不同接地型式四极开关的选用

Selection of Four-pole Switch for Different Grounding Types

针对不同的接地型式,依据现行规范,介绍了四极开关的选择:①IT系统有中性线引出时,应采用四极开关;②TT系统应在隔离相线的同时隔离中性线;③在TN-C系统中必须选用三极开关;④TN-S系统可使用四极开关,但是开关的N极只能接N线,而不能接PEN或PE线,在有总等电位联结的TN-S系统建筑物内不必为电气检修安全而隔离中性线;⑤在TN-C-S系统的建筑物内不必为电气检修安全装设四极开关。

Selection of four-pole switches for different grounding types is described concerning with various grounding types according to the current codes, including： ①four-pole switches should be selected when there is outgoing neutral conductor in IT system; ② insulating neutral conductor while insulating phase line for IT system ; ③ three-pole switches must be selected for TN-C system; ④four-pole switches can be used for TN-S system but the N-pole of the switches can only be connected to N conductor instead of PEN or PE conductor and it is unnecessary to insulate the neutral conductor for the electrical maintenance safety in the buildings with TN-S system having main equipotential bonding; ⑤it is unnecessary to mount four-pole switches for the electrical maintenance safety in the buildings with TN-C-S system.