Transient electromagnetic response of frequency-dependent multiconductor underground cables

This paper provides a procedure for calculation of transient electromagnetic fields in the vicinity of underground cables buried in lossy ground. In the proposed procedure, it is assumed that the cable behaves as a chain of small dipoles. The electric and magnetic fields at any observation point are derived by summing up the contribution of all dipoles. The per-unit-length parameters of the underground cable are approximated using a commonly-used formulation in power system simulation. A modified finite-difference time-domain technique is applied to find the current passing through each segment of the excited cable. Two frequency-domain formulations for calculation of electromagnetic radiation from a horizontal electric dipole are implemented and compared. The time-domain solution is obtained using Fourier and Inverse Fourier transforms. Finally, the effects of conductivity of the ground, insulator thickness, and the source-to-observation-point distance on the shape and magnitude of transient electric and magnetic field waveforms are studied.