Direct current compensation for transformers

Siemens installs an improved Direct Current Compensation (DCC) system for transformers. Direct current in transformers leads to increased noise levels and high no-load losses. In order to counteract these problems, Siemens has developed a system for direct current compensation. An improved system has now been installed at Austrian network operator Austrian Power Grid (APG).  

Transformers and direct current

Transformers generally operate on alternating current. However, factors such as wind and solar power, trains and industrial applications can all lead to an increase in the amount of direct current in the grid. Once this direct current is fed into the transformer, it leads to increased no-load losses and increased noise levels. When purchasing transformers, network operators are paying increasingly close attention to ensuring that the transformer emits a minimum of noise, so as not to disturb residents in the vicinity. However, all these efforts can be rendered void due to the presence of direct current. 


Network operator, Austrian Power Grid (APG) has been deploying Siemens transformers with direct current compensation since 2014. As a result of the extremely positive customer experience, APG has shown great interest in further developments in this technology which are now possible.

Direct current compensation system

In order to counteract the effects of direct current on transformers, a few years ago Siemens developed a system for direct current compensation. The advantage of this system is that it does not remove direct current from the transformer. Instead, it nullifies the effects on the transformer without influencing the grid. 


The coming generation of direct current compensation was fitted to a transformer bank at the St. Peter substation as a trial. The operation in a bank setup provides feedback on the direct current load of the individual phases and in so doing offers a better insight into varying direct current loads present in the system at different times throughout the day. 


The trial run of the further-developed system began in April 2018 and concluded successfully with great satisfaction all round. After this promising test, another round of successful cooperation between Siemens and APG should now follow. In the future, the ambition is to analyze direct current load more precisely together, so that the system might be developed even further.

Improved network access

The Direct Current Compensation (DCC) system is part of the Siemens Transformers Pretact® concept. This system improves network accessibility by eliminating the negative effects of direct current. For example, noise is lessened and no-load losses are reduced. The feed in of renewables now no longer presents an obstacle.  


‘’Our innovative Direct Current Compensation system enables customers to mitigate challenges from the 

volatile energy landscape’’, comments Dr. Beatrix Natter, CEO of Siemens Transmission Products.

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