Electric power industry consulting
When laying cables along structures, as well as near the terminations and joints, cables should be fixed. It is necessary because the cables are in the magnetic field of their neighbours, and according to Ampere’s law, forces arise between the cables:➡️ In normal mode.➡️ When switching cables.➡️ In case of a short circuit. The most
Today, let us talk about the bricks that can sometimes be found when laying low-voltage (up to 1 kV) and medium-voltage (up to 35 kV) cables in a trench. In general, the bricks can be used:✅ between the cables (photos 1️⃣-2️⃣-3️⃣).✅ above the cables (photos 4️⃣-5️⃣-6️⃣). Bricks between the cables can have the following purposes:1️⃣
Let us talk about how to position a drum with a cable and, most importantly, why it is possible to do one way or another. The most familiar options are when the drum with the power cable is positioned vertically, as shown in the photos 1️⃣, 2️⃣, 3️⃣. This position allows to have the axis
Today, let us talk about the Earth Continuity Conductor (ECC) and the bad things it does to the cable line during normal operation. ECC is most often used for cable lines made with single-core cables and having single-point bonding/grounding of the metal screens. ECC performs two main functions:✅ ECC reduces 50 Hz voltages (Us), which
The sheath of high-voltage cables sometimes has a semiconductive layer (SC). Such a layer is believed to allow for better control of the condition of the outer sheath of the cable. For example, the presence of such a layer allows to check the cable outer sheath while the cable is on the drum. For this,
On AC 50 Hz lines built with single-core cables, induced (circulating) currents and associated power losses occur when the screens are solidly bonded. These currents and losses become especially dangerous when phases:➡️ have an increased screen cross-section (say, more than 50-70 mm2);➡️ arranged not in a trefoil, but in row, at a distance from each
The Internet has a lot of photos from real facilities where cable lines are laid, and such photos are interesting to study. There were several photos where a pipe was laid along the trench, from which flexible tubes connected to numerous vertical rods extend. There was no doubt that we had a water pumping system
Copper (Cu) and aluminium (Al) are the two main materials for the manufacture of conductive elements (cores and screen) of cables of all voltage classes. When choosing between Cu and Al, we have to compare them, and not in words, but numerically. For example, we know at least the following numbers comparing the properties of
Single-core cables are used in both high-voltage and medium-voltage (MV) networks. In both cases, the cables have the same problem – the presence of induced (circulating) currents in solidly bonded screens. To solve the problem, there are other bonding types:👉 Single-point bonding of the screens.👉 Cross-bonding of the screens. Despite the fact that problem with
If a short circuit occurs on the line, the line is switched off. However, what to do next depends on the type of the line:1️⃣ overhead line;2️⃣ cable line;3️⃣ mixed line, having both overhead and cable sections. 1️⃣ OVERHEAD LINEFor an overhead line, up to 60-90% of faults are associated with short-term overlaps of air