CN103956705A - Full-coverage-type lightning protection device for overhead transmission lines - Google Patents

Abstract

A full-coverage lightning protection device for overhead power transmission lines, including three lightning protection wires arranged above and parallel to the power transmission lines: the middle lightning protection wire is located directly above the middle power transmission line , the left and right lightning conductors are symmetrically arranged, and the protection angle α of the left lightning conductor to the left transmission line is 0°. The device has no dead angle and more comprehensive lightning protection for three-phase transmission lines, and has the characteristics of low reconstruction cost, convenient construction and more reliable lightning protection.

Description

Full-coverage lightning protection device for overhead transmission line

technical field

The invention relates to a lightning protection device, in particular to an improved and full-coverage lightning protection device for overhead power transmission lines.

Background technique

Thundercloud discharge causes lightning overvoltage in the power system, or atmospheric overvoltage.

There are two common overvoltages in overhead lines: the first is the overvoltage caused by lightning strikes near the overhead lines, and the overvoltage on the transmission line through electromagnetic induction; the second is the overvoltage generated by lightning directly hitting the wires. There are three specific situations:

1. Lightning strikes the top of the tower; 2. Lightning strikes the space part of the lightning conductor; 3. Bypassing the lightning conductor and striking the wire.

Lightning strike faults are divided into two types according to their nature:

1) Recoverable: after the lightning flashover occurs, due to the recovery of the air insulation strength, the reclosing switch is successfully put into operation;

2) Permanent: due to serious faults such as insulator falling off and wire breaking, the reclosing switch fails.

Lightning strikes will cause different forms of damage and damage to electrical facilities, as follows:

Overvoltage caused by lightning may cause damage to insulators and transmission lines, so it will generally cause reclosing protection action.

Lightning strikes will cause insulators to flashover and discharge, causing burns and falling off on the porcelain surface; causing network cracks to glass insulators; causing melting marks to iron parts, etc., which will greatly reduce the insulation strength.

Lightning strikes on the transmission line or lightning protection line may cause broken strands or even rupture, making the power transmission work impossible.

When lightning strikes the concrete tower grounded through the internal iron core, the strong lightning current may cause the pole body to burst and cause the main grid to trip.

The above damage may cause protection action, alarm or trip outage, so the harm is very great.

Lightning is an important factor affecting the safety of transmission lines, and has long occupied the first place in line fault tripping. Lightning is a natural process of atmospheric activity, which has not been controlled so far. But we can analyze the frequent accidents, look for the law of lightning strikes, and strengthen prevention, which can be done. Key records vulnerable to lightning damage are as follows:

1) Towers in the mid-mountains or peaks of high mountains;

2) Power transmission lines near ponds and reservoirs;

3) Large-span towers, such as towers spanning mountains or rivers and lakes over 800 meters;

4) Installed on towers with high grounding resistance, such as rock tower foundations and power lines.

The lightning conductor is the most effective and basic measure for the protection of the transmission line. The lightning conductor can prevent the lightning from directly hitting the wire, and also has a shunt function to reduce the lightning current flowing through the tower.

Figure 1-A and Figure 1-B are two common high-voltage transmission lines and iron tower structures, in which Figure 1-A is an owl type, and the transmission lines are arranged in a triangle; Figure 1-B is in the form of horns, and the transmission lines are arranged horizontally . The serial numbers in Figure 1-A and Figure 1-B are the same, 1 is the iron tower, 2 is the transmission line, 3 is the insulating porcelain bottle, and 4 is the lightning protection wire.

Taking the original 220kV transmission line as an example, double lightning protection wires are generally used for this voltage level, and grounded at each base pole, as shown in the upper right corner of Figure 1-A and Figure 1-B, and the protection angle α of the lightning protection wire to the conductor is less than or equal to 25° .

The protection range of the two equal-height lightning conductors of the 220kV transmission line is shown in Figure 2.

The circular protection angle range of the lightning conductor is determined by the following formula:

rx=ha=(h-hg)p

Figure 2 and the marks in the formula: h is the height of the lightning conductor, ha is the distance from the ground wire to the transmission line, hg is the height of the conductor to the ground, D is the horizontal distance between the two lightning conductors, α is the protection angle of the lightning conductor, and P is the height Correction factor.

