• The voltages V-Line and V-Bus are higher than the set values for VHighBusSynch
and VHighLineSynch of the respective base voltages GblBaseSelBus and
GblBaseSelLine.
• The dif
ference in the voltage is smaller than the set value of VDiffSynch.
• The difference in frequency is less than the set value of FreqDiffMax and larger
than the set value of FreqDiffMin. If the frequency is less than FreqDiffMin the
synchronism check is used and the value of FreqDiffMin must thus be identical to
the value FreqDiffM resp FreqDiffA for synchronism check function. The bus and
line frequencies must also be within a range of ±5 Hz from the rated frequency.
When the synchronizing option is included also for autoreclose there is no reason
to have different frequency setting for the manual and automatic reclosing and the
frequency difference values for synchronism check should be kept low.
• The frequency rate of change is less than set value for both V-Bus and V-Line.
• The difference in the phase angle is smaller than the set value of CloseAngleMax.
• The closing angle is decided by the calculation of slip frequency and required pre-
closing time.
The synchronizing function compensates for the measured slip frequency as well as the
circuit breaker closing delay. The phase angle advance is calculated continuously. The
calculation of the operation pulse sent in advance is using the measured SlipFrequency
and the set tBreaker time. To prevent incorrect closing pulses, a maximum closing
angle between bus and line is set with CloseAngleMax. Table
52 below shows the
maximum settable value for tBreaker
when CloseAngleMax is set to 15 or 30 degrees,
at different allowed slip frequencies for synchronizing. To minimize the moment stress
when synchronizing near a power station, a narrower limit for the CloseAngleMax
needs to be used.
Table 52: Dependencies between tBreaker and SlipFrequency with different CloseAngleMax
values
tBreaker
[s] (max settable value)
with
CloseAngleMax
= 15 degrees
[default value]
tBreaker
[s] (max settable value) with
CloseAngleMax
= 30 degrees [max
value]
SlipFrequency [Hz]
(BusFrequency -
LineFrequency)
0.040 0.080 1.000
0.050 0.100 0.800
0.080 0.160 0.500
0.200 0.400 0.200
0.400 0.810 0.100
1.000 0.080
0.800 0.050
1.000 0.040
Section 15 1MRK 504 163-UUS A
Control
678 Transformer protection RET670 2.2 ANSI
Application manual
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