IEC 60870-5-103

IEC 60870-5-103 is an international standard, released by IEC (International Electrotechnical Comission) at the beginning of the 90ies. It allows the coupling of a central unit to several protection devices and is primarily used in the energy sector. The standardized function range is especially designed for the communication with protection devices and therefore it's difficulty to adapt it to other applications.

The protocol is based on the EPA architecture (Enhanced Performance Architecture), defining only the physical link and application layer of the OSI layer model.

IEC 60870-5-103 is mainly used for relatively slow transmission media on asynchronous V.24 (RS232) and RS485 interfaces. Connection via fibre optics is also covered by the standard. The transmission speed in general is specified with a maximum of 19200 Baud.

IEC 60870-5-103 is a 'Companion Standard' and is extended by the following standards:

• IEC 60870-5-1
  defines different frame formats, IEC 60870-5-103 applies only the FT1.2 format
• IEC 60870-5-2
  defines the transmission mode on the link layer
• IEC 60870-5-3
  defines the basic application data structure
• IEC 60870-5-4
  defines how information elements are encoded
• IEC 60870-5-5
  defines basic application layer functions

Interoperability between devices by different vendors is ensured by the interoperability list, which is defined by the standard. In the list, the function range is defined for each device by marking the applicable functions. The common denominator between different vendor lists defines the possible function range.

In addition to standard protocol functions, IEC 60870-5-103 also accommodates extensions for proprietary vendor-specific functions. These are used extensively by manufacturers of protection devices. As a result compatibility between devices by different vendors cannot always be ensured. The function range can further be extended by using generic data objects, which allow the transmission of any kind of information in both directions.