Commissioning Low Voltage Distribution Panelboards

Note: The source of the technical material in this volume is the ProfessionalEngineering Development Program (PEDP) of Engineering Services.

Warning: The material contained in this document was developed for SaudiAramco and is intended for the exclusive use of Saudi Aramcosemployees. Any material contained in this document which is notalready 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, EngineeringServices, Saudi Aramco.

Chapter : Electrical For additional information on this subject, contactFile Reference: EEX30107 W. A. Roussel on 874-1320

Engineering EncyclopediaSaudi Aramco DeskTop Standards

Commissioning LowVoltage Distribution Panelboards

Engineering Encyclopedia Electrical

Commissioning Low Voltage Distribution Panelboards

Saudi Aramco DeskTop Standards

Contents Pages

Saudi Aramco Applications And Requirements For LowVoltage Distribution Panelboards.................................................................... 1

Evaluating Low Voltage Distribution Panelboards UponReceipt............................................................................................................ 8

Evaluating Low Voltage Distribution Panelboard InstallationAnd Testing................................................................................................... 11

Work Aid 1: References For Evaluating Low VoltageDistribution Panelboards Upon Receipt........................................................ 15

Work Aid 2: References For Evaluating LowVoltage Distribution Panelboard Installation AndTesting .......................................................................................................... 23

Glossary........................................................................................................ 36



Saudi Aramco DeskTop Standards 1

SAUDI ARAMCO APPLICATIONS AND REQUIREMENTS FOR LOW VOLTAGEDISTRIBUTION PANELBOARDS

A low voltage distribution panelboard is a single panel or group of panel units that is designedfor assembly in the form of a single panel and that has a maximum ac voltage (rms) of 600volts. Common low voltages in Aramco systems are 480/277 V, 208/120 V, and 240/120 V.Panelboards can be installed in a cabinet enclosure or against the exterior of a cabinet, wall, orpartition. Once a panelboard is installed, it is only accessible from the front. A typicalpanelboard contains buses, automatic overcurrent devices, switches, or a combination of thesedevices. A panelboard can contain switches that control lighting circuits, heating circuits, orequipment power distribution circuits. Electric power to panelboards is usually supplied byswitchboards or switchgear.

A low voltage power switchboard is a floor-mounted enclosed switchboard that is rated at4000 amperes or less, that is rated 600 volts or less, and that consists of an enclosure, circuitbreakers (molded case and low-voltage power), fused switches, instruments, metering orcontrol equipment, and associated interconnections and supporting structures. A switchboardis a convenient way to assemble a group of switching devices that receive their power from acommon source. The devices in a switchboard are fed from a common bus, which makesthem convenient to install and modify. Switchboards are different from switchgear, whichcontain individual breakers that are completely segregated (compartmentalized) by groundedmetal barriers that completely enclose all live parts. Switchgear is used for industrialapplications and switchboards are used for less critical non-industrial applications. Inindustrial applications, Saudi Aramco specifies power switchgear ahead of low voltagedistribution panelboards. For Saudi Aramco installations, low voltage distributionpanelboards are used where power switchgear is not applicable.

This section of the Module will provide the following information that pertains to therequirements for Saudi Aramco low voltage distribution panelboard installations:

Applications Classifications and Ratings

Applications

Low voltage distribution panelboards are the "distribution centers" for small, low voltageloads, such as lighting systems, plug-in receptacles, battery chargers, auxiliary aircompressors, and molded-case circuit breaker panels. The National Electrical Code (NEC)divides the application of low voltage panelboards into two general areas: lighting andappliance panels and power distribution panels. Lighting and appliance panels contain morethan ten percent of the installed overcurrent devices that are rated for 30 amperes or less. Theovercurrent devices that comprise the "more than ten percent" of the lighting and appliancepanels should be devices that have a neutral connection.




Low voltage panelboards are used for branch circuit device phase-sequence connection.Phase-sequence connection provides the design personnel with complete circuit arrangementflexibility in the determination of how the loads are connected to the system. To preventunbalanced system voltages, circuit arrangement flexibility allows an even distribution of theloads on the system circuit phases (e.g., phase A, B, C). For example, if a low voltagedistribution panelboard supplies power to three single-phase loads, the loads are eachconnected between a different pair of phases (e.g., phase A and B, B and C, C and D).

Classifications and Ratings

Low voltage distribution panelboards that contain circuit breakers and switches shouldcomply with the requirements of NEMA Standards Publication No. 250-1985, Enclosures forElectrical Equipment (1000 Volts Maximum). To protect the current-carrying parts of apanelboard, motor starter, or controller against unfavorable external conditions, and to protectoperating personnel against contact with these parts, the NEMA standard specifies thefollowing enclosure classifications:

A Type 1 enclosure is a general purpose enclosure that is suitable for normalconditions and that is used indoors. A Type 1 enclosure consists of a sheet metalcase that is primarily intended to protect personnel against accidental contact withenergized electrical equipment. A Type 1 enclosure can be either ventilated ornonventilated. When a Type 1 enclosure is used, specific gasketing materialshould be specified by the manufacturer.

A Type 2 enclosure is a drip-proof enclosure that is suitable for applications inwhich dripping condensation occurs (e.g., cooling rooms, laundries). A Type 2enclosure has the same construction as a Type 1 enclosure, with the addition ofdrip-proof shields (or their equivalent). A Type 2 enclosure can be eitherventilated or nonventilated.

A Type 3 enclosure is a dust-tight and rain-tight enclosure that provides protectionagainst dust and rain outdoors. When a Type 3 enclosure is used, specificgasketing material should be specified by the manufacturer.

