Electrical Commissioning

National Conference on Building Commissioning: May 20-22, 2003

Electrical Commissioning – Typical Power Equipment Problems Found in the Field Robert E. Fuhr, P.E.

Power Systems Engineering, P.S. Synopsis Many people assume that electrical power systems are static and do not need to be commissioned. Our experience in the field has shown otherwise. We have seen seen a variety of problems ranging from design mistakes, installation errors, errors, and equipment manufacturing defects. These problems are expensive reminders that the commissioning of electrical systems must be done. This paper will discuss some of the most common design, installation, and manufacturing problems for electrical power equipment. These are actual problems that we have found on our projects. It will alert the reader to the most common problems found during new construction. The reader can use some of the items listed in the paper as a checklist to use on their projects(Table 2). This paper will also include include numerous photos of defective equipment and installations. It will discuss the importance of electrical distribution system commissioning and why it must be performed at every facility…both new and existing. About the Author Robert Fuhr graduated with with a B.S.E.E. from from the University University of Wisconsin Wisconsin in 1980. Before graduating, Mr. Fuhr worked for Madison Gas and Electric in Madison, WI and Tennessee Valley Authority in Knoxville, TN. After graduation, he worked for the General Electric Company from 1980 to 1986 as a Field Engineer performing commissioning and start up tests on a multitude of power distribution equipment. From 1986 to 1989 he worked as a Senior Facilities Engineer at the University of Washington. While there, he re-commissioned the electrical power distribution system for the University Hospital. In 1986, he established Power Systems Engineering, a consulting firm that specializes in power system studies, power quality services, and commissioning commissioning services. In addition to his consulting services, he also teaches classes in electrical safety, power factor correction, harmonics and filter design. Mr. Fuhr is a Professional Engineer registered in Washington, Oregon, California, and Alaska. Bob is involved in IEEE and the Electric Electric League of the Pacific Northwest. He has served as an officer for IEEE-Industrial IEEE-Industrial Applications from from 1988 to 1992. He was the 1991-92 chairperson of

Fuhr Fuhr,, Rob Rober ert: t: Elec Electr tric ical al Comm Commis issi sion onin ing– g–Ty Typi pica call Pow Power er Equi Equipm pmen entt Pro Probl blem ems s Fou Found nd in the the Fie Field ld

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IAS. He was a member-at-large for the Seattle Section of IEEE for 1992-93. He is an IEEE Senior Member.


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Electrical Commissioning – Background There are many benefits, other than just cost savings, in performing electrical commissioning. When an electrical system is commissioned, any problems discovered during startup, while the equipment is under warranty, can easily be corrected by the equipment manufacturer or contractor. Other benefits may may include reduced downtime, reduced insurance premiums, and increased personnel and equipment protection. Electrical commissioning or acceptance testing, has been around for many years. For decades, the electric utilities have used extensive programs and testing procedures that have reduced construction delays and outages due to startup startup problems. Commercial and industrial facilities facilities eventually adopted these procedures and techniques. In 1972, several testing companies formed the InterNational Electrical Testing Association (NETA) to further further promote and standardize standardize commissioning and acceptance testing. The organization created NETA Acceptance Testing Specifications for use on new equipment installation and startup. They also implemented a test technician and testing company certification program. Their specifications are widely used on projects throughout the country. There are many codes, standards, and other requirements that mandate some electrical e lectrical testing and commissioning. State Labor and Industry departments, local local electrical inspectors or “authorities having jurisdiction” (AHJ) may have additional testing requirements. Table 1 lists some of the codes and standards that require require electrical commissioning. The National Fire Protection Association (NFPA) has also addressed the need for commissioning commissioning of electrical equipment with its Recommended Practice of Electrical Equipment Maintenance, NFPA-70B.

Table 1 – Codes and Standards Requiring Commissioning Code or Regulation National Electric Code (NFPA 70) National Electric Code (NFPA 70) National Electric Code (NFPA 70) National Electric Code (NFPA 70) National Electric Code (NFPA 70) Standard for Emergency Power Systems (NFPA 110) Standard for Emergency Power Systems (NFPA 110) Standard for Emergency Power Systems (NFPA 110)

Section 701-5 700-4 230-95c 250-84 410-45 5-13 5-13.2 .2.3 .3

Description of Commissioning Test of legally required standby systems Test of complete emergency power system Field test of equipment ground fault protection Service grounding electrode resistance test Short circuit and ground test for fixture wiring Cold Cold star startt tes testt of of sys syste tem m

5-13 5-13.2 .2.5 .5

Load Load ban bank k (full (full load load)) test test of of the the syst system em

