8.16
SEL-351A Relay
Instruction Manual
Date Code 20080213
Breaker Monitor and Metering
Station DC Battery Monitor (Not in SEL-351A-1)
Figure 8.10
Create DC Voltage Elements With SEL
OGIC
Control Equations
DCLO < DCHI (Top of
)
Output contact
OUT106
asserts when:
V
dc
≤
DCLOP or V
dc
≥
DCHIP
Pickup settings DCLOP and DCHIP are set such that output contact
OUT106
asserts when dc battery voltage goes below or above allowable limits.
If the relay loses power entirely (V
dc
= 0 Vdc)
V
dc
= < DCLOP
then output contact
OUT106
should logically assert (according to the top of
), but cannot because of the total loss of power (all output contacts
deassert on total loss of power). Thus, the resultant dc voltage element at the
bottom of
would probably be a better choice. See following
discussion.
DCLO > DCHI (Bottom of
)
Output contact
OUT106
asserts when:
DCHIP
≤
V
dc
≤
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 the bottom
), and this also happens for a total loss of power (all output
contacts deassert on total loss of power).
SV4PU
SV4DO
SV4
SV4T
SV4T
DCHI
SV4 = DCLO + DCHI
OUT106 = SV4T
DCLO
DCLOP
DCHIP
DCLOP
<
DCHIP
Vdc
SV4PU
SV4DO
SV4
DCLO * DCHI
SV4 = DCLO * DCHI
OUT106 = SV4T
DCLOP
DCHIP
DCLOP
>
DCHIP
Vdc
Summary of Contents for SEL-351A
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