5.5 GROUPED ELEMENTS
GND DIST Z2 DELAY:
This setting enables the user to delay operation of the distance elements and implement a stepped distance backup protec-
tion. The distance element timer applies a short drop out delay to cope with faults located close to the boundary of the zone
when small oscillations in the voltages and/or currents could inadvertently reset the timer.
GND DIST Z2 BLK:
This setting enables the user to select a FlexLogic™ operand to block the given distance element. VT fuse fail detection is
one of the applications for this setting.
GROUND DIRECTIONAL SUPERVISION:
A dual (zero- and negative-sequence) memory-polarized directional supervision applied to the ground distance protection
elements has been shown to give good directional integrity. However, a reverse double-line-to-ground fault can lead to a
maloperation of the ground element in a sound phase if the zone reach setting is increased to cover high resistance faults.
Ground distance Zone 2 uses an additional ground directional supervision to enhance directional integrity. The element's
directional characteristic angle is used as a "maximum torque angle" together with a 90° limit angle.
The supervision is biased toward operation in order to avoid compromising the sensitivity of ground distance elements at
low signal levels. Otherwise, the reverse fault condition that generates concern will have high polarizing levels so that a cor-
rect reverse fault decision can be reliably made.
Figure 5–29: GROUND DIRECTIONAL SUPERVISION SCHEME LOGIC – Z2
GND DIST Z2
GND DIST Z2 PKP A
GND DIST Z2 PKP B
GND DIST Z2 PKP C
Figure 5–28: GROUND DISTANCE Z2 OP SCHEME
V_0 > 5 Volts
L90 Line Differential Relay
GND DIST Z2 OP A
GND DIST Z2 OP B
GND DIST Z2 OP C
GND DIST Z2 OP
Pickup 4.5 cycles, Reset 1.0 cycle
GND DIST Z2 DIR
GE Power Management