The power transformer is one of the main elements of the existing system of power supply and distribution of electrical energy. The reliability of a transformer is largely determined by its ability to withstand the electrodynamic effects arising from short circuits.
The most reliable way to check the resistance to short-circuit currents are transformer tests. Therefore, in accordance with GOST R 52719, the resistance of transformers in case of short-circuit should be confirmed by mandatory electrodynamic tests for all transformers up to 40 MVA inclusive. In addition, when conducting certification of purchased equipment, Federal Grid Company focuses on the mandatory compliance with the requirements of GOST in terms of the resistance of transformers to short-circuit currents, which obliges manufacturers to conduct tests.
However, the situation with tests for resistance to short circuits in Russia (and CIS countries) is critical. In recent decades, the volume of tests for durability at short circuit of power transformers has repeatedly decreased, the reason for this is the actual absence of operating test benches in Russia. Previously existing test benches of FSUE VEI, SIC VVA (Moscow), MIS (Tolyatti), UETM (Yekaterinburg) and others, have either completely ceased to exist or have significantly reduced their test capabilities. due to obsolescence of existing equipment.
The only way out of the current situation is to conduct tests at foreign stands located in the Czech Republic, Holland, India, South Korea and other countries of Europe and Asia. Tests are expensive, and the cost of a mistake is very high, so for each manufacturer, conducting such a "crash test" of the equipment being produced is a significant event.
Elmash (UETM), which has a well-deserved authority in the field of transformer engineering, and, in particular, in matters of ensuring electrodynamic resistance, selected the most powerful power transformer of the type TDTN-40000 as the test object as required by GOST R 52719 / 110. The specificity of this type of equipment is the presence of three-winding short circuit modes. They are characterized by the maximum values of currents in the windings and the critical forces acting on the structural elements. Such modes are standardized in GOST R 52719, but are absent in international standards, for example, IEC 60076-5. Therefore, the IEC requirements are less stringent than the domestic standard, and often the designs of foreign manufacturers do not take into account the specifics of the three-winding modes, which are characteristic of a powerful and extensive Russian power system.
When designing, the calculation method was used on the basis of RD 16.431-88, implemented in the REST program (VEI), and operating stations. In the process of testing, the reliability of new design solutions and modern materials currently used in our enterprise was also checked.
As practice shows, tests, not only the correct calculation and new design solutions are the key to creating a reliable product. Other essential components are technology compliance and quality production. The test result confirmed that the technologies used in the transformer production of Elmash LLC (UETM) provide the required high quality of the products. Specialists of the control center TR and OGK SRW were monitored at each and every production stage: from stamping winding gaskets to winding nozzles and thermal vacuum treatment of the active part.
After production and preliminary testing, the transformer was sent to the KEMA test facility located in Prague, Czech Republic. This stand has a well-deserved authority worldwide. The installation and direct tests of the transformer TDTN-40000/110 were carried out according to the program set up in accordance with GOST 20243, where 15 valid experiments were registered, including 5 of them in the three-winding mode with the maximum possible short-circuit currents.
Further, the transformer, according to the existing procedure, was sent back to the plant, where it was disassembled for examination and issuing a final conclusion. Specialists from the KEMA testing laboratory arrived at the plant for inspection, and according to the results of tests and thorough inspections they confidently stated that there was no damage and that the transformer was fully operational. On the fact of the inspection, the KEMA experts congratulated the factory workers on the successful completion of the test procedure, and also noted the reliability of the design and the build quality in general.
The positive test results of the TDTN-40000/110 type three-winding transformer further allowed our company to continue the certification procedure for the possibility of receiving orders for the supply of equipment for such large organizations as Rosseti PJSC, AK Transneft, Gazprom.
At this, work in this direction does not stop, ahead of new tests of transformers with reduced weight and size parameters, which once again must demonstrate the reliability of the design and build quality of transformer-reactor equipment manufactured by Elmash (UETM)!
Dmitry Kiselev, head of design and project group of oil transformers
