Study on characteristics of slow-front overvoltage of ±1100 kV UHVDC transmission lines

Abstract

The ±1100 kV Zhundong–Wannan ultra high-voltage direct current (UHVDC) transmission project is under construction in China, which has the highest operating voltage in the world. The length of the UHVDC overhead transmission line is greater than 3000 km. The electromagnetic transient process caused by grounding faults might have significantly impact on the overvoltage level of DC transmission line, which is crucial for the external insulation configuration of the overhead transmission line. This paper presents a detailed electromagnetic transient simulation model for the UHVDC transmission system using an open-loop extinction angle control principle. The simulation results demonstrate that the single pole grounding fault into a bipolar system causes the most serious damage. The maximum overvoltage is 1.628 p.u. and the 2% statistic overvoltage is 1.635 p.u., while the reference value is 1122 kV. The influence of DC filters for line overvoltage is also analysed here. Furthermore, results show that adding a no gap line arrester at the midpoint of transmission line can suppress line overvoltage, while the maximum overvoltage reduces by 0.138 p.u. The results obtained provides a reference for the optimisation of the external insulation configuration.

Keywords

• HVDC power transmission
• power overhead lines
• power transmission faults
• earthing
• insulation
• optimisation
• slow-front overvoltage
• electromagnetic transient process
• grounding faults
• external insulation configuration
• open-loop extinction angle control principle
• single pole grounding fault
• gap line arrester
• electromagnetic transient simulation model
• Zhundong–Wannan ultrahigh-voltage direct current transmission project
• UHVDC overhead transmission line system
• China
• bipolar system
• DC filters
• line overvoltage suppression
• optimisation
• voltage 1122.0 kV