Modelling transformers for high-voltage power distribution

Paul Boughton

Dr Beriz Bakija discusses the benefits of modelling, designing and testing transformers.

Transformers are used for the transport of energy from power plants to consumers all over the world. Siemens AG offers tailored solutions which it develops and manufactures in the form of high- and medium-voltage switchgear, transformers and substations, automated power supply networks and service infrastructures.

Modelling transformers for high-voltage power distribution is a complex task. Every location has different characteristics, the transformer types differ, every system has different dimensions, the operational voltage ranges change and Siemens delivers systems which include ac transformers to 1000KV and high-voltage dc transformers to 800KV.

Siemens AG's Energy Sector, particularly its Power Transmission and Distribution division uses Electro, an electric field simulator from Integrated Engineering Software, as an every-day tool to assist in transformer design and test.

I support around 20 specialists at the Technology and Innovation Department of the Transformer Section for power transmission in Nuremberg.

We develop the design-rules used by all 20 of our transformer manufacturing plants. We are also responsible for producing new solutions which analyse new designs and insulation systems and also discover why failures occur at the test stage.The Technology and Innovation team provides an important mixture of R&D support services plus the monitoring and improving of the manufacturing process of existing models.

Electro is the only software tool we have in every-day use for field calculations. It is important to have software that is very quick and easy to learn and this product is more than capable of handling the large models we require.

Four years ago Siemens standardised on Electro as a design tool for everyday calculation of electrostatic or quasi-static fields calculations in the design of its transformers.

The software was originally introduced almost 10 years ago in the Nuremberg development centre. Worldwide use by the company has increased in the last two years so that every design is routinely checked using Electro. There's no day that I don't open Electro at some stage to work on a transformer design.

Normally we use Electro for 2D calculation - focussing on rotational symmetry - because the insulation systems are all generally symmetrical. But, where there are non-symmetrical sections, where leads break-out from windings for example, we use cuts through the transformer and model those aspects separately using other 2D calculations in Electro."

In most models the calculations are of the electrostatic fields, ie calculations are based on electrostatic permittivity (permittivity or dielectric constant of a material is an important property of materials from the electrical engineering perspective). Quasi-static calculation is considered too, with the conductivity material as the default.

As it is a fairly specialised product, Siemens makes full use of Electro and has been involved in developing enhancements to the software in association with Integrated to enhance it to Siemens' purposes.

Routinely at Siemens there are as many as 30 licences in use regularly through the world with a user-base of about 60 engineers worldwide. We have an excellent relationship and have worked with Integrated with the data-output formatting from Electro so the output files are generated in a form which is readily accepted by our own in-house design-rule checking software.

Dr Beriz Bakija is a power transmission technology and innovation engineer at Siemens, Nuremberg, Germany. www.energy.siemens.com/energy/en; www.integratedsoft.com/products/electro.aspx

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