Commissioning Motor Control Centers

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

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

Chapter : Electrical For additional information on this subject, contactFile Reference: EEX30204 W.A. Roussel on 874-6160

Engineering EncyclopediaSaudi Aramco DeskTop Standards

Commissioning Motor Control Centers

Engineering Encyclopedia Electrical


Saudi Aramco DeskTop Standards

Content Page

INTRODUCTION................................................................................................................ 1

SAUDI ARAMCO REQUIREMENTS................................................................................. 2

Low Voltage ............................................................................................................. 2

Medium Voltage........................................................................................................ 4

EVALUATING MOTOR CONTROL CENTERS UPON RECEIPT.................................... 6

Visual Inspection....................................................................................................... 6

Verification Against Specification.............................................................................. 6

EVALUATING MOTOR CONTROL CENTER INSTALLATION AND TESTING........... 9

Visual Inspections ..................................................................................................... 9

Suitability .....................................................................................................10

Physical Damage...........................................................................................11

Alignment .....................................................................................................11

Cleanliness....................................................................................................11

Contactor/Controller Mechanism ..................................................................12

Lubrication ...................................................................................................12

Mechanical Inspections.............................................................................................12

Bolt Torque ..................................................................................................13

Open/Close Operation...................................................................................13

Main Contact Check .....................................................................................13

Door Operation ............................................................................................14

Electrical Inspections and Tests ................................................................................14

Point-to-Point Wiring ...................................................................................15

Megger.........................................................................................................15

Contact Resistance........................................................................................16

DC High-Pot ................................................................................................16




SYSTEM PRE-OPERATIONAL CHECK-OUT .................................................................18

SYSTEM OPERATIONAL CHECK-OUT..........................................................................19

WORK AID 1: REFERENCES FOR EVALUATING MOTORCONTROL CENTERS UPON RECEIPT..................................................20

Work Aid 1A: MCC Applications Checklist..............................................................20

Work Aid 1B: Low Voltage MCC Ratings ...............................................................20

Work Aid 1C: Low Voltage MCC Terminal Board Wiring .......................................21

Work Aid 1D: Minimum Low Voltage Indoor Motor Control CenterTechnical Requirements.....................................................................22

Work Aid 1E: Medium Voltage MCC Ratings..........................................................32

Work Aid 1F: Medium Voltage MCC Requirements.................................................33

WORK AID 2: REFERENCES FOR EVALUATING MOTORCONTROL CENTER INSTALLATION AND TESTING.........................40

Work Aid 2A: MCC Commissioning Electrical Test Values......................................40

Work Aid 2B: Information, Formulas, and Tables for Use in Evaluatingthe Results of Insulation Resistance (Megger) Tests ..........................41

Work Aid 2C: Information, Formulas, and Tables for Use in Evaluatingthe Results of DC Hi-Pot Tests..........................................................42

Work Aid 2E: Excerpts from GI 2.710 .....................................................................50

GLOSSARY........................................................................................................................54




Table of Figures Page

Figure 1: Typical Low Voltage MCC ...................................................................... 4

Figure 4: Low Voltage MCC Terminal Board Wiring Type Features(From NEMA ICS 2-322) .......................................................................21

Figure 4: Low Voltage MCC Terminal Board Wiring Type Features(From NEMA ICS 2-322) (Cont'd) .........................................................22

Figure 5: Saudi Aramco Low Voltage MCC General Requirements(From 16-SAMSS-503) ..........................................................................23

Figure 6: Saudi Aramco Low Voltage MCC Construction Requirements(From 16-SAMSS-503) ..........................................................................24

Figure 6: Saudi Aramco Low Voltage MCC Construction Requirements(From 16-SAMSS-503) (Cont'd).............................................................25

Figure 7: Saudi Aramco Low Voltage MCC Enclosure and IsolatingPanel Requirements (From 16-SAMSS-503) ...........................................26

Figure 8: Saudi Aramco Low Voltage MCC Bus and Space HeaterRequirements (From 16-SAMSS-503) ....................................................27

Figure 8: Saudi Aramco Low Voltage MCC Bus and Space HeaterRequirements (From 16-SAMSS-503) (Cont'd).......................................28

Figure 9: Saudi Aramco Low Voltage MCC Nameplates, Wiring, andMiscellaneous Equipment Requirements (From 16-SAMSS-503) ............29

Figure 9: Saudi Aramco Low Voltage MCC Nameplates, Wiring, andMiscellaneous Equipment Requirements (From 16-SAMSS-503)(Cont'd) ..................................................................................................30

Figure 10: Data Schedule for Low Voltage Switchracks and MCCs(From 16-SAMSS-503) ..........................................................................31

Figure 11: Ratings for Class E2 (Fused) Medium Voltage Motor Controllers(From SADP-P-116 and NEMA ICS 2-324) ...........................................32

Figure 12: Saudi Aramco Medium Voltage MCC General Requirements(From 16-SAMSS-506) ..........................................................................33

Figure 13: Saudi Aramco Medium Voltage MCC Construction and Design(From 16-SAMSS-506) ..........................................................................34

Figure 13: Saudi Aramco Medium Voltage MCC Construction andDesign Requirements (From 16-SAMSS-506) (Cont'd) ...........................35




Figure 14: Saudi Aramco Medium Voltage MCC Enclosure andIsolating Panel Requirements (From 16-SAMSS-506).............................35

Figure 15: Saudi Aramco Medium Voltage MCC Bus and SpaceHeater Requirements (From 16-SAMSS-506) .........................................36

Figure 16: Saudi Aramco Medium Voltage MCC Nameplates, Wiring, andMiscellaneous Equipment Requirements (From 16-SAMSS-506) ............37

Figure 16: Saudi Aramco Medium Voltage MCC Nameplates,Wiring, and Miscellaneous Equipment Requirements(From 16-SAMSS-506) (Cont'd).............................................................38

Figure 16: Saudi Aramco Medium Voltage MCC Nameplates,Wiring, and Miscellaneous Equipment Requirements(From 16-SAMSS-506) (Cont'd).............................................................39

Figure 17: Dielectric Absorption Ratio Chart ...........................................................41

Figure 18: Example of DC Hi-Pot Test (Good and Bad Insulation) ..........................42

Figure 19: Saudi Aramco Pre-Commissioning Form, P-018,Motor Control Centers............................................................................44

Figure 19: Saudi Aramco Pre-Commissioning Form, P-018,Motor Control Centers (Cont'd) ..............................................................45





Figure 20: GI 2.710 Excerpt ....................................................................................51

Figure 20: GI 2.710 Excerpt (Cont'd).......................................................................52

Figure 20: GI 2.710 Excerpt (Cont'd).......................................................................53



Saudi Aramco DeskTop Standards 1

INTRODUCTION

Motor control centers (MCCs) are used when the centralized control of a number of motors ispossible and desired. MCCs function as a control location in which branch circuit incoming andoutgoing lines are marshalled. The modular designs of MCCs allow for convenient motor controlgrouping that provides conservation of space and construction flexibility. Once the MCC for agiven installation is chosen, the MCC is ordered, shipped, received, inspected, installed, and testedduring the commissioning process. The commissioning process for MCCs in Saudi Aramcofacilities ensures that a safe and cost-effective system is installed that performs to thespecifications of the facility for the projected operating lifetime of the facility. Experience hasshown that the time and effort that is expended up front to ensure safety, quality control, andadherence to Saudi Aramco and industry standards minimize subsequent equipment failure.

The MCC commissioning process involves evaluations, verifications, and checks that determinewhether the proper MCC specifications and installation requirements are met. Tests are alsoperformed to determine whether the electric power distribution system will operate properly andsafely after the MCC installation. When the MCC is inspected and tested satisfactorily during thecommissioning process, the system should operate in accordance with manufacturer'sspecifications for its maximum useful life.

This Module provides information on the following topics that are pertinent to commissioningmotor control centers for Saudi Aramco installations:

• Saudi Aramco Requirements

• Evaluating Motor Control Centers Upon Receipt

• Evaluating Motor Control Center Installation and Testing

• System Pre-Operational Check-Out

• System Operational Check-Out




SAUDI ARAMCO REQUIREMENTS

Large process and process support equipment relies on motors for primary and ancillary functionsthroughout the manufacturing process (e.g., fans, circulation pumps, and blowers). The motorpower distribution, protection, and control equipment that is contained in an MCC are small butimportant parts of the electric power system. It is usually advantageous to group motorcontrollers at an MCC, which saves space, simplifies cabling, and frequently makes it possible toinstall the control equipment in an air-conditioned room. For Saudi Aramco installations, it ispreferable to group controllers in a substation or control room instead of on switchracks that arelocated in hazardous areas. An MCC provides centralized power distribution and control of agroup of motors. Centralized motor control eliminates

the need for trips to local control stations for equipment startups and shutdowns. Convenientgrouping of motor control circuits at an MCC also reduces the installation costs. Westinghouse,Powell, and GE-type motor control centers utilizing Westinghouse and GE vacuum starters are anexample of some of the MCCs used in Saudi Aramco installations.

