PURPOSE

BE1-67N Ground Directional Overcurrent Relays provide ground fault protection for transmission and

distribution lines by sensing the flow of ground (zero sequence) current into or out of protected zones.

Zero sequence quantities provide a secure reference for the directional element because these quantities

are defined by the total source impedance of the power system.

APPLICATION

BE1-67N Ground Directional Overcurrent Relays are recommended for multi-grounded systems to

provide coordination necessary to selectively trip the faulted line. A directional overcurrent relay operates

by comparing the measured current to a reference quantity to determine whether current is flowing into or

out of the protected zone. Reference quantity is also referred to as polarizing quantity.

BE1-67N relays use one of the following quantities for polarization:

• Zero sequence current

• Zero sequence voltage

• Dual zero sequence current and voltage

The polarizing quantity is field selectable using a switch mounted on the analog circuit board. When the

selected polarizing quantities are less than the minimum threshold, relay operation will be inhibited. When

using dual polarization, the relay will operate if either polarizing quantity is above minimum threshold.