Siemens 7SK80 - Overall Operation

Introduction
1.1 Overall Operation
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A5, Release date 11.2012
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1.1 Overall Operation
The digital SIPROTEC 7SK80 motor 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 7SK80.
Analog Inputs
The measuring inputs (MI) convert the currents and voltages coming from the measuring 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 (I
N
) may be used for measuring the ground fault current
I
N
(current transformer neutral point) or for a separate ground current transformer (for sensitive ground fault
detection I
Ns
and directional determination of ground faults ) - depending on the model.
Figure 1-1 Hardware structure of the digital 7SK80 motor protection device
The optional voltage transformers can either be used to input 3 phase-to-Ground voltages or 2 phase-to-phase
voltages and the displacement voltage (open delta voltage) or any other voltages. It is also possible to connect
two phase-to-phase voltages in open delta connection.