GE Multilin W650 Instruction Manual page 244

5.6 INPUTS/OUTPUTS 5 SETTINGS
f) WITH DOUBLE VOLTAGE SUPERVISION AND SERIAL RESISTOR IN VOLTAGE MONITORS.
Figure 5–31:shows the supervision scheme with an external resistor.
An external series resistor is used with the 52a voltage monitor to prevent CB tripping with a short-circuited voltage monitor.
With CB open, 52/a is open and 52/b is closed. A shorted 52/a voltage monitor will not cause a trip because 52/b voltage
monitor is current limitted to 2mA. With a shorted 52/b voltage monitor, no false trip will be performed because 52/a is in
series limiting current to 2mA.
5
Figure 5–31: SUPERVISION APPLICATION WITH AUXILIARY CONTACTS 52A AND 52B AND SERIES RESISTOR IN
F15-F16
5-104 W650 Wind Generator Protection System GEK-113032A