Optimized Protection of Pole-Mounted Distribution Transformers against Direct Lightning Strikes

Abstract

Direct lightning strikes on overhead phase conductors result in high overvoltage stress on the medium voltage (MV) terminals of pole-mounted transformers, which may cause considerable damage. Therefore, introducing an efficient protection strategy would be a remedy for alleviating such undesirable damages. This paper investigates the optimized protection of MV transformers against direct lightning strikes on the phase conductors. To this end, first, the impacts of grounding densities (number of grounded intermediate poles between every two successive transformer poles) on the probability of overvoltage stress on transformer terminals are investigated. Then, the implications of guy wire, as a supporting device for ungrounded intermediate poles, on reducing the overvoltage stress on transformers, are studied. Finally, the role of a surge arrester in mitigating the overvoltage stress of non-surge-arrester-protected transformer poles is scrutinized. The investigations are conducted on a sample MV network with 82 wood poles comprising 17 pole-mounted transformers protected by spark gaps. To provide in-depth analysis, two different poles, namely creosote- and arsenic-impregnated poles, are considered under wet and dry weather conditions. A sensitivity analysis is performed on grounding distances and on a combination of guy wire and grounded intermediate poles while taking into account soil ionization. The results provide a clear picture for the system operator in deciding how many grounded intermediate poles might be required for a system to reach the desired probabilities of transformers experiencing overvoltage stress and how the surge arrester and guy wires contribute to mitigating undesirable overvoltage stress.

Enhancing the Protective Performance of Surge Arresters against Indirect Lightning Strikes via an Inductor-Based Filter

“…As can be seen from this figure, there is a good agreement between the laboratory test and the results obtained in EMTP-RV software. Interested readers may refer to the work in [49] for obtaining a complete report on the laboratory setup, supporting figures, as well as a wide range of experimental results at the presence of spark gap, while more information regarding the applied impulses and the validation of the spark gap can be found in [33,50].…”

Integrating IoT Technology for Improved Distribution Transformer Monitoring and Protection

“…The distribution transformer is a step-down transformer used to distribute the power to different consumers, usually used to step down 11 kV to 220 V (Phase to Neutral) and 440 V (phase to phase). It has two types of pole-mounted [3] and groundmounted distribution transformers.…”