Spectrum Communications designed and implemented an advanced scada system for the Northern Pretoria Metropolitan Substructure utilising the latest technology and standards.
The system design was based on the following philosophy:
* RTUs must be off the shelf, modular and be able to monitor discrete inputs/outputs from switchgear not equipped with new modern protection relays.
* RTUs must be able to communicate to IEDs in substations (eg New microprocessor-based protection relays, quality of supply recorders, energy meters, etc.)
* The communications protocol must be the popular Electric Utility Protocol, DNP3 and RTUs must comply with this standard.
* High-speed radio-based system capable of handling the data throughput of a demanding electrical system.
* Off-the-shelf scada package.
The tele-FLEX RTU is an advanced telemetry device, which is locally developed and manufactured by Spectrum Communications. It is a modular open system, which allows for monitoring and control of I/O through a number of off the shelf I/O cards. With new developments in protection relays, etc. the system also makes it possible to communicate to various intelligent devices over the same communications channel therefore providing an integrated communications gateway between various IEDs and the scada system.
New digital radio system
Large amounts of data typical on an Electrical system require a radio system that can handle the amount of traffic without degrading the performance of the system. Analog radios were an option, but long runup times and low baud rates would have had a serious impact on the performance of the system.
Spectrum's solution incorporated new digital radios based on the latest design technologies from Microwave Data Systems. This significantly expanded the performance and capability of licensed, narrowband, data telemetry radios. The new MDS4710E Digital Radio has an industry leading key-up time of 2 ms with a baud rate scalable up to 9600 bps.
The radio also provides an added benefit which allows you to communicate from any host software remotely to the IED in the substation via a transparent RS232 link, which allows users to re-program or download settings remotely from the host software.
Citect, one of the worlds leading scada packages was configured to provide the operators with a wide range of functionality and flexibility. Included are features such as system performance data, definable security levels, data exchange and reporting.
Communications was based on the DNP3, as specified by the NRS. This installation is claimed to be the largest radio-based DNP3 system in southern Africa, which allows easy integration to other municipalities, REDs and Eskom in the future. Because it is an open standard, it allows future equipment suppliers offering DNP3 compliant products to communicate directly into the same scada system.
This project is a model for future Electrical Utility scada systems. The success of this project was made possible due to Spectrum's 27 years of experience in the field of telemetry and ongoing R&D, with high calibre people locally at the forefront of new technology and developments in the telemetry/scada industry.
Spectrum Communications
(011) 787 9633
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