Recently, at the annual maintenance and overhaul site of Unit 16 at the Three Gorges Hydropower Plant, a generator rotor weighing over 1,600 tons was smoothly hoisted under the traction of an overhead crane. A laser tracker, like an "eye of wisdom", captured minor deviations of the rotor during hoisting in real time, providing "precision navigation" for the entire lifting process.

This scene epitomizes the in-depth application of laser technology during annual maintenance and overhaul on the world's largest clean energy corridor. From precision measurement during equipment installation to real-time dynamic monitoring of large component hoisting, and then to precision repair of critical equipment, laser technology has been applied in the entire maintenance workflow with its advantages of high precision, high efficiency, and non-contact operation. This "light" of technological innovation is injecting new momentum into this massive and complex maintenance system project.

Using laser as a ruler: transforming "craft" into "data streams"

"Wherever there's maintenance, measurement is inevitably involved. Measurement forms the cornerstone of units' maintenance quality, and measurement data directly influences the formulation of maintenance plans," stated WU Tao, Director of the Mechanical Maintenance Department at CYPC Overhaul and Maintenance Factory, highlighting the core role of measurement in maintenance.

Traditional measurement methods are undergoing a baptism of technological transformation. Inspecting wear on the inner wall of a unit's servomotor piston cylinder was once a "craft" reliant on touch and experience, requiring measurements with an inside micrometer to assess equipment wear. Now, empowered by 3D laser scanning technology, engineers can rapidly perform non-contact surface scans, obtaining complete 3D data with an accuracy of ±0.02 mm. Equipment wear conditions can be intuitively presented through quantified models.

The application of laser trackers has similarly brought leaps in efficiency and accuracy for measuring the roundness of rotors—the core components of generators. Previous roundness measurement methods require installing a specialized rotor roundness measuring device at the rotor hub, which was not only cumbersome but also time-consuming to assemble. Now, laser trackers, by installing target spheres on rotor magnetic poles, receive and feedback laser signals in real time, enabling the rapid generation of complete spatial position parameters for the rotor poles. According to LIU Hongju, Director of Mechanical Division II of the Mechanical Maintenance Department at CYPC Overhaul and Maintenance Factory, this new method can reduce operation time to a quarter of the original, while simultaneously collecting massive amounts of point data, significantly enhancing measurement accuracy and efficiency.  

From "relying on touch" to "relying on data", from "point measurements" to "surface scans", from "slow work yielding fine products" to "maintaining fast, accurate, stable, and efficient," laser technology is comprehensively reshaping the operational models for maintaining power station equipment and facilities.

Precise positioning: mastering "differences of a hair's breadth"

In the complex environment of a hydropower station powerhouse, safely and precisely hoisting core components weighing thousands of tons is a critical link of unit maintenance. Laser positioning technology is precisely the core tool for mastering these "differences of a hair's breadth". 

At the site of Level-A Maintenance of Unit 16 at the Three Gorges HPP, the rotor was smoothly hoisted out, showcasing the precision lifting system's remarkable capabilities. The system's core lies in the real-time, dynamic coordinate feedback provided by the laser tracker, which determines the three-dimensional coordinates of the lifted component through three target spheres. Lifting operators can monitor minute displacements and deflections of the rotor in real time to enable dynamic adjustments, thus effectively mitigating risks arising from visual blind spots or judgment errors. This technological innovation has increased lifting efficiency by 30% and achieved a qualitative leap in safety coefficients.

"Next, we plan to systematize and standardize key elements such as lifting configurations, lifting equipment parameters, and sling selection. Facing ahead, we will also build a digital twin system to achieve lifting trajectory planning, real-time process visualization, and risk identification," said LIANG Qian, Technical Supervisor of Lifting Division of the CYPC Overhaul and Maintenance Factory.

Precise repair: laser cladding performs "minimally invasive surgery"

Beyond measurement and positioning, lasers demonstrate significant value in equipment component repair—specifically laser cladding technology—leveraging unique advantages such as high energy density, minimal heat-affected zones, and ease of control.

Laser cladding technology has been successfully applied during previous annual maintenance and overhaul. Components like hydro-turbine runner blades and head cover flow-passing surfaces, which endure long-term exposure to high-velocity water erosion in harsh environments, have consistently presented technical challenges for damage repair. Traditional electric welding repair often causes localized overheating and deformation due to high heat input. In contrast, laser cladding technology uses a high-energy laser beam to precisely coat damaged areas with a layer of high-performance alloy material, forming a robust, wear-resistant "new armor". The process exerts minimal thermal impact on the base material, effectively avoiding deformation risks associated with traditional welding and providing a novel solution for precision component repair.

The application of this technology was not achieved overnight. WU Tao recalled that it was a bold attempt when laser cladding was first used for repairing the thrust block rotating ring of units at Three Gorges HPP. Despite uncertainties, the team achieved the desired outcome through rigorous process design and thorough technical preparation. Since then, the technology has matured and been successfully applied to precise repair of critical equipment such as runner blades, runner chamber steel plates, and head covers, demonstrating its unique advantages in combating cavitation erosion for hydropower station flow-passing components. It is reported that during this year's annual maintenance and overhaul, laser cladding technology will once again be deployed for the repair of head covers on Unit 15 at Xiluodu HPP and Unit 10 at Three Gorges HPP. This is not only a reexamination of the laser cladding technology's maturity but also marks its progression from isolated successful applications toward large-scale implementation across broader contexts.

From providing "insightful vision" for measurement, embedding "intelligence" into lifting operations, to performing "dexterous hand craft" in repairs, the deep integration of laser technology in cascade hydropower plants maintenance clearly outlines a practical pathway for technological empowerment in traditional industry transformation. The innovative spirit of CYPC Overhaul and Maintenance Factory—daring to bring laboratory-developed technologies directly into real-world production settings—will propel cutting-edge scientific achievements from blueprints to field applications, evolving from pilot projects to large-scale implementation. Moving forward, with continuous technological iteration and integrated innovation, laser technology will achieve deeper "laser fusion" with traditional maintenance practices, providing critical support for ensuring the safe, stable, and efficient operation of "key national infrastructure".