nameplates are also required for the identification of each breaker and auxiliary unit. These nameplates indicate the circuit number and the load that is served or the equipment that is contained within the auxiliary cubicle (if present). To alert employees to the danger of electric shock during operations or maintenance, warning nameplates must be provided on each compartment door or auxiliary cubicle. Data sheets are used to supply specific switchgear information to the manufacturer (when the switchgear is ordered) and to Saudi Aramco (when the the switchgear is delivered). delivered). The data sheets should contain information about the size, type, ratings, and control of the low-voltage switchgear switchgear and the circuit breakers that are to be installed in the switchgear. The data sheets are provided in Work Aid 1. Quality control, quality assurance, and test data should also be provided with the switchgear by the manufacturer.


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Circuit Breakers

Low-voltage power circuit breakers provide low-voltage system and load isolation during normal operation and maintenance maintenance evolutions. evolutions. Low-voltage power power circuit circuit breakers also provide provide automatic system fault isolation to prevent damage to connected equipment during overload, abnormal, or fault fault conditions. Low-voltage power circuit breakers breakers that are used in Saudi Aramco installations are designed, rated, manufactured, and tested in accordance with the latest issue or revision of the cognizant sections sections of ANSI/IEEE Standard C37. Each component of a low-voltage power circuit breaker must be fully capable of interrupting the available system short-circuit current that is indicated in the system engineering drawings. Each low-voltage circuit breaker must have a three-phase short circuit current rating that is equal to, or larger than, the rating of the switchgear assembly. The low-voltage circuit breakers that are used in Saudi Aramco installations should be the dead-front, removable, removable, drawout, air type. Insulated case or molded case circuit circuit breakers must not be used in the place of power circuit breakers in low-voltage low-voltage switchgear switchgear installations installations.. Saudi Aramco uses the General Electric (GE) AK-type, the Westinghouse DS-type, and the ABB KDtype low-voltage circuit breakers in switchgear installations. The minimum mandatory requirements for the design and construction of a low-voltage circuit breaker are provided in Work Aid 1. Generally, Generally, low-voltage low-voltage power circuit breaker contacts c ontacts are operated by a stored-energy mechanis mechanism m in the form of springs; however, some low-voltage feeder breakers use manual operators. Electrical operation of a low-voltage circuit breaker is used when the breaker is controlled remotely, and manual operation is used when the breaker is controlled locally. Main breakers (e.g., (e.g ., incomer) are usually electrically-operated. electrically-opera ted. Feeder breakers are manually operated. In electrically-operated breakers, the springs are electrically controlled through use of a charging motor that maintains the closing springs in a charged state. The closing springs must develop sufficient energy to close and latch the circuit breaker. Figure 2 shows an example GE AKR, manually-operated, low-voltage circuit breaker. The breaker is closed by first turning the manual operation handle up to four strokes to charge the closing springs. Once the charging springs are charged, the breaker is closed by operation of the close push-button. Some manually-operated low-voltage circuit breakers close on the final stroke of the manual operation handle, and they do not have a close push-button. Some electricallyoperated low-voltage circuit breakers do not have a manual operation handle.


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Figure 2 shows one set of breaker contacts with the arc chute assembly assembly removed. When the breaker closes, the moving contacts close against the stationary contacts. To trip the breaker, a trip push-button is operated. Low-voltage breakers use a shunt coil trip trip (or undervoltage release) release) device for remote trip trip operations. The low-voltage breaker also uses a solid-state, solid-state, direct-acting, direct-acting, self-powered self-powered trip device. The trip device current trip levels are are set at the breaker, and a portable test instrument instrument can be used to test each trip trip device setting. The nameplate contains low-voltage low-voltage circuit breaker manufacturer, type, and rating information.

Figure 2: GE AKR Manual Low-Voltage Circuit Circuit Breaker


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Low-voltage circuit breakers that are electrically operated must be equipped with the following: •

Motor-operated, Motor-op erated, stored-energy (e.g., springs) operating operating mechanism.

•

Shunt trip coil (or undervoltage release) tripping mechanism.

•

Trip push-button.

•

Close push-button.

•

Manual closing spring charge operation handle.

•

Control devices (as indicated on Engineering drawings).

Figure 3 shows a closeup view of the low-voltage breaker contact structure for one phase of the breaker with the arc chute assembly assembly removed. The movable contact contact arm opens and closes to make contact between the movable contacts and the stationary stationary contact. When the breaker is closed, closed, the main contacts and the arcing contacts are held against the movable contact via pressure from the contact springs on the the contact pivot point. As the breaker opens, the the main contacts open first, first, which is followed followed by the arcing contacts. Because the arc interrupting interrupting contacts open last, last, the arc that is formed when the breaker opens is forced up the arc runner. The number of main and arcing contacts will vary based on the interrupting capability of the breaker. The arcing contacts are easily differentiated from the main contacts because the arcing contacts angle out slightly more than the main contacts.

Figure 3: GE AKR Low-Voltage Circuit Breaker Contact Structure Saudi Aramco DeskTop Standards

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The removable metal frame that surrounds the low-voltage circuit breaker consists of the necessary circuit breaker bus disconnecting contacts, wheels, and interlocks for drawout application. The removable metal circuit breaker frame frame allows the circuit breaker compartment door to be closed with the circuit breaker in the following four operational positions: connected, test, disconnect, and fully withdrawn (e.g., removed). When a power circuit breaker is padlocked, the breaker must not be able to be closed or moved to any other position. Electrically- or manually-operated low-voltage circuit breakers use auxiliary devices. Auxiliary devices are used for specific circuit breaker and electric power distribution system protection and control. An example of a circuit breaker auxiliary device is a position indicator. The position indicator is mechanically connected to the circuit breaker operating mechanism. An auxiliary contact is also an auxiliary device. Auxiliary contacts consist of "a" (normally open) contacts and "b" (normally closed) contacts. Normally open "a" contacts follow the position of the circuit breaker (i.e., when the circuit breaker contacts are closed, the "a" contacts are closed). Normally closed "b" contacts function the opposite to the position of the circuit breaker (i.e., when the circuit breaker contacts are closed, the "b" contacts on the auxiliary switch are open). Auxiliary contacts are used predominantly in electrical distribution protective relaying and breaker control systems. An example of an auxiliary contact use is a breaker "a" contact that is in series with the breaker trip coil. The "a" contact is only closed when the breaker is closed. The breaker "a" contact prevents the trip coil from being energized unless the breaker is closed. Extra auxiliary contacts must be provided by the manufacturer manufacture r for Saudi Aramco use. The extra auxiliary contacts are in addition to those contacts that are required for circuit breaker operation operation and indication. An alarm switch must also be provided for remote indication of an automatic trip by a protective device.


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EVALUATING LOW-VOLTAGE SWITCHGEAR AND CIRCUIT BREAKERS UPON RECEIPT

The installation of low-voltage switchgear and circuit breakers is a process that occurs over a period of time. The installation installation begins with an identified identified need for a new low-voltage low-voltage power distribution installation (e.g., a new facility). Power is necessary for the new facility to function, function, so a switchgear and circuit breaker installation is designed. After the design is approved, the switchgear and circuit breakers breakers are ordered. ordered. Once the switchgear switchgear and circuit circuit breakers are received from the manufacturer, they must be evaluated to ensure that they are proper for the installation. The purpose of the evaluation is to verify that correct low-voltage switchgear and circuit breakers were received from the manufacturer and that the proper installation specifications and parameters were met. This section will describe how low-voltage switchgear and circuit breakers are evaluated upon receipt. Visual Inspection

When low-voltage switchgear and circuit breakers are received from the manufacturer, a visual inspection should be performed. The purpose of the visual inspection is to verify that the switchgear and circuit breakers that were received from the manufacturer are in good physical condition and that all of the the requested parts and accessories accessories are present. present. Because of the damage that can occur to the moving parts that are associated with low-voltage switchgear and circuit breakers during during installation, installation, only a cursory inspection inspection is performed performed at the receiving receiving point. During the cursory inspection, the inspection personnel look for obvious equipment damage and determine whether all necessary support equipment (e.g., racking lever, and technical manuals) are present. A detailed inspection of the low-voltage switchgear and circuit breakers is performed when they are completely installed at the site or facility. Verification Against Specifications

When a new facility or facility modification is at the equipment installation stage, the design of the installation has already been completed. The type of low-voltage switchgear and circuit breakers that are selected for a specific power system should be shown in the drawings, prints, or specifications for the installation. The purpose of verifying low-voltage switchgear and circuit breakers against the specifications specifications is to ensure that the equipment that is being installed installed meets Saudi Aramco and industry standards.


