Open-Delta PT Circuit

[CuriousElectron]

Greetings,
Why do we typically see an open-delta PT having one of the secondary phases grounded? What is the purpose of grounding, to prevent phases from floating? We'd still get the same line-line voltage between VAB, VBC, and VCA.
Thanks,
EE

 

[TugboatEng]

Grounding is typically done to create a low resistance fault path to trigger a magnetic trip on a breaker and isolate the faulted circuit. Open Delta does not have a neutral so a line leg must be used.

 

[LionelHutz]

On PT circuits it's to keep them from floating. Most all control voltage type TX secondaries need to be grounded.