The purpose of this safe work method of statement procedure is to define the step by step method to implement the correct practices for the precommissioning & commissioning of Motor Control Center through the guidelines contained herein so as to ensure that the job execution complies with the project requirements and serves the intended function to satisfactory level.
- Portable Hand tools
- Step Ladder
- HV Test Kit
- Secondary injection kit
- Insulation resistance tester
Pre-commissioning Procedure for Motor Control Center
- Ensure that the Motor Control Center installation is complete and all electrical & mechanical 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 MCC are properly tagged & identified location wise and service wise as specified.
- Ensure that the wiring termination to the Motor Control Center are complete & are tight & secure.
- Ensure that the outgoing cables (power & control) from the MCC are terminated in the respective equipment / panels & properly tagged and identified.
- Ensure that the earthing of the Motor Control Center has been completed.
- Ensure all BMS wiring has been completed.
- Ensure that the cables to the MCC are properly tagged & identified.
- Ensure that the rating of the breakers (ACB, MCCB,MCB,ELCB, relays, contactors,timers,etc.,) are as per approved shop drawings & schedules.
- Ensure that overload relays are selected & set as per the actual connected load.
- Ensure that emergency stop switches are provided.
- Ensure the metering connections are proper.
- Check manually the breakers of all the cubicles in the MCC.
- Check the electrical & mechanical interlock between star & delta starters.
- 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 out put values as per the rating of meters.
Commissioning Procedure for Motor Control Center
- Ensure that all the precommissioning checks are carried out successfully.
- The incoming supply of the Motor Control Center shall be measured for current, voltage, frequency & phase sequence.
- The outgoing feeders shall be energized one by one & the supply shall be measured for voltage.
- Check the metering functions for proper operation & correct readings.
- Check the functionality of starters in manual mode.
- By keeping the selector switch in AUTO mode check the functionality of the starters by simulation.
- Check the earth leakage trip setting.
- Check trip operation of ELCB (where applicable)
- Check the incomer trip setting
- Check the circuit breakers on/off function.
- Check overload relay setting
- Check timer setting
- Pre-commissioning check sheet for Motor Control Center
- Commissioning check sheet for Motor Control Center
- Risk Assessment
- Manufacturer’s instructions