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Generally, the verification against specifications consists of a determination of whether the type and rating of the equipment that is to be installed matches the size and type of the equipment that is required for the installation. In some cases, this determination is accomplished by reading an electrical plan that identifies the low-voltage switchgear and circuit breaker sizes and types. The Engineer inspects the manufacturer's manufacturer's nameplate data on each switchgear compartment and circuit breaker, and he compares them to the requirements on the electrical plan to determine whether the correct equipment is being used. In other situations, the Electrical Engineer must rely on his knowledge of the correct application of switchgear and circuit breakers sizes and types to determine whether the the correct equipment is being used. The data sheets that were used to order the switchgear from from the manufacturer should also be consulted. Example switchgear data sheets are provided in in Work Aid 1. Any quality control, control, quality quality assurance, and test data that that are provided with the low-voltage switchgear switchgear and circuit breakers should also be reviewed. A switchgear and circuit breaker applications checklist is provided in Work Aid 1. The checklist itemizes what should be included in the verification of low-voltage switchgear and circuit breakers against specifications. Low-Voltage Switchgear Nameplate

All low-voltage switchgear that is used in Saudi Aramco power systems should have a nameplate that is clearly visible on the front of the switchgear. The nameplate should contain manufacturermanufac turertype information. The information that describes the type of switchgear should consist of the manufacturer's name, the type designation, and the serial number. Because switchgear may contain different assemblies at various voltages, nameplates should be present at each switchgear segment. In accordance with ANSI C37, the manufacturer and rating information that should appear on the low-voltage switchgear nameplate should contain the following ratings: •

Rated frequency

•

Rated maximum voltage

•

Rated insulation level

•

Rated continuous current

•

Rated short-time current

•

Rated short-circuit current

Low-voltage switchgear and electric power distribution systems are designed to operate at a specific frequency. Saudi Aramco electrical distribution systems are designed to operate at 60 Hz.


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Low-voltage switchgear is designed for and should be marked with the maximum voltage at which the the switchgear can be applied. The rated maximum voltage levels of a low-voltage switchgear is the highest rms voltage for which the switchgear is designed, and the rated macimum voltage is the upper limit for operation. The rated maximum voltage levels of lowvoltage switchgear switchgear are 635 V, 508 V, or 254 V. The rated insulation insulation level of low-voltage low-voltage switchgear at each maximum voltage rating is equal to the low-frequency one-minute withstand voltage of 2.2 kV. Low-voltage switchgear is designed for and should be marked with the continuous current that the switchgear is capable of carrying and the fault current values that the switchgear is capable of interrupting without damage to the switchgear. switchgear. Specific current ratings for low-voltage low-voltage switchgear are as follows: •

Rated Continuous Current at 60 Hz. The rated continuous continuous current at 60 Hz is the amount of current that can be continuously carried by the switchgear primary circuit components (e.g., buses, bus connections) without exceeding switchgear equipment allowable temperature rise. rise. Examples of switchgear equipment are primary or secondary secondary circuit circuit components, components, insulation, insulation, and switchgear structural structural components.

•

short-time current is the designated designated The Rated Short-Time Current. The rated short-time limit of available current at which the switchgear must interrupt the current within the required time at the rated maximum voltage. The required time is termed the "rated short-time duty" and corresponds to two p eriods of one-half second current flow that are separated by a 15-second interval of zero current.

•

The Rated Short-Circuit Current. The rated short circuit current of low-voltage switchgear is the designated limit of available current at the rated maximum voltage that the switchgear must be required to withstand for a period of no less than four cycles (on a 60 Hz basis).

Circuit Breaker Nameplate

All circuit breakers that are used in Saudi Aramco power systems should have a nameplate that is clearly visible on the front of the breaker. The nameplate should contain circuit breaker manufacturer-type manufacturer-typ e information. The information that describes the type of circuit breaker should contain the manufacturer name, the type designation, and the serial number.


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In accordance with ANSI C37, the manufacturer and rating information that should appear on the circuit breaker nameplate should contain the following rating information: •

Rated frequency

•

Rated maximum voltage

•

Rated continuous current

•

Rated short-circuit current at the rated maximum voltage

•

Rated short-circuit current

Circuit breakers and electric power distribution systems are designed to operate at a specific frequency. Saudi Aramco electrical distribution systems are designed to operate at 60 Hz. Low-voltage circuit breakers are designed for and should be marked with the maximum voltage at which they can be applied. The rated maximum voltage of a low-voltage circuit breaker is the highest rms voltage (three-phase or single-phase) at which the circuit breaker is designed to perform. A low-voltage low-voltage circuit breaker is generally rated at 635 V (600 V for a fused circuit breaker), 508 V, or 254 V. Circuit breakers are designed for and should be marked with the continuous current that the breaker is capable of carrying and the short-circuit fault current values that the breaker is capable of interrupting interrupting without damage to the the breaker. Specific current current ratings for low-voltage low-voltage circuit circuit breakers are as follows: follows: •

Rated Continuous Current at 60 Hz. The rated continuous continuous current at 60 Hz is the amount of current that the low-voltage circuit breaker can continuously carry without exceeding the allowable temperature rise.

•

short circuit current is the designed The Rated Short-Time Current. The rated short limit of available (prospective) rms current at which the circuit breaker will be required to perform its short-time duty cycle at the rated maximum voltage. The short-time duty cycle is defined by ANSI 37.13 as two periods of 1/2 second current flow, which is followed by a 15-second interval of zero current. Unfused low-voltage circuit breakers do not have a rated short-time current.

•

The Rated Short-Circuit Current at Each Rated Maximum Voltage (Interrupting Rating). The rated short circuit current of an unfused low-voltage low-voltage circuit breaker is the designated limit of available current at which the circuit breaker must interrupt interrupt the current current within the required required time at the rated maximum maximum voltage.


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EVALUATING LOW-VOLTAGE SWITCHGEAR AND CIRCUIT BREAKER INSTALLATION AND TESTING

The process of determining whether low-voltage switchgear and circuit breakers should be commissioned is to verify that all the electrical inspections and tests have been properly performed and to verify that the test results are within the specifications that are designated by the applicable Saudi Aramco and industry standards. Installation inspections are performed to verify that proper switchgear and circuit breaker installation materials are used, that installation specifications and parameters are met, and that proper installation installation procedures are followed. The installation installation inspection is conducted to ensure that the switchgear and associated circuit breakers will properly function once they are installed. Electrical tests are performed to check the ability of switchgear and the associated circuit breakers to function under a variety of operating conditions and loads. Installation tests should detect shipping or installation damage, gross manufacturing defects, or errors in workmanship or installation. The Saudi Aramco Switchgear-General Pre-Commissioning Form (P-023) and the Saudi Aramco Low-Voltage Circuit Breaker Pre-Commissioning Form (P-008) contain guidance on the items that should be inspected, checked, and tested during the commissioning of switchgear and low-voltage circuit breakers. The switchgear-general and low-voltage circuit breaker pre-commis pre-commissioning sioning forms forms are provided provided in Work Work Aid 2. The proper evaluation of inspection and testing data during the commissioning process can maximize the operating time of equipment installations through a determination of trends toward failure. Failure prediction can drastically reduce equipment down-time; if a failure is predicted, operational changes can be made, maintenance can be performed, or equipment that is failing can be replaced in a controlled controlled manner. If a problem is corrected before it causes damage, operating costs will be lower because a malfunction can cause associated (or nearby) equipment damage and disruption of service, or the problem can activate emergency repair crews. A failure in any one of the many inspections, checks, or tests that are performed on a low-voltage switchgear and circuit breakers during the installation installation and testing evaluation evaluation is sufficient to prevent the equipment from being commis commissione sioned. d. Visual Inspection

Visual inspections are used to assess the physical condition of switchgear and the associated circuit breakers. A visual inspection is a pass/fail verification about a particular aspect of the physical condition or the operation of equipment. Because the criteria that are established established to determine the acceptability of the visual inspections can be subjective, the visual inspections should be performed by an experienced Electrical Engineer.


