Guide: At night, passing through the high-voltage transmission line corridor, it is often found that the wire is surrounded by a light blue light, accompanied by a "sweet" sound, which is caused by corona discharge.
Passing through the corridors of high-voltage transmission lines at night, it is often found that the wires are surrounded by a light blue light, accompanied by a "sizzling" sound, which is caused by corona discharge. Corona discharge phenomenon will adversely affect the operation of the power grid and people's daily life. For example, corona discharge will generate high-frequency pulse current, which contains various high-order harmonics, which will cause radio interference; corona discharge will cause a The series of chemical reactions produce strong corrosive substances such as ozone, nitrogen monoxide and nitrogen dioxide, which affect the transmission line; corona discharge consumes energy, causing unnecessary energy loss in the power system; corona discharge emits human ear Audible noise has a psychological and physiological impact on people. There are many factors affecting the corona discharge of high-voltage transmission lines, such as the field strength of the wire surface, the surface condition of the wire, the meteorological conditions of the line passing through the area, the altitude, etc., and the field strength of the wire surface is related to the operating voltage, the wire spacing, the height of the wire to the ground, The wire radius and other parameters are related.
In the design stage, the transmission line always hopes to avoid corona discharge by optimizing the wire layout and reasonably selecting the wire size. However, due to the high voltage level of the transmission line, especially the UHV, in order to completely eliminate the corona discharge, the radius of the transmission line will be large, and the distance to the ground is too high, so that the economic feasibility of the transmission line conductor selection and layout scheme is extremely low. Therefore, the corona discharge intensity can be minimized only on the basis of economic feasibility.
In the design of transmission lines, the electromagnetic environment assessment of the pre-selection scheme of the conductors must first be carried out. Whether the existing electromagnetic environment assessment methods in the world are fully applicable to the UHV transmission lines is still uncertain. In order to obtain an electromagnetic environment assessment method that is completely applicable to UHV, the mechanism of wire corona discharge should be first clarified, and the description method of the microscopic physical process of wire corona discharge is obtained. On this basis, we find a more accurate electromagnetic environment assessment method, provide guidance for the selection and layout of UHV transmission line conductors, and achieve the goal of UHV transmission resource conservation and environmental friendliness.
Study the microscopic physical processes and mechanisms of corona dischargeCorona discharge is an old problem. Scholars have carried out corresponding research very early on, and have been able to qualitatively describe some basic processes of corona discharge. The wire is a large curvature electrode relative to the earth. When the transmission line is running, if the electric field strength near the wire is too large, the free electrons in the air (the free electrons existing in the air before corona discharge) will collide and ionize under the action of field strength. (such as electron impact ionization reaction, adhesion reaction, neutralization reaction of positive and negative ions, etc.), the wire will produce corona discharge. At this time, the corona discharge has a certain randomness. If the electric field strength near the wire continues to increase, the vicinity of the wire can spontaneously generate seed electrons under the action of field ionization, wire surface impact ionization, etc., and when the air self-sustaining discharge condition is reached, the wire of the transmission line will generate continuous corona discharge.
The physical process of corona discharge is quite complicated. It is still impossible to determine the development and change law of microscopic particles in corona discharge process through effective research methods, and it is impossible to deeply understand various physical and chemical reactions occurring during corona discharge. At the same time, corona discharge involves a large number of microscopic particles. Due to the limitations of experimental test conditions, it is impossible to carry out experimental measurements of corona discharge characteristic parameters (such as space charge), and it is impossible to carry out research on quantitative analysis of corona discharge process. Therefore, it is difficult for researchers to obtain an effective method for accurately describing the corona discharge process of transmission lines.
To study the microphysical process and discharge mechanism of corona discharge, we should first solve the problems that cannot quantitatively describe the microphysical process of corona discharge and the limitations of experimental test conditions. At present, there is no test method for space charge in gas in the world, and there is no successful case for measuring space charge distribution. Through five years of trials and explorations, the research team has developed a measurement method of acoustic pulse method, which uses ultrasonic transducer to generate ultrasonic pulse to modulate space charge, and establishes a signal reduction algorithm to restore the electric field signal generated by modulation. . According to the principle of the test, a set of experimental equipment was set up in the laboratory according to the ratio of 1:1. Finally, the space charge distribution was measured.
