In the frame of electrohydrodynamic consideration a qualitative model, allowing to determine the basic characteristics for breakdown of non - conductive liquid in terms of macroscopic parameters of dielectric and loading electric field, is formulated. The local exciting state, caused by action of ponderomotive powers, was taken as basic one. This state is accompanied by instability of capillar waves. The question of calculation of electric strength characteristics for breakdown is also connected with ponderomotive powers action on liquid dielectric in the arbitrary inhomogeneous electric field. And in this case the electric conductivity of water and its surface tension determine the critical field intensity when the breakdown takes place. All obtained formulas show the satisfactory coincidence with the experimental data of the proper investigations and those which are in the literature.