Why VT Secondary Yellow phase is earthed?

[yesukannan]

Hi all,
I have a scheme in which the Y-Y VT secondary yellow phase is earthed. and is fed to a 2watt meter energy meter. can you explain why this is done so.




regards,
kannan

 

[Knobhead]

If one leg of the VT network is not earthed it can lead to floating voltages in the metering circuits. The floating voltage will not in it’s self cause a problem with the metering as the phase to phase voltage remains a constant ratio to the primary. But it is confusing to anyone testing.

Yellow has by tradition been the ground reference point, no complicated reason behind it. It’s one of the classic “it’s always been like that”. I’ve worked on gear installed in the 1930’s, guess what? Yellow was always the one.

Don’t ask me why it is, and until you asked, I’ll admit I’ve never even questioned it.