At 220kV Substation, 220kV Bus fault occurred at early morning humid weather condition. All line connected to Bus are tripped In Bus bar protection trip.
Task
To identify the reason of fault, Search Operation/inspection of each element in the switch yard started.
Some traces of burnt materials and pieces of broken porcelain found at a place under the bus- section isolator.
It was observed that flashover has occurred at one of the feeder bay B-phase post-insulator of bus-section isolator (from observing the traces).
Due to Bus section Isolator flashover, All line connected to that Bus are trip in Bus protection trip.
Action Taken
The IR value of the concerned post insulator was carried out and found to be not in the prescribed limit.
So, a new Post-Insulator was replaced with to restore the system immediately whose IR value was in the prescribed region.
Due to deterioration of the IR value of the existing post-insulator, there might have been a flashover. Or, A foreign object like conductor strand might have fallen from a height if taken away by some birds for which the flashover might have occurred.
Due to Humid weather, Bus isolator Insulator flashover occurred due to their loaw IR value.The CCTV camera was checked and found with the flashover.
Required recommendations for minimize Bus fault
The IR value of the Post-Insulator should also be carried out at a regular interval. Polymer insulators can be used in place of porcelain ones.
The switchyard should be maintained neat & clean i.e. residues of the conductor strands, aluminum twigs etc. should not be left at switchyard after completion of the required maintenance work.
The bird nests should also be removed if found to have a check in such incident.
During Night period, Check any abnormal sparking or chattering occurred in any equipment. Also check any Hot spot of all feeder line equipment.