【作者】 林富洪；

【导师】 王增平；

【作者基本信息】 华北电力大学（北京） ， 电力系统及其自动化， 2010， 硕士

【摘要】 针对现有高压输电线路故障测距方法存在着一些如原理上有伪根存在的可能、两端数据同步匹配问题和测距精度与测距速度之间存在此消彼长的矛盾等不足,文章在引入参考点与故障点相匹配的思想基础上构建了一新的测距函数。利用该测距函数相位特性可实现对N(N≥2)端输电线路和同杆双回线进行故障定位。1、双端线路上该测距函数与双曲正切函数(或双曲正弦函数)具有相同相位特性,利用所选参考点与故障点相匹配时测距函数过零这一特征进行定位。该方法原理上不存在伪根,运算量小,具有良好的快速性。2、该测距函数在T型线路的故障支路和正常支路上分别具有不同相位特性,利用正常支路上所选参考点与故障点相匹配时测距函数过零这一特征进行定位。该方法打破了传统先判断故障支路再故障定位的模式,无需事先判别故障支路即可测距。该方法无测距死区,较好的克服了传统方法在T节点附近有测距死区的不足。该方法不存在伪根,对非线性电阻故障具有良好的适用性。3、鉴于现有多端故障测距方法存在的缺陷,诸如采用未能真实反映实际情况的线路集中参数模型,在T节点附近高阻短路故障时有测距死区,算法过于复杂不易实现,受系统运行方式的影响等,在T节点附近发生高阻短路故障时,无法正确判别故障支路。针对该缺陷,文章提出一种N端输电线路同步故障测距新算法。首先,由离参考端最远的母线推算离参考端最近的T节点的电压、电流,在该T节点和参考端之间利用双端测距算法求出故障距离：基于该故障距离的分布特点将原N端输电线路的故障测距问题转化为一个T型线路的故障测距问题。然后,利用文章提出的T型线路故障测距新算法进行测距。该方法无测距死区,克服了传统方法在T节点附近有测距死区的不足,测距精度受过渡电阻、故障类型和负荷电流的影响很小4、现有同杆双回线非同步故障定位方法存在着需要通过移动数据来同步匹配两侧信息。针对这一不足,文章提出一种基于双曲正切函数相位特性同杆双回线非同步故障定位新原理。根据所取参考点与故障点相匹配时双曲正切函数相位过零这特征进行定位。该方法理论证明了非同步故障时可利用对侧反向正序电流相位来同步校正该侧反向正序电流相位,无需通过数据移动来同步匹配两侧信息。由于只采用双端电流量,在原理上避免了电压互感器传变特性的影响,且理论上证明了该方法测距精度不受电流互感器特性的影响。原理上不存在伪根问题,对非线性电阻故障具有良好的适用性。由于故障点与T接点位置关系未知,所以应用于传统双端线路的分布电容电流补偿方法不能直接应用于T型输电线路的全电流差动保护中,因此,目前所提出的工频稳态量差动保护在原理上仍受分布电容电流的影响,为了避免保护误动,定值要躲开分布电容电流,从而降低了保护的抗过渡电阻能力。针对这一问题,文章提出一种基于分布参数模型的T型输电线路电流差动保护新原理,该方法将原为三端线路电流差动保护问题转化为2个原理相似的双端线路电流差动保护问题,并数学分析了这种转化的正确性。与传统T型线路全电流差动保护相比,新保护判据不受分布电容电流的影响,适用于T型高压输电线路。采用保护安装处零序电流相位来估算故障支路电流相位的估算误差是零序电抗继电器及其改进型阻抗继电器难以直接应用于特高压交流输电线路上的主要因素。针对该问题,经分析得出观测点处的负序电流可以很好地模拟单相接地短路时故障支路负序电流的相位信息。在此基础上,提出一种可适用于特高压交流输电线路的单相接地阻抗继电器。该保护在特高压交流输电线路单相接地时具有较强的抗过渡电阻能力和稳定的保护范围以及较高的动作灵敏性。更多还原

