Development and Current Status of Live-Line Working in High-Voltage Distribution Networks

With the continuous development of my country's economic construction, improving the reliability of power supply has become an important task for the power sector. This requires us to vigorously carry out live-line maintenance and repair work in order to improve the reliability of power supply.

Ensuring a continuous power supply is a fundamental requirement for electricity across all sectors of the national economy. With the continuous development of my country's economy, urban power supply reliability has become a key performance indicator for power supply companies. Improving power supply reliability has become a crucial task for the power sector. Even power outages due to maintenance of distribution lines and equipment are no longer permitted. This necessitates a vigorous effort to conduct live-line maintenance and repair work to enhance power supply reliability.

I. Economic Benefits of Live-Line Work

The economic benefits created by live-line work include both calculable and incalculable parts. The calculable part can be categorized into two forms: direct benefits and social benefits. Direct benefits are those obtained by the power sector; social benefits are the increased revenue for factories and mines due to the increased power supply. Incalculable benefits are reflected in reducing power supply accidents, improving power supply reliability, eliminating adverse political impacts, and facilitating people's lives in many ways.

II. Working Environment for Live-Line Work in High-Voltage Distribution Networks

The work location is in the urban area, which is noisy, with noise from the boom truck, etc.; there are many accidents with power distribution equipment, frequent operations, and many abnormal situations in the lines; the lines are complex, with multiple circuits and high and low voltage lines on the same pole; the power distribution equipment is severely corroded; the distance between each phase and the distance to the ground of the power distribution lines are small; and the work is done at height.

Therefore, due to the working environment, the difficulty and labor intensity of this work will be greater than that of live-line work at high voltage levels.

III. Live-line working methods

Due to limitations in tools, equipment, and protective gear, traditional live-line work in power distribution largely relied on shielded suits and indirect methods such as elevated insulated boom trucks or ground potential. Based on the safety distances defined in regulations and the site environment and electrical equipment structure conditions for live-line work, it's clear that indirect methods should be prioritized for safety. However, with advancements in live-line work technology both domestically and internationally, the performance and specifications of insulated suits have improved significantly, and insulated protective tools have become more reliable and lightweight. In particular, foreign insulated tools are superior to domestic products, and most organizations now use foreign insulated suits and protective gear. Furthermore, many lightweight electro-hydraulic maintenance tools from abroad have greatly reduced the workload for workers. Therefore, fully insulated work methods are now more commonly employed.

"Fully insulated work method" is a professional term we often hear. Through our experience, we have expressed skepticism about this term, as it carries certain risks. Therefore, we wish to discuss this with our colleagues. Regardless of the specific conditions, the insulation properties are relative. True safety requires a sound safety mindset, proper behavior, and rigorous management systems, rather than mechanically relying on certain tools to guarantee safety.

IV. Characteristics and Problems of Live-Line Work in High-Voltage Power Distribution

Safety must be the primary consideration when performing live-line work on high-voltage power distribution networks. The voltage in high-voltage distribution networks is lower than that of transmission networks, the air gaps between the three-phase conductors are smaller, and the distribution facilities are densely packed, limiting the working area for personnel. Working within this confined space, coupled with the lack of visibility due to high voltage and the fact that workers are operating at heights on utility poles, often leads to dangerous actions and the risk of contact with other electrical facilities at different potentials. Therefore, if safety measures are inadequate, work methods are not standardized, or tools are used improperly, single-phase grounding, phase-to-phase short circuits, and even personal injury accidents can easily occur.

Problems with inadequate safety protection measures. Safety protection measures are one of the most important measures to ensure the safety of production personnel during live-line work on power distribution networks. Therefore, the key safety protection measures are: first, using good insulating tools to isolate or shield live conductors and grounding conductors during work; second, workers should wear qualified full sets of insulating protective equipment. The problem is that currently, insulating protective clothing produced domestically in my country has some problems to varying degrees, so most of the products used are imported. These products are numerous and varied; when selecting them, special attention should be paid to the electrical parameters provided, and appropriate selection and use should be made according to the intended purpose. We believe that the correct method of use depends on the live-line work method adopted, which determines the insulating and auxiliary insulating objects. For example, when using the indirect work method (i.e., the ground potential method), the insulating tools are the primary insulation, and the insulating protective equipment worn by the operator is the auxiliary insulation. If the pole-mounted insulating platform method or the insulated bucket truck direct work method is used, the insulating platform and the insulated bucket truck are the primary insulation, while the insulating equipment worn by the operator is the auxiliary insulation. In the direct work method, the full set of insulating clothing worn by the personnel is crucial as backup protection. Therefore, insulating clothing or insulating tools not only require high breakdown voltage, but also high surface flashover voltage and very low surface leakage current.

