Oil-Filled Solution for GE’s 3X Turbine

By Elisa Zambrano

Product Manager

Prolec GE Industrial & Renewable Division

Wind energy production has grown exponentially during the past decade, mainly due to public and private sustainability goals as well and the great performance this clean energy production method has displayed.

The Doubly-Fed Inductor Generator (DFIG) has been a popular design for wind turbines and is currently the dominant model in the market. In this technology, the power electronic interface controls the rotor currents to achieve the variable speed necessary for maximum energy capture in variable winds, making the power production more efficient.

This type of configuration usually requires two separate transformers. A large one that steps-up the output voltage from the generator stator, commonly to 34.5kV, and connects the turbine with the windfarm’s grid, for further transmission. The second step-up transformer connects the grid side of the back-to-back converter which in turn is connected to the generator rotor winding via slip rings, to the stator circuit.

This transformer design for GE’s 3MW platform can do both voltage conversions in one single equipment, reducing the project’s capex as well as the overall maintenance cost and time.

We design our scope to match GE’s 3X turbine platform, to comply with GE’s Oil-filled transformer spec. The available options are the following:

3380kVA Transformer, for 2.5 – 2.85 MW rated power turbine

3535kVA Transformer, for 3.2 MW rated power turbine

4300kVA Transformer, for 3.4-3.6 MW rated power turbine

4779kVA Transformer, for 3.8 MW rated power turbine

2Oil-Filled Solution for GE’s 3X Turbine.

These capacities are design to cover the stator output as well as the controller’s input. For instance, the 3380kVA transformer has a 3000kVA capacity for the stator connection and 380kVA available for the rotor.

The HV is design to be connected to a 34.kV network in a Delta configuration, while the stator is connected al 6kV with a Grounded Wye and the controller at 690V also with a Grounded Wye.

These transformers are an oil-filled solution that are designed to be place outside of the turbine’s tower, thus, eliminating any potential internal fire hazard. Additionally, also making maintenance access easier as there is no need for personnel to enter the tower.

Each transformer has its own internal HV fusing protection as well as HV disconnect switch, eliminating the need for a switchgear. We also have available LV fusing protection if needed, as well as surge arrestors for the 6kV side.

For monitoring the unit, we can additionally supply bushing CTs that can connect to a Scada system or any other monitoring platform.

We supply the unit with an external accessory box so that maintenance personnel can access the temperature, oil and pressure gauges, as well as the disconnect HV switch without having to access the energized LV compartment, eliminating risk for arc flash. This also enables the user to monitor the gauge levels without having to de-energize the unit.

Our design uses aluminum windings to ensure a competitive solution, while still complying with a maximum value for load losses. Furthermore, we built our cores with high permeability grain-oriented silicon steel to guarantee low levels of no-load losses, increasing the overall system’s efficiency.

We believe this solution where we integrate two transformers in a single unit will further boost DFIG technology and we will see a shift to this multi-port configuration in the years to come.

In Prolec GE we are proud to continue adapting our transformer technologies to match with the growing market’s needs and supporting the expansion of clean renewable sources of energy.

3Oil-Filled Solution for GE’s 3X Turbine.

Elisa Zambrano Product Manager Prolec GE Industrial & Renewable Division

prolecge.com