Commissioning Switchgear, Low-Voltage and Circuit Breakers

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Note:

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

Warning:

Warning: The material contained in The material contained in this document was this document was developed for Saudideveloped for Saudi Aramco and is intended for the exclusive use of Saudi Aramco’s employees. Aramco and is intended for the exclusive use of Saudi Aramco’s employees. Any material contained in this document which is not already in the public Any material contained in this document which is not already in the public domain may not be

domain may not be copied, reproduced, sold, given, or disclosed to thirdcopied, reproduced, sold, given, or disclosed to third parties, or otherw

parties, or otherwise used in whole, or in part, without the wrise used in whole, or in part, without the written permissiitten permissionon

Commissioning Low-Voltage

Switchgear And Circuit Breakers

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C

Coonntteenntt PPaaggee

INTROD

INTRODUCTION...UCTION... 11 SAUDI A

SAUDI ARAMCO CRAMCO COMMIOMMISSIONSSIONING REQING REQUIREUIREMENTSMENTS ... 22 Swit

Switchgearchgear ... 22 Circ

Circuit uit BreaBreakerskers ... 55 EVALUATING LOW-VOLTAGE

EVALUATING LOW-VOLTAGE SWITCHGEAR SWITCHGEAR AND CI

AND CIRCUIT RCUIT BREAKBREAKERS UPERS UPON RECON RECEIPTEIPT ... 99 Vis

Visual Iual Inspenspectiction...on... 99 Ver

Verifiificatcation ion AgaAgainsinst t SpecSpecifiificatcationsions ... 99 Low-V

Low-Voltage oltage SwitSwitchgeachgear r NameNameplatplate...10e...10 Cir

Circuit cuit BreaBreaker ker NameNameplatplate...11e...11 EVALUATING LOW-VOLTAGE SWITCHGEAR AND CIRCUIT BREAKER

EVALUATING LOW-VOLTAGE SWITCHGEAR AND CIRCUIT BREAKER INSTA

INSTALLATILLATION ON AND AND TESTINTESTING...13G...13 Vis

Visual ual InsInspectpection...13ion...13 Sui

Suitabtabililityity ...14...14 Phy

Physisical cal DamDamage...15age...15 Alignment...15 Alignment...15 Cl

Cleaneanlilinesness...15s...15 Arc Chut

Arc Chute e AssAssembemblyly ...17...17 Contact

Contactss ...17...17 Mec

Mechanihanism/sm/LinLinkagkagee ...18...18 Lubr

Lubricaticationion ...18...18 Mech

Mechanicanical al InsInspectpectionion ...18...18 Bolt Torque...19 Bolt Torque...19 Door

Door OperatiOperationon ...19...19 Rack In - Rack Out...19 Rack In - Rack Out...19 Open/

Open/ClosClose e OperOperatioation...20n...20 Elec

Electritrical cal InsInspectpectionion ...21...21 Ins

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Func

Functiontional al OperOperatioationn ...23...23

Aux Auxiliiliary ary EquEquipmipmentent ...24...24

SYSTEM PRE-OPE SYSTEM PRE-OPERATIORATIONAL CHECK-OUT PHASE REQUIREMENNAL CHECK-OUT PHASE REQUIREMENTSTS ...25...25

Point Point-to--to-Point Wiring CheckPoint Wiring Check ...25...25

Subsy Subsystem Checkostem Checkoutut ...25...25

Inter Interlockslocks...25...25

SYSTEM OPERATION SYSTEM OPERATIONAL AL TESTINTESTING G PHASE REQUIREMENPHASE REQUIREMENTS...26TS...26

WOR WORK AID 1K AID 1:: REFERREFERENCES FENCES FOR EVAOR EVALUATLUATING LOING LOW-VOW-VOLTAGLTAGEE SWITCHGEAR SWITCHGEAR AND CIRCAND CIRCUIT BREAKERS UIT BREAKERS UPON RECEIUPON RECEIPTPT ...27..27

Low-Voltage Switchgea Low-Voltage Switchgear and Cir and Circuit Brcuit Breaker Areaker Applicatipplications Checklons Checklistist ...34...34

WOR WORK AID 2K AID 2:: REFERREFERENCES FENCES FOR EVAOR EVALUATLUATING LOING LOW-VOW-VOLTAGLTAGEE SWITCHGEAR AND CIRCUIT BREAKER SWITCHGEAR AND CIRCUIT BREAKER INSTALLATIONINSTALLATION AND AND TESTINTESTING...35G...35

NETA Checkli NETA Checklists...sts...35..35

Information, Formulas, and Tables for Use in Evaluating the Results of Information, Formulas, and Tables for Use in Evaluating the Results of Insu Insulatilation on ResiResistastance nce (Megg(Megger) er) TestsTests ...44...44

Saudi Aramco Pre-Commissioning Forms...45

GLOSSARY...56

---T Taabblle e oof f FFiigguurrees s PPaaggee Figur Figure 1: e 1: WestWestinghoinghouse Typuse Type DS Low-e DS Low-VoltVoltage Swiage Switchgetchgear Sectar Sectionion ... 33 Figur Figure 2: e 2: GE AKR ManGE AKR Manual Lowual Low-Vol-Voltage Cirtage Circuit Brcuit Breaker...eaker... 66 Figure 3: Figure 3: GE AKR Low-GE AKR Low-VoltaVoltage Circuige Circuit Breaket Breaker Contact Sr Contact Structtructure...ure... 77 Figure 7: Figure 7: Saudi Aramco Low-Voltage Power SwiSaudi Aramco Low-Voltage Power Switchgear Requitchgear Requirementsrements (From 1 (From 16-SAM6-SAMSS-502SS-502)) ...28...28

Figure Figure 8: 8: Low-Voltage Low-Voltage Switchgear Switchgear Buyer Buyer Data Data Sheet..Sheet...29..29

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Figure 10:

Figure 10: Low-Voltage Power Low-Voltage Power Circuit Breaker RCircuit Breaker Rating, Design,ating, Design, Constru

Construction, and Auxiliction, and Auxiliary Device Instalary Device Installation Requirlation Requirementsements ...32...32 Figure 10:

Figure 10: Low-Voltage Power CircuiLow-Voltage Power Circuit Breaker Rating, Desit Breaker Rating, Design,Construction,gn,Construction, and Auxil

and Auxiliary Deiary Device Insvice Installatallation Reqtion Requiremeuirements (Cont'd)nts (Cont'd) ...33.33 Figure 11:

Figure 11: Low-Voltage Low-Voltage Switchgear Switchgear ConstructiConstruction Geon General neral RequirementsRequirements ...39....39 Figure

Figure 12: 12: Low-Voltage Low-Voltage Switchgear Switchgear Stationary Stationary Structure Structure Requirements.Requirements...40...40 Figure

