A collection of protocols is known as DNP3 (Distributed Network Protocol). It is utilized between system components in SCADA systems, where it plays a significant role. The protocol was created expressly to allow RTUs to communicate with one another.
We can communicate with one another via a wide range of different communication channels, including walkie-talkies or two-way radios, fixed telephone lines, mobile telephone lines, or even the internet using programmes like Skype or something similar. While the method of communication may vary, it will be important for us to use the same language, which in this case is English. Just as when two people interact, we may also use many forms of communication when talking about our SCADA and telemetry systems, including Ethernet cable, radio, and public telephone lines. But in this instance, we also have to speak the same language, which is DNP3.
Thus DNP3 is a group of communication protocols that are employed by various parts of process automation systems. Its primary application is in utilities like water and power providers. It is not frequently used in other sectors. It was designed for interoperability with many forms of data collecting and control equipment. It is employed by SCADA Master Stations (also known as Control Centers), Remote Terminal Units (RTUs), and Intelligent Electronic Devices (IEDs) in SCADA systems, where it plays a critical role. It is mostly utilized for interconnecting an IED or RTU with a master station. The Test Harness is an effective tool for DNP3 protocol testing, IEC 60870-5, and Modbus devices.
HOW DOES DNP3 PROTOCOL WORK?
In order to enable communication between master stations and remote units, the DNP3 protocol merely uses 27 fundamental function codes. In order to accomplish this, some function codes will enable the master to ask for and receive information on the state of a distant device, while other function codes will enable the master to choose or modify the configuration of the remote unit. The DNP3 master station uses a number of function codes primarily for operating the machinery or remote unit at remote locations. The DNP3 remote device receives the majority of its communications from the DNP3 master station. The Unsolicited Message (o/p message), however, is started by a remote device and causes an alarm. So that when an alarm is triggered, this message notifies the master.
DNP3 OBJECT LIBRARY
A collection of items that are typically used in SCADA systems is included in the DNP3 protocol framework. These things consist of:
Binary Inputs
They’re employed to report gear properties that exist in two states. For instance, whether the electricity is on or off, or whether an access panel is open or shut.
Analog Inputs
This additional typical object is utilized to report qualities that have a range of possible values. For instance, the main power can range from 110 to 128 VDC, and the exhaust fan speed can range from 40 to 400 RPM.
Using these typical objects to report to their master is made simple for the maker by this library while designing the DNP3 remote responder. Also, it makes it simpler for masters to combine and present the information gathered from remotes for decision-making. The DNP3 library’s objects are separated into Groups and Variations. The Analog Input group, for example, provides six options to deliver 16 or 32-bit integer or floating-point values, with or without a status bitmap. Eight different configurations of the Analog Event group are available to deliver 16 or 32-bit integer or floating-point data with a status bitmap and with or without a timestamp. You should be aware that variations without a status bitmap are not included in the Analog Event group.
DNP3 MESSAGE STRUCTURE
Simple serial telemetry systems (like TBOS) are byte-oriented and only exchange one byte when communicating. Packet-oriented expanded serial telemetry systems, like TABS, exchange packets of data to communicate. The packets’ header, data, and checksum bytes are all present. DNP3 utilizes the packet structure and is similarly packet-oriented. If the remote device has the desired data, it will respond with it when the master submits a Read request for the object or objects. To create the output actions related to the chosen object reference, the master sends the command Operate. Also, as was already said, the remote sends an Unsolicited Message when a particular event takes place.