DNP3.0 - Distributed Network Protocol 3

What is the DNP3.0 protocol?
DNP3 — Distributed Network Protocol 3
Distributed Network Protocol 3 (DNP3) is a set of communications protocols used between components for automation systems in electric, industrial and water sectors.
It is a key protocol in SCADA systems, where it is primarily used for communications between a master station and RTUs or IEDs.
- While IEC 60870–5 was still under development and was waiting to be standardized, there was a need for an interoperable communications standard to interconnect various multi-vendor components in the network.
- Thus, in 1993, the partially completed IEC 60870–5 protocol specifications were used as a base for an open and immediately implementable protocol that specifically catered to North American requirements.
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DNP3 is a layer 2 protocol on the OSI model.
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The protocol provides data fragmentation, error detection, multiplexing, link control, prioritization, and layer 2 addressing services.
- For error detection, it relies on cyclic redundancy check codes.
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Further, it defines a transport function (analog to layer 4) and an application layer (layer 7) that defines functions and generic data types for common SCADA applications.
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Designed for harsh environments, DNP3 is more robust, efficient, and interoperable than older protocols like Modbus, which is still sometimes preferred for its simplicity.
Modbus vs DNP3
Modbus is an application layer protocol, whereas DNP3 consists of both an application and data link layer. Another difference is that DNP3 also supports unsolicited messaging. This means that RTUs can send updates when a change of status happens, without waiting to be polled by the master.
Both protocols can be used over various media, such as RS-232, RS-485, and TCP/IP.
While Modbus has a specific variant for TCP/Ip communcations, DNP3 needs to be wrapped within TCP/IP.
Since you can send more data in smaller packets and unlike Modbus, it is an event-driven protocol, meaning that network devices are able to transmit unsolicited responses and continuity is not required, using DNP3 can save lots of bandwidth. Furthermore, DNP3 is highly standardized and provides high compatibility and interoperability between devices from many different vendors.
Still, some prefer Modbus for its simplicity and the high number of devices that support the protocol. So, both Modbus and DNP3 can be implemented in functional and efficient SCADA systems, making it strongly dependent on the project network.
IEC 104 vs DNP3
DNP3 and IEC-104 have both been specifically developed for SCADA communication beyond the substation level, for instance in order to control a circuit breaker from a Control center.
However, there are a few advantages of DNP3 that make it superior in certain applications.
- For the transmission of larger data volumes over longer distances, DNP3 is preferred as it sends larger but fewer data packages than IEC-104, which sends a high number of small packages.
- DNP3 also enables faster data transmission by operating in higher baud rates (number of data bits transmitted in one second) than the IEC standards.
- At last, if the bandwidth is limited, DNP3’s data priority classes (Class 1,2,3) allow the controller to poll in various frequencies, as opposed to IEC-104, which only provides a constant polling frequency.
Tags: control center, DNP3, gateway, Grid Automation, HMI, modbus, RTU, SCADA, Substation Automation
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Communication Protocols
IEC 60870–5 is a protocol standard for telecontrol, teleprotection, and other telecommunication functions for electric power systems.
IEC 60870–5‑104 (short IEC104) is a companion standard defining how to extend the IEC 60870–5‑101 protocol to gain network access using standard transport profiles.
DLMS/COSEM (or IEC 62056) is the main global standard for smart energy metering, control and management. It includes specifications for media-specific communication profiles, an object-oriented data model and an application layer protocol.
Modbus is a communications protocol based on master/slave (RTU) or client/server (TCP/IP) architectures that can operate on the 1st, 2nd, 7th level of the OSI Model.
Originally designed in 1979 by Modicon for its range of PLCs, it is now a de facto standard communications protocol in the industry, becomming the most widely available protocol for the connection of industrial electronic devices.
Distributed Network Protocol 3 (DNP3) is a set of communications protocols used between components for automation systems in electric, industrial and water sectors.
It is a key protocol in SCADA systems, where it is primarily used for communications between a master station and RTUs or IEDs.
ICCP (Inter-Control Center Communications Protocol) is a standard protocol for communications between control centers, which is part of the IEC 60870–6 standard under the name of TASE.2 Telecontrol Application Service Element 2.
It is being used around the world to exchange data over wide area networks (WANs) between grid operators, utilities, virtual power plants, regional control centers and other generators.
PROFIBUS (Process Field Bus) is an open standard for fieldbus communications in industrial automation systems that was first promoted in Germany in 1989.
The now most commonly found “Profibus DP” provides simple communications between Profibus masters and their remote I/O slaves.
DNP3 & iGrid
We have collected, converted and transferred data using the DNP3 protocol in projects all over the world with many different meters. All of our systems are able to communicate with and convert the protocol according to project needs.
The Slimmest Gateway
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High-performance SCADA for the visualization and control of substation data. It is able to run either in client/server or standalone modes, providing advanced functionalities such as hot-standby redundancy, automatic line coloring, events notification (via e‑mail and sms), SQL logging, and reports generation.

iRTU – With I/Os for Direct Data Acquisition
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iGW‑S Substation Gateway
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