Abstract
To analyze the distribution characteristics of voltage and current along half-wavelength transmission lines (HWTLs) in the cases with or without short circuit in the steady state, the method based on the frequency-length factor (FLF) for lossy lines is proposed. Firstly, according to the pole condition of the FLF, the distribution characteristics of power-frequency waves along HWTLs are analyzed. Then, the comprehensive effects of the system parameters and fault resistance are explored, revealing the mechanism of the power-frequency resonance caused by nonmetallic short circuit. Meanwhile, unbalanced short-circuit fault is studied by exploiting additional impedance. The results show that the distribution of the maximum value of power-frequency resonance voltage is related to the system parameters but not to the fault impedance. When a HWTL is short circuited at 2640 km∼2930 km, the resonance voltage can reach to 21 p.u. In relation to symmetrical short circuit, the resonance voltage appears at 1469 km from the short-circuit point, while the position moves towards the short-circuit point with the increase of additional impedance in asymmetrical short-circuit conditions. Additionally, the model theoretically proves that the power-frequency overvoltage induced by short circuit does not appear on a line whose length is less than 1469 km. Finally, cases are studied on PSCAD to verify the accuracy of the model.
Highlights
Half-wavelength power transmission refers to the longdistance three-phase AC transmission technology. e electrical distance of a half-wave length transmission line (HWTLs) is close to half of the power-frequency wavelength (3000 km for 50 Hz systems and 2600 km for 60 Hz systems) [1,2,3,4]
Compared with HVDC lines [5,6,7] or highly compensated AC lines [8], half-wavelength power transmission technology has an advantage with no requirement of compensation, which may be the most economical solution for ultra-long distance power transmission [9,10,11]
A point-to-point power system with a half-wavelength transmission lines (HWTLs) is built in PSCAD, as shown in Figure 1, where the traveling wave Bergeron model of the transmission line is chosen. is model is based on the distributed LC parameters and lumped resistance
Summary
Half-wavelength power transmission refers to the longdistance three-phase AC transmission technology. e electrical distance of a half-wave length transmission line (HWTLs) is close to half of the power-frequency wavelength (3000 km for 50 Hz systems and 2600 km for 60 Hz systems) [1,2,3,4]. Some investigations have been carried out for the distribution of the powerfrequency voltage and current on HWTLs after short circuit Most of these analyses either rely on simulation or neglect line loss, making them unable to give a deep insight into the mechanism [24]. Based on the pole distribution condition of the FLF, the distribution characteristics of steady-state power-frequency voltage and current on HWTLs are firstly analyzed.
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