The safety in the high voltage substations relies on the integrity of its grounding grid. A single discontinuity at any part of the grounding grid may cause an increase in touch or step potentials, resulting in the exposure of the personnel to a hazard of critical electric shock. In addition, such a discontinuity may lead to malfunction of the protection devices leading to the gratuitous tripping of circuit breakers. In this paper, a cost-effective, reliable and meticulous measurement will be presented for the evaluation of the integrity of an existing substation grounding grid. The method involves injecting a sinusoidal current (in the order of few Amps) into the grounding grid at a frequency of 400 Hz and the operator walks along different magnetic field profiles while holding an electromagnetic sensor. To verify the correctness of the measurement readings, a comparison is performed with simulation results in the CDEGS software for the same location and profiles. A mathematical analysis of the grounding grid was undertaken to calculate the expected magnitude of currents and magnetic fields, when damaged or integrated elements are present within the grounding grid. It was found that the current distribution of damaged horizontal elements is uneven in comparison with elements without failure and/or mechanical degradation. Also, the magnetic field along the profile of a damaged element shows a noticeable dip compared to an expected peak for elements without failure and/or mechanical degradation. Considering all these factors, the integrity of an existing substation grounding grid can be evaluated. Finally, a flowchart for the sequence of steps that should be followed during grounding grid investigations will also be presented.