Figure 13: 13: Low-Voltage Low-Voltage Switchgear Switchgear Bus Bus ConstructioConstruction n RequirementsRequirements ...41....41 Figure 14:

Figure 14: Low-Voltage SwitcLow-Voltage Switchgear Bus Connecthgear Bus Connection and Cable Termion and Cable Terminationination Const

Constructruction ion RequiRequiremerementsnts ...42...42 Figure 15:

Figure 15: Low-Voltage SwLow-Voltage Switchgear Nitchgear Nameplate Cameplate Construction onstruction Requirements...Requirements...43....43 Figure

Figure 16: 16: Dielectric Dielectric Absorption Absorption Ratio Ratio Chart..Chart...44...44 Figure 17:

Figure 17: Saudi Aramco PreSaudi Aramco Pre-Commis-Commissioning Forsioning Form, P-023, Switchm, P-023, Switchgear-General...gear-General...46..46 Figure 17:

Figure 17: Saudi Aramco Saudi Aramco Pre-Commissioning Form, Pre-Commissioning Form, P-023,P-023, Swit

Switchgeachgear-Ger-General neral (Cont(Cont'd)'d)...47...47 Figure 17:

Figure 18: Saudi Aramco Saudi Aramco Pre-Commissioning Form, Pre-Commissioning Form, P-008,P-008, Low-V

Low-Voltage oltage Power Power CircuCircuit it BreakeBreakers...50rs...50 Figure 18:

Low-Voltage Power oltage Power CircuCircuit it BreakeBreakers rs (Cont(Cont'd)...51'd)...51 Figure 18:

Low-Voltage Power oltage Power CircuCircuit it BreakeBreakers rs (Cont(Cont'd)...52'd)...52 Figur

Figure 19: e 19: GI 2.lGI 2.l710 Exc710 Excerpt...54erpt...54 Figur

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INTRODUCTION INTRODUCTION

The selection of the type and size of switchgear and the associated power circuit breakers are The selection of the type and size of switchgear and the associated power circuit breakers are based on

based on the technical, installatithe technical, installation, on, and and economieconomic c requirrequirements of ements of a a facilfacility. ity. FaciliFacility ty switchgear switchgear and circuit breaker technical requirements include the system voltage level, fault current, and the and circuit breaker technical requirements include the system voltage level, fault current, and the number and type

number and type of loads. of loads. Once the type Once the type of switchgear and of switchgear and circuit breakers for circuit breakers for a givena given installation are

installation are chosen, the schosen, the switchgear is assembled witchgear is assembled and the circuit and the circuit breakers are installed. breakers are installed. TheThe commissioning process for low-voltage switchgear and circuit breakers in Saudi Aramco facilities commissioning process for low-voltage switchgear and circuit breakers in Saudi Aramco facilities ensures that a safe and cost-effective system is installed and that this system will perform to the ensures that a safe and cost-effective system is installed and that this system will perform to the specifications of the

specifications of the facility for facility for the projected operating lifetime the projected operating lifetime of the facility. of the facility. Experience hasExperience has shown that the time and effort that is expended up front to ensure safety, quality control, and shown that the time and effort that is expended up front to ensure safety, quality control, and adherence to Saudi Aramco and industry standards minimizes subsequent equipment failure.

adherence to Saudi Aramco and industry standards minimizes subsequent equipment failure.

The commissioning process for low-voltage switchgear and circuit breakers involves evaluations, The commissioning process for low-voltage switchgear and circuit breakers involves evaluations, verifications, and checks that determine whether the proper switchgear and circuit breaker verifications, and checks that determine whether the proper switchgear and circuit breaker specifications and installation

specifications and installation requirements are requirements are met. met. Tests are Tests are also performed also performed that determinethat determine whether the electric power distribution system will operate properly and safely after installation. whether the electric power distribution system will operate properly and safely after installation. When the low-voltage switchgear and circuit breakers are inspected and tested satisfactorily When the low-voltage switchgear and circuit breakers are inspected and tested satisfactorily during the commissioning process, the system should operate in accordance with manufacturer's during the commissioning process, the system should operate in accordance with manufacturer's specifications for its maximum useful life.

specifications for its maximum useful life.

This Module provides information on the following topics and subtasks that are pertinent to This Module provides information on the following topics and subtasks that are pertinent to commissioning low-voltage switchgear and circuit breakers for Saudi Aramco installations:

commissioning low-voltage switchgear and circuit breakers for Saudi Aramco installations:

•

• Saudi Aramco Commissioning RequirementsSaudi Aramco Commissioning Requirements •

• Evaluating Low-Voltage Switchgear and Circuit Breakers Upon Evaluating Low-Voltage Switchgear and Circuit Breakers Upon ReceiptReceipt •

• Evaluating Low-Voltage Switchgear and Circuit Breaker Installation and TestingEvaluating Low-Voltage Switchgear and Circuit Breaker Installation and Testing •

• System Pre-Operational Check Out Phase RequirementsSystem Pre-Operational Check Out Phase Requirements •

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SAUDI ARAMCO COMMISSIONING REQUIREMENTS SAUDI ARAMCO COMMISSIONING REQUIREMENTS

Large process and process support equipment in industrial facilities requires electric power to Large process and process support equipment in industrial facilities requires electric power to function.

function. Also, the Also, the operations, maintenance, and support operations, maintenance, and support personnel who personnel who work in work in an industrialan industrial facility require

facility require electric power electric power for for lights, fans, lights, fans, computers, and computers, and other support other support equipment. equipment. TheThe electric power that is required to run equipment is passed through a distribution system that electric power that is required to run equipment is passed through a distribution system that routes the electric power to the correct equipment

routes the electric power to the correct equipment. . The distribution systThe distribution system also provides electricem also provides electric power control cap

power control capabilitiesabilities, as well as rapid fau, as well as rapid fault isolatilt isolation and protectionon and protection..

Low-voltage switchgear and the circuit breakers that are contained in the switchgear are a small Low-voltage switchgear and the circuit breakers that are contained in the switchgear are a small but

but important important part part of of the the distributdistribution ion system. system. Low-voltage Low-voltage switchgear switchgear and and circuit circuit breakersbreakers generally supply power to

generally supply power to support ancillary loads, ssupport ancillary loads, such as a uch as a cooling fan. cooling fan. This section of This section of thethe Module contains information on Saudi Aramco applications and requirements for low-voltage Module contains information on Saudi Aramco applications and requirements for low-voltage switchgear and circuit breakers.

switchgear and circuit breakers.

