Is sudden change of DWATT to negative value can cause a trip of the F5 Gas Turbine generator? because in our case in just a split second DWATT becomes negative value from 19MW to -12. and then a trip of flame out happens (fuel was cut) in just 0.131 sec after the negative power was received. This is what our trip log reported.

 

emelito,

From your description the turbine experienced a 31 MW change in load--that kind of load swing "... in just a split second ..." is usually the result of either a loss of fuel (pressure and/or flow), OR a very large load swing and/or grid frequency change. If the fuel supply was suddenly cut off (low gas fuel pressure; loss of liquid fuel supply pressure/flow) then the load would decrease extremely suddenly--and the resulting Process Alarm would be "Loss of Flame Trip", because there wouldn't be enough fuel to maintain flame. At this point, the Speedtronic would shut the fuel stop valve to prevent a sudden increase in fuel flow from causing an explosion in the combustors.

In the case of sudden grid load/frequency changes, the turbine would be severely loaded if the load suddenly went from 19 to -12 MW which would be very difficult for the turbine to maintain flame while load was being lost that quickly so in order to protect the turbine it would be tripped on reverse power.

In either case, the result should be the same: turbine trip. There is usually a reverse power relay external to the Speedtronic turbine control panel which monitors both the magnitude of reverse power AND the time it takes to go reverse and if the time is very quick (split second) then it's going to trip the turbine by shutting off the fuel.

Trip logs are not always the fastest at measuring and recording instantaneous changes--but you can be assured that a sudden 31 MW change in load is NOT good for the turbine and auxiliaries and the turbine should be tripped to prevent large load oscillations from occurring if the load oscillations were allowed to continue which could damage the load coupling, the combustors, the axial compressor and just mess things up pretty badly.

 

If that amount of time spent in the negative is acceptable for you, add a noise (averaging) filter which adequately covers the times you "dip".

(Sorry if my answer doesn't make sense, I don't have any direct experience with Gas Generators.)

 

GT should not trip on loss of DWATT signal. Suppose GT is running at 25 MW and DWATT suddenly becomes negative due to loss of power of transducer in that case GT will hold good the last valve of 25 MW and continue to run at that level.

After restoration of power to transducer,you give the master reset command to increase or decrease the GT load and load shall very as per requirement. Reverse power protection to trip the GT can be avoided however you ensure your generator reverse power protection is in line. During power swing also generator could trip on reverse power so time delay must be provided to prevent unnecessary generator tripping.

 

On GE gas turbines with constant settable droop feature, there are triple redundant DWATT transmitters and there may be a protective trip on loss of 2 of 3 transmitters.

I don't remember for certain, but in general, if there are triple redundant sensors, there will be protective action on loss of 2 of 3 signals.