Commissioning Low Voltage Distribution Panelboards

Engineering Encyclopedia Saudi Aramco DeskTop Standards

Commissioning Low Voltage Distribution Panelboards

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

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

Chapter : El Electrical File Reference: EEX30107

For additional information on this subject, contact W . A . R ou ssel o n 87 4-13 2 0

Engineering Encyclopedia

Electrical Commissioning Low Voltage Distribution Panelboards

C o n t e n ts

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Saudi Aramco Applications And Requirements For Low Voltage Distribution Panelboards............................................................ Panelboards.................................................................... ........ 1 Evaluating Low Voltage Distribution Panelboards Upon Receipt ............................................... ......................................................................... ................................................ ................................... ............. 8 Evaluating Low Voltage Distribution Panelboard Installation And Testing ................................................ .......................................................................... ................................................... ......................... 11 Work Aid 1: References For Evaluating Low Voltage Distribution Panelboards Upon Receipt ............................................... ........................................................ ......... 15 Work Aid 2: References For Evaluating Low Voltage Distribution Panelboard Installation And Testing ............................................... ......................................................................... ................................................ ................................. ........... 23 Glossary Glossa ry................... ............................................. .................................................... ................................................ ................................. ........... 36

Saudi Aramco DeskTop Standards



SAUDI ARAMCO APPLICATIONS AND REQUIREMENTS FOR LOW VOLTAGE DISTRIBUTION PANELBOARDS A low voltage distribution panelboard is a single panel or group of panel units that is designed for assembly in the form of a single panel and that has a maximum ac voltage (rms) of 600 volts. 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, or partition. partitio n. Once a panelboard pane lboard is installed, installe d, it is only accessible acce ssible from the front. A typical typica l panelboa pane lboard rd contains co ntains buses, buses , automati au tomaticc overcurr ov ercurrent ent device d evices, s, switches sw itches,, or a combin co mbination ation of these th ese devices. A panelboard can contain switches that control lighting lighting circuits, heating circuits, or equipment power distribution circuits. circuits. Electric power to panelboards is usually supplied by switchboards or switchgear. A low voltage power switchboard is a floor-mounted enclosed switchboard that is rated at 4000 amperes or less, that is rated 600 volts or less, and that consists of an enclosure, circuit breakers break ers (molded (mold ed case and low-voltage low-v oltage power), powe r), fused switches, switch es, instruments, instrum ents, metering meteri ng or control equipment, and associated interconnections and supporting structures. A switchboard is a convenient way to assemble a group of switching devices that receive their power from a common source. The devices in a switchboard are fed from a common bus, which makes them convenient to install and modify. Switchboards are different different from switchgear, which contain individual breakers that are completely segregated (compartmentalized) by grounded metal barriers that completely enclose all live parts. Switchgear is used for industrial applications and switchboards are used for less critical non-industrial applications. applications. In industrial applications, Saudi Aramco specifies power switchgear ahead of low voltage distribution panelboards. For Saudi Aramco installations, low voltage distribution panelboa pane lboards rds are used where wher e power pow er switchge swi tchgear ar is not n ot applica ap plicable. ble. This section of the Module will provide the following information that pertains to the requirements for Saudi Aramco low voltage distribution panelboard installations: • •

Applications Clas Classi sifficat cations ions and and Rati Rating ngss

Applications Low voltage distribution panelboards are the "distribution centers" for small, low voltage loads, such as lighting systems, plug-in receptacles, battery chargers, auxiliary air compressors, and molded-case circuit breaker panels. The National Electrical Electrical Code (NEC) (NEC) divides the application of low voltage panelboards into two general areas: lighting and appliance panels and power distribution distribution panels. Lighting and appliance panels contain more than ten percent of the installed installed overcurrent devices that are rated rated for 30 amperes or less. less. The overcurrent devices that comprise the "more than ten percent" of the lighting and appliance panels pane ls should sho uld be b e devices de vices that have h ave a neutral ne utral conne c onnection. ction.