In Saudi Aramco installations, MCCs are grouped into two voltage levels: low voltage (0-600 V)and medium voltage (2400 and 4160 V). This section of the Module contains information onSaudi Aramco low and medium voltage MCC requirements.

Low Voltage

To commission low voltage MCCs, it is important for the commissioning engineer to be familiarwith the requirements for MCCs that are used in Saudi Aramco installations. This section willbriefly describe general Saudi Aramco low voltage MCC requirements. Due to the environmentalconditions in Saudi Aramco installations, the only outdoor low voltage MCCs that are allowed arethose MCCs that are of the switchrack construction. Specific Saudi Aramco low voltage MCCrequirements (e.g., enclosure and bus requirements) are provided in Work Aid 1.

NEMA ICS 2-322 classifies low voltage MCCs into the following two classes: Class I and ClassII. Class I MCCs consist of a group of combination starters or controllers that are operationallyindependent. These starters or controllers do not include interlocking or control connectionsbetween units. Class II MCCs consist of a group of combination starters or controllers that areoperationally related to each other for specific applications (e.g., sequence control). Class IIMCCs include interlocking and control wiring between units.




Class I or Class II low voltage MCCs that are used in Saudi Aramco installations must be rigid,free-standing, metal-enclosed structures that are designed in accordance with NEMA Class I,Type B. Figure 1 shows a typical low voltage MCC. Low voltage MCCs consist of verticalsections that are assembled into a group. Because low voltage MCCs that are used in SaudiAramco installations must be suitable for back-to-wall or back-to-back mounting, they shouldonly contain front-mounted equipment (e.g., breakers, controllers, and switches). Each verticalsection grouping has a common power bus and that forms an enclosure to which additionalsections may readily be added. Each MCC vertical section is subdivided into compartments thatcontain the various control and protective devices. Field rearrangement of MCC compartmentsinto any possible combination is accomplished through use of simple fasteners, such as bolts andscrews. The line side of MCC incomers must be provided with meters (e.g., ammeters andvoltmeters).

All control and protective devices that are installed in the MCC are selected so that they willoperate properly in the designated atmosphere without further protection. To preventoverheating, MCCs are fitted with ventilation openings that are filtered or screened to prevent theentrance of rodents and other foreign matter. Control device assemblies are arranged so theassemblies can be removed for maintenance or repair without deenergizing the MCC (e.g., plug-inline connections). Although fuses are an integral part of the control and protective device designin most industrial installations, circuit breakers are preferred over fuses for Saudi Aramcoinstallations because of the inherent single-phasing characteristics of fuses. Saudi Aramcopractice does not normally include the use of capacitors that are directly connected to theterminals of motors or motor control centers on low voltage systems.




Figure 1: Typical Low Voltage MCC

Medium Voltage

This section will briefly describe general Saudi Aramco medium voltage MCC requirements.Specific Saudi Aramco medium voltage MCC requirements (e.g., construction and designrequirements) are provided in Work Aid 1.




NEMA Class E1 controllers and starters are not used in Saudi Aramco installations because oftheir inherently low short-circuit interrupting ratings. NEMA Class E2 controllers are used formedium voltage motors (2300 V and 4000 V motors) up through 1100 kW (4000 hp). Class E2starters and controllers can be grouped to form motor control centers if the fault level does notexceed the interrupting capacities that are listed in Figure 11 of Work Aid 1; however, controllersshould not be fabricated back-to-back or stacked over one-high. Two-high arrangements werepreviously allowed; however, only one-high controllers are now allowed.

NEMA Class E2 controller fuses should be carefully chosen to ensure optimum coordination withthe overload relays and the relays of other breakers on the system. A static motor protection(multi-function) relay that provides protection against single phasing should be specified andimplemented because NEMA standard ICS does not require the fuses to open all three phases. Ifthe fuses in all three phases do not open when a fault occurs, single phasing is possible.

In addition to the protection mentioned above, the medium voltage MCCs should include groundfault relaying. A disconnect should also be provided for each starter as a means of isolating themain contactor. Individual control power transformers must provide a source of control powerfor each circuit within the MCC. Each motor control center bus must have a voltmeter with aselector switch, and each incoming supply feeder must have an ammeter with a selector switch. Acircuit for motor space heating should be provided for each motor circuit that is powered from theMCC. Each motor space heating circuit should have a separate molded case circuit breaker.

Additionally, the following items can also be accommodated in an MCC, if required:

• A starting reactor, or auto-transformer, that is used for control during reducedvoltage motor starting.

• A group surge protection device for the motor control bus.

• A test source of ac control power that is to be used during controller testing.

• A method for excitation control of synchronous motors. (Excitation control isnormally provided as a separate unit.)




EVALUATING MOTOR CONTROL CENTERS UPON RECEIPT

The installation of motor control centers (MCCs) is a process that occurs over a period of time.MCCs usually supply power to the motors and pumps that form the base of the manufacturing orrefining process. The MCC installations begin with an identified need for pump and motor powerdistribution and control centers in a new facility. After the facility design is approved, the MCCsare ordered from the manufacturer. When the MCCs are received from the manufacturer, theymust be evaluated to ensure that they are proper for the installation. The purpose of theevaluation is to verify that correct MCCs were received from the manufacturer and that theproper equipment specifications and parameters were met. This section will describe how MCCsare evaluated upon receipt.

Visual Inspection

When MCCs are received from the manufacturer, a visual inspection should be performed. Thepurpose of the visual inspection is to verify that the MCC components (e.g., controllers andindicating lights) that were received from the manufacturer are in good physical condition and thatall of the requested parts and accessories are present. Because damage can occur to the movingparts associated with controllers installed in MCCs, only a cursory inspection is performed at thereceiving point. During the cursory inspection, the inspection personnel look for obviousequipment damage and determine whether all necessary support equipment is present. A detailedinspection of the MCCs is performed when they are completely installed at the site or facility.

Verification Against Specification

When a new facility or facility modification is at the equipment installation stage, the design of theinstallation has already been completed. The type, the size, and the configuration of the MCCthat is selected for a specific power system should be shown in the drawings, the prints, or thespecifications for the installation. The purpose of verifying MCCs against the specifications is toensure that the equipment that is being installed meets Saudi Aramco and industry standards.

Generally, the verification against specifications consists of a determination of whether the typeand rating of the equipment that is to be installed match the size and type of the equipment that isrequired for the installation. In some cases, this determination is accomplished by reading anelectrical plan that identifies the MCC type, the size, and the configuration.




During the verification against specifications, the Engineer inspects the manufacturer's nameplatedata on each MCC compartment and compares them to the requirements on the electrical plan todetermine whether the correct equipment is being used. In other situations, the ElectricalEngineer must rely on his knowledge of the correct application of MCCs to determine whetherthe correct equipment is being used. The data sheets that were used to order the MCC from themanufacturer should also be consulted. An example MCC data sheet is provided in Work Aid 1.Any quality control, quality assurance, and test data that are provided with the MCC should alsobe reviewed.

MCCs that are used in Saudi Aramco power systems should have a nameplate that is clearlyvisible on the front of the MCC. The nameplate should contain manufacturer-type information.The information that describes the MCC should consist of the manufacturer's name, the typedesignation (if applicable), and the serial number. Because MCCs may contain different verticalassembly compartments (e.g., controllers) that use control and indicating equipment at variousvoltages, nameplates should be present at each MCC compartment. Electric power distributionsystem MCCs are designed to operate at a specific frequency. Saudi Aramco electricaldistribution systems are designed to operate at 60 Hz. Medium voltage MCC controller ratingsshould be in accordance with the table that is provided in Figure 11 of Work Aid 1.

Because there are different terminal board arrangements in low voltage MCCs, NEMA ICS 2-322provides for the different types of terminal board wiring that are required in accordance with thearrangement of the terminal boards. The different types of terminal board wiring are designatedType A, Type B, and Type C. Low voltage MCC power and control leads should be arranged inaccordance with Type B. The features that are required by NEMA for Type A, Type B, and TypeC are provided in Work Aid 1.

MCC bus capacity should be computed through use of the normal full-load current of the largestmotor that is supplied by the MCC, all other motors that can be operated at the same time, otherloads supplied by the MCC, and future MCC load requirements. The incoming feeder of a lowvoltage MCC should be provided with a switching device (unless a switching device is alreadyprovided at the source of the incoming feeder and it is readily accessible). For low voltageMCCs, the basis for computing the low voltage MCC bus capacity is provided in Work Aid 1.The total MCC bus capacity should be less than the continuous current rating of the mainincoming circuit breaker or the fan-cooled current rating of the power source transformer(whichever is most restrictive).




