Instrumentation specialist Endress+Hauser was awarded a contract for the upgrade of three hydro-electric generators at NamPower's Ruacana hydropower station situated on the border river - the Kunene - between Namibia and Angola, making this the first hydropower station in the world to adopt Profibus technology.
Awarded by Namibian parastatal, NamPower, the scope of the project involved upgrading all measurement devices to Profibus using Siemens PLC and scada software.
The Ruacana hydropower plant is NamPower's main source of power generation, this is despite the fact that Ruacana's contribution to Namibia's electrical energy demands has been on a decline - in 1991 Ruacana contributed 69%, while in 1997 this had dropped to 31% due to run of river conditions. Other sources include thermal power generated at Van Eck and Paratus power plants. This is relatively costly due to high fuel costs, and is primarily used to substitute costly imports during peak hours. During dry years imports from Eskom exceed domestic generation as experienced in 1993/4. At full capacity Ruacana produces about 240 MW, depending on the flow of the river.
The hydropower plant, which is an underground power station with three units of 80 MW each, was put into operation in 1977/8. By the 1960s NamPower (previously called SWAWEK - South West African Water and Electricity Corporation) was committed to the construction of the hydropower plant. However, the initial erection and operation of Ruacana was less than smooth, being disrupted by political activity in the region. It was only in the early to mid-eighties that the power station could operate with any sort of regularity.
The regulating reservoir at the plant allows only for daily and limited weekly regulation. Real water management regulation was planned to be provided from the Gove dam and Calueque reservoir, both located on the upper Kunene on Angolan territory. Yet, Gove as well as Calueque have for various reasons never been operated according to the initial intentions.
The seasonal river flow at Ruacana is thus largely fluctuating, varying with extensive spilling during the wet season and nearly no generation on certain occasions during the drought periods. "Because of the unpredictable water flow in the Kunene River, Ruacana demands high levels of reliability and availability when the water level is high," informs Ivan De Waal, Endress+Hauser projects manager. Usually only one or two of the generators are active, with the third in reserve for the rainy season.
Endress+Hauser completed Unit 3 in December 2000, Unit 2 in December 2001 and was scheduled to complete Unit 1 in December 2002. The company supplied over 100 Profibus PA devices per generator consisting of pressure, level and temperature devices.
Instrumentation supplied included the Prosonic T, a compact ultrasonic transmitter for non-contact level detection, the Promag 33 measuring system that makes high-quality electromagnetic flow measurement possible, the Cerabar S PMC 731 pressure measurement application, the Deltabar range for differential pressure measurement applications, and, finally, the TMT 184 temperature head transmitter with a Profibus-PA protocol for converting various input signals into digital output signal.
"The interface between the PLC, scada and control room will enable the operator to enter all necessary setpoints and control parameters, this is in addition to starting and stopping the units and monitoring feedback through digital signals," says De Waal.
Endress+Hauser presented Ruacana with a total solution, from initial consulting and site inspection, to the engineering specifications, network layout and drawing of diagrams for installation of the devices. "Due to the remote location, part of the package included dedicated training at the plant," states De Waal.
For more information contact Grant Joyce, Endress + Hauser, 011 262 8000, [email protected], www.za.endress.com
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