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Low voltage panelboards are used for branch circuit device phase-sequence connection. Phase-sequence connection provides the design personnel with complete circuit arrangement flexibility in the determination of how the loads are connected to the system. To prevent unbalanced system voltages, circuit arrangement flexibility allows an even distribution of the loads on the system circuit phases (e.g., phase A, B, C). For example, if a low voltage distribution panelboard supplies power to three single-phase loads, the loads are each connected 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 should comply with the requirements of NEMA Standards Publication No. 250-1985, Enclosures for Electrical Equipment (1000 Volts Maximum). To protect the current-carrying parts of a panelboard, motor starter, or controller against unfavorable external conditions, and to protect operating personnel against contact with these parts, the NEMA standard specifies the following enclosure classifications: •

A Type 1 enclosure is a general purpose enclosure that is suitable for normal conditions and that is used indoors. A Type 1 enclosure consists of a sheet metal case that is primarily intended to protect personnel against accidental contact with energized electrical equipment. A Type 1 enclosure can be either ventilated or nonventilated. When a Type 1 enclosure is used, specific gasketing material should be specified by the manufacturer.

•

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

•

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

•

A Type 3S enclosure is an enclosure that provides protection against dust and rain outdoors. A Type 3S enclosure also provides for the operation of external mechanisms when the enclosure is laden with ice.

•

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


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Classifications and Ratings (Cont'd) •

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

•

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

•

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

•

A Type 6 enclosure is an indoor or outdoor enclosure that provides protection against hose-directed water, temporary submersion in water, and damage from ice formation.

•

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

•

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

•

A Type 8 enclosure is an indoor or outdoor enclosure that is used in Class I hazardous 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 of the Mining Enforcement Safety Administration of the U.S. Department of the Interior.

•

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

•

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


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A Type 13 enclosure is an indoor enclosure that is used to provide a degree of protection against dust, spraying of water, oil, and/or noncorrosive coolant.The type of panelboard enclosure that is selected for an installation is dependent upon the loads that will be supplied by the panelboard as well as the environmental conditions at the panelboard location. Indoor and outdoor enclosure application comparisons 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 the minimum feeder capacity that the panelboard will supply to the loads. Panelboards should be marked by the manufacturer with the voltage and current rating of the panelboard as well as by the number of phases for which the panelboard is designed. The panelboard NEMA-type designator, nameplate rating, and design information should be visible on the outside front portion of the enclosure without having to disturb the interior parts or wiring. A danger sign that indicates the presence of a shock hazard should be clearly visible. If the panelboard has a door or cover, the NEMA-type designator, nameplate data, and danger sign should be clearly visible with the door or cover open. The door or cover should have a method to secure the door, 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 are horizontally mounted. The positions (e.g., "ON" and "OFF") that indicate the open and closed positions of the breakers and switches should be clearly marked at the breaker. The industry 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 horizontallymounted breakers or switches that are in parallel (as in Figure 1), the closed position is towards the center of the panelboard, and the open position is towards the edges of the panelboard. Each small molded-case breaker is usually connected to a single phase. Some single phase loads require a connection to two of the phases. The single phase load can be isolated through the use of a single breaker or two breakers. When two breakers are used to isolate the load, they should open or close at the same time. To ensure that breakers open and close at the same time, they are ganged. Ganged breakers have a mechanical connection that bridges the operating tips of the breakers.


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Typical Low Voltage Distribution Panelboard

Figure 1


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Classifications and Ratings (Cont'd) In addition to the required nameplate data markings that have already been described, the panelboard must also contain, either external to the enclosure or on the inside of the enclosure, 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 should be provided. The marking should be provided in the form of a pressure sensitive label in an envelope or on a card.

