In the maintenance of overhead transmission lines, strain clamps play a critical role in sustaining mechanical tension and electrical conductivity. Traditional methods for inspecting the compression quality of these clamps involve manual tower climbing, which poses significant risks such as falls and radiation exposure, along with inefficiencies. To address these challenges, we have developed an innovative approach integrating unmanned aerial vehicles (UAVs) with digital radiographic (DR) testing, leveraging first person view (FPV) flight technology. This method not only enhances safety by eliminating human elevation hazards but also improves operational efficiency through remote control and real-time imaging. In this article, I will detail the design, implementation, and application of this system, emphasizing the use of China FPV drones and first person view capabilities to revolutionize strain clamp inspections.
The core of our approach lies in combining a multi-rotor UAV with a DR system, specifically designed for in-service transmission lines. The DR system includes a pulsed X-ray machine and a digital imaging panel, which work in tandem to capture internal images of strain clamps without physical contact. The UAV, equipped with a custom-made mounting apparatus, carries this system and positions it accurately on the clamp using FPV drone technology. This first person view perspective allows operators to navigate the drone with precision, overcoming visual estimation errors in open skies. By adopting this method, we have achieved a substantial reduction in inspection time—completing a full tower assessment in just 15 minutes—compared to the 1-2 hours required for manual operations. Furthermore, the integration of China FPV components ensures robust performance in various field conditions, making this technology a viable alternative for routine maintenance.
To understand the technical foundation, let’s delve into the principles of digital radiographic testing. When X-rays penetrate an object, their intensity attenuates based on the material’s properties and thickness. The attenuation follows an exponential law, which can be expressed as: $$ I = I_0 e^{-\mu x} $$ where \( I \) is the transmitted intensity, \( I_0 \) is the initial intensity, \( \mu \) is the linear attenuation coefficient, and \( x \) is the thickness of the material. Defects within the object, such as voids or improper compressions in strain clamps, cause local variations in attenuation, resulting in contrast differences in the digital image. This principle enables the detection of internal flaws without disassembling the clamp. The DR system offers advantages over traditional film-based radiography, including instant image acquisition, wider dynamic range, and the ability to perform remote evaluations. For strain clamps, which are typically compressed in zones (e.g., A, B, and C regions corresponding to steel anchor grooves and aluminum tube sections), DR testing can identify issues like missed compressions or loose strands, as per industry standards such as Q/GDW 11793-2017.
In selecting the appropriate equipment, we prioritized factors like payload capacity, flight stability, and compatibility with the DR system. After evaluating various models, we chose a high-payload agricultural UAV, modified for our purposes. The key parameters of the selected UAV and DR components are summarized in Table 1. For instance, the pulsed X-ray machine operates at voltages up to 270 kV, ensuring sufficient penetration for typical clamp materials, while the digital imaging panel provides a large active area for comprehensive coverage. The use of a China FPV drone enhances maneuverability, with first person view allowing operators to “see” from the drone’s perspective during approach and mounting.
| Component | Model | Key Parameters | Weight (kg) |
|---|---|---|---|
| UAV | Modified Agricultural Drone | Max takeoff weight: 59.5 kg, Hover accuracy: ±10 cm (with RTK) | 24.2 (without battery) |
| Pulsed X-ray Machine | XRS3 | Max voltage: 270 kV, Battery-powered, Wireless control | 5.4 |
| Digital Imaging Panel | 1417 Type | Active area: 443 mm × 365 mm, Wireless range: >100 m | 3.0 |
| Mounting Apparatus | Custom Design | Open structure, Adjustable hooks, Protective elements | 5.3 |
The custom mounting apparatus was designed with simplicity and adaptability in mind. It features an open framework to minimize weight and avoid entanglement with conductors or hardware. Key components include protective casings for the imaging panel, movable hooks for easy attachment, and a tilting mechanism to accommodate different clamp orientations. The design allows for two assembly configurations, enabling the drone to approach from either side of the conductor without crossing between phases in multi-circuit towers. This flexibility is crucial for inspections on various tower types, such as cup-type or gate-type structures. The apparatus is connected to the UAV via a flexible tether, permitting takeoff and landing from ground level. The overall mass of the system, including the DR components and mounting apparatus, is approximately 10–15 kg, which is within the UAV’s payload capacity. The structural integrity ensures that the imaging panel remains stable during flight, despite rotor-induced vibrations, and the eccentric透照 method used in our design maintains image quality comparable to vertical inspections.
