Date Code 20001006
Inputs, Outputs, Timers, and Other Control Logic
7-25
SEL-351 Instruction Manual
Timer pickup setting SV8PU is set greater than the pulse width of the SCADA contact
(Figure 7.20). This allows only one active setting group change (e.g., from setting Group 1 to 4)
for each pulse of the SCADA contact (and subsequent assertion of input IN5). The function of the
SEL
OGIC
Control Equations in Table 7.5 becomes more apparent in the following example
scenario.
Start Out in Setting Group 1
Refer to Figure 7.22.
The relay has been in setting Group 1 for some time, with timer logic output SV8T asserted to
logical 1, thus enabling SEL
OGIC
Control Equation setting SS4 for the assertion of input IN5.
Switch to Setting Group 4
Refer to Figure 7.22.
The SCADA contact pulses input IN5, and the active setting group changes to setting Group 4
after qualifying time setting TGR (perhaps set at a cycle or so to qualify the assertion of setting
SS4). Optoisolated input IN5 also has its own built-in debounce timer (IN5D) available (see
Figure 7.1).
Note that Figure 7.22 shows both setting Group 1 and setting Group 4 settings. The setting
Group 1 settings (top of Figure 7.22) are enabled only when setting Group 1 is the active setting
group and likewise for the setting Group 4 settings at the bottom of the figure.
Setting Group 4 is now the active setting group, and Relay Word bit SG4 asserts to logical 1.
After the relay has been in setting Group 4 for a time period equal to SV8PU, the timer logic
output SV8T asserts to logical 1, thus enabling SEL
OGIC
Control Equation setting SS1 for a new
assertion of input IN5.
Note that input IN5 is still asserted as setting Group 4 is activated. Pickup time SV8PU keeps the
continued assertion of input IN5 from causing the active setting group to revert back again to
setting Group 1 for a single assertion of input IN5. This keeps the active setting group from being
changed at a time interval less than time SV8PU.
Switch Back to Setting Group 1
Refer to Figure 7.22.
The SCADA contact pulses input IN5 a second time, and the active setting group changes back to
setting Group 1 after qualifying time setting TGR (perhaps set at a cycle or so to qualify the
assertion of setting SS1). Optoisolated input IN5 also has its own built-in debounce timer (IN5D)
available (see Figure 7.1).
Summary of Contents for SEL-351
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