Line type synthetic insulated zinc oxide arrester manufacturer is used for lightning protection of transmission lines
In recent years, due to the continuous deterioration of environmental conditions, transmission line failures caused by lightning strikes have also increased, which not only affects the normal operation of equipment, but also greatly affects daily production and life. In the past few years, it was mainly concentrated in the southern mountainous lines. In recent years, there has been a trend of moving to the northern plains. Lightning strikes have become the most important factor affecting the safe and reliable operation of transmission lines.
In order to reduce lightning strikes on transmission lines, various comprehensive lightning protection measures have been taken, such as reducing tower grounding resistance, improving line insulation levels, using negative angle protection, and erecting coupling ground wires, etc., and have achieved certain results. However, for some lines distributed in high soil resistivity, it is difficult to reduce the ground resistance of towers, and there are still no good countermeasures to prevent and cure line faults caused by shielding lightning.
At present, line-type synthetic insulated zinc oxide arresters have been widely used abroad for lightning protection of transmission lines, and have achieved good results.
1. Basic principles of lightning protection for line arresters
When lightning strikes a tower, part of the lightning current flows to the adjacent tower through the lightning protection wire, and the other part of the lightning current flows into the earth through the tower. The ground resistance of the tower shows transient resistance characteristics, which is generally characterized by impact ground resistance.
When lightning strikes the tower, the potential at the top of the tower increases rapidly, and its potential value Ut=iRd+L.di/dt
When the difference between the tower top potential Ut and the induced potential U1 on the wire exceeds 50% of the discharge voltage of the insulator string, a flashover from the tower top to the wire will occur. That is, Ut-U1>U50. If the influence of the line power frequency voltage amplitude Um is considered, it is Ut-U1+Um>U50. Therefore, the lightning resistance level of a line is related to three important factors, namely the 50% discharge voltage of the line insulator, the lightning current intensity and the impact ground resistance of the tower. Generally speaking, the 50% discharge voltage of a line is certain. The intensity of lightning current is related to the geographical location and atmospheric conditions. Without the installation of lightning arresters, to improve the lightning resistance level of transmission lines is often to reduce the grounding resistance of the tower. In mountainous areas, reducing the grounding resistance is very difficult, which is why transmission lines are frequently struck by lightning.
After installing a lightning arrester, when the transmission line is struck by lightning, the shunt of the lightning current will change. Part of the lightning current will be transmitted from the lightning protection line to the adjacent tower, and part of it will go to the ground through the tower body. When the lightning current exceeds a certain value, the arrester will operate to join the shunt. Most of the lightning current flows from the arrester into the conductor and propagates to the adjacent tower. When the lightning current flows through the lightning protection wire and the wire, due to the electromagnetic induction between the wires, coupling components will be generated in the wire and the lightning protection wire respectively. Because the shunt of the arrester is much larger than the lightning current shunted from the lightning protection wire, the coupling effect of this shunt will increase the potential of the wire, making the potential difference between the wire and the top of the tower smaller than the flashover voltage of the insulator string, and the insulator will not flashover. Therefore, the line arrester has a good potential clamping effect, which is also an obvious feature of the line arrester for lightning protection.
In the past, lightning protection for transmission lines mainly used the method of reducing the grounding resistance of the tower body, which is relatively easy in plain areas. For towers in mountainous areas, longer radiating ground wires are often used at the four tower feet or deep wells are added with resistance reducing agents to increase the contact area between the ground wires and the soil and reduce the resistivity. The grounding resistance will decrease under power frequency conditions. However, when struck by lightning, the grounding wire is too long and will have a large additional inductance value. The transient component L.di/dt of the lightning overvoltage will be added to the potential of the tower body, greatly increasing the potential at the top of the tower. It is more likely to cause flashover between the tower body and the insulator string, which will instead reduce the lightning resistance level of the line. Because the line arrester has the function of clamping the potential, the requirements for grounding resistance are not too strict, and lightning protection for mountainous lines is relatively easy to achieve. After installing the arrester, it is not difficult to find that the lightning protection effect of adding the line arrester is very obvious.
2. Selection, installation and maintenance of arrester manufacturers
There are two types of line arresters, namely with series gap and without series gap. Due to different operating modes, the structural design is also different from power station arresters.
When installing line arresters, you should pay attention to:
(1) Select transmission line towers with many minefields and prone to lightning strikes. It is best to install them on adjacent towers on both sides at the same time;
(2) Vertically arranged lines can only be equipped with upper and lower phases;
(3) Try not to stress the arrester during installation, and pay attention to maintaining a sufficient safety distance;
(4) The arrester should lay a separate grounding wire along the pole tower, with a cross-section of not less than 25 mm2, to minimize the influence of grounding resistance.
Carry out necessary maintenance after putting into operation:
(1) Measure insulation resistance regularly in conjunction with power outages, and the results over the years should not change significantly;
(2) Check and record the action of the counter;
(3) Tighten its fasteners to prevent loosening;
(4) Take it back after 5 A and conduct a leakage current measurement at 1 mA DC and 75% reference voltage.
Yichang Hengyuan Technology Co., Ltd. specializes in the production of European-style cable joints, plug-and-pull heads, cable branch boxes, American-style elbow joints, high-voltage vacuum circuit breakers, high-voltage load switches, arresters, zinc oxide arresters, tank arresters, over-voltage protectors, counters, monitors, heat-shrinkable cable accessories, Manufacturer of cold shrink cable accessories, T-heads, wall bushings, European cable accessories, American cable joints, transformer neutral point protection devices, fuses, isolating switches, PT cable heads, elbow cable joints, 10kV outdoor terminals, switch cabinets, cable intermediate joints, cable accessories and other products
