Manual 37143A
MFR 15 - Protection Relay & Control
Page 66/119
© Woodward
Overfrequency Monitoring (
Option U
)
The frequency monitoring is performed on two levels. The frequency measuring is monitored three-phase if all
voltages are greater than 15 % of the rated value (100 V or 400 V). This ensures quick and precise measurement
of the frequency. The frequency is still monitored correctly even if voltage is only applied to one phase.
Function
"Frequency not within permissible limits"
The monitored frequency is not within the configured permissible limits for overfrequency. The alarm message
"
Overfreq.1
" or "
Overfreq.2
" will be displayed. This message
cannot
be suppressed with the discrete in-
put "Blocking of protective functions / remote acknowledgement".
Overfrequency-
Monitoring ON
Overfrequency Monitoring
ON/OFF
ON
................Overfrequency monitoring is enabled. The subsequent screens of this
function are indicated.
OFF
..............Overfrequency monitoring is disabled. The subsequent screens of
this function are not displayed.
Overfrequency 1
f > 00.00Hz
Threshold overfrequency, level 1
40.00 to 80.00 Hz
Overfrequency (level 1) is defined by this parameter. If this limit is reached or ex-
ceeded, the unit outputs the message "
Overfreq.1
". If a relay was assigned to
this function in the relay manager, that relay will be energized.
Overfrequency 1
Delay 00.00s
Pickup delay, level 1
0.02 to 99.98 s
In order to initiate an overfrequency (level 1) alarm, the measured frequency must
exceed and remain above the configured threshold without interruption for at least
the period of time specified in this screen.
Overfrequency 2
f > 00.00Hz
Threshold overfrequency, level 2
40.00 to 80.00 Hz
Overfrequency (level 2) is defined by this parameter. If this limit is reached or ex-
ceeded, the unit outputs the message "
Overfreq.2
". If a relay was assigned to
this function in the relay manager, that relay will be energized.
Overfrequency 2
Delay 00.00s
Pickup delay, level 2
0.02 to 99.98 s
In order to initiate an overfrequency (level 2) alarm, the measured frequency must
exceed and remain above the configured threshold without interruption for at least
the period of time specified in this screen.
Overfrequency
Hysteres. 0.00Hz
Hysteresis for the overfrequency monitoring, levels 1+2
0.01 to 9.99 Hz
In order to prevent system fluctuations from continually initiating overfrequency
alarms (both levels), a lower release point is defined here. If the control monitors
the frequency above the permissible limit, the frequency must drop below that
threshold and the frequency level defined here for the fault condition to be recog-
nized as no longer existing.
Example: If a 60 Hz system has an overfrequency limit of 70 Hz and a hysteresis of
5 Hz, the monitored frequency for an overfrequency alarm must fall below 65 Hz
to reset the alarm.
