Droop

Shaleshwar,

Threre is no harm in asking questions of academic interest, but bear in mind that a thorough research on your own would be more rewarding. I don't understand, why 'Off the shelf' answer is a much sought after 'commodity' which is ultimately detrimental to professional development. Incidentally, we do have highly experienced and talented professionals on this forum who would gladly answer such questions, yet I think it is a good ideal to seek their advise on 'real life problems'.

However, following is a partial answer to your question.

Voltage variations are not uncommon in the utility system. When they are minor, the reactive droop compensation within the voltage regulator will assure reactive load sharing between the generator and the interconnected bus. This prevents large changes in reactive current for any one generator. Excessive reactive current can result in either overload or loss of generator synchronism. Reactive droop compensation is accomplished by the addition of a current transformer in one of the generator output leads. With the proper orientation of this signal into the voltage regulator sensing circuit, the control system becomes sensitive to reactive current flow. The compensation circuit has the same effect as adding approximately 10% impedance in series with the generator whose automatic voltage regulator provides 1/2% voltage regulation.

Generators intended for parallel operation are fitted with a quadrature droop C.T. which provides a power factor dependent signal for the AVR. The C.T. is connected to the AVR. The DROOP adjustment is normally preset in the works to give 5% voltage droop at full load zero power factors.