Jiahong He

Adopting mobile robots for high voltage (HV) live-line operations can mitigate personnel casualties and enhance operational efficiency. However, conventional mechanical arms cannot inspect concealed spaces in the power cable tunnel because their joint integrates metallic motors or hydraulic serial-drive mechanisms, which limit the arm’s length and insulation performance. Therefore, this study proposes a 7-degree-of-freedom (7-DOF) bionic mechanical arm with rigid-flexible coupling, mimicking human arm joints (shoulder, elbow, and wrist) designed for HV live-line operations in concealed cable tunnels. The arm employs a tendon-driven mechanism to remotely actuate joints, analogous to human musculoskeletal dynamics, thereby physically isolating conductive components (e.g., motors) from the mechanical arm. The arm’s structure utilizes dielectric materials and insulation-optimized geometries to reduce peak electric field intensity and increase creepage distance, achieving intrinsic self-insulation. Furthermore, the mechanical design addresses challenges posed by concealed spaces (e.g., shield tunnels and multi-circuit cable layouts) through the analysis of joint kinematics, drive mechanisms, and dielectric performance. The workspace of the proposed arm is an oblate ellipsoid with minor and major axes measuring 1.25 m and 1.65 m, respectively, covering the concealed space in the cable tunnel, while the arm’s quality is 4.7 kg. The maximum electric field intensity is 74.3 kV/m under 220 kV operating voltage. The field value is less than the air breakdown threshold. The proposed mechanical arm design significantly improves spatial adaptability, operational efficiency, and reliability in HV live-line inspection, offering theoretical and practical advancements for intelligent maintenance in cable tunnel environments.

Electrical phase verification identifies the phase reference between three phases in two different power transmission systems. Conventional phase verification of overhead lines requires several workers to climb up, then, hang and hook the phase detector sticks to the overhead lines. Manual operations lead to power outages and increase the risk of workers falling from height or being electrocuted. This study investigated a self‐insulated rope‐driven mechanism framework to hook up and take off a phase detector on the transmission line. The framework balances robotic dynamic stability performance during high‐altitude operations and ensures that phase verification operations can be performed efficiently without power interruptions. The stability of the proposed framework was analyzed under external wind disturbances and collisions. Finally, experiments are conducted to verify the accuracy of the analysis and the feasibility of the scheme. Simulations and experiments show that the proposed robot is capable of lifting phase detector sticks up to a height of 8.6 m, while the maximum wind speed is 7 m/s and the maximum collision force is 6.7 N.

Electrical trees have different shapes and growth rates under different voltage conditions. This paper proposes an electric and stress field-driven electrical tree simulation model. The stress field describes the gas expansion of the partial discharge process. This model introduces the driving energy to determine the tree shape according to multi-physical fields instead of controlling the tree shape manually by artificial parameters. The electrical tree simulations and experiments were carried out to analyze the electric and stress field distributions under 11 kV and 15 kV voltages. The tree under 11 kV is branch-shaped (fractal dimension = 1.33), with the electric and stress fields concentrated at the tree tips. Meanwhile, a significant densification effect of the electric field replaces the concentration effect and causes a bush-shaped tree (fractal dimension = 1.72) under 15 kV. The tree-driving energy during tree growth under 15 kV constantly decreases faster than 11 kV. Consequently, the tree length under 15 kV is 69% shorter than 11 kV due to the decrement of the driving effect of the stress field. The proposed model explains the geometric shapes and growth rates of electrical trees under different voltages.

The use of mobile robots in substations improves maintenance efficiency and ensures the personal safety of staff working at substations, which is a trend in the development of technologies. Strong electric and solid magnetic fields around high-voltage equipment in substations may lead to the breakdown and failure of inspection devices. Therefore, safe operation range measurement and coordinated planning are key factors in ensuring the safe operation of substations. This paper first summarizes the current developments that are occurring in the field of fixed and mobile safe operating range sensing methods for substations, such as ultra-wideband technology, the two-way time flight method, and deep learning image processing algorithms. Secondly, this paper introduces path-planning algorithms based on safety range sensing and analyzes the adaptability of global search methods based on a priori information, local planning algorithms, and sensor information in substation scenarios. Finally, in view of the limitations of the existing range awareness and path-planning methods, we investigate the problems that occur in the dynamic changes in equipment safety zones and the frequent switching of operation scenarios in substations. Furthermore, we explore a new type of barrier and its automatic arrangement system to improve the performance of distance control and path planning in substation scenarios.

