GE Multilin
L90 Line Current Differential System
9-25
9 THEORY OF OPERATION
9.3 DISTANCE ELEMENTS
9
9.3.4 MEMORY POLARIZATION
All distance functions use memory polarization. The positive-sequence voltage – either memorized or actual – is used as a
polarizing signal. The memory is established when the positive-sequence voltage remains above 80% of its nominal value
for five power system cycles. The memory voltage is a three-cycle old voltage.
Once established, the memory is applied for the user-specified time interval. The memory timer is started when the voltage
drops below 80% of nominal or when the user-programmable condition is asserted to force memory polarization. After the
memory expires, the relay checks the magnitude of the actual positive-sequence voltage. If it is higher than 10% of nomi-
nal, the actual voltage is used; if lower, the memory voltage continues to be used.
A provision is added to force self-polarization from any user-programmable condition.
The memory-polarized mho has an extra directional integrity built-in as illustrated below. The self-polarized mho character-
istic is shifted in the reverse direction for a forward fault by an amount proportional to the source impedance, and in the for-
ward direction for a reverse fault.
Table 9–4: DIRECTIONAL QUADRILATERAL GROUND DISTANCE FUNCTIONS
CHARACTERISTIC
COMPARATOR INPUTS
LIMIT ANGLE
Reactance
I
Z – V
j
I_0
e
j
or j
I_2
e
j
COMP LIMIT
Directional
I_0
Z
D
V_1M
DIR COMP LIMIT
Directional
I_2
Z
D
V_1M
DIR COMP LIMIT (removed when 3I_0 > OC SUPV
and I_2 < CUTOFF)
Right Blinder
I
Z
R
– V
I
Z
R
90°
Left Blinder
I
Z
L
– V
I
Z
L
90°
Fault-type
I_0
I_2
50° (removed during open pole conditions or when
3I_0 > OC SUPV and I_2 < CUTOFF)
Zero-sequence
I_0
Z
D
–V_0
90° (zones and higher only; removed for zones 2 and
higher during open pole conditions)
Table 9–5: NON-DIRECTIONAL MHO PHASE DISTANCE FUNCTIONS
CHARACTERISTIC
COMPARATOR INPUTS
LIMIT ANGLE
Offset mho
I
Z – V
I
Z
REV
– V
COMP LIMIT
Table 9–6: NON-DIRECTIONAL MHO GROUND DISTANCE FUNCTIONS
CHARACTERISTIC
COMPARATOR INPUTS
LIMIT ANGLE
Offset mho
I
Z – V
I
Z
REV
– V
COMP LIMIT
Fault-type
I_0
I_2
50° (removed during open pole conditions or when 3I_0 > OC
SUPV and I_2 < CUTOFF)
Table 9–7: NON-DIRECTIONAL QUADRILATERAL PHASE DISTANCE FUNCTIONS
CHARACTERISTIC
COMPARATOR INPUTS
LIMIT ANGLE
Forward Reactance
I
Z – V
I
Z
COMP LIMIT
Reverse Reactance
I
Z
REV
– V
I
Z
REV
COMP LIMIT
Right Blinder
I
Z
R
– V
I
Z
R
90°
Left Blinder
I
Z
L
– V
I
Z
L
90°
Table 9–8: NON-DIRECTIONAL QUADRILATERAL GROUND DISTANCE FUNCTIONS
CHARACTERISTIC
COMPARATOR INPUTS
LIMIT ANGLE
Forward Reactance
I
Z – V
j
I_0
e
j
or j
I_2
e
j
COMP LIMIT
Reverse Reactance
I
Z
REV
– V
–j
I_0
e
j
or –j
I_2
e
j
COMP LIMIT
Right Blinder
I
Z
R
– V
I
Z
R
90°
Left Blinder
I
Z
L
– V
I
Z
L
90°
Fault-type
I_0
I_2
50° (removed during open pole conditions or
when 3I_0 > OC SUPV and I_2 < CUTOFF)
Summary of Contents for UR Series L90
Page 652: ...A 16 L90 Line Current Differential System GE Multilin A 1 PARAMETER LISTS APPENDIX A A ...
Page 772: ...B 120 L90 Line Current Differential System GE Multilin B 4 MEMORY MAPPING APPENDIX B B ...
Page 802: ...C 30 L90 Line Current Differential System GE Multilin C 7 LOGICAL NODES APPENDIX C C ...
Page 812: ...D 10 L90 Line Current Differential System GE Multilin D 1 IEC 60870 5 104 APPENDIX D D ...
Page 824: ...E 12 L90 Line Current Differential System GE Multilin E 2 DNP POINT LISTS APPENDIX E E ...
Page 834: ...F 10 L90 Line Current Differential System GE Multilin F 3 WARRANTY APPENDIX F F ...
Page 846: ...xii L90 Line Current Differential System GE Multilin INDEX ...