On the overhead transmission line, the protection range of the lightning conductor is shown in Figure 1-B and Figure 2, which is represented by the protection angle α. The protection angle is the angle between the plumb line of the lightning conductor and the lightning conductor and the side conductor. Obviously, in theory, when α is smaller, the probability of lightning strikes the wire is lower, and the shielding protection of the wire by the lightning conductor is more sufficient and reliable. However, in reality, if α is too small, the transmission line will break away from the protection range of the lightning conductor when it swings with the wind.

Let us give an example to illustrate: in Figure 2, in the 220kV transmission line according to the conventional layout, the tower height h is about 20 meters, the distance D between the two lightning protection lines is 5 meters, and the distance ha between the lightning protection line and the transmission line is 5 meters. The distance between two adjacent transmission lines is 4.5-5 meters, the protection angle is 25°, and the tangent value of tgα is verified to be 0.4663. From this, the length of the offset distance x of the transmission line can be calculated as:

x = tgα ha = 0.4663х5 = 2.33 (meters);

Because the line spacing, ground wire spacing, protection angle, etc. are all correspondingly regulated, the calculation formula and calculation results of the x value have special significance, which makes it a reference and compliance basis for design and installation. Otherwise, it is easy to ignore in work, and once this data is exceeded, that is, the offset and excessive expenditure, it will be outside the protection angle of the lightning conductor, which will aggravate the lightning overvoltage and increase the number of trips, etc. Full attention.

In Fig. 2, the left lightning protection line is located at the upper right of the left transmission line, and the right lightning protection line is located at the upper left of the right transmission line.

The existing lightning protection methods still have defects, such as improper size matching, etc., which still cannot meet the needs of lightning protection.

Figure 3 is a complete supplementary diagram of the three phases A, B, and C of Figure 2. A few points can be seen from Figure 3:

1. Phase A and Phase C are within the protection angle of 25°lightning conductors, while phase B is covered by the intersection of lightning conductors, but strictly observed, it is outside the protection angle;

2. In high mountains and rivers and lakes, power poles and towers often have large spans, heavy sag of transmission lines, and the largest swing with the wind. The wires are usually within the protection angle, but they may exceed the protection range under strong winds;

3. Rivers and lakes are unobstructed and unobstructed. Lightning can strike directly, obliquely, and violently, and strike towers and power lines from different directions.

Therefore, the above are the most severe lightning strikes, the most severely damaged power facilities, and the highest trip rate. That being the case, why can't we break through the existing structure of double lightning conductors and take necessary improvement measures.

Contents of the invention

The purpose of the present invention is to provide a full-coverage lightning protection device for overhead transmission lines, so that the left and right transmission lines will not deviate from the protection range of the lightning protection line when they swing, and the middle transmission line will not be outside the protection range of the lightning protection line .

The purpose of the present invention is achieved in this way: a full-coverage lightning protection device for overhead power transmission lines, including lightning protection wires arranged above the power transmission lines and parallel to the power transmission lines. There are three lightning protection wires: one lightning protection wire in the middle It is located directly above the transmission line in the middle, and the left and right lightning protection lines are arranged symmetrically. Among them, the protection angle α of the left lightning protection line to the left transmission line is 0° (that is, the left lightning protection line is located on the left directly above a power line).

When the transmission line is 220kV, the protection angle α is 0°, the vertical distance between the left lightning protection line and the left transmission line is 5m, and the distance between two adjacent transmission lines is 4.66m.

The beneficial effects of the present invention are: the device increases the original two lightning conductors to three, as shown in Figure 3, the position of the left lightning conductor is moved from ① outside to be perpendicular to ③, and the position of the right lightning conductor is moved from ② outside Move to the position perpendicular to ④, vacate the position of a lightning protection line in the middle, and add a third lightning protection line perpendicular to B to form a new lightning protection structure, as shown in Figure 4. In this way, there is no doubt that the lightning protection angle Expansion, the protection range is widened, there is no dead zone, and the wire is still within the lightning protection range when the wire is blown by the wind, so it has a good protection against lightning strikes from multiple directions. The transformation is easy and the construction difficulty is low.

