On November 27, 2022, the first domestic converter transformer tap-changer equipped in ±500kV converter transformer was successfully put into operation at Xiluodu DC project from the west converter station. The on-load tap-changer 'neck' problem of the converter transformer was successfully solved.
Huaming SHZVⅡ-1300/72.5D-14271W current transformer on-load tap-changer adopts Chinese vacuum interrupter for the first time, with an electrical life of 300,000 times and a mechanical life of 1.5 million times. At the same time, it is also the first time to adopt the Chinese on-load tap-changer online monitoring system with oil chromatography monitoring and other functions developed by Huaming, which protects the operation of the product.
As the core component of the power transformer, the 'heart' of the power grid, the on-load tap-changer plays an important role in regulating voltage, current and load during the power transmission process, and its safety and reliability requirements are extremely high. The on-load tap-changer technology used in UHV DC converter transformers has always been in the hands of foreign companies, which poses a challenge to the safety of power operation due to limited equipment maintenance and long product maintenance and replacement cycles.
For this reason, Huaming and China Southern Power Grid Co., Ltd. jointly developed the SHZV II on-load tap-changer based on Huaming SHZV type vacuum on-load tap-changer and combined with the application requirements of on-load tap-changer for converter transformers. The switch not only passed all tests, but also made up for the design defects of foreign products.
In April 2022, with the support of Xi'an Xidian Transformer Co., Ltd, the SHZV II converter vacuum on-load tap-changer passed the rigorous collaborative test, and in November 2022, the installation and commissioning of the converter transformer was completed, and the transformer was finally put into operation at the west converter station.
Technical breakthroughs:
-- The vacuum type on-load tap-changer for converter transformers is a two-phase 180 degree symmetrical arrangement, which is suitable for the converter transformer coil arrangement structure and effectively improves the insulation margin inside the tap-changer.
-- The two reversing switches are also equipped with arc extinguishing capability. In case of vacuum tube failure, the reversing switch can complete the transition switching and protect the alarm via relay to avoid accident expansion.
-- Reducing the current density of the transition resistor, i.e. increasing the volume of the resistor, improves the high temperature in the on-load tap-changer oil compartment caused by frequent switching.
-- For the first time, a tap selector with insulation class E has been developed, and the distance between the fixed contacts has been increased to achieve an increase in the internal insulation class.
