Introduction
1.1 Overall Operation
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
20
1.1
Overall Operation
The digital SIPROTEC 7SJ62/64 multifunction protection devices are equipped with a powerful microproces-
sor. It allows all tasks to be processed digitally, from the acquisition of measured quantities to sending com-
mands to circuit breakers. Figures 1-1 and 1-2 illustrate the basic structure of the 7SJ62 and 7SJ64 and the
following paragraphs describe each major element.
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 four current
inputs. Depending on the model, the device is also equipped with three or four voltage inputs. Three current
inputs serve for input of the phase currents. Depending on the model, the fourth current input (
I
N
) may be used
for measuring the ground fault current
I
N
(current transformer starpoint) or for a separate ground current trans-
former (for sensitive ground fault detection
I
Ns
and directional determination of ground faults).
Figure 1-1
Hardware structure of the numerical multi-functional device 7SJ621/622
Voltage inputs can either be used to measure the three phase-to-ground voltages, or two phase-to-phase volt-
ages and the displacement voltage (V
N
voltage). It is also possible to connect two phase-to-phase voltages in
open-delta connection.
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