Siemens SIPROTEC 4 7UT6 Series Manual page 17

currents. One or two additional inputs can be designed for highly sensitive current detection. thus allowing,
for example, the detection of small tank leakage currents of power transformers or reactors, or — with an
external series resistor — processing of a voltage (e.g. for high-impedance unit protection).
The versions 7UT613 and 7UT633 are available with 4 voltage inputs. 3 of these inputs can be connected to
the phase-to-earth voltages. Another voltage input can be used for a single-phase voltage, such as a displace-
ment voltage or any other voltage. In principle, the differential protection is designed such that it can operate
without measured voltages. However, the integrated voltage protection functions use the measuring voltage
inputs, as for example the overexcitation protection, to calculate the induction in transformers or shunt reac-
tors. In addition, the measuring voltages and the quantities derived from them (induction, power, power
factor) can be displayed, annunciated and/or monitored by the device if the voltages are connected.
The analogue signals are then routed to the input amplifier group IA.
The input amplifier group IA provides high-resistance termination for the analogue input quantities and
contains filters that are optimised for measured value processing with regard to bandwidth and processing
speed.
The analogue-to-digital (AD) stage consists of a multiplexor, an analogue-to-digital (A/D) converter and
memory components for the transmission of digital signals to the microcomputer system.
Microcomputer system
In addition to the control of the measured values, the actual protection and control functions are processed in
the μC microcomputer system. In particular, the following is included:
•
filtering and conditioning of measured signals
•
continuous monitoring of measured signals
•
monitoring of the pickup conditions of the individual protective functions
•
Conditioning of the measured signals: i.e. conversion of currents according to the connection group of
the protected transformer (when used for transformer differential protection) and matching of the
current amplitudes
•
formation of the differential and restraint quantities
•
Frequency analysis of the phase currents and restraint quantities
•
calculation of the RMS values of the currents for overload detection and adjustment of the temperature
rise of the protected object
•
retrieval of threshold values and time sequences
•
processing of signals for the logic functions
•
processing User-defined Logic Functions
•
reaching trip command decisions
•
check of control commands and output to switching devices
•
storage of indications, fault data and fault values for fault analysis purposes
•
calculation and display/annunciation of measured values and the quantities derived from them
•
management of the operating system and its functions, e.g. data storage, real-time clock, communica-
tion, interfaces, etc.
The information is provided via output amplifier OA.
Binary Inputs and Outputs
Binary inputs and outputs from and to the computer system are routed via the I/O modules (inputs and
outputs). The computer system obtains the information from the system (e.g remote resetting) or from other
devices (e.g. blocking commands). These outputs include, in particular, trip commands to switchgear and
signals for remote annunciation of important events and conditions.
SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016
Introduction
1.1 Overall Operation
17