Multi-Physical Coupling Field Study of 500 kV GIL: Simulation, Characteristics, and Analysis

Haiqing Niu,Xin Luo,Zeming Chen,Xiaoxiao Li,Bo Yang,Huang Zhang,Xiaoliang Zhuang

doi:10.1109/access.2020.3009694

Abstract

With the construction of a large number of hydropower stations, transmission lines crossing a river and urban utility tunnels, gas insulated transmission line (GIL) has been applied widely due to its large transmission capacity, low environmental impact and high reliability. Accurate modelling of physical quantities and their characteristics of GIL provides a theoretical basis for its design and operation, which is of great significance to ensure the safety and reliability of GIL operation. The mathematical model and their relationship of GIL multi-physical fields are analyzed at first, upon which simulation model of GIL is built. Secondly, multi-physical coupling field model of electric, magnetic, thermal, fluid and stress field for GIL is studied, while simulation results are basically in consistent with experimental data to verify effectiveness of the model. Thirdly, distribution of multi-physical fields and their relationship are simulated and analyzed, while proximity effect, edge effect and compression factor of GIL multi-physical field are discussed. The results show that the radial temperature inside GIL is higher at the top, lower at the bottom, leading to uneven distribution of thermal expansion displacement, while the axial temperature distribution is basically uniform, which falls firstly and then rises near basin insulator thus results in edge effect. Proximity effect leads to asymmetric distribution and a slight increase of temperature inside GIL as well as a dramatic increase of air velocity around GIL. In addition, when ambient temperature is lower than -5 °C, the compression factor is much lower than 1 and the effect of compression factor should be considered in simulation.

Highlights

Gas Insulated Transmission Line (GIL) is a high-voltage power transmission equipment, insulated by SF6 gas or SF6 mixture or compressed air, with enclosures and conductors arranged coaxially [1]
Since metal enclosure of GIL is grounded, there is no electromagnetic proximity effect between adjacent GIL, the analysis of proximity effect in this paper focuses on thermal-fluid field under GIL multiphase parallel operation, which is a further consideration for GIL actual operation
EDGE EFFECT AND INFLUENCE OF ELEMENT LENGTH Axial temperature distribution of GIL enclosure is basically uniform with a slight change near basin insulators at both terminals, which results in edge effect

Summary

INTRODUCTION

Gas Insulated Transmission Line (GIL) is a high-voltage power transmission equipment, insulated by SF6 gas or SF6 mixture or compressed air, with enclosures and conductors arranged coaxially [1]. During GIL operation, heat is generated when current flows through its conductor which results in the temperature rise in simulation domain, gas flow and thermal expansion of conductor and enclosure. C. SIMULATION RESULTS OF ELECTRIC AND MAGNETIC FIELDS When phase voltage is 289 kV, conductor current is 5600 A and SF6 gas pressure is constant 0.35 MPa (the following analysis for 500 kV GIL follows this condition unless otherwise specified), distribution of electric field and magnetic. B. EDGE EFFECT AND INFLUENCE OF ELEMENT LENGTH Axial temperature distribution of GIL enclosure is basically uniform with a slight change near basin insulators at both terminals, which results in edge effect. Note that if one focuses on the middle temperature, that is the highest, the edge effect on middle temperature can be ignored when GIL element length exceeds 7.5 m

COMPRESSION FACTOR

Findings

CONCLUSION