A Type 3S enclosure is an enclosure that provides protection against dust and rainoutdoors. A Type 3S enclosure also provides for the operation of externalmechanisms when the enclosure is laden with ice.

A Type 3R enclosure is an enclosure that provides protection against rainoutdoors. A Type 3R enclosure can be either ventilated or nonventilated.




Classifications and Ratings (Cont'd)

A Type 4 enclosure is an indoor or outdoor, dust-tight, and water-tight enclosurethat is designed to meet the NEMA hose test. The NEMA hose test is conductedby subjecting the enclosure to a stream of water, and the amount of water thatenters the enclosure is evaluated.

A Type 4X enclosure is the same as a Type 4 enclosure with the exception that aType 4X is also corrosion resistant.

A Type 5 enclosure is an indoor enclosure that provides protection against settlingairborne particles and dripping liquids.

A Type 6 enclosure is an indoor or outdoor enclosure that provides protectionagainst hose-directed water, temporary submersion in water, and damage from iceformation.

A Type 6P enclosure is the same as a Type 6 enclosure with the exception that aType 6 enclosure is designed for prolonged submersion in water.

A Type 7 enclosure is an indoor enclosure that is used to enclose equipment inClass I hazardous areas.

A Type 8 enclosure is an indoor or outdoor enclosure that is used in Class Ihazardous areas.

A Type 9 enclosure is an indoor enclosure that is used in Class II hazardous areas.A Type 9 enclosure can be either ventilated or nonventilated.

A Type 10 enclosure is an enclosure that is designed to meet the requirements ofthe Mining Enforcement Safety Administration of the U.S. Department of theInterior.

A Type 12 enclosure is an indoor enclosure that is used to provide a degree ofprotection against dust, lint, fiber and flyings, or oil or coolant seepage. A Type12 enclosure can be either ventilated or nonventilated. A Type 12 ventilatedenclosure is not dust-tight.

A Type 12K enclosure is an indoor enclosure with knockout panels that is used toprovide a degree of protection against dust, lint, fiber and flyings, or oil or coolantseepage.





A Type 13 enclosure is an indoor enclosure that is used to provide a degree ofprotection against dust, spraying of water, oil, and/or noncorrosive coolant.Thetype of panelboard enclosure that is selected for an installation is dependent uponthe loads that will be supplied by the panelboard as well as the environmentalconditions at the panelboard location. Indoor and outdoor enclosure applicationcomparisons are provided in Figures 7 and 8 of Work Aid 1.

Low voltage distribution panelboards are required to have a rating that is not less than theminimum feeder capacity that the panelboard will supply to the loads. Panelboards should bemarked by the manufacturer with the voltage and current rating of the panelboard as well asby the number of phases for which the panelboard is designed. The panelboard NEMA-typedesignator, nameplate rating, and design information should be visible on the outside frontportion of the enclosure without having to disturb the interior parts or wiring. A danger signthat indicates the presence of a shock hazard should be clearly visible. If the panelboard has adoor or cover, the NEMA-type designator, nameplate data, and danger sign should be clearlyvisible with the door or cover open. The door or cover should have a method to secure thedoor, such as a latch. A typical low voltage distribution panelboard is shown in Figure 1.

The molded-case breakers that are installed in the panelboard shown in Figure 1 arehorizontally mounted. The positions (e.g., "ON" and "OFF") that indicate the open andclosed positions of the breakers and switches should be clearly marked at the breaker. Theindustry standard for vertically-mounted breakers is that the breaker is closed when it is in the"up" position, and the breaker is open when it is in the "down" position. For horizontally-mounted breakers or switches that are in parallel (as in Figure 1), the closed position istowards the center of the panelboard, and the open position is towards the edges of thepanelboard. Each small molded-case breaker is usually connected to a single phase. Somesingle phase loads require a connection to two of the phases. The single phase load can beisolated through the use of a single breaker or two breakers. When two breakers are used toisolate the load, they should open or close at the same time. To ensure that breakers open andclose at the same time, they are ganged. Ganged breakers have a mechanical connection thatbridges the operating tips of the breakers.




Typical Low Voltage Distribution PanelboardFigure 1





In addition to the required nameplate data markings that have already been described, thepanelboard must also contain, either external to the enclosure or on the inside of theenclosure, the following data:

Any panelboard mounting instructions that are required.

The type of breakers or switches for which the enclosure is suitable.

If the panelboard contains an enclosed circuit breaker or switch that is marked"Suitable for Use as Service Equipment," a "Service Disconnect" marking shouldbe provided. The marking should be provided in the form of a pressure sensitivelabel in an envelope or on a card.

If an insulated neutral that can be grounded is installed in the panelboard, theneutral assembly ampere rating, catalog number, or equivalent identificationshould be provided.

Any additional shock hazard, burn, or rotating equipment warning informationshould be prominently displayed on the outside of the panelboard or on the insidedoor or cover.

For panelboards that enclose circuits that use a circuit neutral, the neutral assembly that is in,or for use in, the panelboard must have an ampacity that is equal to the highest ampere ratingof the circuit breakers that will be used in the panelboard.

When a panelboard contains molded-case breakers or switches, the breakers or switches arealso required to be marked with nameplate data. The nameplate data must be marked on themolded case of the breaker, on the switch, or on an attached plate. Molded-case breaker orswitch nameplate data must be located in a place where it is both visible and legible. Eachmolded-case breaker or switch must be marked in a durable manner with the following data:

The manufacturer's name or trademark.

The breaker or switch type designation or identification number.

The words "Molded Case Switch" and "No Overcurrent Protection," as applicable.





