Functions
6-1977SA6 Manual
C53000-G1176-C133-1
6.13 Synchronism and Voltage Check (Dead-line / Dead-bus check)
6.13.1 Method of Operation
General The synchronism and voltage check function ensures, when switching a line onto a
bus-bar, that the stability of the network is not endangered. The function can be
programmed to perform the synchronism and voltage check for automatic reclosure
only, for manual closure only, or for both cases. Different close permission (release)
criteria can also be programmed for automatic and manual closure.
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 convenient phase-to-earth or phase-to-phase voltage
derived from the bus-bar voltage transformers.
Figure 6-103 Synchronism check on closing
If a power transformer is situated between the feeder voltage transformers and the
bus-bar voltage transformers (Figure 6-104), its vector group can be compensated for
by the 7SA6 relay, so that no external matching transformers are necessary.
The synchronism check function in the 7SA6 usually operates in conjunction with the
integrated automatic reclose and manual close functions of the relay. It is however
also possible to co-ordinate with an external automatic reclosure relay. In this case,
the information exchange between the devices must be performed through binary
inputs and outputs. If further control functions are to operate with synchronism or
voltage check, these must be combined with the manual close function, either through
the binary inputs and outputs, or by means of the integrated user definable logic
functions (CFC).
7SA6
TRIP
CLOSE
U
line
U
bus
L+
I
Sync
Busbar
Feeder
Protection
AR
Discrepancy
switch
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