Stator winding Fault
Stator winding Fault
(OP)
A couple of days back one of our generator tripped on generator differential protection and smoke started coming from it.The CO2 did not operat on auto so it was manually released.Also the transformer diiferential protection operated resulting in spray on trf.
Inspection revealed 60 to 70 bars effected.The lower sid of bars out of slots was effected.Six or seven had completed melted while other seemed to have suffered from heat.It was a class B insulation.
I want to ask whether the slots in direction of rotation will suffer from heat or the one behind.The rotation is clock wise.I hope I make my self clear.Also why did trf.differential protection operated
Inspection revealed 60 to 70 bars effected.The lower sid of bars out of slots was effected.Six or seven had completed melted while other seemed to have suffered from heat.It was a class B insulation.
I want to ask whether the slots in direction of rotation will suffer from heat or the one behind.The rotation is clock wise.I hope I make my self clear.Also why did trf.differential protection operated






RE: Stator winding Fault
I have no comment on the slot damage.
Rafiq Bulsara
http://www.srengineersct.com
RE: Stator winding Fault
As Rafiq saied, firstly: CT saturation.
You have send us more information.
SLD
Size of generator and Xfr
CT size
Type of protective relay
Setting of 87T, etc
Best Regards.
Slava
RE: Stator winding Fault
RE: Stator winding Fault
Muthu
www.edison.co.in
RE: Stator winding Fault
Also the transformer differential also covers the generator but since the gen.differential operated why did the trf.differential operated.
Winding was installed in 1977
RE: Stator winding Fault
RE: Stator winding Fault
Isn't Xfr differential-it's block generator-transformer differential.
Operated in the same time as generator differential. Is OK.
RE: Stator winding Fault
jan63:
The melting of some six or seven of stator bars has been caused by arcing. This was the primary cause of destruction. The secondary part of winding destruction has been caused by the heating energy from the place of arcing. This energy has been "transported" from the place of origin to the other stator bars "downstream" of the arcing area because of rotor rotation. Modern insulation is regarded as not burning by itself. Manufacturers even claim self-extinguishing properties. However, as long as arcing is present considerable energy is feeding the environment. In your case CO2 application was delayed, this further deteriorating the situation.
Was there a delay in de-excitation also (protection failure)?
Regards
Wolf
WWW.HYDROPOWER-CONSULT.COM
RE: Stator winding Fault
RE: Stator winding Fault
Here's a thought to mull about: Which direction would an arc (a conductive plasma) be driven in the magnetic field between the stator and rotor?
RE: Stator winding Fault
Did you determine the nature of the failure? It sounds like a failure in the end winding region which spread to the adjacent bars causing your cascading failure.
Multiple failures of the winding from the same machine is typical end of life behaviour. Does your company perform routine HV testing (hvdc ramp/negative charge PI)?
I assume you have a stator bar versus a stator coil. Each winding system has different failure modes.