4.80
SEL-787 Relay
Instruction Manual
Date Code 20081022
Protection and Logic Functions
Logic Settings (SET L Command)
shows an example of the effects of the input precedence, with
SC01PV set to 7. The vertical dashed line indicates the relationship between
SC01CU first being seen as a rising edge and the resultant outputs. This
indicates that there is no intentional lag between the control input asserting
and the count value changing. Most of the pulses in the diagram are on every
second processing interval. The “one processing interval” valley is an example
where the CD and CU pulses are only separated by one processing interval.
Figure 4.52
Example of the Effects of the Input Precedence
SC
nn
CD
Rising-Edge Input
Count Down decrements the counter (follows
SEL
OGIC
setting).
SC
nn
R
Active High Input
Reset counter to zero (follows SEL
OGIC
setting)
SC
nn
QU
Active High
Output
This Q Up output asserts when the Preset Value
(maximum count) is reached (SC
n
= SC
n
PV,
n
= 01 to
32).
SC
nn
QD
Active High
Output
This Q Down output asserts when the counter is equal
to zero (SC
n
= 0,
n
= 01 to 32).
SC
nn
Output Value
This counter output is an analog value that may be
used with analog comparison operators in a SEL
OGIC
control equation and viewed using the
COU
command.
Table 4.31
Order of Precedence of the Control Inputs
Order
Input
1
SC
nn
R
2
SC
nn
LD
3
SC
nn
CU
4
SC
nn
CD
Table 4.30
Counter Input/Output Description
(Sheet 2 of 2)
Name
Type
Description
SC01QU
SC01QD
Relay
Word
Bits
SC01R
SC01LD
SC01CU
SC01CD
SEL
OGIC
Settings
SC01PV = 7
Setting
SC01
Analog
= Sample
One Processing Interval
Two Processing Intervals
6
5
4
3
2
1
0
Summary of Contents for SEL-787
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