The effect of the distance between transformer and MV arresters on the surges transferred to the LV side

The western part of the state of Rio Grande do Sul, in South Brazil, is characterized by high ground flash densities. In the period 2003-2011, lightning overvoltages accounted for about 47 % of the total number of distribution transformer failures observed in the service area of the power company AES Sul. This paper presents the results of an investigation on the influence of the distance between transformer and medium voltage arresters on the surges transferred to the secondary side. The analysis, performed through simulations using the Alternative Transients Program (ATP), shows that in general higher voltages are produced by subsequent strokes. Although the amplitudes of the voltages transferred to the secondary side tend to increase as the surge arrester approaches the transformer, the distance between these equipment should be as short as possible.