The need for energy in the industry is increasing. Therefore, cables with this feature are needed to transmit higher energy levels over longer distances. In general, energy transmission over long distances is provided by air. However, in residential areas, the transmission is made with underground cables. Transmission of underground energy is costly but more convenient for safety. The higher the voltage used for a given power, the smaller the current.

Initially, electric current was transmitted by DC current (direct current). Then, transformers were started to be used and electrical current was started to be made with AC current (alternating current). Today, power transmission is still possible with AC current. However, in recent years, new breaker circuits have been developed and it has become easier to convert alternating current to direct current and direct current to alternating current, and since 1980, direct current has been started to be used again in power transmission.

In the field of transmission and distribution, many different cable insulators have been used to date. For example, in the early days, oil impregnated paper insulator was used as an insulator in cables, while synthetic polymers and compressed gases are now used. Polymers are most preferred.

Insulating materials and production techniques are developed on the one hand, while high voltage cable technology is being developed that can transmit the required voltage levels. As the transmission distances of cable networks are so long, the reliability and deterioration problems of these cables have become increasingly important. In this respect, long term resistance tests of insulation to DC voltage (direct current) are performed. These tests are performed by accredited laboratories within the scope of electrical tests.

 

During these tests all sheaths are removed and the vessels are immersed in 60 grade water. Then 10 is applied to 220 volts direct current (DC) throughout the day. There should be no short circuit in the insulation during the test.