Compared with the conventionally used i=iosinωt alternating current, using asymmetric triangular and pulse wave as input signals can greatly enhance the incision's sensitivity of 'dE/dt-E'oscillogram.
The damage of two typical metal materials, Al alloy 3003 and steel alloy Q235 B, subjected to four representative lightning current components are investigated by laboratory and analytical studies to provide fundament...The damage of two typical metal materials, Al alloy 3003 and steel alloy Q235 B, subjected to four representative lightning current components are investigated by laboratory and analytical studies to provide fundamental data for lightning protection. The four lightning components simulating the natural lightning consist of the first return stroke, the continuing current of interval stroke, the long continuing current, and the subsequent stroke, with amplitudes 200 k A, 8 k A,400 A, and 100 k A, respectively. The damage depth and area suffered from different lightning components are measured by the ultrasonic scanning system. And the temperature rise is measured by the thermal imaging camera. The results show that, for both Al 3003 and steel Q235 B, the first return stroke component results in the largest damage area with damage depth0.02 mm uttermost. The long continuing current component leads to the deepest damage depth of 3.3 mm for Al 3003 and much higher temperature rise than other components. The correlation analysis between damage results and lightning parameters indicates that the damage depth has a positive correlation with charge transfer. The damage area is mainly determined by the current amplitude and the temperature rise increases linearly with the charge transfer larger.展开更多
Transmission power lines are a common source of extremely low frequency(ELF) magnetic fields which are usually analyzed as serial lines in one direction.Overhead vertical-type double-circuit power lines,which are gene...Transmission power lines are a common source of extremely low frequency(ELF) magnetic fields which are usually analyzed as serial lines in one direction.Overhead vertical-type double-circuit power lines,which are generally used in Japan,sometimes carry different current for each circuit and change direction.In this paper,we focused on both the angle of direction change and the current balance in order to clarify the characteristics of distribution of magnetic fields at a height of 1 m.The magnetic field distributions were analyzed considering both the angle of power lines changing direction and the current balance of each circuit.The total magnetic field under overhead vertical-type double-circuit power lines with same current was generally reduced in comparison with that under a single-circuit power line due to phase difference.The total magnetic fields around the turning point where the change of transmission lines direction increased because each circuit came closer in that area.The component of B_z effect on total magnetic field was greatest around the maximum of total magnetic fields nearby the turning point.展开更多
文摘Compared with the conventionally used i=iosinωt alternating current, using asymmetric triangular and pulse wave as input signals can greatly enhance the incision's sensitivity of 'dE/dt-E'oscillogram.
基金supported by a grant from National Natural Science Foundation of China(No.51577117)
文摘The damage of two typical metal materials, Al alloy 3003 and steel alloy Q235 B, subjected to four representative lightning current components are investigated by laboratory and analytical studies to provide fundamental data for lightning protection. The four lightning components simulating the natural lightning consist of the first return stroke, the continuing current of interval stroke, the long continuing current, and the subsequent stroke, with amplitudes 200 k A, 8 k A,400 A, and 100 k A, respectively. The damage depth and area suffered from different lightning components are measured by the ultrasonic scanning system. And the temperature rise is measured by the thermal imaging camera. The results show that, for both Al 3003 and steel Q235 B, the first return stroke component results in the largest damage area with damage depth0.02 mm uttermost. The long continuing current component leads to the deepest damage depth of 3.3 mm for Al 3003 and much higher temperature rise than other components. The correlation analysis between damage results and lightning parameters indicates that the damage depth has a positive correlation with charge transfer. The damage area is mainly determined by the current amplitude and the temperature rise increases linearly with the charge transfer larger.
文摘Transmission power lines are a common source of extremely low frequency(ELF) magnetic fields which are usually analyzed as serial lines in one direction.Overhead vertical-type double-circuit power lines,which are generally used in Japan,sometimes carry different current for each circuit and change direction.In this paper,we focused on both the angle of direction change and the current balance in order to clarify the characteristics of distribution of magnetic fields at a height of 1 m.The magnetic field distributions were analyzed considering both the angle of power lines changing direction and the current balance of each circuit.The total magnetic field under overhead vertical-type double-circuit power lines with same current was generally reduced in comparison with that under a single-circuit power line due to phase difference.The total magnetic fields around the turning point where the change of transmission lines direction increased because each circuit came closer in that area.The component of B_z effect on total magnetic field was greatest around the maximum of total magnetic fields nearby the turning point.
