Date Code 20001006
Breaker Monitor, Metering, and Load Profile Functions
8-15
SEL-351 Instruction Manual
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:
20 to 300 Vdc, 1 Vdc increments
This range allows the SEL-351 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-351 Relay
outside of its power supply limits. The relay is shipped with either a 24/48 V supply with
operating range of 20 to 60 Vdc or a 125/250 V supply with operating range of 85 to 350 Vdc.
The power supply rating is located on the serial number sticker on the relay rear panel.
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
£
pickup setting DCLOP
= 0 (logical 0), if V
dc
>
pickup setting DCLOP
DCHI
= 1 (logical 1), if V
dc
³
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
Figure 8.10 shows the resultant dc voltage elements that can be created with SEL
OGIC
Control
Equations for these two setting cases. In these two examples, the resultant dc voltage elements are
time-qualified by timer SV4T and then routed to output contact OUT9 for alarm purposes.
Summary of Contents for SEL-351
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