Application effect of line lightning arrester manufacturers on line lightning protection
In order to reduce the damage caused by lightning strikes to the transmission line, the line lightning arrester is installed in the vulnerable section of the transmission line to improve the lightning resistance level of the line. In view of this, the basic principles of line lightning arrester lightning protection and the preparation work before installation are introduced. In recent years, some lightning arresters that have been connected to the network have been tracked and analyzed. Since the original multi-lightning pole tower was installed with line lightning arresters with series gaps, there has been no lightning trip on the tower so far.
In order to reduce the impact of lightning strikes on the safe operation of transmission lines, a variety of lightning protection measures are usually taken, mainly including: reducing the grounding resistance of the tower; erecting lightning protection wires; increasing the line insulation level; installing coupled ground wires and so on. However, no effective solution can be found to prevent the lightning protection of the line poles and towers from the influence of the shielding lightning on the line and the high soil resistivity. For this reason, it is urgent to adopt some new technical measures to improve the lightning resistance level of the line towers to reduce the lightning trip rate.
With the application and development of synthetic insulating materials in lightning protection technology, many countries such as the United States and Japan have installed lightning arresters in the vulnerable sections of transmission lines to improve the lightning resistance level of the line and reduce the lightning trip rate.
1. The basic principle of line lightning arrester lightning protection
For a tower with a general height, the lightning resistance level of the line is mainly related to four factors: the 50% discharge voltage of the line insulator; whether there is an overhead ground wire; the lightning current intensity; the ground resistance of the tower. The 50% discharge voltage of the insulator is fixed, and the lightning current intensity is related to the geographical location and climatic conditions. When the lightning arrester is not installed, the improvement of the lightning resistance level of the transmission line is often to use the overhead ground wire and reduce the grounding resistance of the tower. In mountainous areas, it is very difficult to reduce grounding resistance, and shielding strikes are prone to occur. This is why the lightning strike rate of transmission lines in mountainous areas is high.
The line arrester is connected in parallel with the line insulator. When lightning strikes, the arrester will act, and the residual voltage of the arrester will be lower than 50% of the discharge voltage of the insulator string. Even if the lightning current increases, the residual voltage of the arrester will only increase slightly, and the insulator will not flashover. After the lightning current passes, the power-frequency freewheeling current flowing through the arrester is only milliamps. The power-frequency freewheeling current flowing through the arrester is extinguished at the first zero crossing, the circuit breaker will not trip, and the system returns to the normal state. Figure 1 illustrates the matching relationship between the volt-second characteristic of the line arrester and the volt-second characteristic of the insulator. During a shielding strike, the volt-second characteristic of the arrester is more than 15% lower than the volt-second characteristic of an insulator, and it can be lower than that of an insulator by more than 20%.
2. Preparatory work before installation of line arrester
The line arrester is mainly used to reduce the lightning trip rate of the transmission line, not to limit the operating overvoltage. Therefore, the line arrester should be of a series gap type, and preparations must be made before installation.
2.1 Carry out the specified electrical test
The manufacturer of the arrester shall carry out the specified electrical test before installation and commissioning. Measure the insulation resistance, the voltage U1mA at DC 1 mA, and the leakage current at 75% U1mA. The measurement results should not change significantly compared with the factory data, and should comply with the regulations. During the installation process, install the series gap as required. After installation and commissioning, check and record the action of the counter so that other lines can be analyzed and compared in the future.
2.2 The fixed-point principle for installing line arresters
a) Operating experience of the line. Analyze the operation of the line since it was put into operation to determine the towers that are vulnerable to lightning strikes, and analyze to determine whether it is a bypass attack or a counterattack.
b) Topography, geomorphology and neighboring influences along the route. On-site survey of the sections that the route passes, especially the sections that pass through fish ponds, rivers and mountains, etc., should be analyzed, and the sections that may be struck by lightning on the line towers due to terrain and geomorphic conditions should be recorded. Generally, the poles and towers passing through this section are given priority.
c) The grounding resistance of the tower and the distance between adjacent towers. According to the grounding resistance requirements and actual grounding resistance values of the designed poles and towers when the line is put into operation, the poles that do not meet the grounding resistance design requirements are determined and modified, and priority is given to those that cannot meet the requirements due to geological conditions.
d) Based on the analysis of the above factors, combined with traffic conditions, determine the best location for installation of line arresters.
Yichang Hengyuan Technology Co., Ltd. is a professional manufacturer of European-style cable connectors, plug connectors, cable branch boxes, American elbow connectors, high-voltage vacuum circuit breakers, high-voltage load switches, lightning arresters, zinc oxide arresters, tank arresters, overvoltage protectors, Counters, monitors, heat-shrinkable cable accessories, cold-shrinkable cable accessories, T-shaped heads, wall bushings, European cable accessories, American cable joints, transformer neutral point protection devices, fuses, isolating switches, PT cable heads, elbows Manufacturers of type cable joints, 10kV outdoor terminals, switch cabinets, cable intermediate joints, cable accessories and other products
