Fire in a generator of a power plant

Leak from faulty hydrogen seal ignited by short circuit between inboard slip ring and outboard slip ring radial lead connection. Hydrogen flame caused damage to brush gear assembly and inboard slip ring.

The INITIATING CAUSE was a leak of hydrogen via a faulty seal on the turbine rotor.

The ROOT CAUSE is unknown.

Slip ring, hydrogen seal

The damage was confined to the hydrogen sealing systems.

A chronological overview of the incident:
13:00 - The hydrogen station opened for business, filling six FCVs with hydrogen by 3:30 PM.
15:30 - Filling of the seventh FCV began.
15:34 PM - An unusual hissing sound of gas leakage was heard (when the filling hose pressure was 79 MPa). A bang was heard upon completion of filling. The gas detector did not activate at this time.
15:39 PM - To check for leaks, the dispenser was manually operated to release residual pressure into the filling hose. The gas detector at the end of the dispenser's filling hose then triggered a high-level alarm, causing the station to shut down.
18:30 PM - A dispenser manufacturer visited the factory and confirmed that the outer layer of the short-length filling hose had torn approximately 4 cm from the crimped portion of the emergency breakaway coupler end fitting.