Structure optimization for downlead cable of 110-kV insulated optical-unit phase conductor

Abstract

Currently, the structure of insulated optical-unit phase conductor (IOPPC) is gradually being employed in 10 kV and 110 kV power transmission lines, replacing the existing Optical Fiber Composition Phase Conductor (OPPC) structures. However, incidents of lines breakage have occurred in the widespread application of IOPPC downlead cables in 110 kV lines. Addressing these breakage incidents, this paper proposes a modi ed structure for the IOPPC downlead cable. Initially, nite element method is employed to calculate the electric eld intensity of both the traditional and modi ed IOPPC downlead cable structures under a 110 kV voltage, providing preliminary validation of the effectiveness of the proposed modi cation. Subsequently, power frequency withstand tests are conducted to further validate and optimize the modi ed structure. Simulation results indicate that the electric eld strength is notably higher in the air region near the parallel groove clamp of the traditional structure. The addition of a semiconductor shielding layer in the modi ed structure effectively suppresses the increase in electric eld strength. Power frequency withstand test results further con rm the inhibitory effect of the semiconductor shielding layer on electric eld intensity. However, experimental observations reveal occurrences of discharge at the cutoff point of the semiconductor shielding layer. Finally, optimization of the modi ed structure successfully eliminates the occurrence of discharge at the cutoff point of the semiconductor shielding layer. The nal chapter showed the withstand voltage test speci ed by IEC standard for the IOPPC downlead cable with the structure of the hollow aluminum ball wrapping, con rming the effectiveness of the modi ed design.