Siemens to repair HVDC transformers in Mozambique

Siemens Power Transmission and Distribution (PTD) is repairing and overhauling two strongly overloaded 180 t transformers in Mozambique at the Cahora-Bassa dam.

The two power transformers were installed in the 1970s during construction of the high voltage direct current (HVDC) transmission link, along which power from the hydro generation plant in Mozambique is conveyed 1450 km to Johannesburg in South Africa.

The 1920 MW long-distance HVDC link between Songo (at the Cahora Bassa dam in Mozambique) and Apollo (between Pretoria and Johannesburg in South Africa) has been back in operation since late 1997, following years of standstill owing to the civil war, and has been running at full power since 1998.

Nevertheless, none of the 24 HVDC power transformers can be allowed to fail, for the two backup transformers provided for emergency operation are already in use (in place of two overloaded main transformers

Since 1974 the transformers have seen relatively little action. Nevertheless today they are at the end of their service life. In the early stages of their operation, the windings were subjected to loads (resulting from unscheduled switching and numerous earth faults and short circuits) of a total magnitude that they would normally have encountered over a period of 30 years. The old windings are therefore being replaced by new ones from the Nuremberg factory, so that the transformers can return to reliable service.

Enfield trading software

Alstom has been chosen by the UK’s Enfield Energy Centre to supply its e-terragenesisplus trading and asset data management system. The generator, based in Enfield, near London, UK, operates a 396 MW combined cycle gas turbine plant selling energy into the UK’s wholesale power market.

The system, supplied by Alstom’s Transmission and Distribution Sector, will carry out all functions required for UK trading. This will consist of managing commercial asset data, submitting contract notifications, checking the forward contract reports, generating and submitting physical notifications and balancing mechanism bids and offers, monitoring balancing mechanism activity and checking settlement payments.

The contract was made after Enfield Energy was invited to see a demonstration of the product at Alstom’s customer sites.

RB211 reaches milestone

Rolls-Royce RB211 gas turbines designed for low exhaust emissions have passed the one million hours of operation mark in the oil and gas and power generation industries.

The RB211s emit low levels of NOx and carbon monoxide with no compromise in performance or reliability. The Rolls-Royce dry low emissions system is unique for an aero-derivative gas turbine in that it is of robust, external cannular configuration which enables easy maintenance, or replacement of components without the need to remove the engine.


The RB211 aeroderivative turbine emits low levels of NOx and CO
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Growing ecological concern worldwide has brought the introduction of increasingly stringent legislation aimed at reducing emissions from gas turbine driven equipment.

Wireless solutions

Sequoia Wireless is to create integrated solutions to provide wireless technologies, such as telemetry and remote monitoring, to utilities.

Core competencies include using GSM and GPRS standard to transmit voice, data, short message services and faxes via the same cellular networks used for mobile phones. GSM and GPRS are used to transmit data from the field back to base and vice versa, such as communicating measurements from sensors to control equipment.

Clyde points the way to savings

By reducing the level of unburnt carbon in ash by one per cent and thereby increasing combustion efficiency, it is estimated that a typical 2000 MWe fossil fuel burning power station can achieve savings of around £400 000 ($623 000) per annum.

To make such savings, UK based ash handling specialist, Clyde Bergemann Materials Handling Limited, has developed an automatic on-line ash monitoring system called Sekam.


Sekam is designed to be located as close as possible to the boiler flue duct
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Apart from the obvious economic benefits, such a system also helps to satisfy demands from legislative and environmental lobbies for reduced stack emissions and boiler optimisation.

Sekam is designed to be located as close as possible to the boiler flue duct. Sample probes draw flue gases from the duct to a cyclone within the unit where fly ash is disentrained prior to delivery to a measurement cell. Electrodes then measure the electrical capacitance of the sample and feed the information to a PLC where it is translated into a carbon value. This information is transmitted to the boiler control room where carbon levels can be monitored and boiler adjustments be made to ensure efficient combustion is maintained.

This immediacy of information also has further benefits in that it allows control room staff to divert fly ash with high carbon levels to a reject silo, thus helping to maintain the integrity of ash destined for resale.

GE Digital Energy launches Signature UPS

GE Digital Energy, a unit of General Electric Company and provider of critical power products and services to the digital marketplace, has launched the Signature 5000 Series, a line of Uninterrupted Power Supply (UPS) systems for the US market.

The first phase of the Signature launch will be for products ranging from 10 kVA to 150 kVA. Additional products within the Signature Series will be introduced globally in 2003.

The Signature 5000 Series operates in double conversion mode, with on-line voltage and frequency independent operation. Based on the performance of the new UPS, validated through testing on GE medical equipment, GE Digital Energy was selected by GE Medical Systems, as a preferred supplier for UPS products to meet the critical power needs of its medical imaging equipment.

“The Signature product family will offer GE Medical Systems and its customers a cost-effective solution with reduced lifecycle costs and a reduced footprint,” said John Chiminski, vice president, US Service for GE Medical Systems.