Ceres Municipality, Western Cape is responsible for the strategic control of the grid network for the areas of Ceres (Nduli & Bellavista) and in future Wolsley and Tulbagh, controlling 26 MVA of power to more than 34 000 people.
This critical operation supplies the bulk of its electricity to residential, industrial, agricultural, and hospital users. The Ceres network has little tolerance for inefficiencies and downtime and requires careful and constant scrutiny, if quality supply levels are to be maintained.
In the early days of 1926 and 1953, Ceres commissioned its first and second hydroelectric turbine schemes for electricity, with capacities of 95 kW and then one megawatt respectively, this brought the first sustainable electricity supplies to the area. This long running hydroelectric scheme is still in commission and producing electricity today, although in a less crucial role, and the old hydroelectric turbine scheme augments Ceres' electricity network.
For more than 50 years, Ceres relied predominantly on manual and semi automated system applications to monitor and control their electricity network. As a result, management were unable to view important network management data and synchronise essential information in a realtime situation.
Expansion of the network and the ever increasing cost of imported control systems and equipment prompted Ceres management to investigate alternative locally developed scada systems of a proven design. The challenge was to upgrade the control process, to accommodate realtime control of the network, whilst optimising energy monitoring and management.
The equipment
The Netelek scada system and equipment includes all the necessary building blocks of a complete supervisory control and data acquisition system. It offered a new approach to scada, with the use of more programmed intelligence in each field device to achieve the required system performance. The use of industry standard data protocol and communication media added to system reliability and flexibility for future expansion.
Advanced features
NetControl uses a system where the Supercon instruments are the primary data collectors. This means that the voltage and current signals only need to be connected to the Supercon instruments. The Supercon converts the measured parameters into a digital format, which eliminates the need to wire all the analog signals to the telemetry equipment. The Supercons can retrieve and update all data every 20 seconds. Status information for a specific breaker is sent via a Supercon mounted in the breaker panel to the substation CP6000s by a twisted pair, reducing the complexity and total wiring cost.
NetControl provides trending analysis of data over time, easy numerical analysis of data using Microsoft and Excel and specific data reports, using Microsoft Word. Online access to historical and realtime information is achieved using the NetControl information database.
The NetControl provides Ceres with a realtime record of over 400 digital tags and over 300 analog tags, and the system can accommodate more than ten years of data storage and archives. This huge amount of data is analysed using the NetControl Analytical tools, which have helped Ceres aggregate data for specified areas to determine network performance, recording, power factor correction, the cause of failures - and provided a means of improving operational philosophies.
NetControl advantages
With Industrial Standard RTU Protocol (compatible with Modbus RTU Protocol) no special drivers for scada software are needed. The binary protocol ensures one of the most compact message frame formats available which means the minimum communication traffic and time. Cyclic redundancy checksum with each message ensures high data reliability. The simple wiring between Supercon and the CP6000 ensures reliability and low maintenance.
Future expansion and flexibility
System expansions are inexpensive and easy because expansion only needs additional front-end devices (Supercon instruments) and connection to the existing radio station's RS485 communications network. No additional communication or other expansion cards on the radio outstation are required.
Cost-effective
Leon Swanepoel, assistant to the chief electrical engineer and Brian van der Watt, Ceres' chief electrical engineer, both concur, "The Netelek, NetControl system is an ideal network integration management tool. The integrated combination of the NetControl system and software with our existing systems has provided the perfect solution to problems experienced in the past of optimising supervisory control and data acquisition." And in terms of value, "the system has paid for itself several times over."
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