The rated current and rated operational voltage.

The indication of a required barrier (if the proper operations or installation of thebreaker or switch is dependent upon an insulation barrier).

The words "ON" and "OFF" to indicate the closed and open positions at the placeof operation. If symbols are used, "I" and "O" must be used to indicate the closedand open position, respectively.

The rated short-time withstand currents (if applicable).

Any molded case breaker or switch that is provided with an accessory or accessories must bemarked to include the type of the accessory, the proper connections for the accessory (if theconnections are not obvious), and the electrical ratings of the accessory. If any specializedapplication information or limitations are required for the operation of the breaker or switch,these data must be marked on the switch, as applicable.




EVALUATING LOW VOLTAGE DISTRIBUTION PANELBOARDS UPONRECEIPT

When low voltage distribution panelboards are ordered from the manufacturer or vendor,certain specifications must be met. The Saudi Aramco Electrical Design Engineer shouldmake a determination as to what panelboard specifications (e.g., size, type, rating) arenecessary for the installation through use of the correct Saudi Aramco installationrequirements for low voltage distribution panelboards. When the panelboard is ordered, thepanelboard specification information is then supplied to the manufacturer or the vendor.When the low voltage distribution panelboard shipment is received from the manufacturer orvendor, the Electrical Engineer should evaluate the panelboard shipment for compliance withthe specifications that were provided with the original order. The Electrical Engineer shouldalso evaluate the delivered low voltage distribution panelboard for any physical damage thatoccurred during the shipment from the manufacturer or the vendor.

This section provides information on the following topics that are pertinent to evaluating lowvoltage distribution panelboards upon receipt:

Physical Inspection Verification Against Specification

Physical Inspection

Prior to the acceptance of a low voltage distribution panelboard shipment, the ElectricalEngineer should inspect the panelboard. A proper and thorough inspection of the panelboardfor applicability, compliance with Saudi Aramco installation requirements, and physicaldamage prior to the installation can save cost-overruns that are associated with theinstallation. The installation of an improper, underrated, or damaged panelboard can wastemoney and resources by causing subsequent system damage or by requiring the frequentmaintenance, repair, or replacement of the panelboard.

A low voltage distribution panelboard physical inspection procedure is provided in Work Aid1. During the physical inspection, the inspector should, at a minimum, check the ratings ofthe switches and breakers, inspect for the presence of contaminants (e.g., dirt, moisture),examine switches and molded-case breakers for cracks, and check for loose connections. Ifany problems exist, or if variations from the installation diagrams or drawings are noted, theyshould be promptly corrected or investigated. The panelboard should completely enclose allbreaker or switch current-carrying parts and should be constructed of materials that arecorrosion resistant and strong and rigid enough to retain its shape during normal operation.Panelboard covers or access holes should fit properly, and doors should close tightlythroughout the useful life of the panelboard. A door or cover that allows access to the interiorof the panelboard should be fastened by screws or with a latch that can be locked.




Physical Inspection (Contd.)

When a panelboard is energized, voltage potentials will be present. To prevent line-to-line orline-to-ground shorts that could cause subsequent equipment damage, Saudi Aramco hasminimum spacing requirements that should be met between live parts and from live parts toground in enclosures. Both UL 67 (Panelboards) and AB 1 (Molded Case Circuit Breakersand Switches) contain minimum clearances and creepage distances for electrical installation.A table of minimum spacings is provided in Figure 9 of Work Aid 1. In the table of minimumspacing, the spacing is measured between the bare portions of insulated conductors. Toprevent wire deformation, terminal connection damage during installation, and line-to-line orline-to-ground shorts that could cause subsequent equipment damage, the wire-bending spacebetween a wire connector or lug should be above a specified minimum value. The minimumdistance between the end of any wire connector or lug and the wall of the panelboardenclosure toward which the conductor is directed or through which the connected conductormay normally pass is provided in Figure 10 of Work Aid 1.

Verification Against Specification

The specifications of the panelboard should have already have been determined by the designteam before the low voltage distribution panelboard is received from the manufacturer or thevendor. Although the specifications for the panelboard have already been determined, theElectrical Engineer should still be familiar with the requirements for panelboard installations.The Electrical Engineer should verify that the data that appear on the nameplate (or label) ofthe panelboard that was received match the specifications of the panelboard that was ordered.Each Electrical Engineer who is associated with any phase of an installation is part of theoverall quality control process. The installation team could uncover installation design errors,manufacturing flaws, or installation conflicts that did not exist during the installation designphase. Careful vigilance and a familiarity with the requirements for Saudi Aramcopanelboard installations are necessary for the proper verification of a panelboard installationagainst the installation specifications.

As part of the receipt evaluation of low voltage distribution panelboard evaluation, theElectrical Engineer should also check that the panelboard that was received is in compliancewith the installation blueprints and installation design documents. In some cases, thedetermination is conducted by reading an electrical plan that has the panelboard type and sizeidentified. Then, the Engineer only has to inspect the manufacturer's marking on thepanelboard and compare them to what is required on the electrical plan to determine whetherthe correct panelboard is being used. In other situations, the Electrical Engineer must rely onhis knowledge of the correct application of panelboard types and sizes, and then determinewhether the correct panelboard is being used. Panelboards are usually assembled with allcomponents (e.g., switches, molded-case circuit breakers) already installed, so that when thepanelboard is received, all that is necessary is to connect up the power supply and the loads.Because panelboards usually come assembled, the inspection should encompass thepanelboard and all of the components that are contained in the panelboard.