The low voltage MCC short-circuit rating should not be less than 105% of the maximumavailable rms symmetrical current available at the MCC line terminals. The short-circuitinterrupting rating of the series combination of the MCC component (e.g., circuit breaker,contactor, or thermal overload relay heaters) should be a minimum of 22,000 amperes rmssymmetrical. Short circuits are to be computed as the sum of the short-circuit currentcontributions of the motors that are connected to the motor control center and all othershort-circuit current contributions of the supply system at the point of connection to the motorcontrol center.




EVALUATING MOTOR CONTROL CENTER INSTALLATION AND TESTING

MCCs are commissioned to verify that they have been electrically and mechanically assembled andtested and that they conform to the specifications that are designated by the applicable SaudiAramco and industry standards.

Installation inspections are performed to verify that proper MCC installation materials are used,that installation specifications and parameters are met, and that proper installation procedures arefollowed. The installation inspection is conducted to ensure that MCCs will properly functiononce they are installed. Electrical tests are performed to check the ability of MCCs to functionunder all operating conditions and loads. Installation tests should detect shipping or installationdamage, gross manufacturing defects, or errors in workmanship or installation. Saudi AramcoPre-Commissioning Form P-018, Motor Control Centers, contains guidance on the items thatshould be inspected, checked, and tested during the commissioning of MCC installations. SaudiAramco Pre-Commissioning Form P-018, Motor Control Centers, is provided in Work Aid 2.

The proper evaluation of inspection and testing data during the commissioning process canmaximize the operating time of equipment installations by providing a database for equipment thatcan be used in the future for a determination of trends towards failure. Failure prediction candrastically reduce equipment down-time; if a failure is predicted, operational changes can bemade, maintenance can be performed, or equipment that is failing can be replaced in a controlledmanner. If a problem is corrected before it causes damage, operating costs will be lower becausea malfunction can cause associated (or nearby) equipment damage and disruption of service, orthe problem can activate emergency repair crews. A failure in any one of the many inspections,checks, or tests that are performed on MCCs during the installation and testing evaluation issufficient to prevent the MCC from being commissioned.

Visual Inspections

Visual inspections are used to assess the physical condition of MCCs. A visual inspection is apass/fail verification about a particular aspect of the physical condition or the operation ofequipment. Because the criteria that are established to determine the acceptability of the visualinspections can be subjective, the visual inspections should be performed by an experiencedElectrical Engineer. Visual inspection items are listed in Saudi Aramco Pre-Commissioning FormP-018, Motor Control Centers. Form P-018 is provided in Work Aid 2.




Because of the large number of inspection items that are associated with MCCs, several coursesof action are available for visual inspection failure. The course of action depends on the part ofthe equipment that failed the visual inspection. A failure of indicating lights or switches cangenerally be corrected through component replacement. For example, a failure ofcontactor/controller mechanism inspection or cleanliness inspection can usually be correctedthrough maintenance procedures. A physical damage or suitability inspection failure will probablyrequire the replacement of the damaged component. The following visual inspections are used toassess the condition of MCCs in Saudi Aramco systems:

• Suitability

• Physical Damage

• Alignment

• Cleanliness

• Contactor/Controller Mechanism

• Lubrication

Suitability

The purpose of the suitability visual inspection is to determine whether the MCC and theequipment that is contained in the MCC are appropriate for the application. Under normalcircumstances, the suitability of the equipment should be determined before the equipment isplaced into the system; however, a visual inspection should be performed to ensure that changesthat may have been made to the system have not exceeded the voltage and current ratings of thecircuit breakers, the contactors, and the fuses that are present in the MCC.

To determine the suitability of the MCC, a visual inspection of the nameplate data should beperformed and compared to the electrical system single line diagram. For example, if thenameplate information on a controller does not match the ratings of the electrical system diagram,the controller should be replaced with a controller that is correctly rated.




Physical Damage

Physical damage to the MCC or to that equipment that is contained in the MCC can lead to MCCor controller failure during critical system operations. The magnitude of the electric energy thatpasses through MCCs can propagate and amplify any minor installation damage. Damage toMCCs can lead to catastrophic equipment failure, fire, personal injury, or death. Any physicaldamage to MCCs that is noted requires the immediate replacement of the damaged component.The most obvious and common forms of physical damage are cracks, dents, missing or brokenpieces, bent doors, and burned-out indicator lights. The purpose of the physical damageinspection is to identify whether corrective maintenance or component replacement is necessary.MCCs that show any form of physical damage, no matter how small, should be determined tohave failed the physical damage inspection.

Alignment

The purpose of the alignment inspection is to ensure that the MCCs will properly pass currentwhen they are installed in the electrical system between the power distribution cabinets and themotor loads. Proper alignment of a controller draw-out cubicle frame will ensure that thecontroller is properly connected to the system when it is installed in the MCC. Stab fingertightness and alignment are also checked during the alignment visual inspection of MCCs.Improper alignment can cause uneven component heating and wear. Due to the construction ofcontroller or contactor draw-out cubicle frames, frames that are out of alignment are usuallyvisually obvious.

Cleanliness

The purpose of the cleanliness visual inspection is to ensure the proper operation of the MCCover the maximum operating life of the equipment. The accumulation of dirt over a period oftime will impede the proper operation of the equipment (e.g., controllers) that is contained in theMCC and will reduce the dielectric strength of the MCC insulation. Dust and dirt can also reducethe speed and sensitivity of a controller or contactor under fault conditions.

The accumulation of heavy amounts of dust and dirt should be cleaned away from the draw-outcubicles and wireways of an MCC during maintenance cycles. MCCs that are installed inextremely dirty, dusty, or humid areas may have to be cleaned more often than once during eachmaintenance cycle.




Contactor/Controller Mechanism

The mechanism assembly of a contactor or controller that is contained in an MCC performs theactual movement of the contacts to supply power to or to remove power from a motor or pump.The purpose of the contactor/controller mechanism inspection is to ensure that moving parts inthe contactor/controller operate properly. Proper operation of the contactor/controllermechanism will ensure that the MCC will supply the proper distribution and control for theconnected motor circuits. The inspector should visually determine that no obstructions exist thatwill impede the movement of the contactor/controller mechanism.

Lubrication

The lubrication visual inspection should be performed in conjunction with the contactor/controllermechanism visual inspection. The purpose of the lubrication visual inspection is to ensure that themoving parts of the contactor/controller mechanisms are properly lubricated and free of rust.

Before the application of new lubrication can occur, hardened grease, dirt, and rust should beremoved from the surfaces that require lubrication. A cloth that is dampened with keroseneshould be used to remove the hardened grease and dirt. Care must be taken to ensure that thecloth does not deposit fibers on the moving parts of contactor/controller. The deposit of clothfibers on the moving parts can cause subsequent improper mechanism operation. After the properpreparation of the moving parts, a thin layer of lubrication should be applied. Excess lubricationshould be wiped off with a clean cloth.

Mechanical Inspections

A mechanical inspection is used to assess the ability of the MCC and the enclosed equipment tophysically perform the mechanical movements that are necessary for proper operation. Tests arealso performed during the mechanical inspection to assess MCC safety functions (e.g., breakertrips). Mechanical inspection items are listed in Saudi Aramco Pre-Commissioning Form P-018,Motor Control Centers. Form P-018 is provided in Work Aid 2. Because of the number ofmechanical inspection items that are associated with MCCs, there are several courses of action fora mechanical inspection failure. The course of action depends on the part of the equipment thatfailed the inspection. A failure of mechanism operation can usually be corrected throughmaintenance procedures. For example, a bolt torque test failure can be corrected throughadjustment of the bolts with a torque wrench.




The following general mechanical inspections and tests are performed on MCCs that are installedin Saudi Aramco systems:

• Bolt Torque

• Open/Close Operation

• Main Contact Check

• Door Operation

Bolt Torque

The purpose of a bolt torque inspection is to ensure that enough force is present to hold thebuswork and cubicle frames in place during normal controller or contactor operations and duringfault conditions. To determine the amount of force that exists at a bolt, a torque wrench isapplied to the bolt in the direction that will tighten the bolt, and the amount of torque is read.Torque values for MCCs are provided in Saudi Aramco Pre-Commissioning Form P-018, MotorControl Centers, that is provided in Work Aid 2. The manufacturer of the MCC will also providea list of acceptable torques in the MCC technical manual.