•

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

•

Any additional shock hazard, burn, or rotating equipment warning information should be prominently displayed on the outside of the panelboard or on the inside door 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 rating of the circuit breakers that will be used in the panelboard. When a panelboard contains molded-case breakers or switches, the breakers or switches are also required to be marked with nameplate data. The nameplate data must be marked on the molded case of the breaker, on the switch, or on an attached plate. Molded-case breaker or switch nameplate data must be located in a place where it is both visible and legible. Each molded-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.


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The rated current and rated operational voltage.

•

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

•

The words "ON" and "OFF" to indicate the closed and open positions at the place of operation. If symbols are used, "I" and "O" must be used to indicate the closed and 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 be marked to include the type of the accessory, the proper connections for the accessory (if the connections are not obvious), and the electrical ratings of the accessory. If any specialized application information or limitations are required for the operation of the breaker or switch, these data must be marked on the switch, as applicable.


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EVALUATING LOW VOLTAGE DISTRIBUTION PANELBOARDS UPON RECEIPT When low voltage distribution panelboards are ordered from the manufacturer or vendor, certain specifications must be met. The Saudi Aramco Electrical Design Engineer should make a determination as to what panelboard specifications (e.g., size, type, rating) are necessary for the installation through use of the correct Saudi Aramco installation requirements for low voltage distribution panelboards. When the panelboard is ordered, the panelboard specification information is then supplied to the manufacturer or the vendor. When the low voltage distribution panelboard shipment is received from the manufacturer or vendor, the Electrical Engineer should evaluate the panelboard shipment for compliance with the specifications that were provided with the original order. The Electrical Engineer should also evaluate the delivered low voltage distribution panelboard for any physical damage that occurred during the shipment from the manufacturer or the vendor. This section provides information on the following topics that are pertinent to evaluating low voltage distribution panelboards upon receipt: • •

Physical Inspection Verification Against Specification

Physical Inspection Prior to the acceptance of a low voltage distribution panelboard shipment, the Electrical Engineer should inspect the panelboard. A proper and thorough inspection of the panelboard for applicability, compliance with Saudi Aramco installation requirements, and physical damage prior to the installation can save cost-overruns that are associated with the installation. The installation of an improper, underrated, or damaged panelboard can waste money and resources by causing subsequent system damage or by requiring the frequent maintenance, repair, or replacement of the panelboard. A low voltage distribution panelboard physical inspection procedure is provided in Work Aid 1. During the physical inspection, the inspector should, at a minimum, check the ratings of the 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. If any problems exist, or if variations from the installation diagrams or drawings are noted, they should be promptly corrected or investigated. The panelboard should completely enclose all breaker or switch current-carrying parts and should be constructed of materials that are corrosion 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 tightly throughout the useful life of the panelboard. A door or cover that allows access to the interior of the panelboard should be fastened by screws or with a latch that can be locked.


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Physical Inspection (Cont’d.) When a panelboard is energized, voltage potentials will be present. To prevent line-to-line or line-to-ground shorts that could cause subsequent equipment damage, Saudi Aramco has minimum spacing requirements that should be met between live parts 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 creepage distances for electrical installation. A table of minimum spacings is provided in Figure 9 of Work Aid 1. In the table of minimum spacing, the spacing is measured between the bare portions of insulated conductors. To prevent wire deformation, terminal connection damage during installation, and line-to-line or line-to-ground shorts that could cause subsequent equipment damage, the wire-bending space between a wire connector or lug should be above a specified minimum value. The minimum distance between the end of any wire connector or lug and the wall of the panelboard enclosure toward which the conductor is directed or through which the connected conductor may 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 design team before the low voltage distribution panelboard is received from the manufacturer or the vendor. Although the specifications for the panelboard have already been determined, the Electrical 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) of the 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 the overall quality control process. The installation team could uncover installation design errors, manufacturing flaws, or installation conflicts that did not exist during the installation design phase. Careful vigilance and a familiarity with the requirements for Saudi Aramco panelboard installations are necessary for the proper verification of a panelboard installation against the installation specifications. As part of the receipt evaluation of low voltage distribution panelboard evaluation, the Electrical Engineer should also check that the panelboard that was received is in compliance with the installation blueprints and installation design documents. In some cases, the determination is conducted by reading an electrical plan that has the panelboard type and size identified. Then, the Engineer only has to inspect the manufacturer's marking on the panelboard and compare them to what is required on the electrical plan to determine whether the correct panelboard is being used. In other situations, the Electrical Engineer must rely on his knowledge of the correct application of panelboard types and sizes, and then determine whether the correct panelboard is being used. Panelboards are usually assembled with all components (e.g., switches, molded-case circuit breakers) already installed, so that when the panelboard 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 the panelboard and all of the components that are contained in the panelboard. Saudi Aramco DeskTop Standards

