Experimental Investigation of Magnetic Field Shielding Techniques and Resulting Current Derating of Underground Power Cables

The paper presents an experimental investigation on the efficiency of different underground transmission/distribution line magnetic shielding techniques. Measurement results of magnetic field and temperature rise around the cable conductors are shown. An analysis of the thermal effects of each shielding technique on the line power capacity is presented. The experiments were performed on a test site where a real 138-kV underground cable section was built. The results provide useful information that can guide the designer when choosing the most suitable shielding technique according to the required shielding factor taking into account its impact on the line-rated power.