Introduction
1.1 Overall Operation
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
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1.1 Overall Operation
The SIPROTEC 4 7SD5 line protection is equipped with a powerful microprocessor system. This provides fully
digital processing of all functions in the device, from the acquisition of the measured values to the output of
commands to the circuit breakers, as well as the exchange of measured data with the other ends of the pro-
tected area. Figure 1-1 shows the basic structure of the device.
Analog inputs
The measuring inputs (MI) transform the currents and voltages from the instrument transformers and match
them to the internal signal levels for processing in the device. The device has 4 current and 4 voltage inputs.
Three current inputs are provided for the input of the phase currents, a further input (I
4
) can be used to measure
the earth current (current transformer starpoint or separate earth current transformer), the earth current of a
parallel line (for parallel line compensation) or the starpoint current of a source transformer (for earth fault di-
rection determination, restricted earth fault protection).
Figure 1-1 Hardware structure of the line differential protection 7SD5
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