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首页> 美国政府科技报告 >Resonant overvoltage transients in power systems
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Resonant overvoltage transients in power systems

机译：电力系统中的谐振过电压瞬变

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The thesis defines stationary and transient resonance. Stationary resonance is normally avoided and does not appear at frequencies above a few kilohertz in a power system, because there are no stationary high frequency sources in a power system. Transient resonance appears when a network has two or more natural frequencies close to each other. The thesis presents a simplified method to roughly estimate maximum overvoltages in the case of transient resonance. It is suggested that a network is divided at the crossing between the high impedance and the low impedance parts of the network. Natural frequencies in the low impedance part are found from the calculated driving-point impedance. Similarly the natural frequencies of the high impedance part are found from the calculated driving-point admittance. Calculated Q-factors in the two network parts give an estimate of the relative attenuation. The calculated natural frequencies and the estimated relative attenuation are used to find the worst case overvoltages from characteristics given in the thesis. Normally the actual overvoltages are considerably lower than those found from the worst case characteristics. Two particular power stations have been used as examples of power system networks containing configurations that might cause transient resonance. Transient resonance is measured in both stations, but the overvoltages due to the transient resonance have only caused interruptions in one of these stations. The dominating frequencies measured in the investigated networks were around 20 kHz and 50 kHz respectively. The simulation part of the thesis stresses the need for an accurate transformer model at high frequencies. It is shown that using a transformer model where the frequency dependency of the parameters is not properly taken into account, may lead to completely erroneous results. 102 refs., 169 figs., 10 tabs.

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