Practical_modern_SCADA_protocols_-_dnp3,_60870-5_and_Related_Systems

3
Open SCADA protocols DNP3
and IEC 60870
3.1 Interoperability and open standards
Historically, SCADA system communication protocols have been developed as proprietary
protocols, each created by a manufacturer as part of a proprietary system, to meet
the specific needs of a particular industry. This was a matter of necessity, as suitable
standards had not hitherto existed. However, proprietary protocols have disadvantages for
the user. As a system is developed over time the owner is either locked in to expansion
using the same proprietary system, or is compelled to replace substantial parts of the
system to change to another manufacturer’s protocol.
Arising from this underlying disadvantage and the increasing use of SCADA systems
generally, the need for open standards became recognized. This recognition has translated
into efforts by a number of organizations in a number of countries. However, the emergence
of standards that have wide acceptance has been a slow process.
The key benefit of an open standard is that it provides for interoperability between
equipment from different manufacturers. This means for example that a user can purchase
system equipment such as a master station from one manufacturer, and be able to add
RTU equipment sourced from another manufacturer. The RTU in turn may have a number
of control relays connected to it which are intelligent electronic devices and also use the
protocol. All of this equipment may be sourced from different manufacturers, either in
an initial installation, or progressively as the system is developed over time. Some of
the different benefits arising from the use of open protocols are listed below, grouped into
immediate and long-term effects.
3.1.1 Immediate benefits
• Interoperability between multi-vendor devices
• Fewer protocols to support in the field
• Reduced software costs
• No protocol translators needed
• Shorter delivery schedules
• Less testing, maintenance and training