How to coordinate Bus couplers

[RAgrawal]

I want help from you people to understand the philosophy adopted to coordinate relay settings of Bus couplers.

I am talking about a bus, which has 3 incomers, and each incomer is separeted by a Bus coupler. So there are 2 bus couplers and 3 incomers in a bus and normally bus couplers are closed making all the incomers parallel.

 

[RalphChristie]

RAgrawal

What kind of bus-zone protection do you have at the Bus couplers? It would be a type of differential protection, most probably a high-impedance sceme for older installations, and a high- or low-impedance sceme for new installations. Thus if all the incomming currents equal the outgoing currents in a certain zone, there would be no relay-operation.

Normally you would use a kind of zone-protection on each busbar, in your case there would be three different zones. Thus for a fault on one zone you would open all the incoming and outgoing feeders on that zone to isolate the fault. Take for instance a fault on the middle-busbar. If the bus-protection sense a fault, both bus couplers, the middle incomer and the middle-feeder have to open to isolate the fault. Zone protection covers just a certain zone, and need not to coordinate with downstream devices, thus it can be as fast as possible to minimize damage.

You can also view:

http://www.areva-td.com/servlet/Con...uct_Detail&c=AGF_Product&cid=1089880316992&am

p;rid=&lid=en&pid=1017999014820&tab=Chapters&id=1056536208254

(copy and paste whole address)
Download chapter 15 (Busbar protection)

Regards