May 2018

Generator Circuit Breaker (Explosion)


The more interesting findings during our assessments are related to poor commissioning practices. These items tend to be more complex than construction defects and typically more serious from a safety, equipment protection, and reliability perspective of the asset.

One case involved an "explosion" of a generator circuit breaker.  The event took place about one year after COD, destroyed the GCB and damaged an F-class turbine generator (both stator and rotor).

The Event: During a unit start the operator was at the elevated GCB panel.  The generator field breaker was closed, so the generator exciter was energized.  The operator inadvertently pushed the earthing switch button which activated.  The earthing switches are NOT designed to be activated when the generator/exciter is energized.  The switch exploded (vaporized) with the GCB housing being damaged and opened like a tin can.  The operator was shielded from bolts and other shrapnel, but luckily did not fall from the platform.

Background: The GCB vendor provided a set of dry contacts on each earthing... Read more

Contractor Savings

Possibly only a time savings, but doubtful.

Repair Costs

Unit was out of service for 6 months.  New breaker, rewound stator and rotor, recommissioing of unit...  All-in costs between contractor, owner, an insurance company was about $8mm.