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DNP 3.0

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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, MasterDNP V3.00, Slave

Applicable Products

ipConvLiteipConvLiteinexpensive protocol converter for standardized application
start price 1.800,- €
Details...
product/ipConvLite/en/ipConvLite_EN.pdf
ipConvOPCipConvOPCSoftwarepackage for conversion between OPC DA 3.0 Server and standard protocols
Details...
ipConvPBSipConvPBSUniversal protocol converter with integrated PROFIBUS-DP, slave interface
Details...
ipConvPBMipConvPBMUniversal protocol converter with integrated PROFIBUS-DP, master interface
Details...
ipConvPNMipConvPNMUniversal protocol converter with integrated PROFINET-IO, master interface
Available soon !
Details...
ipConvPNSipConvPNSUniversal protocol converter with integrated PROFINET-IO, slave interface
Details...
ipConvipConvUniversal protocol converter for highest degree of flexibility
Details...
product/ipConv/en/ipConv_en.pdf

References

Project CFEProject CFE
Details...
MexicoipConv 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 New ZealandHVDC New Zealand
Details...
New ZealandipConv ipConvLite DNP V3.00, Slave / DNP V3.00, Master / TASE.2, Server / TASE.2, Client / Modbus, Master / Simatic TDC, Master /
BASSLINK HVDC Victoria / TasmaniaBASSLINK HVDC Victoria / Tasmania
Details...
AustraliaipConv DNP V3.00, Slave / Simatic TDC, Master /
Neptune RTS, USANeptune RTS, USA
Details...
USAipConv DNP V3.00, Slave / Simatic TDC, Master / Modbus, Master / CDC Type I, Slave /
FSC Dayton, SVC Porter/NinemileFSC Dayton, SVC Porter/Ninemile
Details...
USAipConv DNP V3.00, Slave / Simadyn-D, Master / Simatic TDC, Master /
PLN GambirPLN Gambir
Details...
IndonesiaipConv 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 MexicoCFE Mexico
Details...
MexicoipConv Harris-5000/6000, Slave / Fuji, Slave / DNP V3.00, Master /
FSC Tecali and JuileFSC Tecali and Juile
Details...
MexicoipConv DNP V3.00, Slave / Simadyn-D, Master /
DUBAL21DUBAL21
Details...
United Arab EmiratesipConvLite DNP V3.00, Slave / Modbus TCP/IP, Master /
SVC Penrose/Marsden, New ZealandSVC Penrose/Marsden, New Zealand
Details...
New ZealandipConv DNP V3.00, Slave / DNP V3.00, Master / Simatic TDC, Master /
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