Current in relay earth fault element
Current in relay earth fault element
(OP)
We have a 10MVA 33000/11000 volt transformer connected to a 27-panel 11000 volt board. The transformer is fitted with various types of relays including a GEC K-Series 3-phase and earth fault relay.
Recently, it has been noticed that a current reading of 4 amperes can be seen on the 'Neutral' (Io). The currents in the phase elements are approximately 200A.
Relays on other transformers and feeders connected to the same 27-panel board all have a zero reading of current in the 'Neutral'.
Is this indictative of a pending earth fault?
Many thanks in anticipation,
Paul Cole
Recently, it has been noticed that a current reading of 4 amperes can be seen on the 'Neutral' (Io). The currents in the phase elements are approximately 200A.
Relays on other transformers and feeders connected to the same 27-panel board all have a zero reading of current in the 'Neutral'.
Is this indictative of a pending earth fault?
Many thanks in anticipation,
Paul Cole






RE: Current in relay earth fault element
RE: Current in relay earth fault element
Thanks for the reply.
The system is 3-phase 3-wire. 'Neutral' is the terminology used by GEC Alsthom to describe the current in the earth fault element, it has the symbol Io.
Paul
RE: Current in relay earth fault element
RE: Current in relay earth fault element
Offhand, it seems like 4 amperes CT residual primary current is of no significant concern compared to 200 amps per phase in a transformer winding of ~525 amperes.
Have harmonic contents been measured? The 4 amperes is probably just "garbage," and normally shouldn't have any undesirable effects on the system.
RE: Current in relay earth fault element
You may want to check the pickup setting for this element to make sure it isn't in danger of operating.
RE: Current in relay earth fault element