Interruption Characteristics of High-speed Switches in 500 kV Fault Current Limiter with High Coupled Split Reactance

A 500 kV high-voltage AC fault current limiter(FCL)based on a high coupled split reactor(HCSR)is pro-posed by the National key R&D project team.Low impedance under normal conditions and high impedance under short-circuit conditions are accomplished by the cooperation of HCSR and high-speed switches.High-speed switches play an important role in current limiting processes,thus interruption characteristics of the high-speed switch in the 500 kV FCL are studied in this paper.The simulation model of the FCL and the external equivalent power grid are established.The short-circuit current and recovery voltage characteristics of the high-speed switch in FCL are simulated.The results show that maximum DC component of the short-circuit current of the high-speed switch reaches 91%,the maximum peak value is 118 kA,and the longest arcing time is 14.8 ms.There is a discontinuity in the curve of the short-circuit current peak and arcing time as a function of the short-circuit occurrence time;the peak recovery voltage of a single break of the high-speed switch has a maximum value of 87.5 kV under a three-phase ungrounded short-circuit condition,and the rate of rise of recovery voltage is o.22 kV/s.The recovery voltage peak shows a period change with the short-circuit occurrence time,and the period is 10 ms.The effects of the shunt capacitor value and short-circuit ground resistance on the recovery voltage of high-speed switching are also studied.The research can be used for reference by R&D personnel and testersof500kVFCLs.Index Terms-Fault current limiter(FCL),high coupled split reactor(HCSR),high-speed switch,interruption characteristics,short circuit current.

Two-dimensional transition metal dichalcogenides for post-silicon electronics

Rapid advancements in information technology push the explosive growth in data volume,requiring greater computing-capability logic circuits.However,conventional computing-capability improving technology,which mainly relies on increasing transistor number,encounters a significant challenge due to the weak field-effect characteristics of bulk siliconbased semiconductors.Still,the ultra-thin layered bodies of two-dimensional transition metal dichalcogenides(2D-TMDCs)materials enable excellent field-effect characteristics and multiple gate control ports,facilitating the integration of the functions of multiple transistors into one.Generally,the computing-capability improvement of the transistor cell in logic circuits will greatly alleviate the challenge in transistor numbers.In other words,one can only use a small number,or even just one,2DTMDCs-based transistors to conduct the sophisticated logic operations that have to be realized by using many traditional transistors.In this review,from material selection,device structure optimization,and circuit architecture design,we discuss the developments,challenges,and prospects for 2D-TMDCs-based logic circuits.

On the charged aerosols generated by atmospheric pressure non‐equilibrium plasma

Recently,charged aerosols are used widely in many applications,such as fog elimination,inactivation of airborne viruses and so on.Atmospheric pressure non‐equilibrium plasma(APNP)have become an efficient way to generate charged aerosols.Except the traditional pin‐plate or wire‐plate APNP sources,the new APNP sources such as large scale corona discharge system and air plasma jet array are introduced.These sources can increase the ion density in open air and generate adjustable large plasma plume,which are helpful in increasing the charging efficiency on aerosols.Although the interactions between plasma and aerosols is quite complicated,the preliminary study suggests that the diffusion charging dominates aerosols below 0.1μm,field charging dominates aerosols larger than 1μm,and the photo charging also contributes to aerosols charging.These reactive charged aerosols have shown their potential in the artificial rain enhancement,biomedicine,and ma-terial processing.Finally,challenges and opportunities for theoretical,experimental,and application research in related cross‐disciplinary areas are presented to stimulate critical discussions and collaborations in the future.

Analysis of influence of a novel inductive fault current limiter on the circuit breaker in 500 kV power system

A contribution to the engineering application of a proposed 500 kV fault current limiter(FCL)is presented.A new type of FCL composed of a highly coupled split reactor(HCSR)and fast switches is proposed.When the circuit breaker(CB)in series with the FCL in the 500 kV power system interrupts the limited fault current,the rate of rise of the recovery voltage(RRRV)reaches a value much higher than the rated value.Based on a simplified equivalent single‐phase circuit,the influence of the new FCL on the interruption procedure of the CB is simulated and discussed.The simulation results show that the high RRRV is caused by high‐frequency resonant oscillations between the HCSR and its parasite capacitance.Analysis indicates that when the reactance of the FCL is close to the short circuit reactance of the system,the RRRV will reach the highest value.To solve this issue,we proposed installing a shunt capacitor with the FCL.Simulation results showed that the RRRVunder all fault modes could be restrained to below the rated value by introducing a certain shunt capacitor.