Operation Manual 37107F
MFR 3 - Multi Function Relay
© Woodward
Page 111/165
Mains Frequency Monitoring
NOTE
The "Blocking of mains protection" input (terminal 61) disables mains monitoring and decoupling.
Monitoring of the mains frequency is absolutely vital if a generator is to be operated in parallel with a public util-
ity. In the event of a mains failure (e. g. short interruption) the generator which is in mains parallel operation,
must be automatically disconnected from the mains.
Function: "
Mains frequency not within the permissible range"
The mains frequency is outside of the limit values configured for overfrequency or underfrequency. The power
circuit breaker, which is configured to carry out decoupling from the mains, is immediately opened. The prere-
quisite of mains frequency monitoring is a mains parallel operation (both GCB and MCB are closed). An alarm is
issued if a fault condition is detected.
Parameter
173
Mains frequency
monitoring ON
Mains frequency
ON/OFF
ON
................ Mains frequency monitoring is enabled. The subsequent screens of
this function are displayed.
OFF
.............. Mains frequency monitoring is not performed. The subsequent
screens of this function are not displayed.
Parameter
174
Mains overfreq.
f > 00.00Hz
Mains overfrequency: limit
40.00 to 70.00 Hz
The value for the mains overfrequency limit is configured in this screen. If the mo-
nitored frequency reaches or exceeds this level for the configured delay time, the
unit issues an alarm and opens either the GCB or the MCB depending on which is
configured for decoupling from the mains.
Tripping of class F0 alarm
Parameter
175
ains overfreq.
Delay 00.00s
Mains overfrequency: delay
0.02 to 99.98 s
The mains overfrequency monitoring threshold limit must be exceeded, without in-
terruption, for the time period configured here before the configured relay will be
energized.
Parameter
176
ains underfreq.
f < 00.00Hz
Mains underfrequency: limit
40.00 to 70.00 Hz
The value for the mains underfrequency limit is configured in this screen. If the
monitored frequency reaches or falls below this level for the configured delay time,
the unit issues an alarm and opens either the GCB or the MCB depending on which
is configured for decoupling from the mains.
Tripping of class F0 alarm
Parameter
177
Mains underfreq.
Delay 00.00s
Mains underfrequency: delay
0.02 to 99.98 s
The mains underfrequency monitoring threshold limit must be exceeded, without
interruption, for the time period configured here before the configured relay will be
energized.
