Electric power industry consulting
Single-core cables with XLPE insulation are massively used in 110-500 kV networks. Solid (two-sided) grounding of the screens of such cables leads to negative consequences, and therefore, as a rule, for screens should be used:✅Single-point grounding (see diagram)✅Cross-bonding. In both schemes, voltages may occur on screens relative to the ground caused by interference from the
All over the world, more and more cable lines are laid not in the ground, but in ducts (conduits, pipes). Such ducts are made of various materials (PE, HDPE, PE-RT, PP, PVC), they can be single-layer or multi-layer. But all these ducts have one common problem – they have “infinite” impedance Rd of the side
Cable terminations are a weak element of the cable line, since:✅they have a complex structure;✅they are mounted manually (and the quality of installation depends on the qualification of the installer and his mood);✅they are subject to various external influences (sun, wind, rain, snow, ice etc). When a cable termination is damaged, it is not always
The electrical capacitance of cables directly affects the arrangement of medium-voltage 6-35 kV networks with an isolated neutral, as well as issues of reactive power compensation of 110-500 kV networks. Let’s talk about what kind of capacitance the modern cables have. THE FIRST.When cables with cross-linked polyethylene (XLPE) insulation appeared, we were told that these
In 6-500 kV networks, single-core cables with XLPE insulation are widely used. Such cables have conductive screens. In such screens, if they are grounded at both ends, AC 50 Hz currents are induced in normal mode and active power losses occur. This leads to additional heating of the XLPE, a decrease in the long-term permissible
The reliability of cable lines is catastrophically dependent on the quality of installation work. Therefore, we can only be glad that there are a large number of experts all over the world who do their job accurately and precisely. Certainly, some of them may even be called as perfectionists. However, in my opinion, there is
At the ends of the cable line, there are cable terminations. Metallic screens of cables are removed from terminations to the outside, where they are connected in accordance with selected bonding/ grounding scheme. For example, the figure shows the high voltage cable line with one-sided grounding of screens. To have this scheme, metallic screens, with
Designing a cable line is an interesting process that resembles moving in a circle. The fact is that in order to select cables, we need the correct values of the short-circuit current (1.1) and the steady-state current (1.2). Such currents can only be calculated using information about the impedances of the cable line (R1, X1,
When designing cable lines, it is very rare to find such projects where there is a section of documentation in which calculations of the magnitude of the magnetic field H of the cable line would be carried out. At the same time, the magnetic field H can pose a significant danger, primarily under the following
The previous post was about the reasons why switching lines with shunt reactors (SR) can cause damage of the line breaker B1. Theoretically, several options can be proposed to solve the problem. Let’s start with controlled switching devices (CS, see scheme). CS can be used only in cases when each phase of the breaker has