Phase Selection - GE UR series Instruction Manual

8.2 SINGLE-POLE TRIPPING
The L60 uses phase relations between current symmetrical components for phase selection. First, the algorithm validates if
there is enough zero, positive, and negative-sequence currents for reliable analysis. The comparison is adaptive; that is,
the magnitudes of the three symmetrical components used mutually as restraints confirm if a given component is large
enough to be used for phase selection. Once the current magnitudes are validated, the algorithm analyzes phase relations
between the negative and positive-sequence currents and negative and zero-sequence currents (when applicable) as illus-
trated below.
BC,
BCG
Due to dual comparisons, the algorithm is very secure. For increased accuracy and to facilitate operation in weak systems,
the pre-fault components are removed from the analyzed currents. The algorithm is very fast and ensures proper phase
selection before any of the correctly set protection elements operates.
Under unusual circumstances such as weak-infeed conditions with the zero-sequence current dominating during any
ground fault, or during cross-country faults, the current-based phase selector may not recognize any of the known fault pat-
tern. If this is the case, voltages are used for phase selection. The voltage algorithm is the same as the current-based algo-
rithm; for example, phase angles between the zero, negative, and positive-sequence voltages are used. The pre-fault
values are subtracted prior to any calculations.
The pre-fault quantities are captured and the calculations start when the disturbance detector (50DD) operates.
When the trip command is issued by the trip output logic (
( ), the phase selector resets all its output operands and ignores any subsequent operations of the distur-
OPEN POLE OP
bance detector.
FLEXLOGIC OPERANDS
TRIP 1-POLE
TRIP 3-POLE
OPEN POLE OP
FLEXLOGIC OPERAND
8
SRCn 50DD OP
FLEXLOGIC OPERAND
SRCn VT FUSE FAIL OP
SETTING
DISTANCE SOURCE:
I_0
I_1
I_2
V_0
V_1
V_2
8-36
AB,
ABG
BG
AG
I
2F
CG
CA,
CAG
Figure 8–29: PHASE SELECTION PRINCIPLE (ABC PHASE ROTATION)
OR
DELAY
0
4 cycles
Figure 8–30: PHASE SELECTOR LOGIC
L60 Line Phase Comparison System
CG,
ABG
I
1F
BG,
CAG
or
TRIP 1-POLE TRIP 3-POLE
DELAY
0.5 cycles
RESET
0
DELAY
0
AND START
500 ms
8 THEORY OF OPERATION

8.2.2 PHASE SELECTION

AG,
BCG
I
2F
I
0F
837725A1.CDR
) and during open pole conditions
FLEXLOGIC OPERANDS
PHASE SELECT AG
PHASE SELECT BG
PHASE SELECT CG
PHASE SELECT AB
PHASE SELECT BC
PHASE SELECT CA
PHASE SELECT ABG
PHASE SELECT BCG
PHASE SELECT CAG
PHASE SELECT 3P
PHASE SELECT SLG
PHASE SELECT MULTI-P
PHASE SELECT VOID
837027A4.CDR
GE Multilin