The purpose of this method statement for electrical testing and commissioning is to explain step by step method to implement the correct practices for the precommissioning, testing & commissioning of “LV Switchgear “through the guidelines.
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Electrical testing and commissioning method
The below procedure will ensure that the job execution complies with the project requirements and serves the intended function to satisfactory level.
Required Instruments & Tools
- Portable Hand tools
- Step Ladder
- Measuring instruments
- HV Test Kit
- Secondary injection kit
- Insulation resistance tester
Pre-commissioning Procedure for LV Switchgear
Ensure that the LV Switchgear installation is complete & all mechanical & electrical comments on installation ITRs are completed & approved.
Ensure that no damage has occurred between mechanical completion & precommissioning.
- Repair / replace damaged components, if any.
- Check for the location of installation is free of any water or construction debris.
- Ensure that the Switchgear are properly tagged & identified location wise and service wise as specified.
- Ensure that the wiring termination to the LV Switchgear are complete & are tight & secure.
- Ensure that the outgoing cables (power & control) from the Switchgear are terminated in the respective panels & properly tagged & identified.
- Ensure that the earthing of the LV Switchgear has been completed.
- Ensure that all BMS wiring are completed.
- Ensure that the cables to the Switchgear are properly tagged & identified.
- Ensure that the rating of the breakers (ACB, MCCB,MCB & ELCB) are as per approved shop drawings & schedules.
- Ensure that overload relays are selected & set as per the actual connected load.
- Ensure that the interlocking is done as specified.
- Ensure the metering connections are proper.
- Check manually the breakers of all the cubicles in the LV switchgear.
- Check for proper sliding of the cubicles in the rails for all draw out modules.
- Check the termination of the cables to the bus bars are tightened to the required torque using torque wrench.
Insulation Resistance Test
- Isolate all incoming & outgoing cables.
- Apply a voltage of 500 volts DC between phase ‘R’ to Earth for 1 minute with phase Y,B & N shorted & earthed & record the values.
- Repeat the test for other phases as well.
Power Frequency Voltage Test
- Connect the HV lead from step up transformer to R- phase.
- Short the Y & B phase and connect to earth. Also connect the enclosure to earth.
- Switch ON the HV test kit control unit & apply the recommended test voltage (by increasing gradually) for 1 minute to R-phase with respect to other phases earthed & grounded.
- Record the leak current.
- After 1 minute gradually reduce the test voltage to zero & then switch-off the HV test kit. Discharge the pole & also the HV test kit.
- Repeat the test for Y-phase & B-phase & tabulate the results.
Secondary Injection Test
- Check the tightness of secondary connections to all the metering circuits.
- Inject the nominal secondary values step by step using secondary injection kit to the power scheme & tabulate the output values as per the rating of meters.
Method statement for electrical testing and commissioning for LV Switchgear
- Ensure that all the precommissioning checks are carried out successfully.
- The incoming supply of the LV switch gear shall be measured for current, voltage, frequency & phase sequence.
- The outgoing feeders shall be energized one by one & the supply shall be measured for current, voltage, phase & frequency.
- Check the metering functions for proper operation & correct readings.
- Check the earth leakage trip setting.
- Check tripping operation of ELCB
- Check the incomer trip setting.
- Check the circuit breakers on/off function.
- Check overload relay setting
- Check timer setting
- Check the interlocking is as specified.
- Pre-commissioning check sheet for LV Switchgear
- Commissioning check sheet for LV Switchgear
- Risk Assessment