Electric power industry consulting
We are absolutely sure of π=3.1415926535 and e=2.7182818284 – we use them in software. However, in our everyday life, we specify only 3 digits (3.14 and 2.72), and this is enough. Rarely we give 5 digits at once (3.1416 and 2.7183). If someone indicates 6 or more, we will consider it beyond reasonable. How do
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
Currently, there are a lot of switchgears where metal-oxide surge arresters (MOA or SA) are installed nearby other equipment. We can see MOAs very close to the power transformers, measuring transformers, cable terminations. Sometimes MOAs are installed directly on the tank of a power transformer or suspended above it. Unfortunately, operational experience shows that all
In recent years, the laying of high-voltage cable lines is often carried out in polymer pipes. Such pipes are laid either at the bottom of the trench or are dragged into the ground into channels prepared by horizontal directional drilling (HDD). Laying of cable lines in pipes provides mechanical protection of cables, minimizes open excavation
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
The photo shows a concrete underground well. It houses cable joints for 110 kV single-core cables. There are 6 joints for 6 single-core cables, which means that there is a three-phase double-circuit cable line. A fault (short-circuit) occurred in one of joints due to poor-quality installation, which led to an explosive increase in pressure in