Verification Against Specification (Cont'd)

To ensure overall quality control for the low voltage distribution panelboard installation, theElectrical Engineer should also be familiar with the technical requirements for Saudi Aramcopanelboard installations. Generally, the verification against specification is conductedthrough determination of whether the panelboard type and rating to be installed match thepanelboard type and rating that are required for the installation. If any doubt exists as towhether a received panelboard meets the technical requirements for Saudi Aramcoinstallations, the technical requirement publications should be referenced. Saudi Aramco usesthe following publications for panelboard installations:

NEMA Standard AB-1, "Molded Case Circuit Breakers and Switches." Thisstandard is the reference for breakers and switches that are housed in an enclosurethat is rated for voltages up to, and including, 1000 Vac and 1200 Vdc. Thestandard also covers any accessories that are associated with the enclosure.

NEMA Standard 250-1991, "Enclosures for Electrical Equipment (1000 VoltsMaximum)." This standard covers the classification and description of enclosuresfor electrical equipment.

SAES-P-104, "Wiring Methods and Materials." This standard contains theminimum mandatory requirements for the design and installation of wiring andcable systems standard. Overhead distribution systems are not included in this.




EVALUATING LOW VOLTAGE DISTRIBUTION PANELBOARD INSTALLATIONAND TESTING

After the verification of the low voltage distribution panelboard against the requiredspecifications of the installation is complete, the low voltage distribution panelboard isinstalled and tested. Prior to commissioning, the low voltage distribution panelboardinstallation should be evaluated for compliance with Saudi Aramco installation requirements,and the test results should be evaluated.

The evaluation of the low voltage distribution panelboard installation for compliance withSaudi Aramco installation requirements is performed through conduct of a visual inspectionof the panelboard installation and all of the components that are contained in the panelboard.During the inspection, the Electrical Engineer should pay particular attention to thepanelboard and enclosed equipment labeling, grounds, feeder conductors, and connections.In addition to the visual inspection, tests should be performed to ensure that contact resistanceis low, that insulation resistance is high, and that the installation meets system overcurrentrequirements.

This section provides information on the following topics that are pertinent to evaluating lowvoltage distribution panelboard installation and testing:

Labeling/Indexing Grounding Connection Inspection Rating Check (42 kA) Switchgear Feed Insulation Resistance (Megger) Test Contact Resistance Check Overcurrent Test

Labeling/Indexing

During the inspection and evaluation, the Electrical Engineer should inspect the labeling andindexing of all conductors, connections, and terminations at the panelboard for compliancewith Saudi Aramco and industry specifications. The inspection is performed through a visualcheck of the labels and indexes on the conductors that are used in the panelboard.

A conductor is labeled by its color and the markings on the cable. Conductors that areintended for use as ungrounded current-carrying conductors (single or multiple-conductorcables) should be distinguished through use of colors other than white, natural, grey, or green.Conductors that are intended for use as ungrounded current-carrying conductors can also beidentified through use of a combination of colors or by the addition of a distinguishing mark.Individual phase conductors of a three-phase system should be color coded or otherwisepermanently and individually identified throughout their length. All low voltage cables (1000volts, or less) should be marked in accordance with ANSI/NFPA-70 Article 310.




Labeling/Indexing (Cont'd)

Cable labeling information that is required for low voltage distribution panelboards isprovided in Work Aid 2. Examples of the type of information that is required are themaximum working voltage for which the conductor was tested or approved, the letterdesignation for the type of cable and insulation, the manufacturer's name, trademark, or otherdistinctive marking to identify the cable, the sq mm size of the cable, and the number ofconductors in the cable (if a multiple-conductor cable is used). Cable labeling information isprovided at periodic intervals on the side of the cable.

Because the labeling information appears on the cables at periodic intervals, the labelinginformation may not appear near to the panelboard as a result of where the cable or wire wascut. To ensure that installation and maintenance personnel can correctly identify a wire orcable, the cable end at the panelboard should also be marked with approved labels or tags.Cable labeling and marking requirements are provided in Work Aid 2. The cable end shouldbe marked at the outside of the panelboard where it is clearly visible and at the terminationpoints (e.g., terminal block, breaker) inside the panelboard. The cable end label or tag shouldindicate the phase ("A" "B" or "C") on single conductor cables, the circuit voltage (480 V, 2.4kV etc.). For power cables, the label or tag should indicate the conductor number and size (3-250 MCM, 3-No.4 AWG, etc.) and the cable identification index number (from constructiondrawings). Wiring at terminal blocks is identified through the use of permanently embossedheat-shrinkable or slip-on-type wire markers. Wrap-around, rigid snap-on, or adhesive-typemarkers are not permitted at terminal blocks.

The cable identification index number is provided as a reference to a blueprint or circuitdiagram. The cable identification index number should indicate where the cable is beingrouted from and where it is being routed to. During the evaluation of the low voltagedistribution panelboard, the Electrical Engineer should visually check that the index numberthat appears on the label (or tag) at the termination of the wire or cable correctly matches thecorresponding number on the blueprint or circuit diagram.

Ground Connection Inspection

The installation of a ground is critical to the proper and safe operation of an electrical powerdistribution system. There should be a connection to ground for the panelboard enclosure, aswell as an electrical system neutral ground (if the system requires one) inside the panelboard.When the inspection of a panelboard ground is performed, the Electrical Engineer should lookfor evidence of incorrect connections, terminations, or fittings. The Electrical Engineershould also assess compliance with the cognizant Saudi Aramco or industry grounding systemstandards. Ground connection inspection items are provided in Work Aid 2.




