Analysis of the shielding effectiveness of rectangular enclosure of metal structures with apertures above ground plane

A method of moments solution for analyzing the electromagnetic shielding properties of rectangular metal enclosures with apertures over a lossy half space which can model the ground is presented. The objects are modeled by rectangular surface patches. The roof-top basic functions are used to expand the unknown electric and magnetic currents on the surfaces of the cavity and the apertures. An effective method based on the generalized pencil-of-function (GPOF) method is developed to calculate the generalized Sommerfeld integral (GSI). With this method, the value of Greens´ function can be obtained quickly and accurately. Validation of the method is presented by comparing the calculation results with the results obtained by measurement. Finally, the method is successfully applied to calculating the shielding effectiveness of a relay cell in a substation.