What are the typical faults in overhead lines, and why do they occur?

Electrical line failure may lead to electric shock, fire, power outages, and many other accidents.

Below is a brief analysis of the common faults of electrical lines by ZMS cable.

Overhead Line and Cable Line Faults

Overhead Line Faults

Short circuit and damage to the wire

The causes of the short circuit and damage to the wire are:

a. Wire distance between the line is small, the verticality of the three-phase wire is different, encounter wind scraping, easy to trigger the phase between the phase touch short circuit. And burn the wire.

b. Tree branches, and metal objects falling on the line; crane operation accidentally touching the line, will also cause a short circuit and damage to the wire.

c. By the long-term corrosion of harmful gases in the surrounding environment, the effective cross-section is reduced.

Wire damage is not very serious, and can be used as appropriate to dress the line repair method to give treatment.

Wire Joints Overheating

The causes of overheating of the wire joints are.

a. Wire load current more than the maximum allowable value of the wire cross-section.

b. Wire joint construction work quality could be better.

c. The line suffered long-term wind and rain, oxidation and corrosion are becoming increasingly severe, and the contact resistance of the joint becomes large, affecting the heat.

Found that the wire overheating, you can try to reduce the load. Continue to monitor the operation, and according to the development of the situation. Arrange to deal with.

Cable Line Failure

In terms of the phenomenon, cable failure contains mechanical damage, aluminum skin cracking, swelling, terminal contamination, insulation breakdown, metal sheath corrosion holes, and other faults.

In terms of cause, cable failure contains external damage, chemical or electrical corrosion, lightning, flooding, improper construction, improper maintenance, and other faults.

Common cable failures and prevention methods are as follows:

Plastic Cable Into The Water

Because once the plastic is invaded by water, the insulation aging phenomenon is prone to occur, especially when the conductor temperature is high, the conductor of water caused by the infiltration of aging is more serious.

So the transportation, storage, laying, and operation of plastic cables are not allowed into the water.

Cable Overload Operation

The safety of cable operation has a close relationship with its load capacity, overload will increase the accident rate of the cable, but also shorten the service life of the cable.

The cable damage caused by overload is mainly the following aspects:

Cause Damage To The Wire Joints

b. Accelerate the aging of the cable protection insulation.

c. Make the cable lead package expansion, and even cracking phenomenon.

Such as poor manufacturing quality, and poor installation conditions of the cable under long-term overload will cause lead pack fatigue, cracking expansion, and cracking phenomenon.

d. Make the cable terminal head swell and crack with asphalt insulation rubber.

Damaged By An External Force

A considerable part of accidents on the cable itself is caused by external mechanical damage.

When constructing near the cable line, prompt the construction workers to pay special attention to this point and, if necessary, take protective measures.

Cable Termination Head Casing Contamination

The main measures are regular cleaning of the casing, preferably under blackout conditions, for thorough cleaning.

In areas with serious fouling, the cable terminal head casing should be coated with antifouling paint, or the insulation level of the casing should be increased appropriately.

Water Explosion In The Outdoor Terminal Head

Mainly due to improper construction and maintenance, resulting in the terminal head condensation water agglomeration in the cable head, eventually leading to insulation moisture breakdown, causing an explosion.

Cable Intermediate Joint Explosion

Most of the overload is caused by the expansion of the insulating rubber in the joint box and expansion of the cracked shell, or poor conductor connection so that the joint overheating and explosion.

Analysis of the causes of line failure

Insulation Damage

Insulation damage may occur depending on the degree of damage in the following two situations:

Short Circuit

Complete damage to the insulation will result in a short circuit.

Short circuit when the current flowing through the line increases from the average working wind of several letters to dozens of times, and the wire heating and current square proportional to the heat, resulting in a sharp increase in heat, a short time that may start a fire burning.

Such as short circuit arc discharge, the high-temperature arc may burn the adjacent staff, and may also directly cause combustion.

In addition, in the short-circuit state, some exposed conductors will carry a dangerous fault voltage, which may give a fatal electric shock.

Leakage

If the insulation is not completely damaged, it will lead to leakage, leakage is one of the most common causes of electric shock accidents.

On the other hand, local heating at the leakage.

The high local temperature may directly lead to fire, but also may further damage the insulation, forming a short circuit, caused by short circuit fire.

In addition, if the conductor grounding, due to the grounding current and short-circuit current difference is very far.

Although the line does not ignite by the heat generated by the grounding current, the local heat and arc at the ground can lead to fire combustion.

Severe Overload

Overload will accelerate the aging of insulation.

Such as too much overload or overload time being too long, which will cause the wire to overheat, bringing the risk of ignition.

In addition, the overload will also increase the voltage loss on the line.

The main reason for overload are two: First, the user has privately connected too much electrical equipment, which is caused by overloads.

Broken Wire

The broken wire may cause grounding, mixed wire, short circuits, and many other accidents.

Wire disconnection or pull off when the electric sparks and overhead line wire swing, jumping sparks may ignite the adjacent combustible combustion.

In addition, the three-phase line disconnected a phase will cause three-phase equipment asymmetric operation, which may burn equipment.

Neutral line disconnection may also cause the load three-phase voltage imbalance, and burned power equipment.

The above is about the common faults and fault protection measures for overhead cable lines.

Overhead cable laid in the air for a long time, the cable needs to be strong enough and withstand a certain amount of pulling to do, so be sure to choose high-quality qualified cable products, both safety, and save unnecessary trouble later.