Schweitzer Engineering SEL-387-0, Instruction Manual

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4.7
Date Code 20170601 Instruction Manual SEL-387-0, -5, -6 Relay
Control Logic
Multiple Setting Groups
The REMOTE switch position de-energizes all relay inputs, thus placing all of
the SS
n variables in state 0. With none of the SS n variables asserted, the
GRO n command, or the
{GROUP}
pushbutton on the front panel, can be used
to change the setting group. With the switch in any other position, 1 through 6,
the
GRO n and {GROUP} functions will not effect a group change.
The setting TGR, the group change delay setting, should be set long enough so
that the switch, as it is rotated from one position to another, will not remain at
any intermediate position long enough to make any setting group change. For
example, in rotating from position 1 to position 5, the switch must pass
through positions 2, 3, and 4. It should not remain in 2, 3, or 4 for longer than
TGR during this process, or it may produce multiple group changes before it
finally gets to position 5.
The settings in Table 4.3 are made in the Global settings area.
CHSG Relay Word Bit
Asserts During
Setting Group
Changes
The Relay Word bit CHSG is asserted whenever a setting group change is in
process. It is defined in
Table 4.9 and Table 4.11 as “Timing to change setting
groups.” When group changes are initiated through one of the SS n SEL
OGIC
control equation settings, CHSG is asserted as soon as the new SS n bit is
asserted and the relay has made the decision to change groups. It deasserts
when the SG
n bit for the new group agrees with the SS n bit, indicating that the
relay has changed to the newly requested group number. For example, assume
the relay is in group 1. The active group bit SG1 equals one, while other SG
n
bits are zero. All of the SS n bits are also zero. SS4 is asserted, requesting a
change to group 4. Since SS1 (same group as the active group) is not asserted,
the group change process is initiated, and CHSG is asserted at the same time
as SS4. After the group change is made, SG1 will deassert and SG4 will
assert, indicating the relay is now in group 4. When this agreement of SS4 and
SG4 occurs, CHSG will deassert to indicate the relay is no longer in the
process of changing groups.
When the active group bit SG n and its associated SS n bit are both asserted, for
example SG1 and SS1, the relay does not respond to the assertion of a new
SS
n bit, such as SS3, and no group change will occur. Similarly, the CHSG bit
will not assert along with SS3, since the SG1 and SS1 bits are in agreement.
This agreement acts like a continuous “reset” applied to the CHSG bit.
In applications where a system-related condition requires that a change of
setting groups must be done quickly and automatically, this would likely be
accomplished via a contact input to the relay, which would assert an SS
n bit.
In such cases, it may be desirable to immediately block some relay elements
as soon as the change is needed to prevent misoperation. This could easily be
done via the CHSG bit. CHSG could be used, for example, to supervise the
tripping variable for differential trips. The default TR4 setting is TR4 = 87R +
87U; this could be changed to TR4 = 87R * !CHSG + 87U * !CHSG. CHSG
optimizes (in this case minimizes) the amount of time to block TR4, since
CHSG asserts exactly when the change of groups is needed, and deasserts
exactly when the change has taken place.
Table 4.3 SEL
OGIC
Control Equation Settings for Rotating Selector Switch
SS1 = !IN103 * !IN102 * IN101 = NOT(IN103) * NOT(IN102) * IN101
SS2 = !IN103 * IN102 * !IN101 = NOT(IN103) * IN102 * NOT(IN101)
SS3 = !IN103 * IN102 * IN101 = NOT(IN103) * IN102 * IN101
SS4 = IN103 * !IN102 * !IN101 = IN103 * NOT(IN102) * NOT(IN101)
SS5 = IN103 * !IN102 * IN101 = IN103 * NOT(IN102) * IN101
SS6 = IN103 * IN102 * !IN101 = IN103 * IN102 * NOT(IN101)