In order to improve the reliability of fault identification of the double-circuit transmission lines on the same tower, a new algorithm for fast protection of double-circuit transmission lines on the same tower based ...In order to improve the reliability of fault identification of the double-circuit transmission lines on the same tower, a new algorithm for fast protection of double-circuit transmission lines on the same tower based on the reactive powers of traveling wave is proposed. With the implementation of S-transform, the initial traveling wave reactive powers are calculated and the change characteristics of reactive power under different fault conditions are studied. The protection criterion is constructed by analyzing the ratio of the reactive powers of the same end on double-circuit transmission lines and the ratio of the reactive powers at both ends on the same line. According to the ratio of reactive power on the same side of the line and both ends of the same line, it is possible to identify whether the faults of the double-circuit line of the same tower occurred in or out of the protection zone. A large number of simulation results show that the protection performance is sensitive and reliable, and quick to respond. The criterion is simple and is basically not affected by fault initial angles, fault types, and transitional resistances.展开更多
In this paper,wave and vibratory power transmission in a finite L-shaped Mindlin plate with two simply supported opposite edges are investigated using the wave approach.The dynamic responses,active and reactive power ...In this paper,wave and vibratory power transmission in a finite L-shaped Mindlin plate with two simply supported opposite edges are investigated using the wave approach.The dynamic responses,active and reactive power flow in the finite plate are calculated by the Mindlin plate theory （MPT） and classic plate theory （CPT）.To satisfy the boundary conditions and continuous conditions at the coupled junction of the finite L-shaped plate,the near-field and far-field waves are entirely contained in the wave approach.The in-plane longitudinal and shear waves are also considered.The results indicate that the vibratory power flow based on the MPT is different from that based on the CPT not only at high frequencies but also at low and medium frequencies.The influence of the plate thickness on the vibrational power flow is investigated.From the results it is seen that the shear and rotary inertia correction of the MPT can influence the active and reactive power at the junction of the L-shaped plate not only at high frequencies but also at low and medium frequencies.Furthermore,the effects of structural damping on the active and reactive power flow at the junction are also analyzed.展开更多
This paper analyzes the physical meaning of the active and reactive power flow in the finite L-shaped beams and studies the active vibration control of the structures based on the active and reactive power flow.The tr...This paper analyzes the physical meaning of the active and reactive power flow in the finite L-shaped beams and studies the active vibration control of the structures based on the active and reactive power flow.The traveling wave approach is used to calculate the structural dynamic responses.Because the error of control force is inevitable in practical applications,the effects of the error of control force on the control results are studied.The study indicates that the error of control force has pronounced influence on the control results of the acceleration and reactive power flow.It is obvious that the reactive power flow can represent the vibration strength component of the complex intensity,and the active power flow strongly depends on the structural damping of the finite beams.展开更多
大部分工矿企业的用电情况复杂,大量非线性负荷使供电系统中高次谐波含量增加,引起电网电压畸变,常规无功补偿设备无法有效应对。针对上述现象,本文提出了一种由三电平拓扑电路组成的有源电力滤波器(APF)模块设备,安装在变压器二次侧0.4...大部分工矿企业的用电情况复杂,大量非线性负荷使供电系统中高次谐波含量增加,引起电网电压畸变,常规无功补偿设备无法有效应对。针对上述现象,本文提出了一种由三电平拓扑电路组成的有源电力滤波器(APF)模块设备,安装在变压器二次侧0.4 k V母线上,对电源系统进行谐波治理和无功补偿。该模块运行速度快、功率损耗低、体积小、重量轻,较适宜于现场的安装改造。工程实践证明该模块能够有效解决供电系统谐波污染和无功补偿问题。展开更多
文摘In order to improve the reliability of fault identification of the double-circuit transmission lines on the same tower, a new algorithm for fast protection of double-circuit transmission lines on the same tower based on the reactive powers of traveling wave is proposed. With the implementation of S-transform, the initial traveling wave reactive powers are calculated and the change characteristics of reactive power under different fault conditions are studied. The protection criterion is constructed by analyzing the ratio of the reactive powers of the same end on double-circuit transmission lines and the ratio of the reactive powers at both ends on the same line. According to the ratio of reactive power on the same side of the line and both ends of the same line, it is possible to identify whether the faults of the double-circuit line of the same tower occurred in or out of the protection zone. A large number of simulation results show that the protection performance is sensitive and reliable, and quick to respond. The criterion is simple and is basically not affected by fault initial angles, fault types, and transitional resistances.
基金supported by the National Basic Research Programof China (2011CB711102)the National Natural Science Foundation of China (10672017,11002045)
文摘In this paper,wave and vibratory power transmission in a finite L-shaped Mindlin plate with two simply supported opposite edges are investigated using the wave approach.The dynamic responses,active and reactive power flow in the finite plate are calculated by the Mindlin plate theory （MPT） and classic plate theory （CPT）.To satisfy the boundary conditions and continuous conditions at the coupled junction of the finite L-shaped plate,the near-field and far-field waves are entirely contained in the wave approach.The in-plane longitudinal and shear waves are also considered.The results indicate that the vibratory power flow based on the MPT is different from that based on the CPT not only at high frequencies but also at low and medium frequencies.The influence of the plate thickness on the vibrational power flow is investigated.From the results it is seen that the shear and rotary inertia correction of the MPT can influence the active and reactive power at the junction of the L-shaped plate not only at high frequencies but also at low and medium frequencies.Furthermore,the effects of structural damping on the active and reactive power flow at the junction are also analyzed.
基金supported by the National Natural Science Foundation of China (Grant Nos.10672017, 10632020 and 11002045)
文摘This paper analyzes the physical meaning of the active and reactive power flow in the finite L-shaped beams and studies the active vibration control of the structures based on the active and reactive power flow.The traveling wave approach is used to calculate the structural dynamic responses.Because the error of control force is inevitable in practical applications,the effects of the error of control force on the control results are studied.The study indicates that the error of control force has pronounced influence on the control results of the acceleration and reactive power flow.It is obvious that the reactive power flow can represent the vibration strength component of the complex intensity,and the active power flow strongly depends on the structural damping of the finite beams.
文摘大部分工矿企业的用电情况复杂,大量非线性负荷使供电系统中高次谐波含量增加,引起电网电压畸变,常规无功补偿设备无法有效应对。针对上述现象,本文提出了一种由三电平拓扑电路组成的有源电力滤波器(APF)模块设备,安装在变压器二次侧0.4 k V母线上,对电源系统进行谐波治理和无功补偿。该模块运行速度快、功率损耗低、体积小、重量轻,较适宜于现场的安装改造。工程实践证明该模块能够有效解决供电系统谐波污染和无功补偿问题。
