Electric motor 7

Engi ngine nee erin ring g Ency ncyclo clope pedia dia Saudi Sa udi A ramco DeskTop Standards

Motor Protection Requirements

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 contained in this document which which is not already in the public domain may not be copied, reproduced, sold, given, or disclosed to third parties, or otherwise used in whole, or in part, without the written permission of the Vice President, Engineering Services, Saudi Aramco.

Chapter : El Electrical File Reference: EEX21607

For additional information on this subject, contact W.A. Roussel on 874-1320

Engineering Encyclopedia

Electrical Motor Protection Requirements

C O NT E NT S

P AG E

TYPICAL FACTORS THAT ARE SPECIFIED ON A MOTOR NAMEPLATE .......................................................................................................1 Rated Volts .................................................................................................2 Full-Load Amperes.....................................................................................2 Service Factor (S.F.)...................................................................................3 Horsepower ................................................................................................3 Temperature Factors................................................................................... Factors................................................................................... 4 Temperature Temperature Rise............................................................................ 4 Insulation Class Class and Ambient Temperature..... ...............................4 Time (Duty)................................................................................................5 Locked-Rotor Codes...................................................................................5 Miscellaneous Information......................................................................... Information......................................................................... 6 Maker’s Name.................................................................................6 Frequency and Number Number of Phases ..................................................6 Speed ..............................................................................................6 ANSI/IEEE DEVICES AND FUNCTION NUMBERS THAT RELATE TO AC INDUCTION MOTOR PROTECTION PROTECTION ....................................................7 Purpose.......................................................................................................7 Standard Device Function Numbers...........................................................7 Device 2RS .....................................................................................7 Device 27 ........................................................................................7 Device 46 ........................................................................................9 Device 47 ........................................................................................9 Device 49 ........................................................................................9 Devices 50/50G/50GS ..................................................................10 Device 51LR .................................................................................10 Device 86M ..................................................................................10 Device 87M ..................................................................................10 Saudi Aramco DeskTop Standards



C O NT E NT S

P AG E

TYPICAL FACTORS THAT ARE SPECIFIED ON A MOTOR NAMEPLATE .......................................................................................................1 Rated Volts .................................................................................................2 Full-Load Amperes.....................................................................................2 Service Factor (S.F.)...................................................................................3 Horsepower ................................................................................................3 Temperature Factors................................................................................... Factors................................................................................... 4 Temperature Temperature Rise............................................................................ 4 Insulation Class Class and Ambient Temperature..... ...............................4 Time (Duty)................................................................................................5 Locked-Rotor Codes...................................................................................5 Miscellaneous Information......................................................................... Information......................................................................... 6 Maker’s Name.................................................................................6 Frequency and Number Number of Phases ..................................................6 Speed ..............................................................................................6 ANSI/IEEE DEVICES AND FUNCTION NUMBERS THAT RELATE TO AC INDUCTION MOTOR PROTECTION PROTECTION ....................................................7 Purpose.......................................................................................................7 Standard Device Function Numbers...........................................................7 Device 2RS .....................................................................................7 Device 27 ........................................................................................7 Device 46 ........................................................................................9 Device 47 ........................................................................................9 Device 49 ........................................................................................9 Devices 50/50G/50GS ..................................................................10 Device 51LR .................................................................................10 Device 86M ..................................................................................10 Device 87M ..................................................................................10 Saudi Aramco DeskTop Standards



T/C CHARACTERISTIC CHARACTERISTIC CURVES OF AC INDUCTION INDUCTION MOTORS ...............11 Thermal Capability Capability Curve ........................................................................11 Stall Time Vs Locked Rotor Rotor Current ............................................11 Motor Starting Curve................................................................................13 Locked-Rotor Current...................................................................13 Starting Time ................................................................................13 Full-Load Current .........................................................................13 THERMAL PROTECTION FUNDAMENTALS OF AC INDUCTION MOTORS.............................................................................................................15 Thermal Overload Protection ...................................................................15 Replica-Type Relays.....................................................................15 Resistance Resistance Temperature Detectors (RTDs)................................... 17 Protection Protection Versus Stall Time Time ........................................................18 Thermal Locked-Rotor Protection Protection............................................................18 ............................................................18 Induction Disc Relays................................................................... 19 Protection Protection Versus Stall Time Time ........................................................22 Combined Protection................................................................................23 Underprotection Underprotection - Device 49......................................................... 23 Overprotection Overprotection - Device 51........................................................... 23 FUNDAMENTALS OF FAULT PROTECTION PROTECTION FOR LOW AND MEDIUM VOLTAGE AC INDUCTION MOTORS...........................................24 Introduction Introduction ..............................................................................................24 Phase Faults..............................................................................................24 Current Limiting Fuses .................................................................25 Circuit Breakers ............................................................................26 Ground Faults...........................................................................................31 Residual Connection .....................................................................31 Zero Sequence Sequence Connection ...........................................................32 OTHER TYPES OF MOTOR PROTECTION FUNDAMENTALS FOR AC INDUCTION MOTORS................................................................................36 Saudi Aramco DeskTop Standards



Undervoltage Protection........................................................................... Protection........................................................................... 36 Purpose and Thermal Thermal Effects ........................................................36 Time-Delay Relays Relays - Device 27 ....................................................37 Coordination .................................................................................37 Phase Unbalance Unbalance Protection Protection .....................................................................39 Purpose and Thermal Thermal Effects ........................................................39 Voltage Unbalance Unbalance Relays - Device 47 47 ........................................39 Current Unbalance Relays Relays - Device 46 .........................................40 Voltage Unbalance (Low Voltage Voltage Motors).... ...............................46 Miscellaneous Protection..........................................................................47 High Speed Reclosing...................................................................47 Repetitive Starting Starting - Device 2RS ..................................................47 Protection Scheme One-Line One-Line Diagrams Diagrams ...................................................48 Low Voltage Voltage Motors.....................................................................48 Motors .....................................................................48 Medium Voltage Motors...............................................................51 SOLID-STATE MOTOR PROTECTION PACKAGE (MPP) FEATURES .........................................................................................................54 General Description.................................................................................. Description.................................................................................. 54 Features and and Capabilities Capabilities ..............................................................54 Benefits .........................................................................................54 Multilin MMR 269 Plus ...........................................................................55 Single-Line Single-Line Drawing..................................................................... 56 Protection Features .......................................................................58 Communication Features ..............................................................59 Diagnostic Features.......................................................................60 Other Features...............................................................................62 Westinghouse IQ-1000II ..........................................................................63 Block Diagram..............................................................................63 Protection Features .......................................................................65 Communication Features ..............................................................67 Saudi Aramco DeskTop Standards



Diagnostic Features.......................................................................68 Other Features...............................................................................73 GLOSSARY ........................................................................................................74

