Maintenance checks on MCC cells
a. Ensure that the load is tripped from control room and switch is in off position.
Switch off the isolator at MCC cell.
b. Open the door and rack out the cell into isolation position.
c. Check the tightness of terminal of contactor, 3C, control transformer, control
fuses, wipe in contacts, power cables, etc.
d. Check the tightness of component mounted.
e. Look for any charred components or terminals.
f. Check the IR value of 3C, contactor, control transformer, isolator etc.
g. Check the isolator double switch feature.
h. Check the OLR and calibrate the OLR.
i. Check the pick and drop out value of contactor, 3C.
j. Check the fuses for healthiness and fuse carriers for proper contacts.
k. Clean the arc-chutes of the contactor and clean all the components of the MCC
cell properly.
l. Check the resistances of control transformer, contactor, 3C etc.
m. Check the tightness of control cable at main TB compartment.
Maintenance on MCC panel.
a. Ensure the permit and all isolations.
b. Open the bus bar chamber and discharge the bus bar.
c. Disconnect the cables connected to bus bar and take the IR value of bus bar and
cable individually. Connect it properly and tight it to proper torque.
d. Check the tightness of nut and bolts and cables connected to buses.
e. Open the main TB compartment and check the tightness of all cables and clean it.
f. See the tightness of power terminal compartment and clean it.
g. Check that cables are supported properly.
h. Do checks on CT, PT used for indication purposes.
i. Clean the entire MCC panel properly and take the IR value.
j. Carry the checks on relays, which are used in the MCC panel.
k. See for proper earthing connection and tightness of the earthing connections.
l. See for proper house keeping.