Rating Check (42 kA)

For Saudi Aramco wire and cable installations, any power distribution bus should be rated fora minimum continuous current rating of 600 A, and all phase, neutral, and ground bussesshould be able to withstand 42 kA rms symmetrical fault amperes. A low voltage distributionpanelboard can be used as a load center and can be considered as being a distribution bus.The current interrupting capability of the main breaker that supplies the panelboard and allcurrent-carrying equipment that is connected to the panelboard should have a 42 kA minimumcurrent rating. The rating check should be performed by the Electrical Engineer during thevisual inspection of the low voltage distribution panelboard. The rating should be included inthe nameplate data.

Switchgear Feed

Because a low voltage distribution panelboard supplies power to equipment, the cable thatfeeds power to the panelboard should be the correct size for the installation and should beconnected to the panelboard to provide the proper phase rotation. The Electrical Engineershould compare the switchgear feeder cable size and type with the installation blueprints ordrawings to ensure that the feeder can handle the maximum continuous and fault currents thatcould arise at the panelboard. During the operational checks of the power that is supplied bythe distribution system, a rotational check should also be performed on each connected pieceof rotating equipment to ensure that rotation occurs in the proper direction.

Insulation Resistance (Megger) Test

The purpose of the megohmmeter test is to directly measure the low voltage distributionpanelboard insulation resistance with a megger. To conduct the megohmmeter test, themegger is connected between two of the panelboard phases, and the megger is operated forone minute. The test is performed at the main incoming voltage side and at the downstreamside of each switch, breaker, or disconnect that is enclosed in the panelboard. Electrical testreference information for the insulation resistance (megger) test is provided in the SaudiAramco Pre-Commissioning Form Testing Guide Lines, P-000 (see Figure 11 of Work Aid2). This form is obtained from the Instrumentation Unit of the Consulting ServicesDepartment. The electrical test reference information provides the recommendedmegohmmeter test voltages for various voltage ranges. Similar megger readings are takenbetween each remaining phase pair combination and from each phase to ground.

The Electrical Engineer should evaluate the insulation resistance (megger) test values toensure that the insulation resistance values that were recorded are greater than themanufacturer's minimum values. If the manufacturer's minimum values are not provided, thevalue of the insulation resistance should be greater than the rated voltage + 1 kV in megohms.For instance, a 600 V rated system should have an insulation resistance that is greater than 1.6megohms. Any value of insulation resistance that is below the minimum specificationsshould be investigated by the Electrical Engineer who is performing the test data evaluation.




Insulation Resistance (Megger) Test (Cont'd)

Amplifying instructions for additional megger testing (e.g., dielectric absorption ratios) areprovided in Work Aid 2.

Contact Resistance Test

The electric power distribution system is designed to deliver electric power from the source tothe loads with a minimum power loss. The resistance of switch, breaker, or disconnectcontacts that are installed in a low voltage distribution panelboard should be extremely lowwhen the contacts are closed and extremely high when the contacts are open. The contactresistance test is conducted through measurement of the circuit continuity across the switch,breaker, or disconnect contacts with a micro-ohmmeter. Switch, breaker, or disconnectcontacts should have a resistance value of less than 200 micro-ohms across them when theyare closed. Electrical test reference information for the insulation contact resistance test isprovided in the Saudi Aramco Pre-Commissioning Form Testing Guide Lines, P-000.

Overcurrent Test

Overcurrent tests are performed on breakers that are installed in low voltage distributionpanelboards that have overcurrent trip settings. The type of overcurrent test that is performedis dependent on the type and rating of the breaker that is installed in the panelboard. Toperform an overcurrent test, a current injection test set (Multiamp MS2 or equivalent) isconnected across the line, and load terminals of one pole of the circuit breaker and a testcurrent are applied. The overcurrent test is intended to verify that the trip systems of thebreaker operate in accordance with the marked trip settings on the breaker nameplate. Triptests are performed in one of two ways: an instantaneous value of current is injected at thebreaker and the trip time is determined, or the rated current is injected and the breakerperformance is monitored. Because high fault current can have disastrous results, andbecause it is imperative that the breaker trip properly, the instantaneous trip test is the mostimportant. Manufacturer's preset values are tested and logged. The overcurrent trip testvalues and tolerances for successful overcurrent trip tests are provided in Figures 13 and 14 ofWork Aid2.




WORK AID 1: REFERENCES FOR EVALUATING LOW VOLTAGEDISTRIBUTION PANELBOARDS UPON RECEIPT

Low Voltage Distribution Panelboard Enclosure General Use

Circuit breaker and switch low voltage panelboard enclosures should comply with therequirements of NEMA Standards Publication No. 250-1985, Enclosures for ElectricalEquipment (1000 Volts Maximum). For Saudi Aramco low voltage distribution panelboardinstallations, ventilated enclosures are permitted for circuit breaker frame sizes that are ratedfor 400 amperes or more. Figure 5 shows the types of enclosures that are used in SaudiAramco power distribution installations:




WORK AID 1 (Cont'd)

Enclosure Application TypesEnclosure

TypeUse Location

Type 1 A general purpose enclosure that is suitable for normal conditions. IndoorsType 2 A drip-proof enclosure that is suitable for dripping conditions. IndoorsType 3 A dust-tight and rain-tight enclosure. OutdoorsType 3S A dust-tight and rain-tight enclosure that allows external mechanisms to

operate with laden ice.Outdoors

Type 3R A rainproof enclosure. OutdoorsType 4 A water-tight and dust-tight enclosure that is designed to meet the hose test

(see NEMA ICS 6-110.56).Both

Type 4X A water-tight, dust-tight, and corrosion resistant enclosure that is designed tomeet the hose test (see NEMA ICS 6-110.56).

