Optimizationofair gap clearance in 750 kV converter station area on AC side of ±800 kV UHVDC project

When AC side of converter transformer was connected to 750 kV system, air clearance of AC side would be one of controlling factors in design of valve hall. In order to determine minimum inter-phase clearance A2 on 750 kV AC side in Lingzhou converter station, monographic studies were performed on selection method and optimal value of A2, consideringactual conditions of the station. Based on theoretical analysis and previous testing curves, A2 could be 7.0 m and 6.5 m respectively for two-bundled conductors and bus tubes. Full size tests were carried out for conductor configuration of two bundled conductors and bus tube and 50% switching impulse discharge voltage curve was obtained. According tofull size testresults, A2 could be 6.5m. Based on overvoltage level on 750 kV AC side and optimization of MOA performance, A2 could be further optimized from 6.5 m to 5.9 m or 5.8 m or even lower. These results are important for reducing valve hall size, lowering project design difficulty and saving building cost. ©, 2015, Power System Technology Press. All right reserved.