Overvoltages and protection / 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

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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

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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

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Overvoltages and protection / 13.05.2025

Surge arresters and IEC 60099

All the experience allows the author to state that the global metal-oxide surge arrester (MOA) industry is in dire need of simple MOA application methods, but, instead it, is developing endless editions of IEC 60099, adding details to an already complex document that contains dozens of MOA characteristics. At the same time, IEC 60099 does not divide

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Cable lines / 02.05.2025

Cable overvoltage protection

In the energy industry, many processes can not only be calculated on models, but also measured in an operating network. Measurements are important because they allow us to verify the models and, if necessary, adjust them. One of the areas where measurements in the network are practically impossible is impulse processes (lightning and switching). Therefore,

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Overvoltages and protection / 20.01.2025

Cable network resonance

Medium voltage 6-35 kV grid usually do not have a solid neutral grounding, and a voltage of 50 Hz may occur on the neutral. Today let’s talk about why it may happen in the cable network even in normal operation, and how this can lead to Temporary Overvoltages (TOV) and damage to equipment. One of

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Overvoltages and protection / 01.11.2023

Surge arrester and backup protection

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

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