Correct detection and identification of single-phase to-ground faults not effectively grounded in distribution systems is a major challenge for protection engineers.This paper proposes a novel traveling wave based pro...Correct detection and identification of single-phase to-ground faults not effectively grounded in distribution systems is a major challenge for protection engineers.This paper proposes a novel traveling wave based protection method to solve this problem.The proposed method compares the polarities of current and voltage traveling waves measured immediately after the fault inception to determine the fault direction.Nuisance tripping is avoided by using the power frequency voltages detected on the busbar to inhibit operation.The power frequency voltages ensure that the system does not mal-operate due to noise and also provide discrimination for phase-to-phase and three-phase faults.The wavelet transform and modulus maxima theories are used to extract the polarity of traveling waves measured at the relaying point.The simulation studies demonstrate correct operation of protection,which is independent of fault distance,fault inception angle,fault path resistance,and the method used for neutral grounding.展开更多
An islanding detection method in ungrounded power distribution system based on single-phase operating mechanisms of the circuit breaker(CB)is proposed in this paper.When CB opens three phase circuits to form an island...An islanding detection method in ungrounded power distribution system based on single-phase operating mechanisms of the circuit breaker(CB)is proposed in this paper.When CB opens three phase circuits to form an island,one phase circuit is opened firstly and the other two phase circuits are opened secondly after certain duration.During the period when only one phase circuit is opened,negative sequence voltage with certain duration is obtained at DG side because of the asymmetric operation of the system.After all three phase circuits are opened,the voltage variation direction of the two phases that are secondly disconnected from the grid follows the voltage variation direction of the firstly disconnected phase.Based on the above voltage characteristics,an islanding detection scheme is proposed to identify genuine islanding from system disturbances.The performance of the proposed scheme is tested in PSCAD/EMTDC using a 10 kV distribution network with synchronous DG interconnection.Simulation results demonstrate the proposed method is effective and reliable to detect islanding formation.展开更多
Over the past decade,China has undertaken substation intellectualization of more than 2000 substation operations in three stages.Much experience has been achieved during this developmental period.In this paper,the sta...Over the past decade,China has undertaken substation intellectualization of more than 2000 substation operations in three stages.Much experience has been achieved during this developmental period.In this paper,the status of smart substation development in China is systematically presented,as well as future directions of the smart substation,such as adoption of the hierarchical protection and control system.展开更多
基金financed by the National Natural Science Foundation of China under Grant 50930072,51120175001,51477084in part by the Beijing Natural Science Foundation under Grant 3152016.
文摘Correct detection and identification of single-phase to-ground faults not effectively grounded in distribution systems is a major challenge for protection engineers.This paper proposes a novel traveling wave based protection method to solve this problem.The proposed method compares the polarities of current and voltage traveling waves measured immediately after the fault inception to determine the fault direction.Nuisance tripping is avoided by using the power frequency voltages detected on the busbar to inhibit operation.The power frequency voltages ensure that the system does not mal-operate due to noise and also provide discrimination for phase-to-phase and three-phase faults.The wavelet transform and modulus maxima theories are used to extract the polarity of traveling waves measured at the relaying point.The simulation studies demonstrate correct operation of protection,which is independent of fault distance,fault inception angle,fault path resistance,and the method used for neutral grounding.
文摘An islanding detection method in ungrounded power distribution system based on single-phase operating mechanisms of the circuit breaker(CB)is proposed in this paper.When CB opens three phase circuits to form an island,one phase circuit is opened firstly and the other two phase circuits are opened secondly after certain duration.During the period when only one phase circuit is opened,negative sequence voltage with certain duration is obtained at DG side because of the asymmetric operation of the system.After all three phase circuits are opened,the voltage variation direction of the two phases that are secondly disconnected from the grid follows the voltage variation direction of the firstly disconnected phase.Based on the above voltage characteristics,an islanding detection scheme is proposed to identify genuine islanding from system disturbances.The performance of the proposed scheme is tested in PSCAD/EMTDC using a 10 kV distribution network with synchronous DG interconnection.Simulation results demonstrate the proposed method is effective and reliable to detect islanding formation.
基金National Natural Science Foundation of China under Grant 51120175001Key Project of Smart Grid Technology and Equipment of National Key Research and Development Plan of China under Grant 2016YFB0900600Science and Technology Project of State Grid Corporation of China under Grant GWKJ2013-005.
文摘Over the past decade,China has undertaken substation intellectualization of more than 2000 substation operations in three stages.Much experience has been achieved during this developmental period.In this paper,the status of smart substation development in China is systematically presented,as well as future directions of the smart substation,such as adoption of the hierarchical protection and control system.
