Abstract
Half-wavelength AC Transmission (HWACT) can improve capability of AC transmission significantly. According to the basic principle of HWACT, the electromagnetic transient model of HWACT is built to analyze the fault transient process of transmission line. Based on fault characteristics of HWACT, the adaptability of traditional protections for transmission lines is analyzed briefly, such as current differential protection, distance protection and over current protection. In order to solve the problems of conventional protection caused by HWACT, a novel integrated protection based on multi-frequency domain information is proposed in this paper, which uses both the power frequency information and transient information. The integrated protection based on multi-frequency domain information takes advantages of power frequency and transient protections, which can not only improve the performance of traditional protection of AC transmission line but also realize fast fault judgment by transient travelling wave protection.
Highlights
In order to support UHV long-distance transmission, the Half-wavelength AC Transmission (HWACT) is presented to improve capability of AC transmission, whose electric transmission distance is close to a half of the power frequency wavelength
Principle of integrated protection based on multi-frequency domain information Adaptability analysis of conventional protection According to characteristic of half-wavelength AC transmission, the conventional protection principle line is not suitable to the half-wavelength AC transmission line anymore
The reasons are shown as follow, 1) Mis-operation caused by fault at the middle of line According to the analysis of the short circuit characteristics above, the conventional protection principles, including current differential protection, distance protection, over current protection and under voltage protection, have a large range of dead zone at the middle of the half-wavelength transmission line
Summary
In order to support UHV long-distance transmission, the Half-wavelength AC Transmission (HWACT) is presented to improve capability of AC transmission, whose electric transmission distance is close to a half of the power frequency wavelength. It is a three-phase AC transmission technology used for extremely long distance, such as three thousand kilometers at 50Hz or two kilometers and five hundred kilometers at 60Hz. In a vast country, HWACT technology is very attractive because it’s a way of long distance, large capacity transmission. Paper [8] analyzes the applicability of current differential protection and distance protection, and proposes compensation algorithms of differential current calculation and interphase impedance calculation, but don’t involve ground impedance calculation
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