Method of operation
7SV512
V1
24
C53000---G1176---C91
processing speed to suit the measured value pro-
cessing. The matched analog values are then
passed to the analog input section AE.
The analog input section AE contains input amplifi-
ers, sample and hold elements for each input, ana-
log---to---digital converters and memory circuits for
the data transfer to the microprocessor.
Apart from control and supervision of the measured
values, the microprocessor processes the actual
protective functions. These include in particular:
--- filtering and formation of the measured quantities,
--- continuous interrogation of the binary input which
are used for initiation,
--- continuous calculation of the currents,
--- plausibility checks on the measured currents and
the starting conditions,
--- scanning of limit values and time sequences,
--- decision on trip commands,
--- Storage of instantaneous current and voltage val-
ues during a fault for analysis.
Binary inputs and outputs to and from the processor
are channelled via the input/output elements. From
these the processor receives information from the
switch-gear (e.g. remote resetting) or from other
equipment (e.g. blocking signals). Outputs include,
in particular, trip commands to the circuit breakers,
signals for remote signalling of important events and
conditions as well as visual indicators (LEDs) and an
alphanumerical display on the front.
An integrated membrane keyboard in connection
with a built-in alphanumerical LCD display enables
communication with the unit. All operational data
such as setting values, plant data, etc. are entered
into the protection from this panel (refer Section 6.3).
Using this panel the parameters can be recalled and
the relevant data for the evaluation of a fault can be
read out after a fault has occurred (refer Section 6.4).
The dialog with the relay can be carried out alterna-
tively via the serial interface on the front plate by
means of an operator panel or a personal computer.
Via a second serial interface (option), fault data can
be transmitted to a central evaluation unit. During
healthy operation, measured values (e.g. load cur-
rents) can also be transmitted. This second interface
is designed for connection of optical fibre links, pro-
vided this interface is accordingly ordered (refer
Section 2.3 Ordering data).
A power supply unit provides the auxiliary supply on
the various voltage levels to the described functional
units. +18 V is used for the relay output circuits. The
analog input circuits require ±15 V whereas the pro-
cessor and its immediate peripherals are supplied
with +5 V. Transient failures in the supply voltage, up
to 50 ms, which may occur during short-circuits in
the dc supply system of the plant are bridged by a dc
voltage storage element (rated auxiliary voltage
>110 Vdc).
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