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Live operation is an important means of power operation at present, but there are huge safety risks in the operation process, which will pose a great threat to the stability of power system and the lives of operators. Therefore, it is extremely important to use appropriate tools in the process of live line operation. It is necessary to follow the development of live line operation technology to do a good job in tool research and development, meet the needs of different kinds of live line operation, provide sufficient security for operators, and promote the stable development of the electric power industry.

In the state detection of transmission lines, the use of live operation can avoid the influence of detection work on normal circuit operation and ensure the service of power system. However, live operation is a strict technical measure. As the circuit is still running during the operation, there may be the risk of electric shock, which is a relatively dangerous working mode [1]. If the operation is not up to standard in the process of work, operators, regional power supply, transmission line operation and other production and life will be affected. If the operator fails to operate or has a problem with the tool, he or she will receive severe electric shock and seriously endanger their life.

It is very important to determine the key technical parameters and choose the appropriate tools for live operation because of the obvious danger of live operation. The tool must meet the minimum insulation length, especially for 1000kV high voltage AC circuits, the tool must provide adequate protection to the operator.

1. Analysis of reasons for safety problems in live transmission line operation

Live working environment risks. As the live transmission line operation itself has a high risk, so if the site environment is more complex, it will increase the risk in the operation process. For example, the surrounding weather conditions, terrain, communication lines, traffic and other problems will affect the development of live operations. Therefore, before the start of live work, operators need to survey the surrounding situation, master the site traffic, in order to develop a suitable live work plan. For example, do a good job in weather prediction and equipped with anemometer and other devices to understand the environment on site, avoid working in strong wind, heavy rain, snow and other conditions, such as extreme weather in the process of operation to stop live operation.

Tool management issues. Transmission line site safety protection, not only personal protection work, but also through tool management to ensure the safety of live operation. However, many operators lack the awareness of tool management, the lack of regular inspection and maintenance of tools, easy to lead to tool aging and damage, thus affecting the safety of the operation process; Secondly, there is also a lack of perfect tool management system, tools lack of perfect information, but also lack of tool inspection awareness before operation, which is easy to cause hidden dangers in the work.

Hidden danger of live operation. At present, all live working tools are insulation tools, the insulation level of the tool material determines the insulation effect of the tool. However, some tools may have substandard insulation and damage, which can lead to accidents during operation. There are also some tools that are not designed properly, which can not achieve the ideal operation effect, do not meet the standard of live operation, will cause safety accidents.

Current new metal tools for live working

2.1 Tools requirements for live operation

As uHV and UHV transmission lines have very high voltage grade, large line spacing, more wire splitting, and large insulator string length and tonnage, very high requirements are put forward for operating tools [2]. In general, the minimum effective insulation length of the line should be selected. For example, the wire lifting tool should meet the requirements of large tonnage and soft insulation of the line load. Metal fixtures should also be combined with the characteristics of the circuit to optimize the structure of the tool to meet the requirements of the working process and reduce the working intensity of the operator. At present, a tight wire tool with hydraulic transmission device has been developed.

For the tool selection under live operation, first of all, it needs to have high insulation, meet the requirements of voltage level, and have high weather resistance; Secondly, the tool should have enough mechanical strength to adapt to the working needs of the uHV circuit wire, the dead weight of the fittings and the increase of the line distance, so as to avoid the damage of the operating devices. In order to improve the flexibility of construction, live working tools must be light. For example, in order to cope with insulator strings of different lengths, supporting tools should be larger in length and more reasonable in volume, but they should also be able to control the weight of tools to meet the requirements of convenient transportation and dexterity of operation. Finally, for some special tools must have high versatility.

2.2 Straight hanging line clamp U-bolt filling and tightening tool

Transmission lines straight hanging clamp U bolt tightening solid tools joined the transmission device, including the rear hand turn handle operation, composite insulation lever, the transmission device of the tool can be 180 ° rotating suspension, and with a special storage sleeve, bolt into the fastening device used at the same time, special bolt sleeve inside can deposit in the bolt, spring cushion, flat mat, Achieve fastening bolt and remote filling function. By using the method of position live operation, the problem of loosening and falling off of u-bolt of conductor overhang clip in power system can be solved. After the u-bolt is added, the tool’s steering device can be replaced with a revolving ratchet wrench to ensure the bolt is tightened.

