Views:259 Author:Site Editor Publish Time: 2020-11-24 Origin:Site
Transmission lines are generally divided into cable lines and overhead power lines. The probability of a cable line tripping is small. Once a failure occurs, it is mostly permanent, so no automatic reclosing device is installed. Overhead electric lines are greatly affected by external conditions, such as bad weather and overlapping branches, which are prone to failures, and most of them are instantaneous. Therefore, automatic reclosing devices are generally installed. The practice has proved that after the overhead distribution line trips, the success rate of reclosing is very high, which greatly reduces the number of power outages to users. Here are the main causes of line failures.
Wind power exceeding the mechanical strength of the tower will cause the tower to be distorted or damaged, making the wire vibrate, jump and hit the wire.
Drizzle can cause dirty insulators to flashover and even damage the insulators. When heavy downpours continue for a long time, the river will surge or flash floods will cause pole down accidents.
When the overhead line conductors and lightning protection lines are seriously iced, the first is to increase the mechanical load of the conductors and the towers, so that the sag of the conductors is excessively increased, resulting in mixing or disconnection; when the icing on the upper surface of the conductors and lightning protection lines falls off, it will cause the wire and lightning protection wire to jump, thus causing a line mixing accident. In addition, because too much ice and snow accumulate on the porcelain bottle or the cross arm, the flashover accident of the insulator is caused.
Not only flashover or breakdown of insulators, but also accidents such as wire breakage or splitting of wooden poles or wooden cross-arms.
Birds build nests on poles or stop on poles, and sometimes big blacks fly through wires, which may cause accidents such as short circuit and earth fault.
In industrial areas, especially chemical areas or other polluted areas, the dust or harmful gases generated will significantly reduce the insulation level of insulators, leading to flashover accidents.
When the air temperature changes, the tension of the wire also changes. In the hot summer, due to the elongation of the wire, the sag becomes larger, which may cause a discharge accident at the crossover; while in the cold winter, the wire shrinks, the sag becomes smaller and the stress increases, which may cause a disconnection accident.
There are many other reasons for line accidents, such as accidents affected by external forces, flying kites near the line, shooting birds and shooting guns near the line, digging near the foundation of the tower, and tall trees near the line. These will affect the normal operation of the line and may also cause serious accidents. However, as long as we strictly implement various operation and overhaul systems, earnestly perform maintenance and overhaul work, and earnestly implement various anti-accident technical measures, we can ensure the safe operation of overhead power distribution. The above-mentioned various accidents can be avoided. To find out types of short circuit, we can use the advanced cable fault indicator, the ground fault indicator or the arc fault indicator, which are useful tools in the power system.