Who needs a transformer?

Taking a leap into the next century, ABB has launched the world’s first high voltage (HV) generator, which eliminates the need for transformers so that electricity can now be supplied directly to a high voltage network. Powerformer, as the new innovation is known, will have far-reaching implications for the entire electricity industry. Described as an ‘epoch-making invention’ and a revolutionary breakthrough, the first prototype of Powerformer will be installed at the Porjus hydro power plant in Sweden.

Located on the Lule river in northern Sweden, there is more to Porjus than meets the eye. Owned and operated by the Porjus Hydro Power Centre Foundation, part of the power station serves as a development and training facility for hydro power technology. With a reputation of being a leader in research and development (R&D), the foundation is sponsored by Swedish power utility Vattenfall, ABB and Kværner Turbin.

Upon reflection, there should be little surprise that such a partnership between Porjus (a centre dedicated to new technology) and ABB (which prides itself on its ‘bold, aggressive and targeted R&D’), has made what the latter calls the biggest step forward the electricity industry has taken since the creation of three-phase technology late in the 1800s.

Furthermore, hydro power is leading the advance: ‘We have created the next generation of hydro power plants,’ Kjell Isaksson, chairman of the Porjus Foundation, said. ‘From an international perspective I believe that this will attract a lot of attention,’ he added.

Speaking for ABB, Marcus Bayegan agrees: ‘We have started with hydro power,’ he said, ‘and we will change the rules of the power generation game.’ There are two plants belonging to Vattenfall at Porjus. The old plant, built in 1910-14, was taken out of operation in 1989 and replaced by a newer plant. In addition, the older facility was turned into a museum and, on establishment of the Porjus Hydro Power Centre Foundation in 1994, the decision was taken to replace two of its units and use them for development of hydro technology.

The mission of the Porjus centre is to become a world leader in training and in the development of environmentally friendly and energy efficient hydro power systems. Those committed to R&D at Porjus knew from the beginning that they wanted to have something ‘new’ to boast about. Not quite sure what this would be, the foundation based its R&D work on improving efficiencies and reducing the costs of hydro plants. The aims are to: •Improve the efficiencies of new and refurbished hydro plants by 1%.

•Decrease investment costs by 10%.

•Reduce maintenance and operational costs by 10%.

The two generating units are the focal points of the old Porjus plant. One, utilising a Francis runner and equipped with complete electrical and control units, is used for training and has been in commercial operation since March 1997. The second unit, with a Kaplan runner, is to be used for R&D.

In 1995 the foundation was ready to choose generators for installation at the R&D plant, and by this time ABB realised that its high voltage generator was advanced to a stage where it could contribute to Porjus’ R&D goals. ‘When we created the foundation we knew nothing about the creation of the HV generator,’ Isaksson explained, ‘Although we now know that in some respects the Porjus centre helped to speed up development of the Powerformer.’ Furthermore, he believes that the HV generator will probably help to exceed the foundation’s R&D goals.

For the past seven years, the development of the HV generator has been the task of Mats Leijon at ABB Corporate Research in Sweden. The product has undergone numerous workshop tests and in May will be commissioned at the old Porjus plant, ready for commercial operation on 10 June. Convinced that his idea will change the face of the energy market, Leijon says that in principle the generator is very simple but, he laughs wryly, it has taken almost a century to implement.

The main development in the high voltage generator is that round, high-voltage cables have replaced the complex structure of square insulated copper conductors which form the stator winding of a conventional generator. The reason behind this conventional square shape can be traced back in history: when power demands on generators increased in the 1900s, engineers were not able to increase the output voltage due to the poor insulation material available at the time. Instead they had to increase the current in the generators, and it was maximised by making conductors square.

By the laws of electric fields, distribution around a square conductor is very uneven, with severe concentrations at the corners; this increases the risk of insulation breakdown and consequent short circuits. Indeed, such high field concentrations have, even when the insulation technology developed, limited the maximum output voltage from generators.

