Schweitzer Engineering Laboratories SEL-351-5, Instruction Manual

Page: 337 / 706

8.17
Date Code 20070117
Instruction Manual SEL-351-5, -6, -7 Relay
Breaker Monitor, Metering, and Load Profile Functions
Station DC Battery Monitor
Output Contact Type Considerations (a or b)
Refer to Output Contacts on page 7.32 (especially Note 2 in Figure 7.28 ).
Consider the output contact type (a or b) needed for output contact
OUT106
in
the bottom of Figure 8.10 (dc voltage alarm example).
If SEL
OGIC
control equation setting OUT106 is asserted (OUT106 = SV4T =
logical 1; dc voltage OK), the state of output contact
OUT106
(according to
contact type) is:
➤
closed (a-type output contact)
➤
open (b-type output contact)
If SEL
OGIC
control equation setting OUT106 is deasserted (OUT106 = SV4T
= logical 0; dc voltage not OK), the state of output contact
OUT106
(according
to contact type) is:
➤
open (a-type output contact)
➤
closed (b-type output contact)
If the relay loses power entirely, all output contacts deassert, and the state of
output contact
OUT106
(according to contact type) is:
➤
open (a-type output contact)
➤
closed (b-type output contact)
Additional
Application
Other than alarming, the dc voltage elements can be used to disable reclosing.
For example, if the station dc batteries have a problem and the station dc
battery voltage is declining, drive the reclosing relay to lockout:
79DTL =
!SV4T + ...
[= NOT(SV4T) + ...]
Timer output SV4T is from the bottom of Figure 8.10 . When dc voltage falls
below pickup DCHIP, timer output SV4T drops out (= logical 0), driving the
relay to lockout:
79DTL = !SV4T + ... = NOT(SV4T) + ... = NOT(logical 0) + ... = logical 1
Circuit breaker tripping and closing requires station dc battery energy. If the
station dc batteries are having a problem and the station dc battery voltage is
declining, the relay should not reclose after a trip—there might not be enough
dc battery energy to trip a second time after a reclose.
View Station DC
Battery Voltage
Via Serial Port
See MET Command (Metering Data) on page 10.19 . The MET command
displays the station dc battery voltage (labeled VDC).
Via Front Panel
The information available via the previously discussed MET serial port
command is also available via the front-panel
{OTHER}
pushbutton. See
Figure 11.3 .