Impact of Geoinduced Currents on Excitation Mode of Synchronous Generator at Power Plant

Abstract

The authors developed an equivalent circuit for the synchronous generator and a transformer unit. It could help determine the magnetizing current parameters for a generator transformer when the magnetic system is saturated due to geoinduced currents provided the synchronous generator has an automated excitation controller. The authors identified the dependencies of the magnetizing current fundamental harmonic on the magnetizing power of the generator transformer and the geoinduced current value. The article provided numerical values for the fundamental harmonic of the magnetizing current and power at various geoinduced current values for a TDTs 400000/242/20 generator transformer. It is demonstrated that the increase in the reactive power of the synchronous generator results from the operation of the automated excitation controller aimed at maintaining the constant voltage in the generator buses by the excitation current increase. The authors identified the safe value ranges for the excitation order to compensate the increase in the magnetizing power of the generator transformer without any current overloads on the rotor and stator or any reduction in the synchronous generator active load.