DNP 3.0

The DNP protocol was developed for communication with telecontrol substations and other intelligent electronic devices (IEDs). Designed with current and future telecontrol applications for the North American power industry in mind, it is still widely used to this day. Although the Harris company originally initiated its development, responsibility for further upgrades and maintenance then passed to the DNP User Group, a user and vendor association for the protocol. 

Originally, the protocol's main use was for slow serial communication, its present-day version also supports TCP/IP-based operation.

Unlike related protocols such as IEC 60870-5-101, DNP 3.0 commands a very powerful application layer, which allows the decoding of data without the use of implicit parameters. DNP 3.0 supports a variety of representation modes for information objects, offering a high degree of interoperability on the application layer. This was achieved at the cost of greater complexity, which makes implementation more difficult and demands much more time for implementation and testing. 

Compared with IEC 60870-5-101, the protocol's transport layer allows fragmented data transmission of higher volumes. This has a positive effect on communication via TCP/IP, as the whole network bandwidth can be fully utilized.

A further advantage compared with IEC 60870-5-101 is provided by the additional feature of requesting receive acknowledgement from the remote terminal. A substation can remove data from its buffer after it has actually arrived at its destination and has been acknowledged. This feature facilitates the use of simple routers. 

As is true for the IEC 60870-5-101, its link layer is based on the IEC 60870-5-1 and IEC 60870-5-2 standards. But only balanced transmission mode is used, which was exclusively intended for full-duplex point-to-point connections. As DNP 3.0 is also used for half duplex party-line operation, a mechanism to prevent collisions was added. As this mechanism requires specific functionalities in the DCEs - which might not always be present - and accurate configuration of the timing, in practice its use often involves some difficulties. In many cases this drawback results in ignoring the link layer functionality, so that only the unacknowledged (SEND/NO REPLY) service with poll-initiated data transmission on the application layer is used instead. The problem can be avoided in TCP/IP operation, as collisions cannot occur or are averted by the network.
 

Two forms which have to be completed by every manufacturer help ensure maximum interoperability between devices:

  • DNP Device Profile
    which defines the basic protocol functionalities supported by the device
  • DNP Implementation Table
    which defines the information objects and their representation supported by the device.

In addition subsets of the full function range are defined and divided into three levels:

  • DNP Level 1
    is the smallest subset and defines only the simplest functions and information objects. This level is best suited for IEDs.
  • DNP Level 2
    is intended for larger devices such as RTUs.
  • DNP Level 3
    suits larger RTUs and offers practically the complete range of DNP 3.0 functionalities.

These levels are downward compatible, for instance a master of level 2 supports levels 1 and 2. .

For each device there is a "device profile" that shows which levels are supported. Compatibility tests were developed in 2000 (Certification Procedure) with detailed descriptions of device behavior to ensure maximum compatibility, but until now only for levels 1 and 2.

ISO/OSI Model

7 Application Layer DNP V3.0 Data Object Library
DNP V3.0 Application Layer
6 Presentation Layer n/a
5 Session Layer n/a
4 Transport Layer DNP V3.0 Transport FunctionsDNP V3.0 Transport Functions
DNP V3.00 Data Link Layer
TCP, UDP
3 Network Layer IP
2 Link Layer DNP V3.00 Data Link Layer
IEC 60870-5-2 (balanced)
IEC 60870-5-1 (FT 3)
IP
1 Physical Layer RS232 (V.24)Ethernet (IEEE 802.3)

Implemented Protocol Stacks

DNP V3.00, Master

DNP V3.00, Slave

Applicable Products

  • ipConvLite
    ipConvLite

    inexpensive protocol converter for standardized application

  • ipConvOPC
    ipConvOPC

    Softwarepackage for conversion between OPC DA 3.0 Server and standard protocols

  • ipConvPBS
    ipConvPBS

    Universal protocol converter with integrated PROFIBUS-DP, slave interface

  • ipConvPBM
    ipConvPBM

    Universal protocol converter with integrated PROFIBUS-DP, master interface

  • ipConvPNM
    ipConvPNM

    Universal protocol converter with integrated PROFINET-IO, master interface

    Available soon !
  • ipConvPNS
    ipConvPNS

    Universal protocol converter with integrated PROFINET-IO, slave interface

  • ipConv
    ipConv

    Universal protocol converter for highest degree of flexibility

References

  • Project CFE
    Project CFE, Mexico

    Products: ipConv
    Protocol Stacks: Conitel-2020, Slave DNP V3.00, Slave DNP V3.00, Master Harris-5000/6000, Slave Recon, Slave Indactic 33/41, 2033, Slave Fuji, Slave XMAT, Master

  • HVDC
    HVDC, New Zealand

    Products: ipConv ipConvLite
    Protocol Stacks: DNP V3.00, Slave DNP V3.00, Master TASE.2, Server TASE.2, Client Modbus, Master Simatic TDC, Master

  • BASSLINK HVDC Victoria / Tasmania
    BASSLINK HVDC Victoria / Tasmania, Australia

    Products: ipConv
    Protocol Stacks: DNP V3.00, Slave Simatic TDC, Master

  • Neptune RTS
    Neptune RTS, USA

    Products: ipConv
    Protocol Stacks: DNP V3.00, Slave Simatic TDC, Master Modbus, Master CDC Type I, Slave

  • FSC Dayton, SVC Porter/Ninemile
    FSC Dayton, SVC Porter/Ninemile, USA

    Products: ipConv
    Protocol Stacks: DNP V3.00, Slave Simadyn-D, Master Simatic TDC, Master

  • PLN Gambir
    PLN Gambir, Indonesia

    Products: ipConv
    Protocol Stacks: DNP V3.00, Slave DNP V3.00, Master HN Z 66 S 11/15, T63, Slave HN Z 66 S 11/15, T63, Master

  • CFE
    CFE, Mexico

    Products: ipConv
    Protocol Stacks: Harris-5000/6000, Slave Fuji, Slave DNP V3.00, Master

  • FSC Tecali and Juile
    FSC Tecali and Juile, Mexico

    Products: ipConv
    Protocol Stacks: DNP V3.00, Slave Simadyn-D, Master

  • DUBAL21
    DUBAL21, United Arab Emirates

    Products: ipConvLite
    Protocol Stacks: DNP V3.00, Slave Modbus TCP/IP, Master

  • SVC Penrose/Marsden
    SVC Penrose/Marsden, New Zealand

    Products: ipConv
    Protocol Stacks: DNP V3.00, Slave DNP V3.00, Master Simatic TDC, Master