A helical charge simulation based 3-D calculation model for corona loss of AC stranded conductors in the corona cage

Yunpeng Liu,Daran Liu,Shugang Liu,Shilong Huang

doi:10.1063/1.5017244

Abstract

Corona loss generated from conductors is an indispensable factor in the design of alternating current(AC) transmission lines. Based on a helical charge simulation method, a 3-D calculation model for corona loss considering the outer strands of the conductor in the corona cage was established. Compared to the 2-D corona-loss calculation method, the calculation model proposed in this study incorporates the heterogeneity of the electric fields strength along the axial direction of the stranded conductor. Furthermore, it was also able to calculate the corona loss when the conductor had sagged. The calculation results of the LGJ-300/40 and LGJ-400/35 in the small corona cage show close agreement with the measurement results indicating that the corona-loss calculation model was accurate. In addition, the corona loss of the bundle conductors 4 × LGJ720 with sag in the UHV corona cage was also analyzed.

Highlights

In AC lines, when the field strength around the transmission line exceeds the breakdown electric field strength of air, the air near the conductor is ionized in a process, which is known as corona discharge
The phenomenon of corona loss has been studied for many years[1,2,3,4] and is of significant importance for the selection of conductors and it has been used as a criterion for measuring the operating economy of transmission lines
The experimental results showed that corona loss can be influenced by several factors including phase distance, weather conditions, conductor diameter, the number of sub-conductors, bundle spacing and surface roughness coefficients

Summary

INTRODUCTION

In AC lines, when the field strength around the transmission line exceeds the breakdown electric field strength of air, the air near the conductor is ionized in a process, which is known as corona discharge. Clade calculated the corona loss of a single conductor in a corona cage based on the assumptions of Kaptzov and Deutch, whilst ignoring the influences of space charges on the electric field direction.[13,14,15] By abandoning the Deutsch assumption, Abdel-Salam investigated single, triple, and multi-phase transmission-line corona loss, but did not consider the inhomogeneity of the electric field on the conductor surface and postulated that charges on the conductor surface were emitted uniformly.[16,17] By considering the heterogeneity of charge emissions on the conductors’ surface, Li determined the ion flow of the multi-phase and bundle conductors.[18] Liu further adopted the improved calculation model from Li and determined the corona loss of single and bundle conductors in the corona cage.[19,20]. The calculated accuracy of the model was verified through test data acquired in a small corona cage and UHV corona cage

Twisting form of the strand in the outer layer of the stranded conductor

Coordinates of the simulated helical line charges and boundary points

Corona onset and charge emission

Space charge’s migration and recombination

Calculation of corona loss and corona current

CONCLUSIONS