Date Code 20010625
Breaker Monitor and Metering Functions
8-15
SEL-311L Instruction Manual
S
TATION
DC B
ATTERY
M
ONITOR
The station dc battery monitor in the SEL-311L Relay can alarm for under- or overvoltage dc
battery conditions and give a view of how much the station dc battery voltage dips when
tripping, closing, and other dc control functions take place. The monitor measures the station dc
battery voltage applied to the rear-panel terminals labeled Z25 and Z26 (see Figure 1.4). The
station dc battery monitor settings (DCLOP and DCHIP) are available via the
SET G
command
(see Table 9.1 in
Section 9: Setting the Relay
and also Settings Sheet 6 in the back of
Section
9
).
DC Under- and Overvoltage Elements
Refer to Figure 8.9. The station dc battery monitor compares the measured station battery
voltage (Vdc) to the undervoltage (low) and overvoltage (high) pickups DCLOP and DCHIP.
The setting range for pickup settings DCLOP and DCHIP is:
OFF, 20 to 300 Vdc, .01 Vdc increments
This range allows the SEL-311L Relay to monitor nominal battery voltages of 24, 48, 110, 125,
and 250 V. When testing the pickup settings DCLOP and DCHIP, do not operate the SEL-311L
Relay outside of the power supply limits listed in
Section1: Introduction and Specifications
.
Figure 8.9: DC Under- and Overvoltage Elements
Logic outputs DCLO and DCHI in Figure 8.9 operate as follows:
DCLO
= 1 (logical 1), if V
dc
b
pickup setting DCLOP
= 0 (logical 0), if V
dc
> pickup setting DCLOP
DCHI
= 1 (logical 1), if V
dc
r
pickup setting DCHIP
= 0 (logical 0), if V
dc
< pickup setting DCHIP
Create Desired Logic for DC Under- and Overvoltage Alarming
Pickup settings DCLOP and DCHIP are set independently. Thus, they can be set:
DCLOP < DCHIP
or
DCLOP > DCHIP
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