IEC 60870-5-103
The standardized IEC 60870-5-103 telemetry protocol is used for serial communication of protective devices with the corresponding control systems.
The telemetry protocol defines application units in which the message representation and content are specified and the situations in which the messages are sent are described.
The 103 protocol supports serial data transmission over V.24 at the physical level and can operate up to ten relays over a two- wire line when using RS-485.
All alarm messages from the protection relays are written to text files, stored in the control units and are available for offline analysis.