GE L60, Инструкция по эксплуатации, Страница: 367 / 498

GE Multilin L60 Line Phase Comparison Relay 8-27
8 THEORY OF OPERATION 8.2 SINGLE-POLE TRIPPING
8
8.2.2 PHASE SELECTION
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.
Figure 8–20: PHASE SELECTION PRINCIPLE (ABC PHASE ROTATION)
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, e.g. 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 (
TRIP 1-POLE
or
TRIP 3-POLE
) and during open pole conditions
(
OPEN POLE OP
), the phase selector resets all its output operands and ignores any subsequent operations of the Distur-
bance Detector.
Figure 8–21: PHASE SELECTOR LOGIC
837725A1.CDR
AB,
ABG
CA,
CAG
BC,
BCG
AG
AG,
BCG
I
2F
I
2F
I
1F
I
0F
BG
CG,
ABG
CG
BG,
CAG
837027A3.CDR
TRIP 1-POLE
SRCn 50DD OP
TRIP 3-POLE
OPEN POLE OP
SRCn VT FUSE FAIL OP
DISTANCE SOURCE:
AND
FLEXLOGIC OPERANDS
FLEXLOGIC OPERAND
FLEXLOGIC OPERAND
SETTING
DELAY
DELAY
I_1
V_0
V_1
V_2
I_0
I_2
FLEXLOGIC OPERANDS
PHASE SELECT AG
RESET
START
PHASE SELECTOR
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
4 cycles
500 ms
0
0
OR