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Verification Against Specification (Cont'd) To ensure overall quality control for the low voltage distribution panelboard installation, the Electrical Engineer should also be familiar with the technical requirements for Saudi Aramco panelboard installations. Generally, the verification against specification is conducted through determination of whether the panelboard type and rating to be installed match the panelboard type and rating that are required for the installation. If any doubt exists as to whether a received panelboard meets the technical requirements for Saudi Aramco installations, the technical requirement publications should be referenced. Saudi Aramco uses the following publications for panelboard installations: •

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

•

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

•

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


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EVALUATING LOW VOLTAGE DISTRIBUTION PANELBOARD INSTALLATION AND TESTING After the verification of the low voltage distribution panelboard against the required specifications of the installation is complete, the low voltage distribution panelboard is installed and tested. Prior to commissioning, the low voltage distribution panelboard installation 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 with Saudi Aramco installation requirements is performed through conduct of a visual inspection of 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 the panelboard and enclosed equipment labeling, grounds, feeder conductors, and connections. In addition to the visual inspection, tests should be performed to ensure that contact resistance is low, that insulation resistance is high, and that the installation meets system overcurrent requirements. This section provides information on the following topics that are pertinent to evaluating low voltage 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 and indexing of all conductors, connections, and terminations at the panelboard for compliance with Saudi Aramco and industry specifications. The inspection is performed through a visual check 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 are intended for use as ungrounded current-carrying conductors (single or multiple-conductor cables) 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 be identified 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 otherwise permanently and individually identified throughout their length. All low voltage cables (1000 volts, or less) should be marked in accordance with ANSI/NFPA-70 Article 310.


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Labeling/Indexing (Cont'd) Cable labeling information that is required for low voltage distribution panelboards is provided in Work Aid 2. Examples of the type of information that is required are the maximum working voltage for which the conductor was tested or approved, the letter designation for the type of cable and insulation, the manufacturer's name, trademark, or other distinctive marking to identify the cable, the sq mm size of the cable, and the number of conductors in the cable (if a multiple-conductor cable is used). Cable labeling information is provided at periodic intervals on the side of the cable. Because the labeling information appears on the cables at periodic intervals, the labeling information may not appear near to the panelboard as a result of where the cable or wire was cut. To ensure that installation and maintenance personnel can correctly identify a wire or cable, 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 should be marked at the outside of the panelboard where it is clearly visible and at the termination points (e.g., terminal block, breaker) inside the panelboard. The cable end label or tag should indicate the phase ("A" "B" or "C") on single conductor cables, the circuit voltage (480 V, 2.4 kV etc.). For power cables, the label or tag should indicate the conductor number and size (3250 MCM, 3-No.4 AWG, etc.) and the cable identification index number (from construction drawings). Wiring at terminal blocks is identified through the use of permanently embossed heat-shrinkable or slip-on-type wire markers. Wrap-around, rigid snap-on, or adhesive-type markers are not permitted at terminal blocks. The cable identification index number is provided as a reference to a blueprint or circuit diagram. The cable identification index number should indicate where the cable is being routed from and where it is being routed to. During the evaluation of the low voltage distribution panelboard, the Electrical Engineer should visually check that the index number that appears on the label (or tag) at the termination of the wire or cable correctly matches the corresponding 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 power distribution system. There should be a connection to ground for the panelboard enclosure, as well 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 look for evidence of incorrect connections, terminations, or fittings. The Electrical Engineer should also assess compliance with the cognizant Saudi Aramco or industry grounding system standards. Ground connection inspection items are provided in Work Aid 2.


