2 Ignitors are there and one of them not functioning. Primary & Secondary Resistance of this transformer is same as working one. What could be wrong? All cables, ignitors checked and everything else fine. Have anyone seen problem like this?

 

you mean ignition transformer trouble for gas turbine ?

 

a) No power to ignition circuit
- fused L1 supply open circuit,
- flame safety controller detects safe start fault, purge cycle incomplete or interlock
safety string has an open, any of which will disable ignition (transformer) relay output
- manual start switch open

b) high voltage wire insulation defective
High voltage insulators are faulty - cracked, dirty, soot covered, creating ground path.

c) primary or secondary winding shorted to case ground.

d) transformer is OK but
- the spark electrodes are defective (too far apart, shorted)
- high voltage wiring is defective, open or shorted to ground.

e) transformer fails under load, windings short internally as it heats up.

 

Sometimes, the cable ends are not very well made. There is supposed to be a small "pin" that almost looks like a nail that goes through the insulator and makes contact with the cable's conductor. Sometimes that contact is very poor, and sometimes the "pin"/nail falls out or gets lost when the cables are unplugged for maintenance outages.

Which begs the question: When did this problem start?

Are you sure there is power to the input side of both transformers? And that the neutral connection to both transformers is good?

Have you tried taking the cable from the working ignitor and plugging it into the ignitor which is not working, and vice versa, and then energizing the two transformers and observing the two ignitors?

If that test causes the ignitor which was not working to work and the ignitor which was working not to work, the problem is the cable which is connected to the non-working ignitor.

If the same ignitor which wasn't working before exchanging cables is still not working after exchanging cables and the exciter which was working before exchanging cables is still working after exchanging cables, the problem is either the transformer or the ignitor.

You could then also exchange the cables at the transformer; it might not be easy, but it could be done temporarily as part of the test.

As David says, sometimes a transformer will fail under load.

 

Have you tried swapping cables at the transformers and then at the ignitors?

Greg Ponto
Lead Combustion Turbine Specialist
Elwood Energy

 

Maybe the problem is with the cables. Why not try to change them or switch them.