SEL
OGIC
Control Equations
4-7
SEL-300G Instruction Manual
Date
Code
20060731
In this setting example, the unlatch condition comes true only when
both
the 51N (neutral time-
overcurrent element pickup indication) and 50L (lowest phase overcurrent element pickup
indication) Relay Word bits deassert:
ULTR1 = !(51N + 50L) = NOT(51N + 50L)
As stated previously, the logic within the parentheses is performed first. In this example, the
states of Relay Word bits 51N and 50L are ORed together. Then the NOT operator is applied to
the logic resultant from the parentheses.
If either one of 51N or 50L is still asserted [e.g., 51N = 1 (logical 1)], the unlatch condition is not
true:
ULTR1 = NOT(51N + 50L) = NOT(1 + 0) = NOT(1) = 0
If
both
51N and 50L are deasserted [i.e., 51N = 0 and 50L = 0 (logical 0)], the unlatch condition
is true:
ULTR1 = NOT(51N + 50L) = NOT(0 + 0) = NOT(0) = 1
and the trip condition can unlatch, subject to other conditions in the trip logic (see Figure 4.6).
All SEL
OGIC
Control Equations Must Be Set
All SEL
OGIC
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., TR1 = SV3 + SV4 + 46Q2T + 81D1T + 81D2T)
•
directly to logical 1 (e.g., 46QTC = 1)
•
directly to logical 0 (e.g., SV6 = 0)
Set SEL
OGIC
Control Equations Directly to 1 or 0
SEL
OGIC
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.”
SEL
OGIC
Control Equation Limitations
Any single SEL
OGIC
control equation setting is
limited to 17 Relay Word bits
that can be
combined together with the SEL
OGIC
control equation operators listed in Table 4.1. If this limit
must be exceeded, use a SEL
OGIC
control equation variable (SEL
OGIC
control equation settings
SV1 through SV12) as an intermediate setting step.
For example, assume that a trip equation (such as SEL
OGIC
control equation trip setting TR1)
needs more than 17 Relay Word bits in its equation setting. Instead of placing all Relay Word
bits into TR1, program some of them into the SEL
OGIC
control equation setting SV1. Next use
the resultant SEL
OGIC
control equation variable output (Relay Word bit SV1) in the SEL
OGIC
control equation trip setting TR1.
Note that the SEL
OGIC
control equation variables (SEL
OGIC
control equation settings SV1
through SV16) are processed after the trip equation (SEL
OGIC
control equation trip setting TR).
Summary of Contents for SEL-300G
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