Both

Type 5 An enclosure that protects against settling airborne particles and drippingliquids.

Indoors

Type 6 A submersible, water-tight, and dust-tight enclosure. BothType 6P A prolonged-submersion, submersible, water-tight, and dust-tight enclosure. BothType 7 An enclosure that is suitable for most Class I hazardous locations. IndoorsType 8 An enclosure that is suitable for Class I hazardous locations. BothType 9 An air-break equipment enclosure that is suitable for Class II hazardous

locations.Indoors

Type 10 An enclosure that is suitable for coal mines. IndoorsType 12 A dust-tight and drip-tight enclosure that is designed to be used in industrial

applications.Indoors

Type 12K A dust-tight and drip-tight enclosure with knockout panels that is designed tobe used in industrial applications.

Indoors

Type 13 An oil-tight and dust-tight enclosure that is used primarily to house pilotdevices.

Indoors

NOTE: Type 1, 2, 3R, 9, and 12 enclosures may be either ventilated or non-ventilated. Type 3, 4, 4X, 6, 7, 8, 10, 11, and13 are nonventilated-type enclosures. Type 12 ventilated enclosures are not dust tight. For the use of enclosureTypes 1 and 3, specific gasketing material should be specified by the manufacturer.

Enclosure Application TypesFigure 5




WORK AID 1 (Cont'd)

Comparisons for specific applications of indoor and outdoor enclosures are shown in Figures6 and 7.

Provides a Degree of Protection Againstthe Following Environmental Conditions

Types of Enclosures

1*

2*

4 4X 5 6 6P 12 12K 13

Incidental contact with the enclosed equipment X X X X X X X X X XFalling dirt X X X X X X X X X XFalling liquids and light splashing --- X X X X X X X X XCirculating dust, lint, fibers, and flyings** --- --- X X --- X X X X XSettling airborne dust, lint, fibers, and flyings** --- --- X X X X X X X XHosedown and splashing water --- --- X X --- X X --- --- ---Oil and coolant seepage --- --- --- --- --- --- --- X X XOil or coolant spraying and splashing --- --- --- --- --- --- --- --- --- XCorrosive agents --- --- --- X --- --- X --- --- ---Occasional temporary submersion --- --- --- --- --- X X --- --- ---Occasional prolonged submersion --- --- --- --- --- --- X --- --- ---

* These enclosures may be ventilated. However, Type 1 may not provide protection against smallparticles of falling dirt when ventilation is provided in the enclosure top. Consult the manufacturer.

** These fibers and flying are nonhazardous materials and are not considered the Class III type ignitablefibers or combustible flyings. For Class III type ignitable fibers or combustible flyings see theNational Electrical Code, Article 500.

Comparison of Specific Applications of Enclosures for Indoor Nonhazardous LocationsFigure 6




WORK AID 1 (Cont'd)

Provides a Degree of Protection Againstthe Following Environmental Conditions

Types of Enclosures

3 3R*** 3S 4 4X 6 6PIncidental contact with the enclosed equipment X X X X X X XRain, snow, and sleet* X X X X X X XSleet** --- --- X --- --- --- ---Windblown dust X --- X X X X XHosedown --- --- --- X X X XCorrosive agents --- --- --- --- X --- XOccasional temporary submersion --- --- --- --- --- X XOccasional prolonged submersion --- --- --- --- --- --- X

* External operating mechanisms are not required to be operable when the enclosure is ice covered.

** External operating mechanisms are operable when the enclosure is ice covered.

*** These enclosures may be ventilated.

Comparison of Specific Applications of Enclosures for Outdoor Nonhazardous LocationsFigure 7




Procedure for Panelboard Enclosure Inspection

The following procedure should be followed to perform an inspection of a low voltagedistribution panelboard. The inspection is performed to evaluate the operating panelboardenvironment, the panelboard condition, the condition of all equipment that is contained in thepanelboard (e.g., molded-case circuit breakers), and to determine whether any physicaldamage to the panelboard has occurred. If, for any reason, electric power could be suppliedto the panelboard, ensure that the electric power is removed. Hazardous voltages in electricalequipment can cause severe personal injury or death. Turn off the panelboard power supplybefore any of the following inspections are performed.

1. Verify that the panelboard is of the correct type and rating for the installation inaccordance with installation diagrams and drawings.

2. Turn "OFF" all power to the panelboard to electrically isolate it from other circuits.

3. Turn off all switches and/or breakers in the panelboard.

4. Open the enclosure. Verify that there is no voltage on any incoming conductors andbetween those conductors and ground to positively determine that the equipment isdeenergized. Proper Saudi Aramco practices and procedures should be followed whenthe verification is performed.

5. Verify that any switches and/or breakers that are installed in the panelboard have thecorrect ratings for the installation in accordance with installation diagrams anddrawings.

6. Examine the interior of the panelboard for the presence of dirt, dust, soot, grease, ormoisture.

7. Examine all switches and molded-case circuit breaker cases for cracks.

8. Verify that the conductors are of the correct size and type for the application inaccordance with the installation diagrams and drawings.

9. Verify that the wiring at the circuit breaker terminal is identified correctly inaccordance with the installation diagrams and drawings. Wiring identification at theterminals of the circuit breaker should be permanently embossed wire markers of theheat-shrinkable or slip-on type. Wrap-around, rigid snap-on, or adhesive-type markersare not permitted.

10. Visually check all electrical connections to be certain that the connections are cleanand secure. There should be no evidence of looseness at any electrical connection.




