ABB Relion 670 Series Technical Reference Manual page 370

Section 6
Impedance protection
364
After the first slip, the signals ZONE1 or ZONE2 and – depending on the direction of
slip - either GEN or MOTOR are issued.
Every time pole slipping is detected, the impedance of the point where the slip line is
crossed and the instantaneous slip frequency are displayed as measurements.
Further slips are only detected, if they are in the same direction and if the rate of rotor
movement has reduced in relation to the preceding slip or the slip line is crossed in the
opposite direction outside ZA-ZB. A further slip in the opposite direction within Z
resets all the signals and is then signalled itself as a first slip.
The TRIP1 tripping command and signal are generated after N1 slips in zone 1,
providing the rotor angle is less than TripAngle. The TRIP2 signal is generated after
N2 slips in zone 2, providing the rotor angle is less than TripAngle.
All signals are reset if:
• the direction of movement reverses
• the rotor angle detector resets without a slip being counted or
• no rotor relative movement was detected during the time ResetTime.
1MRK505222-UUS C
-Z
A B
Technical reference manual