The zero sequence network for an Auto TX and for a Yg/Yg transformer both show that there is no connection to the ground bus (No), which means there will be no 0seq current flowing through that circuit (unless there is a Delta tertiary which does connect to the ground bus in the 0seq network).
My question is: for transformer differential application, for the differential CTs (connected Wye) from high side and low side of transformer, do we need to account for any 0seq current showing up on, say, lowside CT for a through fault and causing a 87 trip since high side CT didn't see any 3Io. Digital relays have the ability to select an option to filter 0seq current from these CT readings, but do I really have to filter this 0seq current in the case of Auto or Yg/Yg transformers?
Thanks for your input.
My question is: for transformer differential application, for the differential CTs (connected Wye) from high side and low side of transformer, do we need to account for any 0seq current showing up on, say, lowside CT for a through fault and causing a 87 trip since high side CT didn't see any 3Io. Digital relays have the ability to select an option to filter 0seq current from these CT readings, but do I really have to filter this 0seq current in the case of Auto or Yg/Yg transformers?
Thanks for your input.