Switchgear Switchgear

Saudi Aramco uses compartmentalized, metal-enclosed, low-voltage switchgear assemblies in Saudi Aramco uses compartmentalized, metal-enclosed, low-voltage switchgear assemblies in three-phase electric power systems that have a maximum of 600 V ac (rms) at a nominal three-phase electric power systems that have a maximum of 600 V ac (rms) at a nominal frequency of 60 Hertz.

frequency of 60 Hertz. When low-voltage power switchgear is received from When low-voltage power switchgear is received from the manufacturer, itthe manufacturer, it is generally a

is generally a finished product that is finished product that is complete in all rcomplete in all respects. espects. A finished low-voltage A finished low-voltage switchgear switchgear that is complete in all respects is factory assembled, wired, adjusted, and it includes power circuit that is complete in all respects is factory assembled, wired, adjusted, and it includes power circuit breakers, buses,

breakers, buses, instrumeninstruments, ts, switches, wiring, switches, wiring, space space heaters, terminationsheaters, terminations, , painting, nameplates,painting, nameplates, and tests (as required) so that the low-voltage switchgear is ready for operation when it is set in and tests (as required) so that the low-voltage switchgear is ready for operation when it is set in place.

place. The low-voltage switchgThe low-voltage switchgear bus connections and cable terminaear bus connections and cable terminations must be in accordancetions must be in accordance with

with Saudi Saudi Aramco and Aramco and industry industry requirements and requirements and standards. standards. The The minimum minimum mandatorymandatory requirements for the design and construction of an indoor metal-enclosed low-voltage switchgear requirements for the design and construction of an indoor metal-enclosed low-voltage switchgear assembly are provided in Work Aid 1.

assembly are provided in Work Aid 1.

Figure 1 shows a Westinghouse-Type DS low-voltage switchgear section. The basic construction Figure 1 shows a Westinghouse-Type DS low-voltage switchgear section. The basic construction of distribution switchgear is a stationary enclosure that contains buses, circuit breakers, and of distribution switchgear is a stationary enclosure that contains buses, circuit breakers, and control

control equipment. equipment. The statThe stationary parionary part of t of low-voltage low-voltage switchgeswitchgear musar must be t be a ventia ventilated lated andand verminproof NEMA Type 1

verminproof NEMA Type 1 enclosure. enclosure. To reduce future To reduce future facility modification costs, the facility modification costs, the enclosureenclosure must permit future extension at each end unless specified otherwise. For example, additional must permit future extension at each end unless specified otherwise. For example, additional switchgear can be connected to the main buswork and the ground bus that are shown in Figure 1. switchgear can be connected to the main buswork and the ground bus that are shown in Figure 1. The stationary structur

The stationary structure will have the e will have the required number of compartments to house removable air or required number of compartments to house removable air or vacuum circuit breakers.

vacuum circuit breakers. Each circuit Each circuit breaker must breaker must be provided with be provided with a breaker a breaker cover (safetycover (safety barrier)

barrier) and and latch latch that that closes closes the the compartment compartment completely completely whether whether the the breaker breaker is is racked racked in in or or removed.

removed. Meters for Meters for system system monitoring must monitoring must also also be be provided along provided along with with the the associatedassociated indicating lights

indicating lights and selector and selector switches. switches. Each switchgear segment and Each switchgear segment and circuit breaker compartmentcircuit breaker compartment must have a nameplate that describes the associated electrical design parameters.

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Figure 1:

Figure 1: Westinghouse Type DS Westinghouse Type DS Low-Voltage Switchgear SectionLow-Voltage Switchgear Section

Metal-enclosed low-voltage switchgear assemblies must be furnished from the manufacturer with Metal-enclosed low-voltage switchgear assemblies must be furnished from the manufacturer with three-ph

three-phase main ase main and feeder buses, and feeder buses, neutral bus neutral bus (if specified), (if specified), and ground bus. and ground bus. The incomingThe incoming power supply (with an

power supply (with an associated isolatiassociated isolation breaker) is on breaker) is connected to a connected to a three-phasthree-phase main e main bus and bus and aa neutral bus

neutral bus (if (if specified). specified). The incoming The incoming power supply power supply is sis sometimes called ometimes called the "incomer." the "incomer." TheThe main bus supplies power to a feeder bus (and associated feeder breakers) that feeds multiple main bus supplies power to a feeder bus (and associated feeder breakers) that feeds multiple low-voltage loads.

voltage loads. Some switchgear may have multiple power Some switchgear may have multiple power supplies, in which case, the supplies, in which case, the two power two power supplies are joined by a "tie" bus (and an associated tie breaker) that can connect the two power supplies are joined by a "tie" bus (and an associated tie breaker) that can connect the two power

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To facilitate future system expansion and to minimize expansion modification costs, spare To facilitate future system expansion and to minimize expansion modification costs, spare switchgear compartments

switchgear compartments must must be be provided. provided. The fThe following unused ollowing unused compartments should compartments should bebe provided at

provided at the the end end of of each each metal-enclometal-enclosed sed low-voltage switchgelow-voltage switchgear ar assemassembly bly and and as as specispecified infied in the Engineering Drawings:

the Engineering Drawings:

•

• SPARE SPARE A A completely completely developed developed compartment compartment (including (including a a power power circuit circuit breaker,breaker,

protectiv

protective e relays, relays, control control switchesswitches, , and and indicatiindicating ng lights) that lights) that is is ready ready for for operation when the feeder and control cables are

operation when the feeder and control cables are connected to a load.connected to a load.

•

• SPASPACECE A coA compampartrtmenment tht that iat is des develvelopeoped sid simimilarlarly tly to tho the SPe SPARE ARE comcomparpartmtment ent butbut

without an installed power circuit breaker. without an installed power circuit breaker.

•

• FUTURFUTUREE A compaA compartmrtment thaent that is devet is developeloped with std with statioationary elnary elemenements sucts such as primh as primaryary

studs, current transformers, safety shutters, sliding rail, rail guides, levering studs, current transformers, safety shutters, sliding rail, rail guides, levering mechanism, safety interlocks, secondary disconnects, and circuit breaker mechanism, safety interlocks, secondary disconnects, and circuit breaker control devices and wiring.

control devices and wiring.

For installation and maintenance, a circuit breaker lifting device and manual circuit breaker For installation and maintenance, a circuit breaker lifting device and manual circuit breaker racking lever or

racking lever or ratchet handle must ratchet handle must be provided be provided with each with each switchgear assswitchgear assembly. embly. DeviceDevice nameplates are also

nameplates are also required for required for the identification the identification of each of each breaker and auxiliary breaker and auxiliary unit. unit. TheseThese nameplates indicate the circuit number and the load that is served or the equipment that is nameplates indicate the circuit number and the load that is served or the equipment that is contained within the

contained within the auxiliary cubicle (if auxiliary cubicle (if present). present). To alert To alert employees to the employees to the danger of electricdanger of electric shock during operations or maintenance, warning nameplates must be provided on each shock during operations or maintenance, warning nameplates must be provided on each compartment door or auxiliary cubicle.

compartment door or auxiliary cubicle.

