Cable lines - various topics / 19.07.2025

Cable sheath thickness

It has always been obvious to me that in terms of thickness, there are two types of outer sheath of high voltage (HV) and extra-high voltage (EHV) cables:✅ Ordinary sheath – it has a thickness of about 5 mm.✅ Reinforced sheath – it has a thickness of about 6-7 mm.However, when I started trying to

Read More
Cable lines - transients / 19.07.2025

Screen bonding cable length

We know that the screen’s cross-bonding is an effective way to deal with induced currents and losses in the screens of 6-500 kV cable lines (CL). The use of cross-bonding allows not only to save on losses (dozens of thousands of euros annually), but also to increase the permissible core current of the cable line,

Read More
Cable lines - ampacity / 11.07.2025

Cable line selection

It is not enough to have money to buy a good cable. It is also important to find the time and knowledge to make the necessary calculations and select the best way to lay a cable line, taking into account the screen bonding type. Today, let’s look at a simple calculation example of a double-circuit

Read More
Cable lines - transients / 07.07.2025

Sheath voltage limiter selection

For lines with single-core cables, there is a problem of selecting the optimal screens’ bonding type. It is especially relevant for 110-500 kV lines, where grounding of screens on both sides is almost prohibited, and 99% of lines have either grounding of screens on one side or cross-bonding of screens. In both cases, it is

Read More
Overvoltages and protection / 06.07.2025

Surge arrester optimal location

Dear colleagues, let me please start a series of “green posts” on electromagnetic transients and protection against them. In general, I have to admit that there are too many experts in this area in the world, and it seems to me sometimes, they are ready to fight brutally for their right to exist under this

Read More
Cable lines - ampacity / 03.07.2025

The system of correction factors

In cable catalogues, in addition to the main types of cables, there are simplified recommendations on cable selection. They are given as a table with capacity currents for basic laying conditions (Ib), as well as a series of 5-8 additional tables with various correction factors (K). It is important to note that the system of

Read More
Overvoltages and protection / 01.07.2025

Where does flashover occur?

Lightning processes are statistical processes. It is hardly possible to study such processes by considering a lightning strike to the line with specific parameters (current, front) or by considering a specific lightning wave coming from the line to the switchgear. To calculate the probability, I normally use ATP/EMTP, which has been changed for the convenience

Read More
Cable lines - parameters / 13.06.2025

Equivalent depth of the current

There is one important concept in the calculations of power transmission lines – this is the equivalent depth of current in the ground (Dg). In symmetrical operating modes (normal mode and three-phase short circuit), there is no electric current in the ground, and this depth is not interesting to us. However, in any unbalanced modes

Read More