We found the unit was tripped from Temp Wheelspace 1st Stage HH. After that we replace both of T/C on 1st Stage Wheelspace. But still face the problem.
one of T/C still high during running. How can I check that Wheelspace Temp is really high, not from T/C error.
There is no other way to verify wheelspace temperatures on GE-design heavy duty gas turbines.
When did the problem occur--after a maintenance outage?
What were the wheelspace temperatures in the weeks prior to the trip? Were they High? Were they increasing? How fast were they increasing? If the were already high, near the High-High setpoint then it's likely there is a real problem. If they were not high, or were not increasing over time (days; weeks) then it would seem that something is really amiss if they both increased quickly at approximately the same time.
If both wheelspace temperature T/Cs indicated High-High temperature prior to the trip, then it's likely there is a problem. If you replaced both T/Cs and now only one indicates a high wheelspace temperature then the problem is likely the insertion depths of the two T/Cs is not the same, or there was a problem with the insertion.
Please write to let us know what you find.