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Because of the large number of inspection items that are associated with low-voltage switchgear and circuit breakers, there are several courses of action for visual inspection failure. The course of action to be taken depends on the part of the equipment equipment that failed the the visual inspection. inspection. A failure of alignment, mechanism/linkage, lubrication, or cleanliness inspection can usually be corrected through maintenance procedures. A physical damage or suitability inspection failure will probably require the replacement of the damaged component. The visual inspection of circuit breakers should be performed during the normal breaker maintenance cycle as determined by Saudi Aramco procedures or once every 2,000 circuit breaker operations if the circuit breaker short-circuit interrupting rating does not exceed 29 kA in accordance with ANSI C37.06. Technical data to evaluate the results results of the visual inspection inspection can be found in the switchgear switchgear and circuit breaker manufacturer's manufacturer's technical manual. The following following visual inspections are used to assess the condition of low-voltage switchgear and the associated circuit breakers in Saudi Aramco systems: •

Suitability

•

Physical Damage

•

Alignment

•

Cleanliness

•

Arc Chute Assembly

•

Contacts

•

Mechanism/Linkage

•

Lubrication

Suitability

The purpose of the visual inspection for suitability is to determine whether the switchgear and associated circuit breakers are appropriate for the application in which they are placed. Under normal circumstances, the suitability of the equipment should be determined before it is placed into the system; however, a visual inspection should be performed to ensure that changes that may have been made to the system have not exceeded the ratings of the switchgear or the associated circuit breakers. To determine the suitability of switchgear and the associated circuit breakers, a visual inspection of the nameplate data should be performed and compared to the electrical system single line diagram. For example, if the nameplate information on a circuit breaker does not match the ratings of the electrical system, the circuit breaker should be replaced with a circuit breaker that is correctly rated.


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Physical Damage

Physical damage to switchgear or to circuit breakers that are contained in switchgear can prevent electric power distribution or can lead to switchgear or circuit breaker failure during critical system operations. operations. The magnitude of the electric electric energy that passes passes through switchgear switchgear and the large forces that are required to open and close circuit breakers can propagate and amplify any minor installation installation damage. Damage to switchgear and circuit breakers can lead to catastrophic catastroph ic equipment failure, fire, fire, personal injury, or death. Any physical damage to switchgear or circuit breakers that is noted requires the immediate replacement of the damaged component. The most obvious and common forms of physical damage are cracks, dents, missing or broken pieces, bent doors, and burned burned out indicator lights. The purpose of the the physical damage damage inspection is is to identify whether corrective maintenance or component replacement is necessary. Switchgear Switchgea r and circuit breakers that show any form of physical damage, no matter how small, should be determined to have failed the physical damage inspection. Alignment

The purpose of the alignment inspection is to ensure that the switchgear and circuit breaker will properly pass current when they are connected to the rest of the electrical system. Proper alignment of a circuit breaker frame when it is installed in the switchgear will ensure that the line and load buses are properly connected to the circuit breaker when the circuit breaker is racked in. Improper alignment alignment can cause uneven circuit breaker breaker heating and wear. Due to the construction construction of circuit breaker frames, circuit breakers that are out of alignment are usually visually obvious. When the circuit breaker is properly aligned, the sides of the circuit breaker will be parallel to the corresponding sides of the frame, and the proper clearance will be evident. Cleanliness

The purpose of the cleanliness visual inspection is to ensure the proper operation of the switchgear and the associated circuit breakers over the maximum operating life of the equipment. The accumulation of dirt over a period of time will impede the proper operation of the circuit breaker and will reduce the dielectric dielectric strength of the switchgear switchgear and circuit breaker insulation. insulation. Dust and dirt can also reduce the speed and sensitivity of a circuit breaker under fault conditions. The accumulation of large amounts of dust and dirt should be cleaned away from the switchgear and associated circuit breakers during maintenance cycles. Switchgear that is installed in extremely dirty, dusty, or humid areas may have to be cleaned more often than once during the maintenance cycle.


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Arc Chute Assembly

The arc chute assembly on an circuit breaker is responsible for the suppression of the arc that forms when the circuit breaker opens. The purpose of the visual inspection of the arc chute assembly is to ensure that the arc chutes can safely suppress the arc that forms when the circuit breaker opens under normal normal operating and fault fault conditions. When a visual inspection of the arc chute assembly is performed, three conditions exist that will cause the arc chute assembly to fail inspection: burn marks, scale, and cracks. Burn marks change the consistency of the the surface of an arc chute. If burn marks are present present on an arc chute, the arc chute should be replaced. Scale is the accumulation of foreign material in the arc chutes that can impede the ability of the arc chutes to extinguish an arc. Because scale should not be removed from the surface of the arc chutes, the inspector must determine whether the scale will impede the ability of the arc chute to extinguish an arc. If the inspector determines that the scale will impede the ability of the arc chute to extinguish an arc, the arc chute is replaced. Cracks may form in the arc chutes during the normal normal operation of the the circuit breaker. The inspector must must determine whether the cracks will interfere with the ability of the arc chute to extinguish an arc, and he should replace the arc chute accordingly. Contacts

The circuit breaker contacts provide a current path through the circuit breaker to interrupt the current during normal operating operating and fault conditions. conditions. Damage can occur at the breaker contacts as a result of the mechanical stress from breaker closing operations and the electrical arc that forms during breaker opening operations. The purpose of the visual inspection of circuit breaker contacts is to ensure that the circuit breaker contacts provide a low resistance current path and that the circuit breaker contacts safely interrupt current during normal operating and fault conditions. During the contact inspection, the primary bushings, porcelains, and finger finger clusters should be checked. In general, the two types of current that are interrupted by a circuit breaker are low circuit current and high circuit current. The arc that is associated with a low circuit current interruption will take longer to extinguish extinguish than an arc that is associated associated with a high circuit circuit current interruption. interruption. Low circuit current interruptions will leave small burn and pock marks on the surface of the contacts. These small burn and pock marks will not interfere with the operation of the contacts, but the contacts will need to be replaced when they erode over time to some wear point that is defined by the manufacturer. Contacts that interrupt high circuit current will have burn marks and roughened edges that will affect the amount of contact surface that actually touches when the circuit breaker's contacts are closed. As was the case with with the other type of contact contact wear, if the contacts contacts become too thin, as defined by the circuit breaker's manufacturer, then the contacts should be replaced.


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Mechanism/Linkage

The mechanism/linkage assembly of a circuit breaker performs the actual movement of the contacts when the breaker opens or closes. The purpose of the mechanism/linkage inspection is to ensure that the mechanism/linkage can move freely. Free movement of the the mechanism/linkage will ensure that the circuit breaker can properly and rapidly operate the circuit breaker contacts. The inspector should visually determine that no obstructions exist that will impede the movement of the mechanism/linkage. This inspection will will also ensure that when the open/close operation test is performed, no circuit breaker damage can occur. Lubrication

The lubrication visual inspection should be performed in conjunction with the mechanism/linkage visual inspection. The purpose of the lubrication visual inspection is to ensure that the circuit breaker mechanisms, mechanisms, the moving parts, the bearing points, points, and the sliding mechanics are properly properly lubricated and free of rust. Before the application of new lubrication can take place, hardened grease, dirt, and rust should be removed from the surfaces that require lubrication. A cloth that is dampened with kerosene should be used to remove remove the hardened grease and dirt. Care must be taken taken to ensure that the the cloth does not deposit fibers on the moving parts of the circuit breaker. The deposit of cloth fibers on the moving parts of the circuit breaker can cause subsequent improper breaker mechanism operation. After the proper preparation preparation of the moving parts of the circuit breaker, a thin layer of lubrication should be applied. Excess lubrication should be wiped off with a clean cloth. Mechanical Inspection

A mechanical inspection is used to assess the ability of switchgear and the enclosed circuit breakers to physically physically perform the mechanical mechanical movements that that are necessary for proper operation. operation. Tests are also performed during the mechanical inspection to assess switchgear and circuit breaker safety functions. Because of the large number of mechanical inspection items that are associated with low-voltage switchgear and circuit breakers, there are several courses of action for mechanical inspection failure. The course of action depends on the part of the equipment that failed the inspection. A failure of mechanism operation can usually be corrected through maintenance procedures. procedures. For example, a bolt torque torque test failure can be corrected through adjustment of the bolts with a torque wrench.


