To ensure their sound and continuous operation to the greatest extent,VSC-based DC girds have extremely stringent requirements for transmission line relay protection.In terms of guaranteeing their reliability,accurate...To ensure their sound and continuous operation to the greatest extent,VSC-based DC girds have extremely stringent requirements for transmission line relay protection.In terms of guaranteeing their reliability,accurate identification of lightning strikes on DC transmission lines is one of the urgent key problems to be solved.An effective ultra-high-speed identification scheme of lightning strikes suitable for the VSC-based DC grid is proposed in this paper.First,an 1-mode reverse voltage traveling wave(RVTW)is constructed applying the pole-mode transformation theory.Next,fault traveling wave propagation characteristics along the DC transmission line are analyzed in depth utilizing Peterson's law.Then,differences of time-frequency electromagnetic transient characteristics of 1-mode RVTWs between disturbances and faults caused by lightning strikes are distinguished in detail by means of the classical wavelet transformation multi-resolution analysis theory.Finally,extensive simulations are carried out to evaluate the performance of the proposed identification scheme,and by which its excellent rapidity,reliability and robustness are validated.Index Terms-Lightning-strike identification,Multi-resolution analysis,Relay protection,Traveling-wave protection,VsC-based DC grid,Wavelet transformation.展开更多
The effects of low temperature on germination characteristics of rice seeds were studied,using three rice varieties as materials.The results showed that the germination rate,germination energy,germination index,vigor ...The effects of low temperature on germination characteristics of rice seeds were studied,using three rice varieties as materials.The results showed that the germination rate,germination energy,germination index,vigor index,shoot length and root length all reduced with the decrease of temperature.When the treatment temperature was 10 ℃,whether or not cold-resistant varieties,the values of all parameters showed an extremely significant difference from the control's.When the stress temperature was 15 ℃,compared with the normal condition,the parameter values of the non-tolerant variety( Changbai 9) had an extremely significant difference and the germination rate,germination potential,seedling length and root length of two cold-tolerance varieties( Jisheng 202 and Tongjing 9) had little difference from the control.Therefore,the above four indicators at 15 ℃ can be considered as the evaluation indices of cold tolerance at early stage.展开更多
基金supported by the National Natural Science Foundation of China(No.52277075)the State Key Laboratory of Advanced Power Transmission Technology(Grant No.GEIRI-SKL-2020-012).
文摘To ensure their sound and continuous operation to the greatest extent,VSC-based DC girds have extremely stringent requirements for transmission line relay protection.In terms of guaranteeing their reliability,accurate identification of lightning strikes on DC transmission lines is one of the urgent key problems to be solved.An effective ultra-high-speed identification scheme of lightning strikes suitable for the VSC-based DC grid is proposed in this paper.First,an 1-mode reverse voltage traveling wave(RVTW)is constructed applying the pole-mode transformation theory.Next,fault traveling wave propagation characteristics along the DC transmission line are analyzed in depth utilizing Peterson's law.Then,differences of time-frequency electromagnetic transient characteristics of 1-mode RVTWs between disturbances and faults caused by lightning strikes are distinguished in detail by means of the classical wavelet transformation multi-resolution analysis theory.Finally,extensive simulations are carried out to evaluate the performance of the proposed identification scheme,and by which its excellent rapidity,reliability and robustness are validated.Index Terms-Lightning-strike identification,Multi-resolution analysis,Relay protection,Traveling-wave protection,VsC-based DC grid,Wavelet transformation.
基金Supported by the National Key R&D Program of China(2018YFD0300207)the Innovation Project of Jilin Province(CXGC2018ZY014,CXG2017ZD010)
文摘The effects of low temperature on germination characteristics of rice seeds were studied,using three rice varieties as materials.The results showed that the germination rate,germination energy,germination index,vigor index,shoot length and root length all reduced with the decrease of temperature.When the treatment temperature was 10 ℃,whether or not cold-resistant varieties,the values of all parameters showed an extremely significant difference from the control's.When the stress temperature was 15 ℃,compared with the normal condition,the parameter values of the non-tolerant variety( Changbai 9) had an extremely significant difference and the germination rate,germination potential,seedling length and root length of two cold-tolerance varieties( Jisheng 202 and Tongjing 9) had little difference from the control.Therefore,the above four indicators at 15 ℃ can be considered as the evaluation indices of cold tolerance at early stage.
