Siemens Siprotec 7VK61 Manual page 82

Functions
2.4 Synchronism and voltage check (optional)
Figure 2-17
The synchronism check function in the 7VK61 usually operates in conjunction with the integrated automatic
reclose, 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 2-18).
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 with synchronous or asynchronous system conditions or both. Synchronous
switching means that the closing command is issued as soon as the criticial values (voltage magnitude differ-
ence AR maxVolt.Diff (address 3511) or MC maxVolt.Diff (address 3531), angle difference AR
maxAngleDiff (address 3513) or MC maxAngleDiff (address 3533) and frequency difference AR
maxFreq.Diff (address 3512) or MC maxFreq.Diff (address 3532) lie within the set tolerances. For
switching under asynchronous system conditions, the device calculates the correct time of the closing
command from the angle difference AR maxAngleDiff (address 3513) or MC maxAngleDiff (address
3533) and the frequency difference AR maxFreq.Diff(address 3512) or MC maxFreq.Diff (address
3532) so that the angle difference of the voltages (between busbar and feeder) is nearly 0° the instant the
circuit breaker primary contacts make contact. For this purpose, the device must be informed of the operating
time of the circuit breaker for closing. Different frequency limit thresholds apply to switching under synchronism
and asynchronous conditions. If closing is permitted exclusively under synchronous system conditions, the fre-
quency difference limit for this condition can be set. If closing is permitted under synchronous as well as under
asynchronous system conditions, a frequency difference 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.
Additional functions are described in the section with the margin heading „Operating Modes".
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 2.2.2), 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...).
82
Synchronism check across a transformer - example
SIPROTEC, 7VK61, Manual
C53000-G1176-C159-3, Release date 05.2009