Alternator stator winding failure 4

[SA07]

Hi
Our alternator 950 kW 400 Vac stator has failed. The protection relay Micom tripped by Restricted Earth Fault.
Up to now we can see the damaged part of the stator winding as attached picture.
There was no disturbance on the utility network or internal fault on any motor. We have restarted the plant with the boiler operating now.

There are 4 cables per phase coming from the stator winding which is connected to the output L1,L2,L3
One of these cables on each phase is short with the earth. The environment is full of dust particles. The dust particles are residue of coal ash after it is burned in the boiler. There were dust inside the stator. The alternator is air cooled with no water refrigerant on top.

What might be possible cause of the stator winding failure?

 

[edison123]

If all the 4 louvers have filters, you are just recirculating outlet hot air inside the enclosure, which might explain high winding temps. A properly designed clean inlet air ducting and an outlet air ducting will reduce the winding temps.

Muthu

http://www.edison.co.in