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Rating Check (42 kA) For Saudi Aramco wire and cable installations, any power distribution bus should be rated for a minimum continuous current rating of 600 A, and all phase, neutral, and ground busses should be able to withstand 42 kA rms symmetrical fault amperes. A low voltage distribution panelboard 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 all current-carrying equipment that is connected to the panelboard should have a 42 kA minimum current rating. The rating check should be performed by the Electrical Engineer during the visual inspection of the low voltage distribution panelboard. The rating should be included in the nameplate data.

Switchgear Feed Because a low voltage distribution panelboard supplies power to equipment, the cable that feeds power to the panelboard should be the correct size for the installation and should be connected to the panelboard to provide the proper phase rotation. The Electrical Engineer should compare the switchgear feeder cable size and type with the installation blueprints or drawings to ensure that the feeder can handle the maximum continuous and fault currents that could arise at the panelboard. During the operational checks of the power that is supplied by the distribution system, a rotational check should also be performed on each connected piece of 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 distribution panelboard insulation resistance with a megger. To conduct the megohmmeter test, the megger is connected between two of the panelboard phases, and the megger is operated for one minute. The test is performed at the main incoming voltage side and at the downstream side of each switch, breaker, or disconnect that is enclosed in the panelboard. Electrical test reference information for the insulation resistance (megger) test is provided in the Saudi Aramco Pre-Commissioning Form Testing Guide Lines, P-000 (see Figure 11 of Work Aid 2). This form is obtained from the Instrumentation Unit of the Consulting Services Department. The electrical test reference information provides the recommended megohmmeter test voltages for various voltage ranges. Similar megger readings are taken between each remaining phase pair combination and from each phase to ground. The Electrical Engineer should evaluate the insulation resistance (megger) test values to ensure that the insulation resistance values that were recorded are greater than the manufacturer's minimum values. If the manufacturer's minimum values are not provided, the value 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 1.6 megohms. Any value of insulation resistance that is below the minimum specifications should be investigated by the Electrical Engineer who is performing the test data evaluation. Saudi Aramco DeskTop Standards

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Insulation Resistance(Megger) Test (Cont'd) Amplifying instructions for additional megger testing (e.g., dielectric absorption ratios) are provided in Work Aid 2.

Contact ResistanceTest The electric power distribution system is designed to deliver electric power from the source to the loads with a minimum power loss. The resistance of switch, breaker, or disconnect contacts that are installed in a low voltage distribution panelboard should be extremely low when the contacts are closed and extremely high when the contacts are open. The contact resistance test is conducted through measurement of the circuit continuity across the switch, breaker, or disconnect contacts with a micro-ohmmeter. Switch, breaker, or disconnect contacts should have a resistance value of less than 200 micro-ohms across them when they are closed. Electrical test reference information for the insulation contact resistance test is provided 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 distribution panelboards that have overcurrent trip settings. The type of overcurrent test that is performed is dependent on the type and rating of the breaker that is installed in the panelboard. To perform an overcurrent test, a current injection test set (Multiamp MS2 or equivalent) is connected across the line, and load terminals of one pole of the circuit breaker and a test current are applied. The overcurrent test is intended to verify that the trip systems of the breaker operate in accordance with the marked trip settings on the breaker nameplate. Trip tests are performed in one of two ways: an instantaneous value of current is injected at the breaker and the trip time is determined, or the rated current is injected and the breaker performance is monitored. Because high fault current can have disastrous results, and because it is imperative that the breaker trip properly, the instantaneous trip test is the most important. Manufacturer's preset values are tested and logged. The overcurrent trip test values and tolerances for successful overcurrent trip tests are provided in Figures 13 and 14 of Work Aid2.


