The cable fault tester under UHV power can help many power workers conduct various power tests more conveniently.

What are the causes of underground cable failures?

Nowadays, electricity has penetrated into people's lives, and power cable faults exist at any time; The factors that cause power cable failures are complex and varied. Here, after sorting and analyzing, the causes of underground power cable failures can be roughly summarized into the following categories:

Firstly, poor design and manufacturing processes

The waterproof and electric field distribution design of the middle and terminal of the cable is not thorough, the material selection is improper, and it is not made according to the requirements of the regulations, all of which can cause cable head failure.

Secondly, mechanical damage

Usually, some mechanical damage is minor and did not cause a malfunction at the time. It takes several months or even years for the damage to develop into a malfunction. The main causes of mechanical damage to power cables are:

(1) Carry out civil construction on or near the cable path after installation, causing direct external damage to the cable.

(2) The vibration or impact load of driving vehicles can also cause lead (aluminum) sheath cracking and damage to underground cables.

(3) Accidentally damaging the cable during installation, pulling the cable due to excessive mechanical traction, and bending the cable excessively.

(4) Damage caused by natural phenomena. For example, the inner insulation glue of the intermediate joint or terminal head expands and cracks the outer shell or cable sheath; Or the cable sheath installed on the pipe mouth or bracket may be scratched; Or due to excessive tension caused by land subsidence, the intermediate joint or conductor may be pulled apart.

Thirdly, overvoltage (lightning strike or operational overvoltage)

The effect of atmospheric and internal overvoltage causes the insulation of the cable to be broken down, resulting in cable failure. In general, there are defects at the breakdown point.

Fourth, insulation is affected by moisture

Moisture in insulation can cause a decrease in cable withstand voltage and lead to malfunctions. The main reasons for cable moisture are:

(1) The metal sheath has been corroded, perforated or punctured by external objects.

(2) Water ingress due to unsealed or poorly installed joint or terminal box structure.

(3) Poor cable manufacturing, with small holes or cracks in the metal sheath.

Fifth, insulation aging and deterioration

Insulation aging can cause a decrease in cable withstand voltage and result in faults. The main reasons for cable aging are:

(1) The power cable is used beyond the time limit.

(2) Overloading of cables or poor ventilation of cables can cause local overheating, leading to insulation carbonization. Cable overload is an important factor in cable overheating.

(3) When laying oil immersed paper insulated cables, the ground is uneven. Due to the presence of height differences, the excess insulation oil will flow towards lower areas, resulting in a decrease in the insulation performance of the cables at higher points and causing malfunctions.

(4) There are slag or air gaps inside the insulation medium of the cable, which can cause ionization and hydrolysis under the action of an electric field, leading to a decrease in insulation.