Automation

What is DNP3?

DNP3 is a commonly misunderstood term that you may have heard referred to when talking about SCADA and telemetry systems. We have included some information here to try to demystify DNP3 for those who are not as technically savvy with telemetry systems. DNP stands for Distributed Network Protocol.

Firstly, we are going to use the analogy of two humans communicating in order to help understand where DNP3 fits. When we communicate between each other we DNPmay use a great variety of different communications mediums such as a walkie talkie or 2 way radio, a fixed telephone line, a mobile telephone line or perhaps over the internet using skype or similar. While the medium we use can change, it will be necessary for us to communicate using the same language, i.e. English.

When we talk about communicating around our SCADA and telemetry systems we can also use different communications methods like Ethernet cable, radio and public telephone systems just as when two humans communicate. In
this case though we must also use the same language and the language we commonly use is DNP3. So, when somebody refers to DNP3 they are referring to the language devices and SCADA machines talk and not the communications medium that they use, like radio. This is a common misconception for people not technically clear on DNP3 and so hopefully that analogy clears things up.

Why is it powerful?

There are a few reasons why DNP3 is so powerful, and commonly used in telemetry systems in Australia:-

  1. It is a standard and open. This means that the “language” is readily available and all DNP3 devices communicate using the same language. Early RTU’s communicated using proprietary protocols which meant the language they communicated in was known only to other products produced by the same vendor. Today, many devices are multi-lingual in that they will communicate using their proprietary protocol but also allow communications using the DNP3 protocol, this has been done by many vendors to allow a gradual upgrade of their network to DNP3 over time.
  2. It is a routing protocol. This is a particularly important and key feature of the DNP3 protocol in that it can communicate via different communication networks to reach the destination of the message. For example, the SCADA machine may be connected to an Ethernet connection but the RTU may be on a radio connection, DNP3 is able to be routed through from the Ethernet connection to the Radio connection via an intermediate RTU. This sounds complex, but in simple terms it would be like you talking across a phone connection to your friend, and them relaying the message to someone on a nearby walkie talkie. The power of DNP3 is that this can be done very easily in most modern RTU’s without the need for complex I/O mapping.
  3. It makes good use of the communications channel. DNP3 has been designed to be able to operate on both high speed Ethernet networks and slow speed radio networks and is very good at “only communicating when necessary”. For example, when a pump turns on or off DNP3 will send a message through notifying the SCADA of that one change. Fixed polling protocols, like MODBUS are unable to achieve this as they have to constantly update all data by polling. Back to our human analogy, this would be like you continually asking your friend to tell you what the traffic light is showing, in a polling protocol example the friend would be constantly saying green, green, green, green then red, red, red every second or so. With DNP3, the friend would only tell you when the light changes therefor using up much less bandwidth.
  4. Many friends at once. What this point number 3 above means is that you could hold conversations with many friends at once and this is indeed the power of DNP3, allowing many pumping stations, substations or gas wells to communicate on the same network.

Integrating DNP3

DNP3 is indeed a complex protocol to integrate and while we hope this clears a few misconceptions about DNP3 up we would encourage you, should you wish to implement DNP3 communications to use a qualified and experienced systems integrator as getting the integration right is absolutely essential in ensuring you get all the best features of DNP3. Latitude products are a supplier of quality product only and do not provide integration or engineering services, however, we will give you a list of integrators and engineering companies you can talk to by contacting sales@automationgroup.com.au 

More Information

For more information on DNP3 simply email to sales@automationgroup.com.au with the subject title “More DNP3″ and we will automatically send you an email with more detailed information. Alternatively you may like to start some more research here at http://en.wikipedia.org/wiki/DNP3

See our range of DNP3 certified RTUs here