fault in a generator of a ship

[mottt]

We got 4 diesel units (1000 kw)in a ship, and in the moment of the fault we got one of the generator coupled to the main bars, in island mode.... the voltage of the generator start to swing, at this moment the crew of the ship see it and couple the other generator... after conect the incoming generator, the other generator is disconected for overcurrent trip, the trip is at 1,3 full load current.
When I see the generator i find the next: AVR with the rectifier diodes in short circuit, Permanent Magnet generator totally burned, and a diode positive of the rotor is shortcircuit.
The load in the fault moment was 300 kw.

 

[davidbeach]

Is there a question in there somewhere?

 

[RRaghunath]

Could it be that the generator was feeding negative phase sequence currents (unbalance loads, harmonics etc.) resulting in rotor burning and Excitaion system damage!!
May be, you can share with the forum the findings once the generator is open for inspection.
Thanks.

 

[mottt]

yes, the rotor was ok, and the stator was ok, the only damage is AVR, PMG and positive diode on the main rotor... the question is why i had so much damage, if i get a broken AVR, the system must stop, creating a shutdown, but this time... the system couple other generator in the moment that the first get without excitation, how do you see this point? is it posible?'

 

[waross]

The shorted diode in the rotor may have caused the damage to the AVR. The shorted diodes in the AVR may have caused the damage to the PMG. Do you have any equipment that may have generated a high voltage transient? Is it possible that the crew put a second generator on-line before the fault because of increasing load? The damage may have been started by a poor synchronization attempt and the story changed a little bit afterward.
respectfully

 

[itsmoked]

I would agree with waross. Perhaps a very bad synchronization actually led to the problem?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com