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The general mechanical inspections and tests that are performed on switchgear and circuit breakers that that are installed installed in Saudi Aramco Aramco systems systems are as follows: follows: •

Bolt Torque

•

Door Operation

•

Rack in - Rack Out

•

Open/close Operation

Bolt Torque

The purpose of a bolt torque inspection is to ensure that enough force is present to hold the buswork and circuit circuit breaker frames in in place during circuit breaker breaker operations and and fault conditions. conditions. To determine the amount of force that exists between a bolt and a circuit breaker, a torque wrench is applied to the bolt in the direction that will tighten the bolt, and the amount of torque is read. Torque values for switchgear are listed in the switchgear technical manuals, and torque values for low-voltage circuit breakers are listed in the Saudi Aramco Low-Voltage Circuit Breaker Pre-Commissioning form that is provided in Work Aid 2. The manufacturer of the circuit breaker will will also provide provide a list list of acceptable acceptable torques in in the circuit breaker breaker technical technical manual. Door Operation

Each switchgear circuit breaker compartment must be provided with a door (safety barrier). The door should also contain an interlock that prevents the closure of the door unless the circuit breaker is racked in or completely completely removed. During the mechanical inspection, each switchgear compartment door operating mechanism (e.g., handles and locking bars) should be mechanically operated during the mechanical inspection, and the door interlocks should be tested. Rack In - Rack Out

When a breaker is racked into the switchgear, the line and load sides of the breaker contacts are connected to the electrical electrical system. Additional control control power connections are are made to enable the circuit breaker to be remotely remotely controlled and automatically automatically operated. The purpose of a rack in rack out inspection is to ensure that the circuit breaker moves in and out of the switchgear freely and that all connections and safety interlocks function correctly.


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Circuit breakers generally have a test position to allow the operation of the breaker when it is at the switchgear but but is not connected to to the electrical system. The circuit breaker breaker test position position varies from manufacturer to manufacturer. Generally, as a circuit breaker is pushed into its switchgear cell and the guides of the circuit breaker lock into place, the circuit breaker should be in the test position. In the test position, the circuit breaker breaker protrudes from the switchgear so that the breaker operation operation can be observed. In the test position, the primary primary contacts of the circuit breaker are not connected to the system, but the control circuitry of the circuit breaker can be energized. In the test position, the circuit circuit breaker can be cycled without affecting the rest rest of the electrical distribution system. While the circuit breaker is in transit between the test and the fully inserted position, the breaker should not have control power, and it should not operate. Interlocks can be provided in low-voltage low-voltage circuit breakers. breakers. Interlocks are designed designed to prevent the unsafe operation of the circuit breaker. A typical interlock that is provided on most circuit breakers is the rack in - rack out interlock. To prevent racking in or racking out a closed breaker, circuit breakers are equipped with a rack-out interlock that trips a closed breaker when it is moved from the fully inserted or test positions. A problem arises when a breaker has been closed in the test position and the breaker is subsequently racked all the way to the fully inserted position. If the breaker is closed, the busbar connections connections will complete complete the electric circuit as soon as the busbar connections come in contact with the switchgear busbars. When a breaker is racked into switchgear in the closed position, dangerous arcing and uncontrolled equipment startups could occur. Conversely, if a closed breaker that is in the fully inserted position is racked out, the current interruption would take place at the busbar connections instead of the breaker main contacts. Because there is no arc-suppression arc-suppression mechanism mechanism at the busbar connectors, dangerous arcing could occur. The rack-out interlock is designed to prevent dangerous arcing at the switchgear busbar connections. Generally, the mechanical inspections and tests that are performed on a circuit breaker follow a logical progression. To perform the mechanical inspections and tests, the breaker is first racked to the test position. position. In the test position, position, the circuit breaker is cycled and the breaker operation operation is observed. The breaker is left in the closed position, and the breaker is racked towards the fully inserted position. When the breaker leaves the test position, the breaker should trip. After the breaker trips (from the rack-out interlock), the breaker is returned to the test position and cycled a final time. During the racking operations, mechanical condition of all auxiliary devices, bumpers, position position indicators, latching, latching, tripping, and operating mechanisms mechanisms are checked for proper operation. Open/Close Operation

Some circuit breakers in Saudi Aramco electrical systems can go from maintenance cycle to maintenance cycle without performing a single circuit interruption. A circuit breaker must always be in a condition to operate no matter how infrequently infrequently the circuit breaker has been used. The purpose of the open/close operation test is to ensure that the circuit breaker opens and closes properly. Saudi Aramco DeskTop Standards

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To perform the open/close operation test, the circuit breaker is racked to the test position. In the test position, position, the circuit breaker breaker is cycled, and the breaker operation is observed. observed. The breaker control power is then disconnected (or bypassed), and the breaker is manually closed and tripped. During the opening and closing operations, the mechanical condition of all auxiliary devices, bumpers, position position indicators, latching, latching, tripping, and operating mechanisms mechanisms are checked for proper operation. The moving contact travel travel for the circuit circuit breaker is measured measured and recorded. The manufacturer's technical manual should contain information on the minimum moving contact travel distances. Electrical Inspection

During the commissioning process, electrical inspections and tests are performed to check the ability of the switchgear and circuit breakers to operate for a reasonable future period of time under a variety of operating conditions and loads. Acceptance or installation tests will usually detect shipping or installation damage and gross defects or errors in workmanship in equipment construction. Once the installation and inspection data have been recorded and assembled, a methodical and consistent program of periodic data collection and evaluation should be established. As each new maintenance item, test, splice, system addition, or system reconfiguration occurs, new inspections and data records will be required and should be added to the existing data on file. Because an electrical inspection or test failure can be caused by a construction error, equipment age, or operational misuse, some kind of troubleshooting or maintenance activity should be performed on the faulty equipment. For example, a contact resistance resistance test failure can be rectified rectified by cleaning the contacts to remove carbon build-up or by replacing the contacts. Some electrical inspection or test failures are not repairable, and they will require the replacement of the equipment before low-voltage switchgear and circuit breakers can be commissioned. For example, an insulation resistance test failure usually indicates a gross imperfection in the circuit breaker insulation. insulation. The following electrical inspections, checks, and tests are performed on Saudi Aramco lowvoltage switchgear and circuit breakers: •

Insulation Resistance

•

Contact Resistance

•

Functional Operation

•

Auxiliary Equipment


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Insulation Resistance

The purpose of the insulation resistance test is to directly measure the switchgear and circuit breaker insulation insulation resistance resistance through use of a megger. In the insulation insulation resistance test, the megger is used to set up an electromagnetic field, and the field that is created is used to produce leakage currents that will flow between the breaker phase and ground, or from phase to phase, through the insulation. insulation. The amount of leakage current current flow that is detected detected through use of the megger results in a megger meter readout of insulation resistance (in megohms). To conduct the insulation resistance test, the megger is connected between two conductors (phases) and the the megger is operated. Insulation resistance resistance tests should should be conducted phase-to phase and phase-to-ground phase-to-ground on all buswork, bus insulation, and on the line side and the load side of the the each installed installed circuit circuit breaker. Megohmmeter test voltages voltages should be 1000 V dc. The megger is then connected across the open contacts of one of the circuit breaker phases, and the megger is operated. Similar megger readings are taken across each remaining phase contact pair for every circuit breaker that is installed in the switchgear. The insulation resistance values are recorded on a test data sheet or in the appropriate Saudi Saud i Aramco pre-commiss pre-commissioning ioning form. form. The Electrical Engineer should evaluate the insulation resistance (megger) test values to ensure that the insulation resistance values that were recorded are greater than the manufacturer's minimum value. If the manufacturer's minimum minimum value is not provided, the value of the the insulation resistance should should be greater than the rated rated voltage + 1 kV in megohms. megohms. For example, a 600 V rated system should have a measured insulation resistance that is greater than 1.6 megohms. Any value of insulation resistance that is less than the minimum specifications should be investigated by the Electrical Engineer who performs the test data evaluation. The ratio of two time-resistance readings (such as a 60-second reading that is divided by a 30second reading) is called a dielectric absorption ratio. The dielectric absorption ratio is useful in recording information about the insulation. If the ratio is a ten-minute reading that is divided by a one-minute reading, the value is called the polarization index. Because constant cranking is required for hand-cranked megger instruments, it is easier to run the test for only 60 seconds and take the first reading reading at 30 seconds. When a power-operated megger instrument is used, the results of running the test for a full ten minutes and taking readings at one and ten minutes will give the polarization index. An explanation of the evaluation of the dielectric absorption ratio is provided in Work Aid 2. In accordance with the International Electrical Testing Association (NETA), all of the acceptable insulation resistance values should be determined through consultation with the appropriate switchgear or circuit breaker manufacturer technical manual. The insulation resistance test should only be performed during the commissioning of the low-voltage switchgear and circuit breakers and during the first few maintenance cycles.


