In order to meet the growth of China's electricity load, improve the power grid structure, and implement the “West-to-East Electricity Transmission, North-South mutual supply, and nationwide networking†strategy, the development of UHV power grids is imperative. Because UHV DC transmission has the advantages of low cost and low power consumption, it has unparalleled advantages in long-distance, large-capacity power transmission and non-synchronous interconnection of large-scale power grids, and has been greatly developed in recent years.
The electromagnetic environment (such as audible noise, radio interference and synthetic electric field) caused by the halo after UHV DC lines not only restricts the selection of the conductors of the transmission line and the design of the structural parameters, but also often brings about environmental problems. With the improvement of transmission line environmental protection, energy saving and consumption reduction, the measurement and analysis of corona effects such as audible noise, radio interference, and corona loss alone cannot be used to study the electromagnetic environment of transmission lines. The corona discharge from the source of the line-wide frequency corona current and its correlation with the corona effect was investigated, and the corona discharge of the line was further studied.
The traditional corona current measurement system has a low measurement bandwidth (usually below 2 MHz), and the measurement performance is far from meeting the research requirements for the audible noise, radio interference, and corona loss of UHVDC transmission lines with gradually increasing voltage levels. Therefore, it is necessary to The corona currents of UHVDC transmission lines are measured in the wide frequency domain and the wideband characteristics of the corona currents are studied to provide technical support for the fine control of the electromagnetic environment of UHV DC lines in China.
The engineering design of the UHVDC line and the mechanism research of the corona characteristics of the conductors all need to test and study the high frequency characteristics of the line corona current, and the development of the wide-band corona current sampling sensor has become a bottleneck restricting corona current related research. . In order to measure the high-frequency characteristics of the corona current during the corona discharge of an UHV DC line, this invention proposes a wide-frequency-domain corona current sampling resistance sensor. Through a series of technical improvement measures, the measurement bandwidth in an UHV environment is realized. Up to 30MHz corona current sampling sensor. The core inventions are:
Using a structure in which splitting resistors are uniformly arranged on the outside of the insulating tube effectively reduces the electric field strength of the surface of the sampled resistor and ensures that it is free of corona discharge in an ultra-high voltage environment.
The sampling sensor used in the invention comprises a group of more than one splitting resistor bundles. The splitting resistor bundle consists of a plurality of splitting resistors that are evenly distributed on the outside of the insulating tube in parallel with each other. Because the splitting resistor beam is adopted in the present invention, and a pressure equalizing ring is disposed at both ends thereof, the field strength of the sampling sensor surface is greatly reduced, and the surface of the sensor does not occur after being serially connected to the UHV line. Corona phenomenon.
By rationally configuring the electrical parameters of the splitting resistor beam and the shield ring, and reducing the ratio of the high frequency resistance and the capacitive reactance, the measurement bandwidth is greatly improved. In order to reduce the surface electric field strength of the sensor end and avoid corona discharge, metal shield rings should be installed at both ends of the split resistor bundle, and the split resistor bundle is connected with the shield rings at both ends. However, after the shield ring is installed, the distributed capacitance of the sensor is increased, which may cause the frequency response of the sensor to be deteriorated. Therefore, the electrical parameters of the split resistance and the shield ring need to be reasonably configured so as to reduce the ratio of the high-frequency resistor and the capacitive reactance and improve the signal. Measure bandwidth.
Multiple series splitting resistors are connected in series to enable flexible range switching and more accurate measurement.
According to the different state of the wire corona, the corona current on the wire changes greatly. When studying the corona characteristics of the wire, it is usually required to test the corona current of microamps to tens of milliamps. Since the invention adopts a plurality of splitting resistor bundles connected in series, a plurality of measurement ranges can be provided, and the control end can be switched flexibly through a program to measure the corona currents of different amplitude ranges, thereby making the measurement result more accurate. accurate.
The invention is able to increase the measurement bandwidth of the corona current sensor from 2 MHz to 30 MHz in an UHV environment. The core of the invention is the adoption of a splitting resistor beam structure and the collocation of metal shielding rings on both sides, so that the inventive sensor can The measurement bandwidth is greatly increased, and the sensor element is free from corona discharge in the UHV environment. The invention can be widely applied to ±1200kV UHV DC environment to realize accurate measurement of corona current in the wide frequency domain of UHV transmission lines.
This technology has been checked by the State Grid Corporation of Information and Communication, and is certified by the China Institute of Electrical Engineering. Experts agree that the project has reached the international advanced level in corona current sensing in the UHF DC wide-band area.
A corona current sampling sensor with a measuring bandwidth of up to 30 MHz is realized, which fills the gap of corona current measurement in the wide frequency domain of UHV DC lines at home and abroad, broadens the research scope of frequency in corona discharge and its effect research, and promotes deeper levels in this field. Research has improved China’s right to speak in the international arena.
The research results of the electromagnetic environment have been applied to the optimization design of the pole spacing of ± 800kV DC lines in Xizhe and Hajung, reducing the pole spacing by 2m, thereby saving a large amount of corridor resources, reducing the large number of housing demolition, and protecting the environment and social harmony. It is of great significance. The corona loss research results provided an important technical support for the wire selection of the ±800kV DC line at Hajung. The original planned 6×900mm2 wire was changed to 6×1000mm2 wire, and the average corona loss was reduced by nearly 1kW/km. Saving nearly 10 million yuan each year is of great significance for energy conservation and emission reduction.
The project was mainly completed by China Electric Power Research Institute and Beijing University of Aeronautics and Astronautics. The team began to study the wide-band corona current measurement technology for UHVDC power transmission lines in 2009. The sensor has been successfully developed for nearly three years and is equipped on the test line and corona cage of the UHV National Engineering Laboratory. In the field of research, there are currently nearly 20 authorized patents, more than 20 papers published, and successively won the China Electrotechnical Invention Award, the State Grid Corporation of Science and Technology Progress Award, and the Beijing Science and Technology Progress Award.
Team leader Lu Jialu, Ph.D., registered environmental engineer. He is currently a professor-level senior engineer of the China Electric Power Research Institute, a deputy director of the Institute of High Voltage, and a leader in the scientific and technological research team of the "Electromagnetic Environmental Theory and Measurement Technology for AC and DC Power Transmission Lines" of the State Grid Corporation of China. He is also the Secretary General of the Electromagnetic Interference Committee of the Chinese Society for Electrical Engineering. Member of the Expert Team of the Certified Environmental Engineer Registered Engineers Management Committee of the National Survey and Design Registered Engineers, Member of the Nuclear Safety and Environmental Experts Committee of the National Environmental Protection Agency (National Nuclear Safety Administration), and the Standardization Technical Working Group on Assessment Methods in the Electric, Magnetic, and Electromagnetic Fields in China Member of the Design Group of the Expert Committee of the UHV Test Demonstration Project of the State Grid Corporation of China.
Completed more than 80 national, ministerial and other scientific research projects; won 1 first prize for the China Standard Innovation Contribution Award, 17 provincial and ministerial-level scientific and technological progress awards, and 9 items of the State Grid Corporation of Science and Technology Progress Award. He has published more than 90 papers in domestic and foreign academic journals and edited 19 books. Mainly engaged in the electromagnetic environment and electromagnetic compatibility of power systems. (Liu Yuanqing)
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