3.41
Date Code 20110408 Instruction Manual SEL-551 Relay
Relay Elements and Logic
Demand Ammetering
Output Contacts OUT1 Through OUT4
Refer to Figure 3.23.
The execution of the serial port command PULSE n (n = OUT1–OUT4) asserts
the corresponding Relay Word bit (OUT1–OUT4) to logical 1. The assertion
of SEL
OGIC control equation setting OUTm (m = 1–4) to logical 1 also asserts
the corresponding Relay Word bit OUTm (m = 1–4) to logical 1.
The assertion of Relay Word bit OUTm (m = 1–4) to logical 1 causes the
energization of the corresponding output contact OUTm coil. Depending on
the output contact type (a or b), the output contact closes or opens as
demonstrated in Figure 3.23. An a-type output contact is open when the
output contact coil is de-energized and closed when the output contact coil is
energized. A b-type output contact is closed when the output contact coil is
de-energized and open when the output contact coil is energized.
Notice in Figure 3.23 that all four possible combinations of output contact coil
states (energized or de-energized) and output contact types (a or b) are
demonstrated. See Output Contact Jumpers (SEL-551 With the Conventional
Terminal Blocks Option) on page 2.15 for output contact type options.
ALARM Output Contact (SEL-551 Relay)
Refer to Figure 3.23 and Relay Self-Tests on page 8.16.
When the relay is OK, the ALARM output contact coil is energized. The alarm
logic/circuitry keeps the ALARM output contact coil energized. Depending on
the ALARM output contact type (a or b), the ALARM output contact closes or
opens as demonstrated in Figure 3.23. An a-type output contact is open when
the output contact coil is de-energized and closed when the output contact coil
is energized. A b-type output contact is closed when the output contact coil is
de-energized and open when the output contact coil is energized.
To verify ALARM output contact mechanical integrity, execute the serial port
command PULSE ALARM. Execution of this command momentarily de-
energizes the ALARM output contact coil.
The Relay Word bit ALARM is deasserted to logical 0 when the relay is OK.
When the serial port command PULSE ALARM is executed, the ALARM
Relay Word bit momentarily asserts to logical 1. Also, when the relay enters
Access Level 2, the ALARM Relay Word bit momentarily asserts to logical 1
(and the ALARM output contact coil is de-energized momentarily).
Notice in Figure 3.23 that all possible combinations of ALARM output contact
coil states (energized or de-energized) and output contact types (a or b) are
demonstrated. See Output Contact Jumpers (SEL-551 With the Conventional
Terminal Blocks Option) on page 2.15 for output contact type options.
Demand Ammetering
The demand ammetering settings (in Table 3.7) are available via the SET
command (see Table 4.1 and also Demand Ammetering Settings (see
Figure 3.24 and Figure 3.26) on page SET.5). Also refer to MET D Command
(Demand Ammeter) on page 5.15.
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