Fault Location in Transmission Systems Using Synchronized Measurements

Compared with conventional measurements from supervisory control and data acquisition (SCADA) system, phasor measurement units (PMUs) provide time-synchronized and direct measurements of phasors. The availability of synchronized phasor measurements can significantly improve power system protection and analysis. This dissertation is specifically committed to using synchronized measurements for estimation of fault locations in transmission systems. Transmission lines are prone to various short-circuit faults. Accurate fault location is critical for rapid power recovery. Chapter 2 proposes a new fault location method based on sparse wide area measurements. One distinguishing feature of this method is its applicability to both transposed and untransposed transmission lines. In addition, the method is developed based on sparse-wide area measurement that may be taken far away from the faulted line. Shunt capacitances of transmission lines are also fully considered by the algorithm. Moreover, when synchronized measurements from multiple buses are available, an optimal estimator can be used to make the most use of measurements, and to detect and identify potential bad measurements. Most of the existing fault location literatures discuss common shunt faults, including single line-to-ground faults, line-to-line faults, line-to-line-to-ground faults, and three-phase faults. However, in addition to common shunt faults, some complex faults may also occur in power systems. Among these complex faults, evolving fault and inter-circuit fault are two typical examples. Chapter 3 extends the method developed in Chapter 2 to deal with evolving faults. The proposed wide-area fault location methods are immune to fault type evolution, and are applicable to both transposed and untransposed lines. Chapter 4 discusses location of inter-circuit faults. Inter-circuit fault is a type of simultaneous fault, and it is the most common simultaneous fault type. Inter-circuit faults between each circuit in a double-circuit line is the most common inter-circuit fault. A fault location method for inter-circuit faults on double-circuit lines are developed and evaluated in Chapter 4. Chapter 5 puts forward a fault location algorithm, which does not require line parameters information, for series-compensated transmission lines. Two-end synchronized voltage and current measurements are utilized. The proposed method is independent of source impedance and fully considers shunt capacitances of transmission lines

Protection of major transmission lines using travelling-waves

An ultra high speed relay for the protection of long EBY transmission lines is described in this thesis. The need for ultra high speed relays is first discussed. From a brief review of protection based on "impedance" distance algorithms or methods using post fault transients, it is shown that at present, there is no truly ultra high speed relay available for the protection of long EBY transmission lines. The proposed relay operates on the incident fault transient travelling waves received at the relaying point only. After the arrival of the first incident transient at the relaying point all subsequent incident travelling waves are detected using the cross-correlation of the first reflected wave with the incident transient waves. From the amplitudes of the subsequent incident transients, two fault resistance estimates are obtained. These two fault resistance estimates are in agreement only for the subsequent incident wave which is caused by direct reflection from the fault. The fault location can then be determined from the time of arrival of this wave. Additional checks based on the ground mode delay or the line round trip wave amplitude, are incorporated to enhance further the security of the scheme. Good fault discrimination is shown to be possible over a large range of fault resistances for symmetric three phase faults to ground, phase to ground faults and phase to phase faults. Double circuit transmission lines and compensated transmission lines can also be protected. The relay has good noise tolerance and a reasonable bandwidth requirement. A real time implementation of the basic algorithm for an internal phase-a to ground fault shows that an ultra high speed relay response with good accuracy can be achieved using currently available digital hardware

Protection of major transmission lines using travelling-waves

An ultra high speed relay for the protection of long EBY transmission lines is described in this thesis. The need for ultra high speed relays is first discussed. From a brief review of protection based on "impedance" distance algorithms or methods using post fault transients, it is shown that at present, there is no truly ultra high speed relay available for the protection of long EBY transmission lines. The proposed relay operates on the incident fault transient travelling waves received at the relaying point only. After the arrival of the first incident transient at the relaying point all subsequent incident travelling waves are detected using the cross-correlation of the first reflected wave with the incident transient waves. From the amplitudes of the subsequent incident transients, two fault resistance estimates are obtained. These two fault resistance estimates are in agreement only for the subsequent incident wave which is caused by direct reflection from the fault. The fault location can then be determined from the time of arrival of this wave. Additional checks based on the ground mode delay or the line round trip wave amplitude, are incorporated to enhance further the security of the scheme. Good fault discrimination is shown to be possible over a large range of fault resistances for symmetric three phase faults to ground, phase to ground faults and phase to phase faults. Double circuit transmission lines and compensated transmission lines can also be protected. The relay has good noise tolerance and a reasonable bandwidth requirement. A real time implementation of the basic algorithm for an internal phase-a to ground fault shows that an ultra high speed relay response with good accuracy can be achieved using currently available digital hardware

