During a load rejection governor

[odlanor]

During a load rejection governor automatically switch its operation mode to "Isolated Network" with a speed control mode, and start closing the Distributor.
The dynamic response of regulators speed is slower than the rate of increase of speed of generators s (Approximately 8% / s).
2 things happen:
1- Partial shutdown(86PS) by overspeed relay.
2- Total shutdown (86E)by Automatic Voltage Regulator for failure Excitation Second Stage

How to resolve this problem?

 

[catserveng]

Could you provide some additional details, like what kind of prime mover, how big, governor type, etc? Hard to make any suggestions based on what you provided so far.

Mike L.

 

[rasevskii]

Evidently this is one of your 80MW tube turbines, subject of a recent thread regarding the 32R reverse power relay. On load rejection (100%) the temporary speed rise has to be considered. On tube turbines that I was once involved with, that was about 60%. THe overspeed protection has to be set so high to cover this without tripping, with a suitable time delay. A second stage overspeed protection set higher with short time lag should be considered in case of a runaway situation.

The excitation system should absolutely not trip on load rejection. Since these are likely static exciters, there shoud be almost NO change in stator voltage on a full load trip. The settings must be non-optimal, perhaps all-wrong...

rasevskii

 

[odlanor]

It is a hydro powerplant.
governor and AVR are ABB.

 

[odlanor]

2- Total shutdown (86E)by Automatic Voltage Regulator for failure Excitation Second Stage

During a load rejection, there is a violation of the absorption capacity of reactive power by the Estreito Hydro powerplant and consequent loss of control of the voltage set value.
The loss of both AVR channels causes a fault trip 86E.