Radiation crosslinking thermoplastic material (thermoplastic material for short) is a new type of insulating material in recent years. This paper introduces the type, technical performance of thermal shrinkable materials and their application in substation.
Insulation level applied to thermal shrinkage substations
In recent years, with the continuous development of industry and the increasingly serious environmental pollution, the insulation protection requirements for substations have been continuously improved, especially the insulation protection of the old substations has become increasingly important. In fact, pollution flashover, condensation flashover, ice icing tripping, short circuit of small animals, and naked busbar accidents occur frequently in substations. Therefore, the choice of using high-quality insulation material is of great significance for the safe operation of power system.
This paper aims to introduce the technical parameters related to thermal shrinkage materials and substation and some practical problems that can be solved for substation. It expounds the application of radiative cross-linking thermal shrinkage materials in substation and provides a new insulation protection method and new insulation materials for power system.

1. Types of heat-shrinkable materials
The heat-shrinkable materials used in substation include master insulation heat-shrinkable sleeve (MPG), compound insulation heat-shrinkable belt (FJRD), insulating cover, cable terminal head and climbing distance grower.
MPG is used for insulation protection of convergent bus in substation with excellent insulation performance and process characteristics.
FJRD is a compound heat-shrinkable insulation cladding belt, whose structure is composed of the heat-shrinkable layer and the adhesive layer of low-melting high-polymer. When heated, the outer layer shrinks and the inner layer melts, thus making the shielded electrified body realize sealing and insulation integration. It is used in the old substation of the lack of phase spacing, pollution flash and ice serious and difficult to implement insulation treatment. The insulation protective box is used for the insulation protection of the joint, as well as the special contact protection such as the isolation switch on the cabinet and the oil circuit breaker.
The cable terminal has excellent performance, simple and quick installation, and does not need special equipment and technology. It is widely used in power system and becomes the latest development direction of power cable accessories.
Creep augmentation device is used to solve the pollution flashover problem caused by pollution levels. Generally speaking, as long as the original post insulator or porcelain bottle heat shrink the corresponding size of the umbrella skirt can solve these problems.

2. Technical performance
The heat shrinkable material is used in the bus of substation confluence, and will not affect the temperature rise of the bus
The temperature rise experiment of the xi 'an high pressure research institute on the application of 1000A in the switch cabinet proved that the temperature rise was basically not affected under the condition of the same temperature measurement point after the heat shrinkable materials (MPG and FJRD) were coated with the bus bus. In this regard, ABB, GE, Siemens, Westinghouse and Westinghouse have all made the most convincing practical examples in their application of heat-shrinkable materials. Therefore, the insulation protection of heat shrinkable materials on the busbar of substation will not affect its temperature rise and will not reduce the load flow of the busbar.
(2) flame retardant property of heat shrinkable materials
In the power system, indoor insulation materials are required to be flame-retardant. The heat shrinkable materials used for insulation protection of substation are mainly made of rubber and plastic blend polymer, with the addition of flame retardant with excellent performance. The flame retardant requirement of power system can be met.
(3) aging resistance of heat shrinkable material
The power supply equipment of the power system needs to have long-term operation reliability. Therefore, the radiation crosslinking thermal shrinkage material is widely used in foreign power systems for its superior performance over other materials. We know that the heat shrinkable material has better aging resistance than other insulating materials due to the cross-linking structure derived from internal network in terms of thermal shrinkage principle, thermal shrinkage property and microscopic nature. The accelerated aging experiment conducted by Shanghai cable institute on changchun heat-shrinkable materials co., LTD. Shows that the thermal aging life of this material can reach 20 years. The thermal shrinking end used by Shanghai cable institute in 1984 has been running safely for 13 years, and the polyolefin heat-shrinkable materials applied on artificial satellites have been running normally for 21 years.
(4) temperature resistance of special heat-shrinkable materials for substation
Pyrocondensation material because of its special microscopic nature, by the 158 + 2 ℃, 168 h after thermal aging experiments, performance without big changes (for substation special series of pyrocondensation material). Generally speaking, the limit of the substation bus working temperature is 70 ℃. Therefore, the special heat-shrinkable materials can meet the requirement of temperature resistance of substation.

3. Application
Above, we describe the electrical and physical characteristics of the thermal shrinkage material. This new material can solve many practical problems when applied to the insulation protection of substation.
(1) effectively eliminate the common small animal short circuit fault in substation
For a long time, the technical personnel of the power supply system have been troubled by the electrical accident caused by short circuit fault of small and medium animals in the substation and the lap of foreign body. After the implementation of thermal shrinkage insulation protection for the switch cabinet and confluence bus of the substation, the original electrified conductor has high quality insulation characteristics. Therefore, even if some small animals enter the substation due to loose protection, there will not be tripping or burning caused by the short circuit of small animals. After insulating with heat-shrinkable materials, the electrical distance of 10KV switch cabinet busbar from the bare busbar is 125mm down to 6mm, which can greatly reduce the size of switch cabinet, reduce the cost of switch cabinet, and reduce the floor area and civil investment.
(2) prevent trip accidents such as pollution flashover, condensation flashover and ice icing
Due to the increasing environmental pollution, more and more substations have higher pollution levels, and the failure rate of the old substations has increased. Therefore, insulating the main bus and the branch bus in the cabinet and adding the crawler to the original post insulator have become an effective method to transform the old substation under the full working condition. In this way, we have already reconstructed the 220KV shandui substation in shishi, fujian province, and changshan substation in zhangzhou region, and we plan to transform the temporary low-pressure part of the mudanjiang lianhua hydropower station. Due to high relative humidity, the electric system of hydropower station in high temperature area also has the problem of tripping accident caused by condensation flashover. The northeast cold region in winter temperatures can reach to 45 ℃, may also be caused by ice insulator discharge, the heat insulation protection can solve these problems.
(3) effectively prevent casualty accidents caused by electric bare discharge
In the old transformer substation, because the switch cabinet bus and the bus bus were not insulated, the maintenance staff was injured by the live body. The main bus, branch bus and joint parts of the substation are insulated with thermal shrinkable materials, which can eliminate this danger. In Shanghai shidongkou power plant, local insulation treatment is also carried out on the bus row of three-phase four-wire in the low-voltage distribution screen.
(4) prevent corrosion of bus by salt spray and harmful chemical gases
Salt fog in coastal area and industrial waste gas in heavy industry area corrode the bus line of confluence. In addition to reducing the bus load, it is also easy to generate dirty conductive channel, which leads to pollution flashover. The heat-shrinkable material has excellent acid and alkali resistance and can solve this problem effectively.
(5) climbing distance grower is used to solve the insufficient climbing distance of pillar insulator
Insulators on outdoor 220, 110, 66 and 35KV electrical devices of substations and indoor busbar support insulators often cause pollution flashover due to severe lack of pollution. To solve this problem, we only need to add the thermal expansion device to a porcelain skirt.

4. The conclusion
To sum up, thermal shrinkage material is used for insulation protection of substation, which is technically safe and reliable, simple and feasible in construction, and the benefits of previous technical investment are long-term benefits. It achieves the purpose of one-time construction, comprehensive protection and long-term safety, and provides an effective new method for the safety operation of the newly developed unattended substation (less people on duty) and the renovation of the old substation with high failure rate. At present, the application of thermal shrinkage material has become the development direction of improving insulation protection level of substation.