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Home News 08051: Steenbras Power Station - Element leading with new technology

08051: Steenbras Power Station - Element leading with new technology

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08051 article

The 180 MW Steenbras Power Station, located 50 km from Cape Town near Gordon’s Bay in the Western Cape, was the first hydroelectric pumped-storage scheme in Africa when it was built more than 30 years ago. It was primarily intended to generate during peak loads and is used as the regulating station on the City of Cape Town’s electricity distribution network.

Each of the station’s four 45 000 kW generator units acts as a pump-motor in one mode and a turbine-generator in the other. Surplus national generating capacity is employed to utilise relatively low cost off-peak electricity available at night to pump water from a lower to an upper storage reservoir. During periods of peak demand in the day the water is released back to the lower reservoir, thereby generating electricity as in a conventional hydroelectric power station.

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Element Consulting Engineers was appointed as the consulting engineer and project manager resposible for overseeing the replacement of existing  power transformers for the Steenbras Power Station generators.  The power station uses 4 x 60MVA transformers to convert 12kV to 132KV to supply it into the backbone of the City’s electrical network. Which sets this project apart from others is that ECE implemented new technology for the temperature control, which is now also being followed by other supply authorities with their power transformers. The new technology uses optical fibres to sense temperatures inside the transformer for condition monitoring. Temperature control is important to ensure that it does not overheat due to a faulty condition, as well as to prevent overloading. Due to high cost and critical importance of this component it is crucial to ensure that the transformers remain in good working condition.

The conventional method of determining the temperature is by measuring it at one or two spots inside the tank, and by deducting the temperature from the load current. The new technology which utilises optical fibres senses the core temperature at various locations, including “hot spots”, as well as all HV and LV winding temperatures. The advantages of the new technology is that it provides additional info about whether the oil flow is according to the design parameters, and as this information is recorded, a complete history of the transformer is available. The information obtained assist the client to manage and operate the transformer to its optimal capacity, ensures that faults are detected earlier and increases the lifespan of the transformers accordingly.      

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Element Consulting Engineers was responsible for the compilation of the electrical specifications, project management as well as involved in the design thereof. ACTOM Power Transformers has been awarded the contract to produce four customised 60 MVA 12/132 kV units to replace the old transformers. The contract is also among the first orders that ACTOM has received for higher rated power units since upgrading and expanding its plant to enable design and manufacture of power transformers up to and including 160 MVA.

The transformers for Steenbras were ordered in early-April 2009 by Consolidated Power Projects, the electrical project management company contracted by the City of Cape Town’s Electricity Services Department to procure, install and commission the new power transformers in place of the existing 55 MVA units.

The new transformers will incorporate air-forced and oil-directed equipment for cooling. “The design of these transformers is based on the most advanced technology available since the expansion of our plant,” says Ronnie Russell, ACTOM Power Transformers’ general manager. 

Last Updated (Friday, 08 April 2011 09:46)