F-2
Setting Negative-Sequence Overcurrent Elements
Date Code 20001006
SEL-351 Instruction Manual
To avoid having negative-sequence time-overcurrent element 51QT with such low time-dial
settings trip for this transient negative-sequence current condition, make settings similar to the
following:
SV6PU = 1.50 cycles
(minimum response time; transient condition lasts
less than 1.5 cycles)
SV6 = 51Q
(run pickup of negative-sequence time-overcurrent
element 51QT through SEL
OGIC
Control Equation
variable timer SV6)
TR = ..+51QT*SV6T+..
(trip conditions; SV6T is the output of the SEL
OGIC
Control Equation variable timer SV6)
Figure F.1: Minimum Response Time Added to a Negative-Sequence Time-Overcurrent
Element 51QT
Continue reading in
Coordinating Negative-Sequence Overcurrent Elements
in this appendix for
guidelines on coordinating negative-sequence time-overcurrent elements and a following
coordination example.
C
OORDINATING
N
EGATIVE
-S
EQUENCE
O
VERCURRENT
E
LEMENTS
The following coordination guidelines and example assume that the negative-sequence overcurrent
elements operate on 3I
2
magnitude negative-sequence current and that the power system is radial.
The negative-sequence overcurrent elements in the SEL
-
351 Relay operate on 3I
2
magnitude
negative-sequence current.
The coordination example is a generic example that can be used with any relay containing
negative-sequence overcurrent elements that operate on 3I
2
magnitude negative-sequence current.
The SEL
-
351 Relay can be inserted as the feeder relay in this example. Note that the overcurrent
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