Grippers with a single rigid or flexible state have corresponding limitations, such as poor safety of rigid grippers and low precision of flexible grippers, which require complex algorithms and additional sensors to perform tedious tasks. Here, we design a reconfigurable gripper based on three fingers that can switch among the rigid, rigid bending, and flexible states. This adaptability enables the gripper to perform in diverse application scenarios. The flexible joints are locked and released by the back-and-forth movement of a slider mechanism, thus enabling switches between the rigid and flexible states of the fingers. When the fingers are in the rigid state, the structure resembles a conventional rigid gripper; when the fingers are in the flexible state, the spring-supported joints are driven by four cables. We have developed the mathematical models for the three states, tested the performance of different grasping configurations, analyzed the factors that influence horizontal grasping errors, and finally explored the application of rigid-flexible cooperative operations. Numerical and empirical experimental results clearly demonstrate the viability of the proposed gripper and its wide adaptability to different tasks.

High-voltage direct current (HVDC) submarine cables should be discharged to efficiently reduce the cable voltage after the withstand voltage test in the substation. This article proposes a fast discharge optimization strategy to minimize the time duration from the test voltage to the ground voltage. The discharge process is under the constraints of the maximum power and thermal duration of the resistors and can be divided into two stages. The first stage is the process when the discharge device moves close to the cable terminal before the physical connection. The device structure is optimized to reduce the arc length around the cable terminal. The second stage optimizes the resistor bridging process after the connection to accelerate the discharge process. Compared to the traditional constant resistance discharge method, the proposed structure of the discharge resistors shortens the average arc length by 36.2%, and the discharge time is reduced from 31.5 to 13.2 min. The optimized strategy reduces the potential threat of the arc to the equipment in the substation and the probability of cable damage due to overvoltage.

Long-term exposure to high temperatures can lead to the physicochemical properties of DC cross-linked polyethylene (XLPE) cable material degrading irreversibly, compromising its electrical performance. In this work, the effects of thermal aging on electrical tree initiation and the performance of treated cable material were examined. A Dam-flood model was constructed to investigate the effect of thermal aging on electrical tree initiation behaviors, where indices corresponding to aging performance and electrical tree initiation behaviors were obtained based on this model. Ultimately, by means of multiple linear regression estimation and a GM (1, N) model, prediction methods for the electrical tree initiation voltage ( U _50% ) and electrical tree initiation probability ( P ) were proposed. Results indicate that U _50% and P do not exhibit a monotonic change with an increase in thermal aging time and, based on the Dam-flood model, the recrystallization reaction can be regarded as the primary cause for this phenomenon. According to the Dam-flood model, the indices for gel content ( C_ge ), crystallinity ( X_c ), and dielectric DC breakdown strength ( E_b ) are significantly correlated with U _50% , and these three indices can be used to determine the changing regularity of U _50% . Furthermore, as the relative errors of the validation samples are all less than 15%, an equivalent relationship between P and the indices corresponding to thermal aging performance can be established. This could be used in future research to determine the electrical tree initiation of XLPE cable.

The reliable distributed monitoring system provides the real-time video observation from the power cable tunnels when the preinstalled communication system is disabled in an emergency. The spherical robotic prototypes are designed as the sensor node based on the analysis of the robot dynamic model. A novel self-constructed mobile wireless sensor network (MWSN) is proposed to realize the communication and positioning functions through the fusion of the Ad-Hoc and ultra-wideband (UWB) approaches. The Ad-Hoc network consists of multiple robot nodes as sensor carriers and relay stations to transmit large amounts of data from the accident scene to the monitoring terminal. The UWB network consists of UWB tags and bases on each node and implements the leader-follower (LF) strategy to create the robot formation. In order to maximize the monitoring area and maintain the reliability of the network, the traditional LF strategy is optimized based on the N-X algorithm subjected to the constraints of node number, Ad-Hoc communication and UWB positioning range, and the power tunnel boundaries. A self-constructed MWSN consisting of five robotic nodes ( N=5) is capable of covering 40 m of power cable tunnel, when the value of X is selected as 3. The network failure probability reduces from 73.5% ( X=0) to 0.2% ( X=3) when the malfunction probability of sensor node is 23.3% due to the accident condition in the tunnel. Finally, the simulation and experimental results show that the optimized LF algorithm increases 20.2% coverage of the network in the curve formation. The network transmits a monitoring video streaming with a 320×240 pixel resolution and a delay less than 150 ms. The real-time video observation from the accident scene is significant to formulate the emergency countermeasure and investigate the direct cause of the accident.