5-13.2.8

Cyc Cycle crank te test

In summary, electrical power system commissioning provides the following benefits: • •

Determines if the components and system have been properly installed and are not damaged Reduces downtime


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• • • • • • •

• •

Reduces risk of equipment failure Increases safety Improves insurability Reduces liability exposure of the designers and installers Improves system performance Determines whether components and systems operate properly and meet the design intent Determines if components and systems are in compliance with the project specifications and design Reduces construction schedule delays Saves money

The electrical distribution system system is the foundation for for all other systems in the building. These systems include communication, fire fire and/life safety, security, and all mechanical systems. It is the electrical distribution system system that provides power to to all of these other systems. systems. Without reliable power, these other systems will not function properly.

Electrical Commissioning – Previous Studies NFPA-70B references a study conducted by Factory Mutual on losses associated with electrical failures. The study documented 766 losses totaling $6,548,590. Over 50% were caused by inadequate maintenance and testing. These 433 failures cost an estimated estimated $3,595,850. The Institute of Electrical and Electronic Engineers (IEEE) published Standa rd 493, Reliable Industrial and Commercial Power Systems Systems (Gold Book). The standard lists statistics statistics on the reliability of various electrical electrical equipment and systems. The Industrial Applications Society of IEEE performed an electrical equipment failure survey and categorized the types of failures. These categories are listed below: • • • • • • • • •

Manufacturer-defective component Application engineering or improper application Inadequate installation and testing prior to startup (commissioning) Transportation to site – defective handling Inadequate operating procedures Inadequate maintenance Outside agency-personnel Outside agency-other Other

The first four categories are problems that occur during the construction phase and usually have the greatest effect on the construction construction schedule. IEEE found that these four four categories represent over 40% of the failures. A thorough commissioning commissioning program would have discovered these problems. Performing commissioning prior to the contractor leaving and the owner moving in allows an orderly Fuhr Fuhr,, Rob Rober ert: t: Elec Electr tric ical al Comm Commis issi sion onin ing– g–Ty Typi pica call Pow Power er Equi Equipm pmen entt Pro Probl blem ems s Fou Found nd in the the Fie Field ld

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identification and resolution of the electrical system. With all of the players on board, the contractor, owner, equipment manufacturers, and equipment e quipment distributors can all contribute by offering solutions to correct the problems. The outcome is a fully commissioned, commissioned, fully functioning building with all system problems identificd and resolved be fore the owner moves in.

Our Experience and What We Have Found For over 15 years, Power Systems Engineering has been providing a variety of electrical commissioning services to commercial and industrial clients. During this period, we have seen many equipment problems. When we find these problems, we fill out either a Deficiency Form or Field Problem Observation Form. Form. These forms help us to to document and track the problems until completion. Chart #1 shows the breakdown of deficiencies deficiencies for eleven projects. The chart shows that 58% of the problems found are due to installation mistakes or problems made by the various contractors. co ntractors. Defective components represented almost a third third of the problems found. found. The next largest problem area representing 14% of the problems, was improper design or application of the devices. The final category is component damaged during transit transit to the job site. site. Although this represented only 1% of the deficiencies, they the y still can cause severe problems that can easily delay the construction schedule. Photo #1 shows an example of damage that was caused by a metal clip that loosened up during transit. transit. After the switchboard was installed, the clip eventually fell, causing a line-to-ground fault. fault. This accident caused an extensive amount of damage. Deficiency Breakdown

1% 27%

Defective Design/Application Installation Transportation Damage

58% 14%


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Chart - 1 Deficiency Breakdown for Various Commissioning Projects

Photo 1 - Main Switchboard Fault caused by Loose Metal Clip Lack of Proper Circuit Breaker Trip Unit and Relay Settings A common problem that we see is the failure of the electrical design engineer enginee r to specify and the contractor to provide trip settings settings for circuit breakers and relays. Many of the circuit breakers have solid state trip units units with multiple settings settings available (see Photo #2). The function of these protective devices is to monitor the current level and trip open the circuit breaker if the current exceeds the set points and delay times. A protective device coordination study determines the proper current pickup levels and time delays for the breakers and relays. relays. The goal of the study is minimize the effects of an outage when a fault occurs. A correctly set circuit breaker will have current pick up values and time delays set so that when a short circuit is sensed, the trip unit will trip the breaker closest to the fault. This is called selective device coordination. The breakers are said to be coordinated.


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To limit their liability, the equipment manufacturer will ship their equipment with the current pickup and time delays set on minimum. Many owners and contractors falsely assume that the manufacture has determined the device trip settings at the factory and has adjusted these devices before shipping the equipment. This incorrect assumption causes many of the devices to trip when they are not supposed to.

