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Operation Manual 37107F
MFR 3 - Multi Function Relay
Page 114/165
© Woodward
Mains d
ϕ
/dt Phase/Vector Shift Monitoring
NOTE
The "Blocking of mains protection" input (terminal 61) disables mains monitoring and decoupling.
A d
ϕ
/dt phase/vector jump is a sudden change in the voltage vector angle, and may be caused by a major genera-
tor load change. In this case, the measuring circuit detects a change in the cycle duration once. This change in the
vector angle is compared with a calculated mean value from previous measurements. Monitoring encompasses all
three phases. The threshold value in degrees specifies the difference in time between the mean and the current
value in reference to a full cycle. Monitoring can be set in various manners. The d
ϕ
/dt phase/vector shift moni-
toring may be used as an additional method for decoupling from the mains. The minimum voltage at which the
phase shift monitoring is enabled is 70 % of the rated PT secondary voltage input.
Function:
"Voltage cycle duration not within the permissible range"
The voltage vector exceeds the configured limit value for the phase/vector shift. The breaker configured for
mains decoupling is opened. The requirement therefore is a mains parallel operation (both GCB and MCB are
closed). An alarm is issued if a fault condition is detected.
Parameter
186
Phase shift
monitoring ON
d
ϕ
/dt phase/vector shift
ON/OFF
ON
................ Mains voltage phase shift monitoring is enabled. The subsequent
screens of this function are displayed.
OFF
.............. Mains voltage phase shift monitoring is not performed. The subse-
quent screens of this function are not displayed.
Parameter
187
Monitoring
----------------
d
ϕ
/dt phase/vector shift: type
one/three-phase / three phase only
one/three-phase:
During single-phase voltage phase shift monitoring, tripping oc-
curs if the phase shift exceeds the configured threshold value in any
one of the three phases. This type of monitoring is very sensitive, and
may lead to nuisance tripping if the configured phase angle settings
are too small.
three phase only:
During three-phase voltage phase shift monitoring, tripping oc-
curs only if the phase shift exceeds the configured threshold value in
all three phases within 2 cycles.
Tripping of class F0 alarm