Standard RTU

Index

Standards for Remote Terminal Units

Programming the RTU

Discussion on Standards

Index to IEC 870 Standard

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Need for standards

Any large organisation with an ongoing SCADA program, and which over time intends to install a number of discrete SCADA systems, must eventually integrate these systems. Their SCADA program will involve multiple vendors over time and they will face problems due to the SCADA industry's use of proprietary hardware, software and communications protocols.

A smaller organisation may be able to install in one go a SCADA system that encompasses the majority of their operations. They may take a choice that they will buy a proprietary system and rely on that vendor for continued upgrades and support. This may well be an appropriate decision especially if they are assured of good local support.

The prime difference between these two situations is that the smaller organisation can standardise by installing a single system whereas the larger organisation is necessarily faced with a lengthy program, with relatively small expansions at any time (compared to the overall system). Back to Main Index

Standards for Remote Terminal Units

To overcome this standards may be specified. Standards are required in a number of areas. Communications protocols are the major area requiring standards, and there are a number of alternatives.

Modbus is in common use, but it is incomplete as a standard, and not really suited for larger SCADA applications especially those with large radio networks.

The IEC are developing the IEC870-5 set of standards, and these are supported by many standards organisations. It is an emerging standard currently, and is more popular in Europe than America.

DNP3 is a mature standard coming from the electricity industry. It has established a wide following in this industry, and also in America generally. Water utilities (esp in Australia) are adopting this standard for use in SCADA applications.

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Standards for Programming RTU's

If portability and interoperability are to become a reality, then atandards must be adopted for programming the RTU's. Proprietary programming systems will mean previous application programs cannot be reused, and if the RTU's at a site are to be replaced with a different one at a later date, (due to obsolence, maintenance or whatever), the proprietary programming facilities will become a major expense of reprogramming and retesting.

The prime candidate for RTU programming standards is the IEC-1131-3 programming languages.These have been developed for PLC programming, and are increasingly being mandated for use by large manufacturing concerns esp the car industry.

A particular implementation of this standard is the ISAGRAF product is by CJ International. This can be ported to most RTU's with ease, and provides a modern development environment for programming.Isagraf