同塔双回架空线-电缆混合输电方式合闸过电压差异化研究

Differentiation Study on Closing Overvoltage of Headline-cable Comprehensive Transmission with Double Circuit Transmission Lines on Same Tower

为了研究同塔双回架空线-电缆混合输电方式下的合闸过电压暂态特性,选取某220 k V电网,利用EMTP电磁暂态程序建立了同塔双回架空线-电缆混合输电方式暂态模型,对合闸过电压,单相短路接地时重合闸过电压进行了全面研究。最后分析了影响合闸过电压的主要因素。研究表明:过电压的幅值受合闸相角的影响很大,倍数在1.17 p.u^2.14 p.u之间,考虑避雷器的动作特性,应选择在210°~240°相角间合闸。重合闸过电压幅值小于首次合闸过电压幅值。送电时,应先合送端断路器,再合受端断路器,以免对受端母线PT造成损坏。全架空线合闸过电压幅值小于架空线-电缆混合输电方式下的过电压幅值;采用全电缆输电方式合闸时容易产生谐振过电压。通过倒送电的方式可降低电缆末端过电压倍数。

For researching the close overvoltage transient characteristic of headline-cable comprehensive transmission with double circuit transmission lines on same tower, a 220 k V power system is selected to build the transient model by EMTP. The characteristics of the close overvoltage and the reclose overvoltage after single phase grounding fault are comprehensive studied. Ultimate, the main factors effect on close overvoltage are analyzed. The results demonstrate that the amplitudes of overvoltage are greatly affected by phase angles with range of 1.17 p.u ~ 2.14 p.u. Considering the characteristic of arrester, it’s best to close at the phase angle of 210° ~240°. The amplitude of reclose overvoltage is lower than that of close overvoltage. It is appropriate to close the source side circuit breaker after closing the load side circuit breaker to protect the potential transformer joint with the bus of load. The amplitude of close overvoltage when the transmission line is whole headline is lower than that when the transmission line is headline and cable. It’s really possible to occur resonance overvoltage if the transmission line is the whole cable. The amplitude of the overvoltage can be reduced in inverse power transmission operation.