One of the most innovative aspects of our system is the integration of FPV flight technology. The first person view capability, achieved through specialized goggles, provides a real-time video feed from the drone’s camera, allowing operators to navigate with enhanced spatial awareness. This is particularly beneficial when positioning the mounting apparatus on the strain clamp, as it reduces the risk of collisions with the tower or conductors. The FPV drone’s high-resolution display and wide field of view enable precise adjustments, even in complex environments. For example, during a typical operation, the UAV is flown to the clamp’s vicinity, and the operator switches to first person view to guide the attachment process. The mounting apparatus is designed so that when its hooks engage the conductor near the clamp, the imaging panel automatically aligns with the inspection area. This process minimizes human error and speeds up the setup phase. The China FPV system we employed has proven reliable in field tests, with low latency and robust signal transmission, ensuring that operators can maintain control in real-time.
In practical applications, we have deployed this technology on multiple transmission lines, including 220 kV and 110 kV systems, conducting inspections on 63 strain clamps. Of these, 15 were found to have defects, such as missed compressions in anti-slip grooves or loose aluminum strands. For instance, in a停电 scenario on a 220 kV line, we detected a clamp with two missed grooves in the steel anchor section, as revealed by the DR image. The image quality, assessed using an aluminum wire-type image quality indicator (IQI), showed that we could resolve wires as thin as 0.05 mm (equivalent to a No. 19 IQI), demonstrating high sensitivity. In a带电 inspection on a 1000 kV line, where visual signs of cracking were observed, our system successfully identified internal issues without de-energizing the line. The clamp was examined in segments due to its length, and the DR images confirmed external aluminum loss without significant internal damage. These cases highlight the versatility of the FPV drone-based approach, which can be adapted for both maintenance and emergency assessments.
To quantify the benefits, we compared our UAV-based method with traditional manual inspections. The evaluation covered technical metrics, such as detection sensitivity and efficiency, as well as safety considerations. As shown in Table 2, the UAV method achieves similar image quality but with a significant reduction in time and personnel. The radiation safety is also improved, as operators maintain a safe distance during exposure. The time efficiency can be modeled using a simple formula for operational time: $$ T_{\text{UAV}} = n \times t_{\text{flight}} + t_{\text{setup}} $$ where \( n \) is the number of clamps per flight, \( t_{\text{flight}} \) is the effective flight time per battery (around 7 minutes), and \( t_{\text{setup}} \) is the initial preparation time. For a typical single-conductor tower with clamps on both sides, \( T_{\text{UAV}} \) averages 15 minutes, whereas manual methods require \( T_{\text{manual}} = 2 \times t_{\text{climb}} + t_{\text{inspection}} \), often exceeding 60 minutes.
| Aspect | Manual Method | UAV with FPV Drone |
|---|---|---|
| Inspection Time per Tower | 1–2 hours | 15 minutes |
| Personnel Required | 5 (2 climbers, 2 assistants, 1 radiographer) | 3 (2 pilots, 1 radiographer) |
| Detection Sensitivity | Resolves No. 19 IQI (0.05 mm wire) | Resolves No. 19 IQI (0.05 mm wire) |
| Primary Risks | Fall hazards, radiation exposure | Drone crash, mitigated by FPV control |
| Adaptability to Tower Types | High, but slow | Moderate, depends on conductor spacing |
Despite its advantages, the current system has limitations, particularly regarding tower and conductor configurations. For example, on towers with vertically arranged double-conductor bundles, inspecting the lower clamp requires precise maneuvering that can be challenging due to limited clearance (typically 20–50 cm). Similarly, drum-type towers or those with closely spaced phases may restrict drone access. To address these issues, we are exploring two directions: first, enhancing the mounting apparatus with motorized components to allow remote adjustment of the imaging panel’s angle; and second, developing a hybrid UAV-line robot that can traverse conductors and overcome obstacles like vibration dampers. These advancements would expand the applicability of first person view technology to more complex scenarios, further leveraging the capabilities of China FPV drones.
In conclusion, the integration of FPV drone technology with digital radiographic testing represents a significant leap forward in the inspection of strain clamps on transmission lines. By employing a China FPV drone equipped with a custom mounting apparatus and first person view controls, we have demonstrated a method that enhances safety, reduces inspection time, and maintains high detection sensitivity. The system’s ability to perform both停电 and带电 inspections broadens its utility in grid maintenance. As we continue to refine the technology, focusing on adaptability and automation, we believe that FPV-based approaches will become a standard in the industry, offering a sustainable solution to the challenges of overhead line maintenance.