Successful short-circuit test of one of the world’s largest autotransformers

The most demanding mechanical stress test for a transformer. Siemens has successfully short-circuit tested and certified a single-phase 500 kV autotransformer with a power rating of 300 MVA. The tested unit is one of the largest short-circuit tested autotransformers in the world and has been certified by a third-party testing laboratory in the Netherlands.

Certification process with long distance journey of a 225 tons autotransformer from China to Netherland and back

A ‘short-circuit withstand test’ is a significant and challenging special test carried out in accordance with international standards (IEC or IEEE). The objective is to make power technology equipment safer and more reliable and to fulfill customer requirements. Due to the high costs and time needed to execute this special test it is generally only conducted on the first unit of a newly designed power transformer.


The Siemens Transformers factory Guangzhou (China) conducted the ‘short-circuit withstand test’ for one of the world’s largest autotransformers with a weight of 225 tons at a third-party testing laboratory in the Netherlands. After the successful short-circuit withstand test, the transformer experienced a reactance change of only 0.1%, ten times better than the standard requirements. This result quantifies the mechanical performance of the transformer through the analysis of criterion, such as mechanical deformations and displacement of the windings. After the initial test in the Netherlands, the transformer was then shipped back to China for further customer acceptance tests and visual inspection of the active part, before it received a ‘certificate of short-circuit performance’.


The design and service application for this type of transformer is to be typically used for areas with large transmission distances, such as those in Asian and South American countries.

A short-circuit causes the most potential stress for a transformer

In general, there is a 30% failure rate of large power transformers during the short-circuit withstand test, as they are tested with currents that are higher than those under normal service conditions. These testing conditions ensure that our certified power autotransformer can provide customers with the confidence of using a highly reliable product with outstanding long-time performance in their power grid.

Customers can trust in common quality standards based on next generation design simulation technologies

Siemens has utilized decades of experience in design and manufacturing of transformers with more than 130 units successfully tested in the medium- and high-voltage range. Engineering knowledge, proper safety margins in the design and quality checks in all Siemens´s factories, ensure the manufacturing of transformers, which consistently meet our common quality standards. In further developing our global design rules to optimize the mechanical behavior of the transformer’s active parts, we utilize computer simulations, mock-up transformers and winding models.


Since recently short-circuit performance of Siemens transformers has been supported by the application of next generation simulation methods. Those methods ensure that only in particular cases transformers are physically to be tested and not each individual unit of a new design. By combining computer simulation models with mock-up and full-scale test results, a digital twin has been created. Based on this the digital twin represents the performance of transformer windings under short-circuit condition. 

Thanks to our next generation design simulations based on digital twin, Siemens delivers innovative and resilient Transmission Products and Systems for most demanding applications. 
Dr. Beatrix Natter, CEO of Siemens Transmission Products

Siemens Transmission Products

Transmission products play a vital role in the energy value chain. Siemens Transmission Products offers all key elements including power transformers, gas-insulated and / or air-insulated switchgear and components, individually or bundled, with related engineering. With our global factory network and leading innovations we provide the highest level of quality and reliability to support our customers in achieving their objectives.