3.4
SEL-551 Relay Instruction Manual Date Code 20110408
Relay Elements and Logic
Optoisolated Inputs
There are no optoisolated input settings such as:
IN1 . =
IN2 =
Optoisolated inputs IN1–IN2 receive their function by how their corresponding
Relay Word bits IN1–IN2 are used in SEL
OGIC control equations.
Factory Settings
Example
Relay Word bit IN1 is used in the factory settings for the SELOGIC control
equations circuit breaker status setting:
52A = IN1
Connect input IN1 to a 52a circuit breaker auxiliary contact. See Close Logic
on page 3.20 and Reclosing Relay on page 3.22 for more information on
SEL
OGIC control equations setting 52A.
Input IN1 is also used in other factory settings discussed later in this section
(i.e., SEL
OGIC control equation settings 79RIS and DP2). Just because Relay
Word bit IN1 is assigned to the circuit breaker status setting 52A, it does not
mean that Relay Word bit IN1 cannot be used in other SEL
OGIC control
equation settings.
In the factory settings, Relay Word bit IN2 is not used.
Additional Settings
Examples
52b Circuit Breaker Auxiliary Contact
If a 52b circuit breaker auxiliary contact is connected to input IN1, the setting is
changed to:
52A = !IN1 [!IN1 = NOT(IN1)]
Time-Qualify Optoisolated Inputs
If an input needs to be debounced or time-qualified more than the built-in
0.25 cycles, assign the input to a SEL
OGIC Variables timer (see Figure 3.21):
SV6 = IN1
The output of the timer (Relay Word bit SV6T) can then be used in place of
Relay Word bit IN1. For example, the timer output can be assigned to the
SEL
OGIC control equations circuit breaker status setting:
52A = SV6T
Other Examples
Other example SELOGIC control equation settings in this section use the
optoisolated inputs IN1–IN2 for such applications as breaker failure initiation,
time-overcurrent element torque control, reclose initiation, and reclose timing
stall condition.
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