Siemens SIPROTEC 7SJ61, Руководство пользователя, Страница: 18 / 454

Introduction
1.1 Overall Operation
SIPROTEC, 7SJ61, Manual
C53000-G1140-C210-1, Release date 02.2008
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1.1 Overall Operation
The numerical, multi-functional protection device SIPROTEC 7SJ61 is 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. Figure 1-1 shows the basic structure of the device.
Analog Inputs
The measuring inputs (MI) convert the currents coming from the instrument transformers and adapt them to the
level appropriate for the internal processing of the device. The device has 4 current inputs. three of these are
for the input of the phase currents. Depending on the model, the fourth current input (
I
N
) may be used for mea-
suring the ground fault current I
N
(current transformer starpoint) or for a separate ground current transformer
(for ground fault detection I
Ns
). The analog input quantities are passed on to the input amplifiers (IA).
Figure 1-1 Hardware structure of the numerical multi-functional device 7SJ61
The input amplifier IA stage provides a high-resistance termination for the input quantities. It consists of filters
that are optimized for measured-value processing with regard to bandwidth and processing speed.
The analog-to-digital (AD) element consists of a multiplexor, an analog-to-digital (A/D) converter and of
memory components for the transmission of digital signals to the microcomputer system.