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Contact Resistance

The purpose of the circuit breaker contact resistance test is to identify contacts that are defective or detrimental to the operation operation of the circuit circuit breaker. The contact resistance resistance test may also identify loose connections connections in a circuit breaker. To conduct the contact resistance resistance test, the circuit breaker must be withdrawn withdrawn from its compartment. compartment. With the circuit breaker in the closed position, position, the leads of a digital, low-resistance ohmmeter should be placed across the line and load sides of the circuit breaker, and measurements should be taken. A digital, low-resistance ohmmeter can deliver enough power to the circuit breaker to make accurate readings that have more validity than readings that can be obtained obtained through the use of an ordinary multimeter. multimeter. The contact resistance is recorded on a test data sheet or in the Saudi Aramco Low-Voltage Circuit Breaker Pre-Commissioning form, P-008. Increased contact resistance may be caused by contacts that do not make proper contact or by pitting on the surface of the contacts. The contact resistance values that are recorded should be consistent with manufacturer recommended values. Generally, values of contact resistance in excess of 200 micro-ohms and deviations of more than +/- 20% should be investigated. Technical data to evaluate the results of the contact resistance test can be found in the circuit breaker manufacturer technical manual or in the Saudi Aramco Low-Voltage Circuit Breaker PreCommissioning form, P-008. Functional Operation

The functional operation test of the low-voltage switchgear and circuit breaker is the test that ensures that all of the switchgear and circuit breaker parts are able to work in conjunction with each other so that the circuit breaker can perform perform its protective responsibiliti responsibilities. es. Most of the tests that have been performed so far have been tests that ensure the performance of the individual parts of the low-voltage switchgear or circuit breaker. The functional operation test will ensure that the parts will work together so that the switchgear operates correctly correctly when it is installed installed in an electrical system. system. To perform the functional functional operation test, test, the circuit breaker breaker must be racked into its switchgear compartment and put into the test position. In the test position, control power is connected to the circuit breaker, but the main power connections remain unconnected. Circuit breakers provide for normal circuit switching operations and provide a means for disconnecting a faulty circuit or equipment from the electric system with minimum damage and disturbance. Circuit breakers must be capable of closing, carrying, and interrupting the largest fault possible at their location.


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To test the operation of a circuit breaker trip circuit, the circuit breaker test position is used. With the circuit breaker in the test position, trip signals can be sent to the breaker via test equipment, and the proper operational response of the circuit breaker can be monitored. With the breaker contacts closed, a signal is sent to the instrument transformers that is strong enough to activate a circuit breaker trip signal. The artificial trip signal should trip the circuit breaker and open the circuit breaker contacts at the specified fault current level and within the specified amount of time. The trip test process is repeated for each of the phases of the circuit breaker to ensure that a trip signal that is initiated in any of the phases will trip the breaker. The functional operational trip test information (e.g., current level and time) is recorded on a test data sheet or in the Saudi Aramco correct pre-commissioning form. The functional operational trip test should be repeated for each device that is capable of tripping the circuit breaker (e.g., undervoltage relay, overcurrent relay, and thermal relay). Circuit breaker trip test data are recorded in the Saudi Aramco LowVoltage Circuit Breaker Pre-Commissioning Form, P-008. Auxiliary Equipment

Auxiliary equipment that is used in low-voltage switchgear includes control, indicating, and test equipment. Examples of such equipment include instrument transformers, fuses and fuse holders, relays, annunciators, annunci ators, and meters. The low-voltage switchgear switchgear and circuit breaker auxiliary equipment should be inspected, checked, and tested in accordance with the Saudi Aramco Switchgear-General Pre-Commissioning Form, P-023.


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SYSTEM PRE-OPERATIONAL CHECK-OUT PHASE REQUIREMENTS

The system pre-operational checkout phase of the commissioning cycle for low-voltage switchgear and circuit breakers provides an opportunity for Saudi Aramco personnel to perform wiring checks, subsystem component check outs, and circuit breaker interlock performance tests. Each low-voltage switchgear and circuit breaker component is checked to ensure that it works individually and as a complete system. Point-to-Point Wiring Check

Point-to-point wiring checks are performed to verify low-voltage switchgear and circuit breaker compliance with wiring diagrams and manufacturer's specifications. Terminations and terminal blocks are also checked for routing routing and labeling. During the point-to-point point-to-point wiring wiring checks, control and metering transformers and fuses are checked for proper application and type. If necessary, adjustments adjustments are made to components such as relays, annunciators, alarms, and targets. Subsystem Checkout

Subsystems are checked to ensure that electrical continuity exists for control and protective devices. The proper operation of all subsystems subsystems is tested tested through use of controlled controlled operation and check out of the controls and protective protective devices. Each subsystem is performance performance tested through through the application of full operational voltage to each subsystem through the proper protective devices. A complete operational test is is performed on equipment controls, controls, interlocks, protective protective devices, and components with each subcircuit connected to its main system. During the performance performance test, the main systems are still isolated and independent from plant systems. Before the equipment is connected to the plant system, subsystem performance testing is critical to ensure the proper and safe operation of the equipment protection and control subsystems. Interlocks

Operation tests are performed to ensure that the various switchgear and circuit breaker operational interlocks function properly. For example, if the circuit breaker has a lockout relay, the lockout relay should be tested. tested. Lockout relays are used in in circuit breaker control control circuitry to prevent a circuit breaker that has tripped due to fault conditions from closing until the lockout relay is manually reset. With the circuit breaker contacts open after a trip test, appropriate signals should be sent to the circuit breaker to close the circuit breaker. If the circuit breaker is equipped with a lockout relay, the circuit breaker should not close even though the input signal indicates that the circuit breaker can reclose. All other operational operational interlock devices on the circuit circuit breaker that prevent the closure of the circuit breaker should be tested in a similar manner.


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SYSTEM OPERATIONAL TESTING PHASE REQUIREMENTS

The operational testing phase of the commissioning cycle for low-voltage switchgear and circuit breakers provides an opportunity opportunity for Saudi Aramco personnel personnel to perform perform the following: following: •

Switchgear source feed compatibility checks

•

Complete switchgear functional test

Switchgear source feed compatibility checks are performed on low-voltage switchgear and circuit breakers through application of the full system voltage onto the switchgear with the circuit breakers installed installed and racked in. With the voltage applied, voltage phasing, synchronizing, synchronizing, device rotation, and other source feed compatibility checks are performed. Parallel or alternate power source feed operations are also performed to ensure the total operation of the major components of the low-voltage switchgear system. A complete system functional test is performed on low-voltage switchgear and circuit breakers to ensure that the entire low-voltage electric power distribution system functions in accordance with the system design. During the complete system functional functional test of low-voltage switchgear and circuit breakers, the switchgear is allowed to assume a fully loaded condition for a period of time that is adequate to obtain the maximum system temperature. After the loaded time period, the switchgear temperatures temperatures are monitored. The low-voltage low-voltage cable and busbar temperatures temperatures can be monitored locally through use of temperature monitoring equipment or through use of thermographic surveys. Temperature monitoring equipment can be temporarily installed at the switchgear vents or in the switchgear. Particular attention should be paid to wiring and terminal connections during the complete system functional test.


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WORK AID AID 1:

REFERE REFERENCE NCES S FOR EVALU EVALUATI ATING NG LOW-V LOW-VOLT OLTAGE AGE SWITC SWITCHGE HGEAR AR AND CIRCUIT BREAKERS UPON RECEIPT

Figure 7 shows a table of Saudi Aramco low-voltage power switchgear general requirements. The requirements are excerpted from documented Saudi Aramco standards and specifications (e.g., 16-SAMSS-502). General Requirement mentss

Compartmentalized, metal-enclosed switchgear must be used. Station-type cubicle switchgear is not permitted for Saudi Aramco installations. Desi Design gn and and ins insta tall llat atio ion n of of all all swit switch chge gear ar must must be in in acco accord rdan ance ce wit with h ANSI/NFPA 70 (NEC). Short-circuit ratings of buses and current interrupting devices must not be less than 105 percent of the calculated fault current at the point of application for present and future planned conditions. The system design must use only fully-rated interrupting devices. Series-connected, series-rated series-rated or cascade breaker interrupting ratings are not allowed for Saudi Aramco installations. Switchgear and motor control centers, except for switchracks, switchracks, must must be of the indoor type, installed in an air-conditioned environment. Power circuit breaker switchgear must be used in industrial facilities and hospitals in place of switchboards. Switches, circuit breakers, motor controllers, controllers, and fuses must not be located in Division I classified areas. Transformer line and load circuit breakers must have a continuous rating that is not less than the forced-cooled rating of the transformer. transformer. The current carrying capacity of the main switchgear bus must not be less than the continuous rating of the main incoming circuit breaker. When switchgear bus-tie circuit breakers are used, they must be fully interchangeable with the switchgear main circuit breakers. Bus-tie breakers must be kept normally-open. Controls Contro ls must be provided to allow the bus-tie breaker to be closed for a short period of time with both main breakers closed to provide planned load transfers without a power outage. Short circuit ratings for switchgear with normally open bus-tie breakers must be calculated with the bus-tie breaker in the open position. Low-voltage switchgear must comply with 16-SAMSS-502. Low-voltage power circuit breakers must be of the manually operated type, except for remote tripping, motor controller and specific auto/manual transfer applications. Each breaker line-side (and each bus section in bus-tie applications) must be monitored by an unswitched voltmeter. Each switchgear main isolation breaker line-side must be monitored by an unswitched ammeter. Figure 7: Saudi Aramco Low-Voltage Power Switchgear Requirements (From 16-SAMSS-502)


