Vector shift(VS)is one of the typical methods used for islanding detection in distributed generations.This paper investigates the impact of both the active power imbalance and load variation on VS method.The investiga...Vector shift(VS)is one of the typical methods used for islanding detection in distributed generations.This paper investigates the impact of both the active power imbalance and load variation on VS method.The investigation was conducted via simulation test in the power system dynamic simulation laboratory of Shandong University.The results show that it will take longer time for the VS relay to detect islanding state with the decrease of active power imbalance.In some cases,the vector shift angle is smaller than the setting and VS method would not be able to detect islanding state.In addition,the performance of VS method is impacted by the load variation in normal operation in which the distributed generator is operated in parallel with the main grid.The simulation results show that VS method would cause nuisance tripping if the load changes sharply. It can be summarized that VS method would be unable to reliably discriminate islanding state and normal system disturbances in some cases.展开更多
Ice detecting and measuring technologies used and developed for high voltage transmission lines are introduced in this paper. The Icing Rate Meter developed by Hydro-Quebec, working with the magnetostriction principle...Ice detecting and measuring technologies used and developed for high voltage transmission lines are introduced in this paper. The Icing Rate Meter developed by Hydro-Quebec, working with the magnetostriction principle and regulated by an electronic control system is analyzed and the resonant piezoelectric transducers operated by a microprocessor-controlled electronic circuitry is also analyzed in great detail. It shows that the Icing Rate Meter (IRM) developed by Hydro-Quebec can record the occur- rence and duration of icing events, but has two limitations: information on changes in the rate of icing within each hour is lost and the amount of time consumed during heating cycles is not taken into account. A resonant piezoelectric ice detector can automatically and distinctly sense ice and water films up to 0.5 mm thick. It is a smart ice detection system, which might be used widely.展开更多
文摘Vector shift(VS)is one of the typical methods used for islanding detection in distributed generations.This paper investigates the impact of both the active power imbalance and load variation on VS method.The investigation was conducted via simulation test in the power system dynamic simulation laboratory of Shandong University.The results show that it will take longer time for the VS relay to detect islanding state with the decrease of active power imbalance.In some cases,the vector shift angle is smaller than the setting and VS method would not be able to detect islanding state.In addition,the performance of VS method is impacted by the load variation in normal operation in which the distributed generator is operated in parallel with the main grid.The simulation results show that VS method would cause nuisance tripping if the load changes sharply. It can be summarized that VS method would be unable to reliably discriminate islanding state and normal system disturbances in some cases.
文摘Ice detecting and measuring technologies used and developed for high voltage transmission lines are introduced in this paper. The Icing Rate Meter developed by Hydro-Quebec, working with the magnetostriction principle and regulated by an electronic control system is analyzed and the resonant piezoelectric transducers operated by a microprocessor-controlled electronic circuitry is also analyzed in great detail. It shows that the Icing Rate Meter (IRM) developed by Hydro-Quebec can record the occur- rence and duration of icing events, but has two limitations: information on changes in the rate of icing within each hour is lost and the amount of time consumed during heating cycles is not taken into account. A resonant piezoelectric ice detector can automatically and distinctly sense ice and water films up to 0.5 mm thick. It is a smart ice detection system, which might be used widely.
