Electric power industry consulting
When designing 6-500 kV cable lines, one of the important tasks is to carry out thermal calculations and select the cable core cross-section (taking into account all influencing factors). The customer gives us the current that the cable line should pass, and we tell him which combination of cable core cross-section and screen bonding type
Usually a cable line has one cable (one core) for each of the three phases A,B,C. However, there are cases where the number of cables per phase increases up to 6 (see photo) or even more. This may be necessary, for example, so that the line can pass the entire operating current of the supply
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.
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
Let me pay attention to one very common mistake that can be very expensive. In the construction of a single-core cables, the main elements are the core and XLPE-insulation. The metal screen (Cu, Al) and the outer sheath of the cable are usually perceived as auxiliary elements of the cable. As a result, people carry
The photo shows the ordinary cable termination of 10 kV, which was overheated due to high currents induced in the screens. We can see traces of excessive heating at the junction of the screen with its grounding wire, caused by significant currents passing there. The quality of the screen and wire connections is a separate