The tool has the characteristics of simple operation, flexible operation and high working efficiency by adding and fastening the u-bolt of overhanging line clip. Insulation materials are used in the design of the tool, which can ensure the safety and status of live work to the greatest extent and meet the electrical insulation requirements of live work. Besides, it has good versatility and can work in any weather conditions [3]. Through the supplement of position live band parts, the temporary power failure can be avoided, the safety of operation can be guaranteed, the reliability of the line can be guaranteed to a great extent, and higher economic and social benefits can be created.

2.3 Multi-functional electric spraying tool

The tool consists of an operating head, a telescopic insulating lever, and an operating mechanism, in which the operating head uses a special clamping device, which is connected to the clamping device by a telescopic lever, and which is then driven by a rear manipulator to operate the tank inside the clamping device so that the anticorrosive material can be applied close to the tool. The tool can also meet the work requirements of live work, can ensure the safety distance of work, to achieve indirect live work. It can effectively solve the corrosion of parallel clearance, burn, corrosion of gold fittings and corrosion of shock hammer, and can be repaired by electrified operation. Using this tool can be used in hydrophobic environment, complete the electrical equipment with zinc spraying, to ensure the stability of power equipment.

2.4 Multi-angle tensioning drainage plate bolt fastening tool

There are many directions of tensile drainage plate bolts, including transverse line direction, oblique line direction, along the road direction and so on. For this purpose, three turning points are set on the wrench, among which the head turning point can be rotated horizontally by using the sleeve. In order to adjust the Angle, the current tool can be rotated horizontally by 180°; According to the actual working conditions of the power system, the tool can be fixed at multiple angles and multi-points to solve the problem of disharmony between bolt angles and sleeve angles. For the middle turning point, the spanner can be used for multi-angle rotation, adjust the direction of the sleeve on the spanner, effectively solve the requirements of bolt torque, meet the installation needs of the bolt along the line. The tool also eliminates the need for a safe drainage distance. By connecting the bottom rotation point to an insulated lever, the operator can push and pull the lever to rotate the sleeve, which rotates the drain plate bolts. The use of this tool improves the convenience of the work site, and ensures the requirements of wire fastening bolts with different directions of tension drainage plate.

2.5 Insulating metal fixtures

The development of insulating metal fixtures for live work should be based on the structure and characteristics of line insulator parameters. Since the load range of insulator strings of UHV lines is generally 210 ~ 550kN, the rated load of insulating fixtures should be 60 ~ 145kN according to the design principle [4]. At present, in domestic ultra-high voltage lines, the straight metal clamps used include I type, V type and double string, and the tensioning insulator string includes double or multi-disc insulators. Different insulator replacement tools can be used according to different insulator string forms and the characteristics of connecting fittings. Through the use of metal fixture can better complete the transfer of tonnage work, to meet the requirements of operators in the field. For large tonnage metal tools, the main material consists of titanium alloy and is processed using a new cutting process. To facilitate more efficient transmission of wire load, the fixture also includes hydraulic and mechanical wires to meet the needs of the retracting and retracting rods.

3. Future research and development direction of transmission operation tools

The current domestic homework in uhv transmission lines has a lot of research, a new tool can meet the needs of field work, including walking wire, wire inspection, equipotential metal tools, such as the function of the tool more comprehensive, and in view of the 800 kv dc high tension line charged job, live working tools also has the very high application value. In the future research, we should continue to strengthen the tool research and development for high-altitude areas, deeply study the line characteristics of high-altitude areas, and use tools to ensure the safety of live operation. It is necessary to continue to strengthen the research of high strength flexible insulating materials and make more flexible insulating lifting tools. In the research of equipotential tools, the research of lightweight and mechanized devices should be strengthened to enhance the intelligence of detection tools. In the operation equipment, it is necessary to further study the role of helicopters and other equipment in the operation, as well as strengthen the research of other large machinery to verify the work performance.

To sum up, protection work must be done well during live operation of transmission lines, and operators should choose appropriate tools to ensure safety during operation. Research and development personnel should fully analyze the live line operation situation, do research and development work to meet the current live line operation requirements, and focus on the future, research and development for new transmission systems and live line operation tools in high altitude transmission environment, to minimize the risk of operators.