Improvement Measures of Armor Rods Segment of Overhead Ground Wire Based on Multi-field Coupling

Under the action of power frequency short-circuit current, the armor rods segment of overhead ground wire may break due to suffering from high temperatures. It is necessary to optimize the structure of armor rods segment. Based on the structural characteristics of conventional armor rods segment, the structure of step-type armor rods segment was proposed in this paper. In order to verify the effectiveness of improvement measures, electromagnetic thermal coupling simulation models of two armor rods segments were built, in which the length of conductor of model was determined by the boundary conditions of electromagnetic field and temperature field. The current density distribution and transient temperature distribution of two armor rods segments under the action of power frequency short-circuit current were analyzed by simulation models. Then, combined with the simulation results, an evaluation method for the mechanical properties of ground wire in which the uneven temperature distribution was taken into consideration was proposed. This method was used to compare the tensile strength and rated breaking force of ground wires at the two segments. Finally, the transient temperature rise experiments were designed to verify the accuracy of simulation models. The research results show that the simulation models are accurate enough and the error is less than 6%. Compared with conventional segment, step-type armor rods segment can avoid the heating bottleneck point concentrated on the same radial section of ground wire. The rated breaking force of ground wire at the segment gradually decreases with the increase of short-circuit current, especially for conventional armor rods segment. Under the same condition, the mechanical bearing capacity of ground wire at the step-type armor rods segment is higher than that of conventional armor rods segment, which can prevent the ground wire from breaking at high temperatures to some extent. © 2021, High Voltage Engineering Editorial Department of CEPRI. All right reserved.