Series Couplers

This practice allows remote locations the ability to control power feed into panels and subpanels. If you had two or more feeders for a facility and had the ability to power the facility from either one through the use of couplers, you would want the ability to open or close the feed at the remote service.

If a facility allowed distant couplers to control the feed to another building or plant location that they had no communication with, it may cause damage or injury to the remote section or personnel.

An operator would close the feed and then either close the remote feed themselves or contact a remote operator to do so.

Is Bus A and Bus B located in the same switchboard? I feel one B/C shall do the job in such case.

However, if Bus-A belongs to Swbd # X and Bus-B belongs to another Swbd # Y (in same or distant location), interconnection of these two buses requires Bus coupler on either sides for positive isolation in case one has to work on the interconnected part with both Swbd # X(Bus-A) & Swbd # Y(Bus-B) live.

Couplers are also used to "couple" the two buss sides together for purposes of transmitting low level data throughout a facility. In this case no power can cross over from one buss to another, but the data transmission can occur.

Is this what you are referring to:

http://www.rpsswitchgear.co.nz/products/bus_coupler.html

...or is it a data coupler as WJM states?

the two buses belong to different switchboads and the two switchboards are located next to each other. also, the two couplers have communication with control room for ON/OFF and are not used for any other data communication purpose.

The way the couplers (in North America it is called Tie-In-Breaker) are installed (located next to each other), I don't see any other reason for having two couplers in series except they facilitate the maintenance with completely de-energizing them with having power in one of the switchboards.

- MS

generally two coupler connected in series for maintainance purpose where bus shutdown is not possible(for chemeical/processing factories). with one bus shutdown you can do maintainance on connected coupler with that bus & vice versa.