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G.8
SEL-351-5, -6, -7 Relay
Instruction Manual
Date Code 20070117
Setting SEL
OGIC
Control Equations
SEL
OGIC
Control Equations
When frequency goes above the corresponding pickup level 81D1P, Relay
Word bit 81D1T deasserts and an event report is generated (if the relay is not
already generating a report that encompasses the new transition). This allows
a recovery from an underfrequency condition to be observed. See
.
demonstrates the action of the falling-edge
operator \ on the underfrequency element in setting ER.
Figure G.2
Result of Falling-Edge Operator on a Deasserting Underfrequency
Element
SEL
OGIC
Control
Equation Operation
Example—Tripping
If tripping does not involve communications-assisted or switch-onto-fault trip
logic, the SEL
OGIC
control equation trip setting TR is the only trip setting
Note that
appears quite complex. But since tripping does not
involve communications-assisted or switch-onto-fault trip logic in this
example, respective SEL
OGIC
control equation trip settings TRCOMM and
TRSOTF are not used. The only effective input into logic gate OR-1 in
is SEL
OGIC
control equation trip setting TR.
TR =
51PT + 51GT + 50P1 * SH0
(fuse saving example)
TRCOMM =
0
(not used—set directly to logical 0)
TRSOTF =
0
(not used—set directly to logical 0)
ULTR =
!(51P + 51G)
(discussed in preceding subsection)
Analysis of SEL
OGIC
Control Equation Trip Setting TR
Again, the example trip equation is:
TR =
51PT + 51GT + 50P1 * SH0
The Relay Word bit definitions are:
In the trip equation, the AND operator * is executed before the OR operators
+,
50P1 * SH0
Element 50P1 can only cause a trip if the reclosing relay shot counter is at shot
= 0. When the reclosing relay shot counter is at shot = 0 (see
Word bit SH0 is in the following state:
SH0 = 1 (logical 1)
One Processing Interval
\81D1T
81D1T
One Processing Interval
Relay Word
Bit
Description
51PT
phase time-overcurrent element timed out
51GT
residual ground time-overcurrent element timed out
50P1
phase instantaneous overcurrent element asserted
SH0
reclosing relay shot counter at shot = 0
Содержание SEL-351-5
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