Mission Brief

The Device That Must Interrupt

The protection can be perfect, but if the breaker opens slowly or unevenly the fault still burns and the plant still fails. A new 145 kV SF6 breaker on Bay 5 has to be proven before the bay is energized: how fast each pole parts, how closely the three poles agree, how healthy the contacts and coils are, and whether it will still trip on a sagging battery.

• Measure per-pole opening and closing time
• Check pole discrepancy (the poles must part together)
• Measure main contact resistance with a micro-ohmmeter (DLRO)
• Verify the trip/close coil minimum operating voltage
• Confirm insulation across the open gap and issue the record