JPH0515130B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for grounding an overhead ground wire installed on a power transmission tower, and more particularly, to a lightning protection method for a power transmission line.

<Conventional technology> Generally, one or two overhead ground wires are installed at the top of a power transmission line in an area where lightning occurs to prevent direct lightning strikes, that is, to prevent lightning strikes. It is normal to keep it.

This overhead ground wire is connected to the top of each steel tower whose legs are grounded, and by guiding the lightning charge through the tower body to the ground, it has the effect of shielding power lines from lightning.

However, when lightning current flows into the overhead ground wire, a potential difference is created between the overhead ground wire and the power line due to the resistance of the overhead ground wire and tower members, and if the dielectric strength between them is exceeded, the tower's insulator Reverse sparkle occurs in such cases.

For this reason, many lightning protection designs have been implemented so far, such as multi-stranded overhead ground wires, bridging of overhead ground wires, unbalanced insulation methods, and multiple grounding methods for buried ground wires, but none of them have been shown to be sufficiently effective. The reality is that we have not yet achieved this goal.

<Problem to be solved by the invention> This is because the wave front steepness of the lightning current is large, and the surge impedance of the overhead ground wire, steel tower, and buried ground wire acts, causing the potential to rise around the lightning strike point. Since the connections from the overhead ground wire to the tower, between the tower members, and from the tower to the buried ground wire are surface connections using bolts and metal fittings, lightning waves can cause reflection phenomena at these connections. However, this is caused by the fact that the lightning current does not propagate smoothly to the end of the buried ground wire.

Therefore, in order to solve the above problems,
Publication No. 12-7011 describes an overhead ground wire system in which an overhead ground wire insulated and installed on a steel tower is connected to a grounding plate independent of the tower with a grounding conductor that is electrically isolated from the tower. Disclosed.

In addition, Japanese Patent Application Laid-open No. 54-119693 discloses that an overhead ground wire insulated and installed on a steel tower is grounded with the core wire of a coaxial shielded cable, and the lower end of the conductive sheath of the cable is grounded. A protective device is disclosed.

However, in the former overhead ground wire device, the ground conductor is bent at an acute angle and connected to the overhead ground wire, and the ground conductors on both sides are connected in a Y shape and hang down as a single strip. Therefore, a reflection phenomenon of lightning waves occurs at each connection point, and since the lower end of the grounding conductor is installed on a grounding plate independent of the steel tower, terminal reflection of lightning waves occurs, and the grounding conductor is connected to the tower, Alternatively, there was a risk of a reverse flash fault occurring from the tower to the power line. In addition, because the distance between the grounding conductor and the tower body is large, the capacitance to the tower is small (wave impedance is large), and there is a risk of reverse flash faults from the grounding conductor to the tower, as well as the risk of the grounding conductor connecting to the power line. When applied to actual railway lines, there were difficult problems such as preventing interference due to electrostatic induction and electromagnetic induction and preventing lateral vibration due to wind pressure.

The latter protection device uses a coaxial shielded cable as the grounding conductor, so the wave impedance can be lowered, but when lightning waves with extremely high frequency characteristics flow through the cable, the current flows through the core wire due to skin action. It does not flow into the body, but flows through the exterior part. Also,
Due to the electromagnetic induction effect of the current, lightning surges were also diverted to the steel tower body, and there was a risk that a flash short to the power line would occur due to an increase in the potential of the steel tower.

In addition, since the overhead ground wire and the grounding conductor as well as the grounding conductors are connected with clamps, lightning waves are reflected at each connection point, causing a reverse flash fault from the cable to the tower, or from the tower to the power line. There was a fear that

<Means for Solving the Problems> The present invention has been made to solve the above problems, and the details thereof will be explained below using FIGS. 1 and 2, which correspond to embodiments.

Between the transmission line towers 3, there is an overhead ground wire 1 installed insulated from the tower 3 and whose end is grounded, and one end of the overhead ground wire 1 and one end of the adjacent overhead ground wire 1 are connected to the tower 3. A lightning protection method for a power transmission line connected by a jumper wire 6 passing above the top,
The above-mentioned overhead ground wire 1 has the above-mentioned overhead ground wire 1 at both ends thereof.
and a hanging line 4 integrally and continuously formed,
The hanging wires 4 are insulated from the steel tower 3, and are suspended along the main pillar material 3a of the steel tower 3, with their drooping ends connected to the buried ground wires 5. This is a lightning protection method for a power transmission line, characterized in that the tower legs are connected to the buried ground wire 5 to make the potentials of the hanging wire and the tower the same.

