At present the detecting of ultra high voltage direct current (UHVDC) earth electrode frequently uses manual inspection. This method can't get the real-time operational data of the earth electrodes, and meanwhile,...At present the detecting of ultra high voltage direct current (UHVDC) earth electrode frequently uses manual inspection. This method can't get the real-time operational data of the earth electrodes, and meanwhile, the labor cost is very high. In order to satisfy the security needs of UHVDC, this paper designs an on-line monitoring system for UHVDC earth electrode. By 3G wireless communication-technologies, the system can monitor remotely many kinds of data such as the value of the grounding current, water level of the observation well, soil temperature and humidity near the earth electrode, the micro-climate around the earth electrode site, video data, etc. Through analyzing the datum, the system has broad prospect on fault detection and life evaluation of the UHVDC earth electrode.展开更多
Multi-terminal direct current based on a modular multilevel converter(MMC-MTDC)has received more attention due to the advantages of large capacity and high flexibility.However,the current traveling wave protection sch...Multi-terminal direct current based on a modular multilevel converter(MMC-MTDC)has received more attention due to the advantages of large capacity and high flexibility.However,the current traveling wave protection schemes adopted by the MMC-MTDC DC project are not sufficiently sensitive to high-impedance faults.To solve this problem,this paper first analyzes the characteristics of the first traveling wave of the fault on the DC transmission line and derives the expressions of the first traveling wave of the fault when the DC transmission line has an internal and external fault.Subsequently,the line frequency characteristic is used to simplify the traveling wave expression and construct the fault coefficient.Finally,the principle of single-ended traveling wave protection based on the fault coefficient is proposed.Simulation results show that the protection principle has a strong ability to withstand transition resistance and noise interference.展开更多
Hybrid DC transmission technology is used in new energy transmission due to its advantages of large capacity and long distances.Line-commutated converter-voltage source converter-multi-terminal DC(LCC-VSC-MTDC)is one ...Hybrid DC transmission technology is used in new energy transmission due to its advantages of large capacity and long distances.Line-commutated converter-voltage source converter-multi-terminal DC(LCC-VSC-MTDC)is one of the more important development directions in future power grids.But the multi-terminal high voltage direct current system has problems of inconsistent boundary characteristics,inconsistent control,and fault response characteristics,which places higher requirements on the protection scheme.A protection scheme based on the undistorted factor is proposed to ensure the safe operation of the system.First,the inconsistent line mode voltage attenuation characteristics of different fault locations are used to construct the undistorted factor.Subsequently,the undistorted factor is used to identify fault.The advantage of this scheme is that it remains unaffected by boundary elements,control strategies,and distributed capacitance.Finally,the LCC-VSC-MTDC model verifies the correctness and superiority of the proposed protection scheme.展开更多
文摘At present the detecting of ultra high voltage direct current (UHVDC) earth electrode frequently uses manual inspection. This method can't get the real-time operational data of the earth electrodes, and meanwhile, the labor cost is very high. In order to satisfy the security needs of UHVDC, this paper designs an on-line monitoring system for UHVDC earth electrode. By 3G wireless communication-technologies, the system can monitor remotely many kinds of data such as the value of the grounding current, water level of the observation well, soil temperature and humidity near the earth electrode, the micro-climate around the earth electrode site, video data, etc. Through analyzing the datum, the system has broad prospect on fault detection and life evaluation of the UHVDC earth electrode.
基金supported by the National Natural Science Foundation of China-State Grid Joint Fund for Smart Grid(No.U2066210).
文摘Multi-terminal direct current based on a modular multilevel converter(MMC-MTDC)has received more attention due to the advantages of large capacity and high flexibility.However,the current traveling wave protection schemes adopted by the MMC-MTDC DC project are not sufficiently sensitive to high-impedance faults.To solve this problem,this paper first analyzes the characteristics of the first traveling wave of the fault on the DC transmission line and derives the expressions of the first traveling wave of the fault when the DC transmission line has an internal and external fault.Subsequently,the line frequency characteristic is used to simplify the traveling wave expression and construct the fault coefficient.Finally,the principle of single-ended traveling wave protection based on the fault coefficient is proposed.Simulation results show that the protection principle has a strong ability to withstand transition resistance and noise interference.
基金supported by the National Natural Science Foundation of China-State Grid Joint Fund for Smart Grid(No.U2066210).
文摘Hybrid DC transmission technology is used in new energy transmission due to its advantages of large capacity and long distances.Line-commutated converter-voltage source converter-multi-terminal DC(LCC-VSC-MTDC)is one of the more important development directions in future power grids.But the multi-terminal high voltage direct current system has problems of inconsistent boundary characteristics,inconsistent control,and fault response characteristics,which places higher requirements on the protection scheme.A protection scheme based on the undistorted factor is proposed to ensure the safe operation of the system.First,the inconsistent line mode voltage attenuation characteristics of different fault locations are used to construct the undistorted factor.Subsequently,the undistorted factor is used to identify fault.The advantage of this scheme is that it remains unaffected by boundary elements,control strategies,and distributed capacitance.Finally,the LCC-VSC-MTDC model verifies the correctness and superiority of the proposed protection scheme.
