Research on Parameter Collaborative Configuration of DC Circuit Breaker and DC Fault Current Limiter

Fault current suppression is the key technology to ensure the safe operation of the DC power distribution system. In order to realize the parameter collabora-tive configuration of the DC circuit breaker and the DC current limiter and improve the fault current suppression capability, the fault current suppression mechanism of the DC power distribution system is revealed based on the circuit model. Then, based on the mathematical model of the DC breaker, the characteristic parameters of DC breaking are extracted, and then the influence of different characteristic parameters on the breaking characteristics of fault current is studied. Finally, the mathematical model of the collaborative process between DC circuit breaker and DC current limiter is established. The charac-teristic parameters of fault current collaborative suppression are extracted. The coupling effects of different characteristic parameters on the fault current col-laborative suppression are studied. The principle of collaborative configuration of DC circuit breaker and DC current limiter is proposed, and the collaborative suppression ability of DC circuit breaker and DC current limiter to fault current is fully exploited to ensure the safe and reliable operation of the DC power distribution system.

Planning and analysis of the demonstration project of the MVDC distribution network in Zhuhai

The DC distribution system is an important development direction of the distribution system,which can improve the reliability and the quality of the power supply,and support the new energy,the energy storage,the electric vehicles,and the flexible access of AC and DC loads to grid.To realize the demonstration application of the DC distribution technology,China's first demonstration project of the medium voltage DC distribution network will be built in Zhuhai,Guangdong Province to support the construction of the city energy internet.First,this paper analyzes the demand of the DC distribution network project,and puts forward the construction content and construction target.Then,it designs and analyzes the electrical connection mode,system operation mode,and startup and shutdown mode of the DC distribution network,and proposes the overall project construction plan.Finally,it conducts the specific project design and analysis,which mainly in elude the selection of equipment such as inverters,DC transformers and DC circuit breakers,the design and analysis of the DC control and protection system,the design and analysis of the overvoltage protection and the configuration scheme of the lightning arrester,and analysis of the system transient characteristics.The design and analysis of the engineering program is a combination of China's distribution network engineering practice and technical characteristics,which lays a solid foundation for the advancement of the DC power distribution technology in China,and has reference value and demonstration effect for the design and construction of other projects.

Development and prospect of direct‐current circuit breaker in China

The direct‐current circuit breaker(DCCB)is the most ideal choice for DC fault isolation in DC grids.Despite a late start,China's research and development on the DCCB have made outstanding achievements.This article provides a brief glance of current China's DCCB development status.It begins by sorting out the technical route according to the topology of DCCB.Then it systematically summarises both mechanical and hybrid DCCBs with focussing on the aspects of topology structure and principle,key technology and characteristics,prototype development and application.It is apparent that Chinese scientists and engineers confronted the worldwide problem of large capacity DC breaking,and put forward a comprehensive solution which consists of an innovative topology structure based on coupled negative voltage circuit,breaking throughs on the key technologies such as highly controllable and reliable fault current commutation,millisecond‐level ultra‐fast and efficient electromagnetic repulsion mechanism,high tolerance and high stability power electronic switch,low residual voltage and fast response energy consumption device,etc.The article states that the world's first set of hybrid high‐voltage(HV)DCCB,and the first set of mechanical HV DCCB have been developed.These DCCBs will soon be deployed to the DC grids which have the highest voltage levels therefore require the strongest breaking capacity.These achievements are leading the world in the development and application of DCCB.The article also discusses the overall development trends of DCCB in the areas of new topologies,key techno-logical breakthroughs and application scenarios,etc.These discussions serve as references for DCCB's future technological advancement and its ever‐expanding applications.

Survey of recent progress on lightning and lightning protection research

Lightning and lightning induced effects have significant influence on many aspects affecting the public, whichmakes the research of lightning and lightning protection very important. However, due to the strong randomness andcomplex discharge mechanisms of lightning, the understanding of lightning is still far from satisfactory. On the basis ofthe International Conference on Lightning Protection 2014, this study gives a review of recent progress on lightningand lightning protection research covering the following aspects: lightning locating and observation, lightning physics,lightning electromagnetic transients, and lightning protection for various systems. The goals of this study are to givereaders an overall introduction to the recent progress in lightning and lightning protection research, and to motivatethem to conduct further studies to address the unsolved problems in lightning-related research.

HV isolated power supply system for complex multiple electrical potential equipment in 500kV hybrid DC breaker

High-voltage direct current circuit breakers(HVDC CB)are one of the key technologies of multi-terminal DC systems and DC grids.Different from other equipment that use a large number of power electronic devices,the HVDC CB cannot obtain its power from the primary system at high potential,making the power supply of the complex multiple electrical potential equipment in HVDC CB a challenge.In this study,the authors propose an HV isolated power supply system based on the multi-output high-frequency isolated power supply unit and the cascaded isolation transformer network.This power supply system can support the 500 kV CB to turn-off 25 kA current with 800 kV overvoltage.

Precise multi‐dimensional temperature‐rise characterisation of switchgear based on multi‐conditional experiments and LPTN model for high‐capacity application

As the power load increases, the capacity of switchgear becomes larger so the problem of overheating of switchgears becomes more significant. Whether the switchgears operate safely and reliably affects the reliability and economy of the entire power system. Different methods have been tried to study the thermal problems of switch-gears. However, there are few experimental studies on the switchgear entity. In this study, a series of temperature rise tests were carried out on medium‐voltage high‐ca-pacity switchgear to explore laws of temperature rise. First, five groups of multi‐con-ditional experiments were carried out including changes of the load current, ventilation conditions and loop resistance. Then, multi‐dimensional temperature‐rise characterisa-tion was analysed based on the experimental results and the relating theory. Finally, a circuit‐based lumped‐parameter thermal network (LPTN) model was developed by analysing the heat dissipation in switchgear and used to determine the steady‐state temperature distribution of the switchgear. The model is verified by comparing the simulation results with the experimental results.