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Modeling of transient processes at ground faults in the electrical network with a high content of harmonics

机译：具有高谐波含量的电网接地故障的瞬态过程建模

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The paper presents analytical investigations on determination of influence of higher harmonics existing in a ground fault current on the characteristics of transient processes at arcing ground faults. As initial data, results of real oscillography of ground fault currents in the operational 6 kV distribution network are used. It is shown that there are harmonics of high amplitudes in a ground fault current which are 2.6 times greater than a residual 50 Hz reactive current at a single-phase fault location. Calculations using the detailed mathematical model of the 6 kV network confirm the fact that negative influence of arcing overvoltages on equipment insulation increases due to the high content of harmonics in a fault current which are not compensated by Petersen coils and worsen conditions for successful arc quenching. It is noted that a ground fault current may cross zero many times without current extinction due to harmonic distortion. Due to high-frequency overvoltages, probability for restrikes increases. It results in expanding of a fault area in cable insulation and reducing of time for transition of single phase-to-ground fault into stable arcing with possible breakdowns of phase-to-phase insulation. To prove these statements, resistances in a fault place taking into account harmonic distortions of an arc current are calculated.
机译：本文对确定接地故障电流中存在的高次谐波对电弧接地故障瞬变过程特征的影响进行了分析研究。作为初始数据，使用了实际的6 kV配电网络中接地故障电流的示波器记录结果。结果表明，接地故障电流中存在高幅度的谐波，该谐波比单相故障位置处的残留50 Hz无功电流高2.6倍。使用6 kV网络的详细数学模型进行的计算证实了以下事实：由于故障电流中的谐波含量很高，电弧过电压对设备绝缘的负面影响会增加，而该故障电流无法通过Petersen线圈进行补偿，并且无法成功进行灭弧。注意，由于谐波失真，接地故障电流可能会多次过零而电流不会消失。由于高频过电压，发生再碰的可能性增加。这会导致电缆绝缘层中的故障区域扩大，并减少将单相接地故障转换为稳定电弧的时间，并可能导致相间绝缘故障。为了证明这些说法，计算了考虑电弧电流的谐波畸变的故障位置的电阻。

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