Sensitive earth fault protection - medium voltage
Sensitive earth fault protection - medium voltage
(OP)
I've got a protective issue question, I'll appreciate it if anyone can help me or point me in some direction.
With a high impedance grounding system (secondary of trsf grounded through resistors) in a medium voltage system, on what kind of earth fault protection does IEC insist? (I'm looking for any IEC-standard, but information from an IEEE-viewpoint will also be fine) Is earth fault protection on the residual connection (3 CT's) enough, or is sensitive earth fault protection (Balancing core / ring CT) essential? The question is related to feeders of overhead lines, permanent cables and trailing cables.
Many thanks
Regards
With a high impedance grounding system (secondary of trsf grounded through resistors) in a medium voltage system, on what kind of earth fault protection does IEC insist? (I'm looking for any IEC-standard, but information from an IEEE-viewpoint will also be fine) Is earth fault protection on the residual connection (3 CT's) enough, or is sensitive earth fault protection (Balancing core / ring CT) essential? The question is related to feeders of overhead lines, permanent cables and trailing cables.
Many thanks
Regards
Ralph






RE: Sensitive earth fault protection - medium voltage
For a low-resistance grounding system (50 A to 400 A), standard ground overcurrent detection methods can be used.
I am speaking from a practical application viewpoint for US installations. I know nothing about IEC requirements.
RE: Sensitive earth fault protection - medium voltage
With regard to protection, if the current are low, current based protection is not reliable and hence residual overvoltage is sensed and annunciated.
In case the currents are as high as say 25A, core balance CTs can be included in each of the outgoing feeders and trip of the respective feeder issued on sensing the earth fault.
Trust the above is helpful.
RE: Sensitive earth fault protection - medium voltage