What is the definition of ANSI 67N/67NC - Directional earth fault?

Earth fault protection, with selective tripping according to fault current direction.
3 types of operation:

• type 1: the protection function uses the projection of the I0 vector
• type 2: the protection function uses the I0 vector magnitude with half-plane tripping zone
• type 3: the protection function uses the I0 vector magnitude with angular sector tripping zone

ANSI 67N/67NC type 1
Directional earth fault protection for impedant, isolated or compensated neutral systems, based on the projection of measured residual current

ANSI 67N/67NC type 2
Directional overcurrent protection for impedance and solidly earthed systems, based on measured or calculated residual current.
It comprises an earth fault function associated with direction detection, and picks up if the earth fault function in the chosen direction (line or busbar) is activated.

ANSI 67N/67NC type 3
Directional overcurrent protection for distribution networks in which the neutral earthing system varies according to the operating mode, based on measured
residual current.
It comprises an earth fault function associated with direction detection (angular sector tripping zone defined by 2 adjustable angles), and picks up if the earth fault
function in the chosen direction (line or busbar) is activated.
This protection function complies with the CEI 0-16 Italian specification.

Released for:Schneider Electric Nigeria