Data sheets are used to supply specific switchgear information to the manufacturer (when the Data sheets are used to supply specific switchgear information to the manufacturer (when the switchgear is ordered)

switchgear is ordered) and to Saudi Aramco (when tand to Saudi Aramco (when the switchgear is delhe switchgear is delivered). ivered). The data sheetsThe data sheets should contain information about the size, type,

should contain information about the size, type, ratings, and control of the ratings, and control of the low-voltage switchglow-voltage switchgear ear and the circuit breakers that are to be installed in the switchgear. The data sheets are provided in and the circuit breakers that are to be installed in the switchgear. The data sheets are provided in Work Aid 1.

Work Aid 1. Quality control, quality assurance, and test data Quality control, quality assurance, and test data should also be should also be provided with theprovided with the switchgear by the manufacturer.

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Circuit Breakers Circuit Breakers

Low-voltage power circuit breakers provide low-voltage system and load isolation during normal Low-voltage power circuit breakers provide low-voltage system and load isolation during normal operation

operation and mainand maintenance evoltenance evolutions. utions. Low-voltage pLow-voltage power circuiower circuit breakers t breakers also provialso providede automatic system fault isolation to prevent damage to connected equipment during overload, automatic system fault isolation to prevent damage to connected equipment during overload, abnormal, or faul

abnormal, or fault conditions. t conditions. Low-voltage power circuit breakerLow-voltage power circuit breakers that are used in Saudi Aramcos that are used in Saudi Aramco installations are designed, rated, manufactured, and tested in accordance with the latest issue or installations are designed, rated, manufactured, and tested in accordance with the latest issue or revision

revision of the of the cognizant sectcognizant sections of ions of ANSI/IEEE ANSI/IEEE Standard C37. Standard C37. Each component Each component of aof a low-voltage power circuit breaker must be fully capable of interrupting the available system low-voltage power circuit breaker must be fully capable of interrupting the available system short-circuit current that is indicated in the system engineering drawings. Each low-voltage circuit short-circuit current that is indicated in the system engineering drawings. Each low-voltage circuit breaker

breaker must must have have a a three-phase three-phase short short circuit circuit current current rating rating that that is is equal equal to, to, or or larger larger than, than, thethe rating of the switchgear assembly.

rating of the switchgear assembly.

The low-voltage circuit breakers that are used in Saudi Aramco installations should be the The low-voltage circuit breakers that are used in Saudi Aramco installations should be the dead-front, rem

dead-front, removable, drawout, air type. ovable, drawout, air type. Insulated case or molded case circuiInsulated case or molded case circuit breakers must nott breakers must not be

be used used in in the the place place of of power power circuit circuit breakers breakers in in low-voltlow-voltage age switchswitchgear gear instalinstallationslations. . SaudiSaudi Aramco uses the General Electric (GE) AK-type, the Westinghouse DS-type, and the ABB Aramco uses the General Electric (GE) AK-type, the Westinghouse DS-type, and the ABB KD-type

type low-voltage circuit low-voltage circuit breakers breakers in in switchgear switchgear installations. installations. The The minimum minimum mandatorymandatory requirements for the design and construction of a low-voltage circuit breaker are provided in requirements for the design and construction of a low-voltage circuit breaker are provided in Work Aid 1.

Work Aid 1. Genera

Generally, low-lly, low-voltage power voltage power circuit breaker ccircuit breaker contacts are ontacts are operated by operated by a stored-energy mecha stored-energy mechanisanismm in the form of springs; however, some low-voltage feeder breakers use manual operators. in the form of springs; however, some low-voltage feeder breakers use manual operators. Electrical operation of a low-voltage circuit breaker is used when the breaker is controlled Electrical operation of a low-voltage circuit breaker is used when the breaker is controlled remotely, and manual operation is used when the breaker is controlled locally. Main breakers remotely, and manual operation is used when the breaker is controlled locally. Main breakers (e.g

(e.g., ., incomer) incomer) are are usually usually electrically-operaelectrically-operated. ted. Feeder Feeder breakers breakers are are manually manually operated. operated. InIn electrically-operated breakers, the springs are electrically controlled through use of a charging electrically-operated breakers, the springs are electrically controlled through use of a charging motor that maintains

motor that maintains the closing springs in the closing springs in a charged state. a charged state. The closing springs The closing springs must developmust develop sufficient energy to close and latch the circuit breaker.

sufficient energy to close and latch the circuit breaker. Figure 2

Figure 2 shows an shows an example GE example GE AKR, manually-operated, low-voltage circuit AKR, manually-operated, low-voltage circuit breaker. breaker. TheThe breaker

breaker is is closed closed by by first first turning turning the the manual manual operation operation handle handle up up to to four four strokes strokes to to charge charge thethe closing springs.

closing springs. Once the charging springs are charged, the breaker is Once the charging springs are charged, the breaker is closed by operation of theclosed by operation of the close push-button.

close push-button. Some manually-operated low-voltage circuit breakers close Some manually-operated low-voltage circuit breakers close on the on the final strokefinal stroke of the

of the manual operation handle, and they manual operation handle, and they do not do not have a close have a close push-button. push-button. Some electrically-Some electrically-operated low-voltage circuit breakers do not have a

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Figure 2 shows one set

Figure 2 shows one set of breaker contacts of breaker contacts with the arc chute asswith the arc chute assembly removed. embly removed. When theWhen the breaker

breaker closes, the closes, the moving moving contacts close contacts close against the against the stationary contacts. stationary contacts. To To trip trip the the breaker, breaker, aa trip push-button is operated.

trip push-button is operated. Low-voltage breakers use a shunt coil triLow-voltage breakers use a shunt coil trip (or undervoltage relp (or undervoltage release)ease) device for remote tr

device for remote trip operations. ip operations. The low-voltage breaker The low-voltage breaker also uses a solid-also uses a solid-state, direct-actstate, direct-acting,ing, self-power

self-powered trip device. ed trip device. The trip device current trip levels arThe trip device current trip levels are set at the breaker, and a portablee set at the breaker, and a portable test instr

test instrument can be used to test each trument can be used to test each trip device setting. ip device setting. The nameplate contains lThe nameplate contains low-voltageow-voltage circuit breaker manufacturer, type, and rating information.

circuit breaker manufacturer, type, and rating information.

Figure 2:

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Low-voltage circuit breakers that are electrically operated must be equipped with the following: Low-voltage circuit breakers that are electrically operated must be equipped with the following:

•

• Motor-opMotor-operated, erated, stored-energy (e.g., springs) operstored-energy (e.g., springs) operating mechanism.ating mechanism. •

• Shunt trip coil (or undervoltage release) tripping mechanism.Shunt trip coil (or undervoltage release) tripping mechanism. •

• Trip push-button.Trip push-button. •

• Close push-button.Close push-button. •

• Manual closing spring charge operation handle.Manual closing spring charge operation handle. •

• Control devices (as indicated on Engineering drawings).Control devices (as indicated on Engineering drawings).

