Plant Involved: Pole Mounted Air Break Switch Disconnector – LEL type – 33kV
Flashover at isolation gap on LEL type interrupter head.
SOP – these type are not to be used as a point of isolation.
Plant Involved: Circuit Breaker – FKI Eclipse – 11kV
During the site inspection on site at Maidstone Grid South discharge was detected from 11kV switchgear. The switchgear was de-energized and inspected. The L3 phase VT disconnector contacts were covered in carbon. When cleaned the contacts were functional although there were some small marks caused by low current sparking across the joint.
The poor contact continuity was caused by the combination of 2 factors:
1) The unsupported weight of cables caused cable connection plate displacement on L3 phase.
2) When VT disconnector handle is operated slowly but in full extents, contact blades don’t travel quite as far as when operated normally, although this is not an issue without problem of 1) above.
Remedial action – Ensure that the cable weight is supported by cleats in switchgear panel and cable support fixings underneath the panel as it is instructed in the Eclipse IOM