Fault resistance sensitivity of sparse measurement based transmission line fault location Papiya Dutta Dept. of Electrical and Computer Engineering Texas A & M University College Station, TX, USA papiya82@tamu.edu Mladen Kezunovic Dept. of Electrical and Computer Engineering Texas A & M University College Station, TX, USA kezunov@ece.tamu.edu Abstract—Traditional transmission line fault location methods require measurements from at least one end of the faulted line. Measurements from all the ends of the faulted line are desirable but not always available. Sparse measurement based fault location scheme using phasor measurements from different substations located in the vicinity where the fault has occurred can be applied if the measurements are not available from any of the line ends. Fault resistance is one of the major sources of uncertainty in transmission line fault location estimation. This paper presents a correction scheme to reduce impact of fault resistance on sparse measurement method. I. INTRODUCTION Transmission lines exposed to different weather, as well as human and animal contact are subject to several types of faults which are caused by random and unpredictable events. Protective relays placed at both (all) ends of the line sense the fault immediately and isolate the faulted line by opening the associated circuit breakers. To restore service after a fault, an accurate location of the fault is needed to help the maintenance crew find and repair the faulted line section as soon as possible. Fault may occur between transmission line phases or have a ground return path. When a phase-to-phase fault occurs, the fault current flows through arc resistance and if the fault is a ground fault the current path includes earth resistance (consists of tower resistance, tower footing resistance and ground return path) also. Fault resistance is the combined resistance which appears in the fault current path. This is an uncertain parameter as both the arc resistance and earth resistance depend on many parameters that are sometimes very hard to predict. Distance relay algorithm selectivity may suffer from the combined effect of fault resistance and load current which is known as reactance effect [1]. Such algorithms assume that the fault current is in phase with measured current. Presence of remote infeed complicates the situation. Takagi et al. [2-3] decomposed the faulted network to pre-fault and pure-fault network and take some assumptions to eliminate fault resistance part from the circuit equation. Another one-end method using quadratic formula to eliminate fault resistance is introduced in [4] yielding much more accurate result. Using one-end data to estimate fault resistance by modeling the arc is discussed in [5-6]. [7] is based on equalizing voltage of fault point from both ends of the line based on measurements from both ends and thus eliminates the impact of fault resistance . A settings free fault location method using synchronized samples from both ends of the line is completely independent of fault resistance, which is not used to develop the algorithm [8]. Typically digital fault recorders (DFRs) or digital protective relays (DPRs) are placed in substations and they record current, voltage and status signals on occurrence of an event like fault. Due to the lack of measurement transformers in certain transmission line configurations such as tapped lines availability of measurements from at least one end of the line becomes a problem. If the measurements from other ends are not available, some unconventional fault location techniques based on system-wide sparse measurements may have to be used [9-10]. In this case, fault location is estimated by using measurements recorded from IEDs installed in the substations close to the faulted line (but not from the ends of the line) and also using SCADA measurements from all the substations near the fault. Performance of the system-wide sparse measurement based fault location algorithms depend on fault resistance. The analysis of the impact of the fault resistance on the sensitivity of fault location output is crucial for estimating an accuracy of the output. In [11-12] sensitivity of one-end fault location methods is analyzed to determine most contributing uncertainty factors and interaction of uncertainty factors. This paper explains how accuracy of system wide sparse measurement based fault location can be impacted by fault resistance. An intuitive scheme to choose proper fault resistance range is also proposed. The next section is focused on describing sparse measurement based fault location method and the correction scheme proposed to reduce sensitivity to fault resistance. Software implementation and case study are discussed in the subsequent sections followed by the conclusion.