<Function> In this way, the overhead ground wire 1 is installed insulated from the steel tower 3, and each end is insulated from the steel tower 3 and buried via the hanging wire 4 arranged along the steel tower 3. connected to the ground wire 5, and the above-mentioned overhead ground wire 1
are installed in each predetermined span of the tower, and one end of each overhead ground wire 1 and one end of the adjacent overhead ground wire 1 are connected by a jumper wire 6 passing above the top of the tower 3. 1 to the ground GL, and the electrostatic capacitance between the hanging wire 4 and the steel tower 3 alleviates the lightning surge, and the lightning current is transferred from the overhead ground wire 1 to the hanging wire 4.
, to the buried ground wire 5, and to the ground GL without intervening the surge impedance of the steel tower 3.
This reduces the potential rise at the point of lightning strike.

Furthermore, since the hanging line and the grounding point of the tower are the same,
The direction of the falling current to the grounding point of the hanging line and the reflected current rising up the tower from the grounding point are opposite, and the two cancel each other out, suppressing the potential rise. Reverse flashover can be prevented.

<Effects of the Invention> The lightning protection method for power transmission lines according to the present invention is as described above, which reduces insulator reverse flashover of power lines due to lightning current, and prevents malfunctions of system protection relays, arresters, and circuit breakers due to overcurrent and overvoltage. This has a significant effect in reducing damage accidents and contributing to stabilizing the power supply.

<Example> An example of the present invention will be described below with reference to FIGS. 1 to 4.

The lightning protection method of the present invention includes an overhead ground wire 1, its retaining clamp 8, a retaining insulator 7, a hanging wire 4, its supporting insulator 9, a jumper wire 6, its supporting insulator 9, and a buried ground wire 5. It is carried out using

The overhead ground wire 1 is formed of a predetermined electric wire, for example, a steel-core No. I aluminum alloy stranded wire, or an aluminum-sheathed stranded wire.

This overhead ground wire 1 is held down on one side by a detention clamp 8 that is insulated and supported by a suspension insulator-like detention insulator 7 fixed to the steel tower 3, and similarly held on the other side. It is provided with a predetermined slack and is installed at a predetermined position above the power line 2 .

The hanging wires 4 are integrally and continuously formed at both ends of the overhead ground wire 1, and are curved downward from the retaining clamps 8 of the installed overhead ground wire 1, and arranged in a substantially hanging shape. ing.

Each hanging line 4 is supported by a required number of support insulators 9, and is connected to the main column 3a of each steel tower 3.
The lines are extended downwardly at predetermined intervals along the lines 4 and connected to buried ground lines 5 provided for each downward line 4.

The buried ground wire 5 is formed by burying a predetermined conductor underground around the legs of the three steel towers, and in the example,
Several 30m long conductors are buried in a radial pattern to provide low grounding resistance.

In addition, the above-mentioned overhead ground wire 1 and the overhead ground wires 1 for each of a predetermined number of tower spans installed in the same manner as described above are defined as the overhead ground wires 1 and 1 of the adjacent tower spans are connected to each other. The clamps 8, 8 are adjacent to each other by the jumper wire 6, and the adjacent overhead ground wires 1, 1 are formed in a good conductive state. The jumper wire 6 is supported at its intermediate portion by a support insulator 9 disposed at the top of the steel tower 3.

Further, the steel tower 3 is connected to the buried ground wire 5 at its tower leg.

The above explanation is for the case where there is one overhead ground wire between the tower spans, but even when there are multiple overhead ground wires between the tower spans, each overhead ground wire has a hanging line and a Of course, it is also possible to implement a lightning protection method for power transmission lines by providing a buried ground wire.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing one embodiment of the present invention, Fig. 2 is an explanatory diagram showing a tower span in which an overhead ground wire is installed, and Fig. 3 is an enlarged front view of the retaining clamp section of Fig. 1. , FIG. 4 is an enlarged sectional view of the hanging line support portion of FIG. 1. 1... Overhead ground wire, 3... Steel tower, 4... Drop line,
5...Buried ground line, 6...Jumper line.

Claims (1)

[Scope of Claims] 1. An overhead ground wire installed between the steel towers of a power transmission line insulated from the steel towers and whose end is grounded, and one end of the overhead ground wire and one end of the adjacent overhead ground wire. is a lightning protection method for a power transmission line in which the overhead ground wire is connected by a jumper wire passing above the top of a steel tower, and the overhead ground wire has hanging wires formed integrally and continuously with the overhead ground wire at both ends thereof. each of the hanging wires is insulated from the steel tower, hangs down close to the main column material of the steel tower, and has its hanging end connected to the buried ground wire, and is connected to the pedestal of the steel tower. A lightning protection method for a power transmission line, characterized in that the lower part is connected to the buried ground wire so that the potentials of the hanging wire and the steel tower are the same.