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WORK AID 1: REFERENCES FOR EVALUATING LOW VOLTAGE DISTRIBUTION PANELBOARDS UPON RECEIPT

LowVoltage Distribution Panelboard Enclosure General Use Circuit breaker and switch low voltage panelboard enclosures should comply with the requirements of NEMA Standards Publication No. 250-1985, Enclosures for Electrical Equipment (1000 Volts Maximum). For Saudi Aramco low voltage distribution panelboard installations, ventilated enclosures are permitted for circuit breaker frame sizes that are rated for 400 amperes or more. Figure 5 shows the types of enclosures that are used in Saudi Aramco power distribution installations:


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WORK AID 1 (Cont'd) Enclosure Application Types Use

Enclosure Type

Location

Type 1

A general purpose enclosure that is suitable for normal conditions.

Indoors

Type 2

A drip-proof enclosure that is suitable for dripping conditions.

Indoors

Type 3

A dust-tight and rain-tight enclosure.

Outdoors

Type 3S

A dust-tight and rain-tight enclosure that allows external mechanisms to operate with laden ice.

Outdoors

Type 3R

A rainproof enclosure.

Outdoors

Type 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 to meet the hose test (see NEMA ICS 6-110.56).

Both

Type 5

An enclosure that protects against settling airborne particles and dripping liquids.

Indoors

Type 6

A submersible, water-tight, and dust-tight enclosure.

Both

Type 6P

A prolonged-submersion, submersible, water-tight, and dust-tight enclosure.

Both

Type 7

An enclosure that is suitable for most Class I hazardous locations.

Indoors

Type 8 Type 9

An enclosure that is suitable for Class I hazardous locations. An air-break equipment enclosure that is suitable for Class II hazardous locations. An enclosure that is suitable for coal mines.

Both Indoors

A dust-tight and drip-tight enclosure that is designed to be used in industrial applications. A dust-tight and drip-tight enclosure with knockout panels that is designed to be used in industrial application s.

Indoors

An oil-tight and dust-tight enclosure that is used primarily to house pilot devices.

Indoors

Type 10 Type 12 Type 12K Type 13

NOTE:

Indoors

Indoors

Type 1, 2, 3R, 9, and 12 enc losures may be eithe r ventilate d or non-ventilated. Type 3 , 4, 4X, 6, 7, 8, 10, 11, and 13 are nonventilated-type enclosures. Type 12 ventilated enclosures are not dust tight. For the use of enclosure Types 1 and 3, specific gasketing material should be specified by the manufacturer.

Enclosure Application Types

Figure 5


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WORK AID 1 (Cont'd) Comparisons for specific applications of indoor and outdoor enclosures are shown in Figures 6 and 7. Provides a Degree of Protection Against the Following Environmental Conditions

Incidental contact with the enclosed equipment Falling dirt Falling liquids and light splashing Circulating dust, lint, fibers, and flyings** Settling airborne dust, lint, fibers, and flyings** Hosedown and splashing water Oil and coolant seepage Oil or coolant spraying and splashing Corrosive agents Occasional temporary submersion Occasional prolonged submersion

Types of Enclosures 1 * X X -------------------

2 * X X X -----------------

4

4X

5

6

6P

12

12K

13

X X X X X X -----------

X X X X X X ----X -----

X X X --X -------------

X X X X X X ------X ---

X X X X X X ----X X X

X X X X X --X ---------

X X X X X --X ---------

X X X X X --X X -------

*

These enclosures may be ventilated. However, Type 1 may not provide protection against small particles 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 ignitable fibers or combustible flyings. For Class III type ignitable fibers or combustible flyings see the National Electrical Code, Article 500.

