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One voltage input is provided for each phase-earth voltage. The connection of voltage transformers is not re-
quired for the differential protection, but for using the distance protection and other ancillary functions. A further
voltage input (U
nism and voltage check) or any other voltage U
to the IA input amplifier group.
The input amplifier group IA provides high-resistance termination for the input quantities. It contains filters that
are optimized with regard to bandwidth and processing speed.
The AD analog digital converter group contains analog/digital converters and memory chips for data transfer to
the microcomputer system.
Microcomputer system
Apart from processing the measured values, the microcomputer system µC also executes the actual protection
and control functions consisting of:
• Filtering and conditioning of the measured signals
• Continuous monitoring of the measured signals
• Monitoring of the pickup conditions of the individual protection functions
• Formation of the local differential protection values (phasor analysis and charge current computation) and
creation of the transmission protocol
• Decoding of the received transmission protocol, synchronisation of the differential protection values and
summing up of the differential currents and charge currents
• monitoring of the communication with the other devices of the line protection system
• Interrogation of threshold values and time sequences
• Processing of signals for the logic functions
• Decisions for trip and close commands
• Recording messages, fault data and fault values for analysis
• Operating system and related function management such as, e.g., data recording, real-time clock, commu-
nication, interfaces, etc.
The information is provided via output amplifier OA.
Binary Inputs and Outputs
The microcomputer system obtains external information through binary inputs such as remote resetting or
blocking commands for protection functions. The computer system obtains the information from the system (e.g
remote resetting) or the external equipment (e.g. blocking commands). Outputs include, in particular, trip com-
mands to circuit breakers and signals for remote annunciation of important events and conditions.
Front Elements
LEDs and an LC display provide information on the function of the device and indicate events, states and mea-
sured values.
Integrated control and numeric keys in conjunction with the LCD facilitate local communication with the device.
Thus, all information of the device, e.g. configuration and setting parameters, operating and fault messages,
and measured values can be retrieved or changed (see also chapter 2 and SIPROTEC 4 System Description).
Devices with control functions also allow control of switchgear from the front panel.
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
) can optionally be used to measure the displacement voltage, a busbar voltage (for synchro-
4
(for overvoltage protection). The analog values are transferred
X
Introduction
1.1 Overall Operation
23
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