electrical commissioning

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

Fuhr, Robert: Electrical CommissioningTypical Power Equipment Problems Found in the Field 1

Electrical Commissioning Typical Power EquipmentProblems 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 becommissioned. Our experience in the field has shown otherwise. We have seen a variety ofproblems ranging from design mistakes, installation errors, and equipment manufacturingdefects. These problems are expensive reminders that the commissioning of electrical systemsmust be done.

This paper will discuss some of the most common design, installation, and manufacturingproblems for electrical power equipment. These are actual problems that we have found on ourprojects. 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 theirprojects(Table 2).

This paper will also include numerous photos of defective equipment and installations. It willdiscuss the importance of electrical distribution system commissioning and why it must beperformed at every facilityboth new and existing.

About the Author

Robert Fuhr graduated with a B.S.E.E. from the University of Wisconsin in 1980. Beforegraduating, Mr. Fuhr worked for Madison Gas and Electric in Madison, WI and TennesseeValley Authority in Knoxville, TN.

After graduation, he worked for the General Electric Company from 1980 to 1986 as a FieldEngineer performing commissioning and start up tests on a multitude of power distributionequipment.

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 UniversityHospital.

In 1986, he established Power Systems Engineering, a consulting firm that specializes in powersystem studies, power quality services, and commissioning services. In addition to hisconsulting 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 League of the Pacific Northwest. He has served as anofficer for IEEE-Industrial Applications from 1988 to 1992. He was the 1991-92 chairperson of


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IAS. He was a member-at-large for the Seattle Section of IEEE for 1992-93. He is an IEEESenior 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 orcontractor. Other benefits may include reduced downtime, reduced insurance premiums, andincreased 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 reducedconstruction delays and outages due to startup problems. Commercial and industrial facilitieseventually adopted these procedures and techniques.

In 1972, several testing companies formed the InterNational Electrical Testing Association(NETA) to further promote and standardize commissioning and acceptance testing. The

organization created NETA Acceptance Testing Specifications for use on new equipmentinstallation and startup. They also implemented a test technician and testing companycertification program. Their specifications are widely used on projects throughout the country.

There are many codes, standards, and other requirements that mandate some electrical testingand commissioning. State Labor and Industry departments, local electrical inspectors orauthorities having jurisdiction (AHJ) may have additional testing requirements.

Table 1 lists some of the codes and standards that require electrical commissioning. TheNational Fire Protection Association (NFPA) has also addressed the need for commissioning ofelectrical equipment with its Recommended Practice of Electrical Equipment Maintenance,

NFPA-70B.

Table 1 Codes and Standards Requiring CommissioningCode or Regulation Section Description of CommissioningNational Electric Code (NFPA 70) 701-5 Test of legally required standby systemsNational Electric Code (NFPA 70) 700-4 Test of complete emergency power systemNational Electric Code (NFPA 70) 230-95c Field test of equipment ground fault protectionNational Electric Code (NFPA 70) 250-84 Service grounding electrode resistance testNational Electric Code (NFPA 70) 410-45 Short circuit and ground test for fixture wiringStandard for Emergency Power Systems(NFPA 110)

5-13.2.3 Cold start test of system

Standard for Emergency Power Systems

(NFPA 110)

5-13.2.5 Load bank (full load) test of the system

Standard for Emergency Power Systems(NFPA 110)

5-13.2.8 Cycle crank 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 anddesign

Reduces construction schedule delays

Saves money

The electrical distribution system is the foundation for all other systems in the building. Thesesystems include communication, fire and/life safety, security, and all mechanical systems. It isthe electrical distribution system that provides power to all of these other systems. Withoutreliable 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 electricalfailures. The study documented 766 losses totaling $6,548,590. Over 50% were caused byinadequate maintenance and testing. These 433 failures cost an estimated $3,595,850.

The Institute of Electrical and Electronic Engineers (IEEE) published Standard 493, ReliableIndustrial and Commercial Power Systems (Gold Book). The standard lists statistics on thereliability of various 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 havethe greatest effect on the construction schedule. IEEE found that these four categories representover 40% of the failures.

