G.9
Date Code 20080213 Instruction Manual SEL-351A Relay
Setting SELOGIC Control Equations
SEL
OGIC Control Equations
and an instantaneous trip results. This logic is commonly used in fuse-saving
schemes for distribution feeders.
If the reclosing relay shot counter advances to shot = 1 for the reclose that
follows the trip, Relay Word bit SH0 is in the following state:
SH0 = 0 (logical 0)
If maximum phase current is above the phase instantaneous overcurrent
element pickup setting 50P1P for the reoccurring fault, Relay Word bit 50P1
is in the following state:
50P1 = 1 (logical 1)
With SH0 = 0 and 50P1 = 1, the ANDed combination results in:
50P1 * SH0 = 1 * 0 = 0 (logical 0)
and no trip results from phase instantaneous overcurrent element 50P1.
A trip will eventually result if time-overcurrent element 51PT or 51GT times
out. If residual-ground time-overcurrent element 51GT times out, Relay Word
bit 51GT is in the following state:
51GT = 1 (logical 1)
When shot = 1, SH0 = 0 and the result is:
TR = 51PT + 51GT + 50P1 * SH0 = 0 + 1 + 1 * 0 = 0 + 1 + 0 = 1
and a time-delayed trip results from residual-ground time-overcurrent element
51GT.
Set an Output Contact for Tripping
To assert output contact OUT101 to trip a circuit breaker, make the following
SEL
OGIC control equation output contact setting (see Output Contacts on
page 7.31):
OUT101 = TRIP
All SELOGIC Control
Equations Must Be
Set
All SELOGIC control equations must be set one of the following ways (they
cannot be “blank”):
➤ Single Relay Word bit (e.g., 52A = IN101)
➤ Combination of Relay Word bits (e.g., TR = 51PT + 51GT +
50P1 * SH0)
➤ Directly to logical 1 (e.g., 67P1TC = 1)
➤ Directly to logical 0 (e.g., TRCOMM = 0)
Set SELOGIC Control Equations Directly to 1 or 0
SELOGIC control equations can be set directly to:
1 (logical 1) or 0 (logical 0)
instead of with Relay Word bits. If a SEL
OGIC control equation setting is set
directly to 1, it is always “asserted/on/enabled.” If a SEL
OGIC control equation
setting is set equal to 0, it is always “deasserted/off/disabled.”
Under the SHO Command (Show/View Settings) on page 10.25, note that a
number of the factory SEL
OGIC control equation settings are set directly to 1
or 0.
NOTE: SELOGIC control equation
torque control settings (e.g., 67P1TC,
51P1TC) cannot be set directly to
logical 0.
Courtesy of NationalSwitchgear.com
To Next Page