【Abstract】 A new fault location function is generated based on the matching idea of selecting a reference point to match the fault position, which phase characteristics is determinated by the phase characteristics of hyperbolic tangent function or by the phase characteristics of hyperbolic sine function. The accurate fault location for N-terminal (N≥2) transmission lines and parallel transmission lines can be achieved by using the phase characteristics of the function.(1) The function has different phase characteristics between reference point located at the left of fault position and reference point located at the right of fault position, and the phase of the function equals to zero when the reference point matches the fault position. Based on the phase characteristics of the function, a novel fault location algorithm for two terminals transmission lines is proposed. The presented algorithm has less calculation burden, and the accuracy is independent of fault transition impedance and its property, fault type, fault position. The fault location function has no false root in theory.(2) The function has different phase characteristics between the fault branch and the healthy branches, and phase of the function equals to zero when the reference point matches the fault position on the fault section. Based on the phase characteristics of the function, a novel fault location algorithm for three-terminal tranimission lines is proposed. The method breaks the mold of traditional methods that it must identify the fault section before locating the fault. The method can locate the fault without identifying the fault section first. And the method doesn’t have dead zone of fault location, it can accurately locate the fault occurring near the teed node. Therefore, the method perfectly solves the disadvantage of currently used methods that there is a dead zone of fault location near the teed node. Th·e presented algorithm has less calculation burden, and the accuracy is slightly affected by transition resistance and its property, fault types and load current.(3) Due to the defects of existing synchronized phasor measurement (SPM) based fault location methods for multi-terminal transmission lines, such as the adopted lumped parameter models of transmission line cannot reflect correctly actual condition, there is dead zone of fault location while the high resistance fault occurred near the teed node, or the algorithm is too complex to implement, the adopted algorithms are affected by operation modes of power system, etc., the faulty branch cannot be correctly judged when high resistance fault occurred near the teed node. For this reason, a new fault location algorithm for multi-terminal transmission lines using SPM is proposed. Firstly, the voltage and current of the teed node that is the nearest to the reference bus are calculated by the voltage and current data of the bus that is the farthest to the reference bus, and by use of two-terminal fault location algorithm the fault location between the teed node and reference bus is solved; then based on the distribution characteristic of this fault location, the fault location problem of original N-terminal transmission lines is changed into the fault location of a teed transmission line; finally, a new fault location algorithm without dead zone for teed transmission line is given. The given algorithm remedies the defect of traditional fault location methods in which dead zone of fault location exist. The accuracy of the given algorithm is slightly affected by transition resistance, fault types and load current.(4) A new fault location algorithm for parallel transmission lines using two terminals unsynchronized data is proposed based on the phase characteristics of the function. The synchronization is achieved by using one terminal current’s phase to adjust the other terminal current’s phase in the differential component net. Since voltages are not be used in this algorithm, the measurement error of PT and CT will not affect on location accuracy. The presented algorithm has less calculation burden, and the accuracy is independent of fault transition impedance and its property, fault type, fault position and load current. The fault location function has no false root in theory.Due to the fact that the distributed capacitive current in three-terminal transmission lines significantly influences the protection performance of current differential protection, such influence should be taken into account in the protection principle. On the basis of new research findings of current differential protection for two-terminal transmission lines, a new distributed parameter model based principle of current differential protection for three-terminal transmission lines is proposed. Translating original current differential protection for three-terminal transmission line into two current differential protections for two-terminal transmission lines, which are similar in principle, the correctness of such a translation is strictly proved by distributed parameter model. Comparing with traditional post-fault current differential protection for three-terminal transmission lines, new protection criterion is not influenced by distributed capacitive current, so it is suitable to three-terminal high voltage transmission lines.The estimation error in the fault current phase angle based on the zero sequence current at the relay installed location is the key influential factor for the zero-sequence reactance relay and its improved ground reactance relay to be applicated in Ultra-high-voltage long AC transmission lines. To tackle the problem, an improvement of zero sequence reactance relay with applications in Ultra-High-Voltage long AC Transmission Lines is proposed. It is based on the principle that the negative current phase angle in fault path can be precisely estimated by the negative sequence current phase angle at the relay installed location with single-phase-to-ground faults.The protection has very strong ability against transient resistance and stability protective zone and high operation sensitivity with single-phase-to-ground faults.更多还原