Dnp3 Overview; Dnp3 Standard - Hitachi Relion 670 Series Communication Protocol Manual

1MRK511391-UUS Rev. L
Section 2
DNP3 is a communication protocol used between components in process automation systems. Its main
use is in utilities such as electric and water companies. Usage in other industries is not common,
although technically possible. Specifically, it was developed to facilitate communications between various
types of data acquisition and control equipment. It plays a crucial role in SCADA systems, where it is
used by SCADA master stations (aka Control Centers), RTUs, and IEDs.
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DNP3 standard

The DNP3 protocol was developed by Westronic based on the early versions of the IEC 60870-5
standard telecontrol protocol specifications. DNP is now governed by IEEE Std 1815-2012 IEEE
Standard for Electric Power Systems Communications - Distributed Network Protocol (DNP3)
www.dnp.org.
The protocol is based on the EPA, a simplified model of the ISO/OSI model. It specifies the data link
layer, the application layer and a transport pseudo-layer. To support advanced RTU functions and
messages larger than the maximum frame length as defined by the IEC document 60870-5-1, the DNP3
data link is intended to be used with the mentioned transport pseudo-layer. As a minimum, this transport
layer implements message assembly and disassembly services.
Physical layer
Even though the standard does not specify the physical layer, it does however specify how to operate in
a networked environment and also suggests how to avoid collisions between simultaneously sending
devices.
Many implementations use serial communication based on RS-232, RS-485 or even fiber optics.
DNP, 670 series
Communication protocol manual

DNP3 overview

DNP3 communication schematic representation
SCADA master station / control center
External control points
Communication links (radio, microwave, spread-spectrum, twisted-pair, fiber-optics, dial-up, leased line)
Remote substation (station computer and IED)
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Section 2
DNP3 overview
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