LIST OF FIGURES Figure 1. Typical Ac Motor Nameplate ................................................................1 Figure 2. Ac Motor Voltages ................................................................................2 Figure 3. Nema Temperature Ratings ...................................................................4 Figure 4. Locked-Rotor Kva Codes ......................................................................5 Figure 5. Ac Motor Protection One-Line Diagram ...............................................8 Figure 6. Motor Curves.......................................................................................12 Figure 7. Motor Starting Current ........................................................................14 Figure 8. Bl-1 T/C Curves...................................................................................16 Figure 9. Dt-3 Relay ...........................................................................................17 Figure 10. O/L Relay Protection .........................................................................18 Figure 11. Starting Time Ts < 20 Seconds..........................................................19 Figure 12. Starting Time 20 < Ts < 70 Seconds .................................................20 Figure 13. Starting Time Ts > Tlr .......................................................................21 Figure 14. L/R Relay Protection .........................................................................22 Figure 15. Combined Protection .........................................................................23 Figure 16. Current Limiting Fuses (R-Rated) .....................................................25 Figure 17. Fuse Protection ..................................................................................26 Figure 18. Mcp Protection ..................................................................................27 Figure 19. Phase Faults: Device 50....................................................................28 Figure 20. Partial Differential Protection.............................................................29 Figure 21. Full Differential Protection................................................................30 Figure 22. Residual Connection..........................................................................31 Figure 23. Zero Sequence Feeder Breaker..........................................................32 Figure 24. Three-Wire Circuit.............................................................................33 Figure 25. Four-Wire Circuit ..............................................................................33 Saudi Aramco DeskTop Standards



Figure 26. Zero-Sequence Connection................................................................34 Figure 27. Ground Fault Protection - Mv System...............................................35 Figure 28. Effects Of Voltage Variation .............................................................36 Figure 29. Time Curves - Undervoltage Relay ...................................................38 Figure 30. Cvq Relay ..........................................................................................39 Figure 31. Cm Relay ...........................................................................................40 Figure 32. Cm Relay Operating Characteristics..................................................41 Figure 33. Primary Open (Three-Line Diagram) ................................................42 Figure 34. Phasor Diagram (Primary Open) .......................................................43 Figure 35. Secondary Open (Three-Line Diagram) ............................................44 Figure 36. Phasor Diagrams (Secondary Open)..................................................45 Figure 37. Voltage Unbalance Derating Factors.................................................46 Figure 38. Protection: 0.75 Kw (1.0 Hp) Or Less...............................................48 Figure 39. Protection: Greater Than 0.75 Kw To 75 Kw (1.0 To 100 Hp) .......................................................................................................49 Figure 40. Protection: Greater Than 75 Kw (100 Hp) .......................................50 Figure 41. Protection: Class E2 Controllers (<1125 Kw) ..................................51 Figure 42. Power Circuit Breaker (<7500 Kw)...................................................52 Figure 43. Protection: Power Circuit Breaker (>7500 Kw) ...............................53 Figure 44. Multilin 269 Plus: Faceplate.............................................................55 Figure 45. Multilin 269 Plus: Legend ................................................................56 Figure 46. Multilin 269 Plus: Single-Line Drawing...........................................57 Figure 47. Multilin 269 Plus: Protection Features .............................................58 Figure 48. Iq-1000ii: Faceplate ..........................................................................63 Figure 49. Iq-1000ii: Block Diagram.................................................................64 Figure 50a. Iq-1000ii: Protection Features.........................................................65 Figure 50b. Iq-1000ii: Protection Features (Cont’d)..........................................66 Figure 51a. Iq-1000ii: Monitor Data.................................................................. 68 Figure 51b. Iq-1000ii: Monitor Data (Cont’d) ...................................................68 Figure 51c. Iq-1000ii: Monitor Data (Cont’d) ...................................................69 Figure 51d. Iq-1000ii: Monitor Data (Cont’d) ...................................................69 Saudi Aramco DeskTop Standards



Figure 52. Iq-1000ii: Alarm Conditions.............................................................70 Figure 53a. Iq-1000ii: Trip Conditions ..............................................................71 Figure 53b. Iq-1000ii: Trip Conditions (Cont’d) ...............................................72 Figure 54. Iq-1000ii: Internal Diagnostics .........................................................73

Saudi Aramco DeskTop Standards



TYPICAL FACTORS THAT ARE SPECIFIED ON A MOTOR NAMEPLATE NEC Article 430-7 states a motor nameplate must be marked with the following information: •

volts, full-load amperes, service factor, horsepower

•

temperature factors, time (duty), locked-rotor codes

•

maker’s name, frequency, number of phases, speed

Figure 1 is an example nameplate that contains the NEC minimum required nameplate information; 16-SAMSS-503 also requires the nameplate to contain additional information 2 pertaining to insulation class, winding temperature rise, type of bearings, rotor Wk , types of enclosure, etcetera.

Figur e 1. Typical AC Motor Nameplate


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Rated Volts The voltage marked on the motor nameplate is the rated motor terminal voltage per NEMA MG-1. The nominal three-phase system voltage that matches the rated three-phase voltage is listed in Figure 2.

Figur e 2. AC Motor Voltages Full-Load Amperes The full-load amperes marked on the motor nameplate are based on the rated voltage, horsepower, and frequency. Overload protection, as specified by NEC Art 430-32, is based on the marked full-load amperes.


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Service Factor (S.F.) When the voltage and frequency are maintained as per the nameplate markings, the motor may be overloaded up to the hp obtained by multiplying the rated hp by the service factor shown on the nameplate. When the motor is operated at the higher service factor, efficiency, power factor, and speed may be different than at rated load, but locked rotor torque and current, and breakdown torque remain unchanged. For example, a 100 hp, 1.15 S.F. motor may be safely loaded to 115 hp. Horsepower Horsepower is the rated output mechanical power that may be applied to the motor shaft. IEC motors are rated on output kW vice output hp, where 1hp equals 0.746 kW. For example, a NEMA MG-1 rated 1000 hp motor is equivalent to a nominal 750 kW (746 kW actual) IEC rated motor.


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Tempera tur e Factors The temperature rise or the insulation class and ambient temperature must be marked on the motor (See Figure 3). Note: Saudi Aramco motor specifications (17-SAMSS-502 and 503) require Class F insulation. However, for fractional horsepower motors, SAES-P-113 permits a minimum Class B insulation .

Figure 3. NEMA Tempera tur e Ratings

Tempera tur e Rise The temperature rise shown in the above Figure is based on motor operation at altitudes of o 1000 meters (3300 ft) or less, ambient temperatures of 40 C, and rated horsepower for 1.0 S.F. motors or 1.15 times rated horsepower for 1.15 S.F. motors. Insulation Class and Ambient Temperat ur e o

The insulation class as shown above (Figure 3) is based on a 40 C ambient, but if the motor is operated at higher ambients, the motor temperature rise must be calculated in accordance with NEMA MG 1-12.43.


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Time (Duty) The time ratings for motors, per NEMA MG1-10.36 are 5, 15, 30 and 60 minutes, and continuous. Note: Saudi Aramco specifications call for continuous duty motors only . Locked-Rotor Codes Both NEMA MG 1-10.37 and the NEC require the locked-rotor indicating code letters to be marked on the motor nameplate. The letter designations are based on full voltage and rated frequency (See Figure 4).

