The purpose of this safe work electrical method of statement is to define the step by step procedure to implement the correct practices for the precommissioning & commissioning of Motor Control Center.
By following the guidelines contained herein installation contractor shall ensure that the testing and commissioning job execution complies with the project requirements and serves the intended function to satisfactory level.
Below is list of necessary tools to be arranged before the MCC testing and commissioning.
- Portable Hand tools
- Step Ladder
- HV Test Kit
- Secondary injection kit
- Insulation resistance tester
- Multimeter
Pre Commissioning Procedure for Motor Control Center
Ensure that the Motor Control Center installation is complete and all electrical & mechanical comments on installation inspection reports are closed and approved by consultant/client.
Also make sure that no damage has occurred during the period between mechanical completion and testing & precommissioning.
Repair / replace damaged components, if any.
Check and make sure that area of installation i.e. MCC electrical room is free of any kind of debris dust or humidity etc.
Also check and 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, tight, secure and approved.
Make sure that the outgoing cables (power & control) from the MCC are terminated in the respective equipment / panels & properly tagged, identified and approved.
Ensure that the earthing installation of the Motor Control Center has been completed.
Check and ensure all BMS wiring has been completed.
Ensure that the cables from BMS to the MCC are properly tagged & identified.
Make sure 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.
Check that emergency stop switches are provided as per project specifications and applicable local regulations.
Ensure the metering connections are proper and as per electricity supplier guidelines.
Check manually the function of all breakers of all the cubicles in the MCC room.
Also check and verify the electrical & mechanical interlock between star & delta starters.
Check the operation of sliding of the cubicles in the rails for all draw out modules.
Make sure termination of the cables to the bus bars are completed and 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 and also the HV test kit.
Repeat the test for Y-phase and B-phase, tabulate the results on approved test sheets.
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 and record 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 and approved by consultant.
Incoming supply of the Motor Control Center shall be measured for current, voltage, frequency & phase sequence.
Now outgoing feeders shall be energized one by one and the supply shall be measured for voltage.
Check the metering functions for proper operation and 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.
Also check trip operation of ELCB (where applicable)
Check the incomer trip settings.
Now check the circuit breakers on/off function.
Check overload relay settings.
Also check timer settings.
Attachment:
- Pre-commissioning check sheet for Motor Control Center
- Commissioning check sheet for Motor Control Center
- Risk Assessment
- Manufacturer’s instructions for MCC Testing and Commissioning