Comparison of Specific Applications of Enclosures for Indoor Nonhazardous Locations

Figure 6


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WORK AID 1 (Cont'd) Provides a Degree of Protection Against the Following Environmental Conditions Incidental contact with the enclosed equipment Rain, snow, and sleet* Sleet** Windblown dust Hosedown Corrosive agents Occasional temporary submersion Occasional prolonged submersion

Types of Enclosures 3 X X --X ---------

3R*** X X -------------

3S X X X X ---------

4 X X --X X -------

4X X X --X X X -----

6 X X --X X --X ---

6P X X --X X X X 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 Locations

Figure 7


18



Procedure for Panelboard Enclosure Inspection The following procedure should be followed to perform an inspection of a low voltage distribution panelboard. The inspection is performed to evaluate the operating panelboard environment, the panelboard condition, the condition of all equipment that is contained in the panelboard (e.g., molded-case circuit breakers), and to determine whether any physical damage to the panelboard has occurred. If, for any reason, electric power could be supplied to the panelboard, ensure that the electric power is removed. Hazardous voltages in electrical equipment can cause severe personal injury or death. Turn off the panelboard power supply before any of the following inspections are performed. 1.

Verify that the panelboard is of the correct type and rating for the installation in accordance 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 and between those conductors and ground to positively determine that the equipment is deenergized. Proper Saudi Aramco practices and procedures should be followed when the verification is performed.

5.

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

6.

Examine the interior of the panelboard for the presence of dirt, dust, soot, grease, or moisture.

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 in accordance with the installation diagrams and drawings.

9.

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

10.

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


19



WORK AID 1 (Cont'd) MinimumPanelboard Spacing Requirements To prevent line-to-line or line-to-ground shorts that could cause subsequent equipment damage, Saudi Aramco has minimum spacing requirements that should be met between live parts 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 creepage distances for installation. Figures 8 and 9 contain excerpts from AB 1 that provide minimum spacings between the bare portions of insulated conductors and between conductors and ground as well as the minimum distance between the end of any wire connector or lug and the wall of the panelboard enclosure.

Minimum Spacing in (MM) Inches Other Than at Terminals Between Between Terminals Uninsulated Live Between Uninsulated Live Parts and Any and Any Ground Parts of Opposite Ground Metal* Polarity Metal * B C E D** Through Over Through Over Through Over Through Over Air Surface Air Surface Air Surface Air Surface

At Terminals Between Terminals of Opposite Polarity Voltage A Betwee Through Over n Air Surface Parts 3/ (19.05) 0-125 1/2 (12.7) 4 126-300 3/ (19.05) 1 1/ 4 4 301-600 1 (25.4) (31.75) 2 (50.8)

1/ 1/

2 (12.7)

2 (12.7) 1/ (12.7) 2

1/ 1/

2 (12.7)

2 (12.7) 1/ (25.4) 2

1/ 1/

4 (63.5)

4 (6.35) 3/ (9.52) 8

3/ 3/

8 (9.52)

8 (9.52) 1/ (12.7) 2

1/ 1/

2 (12.7)

2 (12.7) 1/ (12.7) 2

1/ 1/

2 (12.7)

2 (12.7) 1/ (25.4) 2

1/

4 (63.5)

3/

4 (6.35) 3/ (9.52) 8

1/

1/

3/

8 (9.52) 8 (9.52) 2 (12.7)

* The spacing to the enclosure or circuit breaker mounting means is permitted to be reduced if an

acceptable liner of insulating material, not less than spacing through air.

1/

32 inch

in thickness, is used to provide the required

** If indentation or deformation of the overall enclosure or circuit breaker mounting means might reduce

spacings to less than those indicated in Column E. If indentation or deformation of the overall enclosure or circuit breaker mounting means will not affect spacings.

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

Figure 8


20



WORK AID 1 (Cont'd)


21



Minimum Wire-Bending Space

Figure 9


22



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

Low Voltage Panelboard Labeling/Indexing The following enclosure markings are required to be provided (in a durable manner) directly on a panelboard, on a nameplate that is attached to the exterior of the panelboard cover, or on the 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 to be provided (in a visible and legible manner) on a switch or circuit breaker itself or on a nameplate 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-circuit breaking capacities. (For circuit breakers that are rated 240 volts maximum with short circuit breaking capacities of 5000 amperes, the short circuit breaking capacity can be omitted.)

