Electric power industry
High-voltage cables must have a conductive metal screen (sheath). The selection of the screen cross-section is very important. Without selecting the screen cross-section (and bonding/grounding scheme), it is impossible:✅ To ensure the resistance of the cable screen to fault (short-circuit) currents.✅ To perform a thermal calculation of the cable line and select the core cross-section.
High voltage cable terminations are usually installed vertically. This allows you:✅ To ensure the absence of mechanical influences bending the termination under its own weight and the weight of the cable.✅ To ensure high-quality filling of the termination with dielectric oil (not relevant for terminations of dry-type or gas-type). However, sometimes, for various reasons, the
If the cable is laid not in the ground, but on some structures, then it usually needs to be fixed. This is necessary, for example, so that during the passage of short-circuit currents through the cable, the forces that arise do not move the cable from place to place. A huge number of different versions
Earlier, I posted some photos showing that the surge arrester (SA), in case of its damage, can pose a danger to the equipment placed nearby. But what about consequences in case of damage of cable termination or cable joint? There are some examples of what we can get for 110 kV:1️⃣ cable termination mounted in
If you are communicating with a person who puffs out his cheeks and says that he is perfectly familiar with the screens cross-bonding of single-core high voltage cables, then ask him next simple question – “What is the difference between two types of screens cross-bonding shown on schemes (a) and (b)?” There is type “123-312”
High voltage cables have an outer sheath. It is very important to ensure that sheath does not have serious damage. Otherwise, water may get into the cable, which in a few years will lead to a short-circuit of main XLPE-insulation. The sheath tests are performed by applying a DC of 10 kV between the cable
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
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