Measurements and simulations of cable shielding against magnetic field induction

An experimental setup with loop configurations is applied to measure the perfonnance of cable shielding against the magnetic field induction at power frequencies. Such scheme is preferred for shielding measurements in a small test region to avoid the influences of the ground potential rises and the grounding resistances. A quasi-static two-wire transmission line model has been used to simulate and verify the experimental results of the loop circuits. Besides, to test the application of the loop configurations for practical station-to-station routing of the cables, shielding properties obtained from the loop approach are compared with those of the straight parallel circuits determined by using the Electromagnetic Transients Program (EMTP). In addition, methods for improving the shielding of the magnetic field induced voltages excited from power line faults have been investigated by using the EMTP. An approach to correct the geometrical effects of the loop configurations on the measured shielding effectiveness of the cables for the straight parallel circuits is also proposed. Cables with good shielding performance may be designed and tested by using the methods presented in this paper.