Electronic – the purpose of these PTs

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What is the purpose of these PTs installed on the two coupled busbars? And we have whole panels in the HV room for these PTs. Kindly explain. (Photo attached)

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Best Answer

Looks like a wye primary with two wye secondaries and a open-delta secondary.

Without seeing schematics it's hard to say what each winding is used for. My guess:

  • Wye 1: Metering, synchronism check.
  • Wye 2: Protection.
  • Open delta: for residual voltage measurement (earth fault protection) or for connection of a damping resistor to mitigate ferroresonance. Note that the screen displays "3U0" which is the residual voltage, i.e. 3 × the "zero sequence" voltage U0.
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