Introduction
1.1 Overall Operation
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011
19
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.
The analog-to-digital (AD) element consists of an analog-to-digital (A/D) converter and memory components
for data transmission to the microcomputer system.
Microcomputer System
Apart from processing the measured values, the microcomputer system µC also executes the actual protection
and control functions. They especially consist of:
• Filtering and preparation of the measured quantities
• Continuous monitoring of the measured quantities
• Monitoring of the pickup conditions for the individual protection functions
• Interrogation of limit values and time sequences
• Control of signals for the logic functions
• Decision on trip and close commands
• Recording of messages, fault data and fault values for analysis
• Administration of the operating system and its functions, e.g. data storage, realtime clock, communication,
interfaces, etc.
• Formation of the local differential protection values (phasor analysis and charge current computation) and
creation of the transmission protocol
• Decoding the received transmission protocol, synchronization of differential protection values and totaling
the differential currents and charge currents
• Monitoring the communication with the device of the remote end
The information is provided via output amplifier OA.
Binary Inputs and Outputs
Binary inputs and outputs to and from the computer system are relayed via the input/output modules. The com-
puter system obtains information from the system (e.g. remote resetting) or from other devices (e.g. blocking
commands). Outputs are, in particular, commands to the switchgear units and annunciations for remote signal-
ing of important events and statuses.
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