In order to solve the power supply problem of on-line monitoring system for underground power cable

an energy-harvesting coil using the magnetic field around the cable was developed. The energy pick-up coil was designed to be cylindrical structure and could be applicable to the power cables with different voltage levels. The Mn-Zn ferrite material with high initial permeability was used as the coil core

and the theoretical calculation and software simulation were performed.Meanwhile

the experimental results were verified. Thereby

the structure of the pick-up coil

the core material

the number of coil turns

and the output circuit management were confirmed. The results show that the energy-harvesting system can normally operate under a 35 kV underground power cableand in the range of 20～700 A of current.Moreover

the energy-harvesting system can output +5 V and +3.3 V voltage

supplying a stable operation of circuit within a burden of 500 mW/min.