Electric power industry consulting
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.
When we were little boys and girls, many of us liked:1️⃣ Sit in the sandbox and dig the sand with a shovel.2️⃣ Shoot from an imaginary space weapon.3️⃣ Play hide-and-seek with each other. In the attached video, the team of cable specialists, despite their advanced age, was quite able to return to their childhood. Why
For surge arresters (SA) of 110 kV and above, special grading rings are usually used, which, in normal operation mode, make it possible to equalize the distribution of AC 50 Hz voltage along the SA height. This distribution is important because it guarantees the absence of overheating of the SA elements (varistors), eliminates the risk
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
The photo shows the grading ring (“screen”) that remained from the damaged 110 kV metal-oxide surge arrester (SA or MOA). I’m not going to discuss now why and where the damaged SA went (flew away or just fell down on some equipment and people’s heads). Now I would like to discuss the SA screen only.
Birds build nests on the overhead line towers (pylons, poles). Rats feed on the outer sheath of cable lines. Fungus settles on polymer insulators (Photo). What’s next? The photo shows the 110 kV disconnector support insulators installed in Karelia (a region on the southern border of Finland). During operation, it was noticed that over time,
This is an amazing tower of a 110 kV multi-circuit overhead transmission line. It was built in the Kaliningrad region, former USSR. Although I love electric cables and lead a Linkedin group on them, I still have to admit that it is difficult to make something so bright and attractive out of a cable buried
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
Unfortunately, when checking the resistance of equipment to short-circuit currents, it is necessary to take into account not the time of the main protection (usually less than 0.1 seconds), but the time of backup protection (can reach 0.5-2.0 seconds). Such rules, for example, are applied all over the world when designing cable lines. This means
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