Fire at a generator of a power plant

The vent occurred at a power generation plant. One of its turbines was stopped for minor repairs and adjustment. The generator’s excitation breaker and air-operated disconnect breakers were opened. When the turbine generator had nearly completed its shut down, one of the disconnect breakers closed spuriously and reconnected the generator to the grid again. The turbine generator accelerated to rated speed within 25 - 30 seconds. As a result, the generator rotor got into unbalance and its bearings were destroyed.
Cooling hydrogen, sealing oil and lubricating oil caught fire. All feed water and emergency feed water pumps were lost. An alternative make-up water supply and reduction of primary circuit pressure prevented serious consequences.

INITIATING CAUSES
The failure of the turbine was caused by its unplanned, accidental restart, due to the malfunctioning of a circuit breaker.

ROOT CAUSE(S)
Although the source does not report the root causes, from the extension of the fire and its consequence for the overall plant it can be plausibly assumed the same root causes as in the event HIAD ID = 042. The fire could spread up and cause such damage due to lack of measures against fire propagation and escalation.

excitation breaker,
turbine-generator unit
turbine hall

DESCRIPTION OF THE FACILITY
The reactor technology was a graphite moderated pressure tube type reactor, boiling light water reactor. It fed steam directly into the turbines, without an heat-exchanger and a secondary cooling system.

It is unknown if radioactivity was released in the environment

none (Unit shutdown automatically).

, see HIAD ID = 042.

It is unknown if were adopted. For a general