26-04-2012, 12:52 PM
POWERFORMER
powerformer.doc (Size: 196.5 KB / Downloads: 146)
INTRODUCTION:
The power grid with voltages up to 800 KV can not be directly supplied by today’s high voltage generators, a reason why large power plants nowadays are using power step-up transformers in order to transform their generated voltage to a higher voltage level suitable for the interface with the transmission grid. The great drawbacks are imposed by the use of step up transformer on the power plant as a whole, starting from reduction in efficiency, high maintenance costs, and more space, less availability and not to forget the increased environmental impact of the plant. During the last century, a number of attempts were made at developing a high-voltage generator that could be connected directly to the power grid, i.e. without going via the step-up transformer. However, although grid voltages can reach 800 kV or more, generators are presently constructed for voltages up to 30 kV only, as stated above.
ABB has developed in close co-operation with Vattenfall (the Swedish state-owned power utility) a new high-voltage generator with innovative features that enables it to be connected directly to the transmission grid; its output voltage can reach levels up to 400 kV. With the new technology, future transformer-less power plants can be constructed leading to a new concept of energy systems. The new machine has been named Powerformer; its benefits such as higher efficiency, better availability, lower maintenance costs and reduced environmental impact are straightforward consequences of transformer-less power plants.
POWERFORMER CONCEPT: -
Powerformer, although a new machine, it is a 3-phase AC generator with a rotor of conventional design. The difference compared with conventional generator lies in the stator windings. In Powerformer stator winding consists of high-voltage cables instead of today’s windings with a square cross-section. By using high-voltage cables as generator stator winding, it is possible to highly increase the generated voltage. The decisive difference between this design and present-day technology is that Powerformer allows direct connection to the high-voltage grid.
INNOVATIVE DESIGN:
Powerformer has been designed with several unique features that allow it to exceed the 30Kv limit, including a winding consisting of power cables and an innovative stator design.
Powerformer windings
The magnetic circuit of Powerformer makes certain demands on the winding. The winding consists of a power cable with solid insulation and two semi conducting layers, one surrounds the conductor and the other outside the insulation, the semi conducting layers serves as an equi-potential surface that forces the electric field to be uniform around the circumference