What is ANSI 51N?
ANSI 50N/51N or 50G/51G – Earth fault Earth fault protection based on measured or calculated residual current values: ANSI 50N/51N: residual current calculated or measured by 3 phase current sensors. ANSI 50G/51G: residual current measured directly by a specific sensor.
What is 51N?
The phase relays are designated 51 and the residual ground overcurrent relay is designated 51N (both without instantaneous function). The bracketed denotes that there are three phase overcurrent relays and three CT’s.
What is the difference between 51N and 51G?
Quote: 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.
What is 50N and 51N?
Earth fault protection based on measured or calculated residual current values: ANSI 50N/51N: residual current calculated or measured by 3 phase current sensors. ANSI 50G/51G: residual current measured directly by a specific sensor.
What is 50G protection?
50G is the protection of neutral point on grounded-star side in typical Transformers of Iran distribution network. In this protection, a CT is placed between neutral point of the secondary star side and ground to measure zero sequence currents. This will detect faults and unbalanced conditions on the secondary to load.