The research group considered the influence of photoionization and secondary electron collapse emission in the corona discharge control equation, and improved the control equation describing the microphysical process of corona discharge, making the control equation of corona discharge more appropriate. By analyzing the equation, the corona discharge process, how the electrons proliferate, how the various particles diffuse, and the trends of various microscopic particles in the corona discharge process can be clearly obtained. Therefore, a clearer understanding and clear definition of the initial, development and value-added process of corona has laid a theoretical foundation for further research on the electromagnetic environment characteristics of transmission lines.
UHV corona discharge and evaluation of electromagnetic environment characteristicsIn the design stage of power transmission and transformation engineering, various types of conductor selection can be analyzed and calculated by modeling, and the influence factors of corona discharge are predicted. Finally, the optimal design scheme is selected to meet the requirements of electromagnetic environment limits.
The traditional method mainly summarizes empirical formulas based on a series of experiments, such as the Peek formula for calculating the field strength of the halo, the Pidson formula for calculating the corona loss, and the empirical calculation. The empirical formula is simple and easy to use, but its applicability is very limited, and the influence of environmental factors on corona discharge is not considered. In addition, what are the similarities and differences between UHV corona discharge and traditional ultra-high voltage? Is the previous calculation method applicable in UHV? These problems cannot be determined based on past research results. Faced with these problems, the research group based on the above research on corona discharge characteristics, in-depth study of the macroscopic equivalent physical model of corona discharge on transmission lines, and proposed an electromagnetic environment assessment method for corona discharge of transmission lines. On the basis of past research, the researchers abandoned many hypotheses, established a dimensionless model, obtained corona initiation and self-sustaining criteria for UHV transmission lines, and defined the boundary conditions for corona discharge calculations for electromagnetic environment assessment. And related calculations laid the foundation.
The corridor environment of UHV DC transmission lines in China is complex, and there are buildings, trees and surface changes in the vicinity. At present, two-dimensional ion current and synthetic electric field evaluation methods are still used internationally. The research group improved the calculation method of two-dimensional ion flow field, applied the boundary electric field constraint equation method to the calculation of electric field strength on the surface of the sub-wire, accelerated the calculation speed, and accelerated the convergence of the algorithm by using the potential ordering method. Based on this, the three-dimensional development was obtained. The calculation method of the ion flow field.
The research team also studied and obtained a new calculation method of corona loss from the mechanism of corona loss, and carried out on-site measurement experiments of corona loss under different environmental conditions in Wuhan and Beijing UHV bases. Compared with the traditional calculation method, the new calculation method considers the influence of environmental factors on the corona loss, which makes the calculation result more accurate and agrees well with the field data.
Starting from the mechanism of corona discharge, the calculation of the ion flow field, and the solution of the final corona loss, the research team carried out systematic and meticulous research and proposed an evaluation method for the electromagnetic environment of UHV transmission lines, which is very good. The ground is applied to the on-site evaluation of the UHV electromagnetic environment. The results have been applied in Ximeng-Shandong, Huainan-Nanjing-Shanghai, Yuheng-Weifang 1000 kV UHV exchange, Shanghai Temple-Shandong, Ximeng-Taizhou ±800 kV UHV DC engineering design.
Function description
The socket is ordinary converter,with two output 5V2A power USB power supply at the same time,can be very convenient in use electrical appliances and recharge the equipment at the same time,such as digital products like Iphone Ipad,MP3,MP4 etc.The charge apply to full range of international AC output,no-load power consumption less than 0.3W,with short circuit,overload,over-voltage protection,can be convenient for your life and save more energy
Timer Control Time Adgustment
1.Press the power switch 1 time,the 1HOUR LED will light on.The Timer into ON mode,USB and control socket output ON .
2.Continuously press the power switch the LED light on,the Countdown mode and LED light on will cycle change from 1HR,2HR,4HR,6HR,8HR,10HR.
3.Choose you need countdown time mode,the mode LED will lighto on,start countdown until countdown time finish,the control output and USB change to OFF
4.Then the countdown is start,The Time indicate LED will from high to low auto change until Countdown finish off.
Failure analysis:
1.check whether the power supply connection is good
2.check whether the USB cable is loosen
Warning Note:
1.Use indoor and dry location ONLY
2.The load max does not exceed 15A 3600W
3.This product does not convert voltage please do not miss use DO NOT exceed the maximum loading of 3600 Watts 15A
4.Always have earth connection for safety reason
5.If in doubt please consult with a qualified electrician
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