Electric power industry consulting
There are «well-known» formulas for calculating the active R and inductive X impedances of the cable line, given in plenty of cable catalogs and regulatory documents. These formulas are shown in the figure. Unfortunately:1️⃣ They relate exclusively to the case of positive sequence and are inapplicable for zero sequence. That’s why they marked as R1
Look at this example of installing HV cable terminations on the switchgear. In my opinion, there are several mistakes at once. 1️⃣ The lower flange of the termination must be at least 2.5 meters above the ground (this distance is determined by the height of the service personnel who raised his hand up). However, in
We usually think that the core and its XLPE-insulation play the main role in the cable design. At the same time, we perceive the metal screen (Cu, Al) and the outer sheath (PE, PVC, etc) as secondary elements of the cable. It’s a serious mistake. SCREEN. As already shown in previous posts, in normal operation
The photo shows a standard box for grounding of single-core cable screens. Such boxes are placed close to the cable terminations. Looking at the photo, we can see that the lid of the box has about 30 bolts. The question arises – do we really need this? The answer is no, we don’t need it.
Traditionally, the concept of “transposition” was used mainly for overhead lines (OHL) with a voltage of 330 kV and higher. For OHLs, the concept of “transposition” means a periodic change in the relative position of the three phase wires ABC. However, the situation has changed after the appearance of single-core cables with XLPE-insulation – the
Faults on cable terminations (as well as cable joints) are a significant problem of cable lines. Termination fault also means that a section of cable inside and near the termination may be damaged too. Therefore, for the installation of a new termination instead of broken one, not only new termination itself is required, but also
1️⃣ As you can see from the photo, the cable screens are grounded directly to the support structure, without the use of link-boxes (I marked screens with yellow lines). This kind of screens connection is not a good solution, because it creates problems for personnel during periodic tests of the cable outer sheath. Let me
The photo shows a 220 kV cable line laid in one of the Central Asian countries. During the construction of the line, cables and couplings (joints and terminations) were used of one of the world famous Asian manufacturers. After several years of operation, the cable joints gave faults one by one, and in total more
In addition to cable and overhead lines, there are mixed lines when, for various reasons, part of the line route is made as an overhead line, and part as a cable one. At the junctions of cable and air sections, special “transition points” have to be equipped. There are a huge number of transitional point
Let me pay attention to one very common mistake that can be very expensive. In the construction of a single-core cables, the main elements are the core and XLPE-insulation. The metal screen (Cu, Al) and the outer sheath of the cable are usually perceived as auxiliary elements of the cable. As a result, people carry