Photo 2 - Ground Fault Relay In the year 2000, we received a call from a hospital saying that they had just experienced a large power outage. The main breaker for an eight-story wing had tripped when a contractor accidentally cut the power cord to the saw that he was using. When the main breaker was installed in 1995, the trip unit settings had been set to minimum. These low settings of current and time delays prevented the 1200-ampere main breaker from coordinating with downstream 20-ampere circuit breakers. Had a protective device coordination study been conducted and the main breaker set correctly, cutting through the power cord would have resulted in loss of power to a small localized area rather than the entire eighty-story wing. To prevent this from happening on your projects, we highly recommend verifying that Protective Device Coordination requirements are clearly stated in the project specifications. specifications. A protection specialist should be hired to perform the study. Then verify that the correct settings have been Fuhr Fuhr,, Rob Rober ert: t: Elec Electr tric ical al Comm Commis issi sion onin ing– g–Ty Typi pica call Pow Power er Equi Equipm pmen entt Pro Probl blem ems s Fou Found nd in the the Fie Field ld

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programmed into the trip units and relays before the electrical system is energized (See Photo #3). We have seen some projects where the coordination study was performed performed but no one programmed the settings into the breaker trip units and relays. Again this led to unplanned trips and outages. Through commissioning, breakers and relays could have been set properly to avoid these problems.


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Photo 3 - Circuit Breaker Trip Unit Motor HP and Starter Size Problems Another problem that occurs on almost every project is improper motor overload protection. Motors are controlled and protected by motor motor starters. These starters contain overload relays that monitor the current and will trip the motor off-line if the motor current exceeds the overload setting. On most projects, the mechanical engineer determines determines the motor size. size. The electrical engineer determines the motor starter size based upon the information the mechanical engineer has provided him/her. Even on projects where good communication exists between the mechanical and electrical engineers, we find motor starters and overload relays that are not sized properly for the motor that the relays are supposed to protect. As the number of parties in the design/manufacturing loop increases, the potential for a mismatch between the motor and overload relay also increases. Sometimes the mechanical mechanical engineer specifies skid-mounted skid-mounted equipment. The skid manufacturer will change the motor size without telling the mechanical design engineer. Without the mechanical engineer informing the electrical engineer of this change, we again have a motor and relay mismatch. Often the electrical contractor does not discover this mismatch. Electrical commissioning would identify this mistake and prevent the resulting problems. Photo #4 & #5 shows a mismatched mismatched motor starter overload and motor. motor. Note that the motor nameplate ampere rating (40 amperes) is much larger than the maximum motor overload relay full load amperes (3 amperes). amperes). In this example, the motor starter had to be changed out to a larger one.


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Photo 4 - Motor Overload Relay

Photo 5 - Motor Nameplate Medium Voltage Distribution System Installation Problems Many large, campus-type projects distribute distribute medium voltage power. This requires the use of medium voltage cables, stress cones, current transformers, and protective relays. For these distribution systems, it is extremely important to install the stress cones (see Photo #6) and cable splices properly. Stress cones and splices are are the weak points of the system and are usually where faults and failures occur. After the medium voltage cables, stress cones, and splices are installed, they must be hi-potted (insulation resistance tested) to assure that the installation is Fuhr, Robert: Electrical Commissioning–Typical Power Equipment Problems Found in the Field 10


correct. It is not uncommon to have one or two bad stress cones or splice installations installations on a project. Another common problem in medium voltage v oltage distribution systems involving current transformers and relays is the cable shield grounding lead. Many electricians mistakenly think the ground leads should not pass through the ground fault relay current transformers. Failure to do so will result in defeating the detection and removal of a cable ground fault. This will cause more equipment damage than normal. The photo #7 below shows the silver cable shield grounding leads installed outside of the current transformer. They should pass through the transformer not outside of it.

Photo 6 – Cable Stress Cone

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Photo 7 – Cable Shield Grounding Conductor Incorrectly Installed Problems with Switchboard / Panelboard Metering Packages Many projects now have sophisticated metering packages installed on the main switchboard or downstream distribution panelboards (See (See Photo #8). These meters are sometimes sometimes networked together so that the distribution system can be monitored on a remote computer. Many of these meters are required to be set and adjusted for use with the correct voltage / current transformers and transformer transformer winding connection. Many times this is is not done at the factory, as one would expect. Sometimes the discovery is not made until months after after the owner has moved in. These devices should should be commissioned commissioned before energizing the equipment. Failure to do so may require an outage after the owner has moved in to fix the problem.



