Disconnecting switch

A switch used to keep an electric circuit "open" or "closed" and is used in high-voltage circuits of 3,000 volts to ultra-high-voltage circuits of 500,000 volts. For this reason, a disconnecting switch is not required to extinguish arcs when opening and closing. However, it must be able to cut off small charging currents over a very short range up to a circuit breaker with current-cutting capabilities. For this reason, some high-voltage disconnecting switches are equipped with an arc-extinguishing horn, and are sometimes called line switches. There are single-pole and three-pole disconnecting switches, and single-pole disconnecting switches are often operated manually using an insulating rod (hook metal fitting) ( Figure A ), while three-pole disconnecting switches are often operated by compressed air or electromagnetic force and can also be operated remotely.

A disconnecting switch is used to remove voltage from a part of an electric circuit and keep it in the "open" state during maintenance and inspection of power equipment or when changing the configuration of the electric circuit. For this reason, it is used in series with a circuit breaker or major equipment of an electric circuit or as a link between busbars. Also, as shown in Figure B , when busbar A and busbar B are connected by another busbar connecting circuit, the opening and closing operation to switch from busbar A to busbar B is performed by a disconnecting switch.

[Masami Okamura and Yoshifumi Oura]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

3000ボルトの高圧電路から50万ボルトなどの超々高圧電路に至るまで使われる、電路の「開」状態、あるいは「閉」状態を保持するために用いられる開閉器。このことから、断路器は開閉時のアークを消弧する責務はもたせていない。しかし、電流遮断能力のある遮断器に至るごく短い範囲の小さな充電電流程度は遮断できなければならない。このため高電圧用では消弧ホーンを取り付けたものがあり、これを線路開閉器とよぶ場合もある。断路器には単極と三極とがあり、単極断路器は絶縁棒（フック金具）を使う人力操作によるものが多い（図A）が、三極断路器は圧縮空気または電磁力操作によるものが多く、遠隔操作も可能である。

　断路器は電路の一部を無電圧にし電力設備の保守点検、あるいは電路構成変更の際「開」状態を保持するために用いられる。このため、遮断器や電路主要機器と直列構成あるいは母線間の連係として用いられる。また図Bで示すように、甲母線と乙母線が別の母線連絡電路等で連結されている状態では、甲母線から乙母線に切り替えるような開閉操作は、断路器で行う。

［岡村正巳・大浦好文］

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