DISTRIBUTED NETWORK PROTOCOL (DNP) DEFINITIONS AND BASIC TUTORIALS

The development of the distributed network protocol (DNP) was a comprehensive effort to achieve open, standards-based interoperability between substation computers, RTUs, IEDs, and master stations (except intermaster station communications) for the electric utility industry. DNP is based on the standards of the IEC TC 57, WG 03.

DNP 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 (e.g., limited transport-layer functions to support 2K block transfers for IEDs as well as radio frequency [RF] and fiber support).

The present version of DNP is DNP3, which is defined in three distinct levels. Level 1 has the least functionality (for simple IEDs), and Level 3 has the most functionality (for SCADA master station communication frontend processors).

The short-term benefits of using DNP are interoperability between multi-supplier devices; fewer protocols to support in the field; reduced software costs; no protocol translators needed; shorter delivery schedules; less testing, maintenance, and training; improved documentation; independent conformance testing; and support by independent user group and third-party sources (e.g., test sets, source code).

In the long-term, further benefits can be derived from using DNP, including easy system expansion; long product life; more value-added products from suppliers; faster adoption of new technology; and major operations savings

DNP was developed by Harris, Distributed Automation Products, in Calgary, Alberta, Canada. In November 1993 responsibility for defining further DNP specifications and ownership of the DNP specifications was turned over to the DNP User Group, a group composed of utilities and suppliers who are utilizing the protocol.

The DNP User Group is a forum of over 300 users and implementers of the DNP3 protocol worldwide. The major objectives of the user group are to maintain control of the protocol and determine the direction in which the protocol will migrate; to review and add new features, functions, and enhancements to the protocol; to encourage suppliers and utilities to adopt the DNP3 protocol as a standard; to define recommended protocol subsets; to develop test procedures and verification programs; and to support implementer interaction and information exchange.

The DNP User Group has an annual general meeting in North America, usually in conjunction with the DistribuTECH Conference in January/February. The web site for DNP and the DNP User Group is www.dnp.org.

The DNP User Group Technical Committee is an open volunteer organization of industry and technical experts from around the world. This committee evaluates suggested modifications or additions to the protocol and then amends the protocol description as directed by the user group members.

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