Ground fault monitors

[RRaghunath]

Specialised relay vendors supply CBCT and the Ground fault monitor relay as a package. The relay settings are sensitive in terms of primary current directly and no CT ratio etc. details are to be provided as input to the relay. No issue.
For sensitive earth fault protection, normally I am used to seeing a low CT ratio but here I find the CT ratio to be 600/1A while the setting range is 3mA to 16A.
Appreciate if some one could help my understanding the above. Thanks.

 

[krisys]

Raghun, are you looking for MV application or LV application? The Schneider CSH120 and CSH200 Core balance CTs are used in MV as well as LV systems. They have odd ratio of 1/470 and suitable for Schneider Sepam series relays. They can be set for very sensitive values. I used to provide the relay settings for such installations. I heard from the site guys that the wires connecting these CTs to relay is a special cable (may be screened cable like the signal cable).

For LV application Schneider Vigirex unit is also such type of package. Hope this would help you.

Just google it, you will find it.

 

[RRaghunath]

Krisys, Thanks for response. It is about LV system. What could be the reason for using high ratio such as 600/1A for CBCT when the required setting is some thing like 300mA!
Thanks