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Lightning Protection of Distribution Substations by Using Metal Oxide Gapless Surge Arresters Connected in Parallel
Authors: Christos A. Christodoulou, Vasiliki Vita, Theodoros I. Maris
Number of views: 711
The adequate protection of the distribution transformers is a critical issue, in an effort to avoid interruption of the power supply and damages of the equipment. The installation of metal oxide gapless surge arresters at the entrance of the transformers improves their lightning performance and reduces the expected annual failure rate. However, arresters can be damaged, if the discharge current that passes through them is high enough, resulting in thermal stress of the device and possible failure. The parallel connection of arresters contributes to equal current sharing, reducing their failure probability. In the current work, the parallel combination of two metal-oxide gapless surge arresters installed at the MV side of a distribution transformer is examined, considering how the voltage – current characteristic of each arrester influences the expected voltage surges at the entrance of the transformer, the current sharing between the non-linear resistors and the arresters failure probability.