Best Location for CT Grounding

[SMB1]

Hi everyone,

I would like to know where is the best location to ground the CT secondary "one point only"

is it at SWGR CT Box, LCC or relay panel?

and why?

thanx

 

[dpc]

http://www.netaworld.org/files/ItemFileA877.pdf

It depends....

"Theory is when you know all and nothing works. Practice is when all works and nobody knows why. In this case we have put together theory and practice: nothing works... and nobody knows why! (Albert Einstein)

 

[SMB1]

thank you dpc

 

[slavag]

Hi SMB1
Please see attached thread, it was intresting.
thread238-211553.

BTW, I start change my opinion .
Best Regards.
Slava

 

[hilotech]

Your wye or delta connection should be made at your ct termial block.Your ground should be located in the breaker if the relays are in the breaker. If the relays are in a control house then the ground should be there. This will reduce the chance of your differential relays operating for an external fault.

 

[scottf]

I agree with all of the above points in regards to CTs for protection applications.

I'll throw in one thought though for CTs for high-end metering applications.

For EHV metering applications, particularly generation metering, shielded/twisted-pair cabling is used between CTs in the switch-yard and the meter in the control house. The CT secondaries are still connected in a grounded-wye, but the common point is made at the meter and then grounded there. The concept of only 1 grounding point still applies, as multiple grounding points is also a "no-no" for metering circuits due to the concerns of circulating ground current distorting the meter readings.