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Functions
2.18 Synchronism and Voltage Check (optional)
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
349
Figure 2-170 Synchronism check across a transformer - example
The synchronism check function in the 7SD5 usually operates in conjunction with the integrated automatic re-
close, manual close, and the control functions of the relay. It is also possible to employ an external automatic
reclosing system. In such a case signal exchange between the devices is accomplished via binary inputs and
outputs (see Figure 2-171).
When closing via the integrated control function, the configured interlocking conditions may have to be verified
before checking the conditions for synchronism. After the synchronism check grants the release, the interlock-
ing conditions are not checked a second time.
Furthermore, switching is possible under synchronous or asynchronous system conditions or both.
Synchronous switching means that the closing command is issued as soon as the following critical values lie
within the set tolerances:
• Voltage magnitude difference
AR maxVolt.Diff (address 3511 ) or MC maxVolt.Diff (address 3531 )
• Angle difference
AR maxAngleDiff
(address
3513
) or
MC maxAngleDiff
(address
3533
)
• Frequency difference AR maxFreq.Diff (address 3512 ) or MC maxFreq.Diff (address 3532 )
For switching under asynchronous system conditions, the device determines the time for issuing the ON
command from the current angle and frequency difference such that the angle difference of the voltages (be-
tween busbar and feeder) is almost 0° at the instant the poles make contact. For this purpose, the device re-
quires the parameter (address
239 T-CB close ) with the set circuit breaker closing time. Different frequency
limit thresholds apply to switching under synchronous and asynchronous conditions. If closing is permitted ex-
clusively under synchronous system conditions, the frequency difference limit for this condition can be set. If
closing is permitted under synchronous as well as under asynchronous system conditions, a frequency differ-
ence below 0.01 Hz is treated as a synchronous condition, a higher frequency difference value can then be set
for closing under asynchronous system conditions.
The synchro check function only operates when it is requested to do so. Various possibilities exist for this pur-
pose:
• Measuring request from the internal automatic reclosure device. If the internal automatic reclosing function
is set accordingly (one or more reclosing attempts set to synchronism check, see also Section 2.17.2), the
measuring request is accomplished internally. The release conditions for automatic reclosing apply (param-
eter AR...).
• Request to execute a check synchronism measurement from an external automatic reclosure device. The
measuring request must be activated via the binary input „>Sync. Start AR“ (no. 2906). The release
conditions for automatic reclosing apply (parameter AR...).