Schweitzer Engineering Laboratories SEL-311L, Instruction Manual, Page: 321 / 734

Date Code 20010625 Breaker Monitor and Metering Functions 8-17
SEL-311L Instruction Manual
DCLO > DCHI (Bottom of Figure 8.10)
Output contact OUT106 asserts when:
DCHIP
b
V
dc
b
DCLOP
Pickup settings DCLOP and DCHIP are set such that output contact OUT106 asserts when dc
battery voltage stays between allowable limits.
If the relay loses power entirely (V
dc
= 0 Vdc)
V
dc
= < DCHIP
then output contact OUT106 should logically deassert (according to bottom of Figure 8.10), and
this is surely what happens for a total loss of power (all output contacts deassert on total loss of
power).
Output Contact Type Considerations (“a” or “b”)
Refer to Output Contacts in Section 7: Inputs, Outputs, Timers, and Other Control Logic
(especially Note 2 in Figure 7.26). 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) + ...]