50/51G and 50/51N
- Thread starter sahafi
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brian john
Senior Member
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- Leesburg, VA
Re: 50/51G and 50/51N
Are you trying to protect the transformer from intermnal GF/faults you would be best served by a didfferentiaal relay.
Are you trying to protect the transformer from intermnal GF/faults you would be best served by a didfferentiaal relay.
Re: 50/51G and 50/51N
Device 50 is a IEEE Device number defined as an "Instantaneous overcurrent relay, or rate-of-rise relay that functions instantaneously on an excessive value of current, or on an excessive rate of current rise, thus indication a fault in the apparatus of circuit being protected.
Device 51 is an AC time overcurrent relay which is a relay with either a definite or inverse time characteristic that functions when the current in the AC circuit exceeds a predetermined value.
'G'=Generator, or ground
'N'=Network, or neutral
Suffix "N" generally used in reference to "G" for devices connected in the secondary neutral current transformers, or in the secondary of a current transformer whose primary winding is located in the neutral of a machine or power transformer, except in the case of transmission line relaying, where the suffix "G" is more commonly used for those relays which operate on ground fault.
The actual protective relay being applied would most likely be in the "CO" relay family used with a suitable sized CT on the neutral.
However, the selection as well as the setting values of the device would be the responsibility of a electrical engineering consultant who has experience in protective relaying and distribution system coordination.
Device 50 is a IEEE Device number defined as an "Instantaneous overcurrent relay, or rate-of-rise relay that functions instantaneously on an excessive value of current, or on an excessive rate of current rise, thus indication a fault in the apparatus of circuit being protected.
Device 51 is an AC time overcurrent relay which is a relay with either a definite or inverse time characteristic that functions when the current in the AC circuit exceeds a predetermined value.
'G'=Generator, or ground
'N'=Network, or neutral
Suffix "N" generally used in reference to "G" for devices connected in the secondary neutral current transformers, or in the secondary of a current transformer whose primary winding is located in the neutral of a machine or power transformer, except in the case of transmission line relaying, where the suffix "G" is more commonly used for those relays which operate on ground fault.
The actual protective relay being applied would most likely be in the "CO" relay family used with a suitable sized CT on the neutral.
However, the selection as well as the setting values of the device would be the responsibility of a electrical engineering consultant who has experience in protective relaying and distribution system coordination.
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