What is the difference between 51 g 51n relay

Please search in the Forum, we had a lot of threads on the topic. Shortly, I suggest: neutral EF protection, it's mean. So much terms about same. Best Regards. It backs up a faster relay which is often in a residual connection. The Stand by Earth fault protection receives current signal from CT in the transformer neutral. Operation of Stand by Earth fault protection is wired to trip the upstream Trafo primary breaker in addition to the Trafo secondary breaker.

Some times, Stage-1 element of the protection is also set and wired to open the bus coupler in case of 'bus coupler closed' operation. Hello Raghun. Your explanation conform with what I know. But what of Neutral Earth fault? Haisa: I think the question is not correctly worded or its comparing apples to oranges. A proper answerable question would be what is the difference between Neutral overcurrent 51N and ground earth fault overcurrent 51G protection.

OR you can ask what is the difference between a earth ground fault protection and a backup standby, if it a real term earth fault protection. You can deploy either kind of protection as primary or backup earth or neutral overcurrent protection. Only thing that a standby or back up protection will have higher slower setting than the primary settings so failing primary, the backup protection would come in picture.

As for 51N and 51G, the way modern relay manuals proposes, 51G actually measures the current in neutral using a CT residual CTs , where as 51N is where current in neutral is calculated by vector sum of the 3 phase over currents by the relay. ScottyUK has given a pretty good defintion. A CT on the Star point of the transformer will directly measure an earth fault, but it has no idea which feeder it is on, so it trips the transformer.

If it is it is a complete misnomer of something else. There is neutral overcurrent and there is earth ground over current. You are correct, when you think about it, it is a confusing term, but in our organisation we all know what it means. What I was saying is that the relay manufacturers call it different things. SEL and GE for example are in complete contradiction. But getting back to the orginal question , in our part of the world Neutral Earth Fault is a common term.

Just re-reading these posts. The moral of the story is that it doesn't matter what the term is, it is the application that counts. I am sure most of us have seen different terms used for the same application, and also the same term used for different applications - I certainly have on many occaisions.

Haisa, could you please give us some more detail of your questions application or context. Thanks for the explanations. Helps to get the terminology clear. Depends on who's definition you read. I prefer the terms residual current and neutral current. No confusion. Either can be backup standby? Quote: I prefer the terms residual current and neutral current. Please see page 4 and 5 of the linked pdf. Add a comment. Active Oldest Votes. The N, G, etc depicts not what the relay is, but how it is wired up.

The G is connected to three series connected current transformers, one on each phase of a 3-phase system: In both systems the relays are the same - it is merely the arrangement of current transformers and where they get their feed from that changes. Majenko Majenko 55k 8 8 gold badges silver badges bronze badges. The image you are showing belongs to a zero sequence CT however in the description you mentioned 3 individual CTs.

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The dual settings function does not apply to the ground-fault alarm function. When the dual settings function is enabled, ground-fault alarm settings are the same whether set A or set B settings are activated.

Function Settings. Ground-fault alarm settings on MicroLogic 2. Ground-fault alarm settings on MicroLogic 3. Earth-leakage alarm settings on MicroLogic 7.

Predefined Events. The function generates the following predefined event for MicroLogic 2. The function generates the following predefined event for MicroLogic 7. Predefined events cannot be modified by the user.