A thorough commissioning program would have discovered these problems. Performingcommissioning prior to the contractor leaving and the owner moving in allows an orderly


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identification and resolution of the electrical system. With all of the players on board, thecontractor, owner, equipment manufacturers, and equipment distributors can all contribute byoffering solutions to correct the problems. The outcome is a fully commissioned, fullyfunctioning building with all system problems identificd and resolved before the owner moves

in.

Our Experience and What We Have Found

For over 15 years, Power Systems Engineering has been providing a variety of electricalcommissioning services to commercial and industrial clients. During this period, we have seenmany equipment problems. When we find these problems, we fill out either a Deficiency Formor Field Problem Observation Form. These forms help us to document and track the problemsuntil completion.

Chart #1 shows the breakdown of 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.Defective components represented almost a third of the problems found. The next largestproblem area representing 14% of the problems, was improper design or application of thedevices.

The final category is component damaged during transit to the job site. Although thisrepresented only 1% of the deficiencies, they still can cause severe problems that can easilydelay the construction schedule. Photo #1 shows an example of damage that was caused by ametal clip that loosened up during transit. After the switchboard was installed, the clipeventually fell, causing a line-to-ground fault. This accident caused an extensive amount ofdamage.

Deficiency Breakdown

27%

14%

58%

1%

Defective

Design/Application

Installation

Transportation Damage


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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 to specify and thecontractor to provide trip settings for circuit breakers and relays. Many of the circuit breakershave solid state trip units with multiple settings available (see Photo #2). The function of theseprotective devices is to monitor the current level and trip open the circuit breaker if the currentexceeds the set points and delay times.

A protective device coordination study determines the proper current pickup levels and timedelays for the breakers and relays. The goal of the study is minimize the effects of an outagewhen a fault occurs. A correctly set circuit breaker will have current pick up values and timedelays set so that when a short circuit is sensed, the trip unit will trip the breaker closest to thefault. 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 currentpickup and time delays set on minimum. Many owners and contractors falsely assume that themanufacture has determined the device trip settings at the factory and has adjusted these devicesbefore 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 largepower outage. The main breaker for an eight-story wing had tripped when a contractoraccidentally cut the power cord to the saw that he was using. When the main breaker wasinstalled 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 downstream20-ampere circuit breakers. Had a protective device coordination study been conducted and themain breaker set correctly, cutting through the power cord would have resulted in loss of powerto a small localized area rather than the entire eighty-story wing.

To prevent this from happening on your projects, we highly recommend verifying that ProtectiveDevice Coordination requirements are clearly stated in the project specifications. A protectionspecialist should be hired to perform the study. Then verify that the correct settings have been


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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 but no oneprogrammed the settings into the breaker trip units and relays. Again this led to unplanned tripsand 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 starters. These starters contain overload relays thatmonitor the current and will trip the motor off-line if the motor current exceeds the overloadsetting.

On most projects, the mechanical engineer determines the motor size. The electrical engineerdetermines the motor starter size based upon the information the mechanical engineer hasprovided him/her.

Even on projects where good communication exists between the mechanical and electricalengineers, we find motor starters and overload relays that are not sized properly for the motorthat the relays are supposed to protect. As the number of parties in the design/manufacturingloop increases, the potential for a mismatch between the motor and overload relay also increases.Sometimes the mechanical engineer specifies skid-mounted equipment. The skid manufacturerwill change the motor size without telling the mechanical design engineer. Without themechanical engineer informing the electrical engineer of this change, we again have a motor andrelay mismatch. Often the electrical contractor does not discover this mismatch. Electricalcommissioning would identify this mistake and prevent the resulting problems.

Photo #4 & #5 shows a mismatched motor starter overload and motor. Note that the motornameplate ampere rating (40 amperes) is much larger than the maximum motor overload relayfull load amperes (3 amperes). In this example, the motor starter had to be changed out to alarger one.


