Common problems and preventive measures of overhead insulated cables

Overhead insulated lines, also known as overhead insulated cables, with the development of society and economy, overhead insulated cables are a new type of wire developed in the construction of urban power grids in recent years. Compared with ordinary overhead bare wires, they have many advantages. It solves some problems encountered in the operation of ordinary bare wires, and the price is relatively cheaper than that of direct buried cables. Therefore, it is widely used in the transformation of urban power grids and agricultural power grids.

With the further development and construction of the distribution network, the line construction is getting longer and longer. Overhead insulated lines often have potential accidents such as lightning breakage or water ingress oxidation of overhead insulated lines during the thunderstorm season, which greatly reduces the health level of the line and the reliability of line power supply, which increases the work difficulty of distribution line operation and maintenance personnel. Before we talked about the precautions for overhead insulated cables, let’s continue to understand what other common problems?

Problems Existing in Overhead Insulated Cables

1.Frequent lightning accidents

In the construction of the distribution network, most builders only consider the improvement of the insulation rate of the line and the contradiction with the tree line, but ignore the lightning protection problem of the overhead insulated cable, which has a certain impact on the safe operation of the line.

The reason why overhead insulated cables are easy to disconnect is that when lightning strikes the cable, the insulating layer will form a barrier to the movement of the arc generated by the lightning, resulting in slower moving speed of the arc, making the power frequency arc concentrated at the damage point of the insulating layer. When the direct lightning strike or induced lightning strike destroys the insulating layer of the insulated cable, its arc current will cause a phase-to-phase short circuit. Since the arc position is fixed, the insulated cable is more likely to break after a loud lightning strike than the bare wire. In addition, the insulators on the line will also flashover or burst due to lightning strikes, and even cause accidents such as wire fuses.

2.Insulation water, wire oxidation

During the construction of insulated cables, the insulation layer at the line terminal, interface and cutout is not insulated or the insulation is not properly treated. Water enters the wire and gathers at the lowest point of the sag. Due to environmental pollution and other factors, especially the rainwater in the chemical industry area is acidic, it reacts with the aluminum conductor to form white powder. This kind of oxide accelerates the corrosion of the cable under the action of the electric field, reducing the strength of the cable and forming an insulating layer. Swelling phenomenon, even disconnection, shortens the life of the cable.

3.Material selection

In the selection of auxiliary materials for insulated cables, the requirements for the use of insulated cables are not strictly followed. In order to reduce capital investment, the relevant materials used for overhead bare wires are used instead, which seriously affects the safe use of overhead insulated cables and speeds up the insulation of cables. aging and oxidation corrosion of the internal aluminum conductor.

4.Construction technology

In the process of unwinding and tightening the cable, the pulley is not selected according to the specified requirements, which will cause damage to the cable insulation layer and even cause a disconnection accident when the cable is tightened. During the installation of overhead insulated cables, a few irregular construction methods caused the cables to enter water and the cables to slip out of the clamps. Cable vibration fatigue, local heating, etc. Affect the safe operation of the cable and shorten the service life of the cable.

Frequently Asked Questions Preventive Measures

1.Strengthen lightning protection measures for medium voltage lines

In the construction and renovation of electricity, whether it is a new line or a line renovation, it is necessary to pay attention to the lightning protection measures of the overhead insulation ground, and you can choose to install lightning arresters or protection gaps.

2.Enhanced construction process specifications

In the erection of overhead insulated cables, the weather with dry temperature is selected for laying out, and plastic pulleys or aluminum pulleys with rubber sheaths should be used when tightening the wires. During the laying process, construction specifications should be strengthened to avoid unnecessary failures.