2 Functions
314
7SD5 Manual
C53000-G1176-C169-1
2.16 Synchronism and Voltage Check (optional)
The synchronism and voltage check function ensures, when switching a line onto a
busbar, that the stability of the network is not endangered. The voltage of the feeder
to be energized is compared to that of the busbar to check conformances in terms of
magnitude, phase angle and frequency within certain tolerances. Optionally, deener-
gization of the feeder can be checked before it is connected to an energized busbar
(or vice versa).
The synchronism check can either be conducted only for automatic reclosure, only for
manual closure (this includes also closing via control command) or in both cases. Dif-
ferent close permission (release) criteria can also be programmed for automatic and
manual closure.
Synchronism check is also possible without external matching transformers if a power
transformer is located between the measuring points.
Closing is released for synchronous or asynchronous system conditions. In the latter
case, the device determines the time for issuing the close command such that the volt-
ages are identical the instant the breaker poles make contact.
2.16.1 Method of Operation
General
The synchronism and voltage check function uses the feeder voltage – designated
with U
Line
– and the bus-bar voltage – designated with U
Bus
– for comparison purposes.
The latter may be any phase-to-earth or phase-to-phase voltage.
Figure 2-130
Synchronism check on closing
If a power transformer is located between the feeder voltage transformers and the bus-
bar voltage transformers (Figure 2-131), its vector group can be compensated for by
the 7SD5 relay, so that no external matching transformers are necessary.
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