Open/Close Operation

Some MCC contactors or controllers in Saudi Aramco electrical systems can go for long periodsof time between operations. A contactor or controller must always be in a condition to operateno matter how infrequently the motor or pump is being used. The purpose of the open/closeoperation is to check the operation of the breakers and contactors to ensure the freedom ofmovement of all moving parts. During opening and closing operations, the mechanical conditionof all auxiliary devices, bumpers, position indicators, latching, tripping, and operating mechanismsis checked for proper operation.

Main Contact Check

A check of the main contacts is performed in conjunction with the open/close operation check.The check of the main contacts consists of a pressure check, a contact alignment check, and acheck of the full contact area on contactors. The pressure check is performed to ensure that thecorrect pressure is maintained at the main contact. The correct pressure at the main contacts isnecessary to provide a low resistance current path when the MCC is supplying power to a pumpor motor. The contact alignment and full contact area checks are performed to maximize thecontact surface area at the main contact face. Maximizing the contact surface will provide thelowest resistance in the current path.




Door Operation

Each switchgear circuit breaker compartment must be provided with a door (safety barrier). Thedoor should be provided with a latch that completely closes the compartment when the controlleror contactor cubicle is completely installed or removed. The door should have a locking bar tohold the door open. The door should also contain an interlock that prevents the closure of thedoor unless the cubicle is completely installed or removed.

During the mechanical inspection, each cubicle compartment door operating mechanism should bemechanically operated during the mechanical inspection, and the door interlocks (e.g., breakertrips) should be tested.

Electrical Inspections and Tests

During the commissioning process, electrical inspections and tests are performed to check theability of MCCs to operate for a reasonable future period of time under all operating conditionsand loads. Acceptance or installation tests will usually detect shipping or installation damage andgross defects or errors in workmanship in equipment construction. Once the installation andinspection data have been recorded and assembled, a methodical and consistent program ofperiodic data collection and evaluation should be established. As each new maintenance item,test, splice, system addition, or system reconfiguration occurs, new inspections and data recordswill be required and should be added to the existing data on file.

Because an electrical inspection or test failure can be caused by a design flaw, construction error,equipment age, or operational misuse, some type of troubleshooting or maintenance activityshould be performed on the faulty equipment. For example, a contact resistance test failure canbe rectified by cleaning the contacts to remove carbon buildup or by replacing the contacts. Someelectrical inspection or test failures are not repairable, and they will require the replacement of theequipment before the MCC can be commissioned. For example, an insulation resistance testfailure usually indicates a gross imperfection in the cable, the bus, or the circuit breaker insulation.

The following electrical inspections, checks, and tests are performed on MCCs:

• Point-to-Point Wiring

• Megger

• Contact Resistance

• DC High-Pot




Point-to-Point Wiring

Point-to-point wiring checks are performed to verify that MCCs comply with Saudi Aramcowiring diagrams and manufacturer's specifications. Terminations and terminal blocks within theMCC are also checked for routing and labeling. During the point-to-point wiring checks, controland metering transformers and fuses (if they are present) are checked for proper application andtype. If necessary, adjustments are made to components such as relays, annunciators, alarms, andtargets.

Megger

The purpose of the insulation resistance megger test is to directly measure the insulationresistance of the MCC and the components that are contained in the MCC. In the insulationresistance test, the megger produces a voltage and measures the leakage current, which iscalibrated directly in second megohms. The voltage is applied, for example, between the breakerphase and ground, or from phase to phase. The amount of leakage current that is detected resultsin a meter readout of insulation resistance (in megohms).

To conduct the insulation resistance megger test, the megger is connected between each MCCmain bus phase ground and the megger is operated. Insulation resistance megger tests must beconducted phase-to-phase and phase-to-ground on all panel buses, outgoing circuits, and PTs andCTs that are contained in the MCC. The line side and the load side of each circuit breaker that isinstalled in the MCC that is being commissioned must also be megger tested. Because the voltagepotentials that are generated during the megger test can damage any connected electronicequipment, megger tests must not be performed on electronic equipment. The insulationresistance values are recorded on a test data sheet or on Saudi Aramco Pre-Commissioning FormP-018, Motor Control Centers, in the recorded test data section.

During the commissioning process, the Electrical Engineer should evaluate the insulationresistance (megger) test values to ensure that the insulation resistance values that were recordedare greater than the manufacturer's minimum value. If the manufacturer's minimum value is notprovided, the value of the insulation resistance should be greater than the rated voltage +1 kV inmegohms. For example, a 600 V rated system must have a measured insulation resistance that isgreater than 1.6 megohms. Any value of insulation resistance that is less than the minimumspecifications should be investigated by the Electrical Engineer who performs the test dataevaluation.

The ratio of two time-resistance readings (such as a 60-second reading that is divided by a 30-second reading) is called a dielectric absorption ratio. The dielectric absorption ratio is useful inrecording information about the insulation. If the ratio is a ten-minute reading that is divided by aone-minute reading, the value is called the polarization index.




Because constant cranking is required for hand-cranked megger instruments, it is easier to run thetest for only 60 seconds and take the first reading at 30 seconds. When a power-operated meggerinstrument is used, the results of running the test for a full ten minutes and taking readings at oneand ten minutes will give the polarization index. An explanation of the evaluation of the dielectricabsorption ratio is provided in Work Aid 2.

Contact Resistance

The purpose of the MCC contact resistance test is to identify contacts that are defective ordetrimental to the operation of the circuit breakers, the contactors, or the starters or bus sectionsthat are contained in the MCC. The contact resistance test may also identify loose connections incircuit breakers, contactors, starters, or bus sections. Circuit breakers, contactors, or startersgenerally have removable cubicles or drawers to facilitate temporary removal for maintenance ortesting. Once the equipment is removed from the MCC and with the contacts of the equipment inthe closed position, the leads of a digital low-resistance ohmmeter are placed across the line andload sides of the contacts and measurements are taken. A digital low-resistance ohmmeter candeliver enough power to the contacts to make accurate readings that have more validity thanthose readings that can be obtained through the use of an ordinary multimeter. The contactresistance is recorded on a test data sheet or in the Saudi Aramco Pre-Commissioning Form, P-018, Motor Control Centers.

Increased contact resistance may be caused by contacts that do not make proper contact or bypitting on the surface of the contacts. The contact resistance values that are recorded should beconsistent with manufacturer's recommended values. Generally, values of contact resistance inexcess of 200 microohms and deviations of more than +/- 20% should be investigated. Technicaldata to evaluate the results of the contact resistance test can be found in the circuit breakermanufacturer's technical manual or in the Saudi Aramco Pre-Commissioning Form, P-000,Testing Guide Lines.

DC High-Pot

The purpose of the dc high potential (high-pot) test is to identify internal faults in or damage tothe MCC bus insulation system. The dc high-pot test should be done prior to the initialenergization of the MCC and after the megohmmeter test. The dc high-pot testing technique forMCCs involves the measurement of increased dc voltage that is applied to the system under test.The value of the leakage current is tracked as the test voltage is increased through several stepsand becomes a criterion of the condition of the MCC insulation.

Electrical test reference information for the dc high-pot test is provided in Saudi Aramco Pre-Commissioning Form, P-000, Testing Guide Lines. A portion of P-000 is provided in Work Aid2. The electrical test reference information provides the recommended dc high-pot test procedureand test voltages for the various connected equipment voltage ratings.




During the high-pot test, the leakage current is plotted against time at the end of each timinginterval. Figure 18 of Work Aid 2 illustrates representative current-time curves over a test period.The curves in Figure 18 show that good insulation exhibits a steady decrease in leakage currentwith time and that bad insulation exhibits a rise rather than a decline in leakage current. Thepolarization index can be calculated from this test data through division of the leakage currentafter one minute by the leakage current that is obtained after ten minutes.

The Electrical Engineer should evaluate the dc high-pot test leakage current test data to ensurethat the MCC high-pot test data meet the minimum requirements of a successful test. Apolarization index value of less than two or dc high-pot test data curves that indicate a steadyincrease in leakage current over the duration of the test should be investigated by the ElectricalEngineer who performs the test data evaluation.




SYSTEM PRE-OPERATIONAL CHECK-OUT

The system pre-operational checkout phase of the commissioning cycle for MCCs provides anopportunity for Saudi Aramco personnel to perform wiring checks, subsystem component checkouts, and MCC component interlock tests. Each MCC controller, contactor, or startercomponent is checked to ensure that it works individually and as a complete system.

Subsystems are checked to ensure that electrical continuity exists for control and protectivedevices. The proper operation of all subsystems is tested through use of controlled operation andcheck out of the controls and protective devices. Each subsystem is performance tested throughthe application of full operational voltage to each subsystem through the proper protectivedevices. A complete operational test is performed on equipment controls, interlocks, protectivedevices, and components with each subcircuit connected to its main system. During theperformance test, the main systems are still isolated and independent from plant systems. Beforethe equipment is connected to the plant system, subsystem performance testing is critical to ensurethe proper and safe operation of the equipment protection and control subsystems.

