Electric power industry
Power transmission lines usually are double-circuit. This allows you to maintain or repair a disconnected circuit while the second circuit remains in operation and provides power to consumers. For this kind of lines, questions usually arise with the safety of personnel, since the disconnected circuit is under the influence of a 50 Hz voltage induced
The photo shows cable termination of the single-core cable, which was overheated due to high currents induced in the screen and the armor. As far as you know, for single-core cables, armor can only be made of non-magnetic materials, and the photo shows aluminum allow armor that tightly covers the cable from the outside. Why
There are a huge number of different types of transition towers between cable and overhead lines. The photo shows one of the HV types which is used on the territory of the UK. There are similar examples from around the world. As you can see, the equipment of the transition tower is surrounded by a
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.