Figur e 4. Locked-Rotor kVA Codes


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Miscellaneous Information Maker’s Name The NEC requires the motor manufacturer’s name to be marked on the nameplate. Most manufacturers also include additional markings such as serial numbers, model numbers, bearing numbers, etcetera. Fr equency and Num ber of Phases The motor frequency (50 or 60 hertz) as well as the number of phases (1 or 3) are required markings on the motor nameplate. Virtually all other ratings are based on loadings at rated frequency. All AC motors are required by NEMA MG1-12.44 to operate successfully under running conditions at rated load and voltage and at plus or minus 5 percent frequency. Speed NEMA MG1-10 lists the synchronous speed of motors (N rpm = 120f/p), whereas the nameplate speed for induction rotors includes slip (rotor speed).


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ANSI/IEEE DEVICES AND FUNCTION NUMBERS THAT RELATE TO AC INDUCTION MOTOR PRO TECTION Purpose The devices in switching equipment are referred to by numbers, with appropriate suffix letters when necessary, according to the functions they perform. Exercise caution when interpreting the letter suffix: There are often dual meanings. For example, the suffix G can mean ground (50G) or generator (87G). The numbers are based on a system, and adopted as standard for automatic switchgear by ANSI/IEEE Std.C37.2. The system is used in connection diagrams, one-line diagrams, instruction books, and in specifications. Figure 5 is a one-line diagram showing application of standard ANSI/IEEE device numbers. Standa r d Device Function Numb ers Device 2RS A time-delay starting, or closing relay is a device that functions to give a desired amount of time delay before or after any point of operation in a switching sequence or protective relay system, except as specifically provided by device functions 48, 62, and 79. Saudi Aramco uses this device to block repetitive starting (RS) of large motors rated at 3750 kW(5000 hp) or larger. Device 27 An undervoltage relay is a device that functions on a given value of undervoltage. Saudi Aramco uses this device to detect undervoltage on a motor bus or individual motors.


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Figur e 5. AC Motor Pr otection One-Line Diagra m


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Device 46 A reverse-phase, or phase-balance current relay is a relay that functions when the polyphase currents are of reverse-phase sequence, when they are unbalanced, or when they contain negative phase-sequence components above a given amount. This relay is primarily used to protect motors against single-phasing (primary or secondary opens). Device 47 A phase-sequence voltage relay is a relay that functions on a predetermined value of polyphase voltage in the desired phase sequence. This relay, in conjunction with a Device 27 relay, is used to detect undervoltage, reverse phasing, and single- phasing of a motor. Device 49 A machine, or transformer thermal relay, is a relay that functions when the temperature of a particular element exceeds a predetermined value. These elements consist of a machine armature, or other load-carrying winding or element of a machine, or a power rectifier or power transformer (including a power rectifier transformer). Thermal relays are used to overload protect all Saudi Aramco motors; however larger motors require more sophisticated (capable) Device 49 relays. For example, a small 7.5 kW (10 hp) motor may be protected by a simple solder-pot overload device, whereas a large 3750 kW (5000 hp) motor would require use of a much more sophisticated ABB type BL-1 thermal overload relay.


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Devices 50/50G/50GS An instantaneous overcurrent, or rate-of-rise relay, is a relay that functions instantaneously on an excessive value of current or on an excessive rate of current rise, thus indicating a fault in the apparatus of the circuit being protected. Saudi Aramco uses this device for both phase and fault protection of motors. The suffix G is the abbreviation for ground and GS is the abbreviation for ground sensor. Module EEX216.04 will describe the different applications of Device 50. Device 51LR An AC time overcurrent relay is a relay with either a definite or inverse time characteristic that functions when the current in an AC circuit exceeds a predetermined value. Saudi Aramco uses this device to provide thermal locked-rotor (LR) protection for medium voltage motors. Device 86M A locking-out relay is an electrically-operated hand or electrically reset, relay that functions to shut down and hold a piece of equipment out of service on the occurrence of abnormal conditions. Saudi Aramco uses this device to lock out large motors (M) after occurrence of a fault. This device is activated by Device 87 . Note: Device 86 requires manual reset . Device 87M A differential protective relay is a protective relay that functions on a percentage, phase angle, or other quantitative difference of two currents or other electrical quantities. Saudi Aramco uses this device for fault protection of motors (M) rated greater than 4 kV.


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T/C CHARACTERISTIC C URVES OF AC INDUCTIO N MOTORS Thermal Capability Curve Heating characteristics of motors are very difficult to obtain and vary considerably with motor size and design. These heating characteristics are modeled as curves, and are an approximate average of an imprecise thermal zone, where varying degrees of damage or shortened insulation life may occur. Figure 6 shows a typical motor capability curve, which is the motor designer’s estimate of the amount of load current that may flow in the motor without exceeding permissible temperatures. Stall Time Vs Locked Rotor C ur r ent Cold Star t - The locked-rotor time (t LR) shown in Figure 6 depicts the time (capability) of the motor (current versus time), which is based on starting the motor cold (the motor windings, rotor, etcetera are at ambient temperature). Hot Star t - If the motor’s duty cycle permits hot starts - the motor windings, etcetera are at an elevated temperature, the manufacturer must be consulted to determine a permissible starting time (ts) to prevent motor damage.


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Figure 6. Motor Cur ves


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Motor Starting Curve Locked-Rotor Cur r ent The starting current is represented by the curve (solid line) as previously described in Figure 6 and the current (labeled LRA a and LRAs) shown in Figure 7. Asymmetrical (DC Transient) - The asymmetrical starting current (LRA a) exceeds the symmetrical locked rotor current (LRA s) during the first few cycles because of the transient direct current. This transient current appears, as it does under fault conditions, because the series reactance (inductance) prevents an instantaneous change in the magnitude of the alternating current. The magnitude of the asymmetrical starting current is approximately 1.5 LRAs for low voltage motors and 1.6 LRA s for medium voltage motors. Symmetrical - After the transient current decays, the starting current hovers near the symmetrical starting current (LRA s). The magnitude of this starting current is typically 4 to 6 times the motor’s full-load amperes (FLA). The exact amount is based on the subtransient reactance (X” d) of the motor, which ranges from 16.7 to 25 percent. Star ting Time The starting time (t s) of the motor is the approximate time it takes the motor to approach rated running speed. For purposes of this course, it is assumed that the starting time (t s) is less than the locked-rotor (stall) time (t LR). Full-Load Cur r ent After the motor reaches rated speed, it acquires its normal rated value (full-load amperes), assuming rated load, voltage and frequency.