V. Main tools and equipment for live-line work in high-voltage power distribution and existing problems

(I) Insulating Protective Clothing 1. Problem: Regarding insulating protective clothing for 10kV live-line workers, the national standards are not yet fully comprehensive. However, most units nationwide that have already started 10kV live-line work have widely purchased and used various imported insulating protective equipment. This is because some imported insulating protective clothing uses high-performance insulating materials with high voltage resistance, and is lightweight, effective, and performs well. Therefore, it is favored by many domestic users. The problem to be discussed is that the electrical parameters of these imported insulating tools do not meet the requirements of my country's safety regulations. Using them would violate industry regulations. If these products are not accepted, domestic manufacturers cannot currently provide products that meet the needs of users.

2. Perspectives on solving the problem:

Through learning and production practice, we believe that the tools and equipment used for 10kV live-line work imported from abroad are appropriate.

First, when purchasing, you must have a clear understanding of the electrical performance and physical characteristics of the tools with the seller, and purchase them carefully according to your own needs. When you decide to purchase, it is best to include the warranty requirements promised by the seller in the agreement.

Secondly, for imported live-line working tools and clothing purchased that do not meet the current requirements of my country's "Safety Regulations," but are scientifically analyzed and verified to be usable in production, it is appropriate to use the established enterprise standards to regulate them.

Third, for purchased live-line working tools and equipment, a thorough inspection and testing process must be organized upon receipt (mainly by the materials department). Before being handed over to production teams for use, they must undergo strict electrical testing in accordance with the requirements of the "Live-line Working Technology Management System," the "Safety Regulations," and enterprise management standards. Only after all tests are passed can they be provided to the producers for use.

Fourth, producers should carefully inspect these insulating protective devices before and after production, because these products are made of plastic or rubber and are exposed to various metal equipment and components during use, so they are inevitably scratched or damaged. Therefore, it should be emphasized that they should be carefully inspected before production begins and after work is completed in order to detect problems in time and prevent accidents from happening.

(ii) Insulation and concealment tools

1. Problem

Currently, many domestic manufacturers are actively organizing production. However, due to a lack of management regarding the applicability, versatility, appearance, and dimensions of tools, tools for the same purpose are becoming increasingly diverse, with varying sizes and significant differences. Secondly, some manufacturers prioritize profit over product quality. Consequently, many shielding tools fail to meet electrical strength requirements, frequently exhibiting surface discharge or breakdown during testing, which significantly impacts normal production during live-line work.

2. Suggestions for addressing the problem

First, manufacturers should research and develop new and better insulation materials. Second, the selection and design should be more scientific, and more user information should be collected. Third, national and industry authorities should standardize industry standards and make manufacturers' material selection, material use, production technology management, and process requirements more standardized (especially since my country has joined the WTO). We sincerely hope and look forward to good, new, and technologically advanced new tools appearing in power grid production as soon as possible.

VI. Development Trends of Live-Line Working in High-Voltage Distribution Networks

To meet the demands of modernization, rigorous assessments of live-line work are essential, along with strengthened research into fundamental theories. Only through this rigorous process can live-line work technology continuously innovate and develop; otherwise, its progress will stagnate.

The development of power transmission lines has led to the emergence of compact tower lines to reduce the space required for line corridors. However, this presents challenges in maintaining safe distances during live-line work. Utilizing robots in live-line work is one important way to address this issue.

The application of helicopters in live-line working, using helicopters as the primary tool for this purpose, is already widely adopted in some developed countries. Currently, some domestic organizations are researching the application of helicopters in live-line working, and the State Grid Corporation of China is undertaking this project.

Conclusion

my country is currently experiencing a period of rapid economic growth, and all reform measures should be based on whether they can mobilize people's enthusiasm and vigorously develop productivity. Live-line working is a new technology that benefits the national economy and people's livelihood, and it should receive full attention and promotion. Ensuring safe production and standardized management of live-line working will promote the development of live-line working and enable it to create greater benefits for society.