# Difference between 51G, 51Gs, 51N Relays



## Dug (Nov 15, 2011)

I was wondering what the difference is between 51G, 51Gs, and 51N Relays? In addition, how do they relate to current transformers (How could you tell which is which based on a schematic of a power system or other ways)?


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## brian john (Mar 11, 2007)

A little google

http://www.aeusp.com/fundamentals/dvprgo.asp

The three most commonly used connections for ground-overcurrent relays are the residual connection (51N), the ground-sensor (balanced-flux or zero sequence) connection (50GS or 51GS), and the neutral current transformer connection (51G). 

It should be simple to identify the current transformers from the schematic (if the drawings are accurate).


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## sparky970 (Mar 19, 2008)

Dug said:


> I was wondering what the difference is between 51G, 51Gs, and 51N Relays? In addition, how do they relate to current transformers (How could you tell which is which based on a schematic of a power system or other ways)?


http://www.csanyigroup.com/ansi-standards-for-protection-devices


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## ponyboy (Nov 18, 2012)

highvoltpower said:


> It’s a standard device number, these types of device protect electrical systems and components from damage. 50G/51G is remaining current measured directly by a specific sensor and 51N is residual current calculated or measured by 3 phase current sensors.




This threads 5 years old


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