Photo 8 – Solid State Metering Packages

Emergency Distribution Component Problems Emergency Distribution systems consist of generators (Photo #9), automatic transfer switches (ATS), switchboards, panelboards, and other equipment. They are necessary for emergency lighting, fire alarm system, system, smoke control, and other critical critical systems. Commissioning the components of the emergency distribution system is a must. Typical problems that we find are as a s follows: Incorrect or no ATS controller settings (Photo #10) Failure of engine start or cool down circuit from the ATS to the generator gen erator Failure of the generator to supply or control power to non-linear loads such as a s UPS units, lab equipment, computers, and solid state lighting ballasts.

• • •



Photo 9 – Emergency Generator

Transfer Switch Controller Controller Photo 10 – Automatic Transfer Fuhr, Robert: Electrical Commissioning–Typical Power Equipment Problems Found in the Field 14


Noisy Distribution Transformers Dry type distribution transformers are commonly used in many buildings to reduce the voltage from 480/277 to 208/120 Volts. Most of the transformer transformer manufacturers have shipping bolts (See Photo #11) that keep the transformer secure during shipment to the job site, which reduces transportation damage. Many times the electrical contractor contractor fails to loosen loosen these shipping bolts. This causes the transformer transformer to be very noisy and resonate when energized. This is very annoying for the building occupants located near the transformer. Commissioning ensures that these bolts are checked and verifies that they are loose before the transformer is energized.

Photo 11 – Distribution Shipping Bolt (Shown not loosened) Illegal Neutral to Ground Bonds The National Electric Code requires that the neutral conductor be bonded to ground. This is done at the main service switchboard or switchgear and on the secondary side of step down distribution transformer. This is to prevent returning returning neutral current from splitting and flowing Fuhr, Robert: Electrical Commissioning–Typical Power Equipment Problems Found in the Field 15


on the green equipment grounding safety conductor. Figure #1 shows a correctly installed neutral ground bond at the main panel. Figure #2 shows an illegal neutral to ground bond in the Sub-Panelboard.

Figure 1 - Correctly Neutral to Ground Bond at Main Panel



Figure 2 - Illegal Neutral to Ground Bond at Sub-Panel Our experience has shown that it is extremely common to have an inadvertent neutral to ground bond downstream from the neutral grounding point. Many of these bonds are pinched neutrals in lighting fixtures. This can cause neutral current to flow on equipment grounding conductors and cause ground fault protection systems to mis-operate. It some cases, it has caused the main breaker to trip out, causing a wide spread power outage. Before energizing the main switchboard, but after the conductors, panelboards, and lighting have been installed, an insulation resistance test (megger test) should be performed performed on the neutral conductor. The test is done by removing removing the single single (legal) neutral to ground bond and measuring the resistance between neutral and ground. This measurement should be at least one megohm. If the value is lower, lower, it usually indicates that the neutral is grounding somewhere somewhere downstream. Therefore, one would continue to lift neutral neutral wires from the neutral bus and measure the resistance to ground until the grounded neutral is found.

Summary Although there are many different types of o f problems and deficiencies that we have found throughout the last fifteen years, years, the items discussed discussed above are the most common problems. problems. By focussing on these items, you will uncover many of the problems that will plague your project.



The checklist below (Table 2) 2 ) is not meant to be a replacement for performing a full-service electrical commissioning program for your project. However, it will give you a good idea of some common problems and mistakes that see repeatedly on our projects.

Table 2: Common Electrical Problems Problem Description Lack of Proper Circuit Breaker Trip Unit and Relay Settings

Solution Specify that contractor must hire a protection specialist to perform a Protective Device Coordination Study (PDC) and testing company to adjust the breakers.

Motor HP an and Starter Size Problems

Mechanical, El Electrical de design en engineer and manufacturer must coordinate with each other during design phase. Field verify as soon soon as equipment has arrived on site

Medium Voltage Distribution System Installation Problems

Perform Hipot (insulation resistance test) on all cables, stress cones, and splices.

Switchboard / Panelboard Metering Packages Problems

Test equipment before energizing

Emer Em erge genc ncy y Distr Distrib ibut ution ion Com Compon ponen entt Prob Proble lems ms

Test Test all all emerg emergen ency cy dist distri ribu buti tion on syste system m comp compon onen ents ts.. Then perform a system test by having the generator using actual building non-linear loads.

Noisy Distribution Transformers

Check and verify that the shipping bolts are loose.

Illegal Neutral to Ground Bonds

Remove neutral to ground bond at main service and measure the insulation resistance between neutral and ground.


Electrical Commissioning

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