Corona lightning overvoltage analysis for a 500 kV hybrid line

In this paper, the overvoltage distributions due to the lightning stroke are analyzed for a 500 kV hybrid OHTL-Cable-GIL circuit beside substation, in which the section length is variable. Corona effect is incorporating in order to estimate the attenuation and deformation of overvoltage's travelling waves on transmission lines near substations. The influence of connecting substations surge arrester, direct, and indirect lightning strokes are investigated. ATP/Electro Magnetic Transients Program(EMTP) simulation program is applied to analyze the lightning overvoltage of a 500 kV hybrid OHTL-Cable-GIL system. It was discovered that OHTL-Cable, OHTL-GIL, and hybrid systems produces lightning overvoltages higher than those of a fully cable system and very likely lower than those of a fully OHTL system with the same transmission lengths. This means that the risk of experiencing high lightning overvoltages and stressing system components is higher in a fully-Overhead Line (OHL)circuit than in a partial or full cable or GIL line. Furthermore, using the Cable with MOSA (Metal Oxide Surge Arrester), the results have more regular voltage waveform at substation entrance; also Hybrid line has the same effect of fully GIL. Finally, the corona has a less attenuation effect of overvoltage reached to substation by about 2.7% in case short length OHTL.