Figure 3 shows a closeup view of the low-voltage breaker contact structure for one phase of the Figure 3 shows a closeup view of the low-voltage breaker contact structure for one phase of the breaker with the arc chute ass

breaker with the arc chute assembly removed. The movable contembly removed. The movable contact arm opens and closes to makeact arm opens and closes to make contact between the movable

contact between the movable contacts and the statcontacts and the stationary contact. ionary contact. When the breaker is clWhen the breaker is closed, theosed, the main contacts and the arcing contacts are held against the movable contact via pressure from the main contacts and the arcing contacts are held against the movable contact via pressure from the contact springs on t

contact springs on the contact pivot point. he contact pivot point. As the breaker opens, tAs the breaker opens, the main contacts open fihe main contacts open first,rst, which is follow

which is followed by the arcing contacts. ed by the arcing contacts. Because the arc interrBecause the arc interrupting contacts open lasupting contacts open last, the arct, the arc that is formed

that is formed when the breaker opens is when the breaker opens is forced up the arc forced up the arc runner. runner. The number of main The number of main andand arcing contacts will vary

arcing contacts will vary based on the interrupting capability of based on the interrupting capability of the breaker. the breaker. The arcing contactsThe arcing contacts are easily differentiated from the main contacts because the arcing contacts angle out slightly are easily differentiated from the main contacts because the arcing contacts angle out slightly more than the main

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The removable metal frame that surrounds the low-voltage circuit breaker consists of the The removable metal frame that surrounds the low-voltage circuit breaker consists of the necessary circuit breaker bus disconnecting contacts, wheels, and interlocks for drawout necessary circuit breaker bus disconnecting contacts, wheels, and interlocks for drawout application.

application. The removable metal The removable metal circuit breaker fcircuit breaker frame allows rame allows the circuit the circuit breaker compartmentbreaker compartment door to be closed with the circuit breaker in the following four operational positions: connected, door to be closed with the circuit breaker in the following four operational positions: connected, test, disconnect,

test, disconnect, and fully and fully withdrawn (e.g., withdrawn (e.g., removed). removed). When a When a power circuit power circuit breaker isbreaker is padlocked, the breaker must not be able to be closed or moved to any other position.

padlocked, the breaker must not be able to be closed or moved to any other position.

Electrically- or manually-operated low-voltage circuit breakers use auxiliary devices. Auxiliary Electrically- or manually-operated low-voltage circuit breakers use auxiliary devices. Auxiliary devices are used for specific circuit breaker and electric power distribution system protection and devices are used for specific circuit breaker and electric power distribution system protection and control.

control. An example An example of a of a circuit breaker circuit breaker auxiliary device auxiliary device is is a position a position indicator. indicator. The positionThe position indicator is

indicator is mechanically connected to mechanically connected to the circuit the circuit breaker operating breaker operating mechanism. mechanism. An auxiliaryAn auxiliary contact is also

contact is also an auxiliary device. an auxiliary device. Auxiliary contacts consist of Auxiliary contacts consist of "a" (normally open) contacts "a" (normally open) contacts andand "b" (normally closed)

"b" (normally closed) contacts. contacts. Normally open "a" Normally open "a" contacts follow the contacts follow the position of position of the circuitthe circuit breaker (i.e., when the

breaker (i.e., when the circuit breaker contacts are closed, the circuit breaker contacts are closed, the "a" contacts are "a" contacts are closed). closed). NormallyNormally closed "b" contacts function the opposite to the position of the circuit breaker (i.e., when the closed "b" contacts function the opposite to the position of the circuit breaker (i.e., when the circuit breaker contacts are

circuit breaker contacts are closed, the "b" closed, the "b" contacts on the contacts on the auxiliary switch are auxiliary switch are open). open). AuxiliaryAuxiliary contacts are used predominantly in electrical distribution protective relaying and breaker control contacts are used predominantly in electrical distribution protective relaying and breaker control systems.

systems. An example of an auxiliary contact use is An example of an auxiliary contact use is a breaker "a" contact that is in a breaker "a" contact that is in series with theseries with the breaker

breaker trip trip coil. coil. The The "a" "a" contact contact is is only only closed closed when when the the breaker breaker is is closed. closed. The The breaker breaker "a""a" contact prevents the trip coil

contact prevents the trip coil from being energized unless the from being energized unless the breaker is closed. breaker is closed. Extra auxiliaryExtra auxiliary contacts must be

contacts must be provided by the provided by the manufacturemanufacturer for r for Saudi Aramco use. Saudi Aramco use. The extra The extra auxiliaryauxiliary contacts are in

contacts are in addition to those addition to those contacts that are contacts that are required for required for circuit breaker operatcircuit breaker operation andion and indication. An alarm switch must also be provided for remote indication of an automatic trip by a indication. An alarm switch must also be provided for remote indication of an automatic trip by a protective device.

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EVALUATING LOW-VOLTAGE SWITCHGEAR AND CIRCUIT BREAKERS UPON EVALUATING LOW-VOLTAGE SWITCHGEAR AND CIRCUIT BREAKERS UPON RECEIPT

RECEIPT

The installation of low-voltage switchgear and circuit breakers is a process that occurs over a The installation of low-voltage switchgear and circuit breakers is a process that occurs over a period

period of of time. time. The The instalinstallation lation begins begins with with an an identifidentified ied need need for for a a new new low-vollow-voltage tage power power distribution installation (e.g., a

distribution installation (e.g., a new facility). new facility). Power is necessary Power is necessary for the new for the new facility to ffacility to function,unction, so a

so a switchgear and circuit breaker installation switchgear and circuit breaker installation is designed. is designed. After the design After the design is approved, theis approved, the switchgear and

switchgear and circuit breakercircuit breakers are orders are ordered. ed. Once the swiOnce the switchgear and cirtchgear and circuit breakers cuit breakers areare received from the manufacturer, they must be evaluated to ensure that they are proper for the received from the manufacturer, they must be evaluated to ensure that they are proper for the installation.

installation. The purpose of The purpose of the evaluation is the evaluation is to verify to verify that correct low-voltage switchgear andthat correct low-voltage switchgear and circuit breakers were received from the manufacturer and that the proper installation circuit breakers were received from the manufacturer and that the proper installation specifications and parameters

specifications and parameters were met. were met. This section This section will describe will describe how low-voltage how low-voltage switchgear switchgear and circuit breakers are evaluated upon

and circuit breakers are evaluated upon receipt.receipt.

