6FA gas turbine connected to 132kv grid on grid fault machine went normal stop.

we did not found any relevant alarm in the mark vie if any body face the problem kindly explain the reasons.

 

Kindly explain the grid fault and the magnitude of any frequency excursions--high or low.

What alarms did you find that you believe were not relevant? Kindly list all alarms that preceded the STOP and any after the stop as well.

Did any generator- or transformer protective relays operate?

Did the generator breaker open before the unit went into a STOP or did the STOP command start unloading the unit and then the generator breaker opened?

You should be able to answer all of these questions from the Trip Log, which should be stored on the HMI for at least thirty days.

Have you examined the auto stop logic to see if there are any signals related to generator- or transformer protective relays which might initiate an auto shutdown sequence?

While it is a GE "standard" to alarm on all automatically-initiated shutdown (STOP) commands, sometimes the "standard" gets overlooked. This is especially true if there were last-minute modifications to application code made during commissioning.

The logic signal L94AX is the usual signal name for automatic shutdown logic to set to a logic "1" to then set L94X, the shutdown logic to a logic "1". You should examine the L94AX rung as well as the L94X rung to see if you can determine what might have initiated the shutdown.

If the grid frequency resulted in an opening of the generator breaker without tripping the turbine and the fuel was reduced so much that the turbine speed went below L41HS dropout (TNK14HS2), then it's very possible that the L94X rung latched in and the unit went into a normal fired shutdown.

Kindly advice with the answers to the above questions and perhaps we can help.

If you discover the cause by investigating the L94AX and L94X rungs and from examining the Trip Log files, please post the findings here to let others know.

 

You say you had no relevant alarms but you say it was a normal stop, how do you know?

You say you had a grid fault, what was it?

You really need to post much more information, it is nearly impossible to try and diagnose anything from what you have given us.