Research on Protection Method for Pumped Storage Unit Loss-of-Excitation Faults Based on Electrical Quantity Variation Characteristics

Loss-of-excitation faults are a common fault form of pumped storage units that can threaten both unit safety and grid stability. However, the traditional loss-of-excitation protection based on the impedance principle may exhibit delayed operation or even fail to operate in the case of partial loss of excitation or loss of excitation under light-load conditions, and there is a risk of maloperation in the case of system oscillation. Therefore, this paper analyzes the differences in the characteristics of electrical quantities such as voltage, current, active power, reactive power and power angle during the loss of excitation and system oscillation of a pumped storage unit, and proposes a loss-of-excitation index criterion based on the magnitudes and polarities of variations in terminal voltage, reactive power, and power angle, which constitutes a new method of pumped storage unit loss of excitation fault protection. The simulation results show that compared with the traditional impedance principle loss-of-excitation protection, the proposed method reduces the operating time by 58.6–90.0%. It can reliably and quickly detect the loss-of-excitation fault of pumped storage units under various operating conditions, and shows good anti-maloperation ability for non-loss-of-excitation faults and system oscillation. In addition, the proposed protection method can still maintain reliable operation under the condition of noise interference with a signal-to-noise ratio of 20 dB or communication delay of 0.2 s, which verifies its strong engineering practicability and anti-interference ability.