Design of Shielded Enclosures, Especially for High-Voltage Laboratories

摘要

It is argued that a shielded enclosure acts as a complicated receiving antenna for incoming electromagnetic waves, so it is incorrect to model an enclosure as a flat metallic sheet of infinite extent, as is done in the traveling wave concept to calculate shielding effectiveness. The field method and the circuit method are more useful calculation models, because they are based on currents circulating around the entire volume enclosed. The field method gives correct values, but is rather complicated. The circuit method offers more insight into the shielding mechanism, especially at low frequencies. The required attenuation is found by considering measuring circuits for the detection of partial discharges. The resulting attenuation is not only a matter of a correct choice of wall material and thickness, but also depends on the construction of doors and joints, and on filtering of the electrical supply.