Abstract
Corona-originated discharge of DC transmission lines is the main reason for the radiated electromagnetic interference (EMI) field in the vicinity of transmission lines. A joint time-frequency analysis technique was proposed to extract the radiated EMI current (excitation current) of DC corona based on corona current statistical measurements. A reduced-scale experimental platform was setup to measure the statistical distributions of current waveform parameters of aluminum conductor steel reinforced. Based on the measured results, the peak value, root-mean-square value and average value with 9 kHz and 200 Hz band-with of 0.5 MHz radiated EMI current were calculated by the technique proposed and validated with conventional excitation function method. Radio interference (RI) was calculated based on the radiated EMI current and a wire-to-plate platform was built for the validity of the RI computation results. The reason for the certain deviation between the computations and measurements was detailed analyzed.
Highlights
The pulse amplitude distribution of corona current for aluminum conductor steel reinforced (ACSR) is close to the lognormal distribution when the positive applied voltage is above the inception level
When the applied voltage is above inception level, the pulse interval time obeys the exponential distribution at low voltage
A joint time-frequency analysis technique for the computation of radiated electromagnetic interference (EMI) current of DC corona discharge, and the radio interference (RI) is calculated based on the computation of the excited current
Summary
With the continuously increasing the voltage level of DC transmission line, the radiated electromagnetic interference (EMI) or radio interference (RI) or radio noise (RN) issue of transmission line is becoming more and more prominent, which has become an important factor in the design of the transmission tower structure and the selection of the conductor.[1,2,3] In addition, the attention of the public to the electromagnetic environment of high voltage direct current (HVDC) or UHVDC system is increasing year by year.[4,5] it is very imperative to study the mechanism of radiated EMI and limit it to a reasonable extent. Due to the space charge in presence of the region in the vicinity of DC lines, these heavy space species, including positive and negative ions and charged aerosols, move slowly along flux (10-4 to 10-3 cm2/N·s) forming the ion flow field They would affect the corona discharge process and corona current magnitude of the conductor, so, the mechanism, computation and analysis of radiated EMI of DC lines is different from that of the AC lines. The 0.5 MHz is recommended as a test intermediate frequency and a narrowband excitation function by CISPR.[18] The 0.5 MHz interference of transmission line is generated by the 0.5MHz component of the high frequency corona current. A finite length wire-to-plate is used to verify the radiated radio interference
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