Applying Low-Residual-Voltage Surge Arresters to Suppress Overvoltages in UHV AC Systems

Introduction

1000 kV or above UHV AC systems have been built in some countries such as Russia, Japan and Italy, and have been in commercial operation in China since 2009. As of 2021, China has built a total of 30 UHV AC lines and UHV DC lines, and the cumulative UHV line length has reached 40000 km.

Overvoltage level plays a decisive role in the selection and manufacturing of the UHV power apparatus, which directly determines the manufacturing cost and technical limitations of the UHV power systems. As was the case for EHV systems, practical ways to deeply suppress the overvoltages in UHV systems were needed to reduce the construction costs.

The performance improvement of surge arresters results in better protection properties and consistently lower overvoltage level in power systems than conventional alternatives such as impedance-matching closing and opening resistors in circuit breakers. Some advantage can be observed from the significant change in insulation levels of power apparatus when ZnO (zinc-oxide) surge arresters replaced SiC (silicon carbide) technology. Further advantage can be derived from improved ZnO arrester materials and configurations to meet UHV design goals.

The residual voltage is a key parameter of a surge arrester when considering the overvoltage suppression capability. If the residual voltage of a surge arrester is reduced, the overvoltage would be suppressed to a lower level, and the manufacturing costs of high voltage power apparatus, especially the UHV power apparatus, will be decreased. China and Japan are developing low-residual-voltage surge arresters in recent years, including surge arresters with low-residual-voltage metal-oxide varistors (MOVs), low-rated-voltage arresters, and controllable surge arresters.

Considerable work on ZnO varistors and surge arresters have been completed in CIGRE SC A3 such as Technical Brochures 693 and 696. Currently WG A3.39 is investigating the field performance on UHV metal-oxide surge arresters. These works formed the fundamental starting points for this working group.

The objective of this working group therefore is to summarize the state of low-residual-voltage surge arresters, including advanced MOV technology, and analyse the application effects of different kinds of low-residual-voltage surge arresters for 1000 kV UHV AC systems on suppressing switching and lightning overvoltages.

This report studied the effects of different measures (the closing resistors for circuit breakers, the surge arresters with low-rated-voltage, the surge arresters with low-residual-voltage, and the controllable surge arresters) and different methods (installing closing resistors for circuit breakers alone, installing both the surge arresters in substations and closing resistors in circuit breakers, and installing another group or...