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Figur e 7. Motor Start ing Cur r ent


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THER MAL PROT ECTIO N FUNDAMENTALS OF AC INDUCTION MO TORS Ther mal Overload Pr otection Overload (O/L) protection is always applied to motors to protect them from overheating. NEC Article 430-38 requires an O/L device in each phase except “where protected by other means.” This requirement (one-per-phase) is necessary because single phasing of the primary in a delta-wye configuration results in a 2:1:1 three-phase motor current relationship. This protection is provided by replica-type relays for small kW-rated motors and by resistance temperature detectors (RTDs) for larger motors. Replica-Type Relays Replica-type relays operate directly from motor circuit current. They receive their name “replica” because they tend to “replicate” the heating characteristics of the motor. For very small motors, this type of relay is simply a bimetallic element that operates within a heater unit. For large kW-rated motors, they are truly a type of overcurrent relay. For instance, Saudi Aramco specifies an ABB-type BL-1 O/L relay for motors rated 4 kV and larger and less than 7500 kW. Figure 8 is a T/C characteristic curve of a BL-1 relay.


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This relay is a temperature-compensated relay, which means it has different T/C curves depending on the motors’s temperature. For instance, if the motor is at room ambient (just turned on) when the O/L occurs, the relay responds to the 0 percent curve. If the motor has been running continuously, the relay would respond to the 100 percent curve. Because replica-type relays only respond to current, they will not typically protect for blocked ventilation.

Figur e 8. BL-1 T/C Cur ves


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Resistance Temperature Detectors (RTDs) RTD-type relays operate from exploring coils embedded by the manufacturer directly in the motor windings. They are commonly used in industrial applications in motors rated above 1125 kW (1500 hp). Note: Saudi Aramco (17-SAMSS-502) requires RTD applications in motors rated above 150 kW (200 hp). RTDs respond to temperature alone, and they will protect against blocked ventilation. Figure 9 is an ABB DT-3 type relay used to detect overtemperature (overloads) with RTDs in a large motor.

Figur e 9. DT-3 Relay


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Protection Versus Stall Time Thermal-type relays offer very good protection for light overloads as shown in Figure 10, but provide inadequate protection (shaded area) for heavy overloads or during starting.

Figur e 10. O/L Relay Protection Thermal Locked-Rotor Protection Thermal locked-rotor (L/R) protection, similar to O/L protection, involves the matching of a relay to the motor’s thermal capability curve, and at the same time remembering that the capability curve is at best an approximation. A motor with a locked-rotor condition is particularly vulnerable to damage because of the 2 large amount of heat generated (I R). Also, remember that a motor at standstill cannot dissipate the heat as well as a rotating motor.


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Induction Relays

Disc

The type of L/R protection depends on comparison of the starting time (t s) of the motor to its permissible locked-rotor time (tLR). If the starting time (ts) is less than or equal to 20 seconds, and less than L/R time (tLR), it is best to use an extremely inverse relay similar to types ABB CO-11 or GE IFC 77 (see Figure 11).

Figur e 11. Star ting Time t s < 20 Second s


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If ts is between 20 and 70 seconds and less than t LR, it is best to use a relatively flat relay similar to types ABB CO-5, CO-6 or GE IFC-95 (see Figure 12).

Figur e 12. Star ting Time 20 < t s < 70 Second s


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If ts is greater than t LR (see Figure 13), a mechanical zero-speed switch may be used. This device supervises an overcurrent unit (Device 51) and prevents its operating a timer when rotation is detected. Note: This scheme will not detect a failure to accelerate to full speed nor pullout with continued rotation.

Figur e 13. Star ting Time t s > t LR


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Pr otection Versus Stall Time The overcurrent relay offers excellent protection for heavy overloads as shown in Figure 14, but overprotects (shaded area) for light overloads.

Figur e 14. L/R Relay Pr otection


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Combined Pr otection The best (recommended) thermal protection for large motors is to combine both O/L and L/R protection as shown in Figure 15.

Figur e 15. Comb ined Pr otection Under pr otection - Device 49 A typical scheme is to provide two overload protective devices (i.e. BL-1 relays) in phases A and C, which underprotects (thermally) for heavy overloads (i.e. locked-rotor conditions), but adequately protects for light overloads. Over pr otection - Device 51 To complement Device 49 thermal protection, one locked-rotor device (i.e. CO relay) is applied to phase B, which overprotects for light overloads, but adequately protects for heavy (i.e. locked-rotor conditions).


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FUNDAMENTALS OF FAULT PRO TECT ION FOR LOW AND MEDIUM VOLTAGE AC INDUCTION MOTO RS Introduction As with thermal protection, the size of the motor and the type of service will influence the type of fault protection required to protect the motor. Although NEC Article 430-52 and Table 430-152 dictate phase and ground fault protection for low voltage motor circuits, the type of protective device is a designer’s choice. There are five types, each having different benefits depending on the size of the motor, cost of protection, etcetera. The five types used for low voltage motor protection are: •

non-time delay fuse (non-current limiting).

•

time delay fuses (current limiting).

•

inverse time circuit breaker.

•

magnetic only circuit breaker.

•

motor circuit protector (MCP).

Medium voltage motors, typically large and expensive, are fault protected by NEMA Type R current limiting fuses or differential relays. Ground fault protection can be provided by a residual scheme, but zero sequence protection is the preferred scheme. Phase Faults Although the NEC permits current limiting fuses for low voltage motor phase fault protection, Saudi Aramco SAES-R-114 specifies magnetic-only molded case circuit breakers or MCPs for protection of motors rated below 75 kW (100 hp), and devices 50 or 87 for all other motors (low and medium voltage).


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Cur r ent Limiting Fuses R-rated (NEMA Type R) current limiting fuses are used in NEMA Class E2 controllers to provide short circuit fault protection up to 350,000 kVA . Note: Class E2 controllers will be discussed in detail in EEX216.05 . Figure 16 lists the continuous current ratings of NEMA Type R fuses, while Figure 17 shows a typical T/C coordination scheme for protecting a medium voltage motor. Note: SAES-P-114 permits Class E2 controllers with current limiting fuses for motors rated 4.0 kV, 1125 kW (1500 hp) or smaller sized motors .

Figur e 16. Cur r ent Limiting Fuses (R-Rated)


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Figur e 17. Fu se Pr otection Circuit Breaker s SAES-P-114 requires: a) magnetic-only or MCP fault protection for low voltage motors rated less than or equal to 75 kW (100 hp); b) low voltage power circuit breakers (LVPCBs) for low voltage motors rated above 75 kW; and c) medium voltage power circuit breakers for motors rated greater than 1125 kW (1500 hp).


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Low Voltage Motors -The T/C characteristics of an MCP (or magnetic-only molded case circuit breaker) are shown in Figure 18.

Figure 18. MCP Pr otection


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Medium Voltage Motors - Phase fault protection for medium voltage motors rated above 1125 kW (1500 hp) is provided by a power circuit breaker controlled by relays. •

Instantaneous trip units (device 50) are recommended where the ratio I 3φ /LRAs is greater than 5 and the kVA rating of the motor is less than 50 percent of the kVA rating of the transformer (see Figure 19).

Figur e 19. Pha se Fau lts: Device 50


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•

Partial differential (Device 87M) is the preferred phase fault protection for large motors, and is recommended when I 3φ is approximately equal to LRA s, which varies from 4-6 times the full load, three-phase current. The advantage of this scheme is that it has excellent sensitivity, the starting currents cancel, and only three current transformers (CT) are required. The biggest problem with this protection scheme is a “physical limitation” based on the CT size (see Figure 20). Note: Saudi Aramco specifies differential protection (87M) only for medium voltage motors .

