Power cables operate based on Ohm's Law and the principles of electromagnetic induction. When a voltage is applied across the ends of a power cable's conductor, an electric current is established within the conductor-in accordance with Ohm's Law, I = U/R (where I represents current, U represents voltage, and R represents the conductor's resistance)-thereby enabling the transmission of electrical energy. During this transmission process, the inherent resistance of the conductor generates Joule heating, defined by the formula Q = I²Rt (where Q represents heat energy and t represents time); consequently, it is imperative that the conductor's resistance be minimized as much as possible to reduce energy loss. The insulation layer plays a pivotal role by electrically isolating the conductor from the external environment, ensuring that the current flows strictly along the path of the conductor and preventing current leakage. The insulating material is characterized by high electrical resistance, effectively blocking the escape of current into the surrounding environment.
The shielding layer functions by harnessing the principles of electromagnetic induction. When the cable is exposed to a fluctuating external electromagnetic field, Faraday's Law of Electromagnetic Induction dictates that an induced current will be generated within the shielding layer. The magnetic field produced by this induced current opposes the direction of the external electromagnetic field, thereby neutralizing the interference that the external field would otherwise exert upon the signals or currents flowing within the cable. Simultaneously, the electromagnetic field generated by the current flowing inside the cable is confined within a specific boundary by the shielding layer; this prevents the emission of electromagnetic interference that could disrupt other external equipment, thereby ensuring the stable and efficient transmission of electrical energy by the power cable.
