Earth Leakage Relay connection with normal CT

[IBRAHIM HAMEED]

Hi
Can I connect normal Current Transformers (CT) instead of Core Balance Current Transformers (CBCT) to Earth Leakage Relay..

Thanks

 

[Pete999]

Hi
Can I connect normal Current Transformers (CT) instead of Core Balance Current Transformers (CBCT) to Earth Leakage Relay..

Thanks

More detail required

 

[westward10]

No it should be CBCT. When there is no fault the output is zero, when a fault is detected this breaks the balance. All conductors pass through a CBCT, this is how it functions a CT generally only encompasses one conductor giving constant output to the CT when under load.

 

[IBRAHIM HAMEED]

Can I use normal CT with Earth Fault Relay ? Like DELAB Earth Fault Relay (EFR).

Normal CT I’m using here it’s CT used with Amp meter or Over Current Relay (OCR). So is there any other name instead of normal CT?

 

[westward10]

You would have to speak with Delab, earth leakage relays normally function by CBCTs but with new technology who knows whether a CT would suit.

 

[IBRAHIM HAMEED]

Thanks

Can you please explain me how does CBCT works and Normal CT works..

 

[westward10]

A CBCT is essentially a toroidal transformer, all conductors for the circuit pass through but not the earth. When no fault is present the vector sum of currents is null but when any earth leakage occurs the balance is broken and this is measured in the toroid giving secondary output to the leakage relay.
A CT transformer produces secondary output which is proportional to the primary and hence while the circuit being monitored is using current there is always secondary output. This can be used for overcurrent protective relays and whilst I am not 100% certain I do not think this will suit a leakage relay.
I am sure Delab will give much better advice than myself.

 

[IBRAHIM HAMEED]

Thanks for your information..

 

[IBRAHIM HAMEED]

Hi,
DELAB Earth Fault Relay (EFR) can connect with DELAB Over Current Relay (OCR), see the picture.. so, it means it’s connected using Normal CT? Right? But I know DELAB have there own CBCT for there ELR. My question is what is different between EFR and ELR? How is it functioning EFR using normal CT?

 

[westward10]

A CTs output is dictated by how it is wound but that is showing an earth fault relay which may not be the same for an earth leakage relay.

 

[IBRAHIM HAMEED]

Earth Leakage Relay and Earth Fault Relay is functioning different. Right?
Do Earth Fault Relay is work with normal C.T. not a CBCT. Right?
Can you please give me some more information on this ..
Thanks

 

[westward10]

The only way for certain is to contact Delab they will tell you exactly what is required.

 

[westward10]

I have just been looking online for the earth fault and earth leakage relays from Delab. Wiring diagrams differ as it shows a CBCT for the leakage relay and CTs for the fault relay.

 

[IBRAHIM HAMEED]

I’m posting this question because, one of my friend are studying Electrical program. There instructor saying CBCT will create using 4Nos of Normal CT. I’m also not believing this. That’s why I’m discussing. I think DELAB EFR will not working using CBCT. Only ELR will work. I’m right? And also DELAB ELR will not working using normal C.T. I’m right? What’s your idea?
Thanks

 

[westward10]

CTs can be used for overcurrent and fault relays but a CBCT is used for a leakage relay but never say never. If you used CTs for a leakage relays to me it will be constantly tripping, a CBCT doesn't give an output when no leakage is present.