Date Code 20011205
Trip and Target Logic
5-13
SEL-311A Instruction Manual
Other Applications for the Target Reset Function
Refer to the bottom of Figure 5.1. The combination of the TARGET RESET pushbutton and the
TAR R
(Target Reset) serial port command is available as Relay Word bit TRGTR. Relay Word
bit TRGTR pulses to logical 1 for one processing interval when either the TARGET RESET
pushbutton is pushed or the
TAR R
(Target Reset) serial port command is executed.
Relay Word bit TRGTR can be used to unlatch logic. For example, refer to the breaker failure
logic in Figure 7.25 in
Section 7: Inputs, Outputs, Timers, and Other Control Logic
. If a
breaker failure trip occurs (SV7T asserts), the occurrence can be displayed on the front panel
with seal-in logic and a rotating default display (see
Rotating Default Display
in
Section 7
and
Section 11
, also):
SV8
= (SV8 + SV7T) * !TRGTR
DP3 =
SV8
DP3_1 = BREAKER FAILURE
DP3_0 = (blank)
Figure 5.4: Seal-in of Breaker Failure Occurrence for Message Display
If a breaker failure trip has occurred, the momentary assertion of SV7T (breaker failure trip) will
cause SV8 in Figure 5.4 to seal-in. Asserted SV8 in turn asserts DP3, causing the message:
BREAKER FAILURE
to display in the rotating default display.
This message can be removed from the display rotation by pushing the TARGET RESET
pushbutton (Relay Word bit TRGTR pulses to logical 1, unlatching SV8 and in turn deasserting
DP3). Thus, front-panel rotating default displays can be easily reset along with the front-panel
targets by pushing the TARGET RESET pushbutton.
Содержание SEL-311A
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