Despite the higher investment costs, cable lines are becoming more and more popular because they are safer and less emergency than commonly used overhead lines. However, this does not change the fact that, like any other technology, they also have their drawbacks. In order for their use to be safe, so you need to follow strictly set rules and follow good practices.

Cable lines and electromagnetic field

When laying and operating cable lines, especially high voltage, be careful at every stage. When laying, it is useful to such equipment as a cable. However, the threat does not end at this stage, because even efficient, undamaged cable lines produce an electric field around them, which may result in interference. High voltage lines allow you to send high power, but this has its cons, because negative environmental impact and living organisms cannot be ruled out.

These types of doubts are discussed more often, because the increasing part of the line are high voltage lines. They are often located near electric, telephone, heat and gas lines. They are also run a short distance from various types of housing and utility buildings. Therefore, the power field can somewhat affect IT or signaling systems. It is therefore necessary to assess how much disturbances the cable line can cause. There are also ways to minimize them, e.g. by proper arrangement and grounding, or the use of additional antico -balance screens.

Magnetic coupling

Generating interference by electromagnetic lines consists primarily of magnetic and galvanic couplings. The mechanisms of this problem are different. It is largely due to the induction of tensions and currents in metal elements and wires that are located near the electromagnetic line, such as signaling cables, telephone, IT lines, gas or thermal routes. The second mechanism is earthing problems, which may arise if the cables of other systems are connected to it.

The magnetic coupling scale depends on many factors, which include:

• The value of the current flowing in the working vein,
• Mutual inductance,
• Land resistivity,
• Current value in long -term work and emergency states,
• Type of grounding.

Magnetic coupling is not the only problem that may appear when using high voltage cable lines. Galvanic coupling is another of them.

Galvanic couplings

With the proper design and implementation of grounding, this problem does not matter too much. It may appear if there was a short short circuit near the cable entrance to the transformer station. Galvanic coupling values depend on the resistance of the soil and the place of short circuit. Therefore, they are marginal when it comes to the safety of the use of high voltage cable lines. To exclude problems with galvanic couplings, it is usually enough, for example, using the appropriate screen.

Estimating the voltage induced by cable lines

Safe laying and use of a cable line requires detailed design. At the first stages, this applies, among others, to the use of such solutions as the belt winch, and on the next: e.g. calculation of the reduction factor. For practical reasons, possible magnetic couplings and short circuit current are determined. All this is associated with the presence of an electromagnetic field emitted by a high voltage cable line. The field intensity, of course, is not just as high in every case. It should be borne in mind that values differ depending on the operating conditions, both during long -term work and in emergency conditions.

In fact, disruptions in cable lines are not that large, because all short -circuit current does not participate in their generation. Its part flows back to the transformer through the return vein. This compensates for short -circuits caused by short -circuit in the working vein, which is why the damage does not have such a negative effect on the environment. It is also helpful to use additional metallic screens, because they flow in them with currents that compensate for interference. Correct positioning and shielding, therefore, make the use of high voltage cable lines safe.

When determining the risk, an additional reduction factor, commonly correctional, is also taken into account quite often. It takes into account the fact that the risk for short -circuit current to flow among the entire length of the cable closer is extremely low. However, this is omitted, e.g. during the construction of signaling railway lines.

Cable lines inspection

At the stage of laying cable lines, for safety reasons such equipment is necessary as an invasion of drums. Even the appropriate design and laying are not able to completely prevent damage. It is therefore necessary to carry out a visual inspection, and the frequency depends on the type of cable line:

• 30 kV cables: once a year,
• 6 kV cables: once every 3 years,
• NN cables: once every 5 years.

You should also always remember about the inspection if earth or construction works were carried out near the cable route. The technical condition should also be inspected after automatically off the cable line. Elements such as:

• Parts of cable lines near water reservoirs,
• Entrances to tunnels, channels, etc.,
• Anti -corrosion shields,
• Cable heads,
• Connections of grounding cables and clamps,
• Fire devices and fire equipment.

Regular control of the technical condition of the cable line and a professionally made project avoid the negative effects of their use. However, if there is a risk of damage to the line, you need to examine as soon as possible.