Operation tests are performed to ensure that the various MCC operational interlocks functionproperly. For example, if an MCC cubicle door has a circuit breaker trip interlock, the tripinterlock is tested. Circuit breaker trip tests are also conducted.




SYSTEM OPERATIONAL CHECK-OUT

The operational check-out phase of the commissioning cycle for MCCs provides an opportunityfor Saudi Aramco personnel to perform the following:

• Source feed compatibility checks

• Complete MCC functional test

Source feed compatibility checks are performed on MCCs through application of the full systemvoltage onto the MCC with all components (e.g., controllers) installed. With the voltage applied,voltage phasing, synchronizing, device rotation, protective relay calibration, and other source feedcompatibility checks are performed. Parallel or alternate power source feed operations are alsoperformed to ensure the total operation of the major components of the MCC.

A complete system functional test is performed on MCCs to ensure that the entire low-voltageelectric power distribution system functions in accordance with the system design. During thecomplete system functional test of MCCs, the electric distribution system is allowed to assume afully loaded condition for a period of time that is adequate to obtain the maximum systemtemperature. After the loaded time period, MCC temperatures are monitored. MCCtemperatures can be monitored locally through use of temperature monitoring equipment orthrough use of thermographic surveys. Temperature monitoring equipment can be temporarilyinstalled at MCC vents or in the MCC itself. Particular attention should be paid to wiring andterminal connections during the complete system functional test.




WORK AID 1: REFERENCES FOR EVALUATING MOTOR CONTROL CENTERSUPON RECEIPT

Work Aid 1A: MCC Applications Checklist

MCC rating information can be found on the equipment nameplate or in the manufacturer'stechnical manual. Use the following checklist and the appropriate sections of this Work Aid toverify that the type, the rating, and the operational characteristics of MCCs are correct for theapplication based on Saudi Aramco and industry standards.

• Verify that the MCC low or medium voltage nameplate ratings are correct for theapplication.

• Verify that the low voltage MCC switchgear meets the Saudi Aramco requirementsthat are shown in Figures 4 through 9.

• Verify that the low voltage MCC matches the information that is provided in thedata sheet (Figure 10).

• Verify that the medium voltage MCC switchgear meets the Saudi Aramcorequirements that are shown in Figures 11 through 16.

Work Aid 1B: Low Voltage MCC Ratings

This section of the Work Aid describes low voltage MCC ratings. For low voltage MCCs, theMCC bus capacity should be computed on the following basis:

• 125% of the normal full-load current of the largest motor that is supplied by theMCC, plus

• 100% of the full-load current of all other motors that can be operated at the sametime, plus

• 100% of all other loads (or a lower percentage if a diversity factor can be properlyapplied), plus

• 20% allowance for future requirements.

The final MCC bus capacity must be at least equal to the lesser of:

• The continuous current rating of the main incoming circuit breaker.

• The fan-cooled current rating of the power source transformer.




The low voltage MCC short-circuit rating should not be less than 105% of the maximumavailable rms symmetrical current available at the MCC line terminals.

The short-circuit interrupting rating must be a minimum of 22000 amperes of rms symmetricalcurrent. Short circuits are to be computed as the sum of the short-circuit current contributions ofthe motors connected to the motor control center and all other short-circuit current contributionsof the supply system at the point of connection to the motor control center.

Work Aid 1C: Low Voltage MCC Terminal Board Wiring

Because there are different terminal board arrangements in MCCs, NEMA ICS 2-322 provides forthe different types of terminal board wiring that is required in accordance with the arrangement ofthe terminal boards. The different types of terminal board wiring are designated Type A, Type B,and Type C. The features that are required by NEMA ICS 2-322 for Type A, Type B, and TypeC terminal board wiring are shown in Figure 4.

Type A (a) Terminal boards for load or control connections are prohibited.(Class IOnly)

(b) Connection diagrams are used only for each combination controller orcontrol assembly.

(c) Sketches of the overall dimensions of the control centers are required.Type B (a) A unit control terminal board must be provided. Unit load terminal blocks

must also be provided for combination controllers that are Size 3 or smaller.These terminal boards must be mounted on, or adjacent to, each unit.

(b) Sketches of the overall dimensions of the control centers are required.(c) (Class I Only). Connection diagrams are used only for each combination

controller or control assembly.(d) (Class II Only). The necessary interconnecting wiring between

combination controllers and control assemblies must be in the same MCCsection.

(e) (Class II Only). A connection diagram of the complete control assembly isrequired.

Type C (a) Master section terminal boards must be present that include load terminalsfor combination controllers that are Size 3 or smaller. All control terminalsfor all combination controllers or control assemblies in each vertical sectionmust be mounted on the stationary structure. Load terminal boards forfeeder tap units are prohibited.

Figure 4: Low Voltage MCC Terminal Board Wiring Type Features(From NEMA ICS 2-322)




Type C (b) Sketches of the overall dimensions of the control centers are required.(Cont'd) (c) (Class I Only). Wiring between sections or between master terminals is

prohibited.(d) (Class I Only). Interconnections between any combination controllers or

control assemblies are prohibited. All outgoing wires from any unit must becarried to the master terminal board, except wiring for combinationcontrollers that are Size 4 or larger.

(e) (Class I Only). Connection diagrams for each combination controller orcontrol assembly are required.

(f) (Class I Only). A sketch of main terminal boards showing general locationof terminals is required.

(g) (Class II Only). The necessary interconnecting wiring between combinationcontroller and control assemblies must be in the same section.

(h) (Class II Only). A connection diagram of the complete control center isrequired.

Figure 4: Low Voltage MCC Terminal Board Wiring Type Features(From NEMA ICS 2-322) (Cont'd)

Work Aid 1D: Minimum Low Voltage Indoor Motor Control Center TechnicalRequirements

The minimum technical requirements for low voltage indoor motor control centers (MCCs) aredefined in 16-SAMSS-503. Low voltage in Saudi Aramco installations is defined as 600 V andbelow. The requirements of 16-SAMSS-503 apply to full-voltage combination starters, feedercircuit breakers, contactors, dry-type transformers, panelboards, and auxiliary equipment that areassembled into MCCs and switchracks; however, only the MCC information will be presented inthis section of the Work Aid.




Figure 5 shows Saudi Aramco low voltage indoor MCC general requirements from 16-SAMSS-503.

GeneralRequirements

MCCs must be suitable for operation at nameplate rating within an ambientair temperature range of 0 oC to 40 oC.MCCs must conform to the requirements of NEMA ICS 2-322, except asotherwise indicated in 16-SAMSS-503.Designs and materials that are used in control assemblies must have at leasttwo years of verifiable proven field service. The Vendor must supply aUsers List indicating User company name, installation site, date ofinstallation, and equipment characteristics that are similar to the equipmentthat is quoted.

Figure 5: Saudi Aramco Low Voltage MCC General Requirements(From 16-SAMSS-503)




Figure 6 shows Saudi Aramco low voltage MCC construction requirements from 16-SAMSS-503.

GeneralConstructionRequirements

An external indication (e.g., "ON" or "OFF") must be provided to show thecircuit breaker or disconnect switch position.

Motor control assemblies must be "fully-rated" for bracing and interruptionof the available short circuit current that is indicated on the EngineeringDrawings and/or the Data Schedule.No operating device or instrument can be more than 1980 millimeters (78inches) above the floor.Motor data that is required for the selection of the controller and motorcontrol components must be as shown on the Engineering Drawings.All devices that are supplied under this specification that are to be used inhazardous (electrically classified) locations must be housed in enclosuresthat are approved for the purpose. Arcing devices must be housed incertified explosion proof enclosures. Sealing fittings must be furnished asrequired.Oil-immersed equipment (NEMA Type 8) is not acceptable.

MinimumMCCConstructionand Design

MCCs must be rigid, free-standing, metal-enclosed structures, that consistof vertical sections assembled into a group that have a common power busand that form an enclosure to which additional sections may readily beadded.

Requirements Each MCC vertical section must be subdivided into compartments thatcontain the various control and protective devices.MCC cubicle design must be NEMA Class I, Type B.All ventilation openings must be suitably filtered or screened with aspecified corrosion-resistant material (such as stainless steel hardware clothor galvanized screen) that is arranged to prevent the entrance of rodents andother foreign matter.

Figure 6: Saudi Aramco Low Voltage MCC Construction Requirements(From 16-SAMSS-503)




MinimumMCC

All control devices must be selected for proper operation in the designatedatmosphere without further protection.

