站用10 kV系统中性点接地方式对避雷器地电位升安全限值的影响

Influence of Neutral Grounding Mode on the Safety Limit of Lightning Arrester Ground Potential Rise in Station 10 kV system

随着电网容量变大和新型电力系统的发展,站用10 kV系统中性点接地方式发生改变,仍沿用系统中性点不接地方式下避雷器耐受接地网地电位(U_(GPR))升高的安全限值可能会导致避雷器在其他接地方式下出现安全事故。采用电磁暂态程序ATP-draw可以搭建不同中性点接地方式下U_(GPR)反击避雷器的模型,通过校核避雷器在U_(GPR)作用下动作过程中的吸收能量,得到了中性点接地方式对避雷器耐受U_(GPR)安全限值的影响规律:中性点不接地时,避雷器耐受U_(GPR)安全限值为10~23 kV,随线路对地电容变大而减小;中性点经消弧线圈接地时,U_(GPR)在消弧线圈和线路对地电容的串联回路中产生振荡,导致避雷器耐受U_(GPR)安全限值更低,安全限值主要由脱谐度与阻尼率决定,典型值为8~9.5 kV;中性点经电阻接地时,U_(GPR)大部分耦合至高压母线,使避雷器耐受U_(GPR)安全限值更高,并随线路对地电容和中性点电阻的增大而减小,大电阻接地工况下的典型值大于15 kV,小电阻接地工况下的典型值大于25 kV。

With the increase of grid capacity and the development of new power systems,the neutral grounding mode of the 10 kV station system has changed.The ground potential rise(U_(GPR))safety limit of the arrester’s tolerance under the neutral ungrounded system may lead to safety accidents of the arrester under other grounding modes.The electromagnetic transient program ATP-draw can be used to build the model of U_(GPR)counterattack arrester under different neutral grounding modes.By checking the energy absorbed by the arrester under the action of U_(GPR),the influence of neutral grounding mode on the safety limit of the arrester’s tolerance to U_(GPR)is obtained as follows:Under the neutral ungrounded system,the U_(GPR)safety limit of the arrester is 10~23 kV,which decreases with the increase of the line capacitance to the ground.Under the neutral grounding via arc suppression coil system,U_(GPR)oscillates in the series circuit of the arc suppression coil and the line’s capacitance to the ground,resulting in a lower safety limit of the arrester to withstand U_(GPR).The safety limit is mainly determined by the out-of-resonance degree and damping rate,and the typical value is 8~9.5 kV.Under the neutral grounding via resistance system,most of the U_(GPR)is coupled to the high voltage bus,so that the safety limit of the arrester to withstand U_(GPR)is higher,which decreases with the increase of the line capacitance to the ground and the neutral resistance.The typical value of the high resistance grounding condition is greater than 15 kV,and the typical value of the low resistance grounding condition is greater than 25 kV.