Hi everyone,
I am a translator who currently working with SPEEDTRONIC Mark VIe Turbine Control Systems Guide and one of the places where i stuck is the "**wind-up***". Could anyone help me to understand what it means?

Thanks in advance.
Best regards,
Serg

It goes like this:
Gas Fuel Protection sequencing provides monitoring and diagnostics perform leakage diagnostics across the Stop/Speed Ratio valve and Control Valves by performing a number of tests during startup and warm-up, to prevent the gas turbine from excessive or low fuel at light-off, to prevent "**wind-up***" of the machine.

If the expected P2 pressure drops below the required setpoint for fuel splits when the generator breaker is closed, the unit will perform a runback (L3FG_P2X) to prevent "**wind-up***" of the fuel gas system to prevent an overspeed condition in the event full pressure is restored.

 

Serg,
I don't know how well I can explain this, but here goes. First try searching the web for controller "wind up", I got several good responses back from my query. Wind up typically refers to a controller trying to meet setpoint that has saturated due to the process variable being too far away from the process setpoint.

The gas turbine controls try to maintain a certain P2 interstage fuel pressure. The setpoint for this pressure is based on the machine type and on the speed of the machine. For instance on a Frame 7 machine the typical required inlet fuel pressure is 350 psi. The P2 interstage pressure setpoint is very low during firing and roll-up (less than 20 psi if I recall), but increments up as turbine speed ramps to 100% speed (somewhere around 310psi). Alarms and trips are set-up if P2 pressure is too high, too low, or if the SRV valve is open more than a certain percentage during start-up.

The problem would be that if the SRV was opening a very large amount to get the required P2 interstage pressure (controller wind-up), say if incoming gas pressure was very low. And if incoming fuel pressure suddenly rose up, that the controls and the SRV valve itself may not be able to react quickly enough to control P2 pressure, and if it rises too much above setpoint the machine could overpeed or overtemp causing damage.

So basically since P2 pressure is so important, logic is setup that will trip or runback the machine if P2 pressure deviates from setpoint too much, or if the stop ratio valve is opening further than should be necessary to maintain P2 pressure with normal incoming gas pressure, rather than letting the controls "wind-up" trying to maintain P2 pressure at setpoint.

I hope this helps some, I will guess that another author may explain this better than I have, but I tried!

 

Thank you very much for your help)))

 

Hello over there,

The wind up (P2 check) you are describing is not used in older control system philosophy of the GE HD GT's. This new control philosophy (wind up) is probably standardized in latest control systems (MKVI/MKVIe).

This dedicated P2 check sequence is verifying whether prior start up FG leakage is evident downstream SRV. Bear in mind that SRV is normally plunger type of valve and the GCV globe type valve. Both valves are expected to pass gas since they are not designed as TSO valves (tight shut off). In the past there were incidents such as contained explosions in the exhaust system due to passing SRV/GCV valves. Passing of these valves will lead to accumulating of gas in the exhaust section, which its presence will introduce explosion during ignition.

These incidents were introduced by humans rather then the SRV valve failure and or design of the control system. In order to manage and reduce the risk (make it almost monkey proof), new sequence was designed and ready to be used for the MKVI/MKVIe.
The above described philosophy is used for two shaft GT's MKV/MKV control.

Docendo Discumus