Digital protection has been widely applied in extra high voltage(EHV) lines,the current operation manner of the power system is complicated and changes frequently,and the protection are realized by software makes the protection device is difficult to understand for users,both of this cause great difficulty in the analysis of operation of digital distance protection.

Then we prove the isometrical identity and inversion formula of the solution of the wave equation.

On equal-distance sets in Euclidean Space E~n;

The power density gain and equivalent length of cylinder capillary with different lengths and radii are calculated with a simulation program.

In order to determine the Absolute neutron output of distributed pulse generators,we deduced equivalent length to deal with experimental data,according to the different layout and weighting of multiple pulse generators.