Operation Principle - ABB RES670 Technical Manual

Section 20
Remote communication
20.1.6
738
Table 571: LDCMRecBinS3_2M Monitored data
Name Type
CommStatus BOOLEAN

Operation principle

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).
Start
Information
flag
8 bits n x 16 bits
IEC01000134 V1 EN-US
Figure 284: 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.
Values (Range) Unit
0=Ok -
1=SyncErr
2=No RXD
3=LocalGPSErr
4=RemGPSErr
5=LocAndRemG
PSErr
6=LocalADErr
7=RemADErr
8=LocAndRemA
DErr
9=AddressErr
10=FreqConfErr
11=LatencyConf
Err
Stop
CRC
flag
16 bits 8 bits
en01000134.vsd
Phasor measurement unit RES670 2.2 ANSI
1MRK 511 408-UUS A
PID-6475-MONITOREDDATA v2
Description
Status of communication link
M12452-14 v5
Technical manual