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Fuhr, Robert: Electrical CommissioningTypical Power Equipment Problems Found in the Field10

Photo 4 - Motor Overload Relay

Photo 5 - Motor Nameplate

Medium Voltage Distribution System Installation Problems

Many large, campus-type projects distribute medium voltage power. This requires the use ofmedium voltage cables, stress cones, current transformers, and protective relays. For thesedistribution systems, it is extremely important to install the stress cones (see Photo #6) and cablesplices properly. Stress cones and splices are the weak points of the system and are usuallywhere faults and failures occur. After the medium voltage cables, stress cones, and splices areinstalled, they must be hi-potted (insulation resistance tested) to assure that the installation is


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correct. It is not uncommon to have one or two bad stress cones or splice installations on aproject.

Another common problem in medium voltage distribution systems involving currenttransformers and relays is the cable shield grounding lead. Many electricians mistakenly thinkthe ground leads should not pass through the ground fault relay current transformers. Failure todo so will result in defeating the detection and removal of a cable ground fault. This will causemore equipment damage than normal. The photo #7 below shows the silver cable shieldgrounding leads installed outside of the current transformer. They should pass through thetransformer 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 ordownstream distribution panelboards (See Photo #8). These meters are sometimes networkedtogether 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 / currenttransformers and transformer winding connection. Many times this is not done at the factory, asone would expect. Sometimes the discovery is not made until months after the owner has moved

in. These devices should be commissioned before energizing the equipment. Failure to do somay require an outage after the owner has moved in to fix the problem.


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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 emergencylighting, fire alarm system, smoke control, and other critical systems. Commissioning thecomponents of the emergency distribution system is a must.

Typical problems that we find are as follows:

Incorrect or no ATS controller settings (Photo #10)

Failure of engine start or cool down circuit from the ATS to the generator

Failure of the generator to supply or control power to non-linear loads such as UPS units, labequipment, computers, and solid state lighting ballasts.


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Photo 9 Emergency Generator

Photo 10 Automatic Transfer Switch Controller


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Noisy Distribution Transformers

Dry type distribution transformers are commonly used in many buildings to reduce the voltagefrom 480/277 to 208/120 Volts. Most of the transformer manufacturers have shipping bolts (See

Photo #11) that keep the transformer secure during shipment to the job site, which reducestransportation damage. Many times the electrical contractor fails to loosen these shipping bolts.This causes the transformer to be very noisy and resonate when energized. This is very annoyingfor the building occupants located near the transformer. Commissioning ensures that these boltsare 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 isdone at the main service switchboard or switchgear and on the secondary side of step downdistribution transformer. This is to prevent returning neutral current from splitting and flowing


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

Figure 1 - Correctly Neutral to Ground Bond at Main Panel


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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 groundbond 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 andcause ground fault protection systems to mis-operate. It some cases, it has caused the mainbreaker to trip out, causing a wide spread power outage.

Before energizing the main switchboard, but after the conductors, panelboards, and lighting havebeen installed, an insulation resistance test (megger test) should be performed on the neutralconductor. The test is done by removing the single (legal) neutral to ground bond andmeasuring the resistance between neutral and ground. This measurement should be at least onemegohm. If the value is lower, it usually indicates that the neutral is grounding somewheredownstream. Therefore, one would continue to lift neutral wires from the neutral bus andmeasure the resistance to ground until the grounded neutral is found.

Summary

Although there are many different types of problems and deficiencies that we have foundthroughout the last fifteen years, the items discussed above are the most common problems. Byfocussing on these items, you will uncover many of the problems that will plague your project.


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

Table 2:Common Electrical ProblemsProblem Description SolutionLack of Proper Circuit Breaker Trip Unit andRelay Settings

Specify that contractor must hire a protectionspecialist to perform a Protective Device CoordinationStudy (PDC) and testing company to adjust thebreakers.

Motor HP and Starter Size Problems Mechanical, Electrical design engineer andmanufacturer must coordinate with each other duringdesign phase. Field verify as soon as equipment hasarrived on site

Medium Voltage Distribution System InstallationProblems

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

Switchboard / Panelboard Metering PackagesProblems

Test equipment before energizing

Emergency Distribution Component Problems Test all emergency distribution system components.Then perform a system test by having the generatorusing 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 andmeasure the insulation resistance between neutral andground.

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