4-4
Protection and Control
BE1-951
D 3
D 2
D 1
D 0
A U T O
S G 3
S G 2
S G 1
S G 0
S G C
D2647-20
08-21-98
Figure 4-2. Input Control Mode 1
Figure 4-2 shows an example of how the inputs are read when the setting group control function logic is
enabled for Mode 1. Note that a pulse on the D3 input while D0 is also active doesn’t cause a setting group
change to SG3 because the AUTO input is active.
When the setting group control function block is enabled for Mode 2, inputs D0 and D1 are read as binary
encoded (Table 4-3). Inputs D2 and D3 are ignored. A new coded input must be stable for approximately
1 second for the setting group change to occur. After a setting group change occurs, no setting group
change can occur within two times the SGC alarm on time.
Table 4-3. Setting Group Binary Codes
Binary Code
Decimal Equivalent
Setting Group
D1
D0
0
0
0
SG0
0
1
1
SG1
1
0
2
SG2
1
1
3
SG3
When using control mode 2, the active setting group is controlled by a binary signal applied to discrete inputs
D0 and D1. This requires separate logic equations for only D0 and D1 if all setting groups are to be used.
Figure 4-3 shows how the active setting group follows the binary sum of the D0 and D1 inputs except when
blocked by the AUTO input. Note that a pulse on the D1 input while D0 is also active doesn’t cause a setting
change to SG3 because the AUTO input is active.
Automatic Setting Group Control
The relay has built in schemes that may be used to automatically change setting groups. One scheme is
based on the history of the current in the relay. Another scheme is based upon the status of the reclose
function (79). To enable automatic change of setting groups, setting group control must be enabled and the
<autologic> bit of SL-GROUP command must be a 1 and can be set as follows:
SL-GROUP = /0,,,,,/0.
When automatic control is enabled it holds precedence over all manual logic control.
The automatic setting group control may be used to force the relay to change to settings that will
automatically compensate for cold load pickup conditions. For instance, if the relay senses current drop
below a very small amount for a period of time, indicating an open breaker, then the relay may move to an
