Figure 5.1 Speed droop graph for the example
1,440
1,450
1,460
1,470
1,480
1,490
1,500
0 100 200 300 400 500 600 700 800 900 1000
Droop = (1500 - 1442) / (975 - 0) × 1000 / 1500 × 100 = 4.0 %
5.4.5 Adjusting speed droop
As far as possible, the speed droop must be the same for all the gensets (including the emergency genset), since this gives
the system natural stability when running under switchboard control, or if the controller loses power. When you have
measured the droop of each genset (as described previously), you can adjust each governor accordingly.
Adjusting the droop for a mechanical governor
Adjust the droop at the governor. Refer to the governor supplier for information on how to do this.
Adjusting the droop for an electronic governor
Program the droop that is needed in the electronic governor. Refer to the governor supplier for information on how to do this.
5.4.6 Measuring voltage droop
DEIF recommends that the voltage droop for each genset in the system is 4 %. The voltage droop for the shaft generator
must also be 4 %.
A lower voltage droop gives a faster dynamic control loop. However, if the dynamic control loop is too fast, the system is
unstable. A higher voltage droop gives a slower (maybe too slow) dynamic control loop.
Measuring the voltage droop
To measure the voltage droop for a generator:
1. Make sure that you can connect a reactive load or loads to the generator that are up to 100 % of the generator nominal
reactive power (Q, in kvar).
• At the very minimum, you need to be able to load the genset up to 40 % of the generator nominal reactive power.
PPU 300 Commissioning guidelines 4189341106 UK
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