Siemens SIPROTEC 4 7SD80, Manual

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Overall Operation
The digital SIPROTEC 7SD80 overcurrent protection is equipped with a powerful microprocessor. It allows all
tasks to be processed digitally, from the acquisition of measured quantities to sending commands to circuit
breakers.
Figure 1-1 shows the basic structure of the 7SD80 device.
Analog Inputs
The measuring inputs (MI) convert the currents and voltages coming from the instrument transformers and
adapt them to the level appropriate for the internal processing of the device. The device provides 4 current
transformers and - depending on the model - additionally 3 voltage transformers. Three current inputs serve
for the input of the phase currents, another current input (
Ι
N
) may be used for measuring the ground fault
current
Ι
N
(current transformer starpoint) or for a separate ground current transformer (for sensitive ground
fault detection
Ι
Ns
and directional determination of ground faults) - depending on the model.
[hw-struktur-7sd80-100801, 1, en_US]
Figure 1-1 Hardware structure of the 7SD80 differential protection
There is one voltage input available for each phase-to-ground voltage. The differential protection does not
need measuring voltages due to its functional principle. Directional overcurrent protection, however, requires
the phase-to-ground voltage V
A
, V
B
and V
C
to be connected. Additionally, voltages can be connected that allow
displaying voltages and power values and also measuring the line voltage for automatic reclosing. The analog
quantities are forwarded to the input amplifier group (IA).
The input amplifier group IA provides high-resistance termination for the analog input quantities. It consists of
filters that are optimized for measured value processing with regard to bandwidth and processing speed.
1.1
Introduction
1.1 Overall Operation
20 SIPROTEC 4, 7SD80, Manual
E50417-G1100-C474-A2, Edition 02.2018