Figur e 20. Pa r tial Differ ential Pr otection


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• Full differential (Device 87M) is recommended whenever I 3φ is approximately equal to LRA s, which varies from 4-6 times the full load threephase current, and a partial differential scheme does not work. The only advantage of a full differential scheme over the partial differential scheme is that it offers cable protection. Obvious disadvantages are that six CTs are required, and the scheme is often oversensitive (nuisance trips) to high starting currents because of unequal CT saturation. (See Figure 21). Note: Saudi Aramco specifies differential protection (87M) only for medium voltage motors .

Figur e 21. Full Different ial Pr otection


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Gr ound Faults SAES-P-114 requires ground fault protection for all motors rated 22.5 kW (30 hp) and larger. Residual protection is permitted only on induction motors rated above 7500 kW (10,000 hp), where high cable charging currents would cause false operation of zero sequence (50GS) protection. Residual Conn ection The residual connection is not very sensitive because it “sees” current through the “eyes” of the phase CTs. This connection often causes nuisance trips as well because of the unequal saturation of the three CTs (see Figure 22).

Figur e 22. Residual Conn ection


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Zero Sequence Connection The zero sequence connection (Device 50GS) is the preferred ground fault protection scheme. Low voltage motors use a static trip (solid-state) device to trip the breaker, whereas a relay (ABB Type SC or GE Type PJC) trips the breaker via a lockout relay (Device 86M) for medium voltage motors. Note: Saudi Aramco typically specifies zero sequence CTs for ground fault protection . Low Voltage Motors - Figure 23 shows the zero sequence connection for protecting a low voltage motor. Figures 24 and 25 show alternate connection schemes with the zero sequence CT connection being the preferred Saudi Aramco connection.

Figur e 23. Zer o Sequence Feeder Break er


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Figure 24. Thr ee-Wire Cir cuit

Figur e 25. Four -Wire Circuit


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Medium Voltage Motors - Figure 26 shows the ground fault protection scheme for medium voltage motors. The primary advantages of this type of system are increased sensitivity (no current flows under normal conditions), which eliminates false tripping during motor starting and the lowest CT cost (only one required). The primary disadvantage is CT saturation, especially when induction disc (Device 51) relays and/or solidly-grounded systems are used.

Figur e 26. Zer o-Sequence Conn ection


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Figure 27 is a typical one-line diagram and accompanying coordination scheme using zero sequence ground fault protection schemes.

Figur e 27. Gr ound Fau lt Pr otection - MV System


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OTHE R TYPES OF MOTO R PROT ECTIO N FUNDAMENTALS FOR AC INDUCTION MOTORS Undervoltage Protection A low voltage condition will prevent motors from reaching their rated speed on starting, or cause them to lose speed and draw heavy overload current. While overload relays (Device 49) will eventually detect this condition, the motor should be quickly disconnected when severe low voltage conditions exist. Where continuous operation is essential, such as station auxiliary service or continuous manufacturing processes, an undervoltage relay is used for alarm purposes only. Pur pose and T herm al Effects The primary purpose of undervoltage relay protection (Device 27) in Saudi Aramco applications is as a backup device for locked rotor protection (Device 51). Device 51 is 2 applied to phase B, while Device 27 is applied to phases A and C. Because power (I R) is directly proportional to the current squared and any decrease in voltage (see Figure 28) results in an increase in current, Device 27 will eventually remove the motor if Device 51 fails, although some damage may occur as a result of the increased temperature (approximately 17 percent for just 10 percent low voltage).

Figur e 28. Effects of Voltage Var iation


36



Tim e-Delay R elays - Device 27 Time-delay voltage relays, similar to time delay overcurrent relays (Device 51), use induction disc relays for their time-undervoltage characteristics (see Figure 29). Coordination Device 27 relays must be coordinated with upstream fault relays to prevent tripping the motor for any upstream faults that cause voltage dips on the system. Additionally, caution must be exercised to ensure the relay does not trip due to voltage sags as a result of the motor, or adjacent large motors starting on the same bus.


37



Figur e 29. Time Cur ves - Under voltage Relay


38



Phase Unbalance Protection Pur pose and T herm al Effects The purpose of phase unbalance protection is to prevent motor overheating damage. Motor overheating occurs because increased phase currents flow in order that the motor can continue to deliver the same kW (hp) as it did with balanced voltages. Negative-sequence voltages also appear and cause abnormal currents to flow in the rotor. Because a motor’s negative sequence impedance (Z 2) approximates a motor’s locked rotor impedance, a small negative sequence voltage produces a much larger negative sequence current. Voltage Unb ala nce Relays - Device 47 SAES-P-114 recommends use of an ABB Type CVQ relay (see Figure 30) for voltage unbalance protection. This relay protects against system undervoltage (a Device 27 function), single-phasing of the supply, and reversal of phase rotation of the supply (100 percent negative sequence). No settings are required for the CVQ relay.

Figur e 30. CVQ Relay


39



Phase R eversal eversal protection is primarily protection for the process instead of protection for the motor. Imagine reversing the phases for a pump. The motor begins “sucking” the fluid instead of pumping the fluid . Cu r r ent Unba lance Relays - Devic Devicee 46 46 SAES-P-114 recommends use of an ABB Type CM current unbalance relay for motors rated above 1125 kW (1500 hp). hp). This relay is used to detect phase unbalance unbalance or open phase. It consists of two mechanically mechanically independent independent disc units. units. Phase A and B currents energize energize the upper electromagnets, while phase B and C currents energize the lower electromagnets. When phase currents are balanced, the electromagnets create equal and opposing torques on each of the discs (see Figure 31). •

The The rela relay y con conta tact ctss are are elec electr tric ical ally ly comm common on and and con conne nect cted ed in para parall llel el.. Clos Closin ing g of any one contact on either the upper or lower disc completes the trip circuit.

•

Beca Becaus usee the the CM rela relay y is is cal calib ibra rate ted d for for one one amp amper eree sen sensi siti tivi vity ty and and is is set set to operate on an unbalance, no setting of this relay is required.

•

Note Note:: If this this rela relay y is appl applie ied d on on a mult multii-mo moto torr bus, bus, an unba unbala lanc ncee on any any mot motor or could trip the entire entire bus. The best recommendation recommendation is to apply one CM relay relay per motor.

Figur e 31. CM Relay


40



Figure 32 describes the CM relay’s operating characteristics.

Figur Figur e 32. 32. CM Relay Oper ating Char acteristics acteristics


41



Single-Phasing is caused by the opening of either a primary or secondary conductor feeding a motor. Figures 33 through 36 describe the the three-wire three-wire and phasor phasor diagrams for these conditions.

