Interoperability in utility industries: overview of the DNP3 protocol

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July 2008 News

The development of DNP3 was a comprehensive effort to achieve open, standards-based interoperability between substation computers, RTUs, IEDs (intelligent electronic devices) and master stations (except inter-master station communications) for the electric utility industry. Also important was the time frame; the need for a solution to meet today's requirements. As ambitious an undertaking as this was, the objective has been reached, and since inception, has also become widely utilised in adjacent industries such as water and waste water, transportation and the oil and gas industry.

DNP3 is based on the standards of the International Electrotechnical Commission (IEC) Technical Committee 57, Working Group 03 who have been working on an OSI 3 layer Enhanced Performance Architecture (EPA) protocol standard for telecontrol applications. DNP3 has been designed to be as close to compliant as possible to the standards as they existed at time of development with the addition of functionality not identified in Europe but needed for current and future North American applications (eg, limited transport layer functions to support 2K block transfers for IEDs, RF and fibre support). DNP3 has been selected as a Recommended Practice by the IEEE C.2 Task Force; RTU to IED Communications Protocol.

DNP3 was developed by Harris, Distributed Automation Products. In November 1993, responsibility for defining further DNP3 specifications and ownership of the DNP3 specifications was turned over to the DNP3 Users Group, a group composed of utilities and vendors who are utilising the protocol.

DNP3 is an open and public protocol. In order to ensure interoperability, longevity and upgradeability of the protocol the DNP3 Users Group has taken ownership of the protocol and assumes responsibility for its evolution. The DNP3 Users Group Technical Committee evaluates suggested modifications or additions to the protocol and then amends the protocol description as directed by the Users Group members.

Complete documentation of the protocol is available to the public. The four core documents that define DNP3 are: Data Link Layer Protocol Description, Transport Functions, Application Layer Protocol Description and Data Object Library (referred to as the Basic 4 Document). The Users Group also has available to members the document DNP3 Subset Definitions, which will help implementers to identify relevant protocol elements.

To find out if DNO is the right standard for you read the paper by Danny Johnson at http://www.dnp.org/About/Default.aspx or for more information contact Jaco Hoogenboezem, SCADAgroup, +27 (0)83 282 5706, [email protected], www.controlmicrosystems.com

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Interoperability in utility industries: overview of the DNP3 protocol

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