Page 10 - Energize February 2021

NEWS

Modbus in reclosers Serial implementations of Modbus
carry additional limitations, such as
the number of devices on a data link
(maximum 247), and a lack of report
odbus is one of the oldest and most popular communication protocols for supervisory by exception.
control and data acquisition (SCADA) systems. Developed in 1979 by Modicon, Modbus “Due to customer demand to integrate
Mwas originally designed for programmable logic controllers. Today, Modbus owes its our reclosers into legacy communications
popularity to being both simple and royalty free, despite disadvantages against more modern and SCADA systems that use Modbus
SCADA protocols. Despite its drawbacks, Modbus remains actively used in many legacy process protocol, we have implemented the
and electrical utility control environments. Modbus protocol into our SGA software
Noja Power’s latest firmware release for its RC10/RC15 controllers includes an suite,” says the company’s managing
implementation of Modbus. This allows the RC10/15 to be integrated into existing Modbus director Neil O’Sullivan. “This allows easy
SCADA architectures. As with most engineering decisions, selecting Modbus as a SCADA protocol configuration and download of the
carries both advantages and disadvantages. Modbus device file into our controllers
We explore these in Table 1. from the SGA software suite.”

MODBUS USE CASE
Advantages Disadvantages
Modbus can be considered a sound
engineering decision when there is no
• Royalty Free • Modbus provides no security features. There is no protection
requirement for compliance to network
• Low Cost against unauthorized commands, or data interception.
security standards and costs must be
• Low maintenance • Modbus does not support large Binary objects
optimised. Generally, this requires wired
• Modbus provides no description of data objects
and physically secured communications
media, but it is less appropriate where
Table 1: Advantages and disadvantages of Modbus protocol.
wireless communications are involved.
Wireless broadcasting of Modbus
protocol could plausibly be intercepted
by any third party within
communication range, exposing a
significant attack surface.
Legacy systems which are scheduled
for upgrades to achieve compliance with
cybersecurity standards can be
progressively upgraded by replacing
failed RTU equipment with devices that
support both Modbus and more modern
SCADA protocols (such as IEC 61850, IEC
60870 or DNP3­SA). This method
removes the need for entire system
obsolescence, instead providing an
upgrade path over time and maximising
asset utilisation.
Eventually, when all individual
outstation devices are replaced, a new
SCADA server can be implemented, and
the modern outstations can be
reprogrammed to use their modern
SCADA protocols.

CONCLUSION
Modbus remains a popular protocol for
SCADA due to simplicity and cost
effectiveness. For physically secure
environments, it represents a sound
engineering choice for SCADA control at a
low maintenance overhead. Noja Power’s
OSM recloser system can now be directly
integrated into these legacy
environments, while also providing an
upgrade path for the system to more
modern protocols when needs arise. n

SALES: sales@nojapower.com.au

energize | February 2021 | 8