For a round conductor, however, field distribution is very smooth with no extreme concentrations. As a result the insulation material is uniformly loaded and not stressed as before.

Ideal candidate

ABB realised that an ideal candidate for such a conductor was a high voltage cable and now, with Powerformer, the output voltage is only limited by the availability of cable technology (cable with the right type of insulation is presently available up to 400kV). Consequently, electricity can be generated at the required transmission voltage level, eliminating the need for transformers and allowing a direct connection to the power grid.

‘The idea to work with round cables to optimise voltage is not new,’ says Thommy Karlsson, project manager of the HV generator at ABB, ‘but the cable insulation technology in the early 1900s was so poor it was impossible to apply it.’ Since then, cable insulation technology has improved dramatically and today’s cables are suitable as windings for high voltage electric machines.

However, Karlsson adds, it has not just been advances in materials technology (with the new XLPE-insulated power cable) which has made the generator possible – it is a concept which focuses on a complete new energy system. At Porjus, Powerformer will be the world’s highest voltage generator in commercial operation (at 45kV) and, ABB’s Marcus Bayegan points out, is worthy of a place in The Guinness Book of Records.

The elimination of transformers in the ‘conservative’ electricity industry may be quite a step – but what are the implications for the operators of hydro power plants? Karlsson explained that there will be: •Improved efficiency, due to the direct grid connection and the fact that there are no losses via the transformer.

•New power plant design – as the transformer is no longer needed, it will lead to a substantial reduction in components associated with the generator (such as switch gear and busducts). This means that less space will be needed at the plant – an idea welcomed by hydro developers with underground power houses located in confined spaces. ABB also points out that this is one of those rare occasions where technological advances have created a simpler plant in the power system.

•Lower maintenance costs – fewer components will need less maintenance.

•Environmental advantages. The increased efficiency of the generator may improve the plant’s ‘green’ appeal. The elimination of the transformer also means elimination of the transformer oil, and the problems associated with disposing of it. Described as being ‘superior’ in the recycling stage, after decommissioning of the HV machine much of the material can be recycled.

Ultimately, when discussing the HV generator, ABB is confident about its success – the company has applied for over 200 patents for the product – and one can almost see the dollar signs gleaming in employees’ eyes. ‘We can smell the money,’ ABB’s Bayegan said when commenting on the estimated revenue impact of the product. (A ‘conservative’ figure of US$400M has been given by ABB for its projected sales over the next four to five years).

Although initially Powerformer will cost more than conventional generators, it will decrease life cycle costs by 30% (taking into account the cost of building more compact plant, and reducing losses and maintenance). The implications of such cost savings are impressive. If Porjus’ R&D goals are achieved by the Powerformer, for the entire installed hydro power generating capacity in Sweden, savings of US$250M could be made over a 30-year period. ‘This indicates what economic values are at stake,’ Isaksson commented.

Isaksson sees hydro plant operators with ageing generators as being among the first customers to purchase the HV generator. Those with 40-50-year-old generating units will be particularly interested. Utilities need an upgrading technology for the refurbishment and building of new machines, he explained, and this new product is one way to respond to a need for more efficient operation and maintenance.

When the 10.2MW Powerformer prototype swings into full operation, connected to the 45kV commercial power grid in Sweden, a ‘working demonstration’ of the HV generator will be visible for everyone to see. Powerformer can be used for all types of power plants but, Isaksson admits, the installation of the first prototype at Porjus is quite a step for hydro power.

Looking to the future, ABB and Vattenfall are confident that the high voltage 45kV generator ‘is not very high compared with what can be done’ – there is a possibility that a 145kV generator can be manufactured in 1999. Both companies are also working together looking at the applications for Powerformer in two other Vattenfall plants in Sweden.

Furthermore, Isaksson believes that Powerformer will enhance Swedish hydro’s international competitiveness in the power industry. ‘Things are just starting to happen,’ he said.