Schweitzer Engineering Laboratories SEL-751 - Figure 5.17 DC Under- and Overvoltage Elements

5.16
SEL-751 Relay Instruction Manual Date Code 20170927
Metering and Monitoring
Station DC Battery Monitor
Figure 5.17 DC Under- and Overvoltage Elements
Logic outputs DCLO and DCHI in Figure 5.17 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 5.18 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 SVnT and then
routed to output contact OUTxxx for alarm purposes.
Figure 5.18 Create DC Voltage Elements With SELOGIC Control Equations
DCLO < DCHI (Top of Figure 5.18)
Output contact OUTxxx asserts when:
Vdc  DCLOP or Vdc  DCHIP
DCLO = 1 (logical 1), if Vdc  pickup setting DCLOP
= 0 (logical 0), if Vdc > pickup setting DCLOP
DCHI = 1 (logical 1), if Vdc  pickup setting DCHIP
= 0 (logical 0), if Vdc < pickup setting DCHIP
DCLO
DCHI
Vdc
Relay
Word
Bits
DCLOP
DCHIP
Settings
Undervoltage
Overvoltage
(From Rear- Panel
Terminals Labeled
VBAT+ and VBAT—)
SVnPU
SVnDO
SVn
SVnT
SVnT
DCHI
SVn = DCLO + DCHI
OUTxxx = SVnT
DCLO
DCLOP
DCHIP
DCLOP < DCHIP
V
dc
SVnPU
SVnDO
SVn
DCLO * DCHI
SVn = DCLO * DCHI
OUTxxx = SVnT
DCLOP
DCHIP
DCLOP > DCHIP
V
dc