Electric power industry
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,
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
We hear a lot that “green transition” is impossible without cable lines. But do we know and understand cable lines that well? Unfortunately, I have to say that we do not know them very well, and so far, the cable standards and catalogues require improvement. Let me show this using the example of the longitudinal
In the energy sector, there is more and more complex computer software for calculating equipment, various network operating modes and transients. On the one hand, this is good, but on the other hand, it personally causes me some fear. I will try to clarify my thoughts. Many of the software methods give the impression of
In 6-35 kV networks, many methods of neutral grounding are known. They differ in the magnitude of the ground fault current, the magnitude of the voltage increase on two intact phases, the ability to quickly search and selectively disconnect a damaged line, and so on. Let’s discuss a different question – how does the neutral