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1 PRODUCT DESCRIPTION
where ZD is the angle of "maximum torque" and is equal to 65°.
The characteristic timer angle will be fixed at 115°. That is, the function will operate when the input signals are
within ±65° of each other.
If the faulted phase voltage magnitude is too low (as for a close-in Zone 1 fault), the phase directional function
will not operate. This might also occur for a remote fault when the relay is located near a strong source. There-
fore, if the phase voltage is less than the minimum threshold voltage, the positive-sequence memory voltage
from the ground Mho functions is used in place of the phase voltage to polarize the directional function.
c) RIGHT RESISTIVE BLINDER
The right resistive blinder is a two input phase angle comparator. The input signals for the comparator are:
Iφ '· RB 1 - Vφ
Operate:
Iφ '· RB 1
Polarize:
where:
The magnitude of RB 1 (Right Blinder for Zone 1) is the point at which the characteristic inter-
sects the R axis. The range of adjustment will be 0.1 to 500.0 Ω in 0.1 Ω steps.
The angle of RB 1 is be fixed based on the positive sequence line angle, the zero sequence
line angle, and the K 0 factor. The angle is:
⋅
2 POSSEQANG
----------------------------------------------------------------------------------------------------- -
Iφ ' is the compensated phase current, ( I
The characteristic timer angle will be fixed at 90°. For the Zone 1 ground function, the operate and polarizing
signals are:
'· RB 1 – V
Phase A:
I
A
A
'· RB 1
I
A
'· RB 1 – V
Phase B:
I
B
B
'· RB 1
I
B
'· RB 1 – V
I
Phase C:
C
C
'· RB 1
I
C
The LPS-D provides four zones of distance protection with overcurrent backup functions. The LPS-D is a
highly flexible system: along with predefined protection schemes, it also has the ability to be programmed by
the user. The custom programmability of the LPS-D is discussed in the next section.
The LPS-D pilot protection schemes are as follows:
•
Permissive Underreach Transfer Trip (PUTT)
•
Permissive Overreach Transfer Trip (POTT1)
•
Permissive Overreach Transfer Trip with blocking functions (POTT2)
•
Blocking
•
Hybrid
In addition, each of the above schemes includes up to four zones of step distance backup with individual timers
for phase and ground zones.
GE Power Management
⋅
K 0 ZERSEQANG
+
K 0
2
+
- I
) + K
A
0
where:
' = ( I
I
- I
) + K
1· I
A
A
0
0
0
' = ( I
I
- I
) + K
1· I
B
B
0
0
0
' = ( I
I
- I
) + K
1· I
C
C
0
0
0
K
1 = | K
1| – (ZERSEQANG – POSSEQANG)
0
0
LPS-D Line Protection System
1.2 INTRODUCTION
1• I
0
0
1.2.5 LINE PROTECTION SCHEMES
1
1-
9
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