WORK AID 1 (Cont'd)

Minimum Panelboard Spacing Requirements

To prevent line-to-line or line-to-ground shorts that could cause subsequent equipmentdamage, Saudi Aramco has minimum spacing requirements that should be met between liveparts and from live parts to ground in enclosures. Both UL 67 (Panelboards) and AB 1(Molded Case Circuit Breakers and Switches) contain minimum clearances and creepagedistances for installation. Figures 8 and 9 contain excerpts from AB 1 that provide minimumspacings between the bare portions of insulated conductors and between conductors andground as well as the minimum distance between the end of any wire connector or lug and thewall of the panelboard enclosure.

Minimum Spacing in (MM) InchesAt Terminals Other Than at Terminals

Between Terminals ofOpposite Polarity

Between Terminalsand Any Ground

Metal*

BetweenUninsulated LiveParts of Opposite

Polarity

Between Uninsulated Live Parts and AnyGround Metal*

Voltage A B C D** EBetwee

nParts

ThroughAir

OverSurface

ThroughAir

OverSurface

ThroughAir

OverSurface

ThroughAir

OverSurface

ThroughAir

OverSurface

0-125126-300301-600

1/2 (12.7)3/4 (19.05)1 (25.4)

3/4 (19.05)1 1/4(31.75)2 (50.8)

1/2 (12.7)1/2 (12.7)1/2 (12.7)

1/2 (12.7)1/2 (12.7)1/2 (25.4)

1/4 (63.5)1/4 (6.35)3/8 (9.52)

3/8 (9.52)3/8 (9.52)1/2 (12.7)

1/2 (12.7)1/2 (12.7)1/2 (12.7)

1/2 (12.7)1/2 (12.7)1/2 (25.4)

1/4 (63.5)1/4 (6.35)3/8 (9.52)

3/8 (9.52)3/8 (9.52)1/2 (12.7)

* The spacing to the enclosure or circuit breaker mounting means is permitted to be reduced if anacceptable liner of insulating material, not less than 1/32 inch in thickness, is used to provide the requiredspacing through air.

** If indentation or deformation of the overall enclosure or circuit breaker mounting means might reducespacings to less than those indicated in Column E.

If indentation or deformation of the overall enclosure or circuit breaker mounting means will not affectspacings.

Minimum Panelboard Enclosure Equipment Spacings (from AB 1 - 1986)Figure 8




WORK AID 1 (Cont'd)




Minimum Wire-Bending SpaceFigure 9




WORK AID 2: REFERENCES FOR EVALUATING LOW VOLTAGEDISTRIBUTION PANELBOARD INSTALLATION AND TESTING

Low Voltage Panelboard Labeling/Indexing

The following enclosure markings are required to be provided (in a durable manner) directlyon a panelboard, on a nameplate that is attached to the exterior of the panelboard cover, or onthe inside of the panelboard:

The manufacturer's name or trademark. The type designation and/or identification number. The maximum rated operational voltage. The maximum rated current of the frame size Some manner of indicating switch or breaker position (open or closed). The appropriate electric shock hazard warning signs. Other amplifying warnings as deemed necessary for the installation.

If a panelboard contains a switch or a circuit breaker, the following marking(s) are required tobe provided (in a visible and legible manner) on a switch or circuit breaker itself or on anameplate or nameplates that are attached to the switch or circuit breaker:

The manufacturer's name or trademark.

The type of designation or identification number.

The rated current.

The rated operational voltages with corresponding rated short-circuitbreaking capacities. (For circuit breakers that are rated 240 voltsmaximum with short circuit breaking capacities of 5000 amperes, theshort circuit breaking capacity can be omitted.)

The indication of a required barrier (if the proper operations orinstallation is dependent upon an insulation barrier).

The "LINE" side and the "LOAD" side of the breaker or switch if it isan interchangeable trip circuit breaker or if it is not suitable for reverseconnection.

Indication of the "ON" and "OFF" position.

Rated short-time withstand currents (if applicable).




WORK AID 2 (Cont'd)

A circuit breaker that is provided with an accessory or accessories should be marked toinclude the type, proper connections (if not obvious), and the electrical ratings of theaccessories.

Any additional specialized applications information or limitations should be marked on thebreaker as applicable.

Cable labeling information that is required for low voltage distribution panelboards is asfollows:

The maximum working voltage for which the conductor was tested orapproved.

The proper letter designation for the type of cable and insulation (e.g.,EPR, XLPE, TC, THWN, CONTROL).

The manufacturer's name, trademark, or other distinctive marking alongwith the year that the panelboard was manufactured.

The sq mm (AWG of MCM) size and number of conductors if multiple-conductor cable (e.g., 150 sq mm, 250 MCM, 18 AWG) and"COMPACTED" if such construction is used.

On multiple-conductor power cables, each phase should bedistinguished by labeling "PHASE A," "PHASE B," or "PHASE C," or,if labeling is not feasible, the phases should be distinguished by black,red, or blue helically applied polyester ribbons or tapes or by some otherreadily identifiable means.

All power cables that are installed in a panelboard should be durably marked at the end of thepanelboard with approved labels or tags that indicate the following information (if theinformation is not already available from any color coding or surface marking):

The phase "A," "B," or "C" on single conductor cables.

The circuit voltage (480 V, 2.4 kV etc.) for power cables.

The conductor number and size (3-250 MCM, 3-No.4 AWG, etc.) if it isnot shown on cable jacket.

The cable identification number (from construction drawings).




WORK AID 2 (Cont'd)

The abbreviated information that should be provided on cables is as follows:

The number of conductors. The size of each conductor. The voltage class. The type of insulation. The type of armoring (if any). The type of jacket (if any).

