•
Live line and live bus.
•
Voltage level difference.
•
Frequency difference (slip). The bus and line frequency must also be within a
range of ±10% deviated from rated frequency.
•
Phase angle difference.
A time delay is available to ensure that the conditions are fulfilled for a minimum
period of time.
In stable power systems, the frequency difference is insignificant or zero for
manually initiated closing or closing by automatic restoration. In steady conditions,
a bigger phase angle difference can be allowed as this is sometimes the case in a
long and loaded parallel power line. For this application we accept a synchrocheck
with a long operation time and high sensitivity regarding the frequency difference.
The phase angle difference setting can be set for steady state conditions.
Another example is the operation of a power network that is disturbed due to a
fault event: After the fault clearance a highspeed auto-reclosing takes place. This
can cause a power swing in the network and the phase angle difference may begin
to oscillate. Generally, the frequency difference is the time derivative of the phase
angle difference and typically oscillates between positive and negative values.
When the circuit breaker needs to be closed by auto-reclosing after fault-clearance
some frequency difference should be tolerated. But if a big and increasing phase
angle difference is allowed at the same time, there is some risk in auto-reclosing. In
this case it is safer to close when the phase angle difference is smaller.
To fulfill the requirements above, the synchrocheck function is provided with
separate settings for steady (Manual) conditions and operation under disturbed
conditions (Auto).
SynchroCheck
UHighBusSC > 10 - 120 % of GblBaseSelBus
UHighLineSC > 10 - 120 % of GblBaseSelLine
UDiffSC < 0.02
– 0.50 p.u.
PhaseDiffM < 5 - 90 degrees
PhaseDiffA < 5 - 90 degrees
FreqDiffM < 3 - 1000 mHz
FreqDiffA < 3 - 1000 mHz
Fuse fail
Fuse fail
Line voltage
Line
reference
voltage
Bus voltage
IEC16000122-1-en.vsdx
IEC16000122 V1 EN-US
Figure 66:
Principle for the synchrocheck function
Section 12
1MRK 506 375-UEN A
Control
214
Railway application RER670 2.2 IEC
Application manual
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