An equivalent circuit for the evaluation of cross-country fault currents in medium voltage (MV) distribution networks

A Cross-Country Fault (CCF) is the simultaneous occurrence of a couple of Line-to-Ground Faults (LGFs), affecting different phases of same feeder or of two distinct ones, at different fault locations. CCFs are not uncommon in medium voltage (MV) public distribution networks operated with ungrounded or high-impedance neutral: despite the relatively small value of LGF current that is typical of such networks, CCF currents can be comparable to those that are found in Phase-To-Phase Faults, if the affected feeder(s) consists of cables. This occurs because the faulted cables' sheaths/screens provide a continuous, relatively low-impedance metallic return path to the fault currents. An accurate evaluation is in order, since the resulting current magnitudes can overheat sheaths/screens, endangering cable joints and other plastic sheaths. Such evaluation, however, requires the modeling of the whole MV network in the phase domain, simulating cable screens and their connections to the primary and secondary substation earth electrodes by suitable computer programs, such as ATP (which is the acronym for alternative transient program) or EMTP (the acronym for electromagnetic transient program), with substantial input data being involved. This paper presents a simplified yet accurate circuit model of the faulted MV network, taking into account the CCF currents' return path (cable sheaths/screens, ground conductors, and earthing resistances of secondary substations). The proposed CCF model can be implemented in a general-purpose simulation program, and it yields accurate fault currents estimates: for a 20 kV network case study, the comparison with accurate ATP simulations evidences mismatches mostly smaller than 2%, and never exceeding 5%

Monitoring and Fault Location Sensor Network for Underground Distribution Lines

One of the fundamental tasks of electric distribution utilities is guaranteeing a continuous supply of electricity to their customers. The primary distribution network is a critical part of these facilities because a fault in it could affect thousands of customers. However, the complexity of this network has been increased with the irruption of distributed generation, typical in a Smart Grid and which has significantly complicated some of the analyses, making it impossible to apply traditional techniques. This problem is intensified in underground lines where access is limited. As a possible solution, this paper proposes to make a deployment of a distributed sensor network along the power lines. This network proposes taking advantage of its distributed character to support new approaches of these analyses. In this sense, this paper describes the aquiculture of the proposed network (adapted to the power grid) based on nodes that use power line communication and energy harvesting techniques. In this sense, it also describes the implementation of a real prototype that has been used in some experiments to validate this technological adaptation. Additionally, beyond a simple use for monitoring, this paper also proposes the use of this approach to solve two typical distribution system operator problems, such as: fault location and failure forecasting in power cables.Ministerio de Economía y Competitividad, Government of Spain project Sistema Inteligente Inalámbrico para Análisis y Monitorización de Líneas de Tensión Subterráneas en Smart Grids (SIIAM) TEC2013-40767-RMinisterio de Educación, Cultura y Deporte, Government of Spain, for the funding of the scholarship Formación de Profesorado Universitario 2016 (FPU 2016

Transient fault area location and fault classification for distribution systems based on wavelet transform and Adaptive Neuro-Fuzzy Inference System (ANFIS)

A novel method to locate the zone of transient faults and to classify the fault type in Power Distribution Systems using wavelet transforms and Adaptive Neuro-Fuzzy Inference Systems (ANFIS) has been developed. It draws on advanced techniques of signal processing based on wavelet transforms, using data sampled from the main feeder current to extract important characteristics and dynamic features of the fault signal. In this method, algorithms designed for fault detection and classification based on features extracted from wavelet transforms were implemented. One of four different algorithms based on ANFIS, according to the type of fault, was then used to locate the fault zone. Studies and simulations in an EMTP-RV environment for the 25kV power distribution system of Canada were carried out by considering ten types of faults with different fault inception, fault resistance and fault locations. The simulation results showed high accuracy in classifying the type of fault and determining the fault area, so that the maximum observed error was less than 2%

A Review of Fault Diagnosing Methods in Power Transmission Systems

Transient stability is important in power systems. Disturbances like faults need to be segregated to restore transient stability. A comprehensive review of fault diagnosing methods in the power transmission system is presented in this paper. Typically, voltage and current samples are deployed for analysis. Three tasks/topics; fault detection, classification, and location are presented separately to convey a more logical and comprehensive understanding of the concepts. Feature extractions, transformations with dimensionality reduction methods are discussed. Fault classification and location techniques largely use artificial intelligence (AI) and signal processing methods. After the discussion of overall methods and concepts, advancements and future aspects are discussed. Generalized strengths and weaknesses of different AI and machine learning-based algorithms are assessed. A comparison of different fault detection, classification, and location methods is also presented considering features, inputs, complexity, system used and results. This paper may serve as a guideline for the researchers to understand different methods and techniques in this field