Sel 551 - Page 66

3.28
SEL-551 Relay Instruction Manual Date Code 20110408
Relay Elements and Logic
Reclosing Relay
If the circuit breaker is open (IN1 = logical 0) when the TRIP Relay Word bit
asserts (logical 0 to logical 1 transition), the relay goes to the Lockout State.
This helps prevent reclose initiation for such conditions as a flashover in the
tank of an open circuit breaker.
Additional Settings Example 1
The preceding settings example initiates open interval timing on rising-edge
of the TRIP Relay Word bit. The following is an example of reclose initiation
on the opening of the circuit breaker.
Input IN1 is connected to a 52a circuit breaker auxiliary contact.
With setting:
79RI = !IN1
the transition of the IN1 Relay Word bit from logical 1 to logical 0 (breaker
opening) initiates open interval timing. Setting 79RI looks for a logical 0 to
logical 1 transition, thus Relay Word bit IN1 is inverted in the 79RI setting
[!IN1 = NOT(IN1)].
The reclose initiate supervision setting 79RIS supervises setting 79RI. With
settings:
79RI = !IN1
79RIS = TRIP
the transition of the IN1 Relay Word bit from logical 1 to logical 0 initiates
open interval timing only if the TRIP Relay Word bit is at logical 1 (TRIP =
logical 1). Thus, the TRIP Relay Word bit has to be asserted when the circuit
breaker opens in order to initiate open interval timing. With a long enough
setting of the Minimum Trip Duration Timer (TDURD), the TRIP Relay Word
bit will still be asserted to logical 1 when the circuit breaker opens (see
Figure 3.13).
If the TRIP Relay Word bit is at logical 0 (TRIP = logical 0) when the circuit
breaker opens (logical 1 to logical 0 transition), the relay goes to the Lockout
State. This helps prevent reclose initiation for circuit breaker openings caused
by trips external to the relay.
Other Settings Considerations
In the preceding factory setting example, the reclose initiate supervision
setting (79RIS) includes input IN1, that is connected to a 52a breaker auxiliary
contact.
79RIS = IN1
If a 52b breaker auxiliary contact is connected to input IN1, the reclose initiate
supervision setting (79RIS) would be set as follows:
79RIS = !IN1
In the preceding additional setting example 1, the reclose initiate setting
(79RI) includes input IN1, that is connected to a 52a breaker auxiliary contact.
79RI = !IN1
If a 52b breaker auxiliary contact is connected to input IN1, the reclose initiate
setting (79RI) would be set as follows:
79RI = IN1