Manual 37352A
MFR 12 Packages - Protection Relay
© Woodward
Page 43/62
Ground-Fault Monitoring, Measured (
Package IvIkR
)
Measured ground fault monitoring with isolated or balanced mains.
The line-to-ground current is usually measured via a cable-type transformer or current transformers in Holm-
green. Ground faults result in comparatively small ground currents at the location of the fault. The measuring in-
put is specially designed for these small ground currents. The measuring input is limited to a maximum of 35mA.
The ground fault current input is thermally designed to withstand the CT secondary rated current. All measure-
ments are galvanically isolated. If a ground fault does occur, the control unit issues an alarm message. This mes-
sage can
be suppressed with the discrete input "Blocking of protective functions / remote acknowledgement".
Earth current
monitoring ON
Ground fault monitoring, measured
ON/OFF
ON
................ Ground fault monitoring (measured) is enabled. The subsequent
screens of this function are displayed.
OFF
.............. Ground fault monitoring (measured) is disabled. The subsequent
screens of this function are not displayed.
Earth current 1
Response = 000%
Threshold ground fault, measured, level 1
0.05 to 3.50 %
Ground fault current (level 1) is defined by this parameter. The percentage config-
ured here refers to the configured rated current (refer to page 30). If this limit is
reached or exceeded, the unit outputs the message "
Earthcur.1
". If a relay was
assigned to this function in the relay manager, that relay will be energized.
Earth current 1
Delay 00.00s
Pickup delay, level 1
0.02 to 99.98 s
In order to initiate a ground fault current (level 1) alarm, the measured ground fault
current must exceed and remain above the configured threshold without interrup-
tion for at least the period of time specified in this screen.
Earth current 2
Response = 000%
Threshold ground fault, measured, level 2
0.05 to 3.50 %
Ground fault current (level 2) is defined by this parameter. The percentage config-
ured here refers to the configured rated current (refer to page 30). If this limit is
reached or exceeded, the unit outputs the message "
Earthcur.2
". If a relay was
assigned to this function in the relay manager, that relay will be energized.
Earth current 2
Delay 00.00s
Pickup delay, level 2
0.02 to 99.98 s
In order to initiate a ground fault current (level 2) alarm, the measured ground fault
current must exceed and remain above the configured threshold without interrup-
tion for at least the period of time specified in this screen.
Earth current
Hysteresis 0.00%
Hysteresis for the ground fault monitoring, measured, levels 1+2
0.00 to 3.50 %
In order to prevent system fluctuations from continually initiating ground fault cur-
rent alarms (levels 1 & 2), a lower release point is defined here. If the control moni-
tors the current above the permissible limit, the current must drop below that
threshold and the current level defined here.
Example: If a 1A CT secondary has a ground fault current limit 1 of 2% (20mA)
and a hysteresis of 1.5% (15mA), the monitored current for a ground fault current
alarm must drop below 15mA to reset the alarm.
