Electric power industry consulting
In 6-35 kV networks, single-core cables are most often arranged in a closed triangle (1), and cable screens have a small cross-section of up to 50 mm2 and a simple solid grounding. Let us figure out what happens if the cables, contrary to the project, are laid not in a closed triangle, but otherwise. Three
If the outer sheath of the cable is damaged, water can penetrate into the cable, and this will lead to the defects in the XLPE insulation, followed by its breakdown (that is cable will get a short circuit). Therefore, it is important to monitor the condition of the outer sheath of the cable, preventing the
The method of symmetrical components is used to calculate the normal and emergency modes of the electric network. The method represents an any mode (even asymmetric) as a composition of three separate symmetrical ones:✅ Positive sequence “1”.✅ Negative sequence “2”.✅ Zero sequence “0”. To use the method, it is important that the longitudinal impedances Z1,
There are two main types of power transmission lines – overhead lines and cable lines. Traditionally, in high-voltage networks, the total length of overhead lines exceeded the total length of cable lines. Therefore, some errors in the calculations of impedances of cable lines were not able to lead to serious consequences. However, gradually, especially with
The vast majority of cable lines (CL) are double-circuit. Two circuits are needed not only to increase the transmitted power, but also for reliability reasons. If one circuit turns out to be disconnected (for testing, damage locating, repair, replacement), then the second circuit can provide power supply to consumers (to load). Two modes are possible
Sometimes we have to lay our cable line (CL) along some other 6-750 kV existing lines (cable or overhead). In such cases, we have to think about the magnitude of the induced voltages on the core and screens of our CL. Such interference is caused by the magnetic field of currents passing in adjacent cable
When designing 6-500 kV cable lines, one of the important tasks is to carry out thermal calculations and select the cable core cross-section (taking into account all influencing factors). The customer gives us the current that the cable line should pass, and we tell him which combination of cable core cross-section and screen bonding type
Cable lines are increasingly laid not in the open ground, but in pipes (ducts). This allows you to protect cables from mechanical influences and aggressive environment, ensure quick replacement of the cable with a new one, lay cables not only by the traditional method in trenches, but also by horizontal directional drilling HDD (this method
Usually, AC cable lines are up to 10 km long. However, in some cases the length can reach 50 km or even 100 km. In such cases, the cable line has a significant capacitance, which must be charged and discharged following the sine wave of the alternating voltage of the AC network. This alternating current
Usually a cable line has one cable (one core) for each of the three phases A,B,C. However, there are cases where the number of cables per phase increases up to 6 (see photo) or even more. This may be necessary, for example, so that the line can pass the entire operating current of the supply