The number of conductors or conductor pairs within a cable should be abbreviated as 1/C forone conductor, 3/C for three conductors, 12/C for twelve conductors, or 25 pair for 25 pairs ofconductors.

The size of the conductor or conductors should be expressed in sq mm (MCM or AWG) sizes.The AWG letters for the prefix symbol # (e.g., #2 for No. 2 AWG conductor) should not beused.

The voltage class of the cable as given by the manufacturer or as required by the designshould be used (e.g., 600 V, 1 kV, 5 kV, 15 kV, etc.).

Conductor insulation is described by type letters that are derived from NEC Tables 310-13,310-61, 400-4, or 402-3. Example abbreviations for various insulation types are as follows:

PVC - polyvinyl chloride. EPR - ethylene propylene rubber. XLPE - crosslinked polyethylene. PE - polyethylene.

For example, a cable label that reads "8 - 6 sq mm (no. 10) THWN" describes a group ofeight, 6 sq mm, (# 10) AWG, single conductors that have Type THWN insulation.




WORK AID 2 (Cont'd)

Panelboard Grounding

A low voltage distribution panelboard ground connection is inspected for the following:

Insulated conductors of 16 sq mm (No.6 AWG) or smaller that areintended for use as grounded or neutral conductors should have an outerfinish of a white or natural grey color.

Insulated conductors that are larger than 16 sq mm (No.6 AWG) andthat are intended for use as grounded or neutral conductors should havean outer finish of a white or natural grey color or should have adistinctive white marking at their terminations.

An insulated conductor that is larger than 16 sq mm (No.6 AWG) isidentified as a grounding conductor at each end and at every pointwhere the conductor is accessible through performance of one of thefollowing:

- Strip the insulation from the entire exposed length of the grounding wire.

- Color the exposed insulation green.

- Mark the exposed insulation with green colored tape or green colored adhesive labels.

Panelboard Testing

This section contains information that is pertinent to the testing and evaluation of low voltagedistribution panelboards.

Saudi Aramco Pre-Commissioning Form P-000, Testing Guide Lines (Obtained from InstrumentationUnit, Consulting Services Department)

Figure 10 shows the Saudi Aramco Pre-Commissioning Testing Guide Lines form. The SaudiAramco Pre-Commissioning Testing Guide Lines form provides electrical test referenceinformation for the installation of various systems and support equipment. The Testing GuideLines form also provides standard bolt torque values for various sized bolts.




Saudi Aramco Pre-Commissioning Form, P-000,Testing Guide Lines

Figure 10




Saudi Aramco Pre-Commissioning Form, P-000, Testing Guide LinesFigure 10 (Cont'd)




Saudi Aramco Pre-Commissioning Form, P-000,Testing Guide LinesFigure 10 (Cont'd)




WORK AID 2 (Cont'd)

Information, Formulas, and Tables for Use in Evaluating the Results of Megger Tests

The following 60-second megger tests are conducted for low voltage distribution panelboardcommissioning:

Phase-to-Phase Phase-to-Ground

If additional megger test data are required, a dielectric absorption ratio megger test can beperformed.

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

Figure 11 provides insulation conditions for 60/30 second ratio results (if recorded) and for10/1 minute ratio results.

InsulationCondition

60/30 - SecondRatio

10/1 - Minute Ratio(Polarization Index)

Dangerous

Questionable(Perform investigation)

Good

Excellent

---

1.0 to 1.25

1.4 to 1.6

Above 1.6

Less than 1

1.0 to 2

2 to 4

Above 4

Dielectric Absorption Ratio ChartFigure 11




WORK AID 2 (Cont'd)

Overcurrent Trip Test

Figures 12 and 13 provide the overcurrent trip test values and tolerances for breakers that areinstalled in and that supply power to low voltage distribution panelboards.

BreakerVoltage

Volts

Range of RatedContinuous

CurrentAmperes

MaximumTrip Time

In Seconds*240240600600240240600600600600600600

15-4550-10015-45

50-100110-225250-400110-225250-400450-600

700-12001400-25003000-5000

507070

125200300250300350500600650

* For integrally-fused circuit breakers, trip times may besubstantially longer if tested with the fuses replaced by solidlinks (shorting bars).

Consult the manufacturer if additional information is required.

Values for Overcurrent Trip TestFigure 12




WORK AID 2 (Cont'd)

Tolerances ofHigh and Low Settings

Frame Size,Amperes Hi Lo

250 FACTORY 20% 25%

FIELD +40%-25%

+40%-30%

400 FACTORY 20% 25%

FIELD 25% 30%

Instantaneous Trip Setting TolerancesFigure 13




GLOSSARY

ampacity The current in amperes that a conductor can carry continuously undernormal operating conditions without exceeding its temperature rating.

current rating Specified by the manufacturer, part of the equipment nameplate rating.

equipment ground A ground connection to noncurrent-carrying metal parts of a wiringinstallation or of electric equipment or both.

EPR Ethylene propylene rubber insulated general purpose cable.

feeder busway A busway that is used to transmit large amounts of power betweenequipment, such as transformers and switchgear.

power cable A conductor or a group of conductors that supply current for the properoperation of a machine, apparatus, or system during start-up, normaloperation, and transient conditions.

THHN/THWN PVC insulated, nylon-jacketed, single-conductor cable that can be usedfor either power or control installations.

THW PVC-insulated, single-conductor, general purpose cable.

XLPE Cross-linked polyethylene, insulated, general purpose cable.

Commissioning Low Voltage Distribution Panelboards

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