Metal-Clad SwitchgearMetal-Clad Switchgear Installation & Precommissioning InspectionInstallation & Precommissioning Inspection

April 15, 2007Abdullah M Al-Dushaishi

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OUTLINEOUTLINE

EQUIPMENT INSTALLATION INSPECTION BUSBAR INSTALLATION INSPECTION CABLE CONNECTION INSPECTION GROUNDING CONNECTION INSPECTION SOME DESIGN CONCERNS PRE-COMMISSIONING REFERENCES

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EQUIPMENT INSTALLATION EQUIPMENT INSTALLATION INSPECTIONINSPECTION

Ensure that adequate protection is provided when installing switchgear

Switchgear shall only be installed in an indoor, air-conditioned environment

Switchgear shall have an unobstructed horizontal space of:a) Not less than 2 meters in front

b) Not less than 1 meter in back and sides

Spacing requirement between equipment shall be based upon the largest dimension for either

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EQUIPMENT INSTALLATION EQUIPMENT INSTALLATION INSPECTIONINSPECTION

Lifting/handling devices shall be provided within a room containing switchgear to mechanically assist in removing to floor level, any withdrawable component (e.g., circuit breaker, contactor, potential transformer, etc.) weighing over 20 kg

Switchgear shall be free of any physical damage after installation

Switchgear should be properly anchored to its foundation

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EQUIPMENT INSTALLATION EQUIPMENT INSTALLATION INSPECTIONINSPECTION

Switches, circuit breakers, and other operating mechanisms shall be manually exercised to make sure that they are properly aligned and operate freely

Grounding connections shall be made properly

Debris, scrap wires and surplus shall be removed from the switchgear interior before closing the enclosure

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EQUIPMENT INSTALLATION EQUIPMENT INSTALLATION INSPECTIONINSPECTION

Covers, doors & enclosure parts shall be properly tightened

The switchgear shall be vertically & horizontally aligned before anchoring

Check components for proper identification as per IFC drawings and specifications

Nameplate on equipment shall conform to single line diagrams and schematics

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EQUIPMENT INSTALLATION EQUIPMENT INSTALLATION INSPECTIONINSPECTION

Concrete floor in front of switchgear shall be flush with the roller level of lower breaker carriage rack and have a smooth surface to facilitate removal and rolling of breaker

The bay spacing of transformers and the location of the incoming circuit breakers on switchgear lineups shall be positioned to minimize metal enclosed bus or cable bus length and/or eliminate bends

Preferably, incomer circuit breakers shall be located at ends of switchgear lineup

Unavoidable bends in cable bus or metal enclosed bus shall be inside the substation building

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BUSBAR INSTALLATIONBUSBAR INSTALLATIONINSPECTIONINSPECTION

Neutral buses shall not be used within switchgear

Cable shall not be used to extend the main bus of switchgear

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BUSBAR INSTALLATIONBUSBAR INSTALLATIONINSPECTIONINSPECTION

Contact surfaces for the main bus connections shall be clean

Tightness of bolted bus joints are correct as per manufacturer's instruction for the proper torque (foot-pound) levels

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CABLE CONNECTION CABLE CONNECTION INSPECTIONINSPECTION

Cable phasing shall be in accordance with connection diagram

Proper cable tags shall be provided

Cables termination shall be in accordance with cable manufacturer's instruction

Cable connections are clean and securely bolted.

Bolt torque values shall be as per manufacturer's specifications

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GROUNDING CONNECTION GROUNDING CONNECTION INSPECTIONINSPECTION

Sections of ground bus previously disconnected at shipping sections shall be reconnected when units are installed

Secondary wirings are connected to switchgear ground bus as indicated on IFC drawings

Ground bus shall be connected direct to grounding grid and shall not run in metal conduit unless conduit is adequately bonded to the circuit

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SOME DESIGN CONCERNSSOME DESIGN CONCERNS

Switchgear shall not be used to control: low voltage motors and high voltage motors rated less than 5kV

In industrial facilities, 480V switchgear shall not be fed from 4160V systems

A separate 120 VAC branch circuit shall be provided for the space heater

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PRE-COMMISSIONINGPRE-COMMISSIONINGCheck electrical relays, meters, or instruments to determine connections are made properly and devices function properly

Check settings of the adjustable current and voltage trip mechanisms to confirm that they are at proper values.

Check control, power transformer and PT fuses for size, type, and circuit location

Check PT and CT ratios

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PRE-COMMISSIONINGPRE-COMMISSIONINGCheck wiring connections for tightness at instrument transformers and terminal blocks

Protective devices’ setting for current, voltage, or other relays shall be done on-site in accordance with manufacturer’s recommendation

Ground-fault protection system shall be tested in accordance with manufacturer's instruction

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PRE-COMMISSIONINGPRE-COMMISSIONING

Protective relays, overcurrent trip devices, and breakers shall be tested for correct connections and operation at factory

Factory test results shall be referenced during Precommissioning

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PRE-COMMISSIONINGPRE-COMMISSIONINGInsulation resistance test shall be performed to make sure switchgear is free from short circuits and grounds. This test shall be done both phase to ground and phase to phase and with the switches and breakers both opened and closed

Switchgear busbar shall be tested for insulation resistance with a 1-minute test (phase to phase and phase to ground) with 1kV megohmmeter

Instrument transformers shall be tested for insulation resistance with a 1-minute test with 1 kV megohmmeter

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PRE-COMMISSIONINGPRE-COMMISSIONING

Each circuit breaker protective relay device shall be calibrated and tested with final settings in accordance with relay setting summary or coordination study

With CT disconnected, CT secondary circuit shall be tested for continuity and operation of applicable relays and meters by applying current to the CT secondary winding

PT secondary circuit shall be tested by applying voltage to the PT secondary, with PT disconnected, verifying operation of all applicable relays and meters

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PRE-COMMISSIONINGPRE-COMMISSIONING

Space heaters, switching and indicating devices shall be tested for operation

Auxiliary devices interlocks shall be tested for operation

Local and remote control devices/circuits shall be tested according to engineering specification

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REFERENCESREFERENCES

NFPA 70 --National Electrical Code, 2005

NETA ATS -- Acceptance Testing Specification for Electrical Power Distribution Equipment and Systems, 1999

SAES-P-116 -- Switchgear and Control Equipment, 28 February 2005

SAES-P-119 -- Onshore Substations, 30 march 2005