ABB Relion 670 series, Application Manual

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With low resistance faults, the 55 A difference of the approximate method in comparison to
the exact method, is relatively small when considering high fault currents. With high-resistance
faults, the charging current will not change much so it is acceptable to continue subtracting it.
4.8 Configuration of binary signals
4.8.1 Operation principle
M12452-14 v6
In 64 kbit mode, communication takes place in standard ITU (CCITT) PCM digital 64 kbit/s
channels. Communication is two-way, and telegrams are sent every 5 ms (same in 50 Hz and
60 Hz) to exchange information between two IEDs. The format used is C37.94, and one
telegram consists of start and stop flags, address, data to be transmitted, Cyclic Redundancy
Check (CRC) and Yellow bit (which is associated with C37.94).
en01000134.vsd
Start
flag
Information CRC
Stop
flag
8 bits n x 16 bits 8 bits 16 bits
IEC01000134 V1 EN-US
Figure 44: Data message structure
The start and stop flags are composed of 0111 1110 sequence (7E hexadecimal) as defined in
the HDLC standard. CRC is designed according to the standard CRC16 definition. The optional
address field in the HDLC frame is not used but, instead, separate addressing is included in
the data field.
The address field is used for checking that the received message originates from the correct
equipment. There is always a risk that multiplexers occasionally mix up the messages. Each
terminal in the system is given a number. The terminal is then programmed to accept
messages from a specific terminal number. If the CRC function detects a faulty message, the
message is thrown away and not used in the evaluation.
If communication is used for line differential purposes, transmitted data consists of three
currents, clock information, trip, block and alarm signals and eight binary signals which can be
used for any purpose. The three currents are represented as sampled values.
If communication is used exclusively for binary signals, full data capacity of the
communication channel is used for the binary signal purpose which gives the capacity of 192
signals.
In 2 Mbit mode, telegrams are still sent using C37.94 but the HDLC part is not used. Instead, all
12 channels of the C37.94 frame are used, and a telegram is sent whenever a sample is
available. The address field is used in the same way as in 64 kbit mode but the CRC field is 32
bits. It carries 9 analog samples and 192 general purpose binary signals.
GUID-E8E1B062-7E32-4850-A5D1-6EDBC82154D4 v1
IEC10000071 V1 EN-US
Figure 45: Setting example with one communication channel for binary transfer
Section 4 1MRK 505 382-UEN E
Analog and binary signal transfer for line differential protection
44 Communication set-up, 670/650 series
Application Guide
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