GE D30 Instruction Manual page 257

5 SETTINGS
Figure 5–60: GROUND DISTANCE ZONE 1 TO ZONE 3 SCHEME LOGIC
GROUND DIRECTIONAL SUPERVISION:
A dual (zero-sequence 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 resis-
tance faults.
Ground distance zones 2 and higher use 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.
SETTING
Distance Source
= V_0
= I_0
Figure 5–61: GROUND DIRECTIONAL SUPERVISION SCHEME LOGIC
GE Multilin
V_0 > 5 volts
RUN
OR
Zero-sequence
directional characteristic
t
FLEXLOGIC OPERAND
OPEN POLE OP
Co-ordinating time:
pickup = 1.0 cycle, reset = 1.0 cycle
D30 Line Distance Protection System
5.6 GROUPED ELEMENTS
FLEXLOGIC OPERAND
TIMER
GND DIST Z2 DIR SUPN
AND
pickup
t
reset
5
837009A7.CDR
5-125