Functions
6-1817SA522 Manual
C53000-G1176-C119-2
6.12 Synchronism and Voltage Check (Dead-line / Dead-bus check)
6.12.1 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 pro-
grammed 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 pur-
poses. The latter may be any convenient phase-to-earth or phase-to-phase voltage
derived from the bus-bar voltage transformers.
Figure 6-92 Synchronism check on closing
If a power transformer is situated between the feeder voltage transformers and the
bus-bar voltage transformers (Figure 6-93), its vector group can be compensated for
by the 7SA522 relay, so that no external matching transformers are necessary.
The synchronism check function in the 7SA522 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 in-
puts and outputs. If further control functions are to operate with synchronism or volt-
age 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).
7SA522
TRIP
CLOSE
U
line
U
bus
L+
I
Sync
Bus-bar
Feeder
Protection
AR
Discrepancy
switch
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