Answer / raj

Voltage is applied through open delta PT only.

Answer / ekanadam patlavath

dc 110 voltage used for relay operating. for reverse power
operetion

Answer / nur.asidik

to make polarisation

Answer / rajesh bodduna

Open delta voltage is used to check the direction of fault,
i.e secondary voltages are connected in delta fashion with
open at one end . . The directional earth fault relay will
get volatge from open delta and currents from CT's as inputs.

Answer / hamed

Directional Earth fault relay requires to Inputs line
Current and line voltage.
So in case of Current there are standard output of any CT
(either 1A or 5A).And for Voltage Inputs there is a
Standard Potential transformers witch give 110/(sqr.root of
3).

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