Schweitzer Engineering Laboratories SEL-351-5, Instruction Manual

Page: 236 / 706

5.34
SEL-351-5, -6, -7 Relay Instruction Manual
Date Code 20070117
Trip and Target Logic
Front-Panel Target LEDs
{TARGET RESET/LAMP
TEST} Front-Panel
Pushbutton
When the
{TARGET RESET/LAMP TEST}
front-panel pushbutton is pressed:
➤
All front-panel LEDs illuminate for one (1) second.
➤
All latched target LEDs (target LEDs numbered 2 through 13 in
Table 5.1 ) are extinguished (unlatched), unless a trip condition
is present in which case the latched target LEDs reappear in
their previous state.
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 7.26 . 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 on page 7.36 and
Rotating Default Display on page 11.12 , also):
SV8 =
(SV8 + SV7T) * !TRGTR
DP3 = SV8
DP3_1 =
BREAKER FAILURE
DP3_0 = NA (blank)
Figure 5.17 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 5.17 to seal-in. Asserted SV8 in
turn asserts DP3, causing the message:
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.
SV7T
Breaker Failure Trip
(= logical 1)
(= logical 0)
Target Reset
TRGTR
SV8
DP3 = SV8
DP3_1 = BREAKER FAILURE
DP3_0 = (blank)
BREAKER FAILURE