Constructionand DesignRequirements(Cont'd)

Structure drilling, tapping, cutting, welding, and forming must be designedand factory finished to permit field rearrangement of the controllercompartments into any possible combination by the use of simple fastenerssuch as bolts and screws.If the bus plug-in contact design uses special shapes or fittings that areconnected permanently to the bus, the shapes or fittings must be provided atall locations that are needed by any rearrangement of all possible sizecompartments.Control device assemblies must have plug-in line connections or must bearranged so the assembly can be removed without deenergizing the MCC.Fuses must be accessible for replacement without removing the controldevice assembly from the MCC or disconnecting cables.Units that are designated as "FUTURE" on the Engineering Drawings mustbe complete with stationary elements, drawout pans, and door.A means must be provided to cover the openings which expose the verticalbus.Adequate space must be provided for incoming power, control, groundconductors, and conduit terminations. Minimum bending radius restrictionsmust be followed. Provisions for terminating all incoming conductors mustbe included.The line side of incomers must be provided with an ammeter and voltmeter,together with associated current and potential transformers.

Figure 6: Saudi Aramco Low Voltage MCC Construction Requirements(From 16-SAMSS-503) (Cont'd)




Figure 7 shows Saudi Aramco low voltage MCC enclosure and isolating panel requirements from16-SAMSS-503.

MCCEnclosureRequirements

Enclosures must be suitable for back-to-wall or back-to-back mounting.Back-to-back constructions that have a common horizontal bus are notacceptable.Enclosures must be designed for front access only and must be providedwith floor channels.Enclosures must have floor plates with holes and grommets as specified onthe Data Schedule. Holes must be provided with cover plates.Vertical sections must have a minimum width and depth of 508 mm (20 in),with each vertical section having a vertical wiring compartment with hingedcovers, means for support of wiring, and grommets where wiring penetratesmetal barriers.Space for horizontal wiring between vertical sections at the top and bottommust be provided. Wiring spaces must be isolated from the buses.Minimum individual space allocation in vertical sections of motor startersmust be sufficient to accommodate a NEMA Size 2 controller.All hardware must be galvanized cadmium or chromium-plated mild steel orstainless steel.

Isolatingpanels

Isolating panels must be provided between device, bus, and cablecompartments to permit the cables to be pulled safely into the MCC andextend to device compartments with the control center energized.Uninsulated live parts must not be located in cable pulling spaces.Isolating panels must be provided between device, bus, and cablecompartment to permit personnel to work safely. Safe work is performedwithin either an empty compartment or a compartment from which thecontrol assembly has been removed while the bus is energized.The isolating panels must prevent transmission of arcs and must retard themigration of arc products into bus spaces and/or cable pulling spaces.The isolating panels must prevent transmission of arcs and retard themigration of arc products between device compartments even when anintervening device assembly has been removed.

Figure 7: Saudi Aramco Low Voltage MCC Enclosureand Isolating Panel Requirements (From 16-SAMSS-503)




Figure 8 shows Saudi Aramco low voltage MCC bus and space heater requirements from 16-SAMSS-503.

BusRequirements

Main horizontal buses must consist of electrical grade copper bus bars thatare mounted on glass-reinforced polyester or non- hygroscopic ceramicinsulators.Buses must be rated for a minimum continuous current rating of 600 A,braced for a minimum of 42,000 A symmetrical short circuit current.All bus connections must be bolted with all bar connecting surfacessilver-plated or tin-plated.Power bus bars, bar connections and plug-in connection continuous currentratings must be based on a 40 oC ambient temperature and 50 oCtemperature rise.Bus phase arrangement must be 1- 2- 3, counting from front to back, top tobottom, or left to right, as viewed from the front of the control assembly.MCCs must have a silver plated or tin plated bolted copper bar ground busthat is horizontally mounted near the bottom of the structure and thatextends throughout the length of the MCC.Cable is not an acceptable substitute for bus material.Connectors that are sized for 70 square millimeters (No. 2/0 American WireGage (AWG)) copper grounding conductor must be provided on each endof the bus.The minimum momentary rating of all phase, neutral, and ground busesmust be 42,000 RMS symmetrical amperes.The continuous current rating of neutral buses, where specified, must be 50percent of the bus phase rating.

Figure 8: Saudi Aramco Low Voltage MCC Busand Space Heater Requirements (From 16-SAMSS-503)




BusRequirements(Cont'd)

Vertical power buses must be copper, must have a minimum continuouscurrent rating of 600 A, and must be enclosed in a flame-retardant,non-tracking, low-hygroscopic, glass-reinforced, polyester insulation andbus support system. The bus support system must provide phase-to-phaseand phase-to-ground bus isolation.Cable is not acceptable as a substitute for copper bar, including thetransition busing to other equipment.

Space Heaters Space heaters must be provided in each MCC vertical section.Space heater heating elements must have a voltage rating of approximatelytwice the supply voltage.Heaters and associated circuits must be rated for continuous duty.A space heater control system must be furnished for each piece of verticalequipment and must consist of a thermostat that is used to control theheater so that the equipment interior temperature is maintained severaldegrees above the ambient temperature.The space heater system must be completely wired and must include amanual disconnect.Space heater sheath temperature for all equipment must be limited to thetemperature that is specified on the Data Schedule.

Figure 8: Saudi Aramco Low Voltage MCC Bus andSpace Heater Requirements (From 16-SAMSS-503) (Cont'd)




Figure 9 shows Saudi Aramco low voltage MCC nameplates, wiring, and miscellaneousequipment requirements from 16-SAMSS-503.

Nameplates Engraved phenolic nameplates that show black letters on white face must beprovided and attached with stainless steel or brass screws to the door ofeach MCC unit.Warning nameplates must be provided on each compartment for whichopening of the branch circuit breaker does not de-energize all voltagesources within the unit. The warning plate must have white characters on ared background that read: "CAUTION - THIS UNIT CONTAINS ANEXTERNAL VOLTAGE SOURCE!".A nameplate must be attached to each controller and must indicatemanufacture's catalog designation, maximum horsepower rating at aspecified voltage, maximum continuous amperes, and control circuitvoltage.All nameplate wording must be in the English language according toAmerican usage except for danger and warning indicators which must bewritten in both Arabic (Naskh script) and English. White characters on ared background must be used.Separate nameplates, suitably located, must indicate the following:

1) Warning or operational instructions as required.2) Identity of all relays, meters, etc.3) Purchaser's assigned motor or equipment number and identification, when specified.

The bus structure, each motor control unit, and each feeder tap unit must beidentified with its short-circuit current rating expressed in RMS symmetricalamperes. This identification supersedes any interrupting rating shown onfuses or circuit breakers that are included in the units.

Figure 9: Saudi Aramco Low Voltage MCC Nameplates, Wiring,and Miscellaneous Equipment Requirements (From 16-SAMSS-503)




Wiring Control and secondary conductors must be stranded copper, 600 V, NECType SIS or THHN. The minimum conductor size must be 2.5 square mm(No. 14 AWG).Insulated, ring tongue, compression (crimped) terminals must be providedfor all control and secondary wiring terminations.All connection points between assembly control devices and field wiringmust be made with terminal blocks.Terminal blocks must be one-piece, phenolic, barrier-type, rated 20 A, 600V, minimum, with pre-numbered marking strips. A maximum of two wiresper point is permitted.Two-piece terminal blocks which allow complete withdrawal of unitassemblies are acceptable.Shorting terminal blocks must be provided for current transformer circuits.Each wire must be identified with a thermoplastic, slip-on type (ferrule),marker with permanently printed characters. Snap-on or adhesive typemarkers are prohibited.

MiscellaneousEquipment

Pushbutton and selector switches must be of the heavy-duty oil-tight typerated 10 A continuous at 600 V.Indicating lights must be of the incandescent heavy-duty oil-tight type withintegral transformer or series voltage-dropping resistor sized so that theapplied voltage is 80 percent of rated lamp voltage.Indicating lights must be designed so that relamping is performed from thefront of the MCC.All special tools required, such as nonstandard wrenches, sockets, etc., usedto latch/unlatch, bolt/unbolt, equipment supplied under this specification,must be provided with each MCC assembly.

Figure 9: Saudi Aramco Low Voltage MCC Nameplates, Wiring,and Miscellaneous Equipment Requirements (From 16-SAMSS-503) (Cont'd)

Figure 10 shows the data schedule that is used to order low voltage switchracks and MCCs fromthe manufacturer.




