1. Core identification is very impotent process during CT primary injection
2. CT 1 core -1 is used for line protection. Some times Core 2 and Core 1 will cores connect each other and can not identify during CT secondary or CT testing .
3. This can be only identified in Primary Injection.
4. Inject some current in primary side and measure the secondary current.
5. Short the used Tap say S1& S4 and inject the current in primary side. Now the current will be reduced in the relay side means current will dived. Some current will flow through shorted path and minimum current will follow through relay path. If the relay had more impedance the current will be zero.