Research on transient characteristics of TRV under double faults of hybrid reactive power compensation line

• A double fault equivalent model of the UHV HRPC line is established, and the mechanism of TRV generation under double fault is revealed. The simulation results show that when double faults occur at different positions of the transmission line, the structural parameters of the transmission line change. Compared with the single-phase grounding fault, the TRV peak and RRRV under the double fault increase significantly. When the double fault occurs on the back side of HRPC, the TRV peak reaches 2924 kV, which affects the normal breaking of the circuit breaker. • When double faults occur at different times on both sides of the HRPC, the TRV peak and RRRV increase with the increase of the time interval between the secondary fault and the primary fault, because the secondary fault time affects the superposition of the series compensation voltage in the HRPC. A first fault occurred in 1.0 s and a secondary fault occurred in 1.047 s. The TRV peak reached 2662 kV, which threatened the insulation performance of the circuit breaker. • The HSGS suppression measures are proposed. The simulation results show that the reasonable configuration of HSGS can effectively reduce the value of the TRV peak, reduce the excessive working condition of RRRV and the breaking current of circuit breaker. The national standard of circuit breaker is satisfied, and the stable operation of transmission system is guaranteed. With the continuous increase in voltage levels and transmission capacity of modern power systems, traditional hybrid reactive power compensation (HRPC) can no longer fully meet the stability requirements of ultra-high-voltage (UHV) transmission. During short-circuit faults, controllable HRPC introduces high-amplitude, low-frequency oscillations in the fault current, intensifying the transient recovery voltage (TRV) and posing a serious threat to system insulation. To address this issue, this study establishes an equivalent double-fault model of the UHV HRPC line based on its compensation principle, derives the TRV mechanism under different fault locations and initiation times, and analyzes the effects of compensation degree on TRV peak and rate of rise. The deterioration characteristics of TRV under double faults are revealed, and a high-speed grounding switch (HSGS) suppression scheme is proposed. Simulation results show that double faults on HRPC lines can cause TRV to exceed standard limits, hindering reliable circuit breaker interruption, while a properly configured HSGS effectively reduces both TRV peak and RRRV, enhancing breaker reliability and overall system stability.