Abstract: Devices and systems of inductive-capacitive (LC) coil-resonators that can be embedded easily inside high-voltage insulation discs are provided. Each LC coil-resonator comprises spiral conductive tracks fabricated or printed in the form of at least two layers of planar spiral windings on electrically non-conductive materials. The planar conductive windings on at least two parallel layers may be connected to form a closed winding. The distributed inductance associated with the planar spiral windings and the distributed capacitance between the layers of the conductive tracks form an equivalent LC coil-resonator. When these LC coil-resonators are embedded in some or all of the insulation discs in a high-voltage insulation rod, they form the relay coil-resonators for wireless power transfer.