高速接地开关抑制超、特高压输电线路潜供电流的研究

High-speed Grounding Switches for Suppressing the Secondary Current in EHV and UHV Transmission Lines

为提高单相重合的成功率,进行了在不设并联电抗器的超、特高压短线路中借高速接地开关的分流和疏导功能来抑制潜供电流的研究。单相开断和线路两侧高速接地开关的闭合,形成后者与故障电弧通道对避雷线的3点并联接地方式,潜供电流的静电感应分量将因分流而被抑制。由于全线架设避雷线,闪络后的接地电阻实际上等于所有杆塔包括两侧变电所地网在内的全部接地电阻的并联值,它因很小而不起限流作用。分析表明,弧道电阻的限流作用亦可不计,但可显著增强接地开关的分流功能;在弧道电阻为零的最不利情况下,3点分流亦可将静电感应电流抑至低于原来的1/3,而且两侧高速接地开关的接地与线路漏抗形成平衡的电桥通道,使从线路终端返回的3倍零序电流被从桥臂导通,通过检流计支路即故障点的电磁感应电流就被抑制。最后,列出了接地开关电流的计算公式,同时指出,不容许只在线路一侧设置接地开关,因为电磁感应电流将会显著增大而使熄弧成为不可能。

In EHV and UHV transmission lines without shunt reactors,the secondary current （SC） can be suppressed by the use of high-speed grounding switches. This is achieved from the suppression of the electrostatic component of the SC through the three grounding pathways formed from the closed grounding switches together with the arc canal. With the lightning wires on all towers,the earthing resistance of a transmission line becomes equal to the equivalent resistance value of the parallel resistances of all towers including the grounding switches,and thus is too small to be used in current suppression. This paper shows that although ineffective in current suppression,the arc resistance can effectively enhance the shunting action of the grounding switches. The grounding switches and the line inductances form a balanced bridge circuit,leading to the fact that the zero-sequence current from the load transformer of the remote end passes only through the bridge arms. As a result,the electromagnetic component of the SC passing through the galvanometer circuit is suppressed. It is further pointed out that grounding switches should be installed on both line sides,because in one-side installation the magnetic induced current becomes significantly large.Finally,the formula for computing the maximun switching circuit is derived.