CT Switching Relays

Try Google first. I found this in first 3 results:

http://www.alstom.com/WorkArea/DownloadAsset.aspx?id=8589939358

thanks

http://www.rmspl.com.au/handbook/6rmatrix_pre_defined_common.pdf

CT switching relays are used when the CT inputs change from one relay to another relay.. for example, in bus bar protection for double bus bar systems, we will be having main protection for bus 1 and main protection for bus 2 separately. All the feeders could be connected to either bus 1 or bus 2 through disconnectors. The auxilairy contacts of the disconnectors decide to which protection relays(i.e. bus 1 or bus 2 protection relays) the CT inputs from the specific feeder should be feeding. So the aux.contacts of the disconnectors helps in activating the switching relays to toggle the ct connections between bus 1 and bus 2 protection relays. This is done to prevent unwanted trippings of the feeders which are connected to healthy bus during trippings of feeders which are all connected to faulty bus.

Hope it helps.

-Vijay