Since the putting in force of GOST R 55194 Electrical Equipment and Installations for a.c. Voltages from 1 to 750 kV. General Methods of Dielectric Tests, 10 years have passed. The vast majority of the provisions of GOST R 55194 still remain relevant and do not require changes. At the same time, technical progress has led to the emergence of new knowledge about the physical nature of discharge phenomena and improvement of methods for digital processing of surge voltages. All this made it necessary to modify certain provisions of this regulatory document. The above refers to the procedure for determining corrections to test surge voltages of external insulation and digital processing of lightning voltage surges with superimposed high-frequency oscillations. As a result of the accomplished studies, new formulas filled with physical content have been proposed for determining the parameter q used to determine corrections for atmospheric conditions. Recently obtained new data on experimental studies of large-scale air insulation structures, insulation systems in SF6 and transformer oil have made it possible to propose a well-grounded expression for the test voltage function k(f), used for digital processing of lightning voltage surges with superimposed high-frequency oscillations.