Visual Inspection Visual Inspection

When low-voltage switchgear and circuit breakers are received from the manufacturer, a visual When low-voltage switchgear and circuit breakers are received from the manufacturer, a visual inspection should be

inspection should be performed. performed. The purpose of The purpose of the visual the visual inspection is to inspection is to verify that verify that thethe switchgear and circuit breakers that were received from the manufacturer are in good physical switchgear and circuit breakers that were received from the manufacturer are in good physical condition and that all of t

condition and that all of the requested parts and acceshe requested parts and accessories are pressories are present. ent. Because of the damageBecause of the damage that can occur to the moving parts that are associated with low-voltage switchgear and circuit that can occur to the moving parts that are associated with low-voltage switchgear and circuit breakers duri

breakers during installating installation, only a on, only a cursory inspcursory inspection is performeection is performed at the d at the receivinreceiving point. g point. DuringDuring the cursory inspection, the inspection personnel look for obvious equipment damage and the cursory inspection, the inspection personnel look for obvious equipment damage and determine whether all necessary support equipment (e.g., racking lever, and technical manuals) determine whether all necessary support equipment (e.g., racking lever, and technical manuals) are present.

are present. A detailed inspection of A detailed inspection of the low-voltage switchgear and circuit breakers is the low-voltage switchgear and circuit breakers is performedperformed when they are completely installed at the site or facility.

when they are completely installed at the site or facility.

Verification Against Specifications Verification Against Specifications

When a new facility or facility modification is at the equipment installation stage, the design of the When a new facility or facility modification is at the equipment installation stage, the design of the installation has

installation has already been completed. already been completed. The type of The type of low-voltage switchgear and circuit breakerslow-voltage switchgear and circuit breakers that are selected for a specific power system should be shown in the drawings, prints, or that are selected for a specific power system should be shown in the drawings, prints, or specifications for

specifications for the installation. the installation. The purpose The purpose of verifying of verifying low-voltage switchgear and low-voltage switchgear and circuitcircuit breakers

breakers against against the the specifispecifications cations is is to to ensure ensure that that the the equipment equipment that that is is being being installinstalled ed meetsmeets Saudi Aramco and industry standards.

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Generally, the verification against specifications consists of a determination of whether the type Generally, the verification against specifications consists of a determination of whether the type and rating of the equipment that is to be installed matches the size and type of the equipment that and rating of the equipment that is to be installed matches the size and type of the equipment that is required for

is required for the installation. the installation. In some cases, this In some cases, this determination is accomplished by reading andetermination is accomplished by reading an electrical plan that

electrical plan that identifies the identifies the low-voltage switchgear and circuit breaker sizes and types. low-voltage switchgear and circuit breaker sizes and types. TheThe Engineer inspects the manufacturer

Engineer inspects the manufacturer's nameplate data on 's nameplate data on each switchgear compartment and each switchgear compartment and circuitcircuit breaker,

breaker, and and he he compares compares them them to to the the requirements on requirements on the the electrical plan electrical plan to to determine determine whether whether the correct equipment is being used.

the correct equipment is being used. In other situations, the In other situations, the Electrical Engineer must rely on hisElectrical Engineer must rely on his knowledge of the correct application of switchgear and circuit breakers sizes and types to knowledge of the correct application of switchgear and circuit breakers sizes and types to determine whether t

determine whether the correct equipment he correct equipment is being used. is being used. The data sheets that The data sheets that were used to order were used to order the switchgear fr

the switchgear from the om the manufacturer should also manufacturer should also be consulted. be consulted. Example switchgear data sheetsExample switchgear data sheets are provided i

are provided in Work Aid 1. n Work Aid 1. Any quality contAny quality control, qualitrol, quality assurance, and y assurance, and test data thatest data that aret are provided

provided with with the the low-voltage low-voltage switchgeaswitchgear r and and circuit circuit breakers breakers should should also also be be reviewed. reviewed. AA switchgear and circuit

switchgear and circuit breaker applications checklist is breaker applications checklist is provided in Work provided in Work Aid 1. Aid 1. The checklistThe checklist itemizes what should be included in the verification of low-voltage switchgear and circuit breakers itemizes what should be included in the verification of low-voltage switchgear and circuit breakers against specifications.

against specifications.

Low-Voltage Switchgear Nameplate Low-Voltage Switchgear Nameplate

All low-voltage switchgear that is used in Saudi Aramco power systems should have a nameplate All low-voltage switchgear that is used in Saudi Aramco power systems should have a nameplate that is

that is clearly visible clearly visible on the on the front of front of the switchgear. the switchgear. The nameplate should contain manufacThe nameplate should contain manufacturer- turer-type information.

type information. The information The information that describes that describes the type the type of switchgear should consist of switchgear should consist of theof the manufacturer's name,

manufacturer's name, the type the type designation, and designation, and the serial the serial number. number. Because switchgear Because switchgear maymay contain different assemblies at various voltages, nameplates should be present at each switchgear contain different assemblies at various voltages, nameplates should be present at each switchgear segment.

segment. In accordance with In accordance with ANSI C37, ANSI C37, the manufacturer and the manufacturer and rating information that rating information that shouldshould appear on the low-voltage switchgear nameplate should contain the following ratings:

appear on the low-voltage switchgear nameplate should contain the following ratings:

•

• Rated frequencyRated frequency •

• Rated maximum voltageRated maximum voltage •

• Rated insulation levelRated insulation level •

• Rated continuous currentRated continuous current •

• Rated short-time currentRated short-time current •

• Rated short-circuit currentRated short-circuit current

Low-voltage switchgear and electric power distribution systems are designed to operate at a Low-voltage switchgear and electric power distribution systems are designed to operate at a specific

specific frequency. frequency. Saudi Aramco Saudi Aramco electrical distribution systems are electrical distribution systems are designed to operate at designed to operate at 6060 Hz.

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Low-voltage switchgear is designed for and should be marked with the maximum voltage at Low-voltage switchgear is designed for and should be marked with the maximum voltage at which t

which the switchgear he switchgear can be can be applied. applied. The rated The rated maximum voltage levels maximum voltage levels of a of a low-voltagelow-voltage switchgear is the highest rms voltage for which the switchgear is designed, and the rated switchgear is the highest rms voltage for which the switchgear is designed, and the rated macimum voltage is

macimum voltage is the upper limit the upper limit for operation. for operation. The rated maximum The rated maximum voltage levels of voltage levels of low- low-voltage swit

voltage switchgear are 635 V, chgear are 635 V, 508 V, or 254 V. 508 V, or 254 V. The rated insThe rated insulation level ulation level of low-voltof low-voltageage switchgear at each maximum voltage rating is equal to the low-frequency one-minute withstand switchgear at each maximum voltage rating is equal to the low-frequency one-minute withstand voltage of 2.2 kV.

voltage of 2.2 kV.