DATA SCHEDULEFOR 16-SAMSS-503, LOW-VOLTAGE SWITCHRACKS

(600 VOLTS AND BELOW)

INFORMATION SUPPLIED BY BUYER

1. Buyer's Quotation Request/Purchase Order No. ________________________

2. Buyer's B.I./J.O. No. _____________________________________________

3. Buyer's Line Item No. _____________________________________________

4. Area Classification: ( ) Classified ( ) UnclassifiedClass ______ Group(s) ______ Division ___

5. Enclosure Type: ( ) NEMA Type 4, 7 ( ) NEMA Type 4( ) Other ___________________ (Specify)

6. Main Horizontal Bus Continuous Rating ___________ A (RMS) at:( )50 deg C, (Covered)( )70 deg C, (Uncovered)

7. Incoming Section Entry: ( ) Top, ( ) BottomNo. of Access holes: ____________

8. Space Heater Supply; Voltage: __________________ V ACSource: ( ) Buyer ( ) Vendor CPTMaximum Surface Temperature of Heater Element deg C __________________

9. Canopy ( ) No ( ) Yes; Canopy Lighting ( ) Yes ( ) No

10. Enclosure Mounting and Arrangement: ( ) Single-Row( ) Double-Row ( ) Front ( ) Back ( ) Front and Back

11. Incoming Feeder: ( ) Bus Duct ( ) Cable in Conduit

12. Size of Incoming Feeder: __________________

13. Cable Conductors per Phase: _______________

14. Control Power Voltage: ____________________

Approved: _____________________ Dwg. No. NT- __________________

Date: _____________________ Revision No. __________________

Sheet 1 of 1

Figure 10: Data Schedule for Low Voltage Switchracksand MCCs (From 16-SAMSS-503)




Work Aid 1E: Medium Voltage MCC Ratings

Figure 11 shows medium voltage controller ratings.

1 Controllers that are rated for 630 amperes continuous are available from some manufacturers with interrupting ratings up to 500 MVA at 4000 volts.* Not extracted from NEMA standards.

Figure 11: Ratings for Class E2 (Fused) Medium Voltage Motor Controllers(From SADP-P-116 and NEMA ICS 2-324)

The required interrupting capacity must be 350 MVA at 4800 volts.




Work Aid 1F: Medium Voltage MCC Requirements

The minimum technical requirements for medium-voltage (5 kV class), metal-enclosed indoorMCCs are described in 16-SAMSS-506. The requirements of 16-SAMSS-506 apply to NationalElectrical Manufacturers Association (NEMA) Class E-2 current-limiting fused controllers and allcontrol and auxiliary equipment that is assembled into MCCs.

Figure 12 shows Saudi Aramco medium voltage indoor MCC general requirements from 16-SAMSS-506.

GeneralRequirements

Oil-immersed controllers are not acceptable for use in Saudi Aramcoinstallations.Motor control assemblies must be suitable for continuous operation atnameplate rating with cooling air surrounding the assembly enclosure withinthe limits of 0oC and 40oC.Designs and materials used in the control assemblies must have at least twoyears of verifiable proven field service. The Vendor must supply a UsersList indicating User company name, installation site, date of installation, andequipment characteristics similar to equipment quoted.

Figure 12: Saudi Aramco Medium Voltage MCC General Requirements(From 16-SAMSS-506)

Figure 13 shows general construction and design requirements for medium voltage MCCs.




GeneralConstructionRequirements

Controllers must be of the metal enclosed type consisting of a free-standing,full-height structure with a maximum of two controllers per vertical section.

Enclosures must be rigidly constructed to allow mounting pad levelvariations of +/- 1/8 inch. Under these conditions, doors must open andclose smoothly and all mechanical interlocks must function properly.Enclosures must be 2.28 m (90 in) nominal height.If Vendor's standard is three-high construction, the top unit must be for"FUTURE" or for auxiliary devices, as indicated on Engineering Drawings.Grounded metal barriers must be provided to isolate each vertical section,each compartment within a vertical section, high and low voltagecompartments, and main horizontal power bus compartment.A corrosion-resistant coating over a suitably prepared surface must beapplied to the inside and outside of the cubicle.Isolating shutters must be provided to automatically cover vertical bus whena drawout component is moved to the withdrawn position on "FUTURE"as well as active compartments.All parts must be readily accessible for maintenance and inspection.Power fuses and contactor must be mounted on a single drawout carriageassembly.

MinimumMCC

The cubicle design must be NEMA Type 1 for installation in anenvironmentally controlled location.

Constructionand DesignRequirements

All ventilation openings must be suitably filtered or screened with stainlesssteel hardware cloth arranged to prevent the entrance of rodents.

Figure 13: Saudi Aramco Medium Voltage MCC Constructionand Design (From 16-SAMSS-506)




MinimumMCC

All control devices must be selected for proper operation in the designatedatmosphere without further protection.

Constructionand Design

Enclosures must conform to NEMA ICS 6 "Enclosures for IndustrialControls and Systems" requirements for NEMA Type 1.

Requirements(Cont'd)

Enclosures must be of carbon steel sheet metal with supporting frame,designed for front access only, and suitable for back-to-wall orback-to-back mounting.Hinged and removable panels and doors must be provided with captivehardware.Self-tapping screws are not acceptable.All unpainted hardware must be galvanized, stainless steel, or cadmium orchromium plated.Compartment doors must be double or full-length hinged.

Figure 13: Saudi Aramco Medium Voltage MCC Constructionand Design Requirements (From 16-SAMSS-506) (Cont'd)

Figure 14 shows Saudi Aramco medium voltage MCC enclosure and isolating panel requirementsfrom 16-SAMSS-506.

MCCEnclosure

Enclosures must conform to NEMA ICS 6 "Enclosures for IndustrialControls and Systems" requirements for NEMA Type 1.

Requirements Enclosures must be of carbon steel sheet metal with supporting frame,designed for front access only, and suitable for back-to-wall orback-to-back mounting.Hinged and removable panels and doors must be provided with captivehardware.Self-tapping screws are not acceptable.All unpainted hardware must be galvanized, stainless steel, or cadmium orchromium plated.Compartment doors must be double or full-length hinged.

Figure 14: Saudi Aramco Medium Voltage MCC Enclosureand Isolating Panel Requirements (From 16-SAMSS-506)




Figure 15 shows Saudi Aramco medium voltage MCC bus and space heater requirements from16-SAMSS-506.

BusRequirements

The entire length of the power bus must be individually insulated for ratedvoltage.Full height single units must be equipped with power bus bars and a wiringtrough extending the full cubicle width.All power, ground, and wiring facilities must be arranged to facilitate futureadditions.All power and ground buses, including transition busing to other equipment,must be constructed of bar material.Cable is not acceptable for power or ground busing.Power and ground buses must be full size and continuous throughout.Tapered bus sizing is prohibited.Bolted power bus connections must be provided with a minimum of 2 bolts,nuts, and with either dished (conical) spring washers or flat washers andsplit lockwashers.Bus bar connection surfaces must be silver-plated or tin-plated.Power bus insulation materials for bars and bar connections must beflame-retardant, low-hygroscopic, and track-resistant throughout.Bolted bus joints must be covered with removable insulating boots. Tapingof bus and bolted joints is not acceptable.Bus phase arrangement must be 1, 2, 3, counting from front-to-back,top-to-bottom, or left-to-right, as viewed from the main switching deviceoperating mechanism side.

Space Heaters Each vertical section must contain a thermostatically controlled spaceheater.Heating elements must have a voltage rating of approximately twice thesupply voltage for extended service life.Heaters and associated circuits must be rated for continuous duty.Each heater circuit must be provided with an externally operablethermal-magnetic molded-case circuit breaker to serve as a disconnectingand overcurrent protection device.

Figure 15: Saudi Aramco Medium Voltage MCC Busand Space Heater Requirements (From 16-SAMSS-506)




Figure 16 shows Saudi Aramco Medium voltage MCC nameplates, wiring, and miscellaneousequipment requirements from 16-SAMSS-506.

Nameplates Nameplates must be attached to the controller group, individual doors, orcontactor as appropriate and must indicate the following:

1. Manufacturer's shop order number, date, and catalogdesignation.2. Horsepower rating of motor.3. Interrupting rating of the controller.4. Maximum continuous amperes.5. Nominal voltage rating.6. Control circuit voltage.

Separate nameplates suitably located must indicate:1. Warning of operational instructions as required.2. Identity of all relays, meters, and so forth.3. Purchaser's assigned motor number if specified.4. Foreign voltage when external sources are used.

Device nameplates must be provided for the identification of each controllerand auxiliary unit, indicating the circuit number and load served orequipment contained within an auxiliary cubicle.All panel mounted devices must be identified by escutcheon or nameplateon the front of the panel and by nameplate on the rear of the panel adjacentto the device terminals.Protective relay nameplates must be provided to indicate protectivefunction, ANSI device number, and phase(s) which is/are monitored.Device nameplates must be engraved laminated plastic with black 6.4 mm(0.25 in) characters on a white 64 mm (2.5 in) by 25 mm (1 in) backgroundas a minimum. Device nameplates must be in the English languageaccording to American usage.

