Ring CT

Stay away from it and get some formal training!

Dear Mr.Pwslack,

Thanks for your suggestion.

regards

G.Govarthinam

Contact the switchgear or CT manufacturers.

My advice is if it's working OK leave well alone.

Have you considered the possibility that this is a combination CT/VT (current AND voltage transformer)? These are sometimes used in billing metering applications.

In a ring CT, there is no need for a hard-wired connection to the primary. However, for a VT connected phase-to-ground, this terminal would be just what's expected. That is also suggested by the four secondary terminals (and earth terminal): two are for the secondary current connection, two for secondary voltage connection. Does the unit have a nameplate on it?

Very simple dear! It is called the "potential equalisation jumper" and is very common in all HV CTs (particularly, board mounted CTs).

If you dont have this jumper, the inner wall of the CT will be at the High Voltage Potential (6350 V for a 11kV System) and the outer wall of the CT will be at a different potential (close to earth potential, may be). The CT is normally a resin encapsulated one. The inner wall and the outer wall of the CT act as plates of a capacitor and the resin will be the dielectric of this capacitor. There would be capacitive charge & discharge currents through this insulation, which, over a period of time, would weaken the insulation.

By linking the inner bus bar and the outer wall of the CT using a low resistance wire, the inner and outer walls of the CT are kept at the same potential and thus there would not be any current flow thro the CT insulation. Thereby the life of the CT is enhanced.

Hope it is clear!

Dear Sir

Excellant answer sir.

This is my experience in one site.There I confused why this HT supply is connected to this CT outer wall.Now u clear my doubts.

Thank u very much sir

regards

G.Govarthinam