Sel 411L - Table 9.9 Example DC Battery Monitor Settings-125 VDC for Vdc1 and 48 VDC for Vdc2

P.9.22
SEL-411L Relay Protection Manual Date Code 20151029
Monitoring and Metering
Station DC Battery System Monitor
Use the expected battery voltages of Table 9.9 to determine the relay station
dc battery monitor threshold settings. Table 9.9 shows these threshold settings
for a nominal 125-Vdc battery system (the Vdc1 input) and a nominal 48-Vdc
battery system (the Vdc2 input).
AC Ripple
Another method for determining whether the substation battery charger has
failed is to monitor the amount of ac ripple on the station dc battery system.
The IEEE C37.90-1989 standard also identifies an “Allowable AC Component
in DC Control Voltage Supply” (Section 6.5) as an alternating component
(ripple) of 5 percent peak or less. (This definition is valid if the minimum
instantaneous voltage is not less than 80 percent of the rated voltage.) The
relay measures ac ripple as a peak-to-peak waveform, consequently, DC1RP
and DC2RP should be set at or greater than 10 percent (2 • 5% peak) of the
equalizing voltage. Table 9.10 shows the ac ripple threshold settings for this
example.
Float Low 60 (cells) • 2.15 (volts/cell) 129.0
Float High 60 (cells) • 2.23 (volts/cell) 133.8
Equalize Mode 60 (cells) • 2.33 (volts/cell) 139.8
Trip/Close 80% • 48 Vdc 38.4
Open Circuit 24 (cells) • 2.06 (volts/cell) 49.4
Float Low 24 (cells) • 2.15 (volts/cell) 51.6
Float High 24 (cells) • 2.23 (volts/cell) 53.5
Equalize Mode 24 (cells) • 2.33 (volts/cell) 55.9
Trip/Close 80% • 24 Vdc 19.2
Open Circuit 12 (cells) • 2.06 (volts/cell) 24.7
Float Low 12 (cells) • 2.15 (volts/cell) 25.8
Float High 12 (cells) • 2.23 (volts/cell) 26.8
Equalize Mode 12 (cells) • 2.33 (volts/cell) 28.0
Table 9.9 Example DC Battery Monitor Settings—125 Vdc for Vdc1 and
48 Vdc for Vdc2
Setting Description Indication Value (Vdc)
DC1LFP Low-fail threshold, Mon. 1 Poor battery performance 100
DC1LWP Low-warning threshold, Mon. 1 Charger malfunction 127
DC1HWP High-warning threshold, Mon. 1 Equalization 137
DC1HFP High-fail threshold, Mon. 1 Charger malfunction 142
DC2LFP Low-fail threshold, Mon. 2 Poor battery performance 38
DC2LWP Low-warning threshold, Mon. 2 Charger malfunction 50
DC2HWP High-warning threshold, Mon. 2 Equalization 55
DC2HFP High-fail threshold, Mon. 2 Charger malfunction 57
Table 9.8 Example DC Battery Voltage Conditions (Sheet 2 of 2)
Condition Calculation Battery Voltage (Vdc)