Research On AC Ice-melting For Optical Fiber Composite Overhead Ground Wire

Optical fiber composite overhead ground wire (OPGW) with the functional combination of communication with lightning protection for transmission line has been more and more popularly used in the power system for recent years. The OPGW is an important component for communication network of transmission line. In practical application, the icing problems of OPGW seriously affect the safe operation of power system in some areas where icing frequently appears. An effective method of OPGW ice melting is a topic key of current research and has significant engineering value.Based on present status of OPGW ice-melting, the possible problems existed in traditional ice-melting process are analyzed, they include the OPGW insulation, the high voltage induced by transmission line during ice-melting operation, as well as the electrical energy loss. An embedded ice melting structure of OPGW is suggested, in which a heater is fabricated by bifilarly twisting two polyimide enamel wires and replaces the aluminum-clad steel wire in the central layer of OPGW, the heater can thus have near zero reactance and reduce simultaneously electromagnetic influence on the surrounding environment. The main energy loss is active loss in the bifilar twisting heater, while the reactive power loss can be almost neglected.An equivalent thermal circuit is established, the temperature rise of twisted wires in OPGW is separately analytically calculated and simulated by MATLAB software. The thermal stability of optical fiber unit during heating process and ice melting time efficiency are analyzed, respectively. To verify the feasibility of the structure, ice-melting samples are fabricated and tested under laboratory conditions.In order to improve the heat transfer rate and reduce the temperature gradient in radial direction of the OPGW as well as reduce the ice-melting time, aluminum nitride (AlN) which is a kind of semiconductor with high thermal conductivity, is used to fill in the void among the wires of OPGW. By this processing, the heat created at center location can transfer to the surface of OPGW more rapidly. The simulated and experimental results show that ice melting time can be shortened 40% comparing with the situation without filling AlN. Therefore, the ice melting efficiency of OPGW can be feasibly improved.