Laying cable lines in accordance with good practices ensures safety, but you also need to remember to check the technical condition before starting and during operation. The use of such solutions as cable winch prevents damage during laying, but this does not mean that punctures will not appear later.

Inspection of low and medium voltage lines

A detailed check of the technical condition is necessary not only before the new cable line is commissioned, but also, for example, after its reconstruction. The elements that need to be checked include the way the cables are laid and their connection. It is necessary to use markers, i.e. simply plates on which all the most important information are found: user, line number, cable type, year of arrangement. The presence of the marker allows for quick cable identification, which is why the plates must be regularly arranged. The ground should be found every 10 meters, and in tunnels or channels - every 20 meters. The plates should also be placed in cable cable lines: on arches, on connections (made of muff and heads) and at intersections.

Marking is also placed on the surface, which greatly facilitates repair and maintenance. Concrete buildings and posts are used here, on which there are plates with K - cable and m - MUFA. Thanks to this, setting the cable line route is very simple.

Regular inspection is also necessary, but thanks to the low failure rate of cable lines, with low and medium voltage lines, it is enough to carry them out every 5 years. Check first of all:

• heads,
• markers,
• entrances to tunnels and wells,
• fire protection and anti -tire protection.

Although when laying and rebuilding a cable line, solutions such as cable stocking are used, after completing work it is necessary to check whether there was no damage.

Measurements of resistance and electrical strength of insulation

The cable line review is the basis for its safe operation. After arranging a new line or its reconstruction, you need to check such parameters as insulation resistance and electrical resistance.

To measure insulation resistance, a megamomer is used, whose voltage should be a minimum of 2.5 kV. The result depends on voltage, line length and type of insulation. The longer the line, the lower the insulation resistance must have. As an example, we can give a 1 km long cable line with paper-oil insulation. If the cable voltage does not exceed 1 kV, the 20 mΩ resistance will be sufficient. When the voltage is in the range of 1-30 kV, the resistance should be higher and be 50 mΩ. Too low resistance may result from various reasons. It happens that the problem with insulation appears all over the line - it can be weakened due to moisture or overheating. Sometimes the situation is different - the insulation is in excellent condition on most cable lines, but in one place it appeared. That is why, the resistance of a longer section of the cable line provides less accurate information than measuring a single receiver or transformer insulation resistance.

With full insulation test, you can check the electrical strength. However, this is more complicated, which is why this method is used rather with high voltage cable lines. To check the electrical strength, the exile current flowing through insulation in increased voltage conditions is measured for 10 minutes. In this way, you can check if the cable line is able to withstand the voltage higher than usual. Insulation is checked in terms of solid and alternating voltage.

Cable lines celebrations and detection of damage

An important element of the technical control of the cable line are their celebration, i.e. simply a visible part of the visible parts. This is especially important when earthworks are carried out near the cable line and the risk of damage increases. During the celebration, markers, tunnels, channels, wells, cable heads, protective connections and covers are checked. In the case of a line with a voltage below 60 kV, this celebration is usually done every 2-3 years.

It is also necessary to regularly clean elements such as wells, channels and cable tunnels. Armored cables, which are located in places conducive to corrosion, also require special maintenance. It is helpful to paint them with rust -protecting them. If necessary, the Syciwo in the oil heads is also complemented, because in time defects may appear.

Cable damage may appear at any stage. When laying lines, their likelihood is reduced by solutions such as drum developing, but the puncture can also arise during operation. Here, many damage location methods are used because it is difficult, especially if the cable is in the ground. We have already mentioned detection of damage in one of the previous articles on our blog.