•

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

•

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

•

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

•

Rated short-time withstand currents (if applicable).


23



WORK AID 2 (Cont'd) A circuit breaker that is provided with an accessory or accessories should be marked to include the type, proper connections (if not obvious), and the electrical ratings of the accessories. Any additional specialized applications information or limitations should be marked on the breaker as applicable. Cable labeling information that is required for low voltage distribution panelboards is as follows: •

The maximum working voltage for which the conductor was tested or approved.

•

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 along with the year that the panelboard was manufactured.

•

The sq mm (AWG of MCM) size and number of conductors if multipleconductor 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 be distinguished 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 other readily identifiable means.

All power cables that are installed in a panelboard should be durably marked at the end of the panelboard with approved labels or tags that indicate the following information (if the information 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 is not shown on cable jacket.

•

The cable identification number (from construction drawings).


24



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 for one conductor, 3/C for three conductors, 12/C for twelve conductors, or 25 pair for 25 pairs of conductors. 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 be used. The voltage class of the cable as given by the manufacturer or as required by the design should 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 EPR XLPE PE

-

polyvinyl chloride. ethylene propylene rubber. crosslinked polyethylene. polyethylene.

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


25



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 are intended for use as grounded or neutral conductors should have an outer finish of a white or natural grey color.

•

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

•

An insulated conductor that is larger than 16 sq mm (No.6 AWG) is identified as a grounding conductor at each end and at every point where the conductor is accessible through performance of one of the following: -

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 voltage distribution panelboards. Saudi Aramco Pre-Commissioning Form P-000, Testing Guide Lines (Obtained from Instrumentation Unit, Consulting Services Department)

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


26




27



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

Figure 10


28




29




Figure 10(Cont'd)


30




31




Figure 10(Cont'd)


32



WORK AID 2 (Cont'd) Information, Formulas, and Tablesfor Usein Evaluating theResults of Megger Tests

The following 60-second megger tests are conducted for low voltage distribution panelboard commissioning: • •

Phase-to-Phase Phase-to-Ground

If additional megger test data are required, a dielectric absorption ratio megger test can be performed. When a dielectric absorption ratio megger test is performed, the polarization index can be determined through use of the following equation:

Figure 11 provides insulation conditions for 60/30 second ratio results (if recorded) and for 10/1 minute ratio results. Insulation Condition Dangerous

60/30 - Second Ratio ---

10/1 - Minute Ratio (Polarization Index) Less than 1

Questionable (Perform investigation)

1.0 to 1.25

1.0 to 2

Good

1.4 to 1.6

2 to 4

Excellent

Above 1.6

Above 4

Dielectric Absorption Ratio Chart

Figure 11


33



WORK AID 2 (Cont'd) Overcurrent Trip Test

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

Breaker Voltage Volts 240 240 600 600 240 240 600 600 600 600 600 600

Range of Rated Continuous Current Amperes 15-45 50-100 15-45 50-100 110-225 250-400 110-225 250-400 450-600 700-1200 1400-2500 3000-5000

Maximum Trip Time In Seconds* 50 70 70 125 200 300 250 300 350 500 600 650

* For integrally-fused circuit breakers, trip times may be substantially longer if tested with the fuses replaced by solid links (shorting bars). Consult the manufacturer if additional information is required.

Values for Overcurrent Trip Test

Figure 12


34



WORK AID 2 (Cont'd)

Tolerances of High and Low Settings Frame Size, Amperes £250

Hi ±20%

Lo ±25%

FACTORY

+40% -25% ±20%

+40% -30% ±25%

FIELD

±25%

±30%

FACTORY FIELD

³400

Instantaneous Trip Setting Tolerances

Figure 13


35

Commissioning Low Voltage Distribution Panelboards

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