Figure 33. 33. Pr imar y Open (Thr (Thr ee-Line ee-Line Diagra Diagra m) Primary open phasor diagrams and equations: •

IA = IA 1 + IA 2 = 1∠120 ° +1∠ 300° = 0

•

60° = 3∠30 30 °p . u. IB = IB 1 + IB 2 = 1∠0 ° +1∠ 60

•

IC = IC1 + I C2 = 1∠ 240° +1∠180 ° = 3∠ 210° p. u. = −IB

•

Ia = Ia1 + I a2 = 1∠ 90° +1∠330 ° = 1∠ 30° p .u.

•

Ib = Ib1 + I b2 = 1∠330 ° +1∠90° = 1∠ 30° p.u. = Ia

•

Ic = I c 1 + Ic 2 = 1∠240 ° +1∠240° = 2∠ 240° p .u.


42



Figure 34. 34. Phasor Diagra Diagra m (Pr (Pr imar y Open)


43



Figure 35. Secondar y Open (Thr ee-Line Diagr am)

Secondary open phasor diagrams and equations: •

IA = I A1 + I A 2 = 1 ∠120 ° + 1 ∠240 ° = 1 ∠180 ° = - 1.0 p.u.

•

IB = I B1 + I B2 = 1 ∠0 °+ 1 ∠0 ° = 2 ∠0 ° = 2.0 p.u.

•

IC = I C 1 + I C 2 = 1 ∠240 ° + 1 ∠120 ° = 1 ∠180 ° = - 1.0 p.u. = I A

•

Ia = I a1 + Ia 2 = 1 ∠90 ° + 1 ∠270 ° = 0

•

Ib = I b1 + Ib 2 = 1 ∠330 ° + 1 ∠30 ° = 3 ∠0 ° =

•

Ic = Ic 1 + I c2 = 1 ∠210 ° + 1 ∠150 ° =


3 p.u.

3 ∠180 ° - 3 p.u. = -I b

44



Figure 36. Phasor Diagram s (Secondar y Open)


45



Voltage Unb alance (Low Voltage M otors) Protection of low voltage motors using voltage unbalance relays is usually not cost effective. As previously discussed, increased heating occurs as a result of the voltage unbalance, and the only other practical means to reduce the thermal effects is to reduce the shaft kW (hp) loading in accordance with the following formula and Figure 37.

Max deviation from average voltage average voltage Percent NEMA unbalance =

Figur e 37. Voltage Unba lance Dera ting Fa ctors


46



EXAMPL E A:

Given the following data, what is the maximum safe connected shaft kW (hp) to avoid thermal overheating of the motor? Motor Ratings: 150 kW (200 hp), 3-phase, 460V Voltages: V ab = 449V, V bc = 459V, V ca = 421V

ANS WE R

Vavg = (449 + 459 + 421)/3 = 1329/3 = 443V Maximum voltage deviation from average = 443 - 421 = 22V Percent NEMA unbalance = (22/443) X 100 = 4.97% Per Figure 37, the motor should be derated approximately 75% to 112.5 kW (150 hp) for a 5% voltage unbalance. Note: Derating the motor is not the preferred method to avoid overheating. The preferred method is to correct the causes of the voltage unbalance. For example, removing single-phase loads from the motor bus, balancing the single-phase loads on the bus, etcetera.

Miscellaneous P r otection High Speed Reclosing If a motor is reenergized before it has stopped rotating, high transient torques can develop (T 2 α V ), and possible damage (e.g. broken shafts) can occur. The most probable cause of reenergization is utility high speed reclosing (10-36 cycles) after a fault. The simplest protection schemes are a timing relay that allows the motor to coast to a stop before restarting, or delaying restart using an undervoltage permissive relay in the starting control circuit set at 25-33% of normal voltage. Repetitive Star ting - Device 2RS Restarting motors with insufficient cooling time, or operating with extreme load variations (jogging) can result in dangerously high motor temperatures. Timing circuit protection schemes based on manufacturer-recommended starting cycles (e.g., 2 hot/1 cold per hour), or temperature sensitive relays, such as the CT relay just previously discussed, are also used to protect the motor against repetitive starting. Use of this type of relay requires very careful analysis of the motor and its projected operating cycles.


47



Protection Scheme One-Line Diagrams SAES-P-114 (Chapter 6) very clearly lists the preferred protection scheme for the various types of induction motors used in Saudi Aramco industrial applications. Figures 38 through 43 are one-line diagrams developed to describe the SAES-P-114 motor protection requirements. Low Voltage Motor s Voltage motor protection is separated based on the following motor rating categories: •

0.75 kW (100 hp) or less

•

Greater than .75 kW to 75 kW (1.0 to 100 hp)

•

Greater than 75 kW (100 hp)

0.75 kW (1.0 hp) or Less - This category of low voltage motor is protected by thermal magnetic molded case circuit breakers (MCCB) with three-pole thermal magnetic trips (Figure 38a), or combination controllers with overloads, a contactor, and a magnetic-only MCCB or thermal-magnetic MCCB as shown in Figure 38b.

Figur e 38. Pr otection: 0.75 kW (1.0 hp) or Less


48



Greater than 0.75 kW to 75 kW (1.0 to 100 hp) - This category of motor protection permits use of motor circuit protectors (MCP), and requires window-type CT ground fault protection for motors rated 22.5 kW (30 hp) and larger. Overload and contactor requirements are the same as the less than 0.75 kW (1.0 hp) category. The one-line diagram for this category is described in Figure 39.

Figure 39. Pr otection: Gr eater T han 0.75 kW to 75 kW (1.0 to 100 hp)


49



Gr eater T han 75 kW (100 hp) to a maximum of 185 kW (250 hp) - This category of motor requires a low voltage power circuit breaker (LVPCB), drawout type, electrically-operated, with shunt-trip device. Undervoltage protection (Device 27), in addition to ground fault protection (Device 50GS), is required for the larger, low voltage motors. SAES-P-114 permits individual or common bus undervoltage protection (see Figure 40).

Figure 40. Pr otection: Gr eater Than 75 kW (100 hp)


50



Medium Voltage Motor s Medium voltage motor protection is separated into the following two motor rating categories: •

150 kW (200 hp) through 7500 kW (10,000 hp)

•

7500 kW (10,000 hp) or greater

150 kW (200 hp) through 7500 kW (10,000 hp) - SAES-P-114 further breaks this category of motor protection into two sub-categories. Power circuit breakers are the typical protective devices with Class E2 controllers permitted for motors rated 1125 kW (1500 hp or less). Figure 41 is the recommended protection scheme using Class E2 controllers.

Figur e 41. Pr otection: Class E2 Contr ollers (<1125 kW )


51



Figure 42 is the recommended protection scheme using a power circuit breaker for motors rated 150 kW (200 hp) through 7500 kW (10,000 hp) ranges.

Figur e 42. Power Circuit Break er (<7500 kW )


52



7500 kW (10,000 hp ) or Gr eater - This category of motor requires differential (Device 87M) protection versus Device 50 short circuit protection, and temperature (Device 49T) protection as opposed to thermal overload protection using a BL-1 relay (Device 49). Additional overload protection for this motor category is also provided by using an ABB COM relay (see Figure 43).

