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

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.

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.