Isolators in a power system are those switches whose open and close positions are clearly visible. Each isolator must be operated in off load condition. Although there is another type of isolator called on load isolator. We can operate these isolators provided there must be a parallel path during operation of the isolators.
The isolators have main two parts. These are insulating part and conducing part. So, we must take proper care for both of the parts.
The following actions we need to take in the coerce of the maintenance of electrical isolators.
- Half yearly, we need to clean the support insulator body with removing of salt cements and acid fumes, if accumulated.
- Also, half yearly we need to inspect the contact surface. If we found any abnormality (burning of contacts) we must immediately replace the same with new one. If the sign of burning is very small, we can remove those by rubbing with sand paper.
- Also we must check the proper alignment of the contact rods etc during maintenance.
- Also we must check the lightness of bolts of mechanism as well as power connections and earth connections.
- By fully closing the isolators we need to check whether all the male contacts properly enter in the female contacts or not. If any abnormality found the proper adjustment is needed to be alone immediately.
- Then we physically have check whether the mechanical interlock is working properly or not. That means we have to try closing the earth switch after closing the isolator. If it is not possible physically, then we can ensure that the mechanical interlocking is all right. Otherwise we need check the mechanism and rectify it.
- Half yearly we need to lubricate the shaft bearing assembly including mechanical linkages of auxiliary switches.
- We apply a thin layer of conductive lubricant on the contacts the auxiliary switches.
- We need to check the tightness off all the electrical control connections in the mechanism box. Also we need to check the functionality of all auxiliary relays, in the mechanism box.
- We should measure the contact existence of each contact of each phase once in 2 years. We may use a Digital Micro Ohm meter for the purpose.
- Lastly we must check the electrical inter locking scheme of each isolators and CBS come under the interlocking scheme of that isolator.
Maintenance of Earth Switches
- We must check the alignment of the earthling blades, clean the blades including the female contacts of the isolators.
- We need to check the aluminium and copper flexible bonds of the earth switch. If we found any defect, we should replace those without going far repairing. Because we should not compromise for connection of earthing.
- We also need to check for the proper lightness of the earthing connection of the isolator structure and mechanism box.
- In marshaling kiosk of isolator, we need to visually check the contacts, clean the control terminals.
- The space heater plays a significant role in marshaling kiosk. Because it keeps the inner space of the kiosk moisture free. So proper checking the healthiness of the space heater in the marshaling kiosk is essential.
- If any defect found in the door gasket of the kiosk, it must be repaired or replace to avoid the entry of rain water in the kiosk.
- Maintenance of a Potential Transformer and Capacitive Voltage Transformer
- Maintenance of Minimum Oil Circuit Breakers
- Maintenance of SF6 Circuit Breaker
- Maintenance of Electrical Isolators and Earth Switches
- Maintenance of Current Transformer
- Maintenance of Lightning Arrestors (Lighting Arresters)