On one of our GE F9E DLN1 machine the load spikes to about 15MW and back to zero during synchronization/generator breaker closure and the GT trips. The trip was due to the bleed valve opening and closing when the load spike occurred. As a temporary remedy, we are forcing the bleed valve solenoid prior to synchronizing and unforcing it after the generator breaker is closed. Please advice possible root causes of this problem. GT Control is GE Speedtronic Mark V TMR with <I> interface.

 

Have you used VIEW2 to monitor the permissives to L20CB1X to see what could be changing, or if something is wrong with the solenoid output itself?

 

> Have you used VIEW2 to monitor the permissives to L20CB1X to see what could be changing, or if something is wrong with the solenoid output itself? <

Thanks for replying CSA. Yes, we did use VIEW2 and monitor L20CB1X. The solenoid valve 20CB is waiting for DWATT to be more than 10MW then the solenoid 20CB energizes to close the 4 bleed valves.

 

As seems to be my failing these days, I neglected to ask when this problem started. Was it after a maintenance outage? After the Mark V was powered-down for some reason and then powered back up? Was some sequencing or Control Constant modification recently made and downloaded to the panel and then the processors/panel re-booted? Was some work done ("calibration") on the load (MW) transducers or the PT and/or CT circuits feeding the load transducers?

By the way, what is the grid frequency doing during and after synchronization? Is it stable or is it unstable? Is it more unstable than normal recently?

You say you are forcing the bleed valves during synchronization. What is happening to the load during synchronization when the bleed valves are forced? Is it still "jumping"?

The amount of "load" is a function of the amount of fuel. So, if the load is spiking and causing the bleed valves to close suddenly and then the load is dropping very quickly and causing the breaker to open on reverse power and that's causing the bleed valves to open, the problem isn't the bleed valve opening/closing, the root cause is the fuel increasing rapidly and then decreasing rapidly.

But, I'm still not very clear about the issue. As is typical of DLN-I software the bleed valves close when the load goes above 10 MW, and you seem to be saying that as soon as the generator breaker closes the load "jumps" to 15 MW (or at least above 10 MW), and the bleed valves close. And then the load reduces very quickly and the generator breaker opens and the bleed valves open.

I believe once the bleed valves are commanded to close they remain closed until the generator breaker opens (I don't have any DLN-I software to look at presently to confirm that). In other words, there is a "latch" around the MW signal that keeps the bleed valves closed until the generator breaker opens. If that is true, then something is causing the generator breaker to open, and that is opening the bleed valves.

What is causing the generator breaker to open? Is it the reverse power relay or the reverse power function of the Mark V?

If you're forcing the bleed valve signal and the load isn't spiking, then there's something else going on that we don't yet know about or understand with regards to the synchronization or loading. When the generator breaker is automatically synchronized and neither Pre-Select Load nor Base Load is selected prior to the synchronization the Speedtronic should load the unit to Spinning Reserve, which is usually defined by the Control Constant LK90SPIN, and it should do so relatively smoothly and without spiking. So, what has changed to cause the unit to load so quickly or to unload quickly?

Could the problem be that there is some issue with the MW transducers or the PTs or CTs providing signals to the MW transducers? Is the fuel (and load) actually increasing and decreasing rapidly, or is it just that the load signal(s) are increasing and decreasing rapidly?

Use VIEW2 during synchronization to monitor all of the load (MW) transducer signals and FSR and the gas control valve LVDT feedback. Monitor L70R & L70L also, as well as all the signals that can cause them to be a logic "1".

You need to determine if there is truly a load spike and sudden drop during synchronization or if it's just a signal problem, or, if there is truly a load spike and sudden reduction then you need to determine what is causing the fuel to suddenly increase and decrease.

Lastly, please provide a list of the alarms, in chronological order with the time stamps that occurred when this event happened. ALL of the alarms, please. Including any and all Diagnostic Alarms. Also, is the Speedtronic experiencing any 125 VDC supply problems or battery grounds? Does the Mark V have a <DACA> and if so, is it powered by an AC source and what is the AC source (such as an inverter or UPS output)?

There are a lot of questions above. Please make a list of all of them and respond to all of the questions; without a full response to all of the questions above it will be very difficult to provide any further assistance.