【作者】 张利；

【导师】 杨以涵；

【作者基本信息】 华北电力大学（北京） ， 电力系统及其自动化， 2009， 博士

【摘要】 我国中压电网大多采用中性点非有效接地方式(小电流接地方式),这种接地方式的系统在发生单相接地故障时,接地电流很小,系统运行可靠性高。但由于接地电流微弱,加上中压电网接线复杂,分支众多,中性点非有效接地系统的单相接地故障定位成为一个尚未得到很好解决的难题。本文根据配电部门对于定位的需求差异,提出了故障定位的停电方法和带电方法。主要研究内容如下:深入研究交流法,该方法用于停电故障定位。分析线路上分布电感和分布电容对注入信号的影响,建立注入交流信号时线路的集中参数模型,得出定位可靠性和注入信号频率之间的函数关系,选择交流信号频率为60Hz。分析了接地过渡电阻和线路分布电容对定位可靠性的影响。完善停电定位的直流法。该方法可完全克服接地过渡电阻和线路分布电容的影响,可解决长短分支问题。直流信号仅在注入点和接地点之间形成回路,定位可靠性高,可以解决一切单相接地故障的定位问题。采用断面直流检测方式,克服配电变压器三相之间的串通问题。采用无线通信技术,实现了直流信号的检测。提出交直流综合法(停电定位)。该方法将接地过渡电阻与线路长度之积作为判断指标,该指标较大时,线路对交流信号的分流作用强,交流法可靠性低,采用直流法;该指标较小时,大部分交流电流都经故障路径流入故障点,应采用交流法。交直流综合法将交流法的易检测和直流法的准确可靠有效结合,实现了两种方法间的优势互补。提出中性点不接地系统带电定位的零序电流相量比较法。中性点不接地系统发生单相接地故障时,故障路径上零序电流滞后零序电压90°,非故障路径上的零序电流超前零序电压90°。零序电流相量比较法直接利用单相接地故障本身产生的工频信号进行定位,不需要外加信号,对系统运行无任何影响。应用GPS(全球定位系统)进行同步采样,GPRS(通用无线分组业务)无线传输数据,实现了电压电流间相对相位的获取。提出两种零序电流的检测手段:移动式零序电流互感器检测方式和感应磁场的移动式检测。移动式零序电流互感器检测方式采用高精度钳形CT,分别套接于三相线路上,用三相电流离散值合成故障线路上的零序电流,测量不受周围环境影响,准确度高。感应磁场的移动式检测采用双端相位比较的方式代替单一点的直接模值测量,避免了单一点测量易受距离、周围影响的不足,增强测量结果的可靠性。提出谐振接地系统带电定位的零序电流突变量法。该方法通过改变消弧线圈电抗值,从而引起线路上各点的零序电流模值发生变化,根据零序电流模值的变化特性来判断故障位置。通过将折算到同一电压水平的零序电流模值相减,克服了接地电阻的影响。更多还原

【Abstract】 The neutral ineffectively grounded systems are adopted mostly in MV power distribution networks.The advantages of this kind of system are highly reliability and small current when single-phase-to-earth fault happened.Fault location of single-phase-to-earth in neutral ineffectively grounded system has not been well resovled due to its little current and complicated connection of the branches.The thesis put forword online and offiine methods to realize the fault location based on the demand of the distribution department.The principle contents are as follows:Off-line fault location method of AC is proposed.By analyzing the effects of the inductance and distributed capacitance of the line to the AC signal injected to the line, the paper set up the lumped parameter of the line model,and draw the function between the reliability and the frequency of the AC signal,then choose 60Hz as the frequency of the signal.At last,the paper analyzes the influence of the resistor and the distributed capacitance to the reliability of this method.In order to overcome the influence of the resistor and distributed capacitance,A method of DC is put forward.The signal of DC can only flew from the injection point and the earthing point,so the method can settle all the faults of the single-phase-to earth,such as large resistor,fault line with long and short branches,and et al.The way of "section current" is adopted to settle the problem of the DC signal flew within three-phase line through the transformer.The technology of communication wireless is used to solve the issue of the detection of DC signal.The method of DC-AC is proposed in the paper.Where the product of the resistor and the length of the line is used as the target to decide which method(AC or DC) is suited under different fault location.When the target is large,the capacitance of the line will take a large percent of the AC current injected,then the reliability of method of AC is low,the method of DC should be taken.When the target is small,most of the AC current flew into the earthing point,so the method of AC is suitable.The method of DC-AC combine the accuracy of the method DC and the easily detect of the method AC together,can achieve more quickly and more accurate fault location.The method of phasor comparison of zero-sequence current is proposed to locate the fault point online for neutral non-connected grounded system.When single-phase-to-ground fault is happened,the zero-sequence current lags the zero-sequence voltage 90°on the fault route and leads the zero-sequence voltage 90°on non-fault route.This method locates the fault by the signal caused by the fault itself without no external signal,then cause no effect to the system running.The system of GPS and the technology of GPRS are used to acquire the phase between the voltage and current.Two detection means are introduced here to measure the zero-sequence current, which is mobile zero-sequence CT and mobile induct magnetic filed detection.Mobile zero-sequence CT use three precise CT of clamp mode,which socket separately on the three-phase line,and synthesis the zero-sequence current of the fault line by the discrete value of the three-phase current.This means suffer little from the environment and achieve high accuracy.Mobile induct magnetic field detection realize the current detection by compare the phase of dual sides instead of detect the amplitude of a single point,and enhance the reliability of the measure.The method of zero-sequence current change is proposed to solve the problem of fault location of resonant grounded system.The zero-sequence current will change when the inductance of arc-suppression coil is changed.The method locate the fault point based on the properties of the change on the fault line.更多还原