CHAPTER 2: RS485 INTERFACE IEC 60870-5-103 SERIAL COMMUNICATION
SR3 SERIES PROTECTIVE RELAY PLATFORM – COMMUNICATIONS GUIDE 2-21
Miscellaneous
Application level
Application functions The unbalanced transmission mode of the protocol is used to avoid the possibility of more
than one protection device attempting to transmit on the channel at the same time, over
the RS485 port.
Data is transferred to the primary or control station (master) using the “data acquisition by
polling” principle. Cyclically, the master will request class 2 data to the secondary station
(slave).
When slave has class 1 data (high priority) pending, the ACD control bit will be set to 1
demanding the master to request for that data.
Periodically, the master may send a General Interrogation in order to update the complete
database.
The measurands will be sent to the primary station as a response to class 2 request. A
setting (0 to 60 min) is available to configure the desired interval, where 0 means
transmission as fast as possible.
The following functions are supported:
• Initialization
• General Interrogation
• Synchronization
• Commands transmission
Type identification The Type Identification implemented will be:
TYPE IDENTIFICATION UI8[1..8] <1..255>
<1..31>:= definitions of this companion standard(compatible range)
<32..255>:= for special use (private range)
Information in monitor direction:
<1>:= time-tagged message
<3>:= measurands I
<5>:= identification
<6>:= time synchronization
<8>:= general interrogation termination
<9>:= measurands II
Information in control direction:
Measurand Max. MVAL = times rated value
1,2 or 2,4
Current L1 □⊠
Current L2 □⊠
Current L3 □⊠
Voltage L1-E □⊠
Voltage L2-E □⊠
Voltage L3-E □⊠
Active power P □⊠
Reactive power Q □⊠
Frequency f □⊠
Voltage L1-L2 □⊠
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