10kV架空导线单相触树接地故障检测方法

针对单相触树接地故障(TSF)检出困难的问题,进行了TSF建模和检测方法研究.通过分析导线触树过程中的树木温度变化,构建了基于树木电阻率、高度、半径、电阻率-温度特性等实际物理参数的TSF过渡电阻工频时变模型.利用所建模型,分析得到不同10 kV系统发生TSF时的零序电压、电流随时间的变化规律.基于TSF零序电流缓慢单调上升的特征,提出了监测零序电流超过阈值的持续时间的TSF检测方法,并利用多周期测量数据提高测量可靠性.以数字仿真和10 kV TSF试验对模型和方法进行了验证.验证结果表明,所建模型能够准确地模拟不同尺寸树木TSF的过渡电阻随时间的缓变曲线,所提方法的TSF检测灵敏度可达几十千欧,能够大大提升TSF的检出率.

Detection Method for Tree-contact Single-phase-to-ground Fault of 10 kV Overhead Line

Aiming at the difficulty in detection of tree-contact single-phase-to-ground faults (TSFs), the modeling and detection method for TSFs are studied. By analyzing temperature changes of trees during faults, a time-varying model for transition resistance of TSFs is established based on actual physical parameters of trees, i.e., resistivity, height, radius, and resistivity-temperature characteristics. Using this model, the TSF characteristics of zero-sequence voltage and current variation with time for different 10 kV systems are analyzed and concluded. Based on the characteristic that TSF zero-sequence current rises slowly and monotonously, a TSF detection method is proposed which monitors the time duration of the zero-sequence current exceeding the threshold, and the measurement reliability is improved by using multi-cycle measuring data. The model and the method are verified with digital simulations and 10 kV TSF experiments. The verification results indicate that the model can accurately simulate the slowly time-varying curves of transition resistance for TSFs caused by size difference of trees , and the detection sensitivity of the proposed method can reach tens of kiloohms, which can greatly improve the detection ratio of TSFs.