CT for restricted earth fault (REF) protection

In summary, the person is seeking advice on whether the nominal primary CT used for REF protection must be the same. They provide information about the CTs they currently have and ask for a sample three line diagram of a 500kV Substation. They also mention that they are new to this topic and may need help.
  • #1
saragiha
3
0
Does somebody could advice me, whether the nominal primary CT to be used for REF protection must be same?

The CT I have now as follow:
Power Transformer: 60MVA, 150/20kV, Ynyn(0)d1
CT on 20kV switchgear 2000/5, class 5P20
CT on neutral Power Transformer: 1200/5, class X
Relay to be used: Areva Micom P632
 
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  • #2
Generally in high impedance Restricted Earth Fault (REF) protection, the ratio of involved CTs must be same, but in low impedance type it can be difference.
For more information about low and high differential protection also REF you can refer to Protection Riddle No.59 and other riddles from http://electrical-riddles.com
 
  • #3
Dear msj,

thank you, helpfully
 
  • #4
three line diagram of 500kV Substation

Hi...

Does somobody have a sample three line diagram of 500kV Substation?
I will have a disscussion of this topic, unfortunately I'm new on this topic.

Regards,
Saragiha
 

1. What is CT for restricted earth fault (REF) protection?

CT stands for current transformer, which is a device used in electrical power systems to measure the current flowing through a circuit. REF protection is a type of protection used to detect and isolate earth faults in power systems.

2. How does CT for REF protection work?

CTs are placed around the conductors of a power system and measure the current flowing through them. In the event of an earth fault, the current flowing through the faulted conductor will be different from the current flowing through the other conductors, and this difference is detected by the CTs. This information is then used to trip the circuit breaker and isolate the fault.

3. What are the advantages of using CTs for REF protection?

CTs are highly sensitive and can accurately detect even small earth faults, allowing for quick and effective isolation of faults. They are also cost-effective and can be easily installed in existing power systems.

4. Are there any limitations to using CTs for REF protection?

CTs can only detect earth faults within the zone of protection where they are installed. This means that faults outside of this zone may not be detected, and additional protection measures may be needed for full system protection.

5. How can the accuracy of CTs for REF protection be ensured?

CTs must be regularly tested and calibrated to ensure their accuracy. This can be done using specialized test equipment and following industry standards and guidelines. It is also important to ensure that the CT is properly sized and installed for the specific power system it is being used in.

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