Power Factor Meter Testing

Procedure Photos & Videos

CT CORE IDENTIFICATION

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.

Tertiary winding in Power Transformer

The Tertiary winding with DELTA connection is normally used in Yy connection power & Auto transformers for following purpose.

1. The Tertiary winding used as a path for the Zero sequence current  during secondary loaded with unbalanced load. Normally the primary neutral point would not be connected with system  ground. Tertiary winding one DELTA point is connected with system ground which is prevent the shifting of secondary neutral point and  the voltages become unsymmetrical during unbalanced load condition. Other wise the zero sequence current will flow through the secondary neutral connected with Transformer Tank and tank will get heat up.

2. When an external Earth Fault occurs, the resulting zero sequence currents  flow through the OPEN DELTA winding to ground.This prevents the zero sequence currents from flowing through the Transformer. This also prevents abnormal DIFFERENTIAL RELAY operation of the Transformer for external faults.

3. Some times a external resistor is used in the path of Delta to ground connection to limit the Current circulation. 

4. Some times this winding is used as a station supply and surge arrester are used to prevent the surges from the load side. 

Protection Arrangement

The CT in the closed conductor will detect asymmetrical-faults such as turn-to-turn, or winding-to-winding and connected with instantaneous over current 51 and other and one core is connected with winding Temperature meter.

The CT in the Grounding conductor will detect ground-faults in the delta winding.