Overheating of Busbar Isolating Switches: Causes and Handling Procedures
Overheating of busbar isolating switches is a common electrical equipment defect. If not addressed promptly, the situation can severely deteriorate during a system short circuit—when high short-circuit current flows through the overheated point, potentially causing contact melting or even destruction of the switch.
When overheating of a busbar isolating switch is detected, follow these steps for safe handling:
Report the defect to the grid dispatcher and request load reduction to lower the current through the affected circuit.
If a bypass busbar is available, use the bypass circuit breaker to take over the load, allowing the overheated busbar isolating switch to be taken out of service.
If conditions permit, energize a standby line, open the circuit breaker of the faulty line, and then open the overheated busbar isolating switch for maintenance.
If neither bypass operation nor de-energization is possible, apply the following measures based on the busbar configuration:
For single-busbar configurations:
Minimize the load current in the affected circuit as much as possible. Improve cooling conditions (e.g., by installing temporary forced ventilation fans), enhance real-time monitoring, and coordinate with the dispatcher to create conditions for an early outage and repair.
For double-busbar configurations:
Reconfigure the system operation mode—close the spare busbar isolating switch and open the faulty (overheated) one to isolate it from service. Ensure that bus differential protection and non-selective switching logic remain correctly configured and functional during the transition.
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