Figur e 43. Pr otection: Power Cir cuit Br eaker (>7500 kW )


53



SOLID-STATE MO TOR PR OTEC TION PACKAGE (MPP) FEATURES General Description Solid-state motor protection packages (MPPs) are typically self-contained, door-mounted, motor protection devices. Saudi Aramco (SAES-P-114) permits use of MPPs for motors 4.0 kV or greater in any kW (hp) rating. Featur es and C apab ilities Solid-state MPPs (latest generation), such as the Multilin 269 Plus or Westinghouse IQ1000II, are the best or preferred method of protecting medium voltage motors in today’s industrial environment. These MPPs develop very accurate thermal models of the motor, and, therefore, the protection set points (for example, locked-rotor and thermal protection) can better match the thermal characteristics of the motor. In contrast, conventional relays are set to protect based on an estimate of the motor’s thermal capabilities. Algorithms, used in the 2 MPPs for the motor’s I t thermal characteristics, are calculated based on the motor’s actual load amps. Most MPPs also continuously calculate positive and negative sequence currents as well. The primary features of a typical MPP are: •

Protection

•

Communication

•

Diagnostics

Benefits The key benefit of an MPP is that these types of relays offer, for all practical purposes, unlimited motor protection. Another and often overlooked benefit is that they extend a motor’s life, because the protection set points are based on much more accurate thermal models of the motor. Note: Because all of the motor protection is in a single, self-contained package, a designer must consider backup electromechanical relays when fail-safe tripping is not allowable for an MPP failure.


54



Multilin MMR 269 Plus This relay is primarily a current (CT secondary) sensing relay. Voltage functions (metering and/or relaying) are optional. Figure 44 is a description of the MMR 269 Plus faceplate.

Figur e 44. Mu ltilin 269 Plus: Faceplate


55



Single-Line Dr awing Figure 45 is the legend describing the relays shown on the single-line drawing (Figure 46).

Figur e 45. Mu ltilin 269 Plus: Legend


56



Figur e 46. Mu ltilin 269 Plus: Single-Line Dra wing


57



Pr otection Featur es The protection features (relay functions) listed in Figure 47 are no different than their electromechanical counterparts. The differences are that all of the functions are selfcontained in one case, and the user enters the set points via a keypad. Note: SAES-P-114 requires a separate undervoltage relay (Device 27) if the meter option is not selected .

Figur e 47. Mu ltilin 269 Plus: Pr otection Featu r es


58



Communication Features The communication features of the relay provide motor data/status to a remote device such as a computer. The following list describes the communication features of the Multilin MMR 269 Plus. •

Overload alarm

•

Stator RTD alarm

•

Ground fault alarm

•

Undercurrent alarm

•

Unbalance alarm

•

Bearing RTD alarm

•

Broken RTD alarm

•

Undervoltage alarm (meter option only)

•

Power factor alarm (meter option only)

•

Self test alarm

•

Alphanumeric display

•

Actual motor values displayed

•

Status indication

•

RS485 port

•

Analog output load amps

•

Analog output motor thermal capacity

•

Analog output stator temperature

•

Analog output (average RMS amps) (meter option)

•

Analog output kW (meter option)

•

Analog output kVAR (meter option)

•

Analog output p.f. (meter option)


59



After the relay has been programmed and the motor is running, operations personnel, using the keypad, can demand the following list of actual values. •

Three-phase average current

•

Individual phase currents

•

Hottest stator RTD temperature

•

Individual stator RTD temperature

•

Maximum stator RTD temperature since last access

•

Unbalance ratio (% I n /lp)

•

Ground leakage current

•

Individual motor bearing RTD temperatures

•

Individual drive bearing RTD temperatures

•

Individual maximum bearing temperatures since last access

•

Thermal capacity remaining/ Estimated time to trip at present overload level

•

Motor load as a % of full load

•

Phase-to-phase voltage

•

kW, kVAR, MWH, p.f., frequency

Diagnostic Features The diagnostic features of the relay include the following: •

Learned motor parameters

•

Pre-trip values

•

Motor operation historical data

•

Latched fault indications

Several of the learned motor parameters include cool down time from run to stop, cool down time from run-overload to run-normal, learned negative sequence contribution, and acceleration time. To assist in fault diagnosis, the relay will identify the cause of trip and the following values can be recalled for rapid fault diagnosis. Saudi Aramco DeskTop Standards

60



•

Average motor current

•

Unbalance ratio

•

Ground fault current

•

Maximum stator RTD temperature

•

Phase voltage

•

kW

•

Power factor

•

Frequency

To assist in fault diagnosis, maintenance and operations monitoring, the relay will display the following list of statistical values. •

Running hours since last commissioning

•

Number of starts since last commissioning

•

Number of trips since last commissioning

•

Number of overload trips

•

Number of unbalance trips

•

Number of ground fault trips

•

Number of RTD trips

•

Number of short circuit trips

•

Number of start trips

•

Total watt-hours


61



Other Features Numerous other features as shown in the following list are also available on the relay. •

Emergency restart

•

Learned acceleration time

•

Start inhibit

•

Single shot restart

•

Output relays

•

Draw-out case option (extra)

•

Optional DC control supply (extra)

•

Exponential running cool down

•

Anti backspin timer


62



Westinghouse I Q-1000II The IQ-1000II is also a current (CT secondary) sensing relay. Figure 48 is a description of the IQ-1000II faceplate.

Figur e 48. IQ-1000II: Faceplate Block Diagra m Saudi Aramco DeskTop Standards

63



The IQ-1000II receives motor current sensing derived from 3 separate current transformers, each of which monitors one phase of an AC line to the motor (see Figure 49). If an optional zero sequence ground fault transformer is used, the IQ-1000II monitors ground fault current levels and compares them to a user-selected setpoint. If optional RTDs are used, the IQ1000II gathers winding temperature data from six RTDs embedded in the stator windings of the motor. Four RTDs associated with the motor and load bearings can also be monitored for temperature levels. Additionally, one auxiliary RTD, such as motor case temperature, can be monitored.

Figure 49. IQ-1000II: Block Diagram


64



Pr otection Featur es The IQ-1000II protection features are current sensitive only (see Figures 50a and b). SAESP-114 would, therefore, require a separate undervoltage relay (Device 27) to protect the motor.

Figure 50a. IQ-1000II: Pr otection Featur es


65



Figure 50b. IQ-1000II: Protection Features (Cont’d)


66



Communication Features IMPACC, a Westinghouse Local Area Network, can be used to communicate with one or multiple IMPACC-compatible devices. These devices include the following: IQ-500, IQ1000, IQ-1000 II, IQ Data Plus, IQ Data PlusII, IQ Data, IQ Generator, Digitrip, Addressable Relay II Advantage Motor Starters, and IQ Energy Sentinels. Up to 1000 devices can be connected on a network via shielded twisted pair wire. Four different communication levels are available and are described below: •

IMPACC Series I: Standardized software package that runs on a 100% IBMcompatible computer. The software is packaged with a computer interface card (CONI). Series I offers the following features: System Monitoring, Data Logging, Event Logging, Remote On/Off Control, Dialup Capabilities and Gateway Interface.