Low-voltage switchgear is designed for and should be marked with the continuous current that Low-voltage switchgear is designed for and should be marked with the continuous current that the switchgear is capable of carrying and the fault current values that the switchgear is capable of the switchgear is capable of carrying and the fault current values that the switchgear is capable of interrupting

interrupting without damage without damage to the to the switchgearswitchgear. . Specific Specific current current ratings ratings for lofor low-voltagew-voltage switchgear are as follows:

switchgear are as follows:

•

• Rated Continuous Current at 60 Hz.Rated Continuous Current at 60 Hz. The rated contiThe rated continuous current nuous current at 60 Hz at 60 Hz isis

the amount of current that can be continuously carried by the switchgear primary the amount of current that can be continuously carried by the switchgear primary circuit components (e.g., buses, bus

circuit components (e.g., buses, bus connections) without exceeding switchgear connections) without exceeding switchgear equipment allowable

equipment allowable temperature ritemperature rise. se. Examples Examples of of switchgear equipment switchgear equipment areare primary or s

primary or secondary circecondary circuit componentuit components, insulats, insulation, and switchgear strion, and switchgear structuraluctural components.

components.

•

• The Rated Short-Time Current.The Rated Short-Time Current. The rated short-time current The rated short-time current is the desiis the designatedgnated

limit of available current at which the switchgear must interrupt the current within limit of available current at which the switchgear must interrupt the current within the required time at the rated maximum voltage. The required time is termed the the required time at the rated maximum voltage. The required time is termed the "rated short-time duty" and corresponds to two p

"rated short-time duty" and corresponds to two periods of one-half second currenteriods of one-half second current flow that are separated by a 15-second interval of zero

flow that are separated by a 15-second interval of zero current.current.

•

• The Rated Short-Circuit Current.The Rated Short-Circuit Current. The rated short The rated short circuit current circuit current of low-voltageof low-voltage

switchgear is the designated limit of available current at the rated maximum voltage switchgear is the designated limit of available current at the rated maximum voltage that the switchgear must be required to withstand for a period of no less than four that the switchgear must be required to withstand for a period of no less than four cycles (on a 60 Hz basis).

cycles (on a 60 Hz basis).

Circuit Breaker Nameplate Circuit Breaker Nameplate

All circuit breakers that are used in Saudi Aramco power systems should have a nameplate that is All circuit breakers that are used in Saudi Aramco power systems should have a nameplate that is clearly visible

clearly visible on the on the front of front of the breaker. the breaker. The nameplate The nameplate should contain circuit should contain circuit breaker breaker manufacturer-typ

manufacturer-type information. e information. The information that The information that describes the type describes the type of circuit of circuit breaker shouldbreaker should contain the manufacturer name, the type designation, and the serial number.

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In accordance with ANSI C37, the manufacturer and rating information that should appear on the In accordance with ANSI C37, the manufacturer and rating information that should appear on the circuit breaker nameplate should contain the following rating information:

circuit breaker nameplate should contain the following rating information:

•

• Rated frequencyRated frequency •

• Rated maximum voltageRated maximum voltage •

• Rated continuous currentRated continuous current •

• Rated short-circuit current at the rated maximum voltageRated short-circuit current at the rated maximum voltage •

• Rated short-circuit currentRated short-circuit current

Circuit breakers and electric power distribution systems are designed to operate at a specific Circuit breakers and electric power distribution systems are designed to operate at a specific frequency.

frequency. Saudi Aramco electrical distribution systems are designed to Saudi Aramco electrical distribution systems are designed to operate at 60 Hz.operate at 60 Hz.

Low-voltage circuit breakers are designed for and should be marked with the maximum voltage at Low-voltage circuit breakers are designed for and should be marked with the maximum voltage at which they can

which they can be applied. be applied. The rated maximum The rated maximum voltage of a voltage of a low-voltage circuit breaker is low-voltage circuit breaker is thethe highest rms voltage (three-phase or single-phase) at which the circuit breaker is designed to highest rms voltage (three-phase or single-phase) at which the circuit breaker is designed to perform.

perform. A A low-voltalow-voltage ge circuit circuit breaker breaker is is generally generally rated rated at at 635 635 V V (600 (600 V V for for a a fused fused circuitcircuit breaker), 508 V,

breaker), 508 V, or 254 V.or 254 V.

Circuit breakers are designed for and should be marked with the continuous current that the Circuit breakers are designed for and should be marked with the continuous current that the breaker is capable of

breaker is capable of carrying and the short-circuit fault current values that the breaker is carrying and the short-circuit fault current values that the breaker is capablecapable of interrupti

of interrupting without damage to thng without damage to the breaker. e breaker. Specific currenSpecific current ratings for lt ratings for low-voltage circuiow-voltage circuitt breakers are as fo

breakers are as follows:llows:

•

• Rated Continuous Current at 60 Hz.Rated Continuous Current at 60 Hz. The rated contiThe rated continuous current nuous current at 60 Hz at 60 Hz isis

the amount of current that

the amount of current that the low-voltage circuit breaker can continuously carrythe low-voltage circuit breaker can continuously carry without exceeding the allowable temperature rise.

without exceeding the allowable temperature rise.

•

• The Rated Short-Time Current.The Rated Short-Time Current. The rated short circuit The rated short circuit current is current is the designedthe designed

limit of available (prospective) rms current at which the circuit breaker will be limit of available (prospective) rms current at which the circuit breaker will be required to perform its

required to perform its short-time duty cycle at short-time duty cycle at the rated maximum voltage. the rated maximum voltage. TheThe short-time duty cycle is defined by ANSI 37.13 as two periods of 1/2 second short-time duty cycle is defined by ANSI 37.13 as two periods of 1/2 second current flow, which is

current flow, which is followed by a 15-second interval of zero followed by a 15-second interval of zero current. current. UnfusedUnfused low-voltage circuit breakers do not have a

low-voltage circuit breakers do not have a rated short-time current.rated short-time current.

•

• The Rated Short-Circuit Current at Each Rated Maximum VoltageThe Rated Short-Circuit Current at Each Rated Maximum Voltage

(Interrupting Rating).

(Interrupting Rating). The rated short circuit The rated short circuit current of an unfused lcurrent of an unfused low-voltageow-voltage circuit breaker is the designated limit of available current at which the circuit

circuit breaker is the designated limit of available current at which the circuit breaker must int

breaker must interrupt the currerrupt the current within the requient within the required time at the rated maxired time at the rated maximummum voltage.

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EVALUATING LOW-VOLTAGE SWITCHGEAR AND CIRCUIT BREAKER EVALUATING LOW-VOLTAGE SWITCHGEAR AND CIRCUIT BREAKER INSTALLATION AND TESTING

INSTALLATION AND TESTING

The process of determining whether low-voltage switchgear and circuit breakers should be The process of determining whether low-voltage switchgear and circuit breakers should be commissioned is to verify that all the electrical inspections and tests have been properly performed commissioned is to verify that all the electrical inspections and tests have been properly performed and to verify that the test results are within the specifications that are designated by the applicable and to verify that the test results are within the specifications that are designated by the applicable Saudi Aramco and industry standards.

Saudi Aramco and industry standards.