26



Figure 8 shows the data sheet that is used by Saudi Aramco to supply low-voltage switchgear information to the manufacturer (Vendor)

Figure 8: Low-Voltage Switchgear Buyer Data Sheet


27



WORK AID 1 (Cont'd)

Figure 8: Low-Voltage Switchgear Buyer Data Sheet (Cont'd)


28



Figure 9 shows the data sheet that is used by the manufacturer (Vendor) to supply low-voltage switchgear information to Saudi Aramco

Figure 9: Low-Voltage Switchgear Vendor Data Sheet


29



Figure 10 shows a table of rating, design, construction, and auxiliary device information for lowvoltage power circuit breaker installations.

Rat Rating ing

LowLow-vo volt ltag agee powe powerr circ circui uitt brea breake kers rs must must be desi design gned ed,, rate rated, d, manu manufa fact ctur ured ed,, and tested in accordance with the latest issue or revision of the following: ANSI/IEEE Standard C37.13 ANSI/IEEE Standard C37.16 ANSI/IEEE Standard C37.17 ANSI/IEEE Standard C37.50 Each unit of the low-voltage power circuit breaker must be able to interrupt the available short-circuit current that is indicated in Engineering Drawings. LowLow-vo volt ltag agee cir circu cuit it brea breake kers rs must must be the the air air circ circui uitt bre break aker er type type.. Oi Oil cir circu cuiit breakers and oil-im oil-immers mersed ed contactors are not permitted for Saudi Aramco installations. Stationary mounted type power circuit breakers, fused circuit breakers, series-connected, series-connected, series-rated or cascade rated circuit breakers must not be used. Low-voltage circuit breakers should be the dead-front, removable, drawout type. Insulated case or molded case circuit breakers must not be used in the place of power circuit breakers. Low-vol Low-voltag tagee power power circui circuitt breaker breaker conta contacts cts must must be be operate operated d by a stored-energy store d-energy mechanism in the form of springs. The springs must be electrically controlled and must develop sufficient energy to close and latch the circuit breaker. Low-voltage circuit breakers that are electrically operated must be equipped with the following: Motor-operated, Motor-op erated, stored-energy operating operating mechanism. mechanism. Shunt trip coil tripping mechanism. Trip push-button. Close push-button. Manual closing spring charging handle. Control devices (per the Engineering drawings). The removable element in the metal frame configuration must consist of a power circuit breaker equipped equipped with the necessary necessary disconnecting contacts, contacts, wheels, and interlocks for drawout application. • • • •

Des Design ign

Constr Construct uction ion

• • • • • •

Figure 10: Low-Voltage Power Circuit Breaker Rating, Rating, Design, Construction, and Auxiliary Device Installation Requirements


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Construction (Cont’d)

The removable element must permit closing the compartment door with the circuit breaker in the following four operational positions: connected test disconnect fully withdrawn (or removed) Each circuit breaker enclosure door must have a provision for padlocking (with up to three locks) in all three open (off) positions. When padlocked, the circuit breaker must not be able to be closed or moved to any other position. Each circuit breaker must be equipped with a position indicator that is mechanically connected to the operating mechanism. Unless specified otherwise, each circuit breaker must have a minimum of four convertible auxiliary contacts, in addition to those contacts that are required for circuit breaker operation and indication, that are available for Saudi Aramco use. An alarm switch must be provided for remote indication of an automatic trip by an overcurrent overcurrent or other protective device. The alarm switch must not be operated by other trips. A minimum of one "a" (normally open) contact and one "b" (normally closed) contact must be provided. • • • •

Auxiliary Devices

Figure 10: Low-Voltage Power Circuit Breaker Rating, Rating, Design, Construction, and Auxiliary Device Installation Requirements (Cont'd)


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Low-Voltage Switchgear and Circuit Breaker Applications Checklist

Low-voltage switchgear and circuit breaker rating information can be found on the equipment nameplate or in the manufacturer technical manual. The following is a checklist that is used to verify that the type, rating, and operational characteristics of low-voltage switchgear and circuit breakers are correct for the application application based on Saudi Aramco and industry industry standards: standards: •

Verify that the low-voltage switchgear meets the Saudi Aramco requirements that are shown in Figure 10.

•

Verify that the low-voltage switchgear matches the information sheet that is provided in the data sheet (Figure 9).

•

Verify that the following low voltage switchgear nameplate ratings are correct for the application: •

Rated Frequency

•

Rated Maximum Voltage

•

Rated Insulation Level

•

Rated Continuous Current

•

Rated Short-Time Current

•

Rated Short-Circuit Current

•

Verify that the circuit breakers do not use oil as the current interrupting medium.

•

Verify that the following low-voltage circuit breaker ratings are correct for the application: •

Rated Frequency

•

Rated Maximum Voltage

•

Rated Continuous Current

•

Rated Short-Time Current

•

Rated Short-Circuit Current at the Rated Maximum Voltage (Interrupting Rating)

•

Verify that the circuit breaker's frame is sufficiently rated for the amount of asymmetrical asymmetrical short-circuit current that the circuit can produce.

•

Verify that the circuit breaker's operational characteristics will provide adequate protection protection for the electrical equipment that is in the circuit with the circuit breaker (e.g., long-time-delay protection; short-time-delay protection; and instantaneous protection).


32



WORK AID AID 2:

REFERE REFERENCE NCES S FOR EVALU EVALUATI ATING NG LOW-V LOW-VOLT OLTAGE AGE SWITC SWITCHGE HGEAR AR AND CIRCUIT BREAKER INSTALLATION AND TESTING

NETA Checklists

The following checklist is excerpted from the International Electrical Testing Association (NETA) checklist for the inspection of switchgear - general: 1.

Insp Inspec ectt the the phys physic ical al,, ele elect ctri rica cal, l, and and mec mecha hani nica call con condi diti tion on..

2.

Compa Compare re the the equi equipme pment nt nam namepl eplat atee info inform rmat atio ion n with with the the lat lates estt sin singl glee line line dia diagr gram am and report any discrepancies.

3.

Insp Inspec ectt for for prop proper er alig alignm nmen ent, t, anch anchor orag age, e, and and grou ground ndin ing. g.

4.

Insp Inspect ect all all bus bus conne connecti ctions ons for high high resi resist stanc ancee with with a resi resist stanc ancee ohmme ohmmeter ter.. Chec Check k the tightness of the bolted bus joints through use of a calibrated torque wrench. Refer to the manufacturer's instructions for the proper foot-pound levels.

5.

Key inter interloc lock k sys system temss shou should ld be physi physical cally ly test tested ed to ensur ensuree that that they they oper operat atee properly properly as follows: follows: •

Attempt to close a locked open device.

•

Attempt to open a locked closed device.

•

Attempt to exchange keys with devices that are not in their normal operating positions.

6.

All All switch switchgea gearr door doors, s, panels panels,, and and sectio sections ns must must be be insp inspect ected ed for paint, paint, dents dents,, scratches, and proper fit.

7.

Insp Inspec ectt the the swi switc tchg hgea earr for for clea cleanl nlin ines esss and and prop proper er lubr lubric icat atio ion. n.

8.

Exercise all active components.

9.

Insp Inspec ectt all all indi indica cati ting ng dev devic ices es for for pro prope perr ope opera rati tion on..


33



The following circuit breaker test information is excerpted from the International Electrical Testing Association (NETA) checklist for the inspection of low-voltage circuit breakers: Circuit Breakers - Low Voltage (Air) Visual and Mechanical Inspection 1.

Insp Inspect ect for for phys physic ical al dam damage age,, clean cleanli lines ness, s, and and nam namepl eplat atee comp compli lianc ancee with with the the sin singl glee line diagram.

2.

