Hunting refers to the periodic variation in speed, voltage or power factor of the machine. Let us say a synchronous generator is rated for 1500 rpm. When hunting occurs, the speed will vary below and above the set speed, 1500 rpm. For instance, it may vary from 1300 to 1800.
In voltage hunting, the voltage varies periodically.
Hunting may be severe or mild.
Hunting causes a variation in output. It also results in instability across the network. The hunting in one machine can cause hunting in another machine.
In Synchronous machines, there can be active power hunting as well as reactive power hunting.
Active power hunting occurs when the active power (kW) varies.
- The common causes of active power hunting are
- Speed Control Issues with the Prime mover
- Issues with fuel input to the prime mover
- External Power Fluctuation in the Grid
Reactive Power Hunting
Reactive Power Hunting occurs when there is a periodic variation in the reactive power (kVAr) and the Power Factor
The common causes of Reactive Power Hunting are
- Loose connection in the excitation circuit of the alternator
- Faulty AVR (Automatic Voltage Regulator)
- External reactive power fluctuation in the grid
Active Power Hunting can be rectified by adjusting the speed controls and the fuel system of the prime mover.
Reactive Power Hunting is directly related to the generator. Check the excitation circuit inside the generator. Check the AVR wiring and change the settings if required.
No load Hunting and On-Load Hunting
No Load hunting refers to the variation of the speed and the voltage when the machine is running on no-load. That is, when the generator circuit breaker is open.
On Load hunting is when the hunting occurs when the circuit breaker is closed and the machine is on load.