1 Introduction
20
7SD5 Manual
C53000-G1176-C169-1
1.1
Overall Operation
The SIPROTEC
®
line protection 7SD5 is equipped with a powerful microcomputer
system. This provides fully numerical processing of all functions in the device, from the
acquisition of the measured values up to the output of commands to the circuit break-
ers, as well as the exchange of measured data with the other ends of the protected
area. Figure 1-1 shows the basic structure of the device.
Analog Inputs
The measuring inputs (MI) convert the currents and voltages coming from the instru-
ment transformers and adapt them to the level appropriate for the internal processing
of the device. The device has 4 current and 4 voltage inputs. Three current inputs are
provided for measurement of the phase currents, a further measuring input (
I
4
) may
be configured to measure the earth current (residual current from the current trans-
former star-point or separate earth current transformer), the earth current of a parallel
line (for parallel line compensation) or the star-point current of a power transformer (for
earth fault direction determination).
Figure 1-1
Hardware structure of the line differential protection 7SD5
A voltage input is provided for each phase-earth voltage. The connection of voltage
transformers is not required for differential protection, but for using distance protection
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