Mecha Mechanic nical al operat operatio ional nal tests tests must must be made made in in acco accord rdanc ancee wit with h the the manufa manufactu cture rer' r'ss instruction manual.

3.

The The circ circui uitt brea breake kerr cell cell fit fit and and elem elemen entt alig alignm nmen entt mus mustt be che check cked ed..

4.

Check th the ti tightness of of co connections.

5.

Dashpo Dashpots ts must must be be remo removed ved,, insp inspect ected, ed, cleane cleaned, d, and refil refilled led with with pro proper per oil. oil.

6.

Make Make a ver very y clos closee insp inspec ecti tion on of of the the ope opera rati tion on of of main main and and arc arcin ing g cont contac actt of the the circuit breaker to ensure that the springs that are responsible for maintaining primary contact pressure pressure are in good condition.

Electrical Tests 1.

A con conta tact ct resis esisttance ance tes test mus mustt be be per perfform ormed. ed.

2.

An insula insulati tion on res resis istan tance ce test test must must be perfor performed med at 1,000 1,000 volt voltss dc dc for for one minute minute from pole to pole, from each pole to ground, and across the open contacts of each phase.

3.

(Optional ) The minimum pickup current of trip devices must be determined by primary primary current injection injection..

4.

The The long long time time delay delay must must be be det deter ermi mine ned d by by pri prima mary ry inje inject ction ion at 300% 300% of of the the pickup current.

5.

Shor Shortt tim timee pic pickup kup and time time dela delay y mus mustt be be det deter ermi mined ned by prim primar ary y inj injec ecti tion on of current.

6.

The inst instant antane aneous ous pickup pickup curren currentt mus mustt be be det deter ermi mined ned by prim primar ary y inj inject ection ion..


34



7.

Trip Trip unit unit rese resett cha charracte acteri rist stic icss mus mustt be be ver verif ifie ied. d.

8.

Adju Adjust stmen mentt mus mustt be be made made for for fina finall set setti ting ngss in in acco accord rdanc ancee wit with h the the engine engineer' er'ss prescribed settings. settings.

9.

Auxil Auxiliar iary y prot protect ective ive device devices, s, such such as as groun ground d fault fault or under under volt voltage age relay relays, s, mus mustt be activated to ensure operation of shunt trip devices.

10.

If the the circu circuit it brea breaker ker has a char chargin ging g motor motor,, the spri springs ngs and and other other devi devices ces that that are are associated with this charging motor must be closely inspected. The circuit breaker must be electrically operated to verify the performance of the limit switches responsible responsible for stopping and starting the charging motor.

11.

Circ Circui uitt break breaker erss with with soli solid d state state trips trips must must be test tested ed in in accor accordan dance ce wit with h manufacturer's instructions. a.

Prim Primar ary y inje inject ctio ion n is reco recomm mmen ende ded d to eva evalu luat atee comp comple lete te tri trip p circ circui uitt operations.

b.

Secondary injection injection can be used for evaluating evaluating the electronic electronic portion of the the trip unit.

Test Values 1.

Conta Contact ct resis resistan tance ce must must be determ determine ined d in in micr microo-ohm ohmss or mill milliv ivol olts ts.. Valu Values es that that deviate from adjacent poles or similar breakers by more than 50% should be investigated.

2.

Insu Insula lati tion on res resis ista tanc ncee mus mustt not not be less less the the 50 mego megohm hms. s. a.

3.

Do no not me megger so solid st state de devices.

Mini Minimu mum m pic pickup kup curre current nt,, tri trip p tim times es,, and and inst instant antane aneous ous picku pickup p val values ues must must be be adjusted to engineer settings. Test values should fall within manufacturer's published time-curren time-currentt characteristic characteristic tolerance tolerance band.


35



NETA Values for Overcurrent Overcurrent Trip Test (at 300% of Rated Continuous Current of Breaker) Tripping Time, Seconds Voltage, Volts

Range of Rated Continuous Current, Amperes Minimum

(1) 240 240 600 600 240 600 600 600 600 600 *

(2) 15-45 50-100 15-45 50-100 110-225 110-225 250-450 500-600 700-1200 1400-2500

Thermal Breakers (3) 3 5 5 5 10 10 25 25 25 25

Magnetic Breakers (4) --5 5 5 --10 10 10

Maximum Tripping Times for Cable Protection* Maximum (5) 50 70 80 150 200 200 250 250 450 600

(6) 100 200 100 200 300 300 300 350 600 750

Thes Thesee valu values es are are bas based ed on on heat heat tes testt cond conduc ucte ted d by circ circui uitt brea breake kerr manu manufa fact ctur urer erss on conductors in conduit.


36



Figure 11 shows a table of low-voltage switchgear construction general requirements.

Gene Genera rall

The The met metal al-e -enc nclo lose sed d low low-v -vol olta tage ge swi switc tchg hgea earr mus mustt be be com compl plet etel ely y fac facttory ory assembled, wired, adjusted, and tested. Switchgear design must have a ventilated and vermin proof enclosure, NEMA Type 1, and must permit future extension at each end, unless specified otherwise. It must consist of a stationary structure assembly and one or more removable air or vacuum circuit breaker units. All circuit breakers installed in the switchgear assembly (except for space heater circuit breakers) must must have the three-phase short circuit circuit current rating equal to or larger than the rating of the switchgear assembly. The overall height of the switchgear lineup must be maximum 2300 mm (90 in.).

Figure 11: Low-Voltage Switchgear Construction Construction General Requirements Requirements


37



Figure 12 shows a table of low-voltage switchgear stationary structure construction requirements. requirements.

Stationary Switchgear Structure

The stationary steel structure assembly must be a self-contained multiple unit housing having a required number of vertical sections. Each incoming or tie power circuit breaker must be in a separate vertical section. Each incoming line, tie, or 3200 A and above feeder power circuit breaker must be located in the lower portion of its vertical section. A compartment that is identified as "SPARE" must be available (including a power circuit breaker, breaker, protective protective relays, control switches, switches, indicating indicating lights, lights, etc.). The continuous current rating of the "SPARE" circuit breakers must be as specified in Engineering Drawings (Data Sheet No.1). A compartment that is designated as "SPACE" must be developed similarly to the "SPARE ," but without the installed circuit breaker. A compartment that is designated as "FUTURE" must be developed with stationary elements (e.g., primary studs, CTs, sliding rail, rail guides, levering mechanism, safety interlocks, secondary disconnects, circuit breaker control devices, and wiring). An additional compartment, within the switchgear assembly and readily available, must be provided to store engineering and installation drawings, instruction books, parts list, special tools, and spare fuses. When specified, the "SPARE", "SPACE", and "FUTURE" compartments compartments must be located at the end of each metal-enclosed switchgear assembly and as specified in the Engineering Drawings. The rear sections of all vertical sections must be developed as separate spaces for main and incoming buses or cables and for outgoing power cables and power cable terminations. terminations. All switchgear compartments must be separated by grounded steel panels-barri panels-barriers ers with with a nominal thickness thickness that that is not less less than 3 mm (MSG (MSG No.11 or 0.1196 0.119 6 in.). Other barriers, blank steel panels, and formed steel doors must be made of sheet metal with minimum thickness of 1.9 mm (MSG No.14 or 0.0747 in.).

Figure 12: Low-Voltage Switchgear Stationary Structure Requirements


38



Figure 13 shows a table of low-voltage switchgear bus construction requirements. Buses (General)

Power Power Bus Bus

Neutral and Ground Buses

Metal-enclosed low-voltage switchgear assemblies must be furnished complete with three-phase main and feeder buses, neutral bus (if specified), and ground bus. Switchgear buses (power, neutral and ground) must be constructed of electrical grade copper flat bar material having 98 % conductivity and mounted (except the ground bus) on glass-reinforced glass-reinforced high strength polyester polyester insulators. All buses must be designed for future extensions. Future extensions must not disturb any equipment or wiring. Power Power bus phase phase arrang arrangeme ement nt must must be be 1-21-2-3, 3, coun counti ting ng from from front front to back, back, top to bottom, or left to right, as viewed from the front of the switchgear assembly. Continuous current rating of the main power buses must be at least equal to the continuous current rating of the largest frame size of a circuit breaker installed in the switchgear assembly. Each bus must be braced to withstand a minimum short-circuit current of 42,000 symmetrical amperes at rated maximum voltage 600 V ac for a period that is not less than 4 cycles. The entire length of the power buses must be equally rated. Tapered bus sizing is prohibited. Buses and outgoing cable terminals must be directly connected to the stationary part of the primary disconnecting contacts of each circuit breaker. Cable is not allowed for use as a power bus. Neutral bus, bus, if specified specified in the Data Sheet, Sheet, must extend extend the full length length of the switchgear and must be insulated from ground. A bo bolted li link mu must be be pr provided fo for ne neutral bu bus bo bonding to to gr ground. Unless specified otherwise, the neutral bus must have a continuous current rating that is identical to the phase bus. A minimum 6 mm x 50 mm (1/4 inch x 2 inch) copper ground bus must be provided. A ground bus must be firmly secured to each vertical section structure, it must be located in the bottom of the switchgear and and it must extend the entire entire length of the switchgear. A ground bus must be drilled to accept two station ground cable terminal connectors (lugs). The terminal connectors must must be copper, two-hole NEMA, NEMA, compression (crimped) type, for use on 120 sq mm (4/0 AWG or 250 MCM) ICEA Class B or C stranded copper conductors and must be located in each vertical end-section.