Figure 16: Saudi Aramco Medium Voltage MCC Nameplates, Wiring,and Miscellaneous Equipment Requirements (From 16-SAMSS-506)




Nameplates(Cont'd)

Warning plates must be provided on each compartment door in which anexternal voltage source is terminated, reading: "CAUTION -THIS UNITCONTAINS AN EXTERNAL VOLTAGE SOURCE."Auxiliary cubicles containing drawout or tilt-out potential transformerssupplying undervoltage relays must be provided with a warning nameplatereading: "CAUTION - OPENING THIS COMPARTMENT TRIPSUNDERVOLTAGE RELAYS."Manual trip devices must be labelled: "Manual/Emergency Trip".Warning nameplates must be engraved laminated plastic withwhite characters on a red background. Warning nameplatesmust be written in both Arabic and English.Nameplates must be attached with stainless steel or brass screws except thatnameplates inside compartment may be attached with permanent adhesives.

Wiring Control and secondary conductors must be stranded copper 600 V NECType SIS or THHN.Minimum conductor size must be 2.5 sq mm (14 AWG).Each wire must be identified with a thermoplastic, slip-on wire marker withpermanently printed characters. Snap-on and adhesive type markers areprohibited.All connection points between assembly control devices and field wiringmust be made with terminal blocks conforming to the requirements of 16-SAMSS-506. All connections between compartment control wiring and removableassembly (truck) mounted devices must be by a single, self-aligning,multi-contact, stab assembly. (When a stab assembly cannot be used, apotted connector assembly must be used in the wiring harness.)

MiscellaneousEquipment

Each controller must have both externally and internally operable controldevices.

Figure 16: Saudi Aramco Medium Voltage MCC Nameplates, Wiring,and Miscellaneous Equipment Requirements (From 16-SAMSS-506) (Cont'd)




MiscellaneousEquipment(Cont'd)

Pushbutton and selector switches must be of the heavy-duty oil-tight typerated 10 A continuous at 600 V. Pushbutton control switches must beconstructed to prevent accidental actuation.Externally operable control devices must be of the hand-reset type for boththe overload relays and lockout relays.An externally operable alternating current control circuit power switch mustbe provided to be used as a control power disconnect and as a maintainedstop for both magnetically held and latched contactors.Internally operable control devices must include a readily accessiblestart/stop pushbutton to operate the main contactor for maintenance testing.This device must be operable when the controller is in the test position.An ammeter with a transfer switch and red and green "RUNNING" and"STOPPED" indicating lights must be mounted clearly visibly on theoutermost cubicle door. The red and green indicating lights must besupplied directly from "M" auxiliary contacts.Hand-reset lockout relay operating coil circuit must be monitored by awhite indicating light located adjacent to the relay handle.For motor feeders, an ammeter for motor space heaters must be mountedclearly visible on the outermost cubicle door.Indicating lights must be of the incandescent heavy-duty oil-tight type withintegral transformer or series voltage-dropping resistor sized so that theapplied voltage is 80 percent of rated lamp voltage.Indicating lights must be designed so that relamping is performed from thefront of the MCC.All special tools required, such as nonstandard wrenches, sockets, etc., usedto latch/unlatch, bolt/unbolt, equipment supplied under this specification,must be provided with each MCC assembly.

Figure 16: Saudi Aramco Medium Voltage MCC Nameplates, Wiring,and Miscellaneous Equipment Requirements (From 16-SAMSS-506) (Cont'd)




WORK AID 2: REFERENCES FOR EVALUATING MOTOR CONTROL CENTERINSTALLATION AND TESTING

Work Aid 2A: MCC Commissioning Electrical Test Values

1. Insulation resistance must not be less the fifty megohms.

a. Megger test voltages must be 1000 V dc in accordance with Saudi Aramco Pre-Commissioning form P-000, Testing Guide Lines.

b. The insulation resistance (megger) test values must be greater than themanufacturer's minimum value. If the manufacturer's minimum value is notprovided, the value of the insulation resistance should be greater than the ratedvoltage + 1 kV in megohms. For example, a 600 V rated system must have ameasured insulation resistance that is greater than 1.6 megohms.

c. Do not megger solid state devices.

2. Contact resistance must be determine in microohms or millivolts. Values of contactresistance in excess of 200 microohms and deviations of more than +/-20% must beinvestigated. Technical data to evaluate the results of the contact resistance test can befound in the circuit breaker manufacturer's technical manual or in the Saudi Aramco Pre-Commissioning form, P-000, Testing Guide Lines.

3. A dc high-potential test is one in which the increase of applied voltage is controlled.Measured currents are continuously observed for abnormalities with the intention ofstopping the test before breakdown occurs. The voltage that is used for the dc high-pottest should be in accordance with the manufacturer's technical manual for the MCC. If amanufacturer's technical manual is not available, then the Saudi Aramco Pre-Commissioning Form, P-000, Testing Guide Lines, must be used. In accordance with P-000, the high-pot test voltage is 9 kV for equipment that is rated 2.5 kV. The dc high-pottest is conducted in two stages as follows:

a. A polarization index (PI) test is performed by applying an initial voltage step ofabout one-third of the recommended maximum voltage. The initial voltage stepmust be maintained at a constant level for 10 minutes. The PI is calculated bydividing the one minute leakage current by the 10 minute leakage current. A PIvalue of 2.0 or less must be investigated.

b. After the initial 10 minute test, the dc test voltage is increased in approximately 10uniform steps. Each step should have a one minute duration. The voltage isincreased until the maximum recommended dc value is reached.




4. Minimum pickup current, trip times, and instantaneous pickup values of protectiveequipment (e.g., relays) must be adjusted to engineer settings. Test values should fallwithin manufacturer's published time-current characteristic tolerance band.

Work Aid 2B: Information, Formulas, and Tables for Use in Evaluating the Results ofInsulation Resistance (Megger) Tests

The results of all commissioning megger tests that are performed must be documented on theappropriate Saudi Aramco pre-commissioning form.

The following are the types of megger tests that can be conducted:

• Short time or spot reading

• Time resistance

• Dielectric absorption ratio

When the dielectric absorption ratio megger test is performed, the polarization index can bedetermined through use of the following equation:Figure 17 provides insulation conditions for 60/30 second ratio results and for 10/1 minute ratioresults.

Figure 17: Dielectric Absorption Ratio Chart




Work Aid 2C: Information, Formulas, and Tables for Use in Evaluating the Results ofDC Hi-Pot Tests

The dc hi-pot test should be secured if one of the following situation occurs:

• The duration of the test has expired.

• A rapid rise in leakage current occurs.

• The polarization index < 1.

The following are the characteristics of a satisfactory dc hi-pot test:

• The leakage current gets smaller over time.

• The polarization index > 1.

• The leakage current increases on a straight line as voltage is increased. No "knee"is noticeable in the leakage current curve.

An example of dc hi-pot test data is shown in Figure 18. Figure 18 also shows both good and badinsulation test data.

Figure 18: Example of DC Hi-Pot Test (Good and Bad Insulation)




Work Aid 2D: Saudi Aramco Pre-Commissioning Form

Figures 19 shows the Saudi Aramco Pre-Commissioning Form, P-018, Motor Control Centers,which provides a field installation checklist for MCC installations. The pre-commissioning formhas a broad checklist of visual and mechanical inspections, as well as the listed electrical and teststhat are required for MCC installations. Space is also provided on the form for test data.




Figure 19: Saudi Aramco Pre-Commissioning Form, P-018, Motor Control Centers




Figure 19: Saudi Aramco Pre-Commissioning Form, P-018,Motor Control Centers (Cont'd)




Work Aid 2E: Excerpts from GI 2.710

The following is an excerpt from GI 2.710, New Construction Check List Example, thatillustrates the overall checklist and sign-off for major pieces of electrical equipment.

3. Electrical Equipment

All substations, powercable, electrical equipment,including lighting andwiring, to be checked forproper application,operation, and grounds.Distribution panels,switches properly identified,and all energizationcertificate requests signed.

Construction Agency

Power Distribution Dept.

Project Inspection

Commissioning (Note 1)

Figure 20 shows an excerpt from GI 2.710, General Instruction Manual, that illustrates theinspections and tests that should be performed on major pieces of electrical equipment prior to theturnover of a facility.




Figure 20: GI 2.710 Excerpt




Figure 20: GI 2.710 Excerpt (Cont'd)




GLOSSARY

dielectric absorption The ratio of two timed insulation resistance readings (such as aratio 60-second reading that is divided by a 30-second reading).

polarization index The ratio is a ten-minute insulation resistance reading that is dividedby a one-minute insulation resistance reading.

Commissioning Motor Control Centers

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Transcript of Commissioning Motor Control Centers