山区35KV电网中性点新型运行方式研究

山区35 KV电网正常整定消弧线圈档位后,线路三相对地电容不对称会使三相电压严重不对称,甚至虚幻接地,虽可用增大消弧线圈脱谐度予以改善,但会导致线路雷击跳闸率居高不下。为此提出电网正常断开消弧线圈(中性点绝缘)运行而在线路单相接地后快速投入消弧线圈的适于山区35 KV电网的新型复合运行方式,电弧熄灭,故障消除即退出消弧线圈。以此兼顾了故障消弧而正常电压对称的要求,研究表明暂态过程中过电压和冲击电流水平并不很高。新运行方式可提高山区35 KV电网运行水平,减低线路雷击跳闸率。

New Neutral Point Operation Method of 35 kV Grids in Mountainous Area

The unbalanced 35 kV grids due to unsymmetrical capacitance values gives difficulty in neutral point operation in mountainous area.Improving compensation of suppressing coil can rectify imbalance of voltage but bring up new problems that suppressing coil can not extinguish grounding arc effectively in fault.When neutral point adopts an insulation operation method,the symmetry of phase voltage conforms to routine operation demand.When neutral point adopts grounding operation method via suppressing coil,the regulating scale of suppressing coil can meet the demands of extinguishing the grounding arc effectively in fault and decreasing the velocity of recovery in fault phase voltage.If single phase-to-ground fault occurs in the grids which neutral point adopts insulating operation method,the fault must not be smoothed away immediately.This paper proposes a new neutral point operation method that neutral point is insulated in routine operation and suppressing coil grounding is used in fault.This new neutral operation method not only can rectify imbalance of voltage but also can extinguish the grounding arc effectively in fault.The EMTP simulation indicates that new neutral operation method can improve the lightning withstand level and decrease trip-out rate of grids.