SEISMIC QUALIFICATION OF TRANSFORMER HIGH-VOLTAGE BUSHINGS

The paper is born as a contribution to the IEC 36A Working Group 2 ''S eismic qualification of bushings'' in order to evaluate the coefficien ts K (amplification factor between the ground and the transformer bush ing flange) and R (response factor of the bushing itself) as defined i n the LEC 61463 [1]. These coefficients allow the definition of the se ismic severity at the flange level to be used for static calculations and vibrational tests on high voltage bushings. For the evaluation of these coefficients both experimental onsite dynamic tests and numerica l finite element analyses have been performed for a 160MVA, 230/135kV power transformer [2]. The natural frequencies and the seismic respons e of the whole transformer (tank, oil conservator and HV bushings), su bjected to different earthquakes, have been calculated. At last a comp arison between the calculated coefficients (K and R) and those establi shed by the IEC 61463 is illustrated.