Huaming CHVT converter transformer on-load tap-changer successfully commissioned at Longdong ±800kV HVDC converter station in China

Ultra-High Voltage Product Successfully Integrated into the Grid: A Historic Breakthrough

Recently, the CHVT converter transformer on-load tap-changers, co-developed by Huaming Power Equipment, was officially put into batch operation in China’s first large-scale integrated energy transmission project combining wind, solar, thermal, and storage —  the ±800kV Ultra-High Voltage Direct Current (UHVDC) Transmission Project, from Longdong to Shandong.

The on-load tap-changer is a high-precision electromechanical device located inside the converter transformer. As the only moving component during tap transitions, it must complete eight mechanical actions in sequence within 100 milliseconds during each changeover, This places extremely high demands on timing accuracy, spatial precision, sequence stability and switching reliability. The successful commissioning of this project demonstrates Huaming’s strong technical capabilities in delivering stable and reliable high-end products.

Longdong Converter Station

Committed to Innovation and Breakthroughs, Surpassing Key Performance Benchmarks

Since 2021, Huaming has been actively involved  in the R&D and manufacturing of tap-changers for converter transformers. Through strong support and close collaboration from all stakeholders, the group successfully developed a Triple-Vacuum Quasi-Symmetric Topology Structure design.

It is worth noting that, in response to common industry challenges such as insufficient insulation margins and  gas generation due to selector polarity reversal in similar products, Huaming leveraged over 30 years of R&D and manufacturing expertise in tap-changer technology. Building on the achievements of joint development efforts,  the company developed a modular switching device featuring a current-carrying capacity of 1,500A (three-phase), internal insulation withstand voltage of 40kV, and integrated fast-acting switches with potential-sensing tap selectors. Through systematic design optimization, Huaming has significantly enhanced product’s reliability and safety — achieving a comprehensive breakthrough in key performance metrics.

CHVT tap-changer core assembly

Craftsmanship and Precision Engineering Forge Exceptional Quality

To ensure consistency and high reliability between prototype testing and subsequent mass production, the company adopted a systematic organizational framework and end-to-end process control. Under the direct leadership of the Chairman, a cross-functional task force was formed to oversee the entire workflow — from raw material selection, parts inspection, precision machining, assembly verification testing, to packaging and transportation. More than 20 enterprise standards specific to ultra-high voltage products were formulated to govern these processes.

During the prototype development phase, to ensure testing and R&D progress,  the company dedicated 20 sets of critical components and over 300 sets of customized tooling molds. More than 1,500 technical documents and work instructions were meticulously compiled. Each document and every mold embodies the ingenuity and dedication of Huaming's engineers, reflecting the company’s unwavering commitment to quality excellence.

Huaming Production Workshop for  Converter Transformer Tap-changers

Validation through Rigorous Testing Highlights Exceptional Performance

True capability must withstand the most rigorous tests.

In early March 2023, the first CHVT prototype successfully completed a series of tests according to standard specifications, including 360,000 switching cycles, 1.5 million mechanical endurance cycles, and low-temperature operation tests at -35°C.

In May of the same year, a second CHVT unit again passed the 360,000 switching cycles and 1.5 million mechanical endurance tests. It also successfully completed, for the first time in history, a -25°C low-temperature load-switching test,  exceeding standard requirements, and fully demonstrating its exceptional performance under extreme operating conditions.

After completing the tests, the Huaming team conducted a comprehensive analysis of the test data, optimizing the structure and manufacturing processes of  20 critical product details. This relentless pursuit of perfection ensures the high -reliability delivery of the subsequent seven units.

Product Testing Site

Commissioning and Shining in Longdong, Ushering in a New Chapter

After rigorous trials and refinements, the moment of glory has arrived.

In March 2024, the first Huaming CHVT tap-changer integrated with a converter transformer and successfully passed on-site witnessed tests by expert panels.

In July 2024, the CHVT tap-changer, installed on the first converter transformer, was successfully delivered to the Longdong ±800kV Converter Station. Huaming dispatched a dedicated and professional technical team to oversee the entire installation process, ensuring an efficient and seamless deployment.

In May 2025, following comprehensive system debugging, the first batch of converter transformers equipped with CHVT on-load tap-changers successfully complete system commissioning and officially went into operation at the Longdong ±800kV Converter Station. All performance metrics were excellent, and the units have been operating in optimal condition!

Operation of the CHVT Tap-Changer at the Longdong ±800kV UHVDC Converter Station

Since the company’s first Ultra-High Voltage on-load tap-changer passed technical certification and received industry accolades in 2014, to the recent batch commissioning of UHV converter transformers, we have journeyed through 11 years of relentless dedication. With unwavering focus and patience, Huaming’s team has advanced step by step—driven by effort and perseverance, professionalism and dedication, courage and wisdom—to deliver an outstanding achievement. We remain undeterred by challenges, steadfast in fulfilling our mission, and refuse to rest on our laurels. This marks a new starting point for Huaming as we strive for even greater heights.

The successful large-scale application of Huaming’s CHVT on-load tap-changers in Ultra-High Voltage  projects is a testament to the collaborative efforts and innovation of global partners. This achievement unequivocally demonstrates that China’s high-end power equipment, through independent R&D and design, has reached internationally leading standards in critical performance metrics, offering the global UHV engineering sector a groundbreaking alternative.

As one of the world’s leading tap-changer manufacturers, Huaming is committed to collaborating with partners worldwide to explore advanced technological solutions for power sectors. Through innovative products, we aim to support the development of a more resilient and sustainable global energy network. We firmly believe that true technological breakthroughs should serve the future of humanity’s energy needs. Guided by our principle that “Innovation Knows No Borders”, we will continue to drive the application of advanced technologies through continuous technological iteration and deep international collaboration—empowering global energy transformation with cutting-edge power equipment proudly originating from China.