3-30 Communications Date Code 970103
SEL-251, -2, -3 Instruction Manual
Shedding in Section 5: Applications). If this type of application is not needed,
then it is better to assign 52A or !52A to an input instead and avoid the 10-cycle
time delay. This time delay shows up in event reports and needs to be accounted
for when making setting 52ADO.
The 10-cycle delay affects the circuit breaker monitor, too. The TDUR timer
should be set somewhat greater than 10 cycles so that relay initiated circuit
breaker trips are counted as such and not as external circuit breaker trips. Also, if
an external trip occurs, no interrupted current values will likely be accumulated by
the circuit breaker monitor because of the 10-cycle time delay.
Refer to the Functional Specifications in Section 2: Specifications and be sure the global
settings you choose result in relay performance appropriate to your application.
The AUTO setting selects Port 1, Port 2, or both serial ports for automatically transmitted
messages. If relay Port 2 is connected to an SEL-RD or SEL-PRTU, the AUTO setting must
direct automatic messages to that port. The following table shows the effect of each possible
setting:
Auto Automatic Message
Setting Destination Port
1 1
2 2
3 1 and 2
Event summaries and self-test warning and failure reports are automatically transmitted from
port(s) designated automatic regardless of access level if the designated port is not timed out.
Enter zero as the timeout setting of the appropriate port if automatic transmissions will be
monitored by a dedicated channel or printed on a dedicated printer.
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