Answer / electric dood

Phasing out is a test performed on energized multi-phase circuits from different sources to ensure that like phases are connected. For example:

Red - Red
White - White
Blue - Blue

This is usually done at the point of interconnection like an isolator or bus section, ring main unit. Tools used are phasing sticks or voltmeters.

Safety precautions are always observed. Rubber gloves are worn. Phasing sticks do not physically touch the energized wires. Being in the presence of the electrical field is all that is required. Most times what is measured is phase angle. In a balanced 3-phase system each consecutive phase is spaced 120 degrees apart.

A voltmeter can be used also. The voltmeter would measure the stepped down voltages from VTs of the respective circuits. Between two phases that are in phase with the same magnitude of voltage gives a measurement of 0V.

The capacity of the transformer is 20/25 MVA, Ratio is 132/11 KV, Vactor group YNyno. and impedance is 10.07%. As per the calculation the secondary current is 1312.2Amps. The maximum fault current the transformer should sustain is 13.030KA. How many times the transformer should sustain the maximum short circuit current of 13.030KA over a period up 1 Year. The transformer is repaired one & 10 Years old.

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