Whether it is an iron tower or a concrete pole, the original metal cross-arm is lengthened, and the position space is fully allowed. Whether it is replacement or welding, there is no technical difficulty, and the investment in funds is very small, but it can play a significant role. Reduced by more than half, the lightning protection function has reached a new level! It has certain flexibility to the existing lightning protection system.

The lightning protection line is a regional work, unlike the transmission line that requires continuity and penetration, so it is optional to increase or not. For example, we can increase the number of lightning protection lines to three lightning protection lines in high mountains and rivers and lakes where there are many lightning strikes, severe lightning strikes, and a high tripping rate. In plains, places with small spans and few lightning strikes, we can also maintain two lightning protection lines. Has a structural state. This kind of flexibility is conducive to adopting different solutions for different environments and different needs, so it is another functional feature that can be taken and put down.

This device has done some unique and beneficial work in the conventional lightning protection, such as for areas with high grounding resistance, it proposes the treatment method of using coupling type and grounding grid, and at the same time, fully considers The protection angle range provides the tangent calculation formula to determine the offset length of the wire. In the lightning-prone areas of mountains and lakes, a new measure of adding three lightning protection lines was proposed to expand the protection range. These have great practical value, effectively improve lightning protection technology, and greatly enhance the safe operation level of high-altitude cables.

Description of drawings

Fig. 1-A and Fig. 1-B are schematic diagrams of lightning conductor arrangement in the case of triangular arrangement and horizontal arrangement of transmission lines respectively.

Fig. 2 is a schematic diagram of the lightning protection angle shown in Fig. 1-A and Fig. 1-B.

Fig. 3 is a schematic diagram of lightning protection protection for the three-phase transmission line shown in Fig. 1-B.

Figure 4 is a schematic diagram of the arrangement of lightning conductors and the protection range of the device.

Detailed ways

Figure 4 shows a full-coverage lightning protection device for overhead transmission lines, including a lightning protection line 4 arranged above the transmission line and parallel to the transmission line. There are three lightning protection lines 4: the middle lightning protection line is located in the middle Directly above a power transmission line, the left and right lightning protection wires are arranged symmetrically. Among them, the protection angle α of the left lightning protection wire to the left power transmission line is 0° (that is, the left lightning protection wire is located at the left one directly above the transmission line); the protection angle α of the right lightning protection line to the right transmission line is 0° (that is, the right lightning protection line is located directly above the right transmission line). When the transmission line is 220kV, the protection angle α (normally 20-30°) is improved to 0°, the vertical distance between the left lightning protection line and the left transmission line is 5m, and the distance between two adjacent transmission lines The distance between them is 4.66m (2x calculated value). The lightning conductor on the left moves 2.33m horizontally from the original position in Figure 2 to the left.

Figure 4 shows that after the transformation of the three lightning conductors, it is obvious that the protection range of the transmission line is enlarged across the arc as shown in the figure, and there is no dead zone.

After the improvement of the three lightning conductors, because the protection angle is 0°, the protection range increases, so a new feature is produced: the distance between the A, B, and C three-phase transmission lines can not be changed before (the protection angle is 25°), the calculated value of 4.66m can be taken as an integer of 5m, etc., so that it becomes looser, more convenient and more flexible in terms of blanking, assembly and production.

Claims (2)

1. A full-coverage lightning protection device for overhead transmission lines, comprising a lightning protection line (4) arranged above the transmission line and parallel to the transmission line, characterized in that there are three lightning protection lines (4): one in the middle The first lightning protection wire is located directly above the middle transmission line, and the left and right lightning protection wires are arranged symmetrically. Among them, the protection angle α of the left lightning protection wire to the left transmission line is 0°. 2. The full-coverage lightning protection device for overhead power transmission lines according to claim 1, characterized in that, when the power transmission line is 220kV, the protection angle α is 0°, and the lightning protection line on the left side is connected to the power transmission line on the left side. The vertical distance of the line is 5m, and the distance between two adjacent transmission lines is 4.66m.