Attenuation of Power Frequency Magnetic Fields in Buildings Due to Induced Currents in Structural Steel

Jim Hoburg, Department of Electrical & Computer Engineering

Magnetic fields caused by electric utility power lines outside buildings are sometimes reduced by induced currents in the structural steel members used in building construction. This effect motivates an ongoing research program, sponsored by the Electric Power Research Institute.

To date, we have created modeling tools at two separate levels: 1)calculations of resistance and reactance per unit length of individual structural steel members (e.g. I-beams) on the basis of cross-sectional geometry and steel material properties (magnetic permeability and electrical conductivity), and 2)calculations of induced currents and resultant magnetic shielding in the large scale interconnections of members that describe building structures.

This CIT Honors Research Project will involve:

• Development of a database of steel member geometries and material parameters, based upon data from the American Institute of Steel Construction. The database will provide all of the data that is needed to evaluate shielding on the basis of the modeling tools.
• Development of a series of case studies, whereby a rich set of examples of realistic large scale building structures will be evaluated. The case studies will extensively document ways in which basic properties and mechanisms translate into practical shielding characteristics
• Evaluation of the results from complex building case studies on the basis of simple analytic models, so as to obtain fundamental insights into the nature of dependences upon all relevant parameters and mechanisms.