Electric power industry consulting
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
Let’s explain how, using the system of correction coefficients given in cable catalogs, the influence of pipes on the long-term permissible current should be taken into account. The error in such calculations is actually due not only to the fact that the catalogs have lost the relevance of the correction factor Kp = 0.9. To
Figure (A) shows the thermal scheme of a cable line laid in the ground. The following designations are used: Pc, Ps – loss of active power in the core and metallic screen of the cable; Tc, Ts, Tg – temperature of the core, screen, ground; Rins, Rosh, Rg – thermal resistances of insulation, outer sheath,
Laying cables in pipes is a common way of laying high-voltage cable lines. Usually, pipes are accounted for using a correction factor K=0.9, that is, it is assumed that laying cables in pipes reduces the permissible current by 10%. For example, if the cable line in the ground had a permissible current of 1000 A,
In the cable catalogs of leading manufacturers of power cables there is a system of correction coefficients for selecting the core cross-section. According to this system, laying cables in pipes reduces the long-term permissible current (current capacity) of the cable line, and the corresponding correction factor is 0.9. I must say that this is incorrect.