Date Code 20011026
Specifications
2-21
SEL-321/321-1 Instruction Manual
Figure 2.2: SEL-321 SEL
OGIC
Control Equations Overview
Programming SEL
OGIC
control equations is easy.
1. Use the SET G command to enter your input assignments into the global settings of the relay.
(“Global” means that only one set of input assignments is permitted. There are six sets of
logic and element settings.) Table 2.4 lists all available input assignment choices.
2. Determine the relay element combinations you want for the following four purposes:
Communications-aided trip
(set with MTCS logic variable)
Unconditional trip
(set with MTU logic variable)
Switch-onto-fault trip
(set with MTO logic variable)
Event report triggering
(set with MER logic variable)
3. Determine the output functions you require, including tripping, keying communications, etc.
First, refer to the rear-panel wiring diagram, and choose the specific output contacts you
wish to assign to various functions. For example, assume you want OUT1 and OUT2 to be
three-pole trip outputs, OUT3 to follow the CLOSE command, and OUT4 to key
communications. Any output contact may be assigned for tripping duty.
When you are designing your trip condition, event trigger, and output logic, you may use
AND, OR, and NOT operators to develop virtually any combination of elements for each
condition. There are also five intermediate variables (V, W, X, Y, and Z) which you can first
program and subsequently use in Steps 2 and 3 above. Three of these (X, Y, and Z) also
have independent general-purpose time delay pickup/dropout timers. The outputs after these
timers (XT, YT, and ZT) are also available.
4. Use the SET L command to enter your logic equations for V, W, X, Y, Z, MTCS, MTU,
MTO, MER, and each of the outputs (except ALARM). Each setting group has its own
associated logic equations.
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