Figure 13: Low-Voltage Switchgear Bus Construction Requirements


39



Figure 14 shows a table of low-voltage switchgear bus connection and cable termination construction requirements.

Bus Bus Bar Bar Connections (General)

All All cop coppe perr bus bus bar bar con conne nect ctio ion n sur surfa face cess mus mustt be be si silver lver-p -pla late ted d or or tin tin-p -pla late ted. d. All bus bar connections (splices) must be made by solidly bolting the bus bars together. Each bus bar connection must be secured with hex bolts, flat washers and split lock-washers, and hex nuts. Copper bus bar welding at splice point is not permitted. Factory installed bus bar connections that are not adjacent to, or connected with, a part of a circuit breaker must have a bolted overlap contact surface area. The bus bar contact surface area must have current density that is not higher than 31 A/cm2 (200 A/in2). The total temperature (hottest spot) of the bus bar bolted connection must not exceed 105 oC (221 oF). Main Bus Bar Main bus bar connections must be made with help of two overlapping splice Connections plates. Each main bus bar connection must have minimum four NEMA size holes (minimum of two NEMA holes in each bus bar end) for bolts. Main Bus Main bus-to-feeder connection must be made with help of at least one Tee-Off splicing copper plate. Connec Connecti tions ons The size size of of the the splici splicing ng plat platee and the the conne connecti cting ng port portion ion of of the feed feeder er bus bus must be governed by the busbar dimensions and the allowable current density. After the feeder bus bar leaves the contact area of a connection, the busbar must be sized on the basis of the allowable cross-section current density of copper. (Refer to Section 3.6 of UL Standard 67). Cable The load side buses of each circuit breaker compartment must have Terminations provisions (e.g., (e.g., be predrilled) to terminate terminate the required number number of cables as indicated on the engineering drawings. Power cable terminal connectors, lugs must be of the copper-bodied, two-hole NEMA compression (crimped) type that are suitable for ICEA Class B or C stranded copper conductors. Provisions must be made for power cables and/or cable terminator support so that the weight of the cables is not imposed upon the terminations. Figure 14: Low-Voltage Switchgear Bus Connection and Cable Termination Construction Requirements


40



Figure 15 shows a table of low-voltage switchgear nameplate construction requirements.

Device Nameplates Nameplates

Warning Plates

Device nameplates must be provided for the identification of each breaker and auxiliary unit that indicate the served load and circuit number or the equipment that is contained within a cubicle. All front panel mounted devices must be identified by a nameplate on the front of the panel and by a nameplate on the rear of the panel adjacent to each device terminal. All devices that are located within a panel must be provided with suitable nameplates to identify the item and its function. No abbreviations are permitted. Protective relay nameplates must be provided to indicate the protective function, the ANSI device number, and the phases that are monitored. All device nameplates must be engraved laminated plastic with black 6.4 mm (0.25 in) characters on a white 64 mm by 25 mm (2.5 in by 1 in) background as a minimum. Device nameplates must be in the English language according to American usage. Exterior and interior mounted nameplates must be attached with stainless steel or brass screws. Warning nameplates nameplates that read "CAUTION - THIS UNIT IS SUPP LIED BY AN EXTERNAL VOLTAGE SOURCE!" must be provided on each compartment door where an external voltage source is terminated. Auxiliary cubicles that contain drawout or tilt-out potential transformers that supply undervoltage relays must be provided with a warning nameplate that reads: "CAUTION - OPENING THIS COMPARTMENT TRIPS UNDERVOLTAGE RELAYS!" Each electrically operated power circuit breaker must have a clearly identified emergency trip button with a warning nameplate that reads: "EMERGENCY TRIP" Warning nameplates must be engraved laminated plastic with black letters on a yellow background. Warning nameplates must be written in both the Arabic and the English language.

Figure 15: Low-Voltage Switchgear Nameplate Construction Requirements


41



Information, Formulas, and Tables for Use in Evaluating the Results of Insulation Resistance (Megger) Tests

The results of all commissioning megger tests that are performed must be documented on the appropriate Saudi Aramco pre-commissioning form. The following following are the types of megger tests that can be conducted: •

Short time or spot reading

•

Time resistance

•

Dielectric Absorption Ratio

When the dielectric absorption ratio megger test is performed, the polarization index can be determined through use of the following equation:

Figure 16 provides insulation conditions for 60/30 second ratio results and for 10/1 minute ratio results.

Figure 16: 16: Dielectric Absorption Ratio Chart


42



Saudi Aramco Pre-Commissioning Forms

Figures 17 and 18 show the Saudi Aramco Switchgear-General Pre-Commissioning Form, P-023, and the Low-Voltage Power Circuit Breaker Pre-Commissioning Pre-Commissioning Form, P-008, which provide a field installation checklist for general switchgear and low-voltage power circuit breaker installations. The pre-commissioning form has a broad checklist of visual and mechanical inspections, as well as the listed electrical and tests that are required for switchgear and lowvoltage power circuit breaker breaker installations. installations. Space is also provided on the form for test test data.


43



WORK AID 2 (Cont'd)

Figure 17: Saudi Aramco Pre-Commissioning Pre-Commissioning Form, P-023, Switchgear-General


44



WORK AID 2 (Cont'd)

Figure 17: Saudi Aramco Pre-Commissioning Form, Form, P-023, Switchgear-General (Cont'd)


45



WORK AID 2 (Cont'd)



46



WORK AID 2 (Cont'd)



47



WORK AID 2 (Cont'd)

Figure 18: Saudi Aramco Pre-Commissioning Form, P-008, Low-Voltage Power Circuit Breakers


48



WORK AID 2 (Cont'd)

Figure 18: Saudi Aramco Pre-Commissioning Form, P-008, Low-Voltage Power Circuit Breakers (Cont'd)


49



WORK AID 2 (Cont'd)



50



WORK AID 2 (Cont'd)



51



The following is an excerpt from GI 2.710, New Construction Check List Example, that illustrates the overall checklist and sign-off for major pieces of electrical equipment. 3.

Electrical Equipment All substations, power cable, electrical equipment, including lighting and wiring, to be checked for proper application, operation, and grounds. Distribution panels, switches properly identified, and all energization certificate requests signed.

Construction Construction Agency

Power Distribution Dept.

Project Inspection

Commissioning (Note 1)


52



Figure 19 shows an excerpt from GI 2.710, General Instruction Manual, that illustrates the inspections and tests that should be performed on major pieces of electrical equipment prior to the turnover of a facility.

Figure 19: GI 2.l710 Excerpt


53



WORK AID 2 (Cont'd)

Figure 19: 19: GI 2.l710 Excerpt (Cont'd)


54



GLOSSARY breaker rated short-circuit current

The designated limit of available current at which the circuit breaker must interrupt interrupt the current within the required required time at the rated maximum voltage.

dielectric absorption ratio

The ratio of two timed insulation resistance readings (such as a 60-second reading that is divided by a 30-second reading).

polarization index

The ratio obtained by a ten-minute insulation resistance reading divided by a one-minute insulation resistance reading.

rated maximum voltage

The highest rms voltage for which an equipment item is designed; the upper limit for operation.

rated continuous current at 60 hz

The amount of current that can be continuously carried by the equipment primary circuit components (e.g., buses and bus connections) without exceeding the allowable temperature rise.

rated short-time current

The designated limit of available current at which the equipment must interrupt the current within the required time at the rated maximum voltage.

switchgear rated short-circuit current

The designated limit of available rms current at the rated maximum voltage that the low voltage switchgear must be required to withstand for not less than four cycles (on a 60 Hz basis).


55

Engineering Encyclopedia: Commissioning Low-Voltage Switchgear And Circuit Breakers

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