•

IMPACC Series II: Customer-written software for special applications. Custom software is required in situations where (1) Westinghouse software does not provide feature(s) desired by the customer or (2) the customer wants to communicate to a non-IBM compatible computer or a programmable controller. A MINT translator module converts device-messages into 10-byte ASCII RS-232 signal. An RS-232 Protocol Manual is included with each MINT.

•

IMPACC Series III: Standardized software package that runs on most 100% IBM-compatible computers. Series III requires a CONI or a MINT to operate. Series III runs in the Microsoft Windows environment and includes the following features: System Monitoring, Data Trending, Event Logging, Spreadsheet-compatible Trend and Log files, Remote On/Off Control, Gateway Interface, Device/System Alarming, Analog Alarming, Security (password protection) and Enhanced Graphics.

•

IMPACC Driver Software (Third Party Vendors): Data acquisition software written by third party vendors. Software drivers are available to gather data from systems such as IMPACC, Programmable Controllers and/or Energy Management Systems. The IMPACC Driver for ICONICS’ Genesis (real-time graphics interface program) offers the following features: System Monitoring, Data Trending, Event Logging, Remote On/Off Control Device/System Alarming, Customized Graphics and Communications to other Genesiscompatible systems (PLC’s), Energy Management Systems


67



Diagnostic Features The IQ-1000II has 52 set points, most of which can be used for diagnostic purposes (maintenance, troubleshooting, etcetera). Figures 51a, b, c, and d list the monitor data.

Figure 51a. IQ-1000II: Monitor Data

Figure 51b. IQ-1000II: Monitor Data (Cont’d)


68



Figure 51c. IQ-1000II: Monitor Data (Cont’d)

Figure 51d. IQ-1000II: Monitor Data (Cont’d)


69



Figure 52 lists the alarm conditions data.

Figure 52. IQ-1000II: Alarm Conditions


70



Figures 53a and b list the trip conditions.

Figure 53a. IQ-1000II: Trip Conditions


71



Figure 53b. IQ-1000II: Trip Conditions (Cont’d)


72



Other Features In addition to load-associated protection, the IQ-1000II relay also, through the use of special algorithms, provides rotor temperature protection. The relay continuously measures/monitors both the positive and negative sequence currents, and incorporates their combined effect into an algorithm that effectively tracks rotor temperature. Another unique feature of the relay is the internal diagnostics failure message capability as shown in Figure 54.

Figure 54. IQ-1000II: Internal Diagnostics


73



GLOSSARY American National Standar ds Institute (ANSI)

An organization whose members approve various standards for use in American industries.

ana log (outpu t)

One type of continuously variable quantity used to represent another; for example, in temperature measurement, an electric current output represents temperature input.

asymmetrical (cur r ent)

The combination of the symmetrical component and the direct-current component of the current.

current-limiting (fuse)

A fuse that, when it is melted by a current within its specified current-limiting range, abruptly introduces a high arc voltage to reduce the current magnitude and duration. Note : the values specified in standards for the threshold ratio, peak let2 through current, and I t characteristic are used as the measures of current-limiting ability .

diagnostic

Pertaining to the detection malfunction or mistake.

duty (rotating machinery)

A variation of load with time, which may or may not be repeated, and in which the cycle time is too short for thermal equilibrium to be attained.

horsepower (shaft) (hp)

The mechanical output (shaft) rating of a motor. (1) hp equals 746 watts. See kilowatt (shaft).

hottest-spot tempera tur e allowance rise

A conventional value selected to approximate the degrees of temperature by which the limiting insulation temperature

and

isolation

of

either a

One

exceeds the limiting observable temperature rise. induction motor

An alternating-current motor in which a primary winding on one member (usually the stator) is connected to the power source and in which a polyphase secondary winding or a squirrel-cage secondary winding on the other member (usually the rotor) carries induced current.

instantaneous (relay)

A qualifying term applied to a relay indicating that no delay is purposely introduced in its action.

Institute of Electrical and A worldwide society of electrical and electronics engineers. Electronics Engineers (IEEE)


74



joggin g

kilowatt (sha ft) (kw)

The quickly repeated closure of the circuit to start a motor from rest for the purpose of accomplishing small movements of the driven machine. The mechanical output (shaft) rating of a motor. horsepower (hp).

See

locked-rotor (rotating machinery)

The condition existing when the circuits of a motor are energized, but the rotor is not turning.

locked-rotor current

The steady-state current taken from the line with the rotor locked and with rated voltage (and rated frequency in the case of alternating-current motors) applied to the motor.

locked-rotor indicating kVA code letter

Code letters marked on a motor nameplate to show motor

low voltage

Voltage levels below 1000 volts usually called utilization level outages.

medium voltage

Voltage levels greater than or equal to 1000 volts and less than 100,000 volts.

motor p r otection the package (MPP )

A solid-state, self-contained motor protection relay, such as

National Electr ic Code (NEC)

An electrical safety code developed and approved every three years by the National Fire Protection Association (NFPA).

National Electr ical Manufacturers Association (NEMA)

A nonprofit trade association of manufacturers of electrical apparatus and supplies, whose members are engaged in standardization to facilitate understanding between users and manufacturers of electrical products.

negative sequence curr ent components sequence

Three balanced current phasors equal in magnitude, displaced 0 from each other by 120 in phase, and having the phase

per hp under locked-rotor conditions.

Multilin 269 Plus or the Westinghouse IQ-1000II.

opposite to that of the


original set of unbalanced phasors.

75



positive sequence curr ent components

Three balanced current phasors equal in magnitude, displaced 0 from each other by 120 in phase, and having the same phase sequence as the original unbalanced phasors.

relay

An electrically controlled, usually two-state, device that opens and closes electrical contacts to effect the operation of other devices in the same or another electric circuit.

r eplica temperatu re proportional relay

A

residual (current)

The sum of the three-phase currents on a three-phase circuit. The current that flows in the neutral return circuit of three wye-connected current transformers is residual current.

rotor (rotating machinery)

The rotating member of a machine with shaft.

service factor (S.F.)

A multiplier that, when applied to the rated power, indicates a permissible power loading that may be carried under the conditions specified for the service factor.

single-phasing (motor )

An abnormal operation of a polyphase machine when its supply is effectively single-phase.

starter (motor)

An electric controller for accelerating a motor from rest to normal speed and for stopping the motor.

starting cur r ent (rotating machinery)

The current drawn by the motor during the starting period. It is a function of speed or slip.

thermal

relay

whose

internal

temperature

rise

is

to that of the protected apparatus or conductor, over a range of values and durations of overloads.

stator The portion that includes and supports the stationary (rotating machinery) active parts. The stator includes the stationary portions of the magnetic circuit and the associated winding and leads. It may, depending on the design, include a frame or shell, winding supports, ventilation circuits, coolers, and temperature detectors. A base, if provided, is not ordinarily considered to be part of the stator. symmetr ical (curr ent)

A periodic alternating current in which points that are one-half a period apart are equal and have opposite signs.

synchronous speed

The speed of the rotation of the magnetic flux, produced by or linking the winding.


76

Electric motor 7

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