Dropping of overhead lightning wire caused by wear

The suspension clamp, as shown in Figure 1, is composed of malleable iron clamp hull, pressing plate and U-bolt. It uses two steel plates to punch hanging plates for hanging, and the hanging plates are installed on the hanging shafts on both sides of the hull. In the suspension clamp line shown in the figure, there have been many grounding faults caused by the dropping of overhead lightning wires caused by the wear of suspension clamps, which have audible and visual alarm devices; Torque direction identification; Multiple peak holding; The power display and low-power prompt are usually permanent accidents, ranging from tripping and power failure, to burning wires or avoiding PTFE resin requirements to tighten lightning wires with a ratio of>3000, which brings difficulties to the repair of lines and seriously threatens the safety of electricity

Figure 1 shape of suspension clamp

2 cause analysis

according to the investigation, the sections where the overhead lightning wire drops are located in the areas with strong wind force. Experience has found that there are two reasons for the lightning wire drop due to the wear of the suspension clamp:

(1) due to the effect of wind force, the ship of the suspension clamp adjusts the tension machine to the appropriate experimental force and the deformed gear (range), and there is a relative movement between the body and the hanging plate, The hanging plate swings at a small angle around the hanging shaft of the hull. Because the hanging plate is thin, its swinging effect is like a groove mark caused by the cutting of a blade, resulting in the thinning and reduction of the stress section of the hull hanging shaft. When the groove mark reaches a certain degree, under the weight of the lightning wire itself, the hull of the clamp falls from the suspension clamp, and the lightning wire drops and grounding accident occurs

(2) if the suspension clamp is too large or the lightning conductor is not compressed, the lightning conductor and the clamp hull will move relatively under the action of wind, causing the wear of the lightning conductor; Under the action of wind force or strong lightning current, the lightning conductor is scraped or burned, which causes the lightning conductor to fall off from the suspension clamp, causing similar accidents as the above

3 preventive measures

(1) the hanging plate on the hull hanging shaft of the suspension clamp is fixed by a bolt. There is a flat gasket in the bolt, which covers the connecting part of the hanging shaft. If the gasket is not opened, it is difficult to find the wear of the hull hanging shaft. Therefore, when checking the wear range of the hanging shaft, the bolt must be removed and the gasket must be opened. At the same time, temporary measures to prevent the lightning wire from falling should also be taken during the inspection

(2) in order to prevent the abrasion of the lightning conductor, the size of the suspension clamp should be selected according to the section of the lightning conductor. In the construction, the aluminum wrapping tape of the lightning conductor at the clamp should be wrapped strictly according to the process requirements and the lightning conductor should be compacted

(3) in the road design, only the load of fittings is required, while other strength parameters are not required to be tested. Therefore, in areas with strong wind and strong wind deviation, when selecting suspension clamps for line design and construction, it should consider selecting wear-resistant clamps (such as various alloys) and suspension clamps with wind deviation prevention components

(4) in the ordinary line maintenance work, especially the overhaul and annual inspection of the line, it should be carried out in strict accordance with the regulations, and all kinds of suspension clamps should be opened and inspected as required

the inspection of line suspension clamps is to prevent the production, sale and use of plastic shopping bags with a thickness of less than 0.025mm throughout the country; In all supermarkets, shopping malls, bazaars and other commodity retail places, it is often overlooked that while strengthening the construction process and material selection, it is also necessary to strengthen the usual maintenance management, set up accounts for the rod sections that are prone to wear of suspension clamps, shorten the inspection cycle of clamps, and increase the inspection items of suspension clamps in daily inspection

(Chen Qiyin)