Pnc&viet

Power requirement is increasing day by day due to the maximum power utilization. In order to meet this demand a large power has to be generated in an efficient way. A new machine namely “Powerformer” can do this. The conventional plant generated voltage is limited to 30KV. This voltage is stepped up to a high voltage level in the order of 800KV with the help of power step-up transformers. The step-up transformer imposes great drawbacks on the power plant, starting from reduction in efficiency, high maintenance costs, and more space less availability.

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 any step-up transformer. The powerformer has opened a new chapter in the generation and transmission of electrical energy.

Powerformer Concept Innovative Design The first Powerformer Installation Advantages of Powerformer

Powerformer is 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.

1. Generator 2. Generator circuit breaker

3. Surge arrester 4. step-up transformer

5. Line circuit breaker

This design implies the omission of the generator circuit breaker, the high current bus bar and the step-up power transformer from the power plant, because Powerformer comprises the functions of both generator and step-up transformer as realized from above Figure

As a consequence there is an increase up to 1.5% in total electric power efficiency compared with today’s best designs, without using superconductive materials.

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.

The winding consists of a power cable with solid insulation and two semiconducting layers, one surrounds the conductor and the other outside the insulation.

The insulation material is cross-linked polyethylene

High-voltage power cables are used in winding. These cables used to many advantages over

conventional designs

The stator of Powerformer consists of a laminated core.

These laminated core are built up from electrical sheet.

The winding is located in the slots formed by the teeth, the cross section of the slots decreases . The winding turn requires less cable insulation the closer it is to the rotor.

Each slot has circular bores at intervals, forming narrow waists between the winding layers, as shown in Figure below.

The world’s first high-voltage generator based on the new technology; a hydropower machine is rated at 11 MVA, 45 kV, and 600 rpm. The machine has already been tested in the factory and installed at the Porjus Hydropower Center on the Lule River in northern Sweden. The machine is directly connected to the 45 kV transmission power grids; its stator is shown in below Figure

1.It generates Low voltage (<30kv)

1.It generates High voltage (>>30kV)

2. High current 2. Low current

3. Stator has Short teeth 3. Stator Long teeth

4. High weight 4. Less weight

5. Mount winding is used 5. Thread cable is used

6. Impregnating windings 6. Extrusion type winding is used

7. High temperature 7. Low temperature

higher efficiency

low maintenance costs

power transfer form generator to power grid without going via the step-up transformer

better availabil i ty

ABB’s new high-voltage generator (Powerformer) has been studied the new concept provides the possibility to directly connect a rotating machine to the high-voltage power grid without going any step-up transformer. Powerformer is a high-voltage generator; the limitation in its rated voltage is set solely by the AC

Power cable and the cable accessories (terminations and joints) used in its stator winding. This means that Powerformer of voltage ratings up to 400 kV can be realized, although has not been proved yet.