In recent years, with the rapid development of China's reform and opening up of the economy, the living standards of residents and the degree of socialization has improved greatly, the electricity consumption of families has increased accordingly, and the total scale of electricity consumption has also improved qualitatively. This has put forward new requirements for China's electric power business, and also to a certain extent promoted the development of the electric power industry. Research shows that the failure rate due to lightning damage and tripping of the aerial insulation cable has accounted for more than 70% of the total failure, seriously affecting the normal operation of the power system, causing huge economic losses to power enterprises. Therefore, electric power enterprises need to strengthen the lightning breakage and lightning tripping prevention technology of aerial insulation cable to ensure the stable operation of power distribution lines.

1. Impact on the aerial insulation cable by lightning strikes.

Different failures occur upon different degree and type of lightning the aerial insulation cable has come across. For example, when a multi-phase fault occurs in an aerial insulation cable directly struck by lightning, the backlash from the lightning can cause other faults. First, tripping phenomenon occurs, continuous tower equipment often appears abnormal flashover phenomenon. Positive triangle array selection will appear abnormal. The phenomenon of shorting can also occur in the lateral midline of the line. For the lightning excitement phenomenon, the aerial insulation cable will appear one-way short circuit error.

However, the lightning phenomenon of the whole system aerial insulation cable has a great impact on the whole system, especially the commonly used 10kV oaerial insulation cable. The error situation is as follows: First, it is easy to be struck by lightning. Second, the tripping phenomenon; Third, the connected electrical equipment may be damaged by lightning. Fourth, there may be an abnormal insulator flashover, threatening the safety of life and property. In addition, lightning strikes on aerial insulation cable generally occur under relatively severe weather conditions, and lightning strikes suffered during the rainy season can easily cause large trees to topple. In this case, if a reasonable solution is not taken as soon as possible, the connection phenomenon will occur, and even passers-by will be electrocuted, seriously affecting people's production life.

2. Reason of the lightning breakage and tripping phenomenon of aerial insulation cable

It is known that at this stage in China's aerial insulation cable, the insulation performance is relatively low, generally only the power distribution energy at normal temperature, and can not play any role in the face of lightning and other powerful high current. Generally speaking, 5-7KA of current will cause the trip fault of aerial insulation cable, but in the case of lightning strikes that generate about 40KA of current, when the aerial insulation cable is exposed to lightning, lightning damage and tripping phenomenon will occur. For the aerial insulation cable, the following reasons are summarized for its easy to get lightning strikes. First, the 50% discharge voltage of the insulator of the aerial insulation cable; The insulator flashover fails. Lightning is easy to create the insulator flashover phenomenon, which may damage the insulator. When a thunderstorm occurs, the overvoltage caused by the lightning will increase the load on the distribution line and quickly exceed the range that the voltage can withstand on both sides of the insulator, thus triggering a series of flashover problems. In addition, the insulator is exposed for a long time and itself is susceptible to damage such as insulator heating due to external natural weather, when it should be replaced with an insulator with better insulation. The intensity of the lightning current is very high. The grounding resistance of the tower in the aerial insulation cable is relatively small. However, the high-voltage lines have a series of lightning protection devices set up to avoid the phenomenon of high-voltage lines tripping, but at this stage, these measures of lightning protection irregular construction is also an important factor for the breakage and tripping phenomenon of the aerial insulation cable lightning.

3. Aerial insulation cable lightning damage and trip prevention technology

3.1 Lightning protection technology

Apply the "switch" lightning protection technology to the actual aerial insulation cable can effectively increase the electrical resistance of the transmission line. The technicians concerned protect the insulator string by inducing flashover and frequency arcing, effectively ensuring the probability of successful reclosing. In practical application, electricians can implement two technical solutions: first, reasonable setting the parallel spacing of the insulator string. In order to make the insulator string and the equipment in the gap work properly, set the distance between the two, so that it is located in the insulator string within the dry arc length. But it should be noted that the technical solution is not suitable for the use of high-voltage aerial insulation cable. Electricians should install line type lightning protection device. The main chemical composition of this type of lightning protection device is zinc oxide. Its role is mainly manifested in the following aspects. The installation of the device can effectively improve the overall aerial insulation cable lightning protection performance. It can effectively improve the overall aerial insulation cable retrograde lightning resistance performance, greatly reducing the tripping phenomenon of the aerial insulation cable by lightning.

3.2 Analysis of overvoltage protection strategy for distribution lines

(1) Strengthen line insulation

The strengthening of line insulation is generally accompanied by cost issues and expenses. From an economic point of view, strengthening the level of line insulation needs to ensure that the line works properly, ensure the basic requirements of internal voltage, and able to have comprehensive analysis in combination with the actual situation. Blindly increasing the level of line insulation can be counterproductive. Therefore, in the process of strengthening the line insulation capacity, ensure the efficiency and reasonableness, and conduct a detailed analysis of various factors to ensure the efficiency and reasonableness of strengthening the line insulation. For example, if it wants to the actual impact insulation strength of the insulator string in the line, it can use wooden poles instead of cement, if it wants to improve the actual insulation of wooden poles, then it can try not to use steel bars to prevent the lightning impact process of lightning current from exceeding the average electric field strength, thus maintaining the wooden pole arc. Therefore, wooden crossbars should be used to meet the actual situation to ensure that the average electric field strength of the plates meet the basic requirements. Only in this way can the actual safety of the wooden pole line be ensured and no tripping problems caused by lightning will occur.

(2) Use of insulating facilities

The first thing to note in the lightning protection countermeasures for distribution line operation is the use of more lightning protection materials and lightning arrestors. Insulation materials, as an important measure of lightning protection, play an important role in the prevention of lightning accidents, and to a certain extent, the impact of lightning accidents can be reduced to a large extent. At present, the distribution line itself is complex, and the line contains many metal materials, therefore, only by strengthening the insulation capacity of the distribution line can the lightning strike accidents be prevented. To this end, the relevant personnel should carefully check the insulation capacity of the distribution lines, promptly maintain the insulation materials that have been aged, and select suitable insulation materials for replacement. In addition, some insulating facilities (such as lightning arresters, etc.) should be installed in time. Lightning arrester has the features of good lightning protection and easy installation, which can well prevent lightning strike accidents. But just like the insulation materials on the distribution lines, the lightning arrester is also the facility that is easy to age. Therefore, it not only needs to carry out the corresponding maintenance work on the lightning arrester, but also needs too set up with the lightning arrester to match the part of the facilities and strengthen the role of the lightning arrester.

4. Conclusion

In summary, the lightning blockage and tripping phenomenon of the aerial insulation cable has a great impact on the whole power system, and the whole supply and distribution system may have various failures, so the electrician concerned should effectively prevent the lightning strike of the aerial line and choose the appropriate lightning protection device to further ensure the safety of the cable distribution line.