Installation inspections are performed to verify that proper switchgear and circuit breaker Installation inspections are performed to verify that proper switchgear and circuit breaker installation materials are used, that installation specifications and parameters are met, and that installation materials are used, that installation specifications and parameters are met, and that proper

proper installatinstallation ion procedures procedures are are followed. followed. The The installatinstallation ion inspection inspection is is conducted conducted to to ensureensure that the switchgear and associated circuit breakers will properly function once they are installed. that the switchgear and associated circuit breakers will properly function once they are installed. Electrical tests are performed to check the ability of switchgear and the associated circuit breakers Electrical tests are performed to check the ability of switchgear and the associated circuit breakers to function under a variety of operating conditions and loads. Installation tests should detect to function under a variety of operating conditions and loads. Installation tests should detect shipping or installation damage, gross manufacturing defects, or errors in workmanship or shipping or installation damage, gross manufacturing defects, or errors in workmanship or installation.

installation. The The Saudi Saudi Aramco Switchgear-General Pre-Commissioning Form Aramco Switchgear-General Pre-Commissioning Form (P-023) and (P-023) and thethe Saudi Aramco Low-Voltage Circuit Breaker Pre-Commissioning Form (P-008) contain guidance Saudi Aramco Low-Voltage Circuit Breaker Pre-Commissioning Form (P-008) contain guidance on the items that should be inspected, checked, and tested during the commissioning of on the items that should be inspected, checked, and tested during the commissioning of switchgear and low-voltage circuit breakers. The switchgear-general and low-voltage circuit switchgear and low-voltage circuit breakers. The switchgear-general and low-voltage circuit breaker pr

breaker pre-commise-commissioning fosioning forms are prorms are provided in Worvided in Work Aid 2.k Aid 2.

The proper evaluation of inspection and testing data during the commissioning process can The proper evaluation of inspection and testing data during the commissioning process can maximize the operating time of equipment installations through a determination of trends toward maximize the operating time of equipment installations through a determination of trends toward failure.

failure. Failure prediction can Failure prediction can drastically reduce equipment down-time; drastically reduce equipment down-time; if a if a failure is failure is predicted,predicted, operational changes can be made, maintenance can be performed, or equipment that is failing can operational changes can be made, maintenance can be performed, or equipment that is failing can be replaced

be replaced in a in a controllcontrolled manner. ed manner. If a If a problem is corrected before problem is corrected before it causes damage, it causes damage, operatingoperating costs will be lower because a malfunction can cause associated (or nearby) equipment damage and costs will be lower because a malfunction can cause associated (or nearby) equipment damage and disruption of service, or

disruption of service, or the problem can activate emergency repair crews. the problem can activate emergency repair crews. A failure in A failure in any one of any one of the many inspections, checks, or tests that are performed on a low-voltage switchgear and circuit the many inspections, checks, or tests that are performed on a low-voltage switchgear and circuit breakers during the

breakers during the instalinstallation and lation and testing evaluatiotesting evaluation n is sufficient to prevent is sufficient to prevent the equipment fromthe equipment from being co

being commismmissionesioned.d.

Visual Inspection Visual Inspection

Visual inspections are used to assess the physical condition of switchgear and the associated Visual inspections are used to assess the physical condition of switchgear and the associated circuit breakers.

circuit breakers. A visual A visual inspection is a inspection is a pass/fail verification about pass/fail verification about a particular aspect a particular aspect of theof the physical

physical condition condition or or the the operation operation of of equipment. equipment. Because Because the the criteria criteria that that are are establisheestablished d toto determine the acceptability of the visual inspections can be subjective, the visual inspections determine the acceptability of the visual inspections can be subjective, the visual inspections should be performed by an experienced Electrical Engineer.

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Because of the large number of inspection items that are associated with low-voltage switchgear Because of the large number of inspection items that are associated with low-voltage switchgear and circuit breakers, there

and circuit breakers, there are several courses are several courses of action for of action for visual inspection failure. visual inspection failure. The courseThe course of action to be taken depends

of action to be taken depends on the part of the equipmon the part of the equipment that failed thent that failed the visual inspecte visual inspection. ion. AA failure of alignment, mechanism/linkage, lubrication, or cleanliness inspection can usually be failure of alignment, mechanism/linkage, lubrication, or cleanliness inspection can usually be corrected through

corrected through maintenance procedures. maintenance procedures. A physical A physical damage or damage or suitability inspection suitability inspection failurefailure will probably require the replacement of the damaged component.

will probably require the replacement of the damaged component.

The visual inspection of circuit breakers should be performed during the normal breaker The visual inspection of circuit breakers should be performed during the normal breaker maintenance cycle as determined by Saudi Aramco procedures or once every 2,000 circuit breaker maintenance cycle as determined by Saudi Aramco procedures or once every 2,000 circuit breaker operations if the circuit breaker short-circuit interrupting rating does not exceed 29 kA in operations if the circuit breaker short-circuit interrupting rating does not exceed 29 kA in accordance with ANSI C37.06.

accordance with ANSI C37.06. Technical data to evaluate the resulTechnical data to evaluate the results of the visual inspectts of the visual inspection canion can be

be found found in in the the switchswitchgear gear and and circuit circuit breaker breaker manufactmanufacturer's urer's technical manual. technical manual. The The followfollowinging visual inspections are used to assess the condition of low-voltage switchgear and the associated visual inspections are used to assess the condition of low-voltage switchgear and the associated circuit breakers in Saudi Aramco systems:

circuit breakers in Saudi Aramco systems:

•

• SuitabilitySuitability •

• Physical DamagePhysical Damage •

• AlignmentAlignment •

• CleanlinessCleanliness •

• Arc Chute AssemblyArc Chute Assembly • • ContactsContacts • • Mechanism/LinkageMechanism/Linkage • • LubricationLubrication Suitability Suitability

The purpose of the visual inspection for suitability is to determine whether the switchgear and The purpose of the visual inspection for suitability is to determine whether the switchgear and associated circuit breakers are appropriate for the application in which they are placed. Under associated circuit breakers are appropriate for the application in which they are placed. Under normal circumstances, the suitability of the equipment should be determined before it is placed normal circumstances, the suitability of the equipment should be determined before it is placed into the system; however, a visual inspection should be performed to ensure that changes that may into the system; however, a visual inspection should be performed to ensure that changes that may have been made to the system have not exceeded the ratings of the switchgear or the associated have been made to the system have not exceeded the ratings of the switchgear or the associated circuit breakers.

circuit breakers.

To determine the suitability of switchgear and the associated circuit breakers, a visual inspection To determine the suitability of switchgear and the associated circuit breakers, a visual inspection of the nameplate data should be performed and compared to the electrical system single line of the nameplate data should be performed and compared to the electrical system single line diagram.

diagram. For example, if For example, if the nameplate information on the nameplate information on a circuit a circuit breaker does not breaker does not match thematch the ratings of the electrical system, the circuit breaker should be replaced with a circuit breaker that is ratings of the electrical system, the circuit breaker should be replaced with a circuit breaker that is correctly rated.