In this paper, the effectiveness of lightning overvoltage protection of cables in high voltage overhead cable lines has been analyzed. Because of the high overvoltage level, the cables are protected by surge arresters and by metallic sheath earthing. However, in practice, quite a lot of cases of electricity-evoked damage to the cable outer sheaths are observed, proving that the effectiveness of the protection used is insufficient. As a result, the cables are exposed to environmental factors, especially moisture penetration, which contributes to cable degradation. To explain the causes of this situation, simulation studies were carried out to determine the relevant factors affecting the level of expected overvoltages. The circuit-field model of the overhead cable line in EMTP-ATP, COMSOL and MATLAB software was used for determining overvoltages on the main cable insulation and the outer protective sheath. The studies reveal that the efficiency of the cable insulation overvoltage protection is ensured regardless of the lightning strike location and the crest value of its current. However, the obtained results confirm that no matter the applied protection, the cable outer sheaths may be exposed to overvoltages with higher values than those of the main insulation. Although the analysis was performed for 110 kV lines, the conclusions are general and are also applicable to power lines with higher rated voltages.

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The article deals with the problems of single-phase short-circuit current distribution in overhead power lines. Short-circuit disturbances cause many negative phenomena in power networks. Since experimental studies of short-circuits in real networks are practically impossible to perform, these effects can be evaluated only theoretically, based on short-circuit current calculations with the use of appropriate mathematical models. Although short-circuit modeling is considered to be one of the simplest power system calculations, the exact mathematical description of the phenomena occurring at short-circuits is complex. Simplified normative methods are often used for short-circuit current calculations; however, this does not give ground for a thorough analysis of short-circuit current distribution in power lines. The distributions are analyzed using power line models with different degrees of complexity in line with the assumptions made for a given model. The paper presents the problem of current distribution analysis in high-voltage overhead lines for single-phase faults to the tower structures. Simulation studies were conducted on the models developed for the calculation of short-circuit currents in the high-voltage power line earthing. The objective of the analysis was to assess the validity of simplification assumptions followed by practical recommendations on the applicability of the models.

Celem artykułu jest analiza możliwości redukcji szerokości stref oddziaływania pola elektrycznego przez zmianę parametrów projektowych linii elektroenergetycznych określających przestrzenne rozmieszczenie jej przewodów. Analizę tę przeprowadzono z zastosowaniem opracowanych i zweryfikowanych eksperymentalnie modeli do wyznaczania pola elektrycznego w otoczeniu linii. Modele obliczeniowe wykorzystano do badań szerokości stref oddziaływania pola elektrycznego jedno-i dwutorowych linii elektroenergetycznych 400 kV. Badania potwierdziły możliwość znacznej redukcji szerokości stref oddziaływania pola elektrycznego dzięki odpowiedniemu wyborowi kluczowych parametrów projektowych i konstrukcyjnych linii. Sformułowane wnioski słuszne są nie tylko w odniesieniu do linii 400 kV, ale także wskazują na kierunki zmian parametrów linii o innych napięciach znamionowych (powyżej 100 kV).Słowa kluczowe: korytarz infrastrukturalny, napowietrzne linie elektroenergetyczne, pole elektryczne, modelowanie, redukcja pola elektrycznego, projektowanie linii elektroenergetycznych ELECTROMAGNETIC ENVIRONMENTAL IMPACT OF 400 KV TRANSMISSION LINES -ANALYSIS AND METHODS OF ITS REDUCTION

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