Schweitzer Engineering Laboratories SEL-311C - Station DC Battery Monitor; DC Under- and Overvoltage Elements; Create Desired Logic for DC Under- and Overvoltage Alarming; Figure 8.9 DC Under- and Overvoltage Elements

8.15
Date Code 20060320 Instruction Manual SEL-311C Relay
Breaker Monitor and Metering Functions
Station DC Battery Monitor
Station DC Battery Monitor
The station dc battery monitor in the SEL-311C 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 1.2). The station dc
battery monitor settings (DCLOP and DCHIP) are available via the SET G
command (see Table 9.1 and also Global Settings (Serial Port Command SET
G and Front Panel) on page SET.22).
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-311C 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-311C outside of the power supply limits
listed in Specifications on page 1.10.
Figure 8.9 DC Under- and Overvoltage Elements
Logic outputs DCLO and DCHI in Figure 8.9 operate as follows:
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 OUT106 for alarm purposes.
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
≥ pickup setting DCHIP
= 0 (logical 0), if V
dc
< pickup setting DCHIP
DCLO
DCHI
V
dc
Relay
Word
Bits
DCLOP
DCHIP
Settings
Undervoltage
Overvoltage
(From Rear
Panel Terminals
Labeled POWER)