A method for the computation of fault location in two- and three-terminal high voltage lines is presented. It is based on digital computation of the three-phase current and voltage 60/50 Hz phasors at the line terminals. The method is independent of fault type and insensitive to source impedance variation or fault resistance. Furthermore, it considers the synchronization errors in sampling the current and voltage waveforms at the different line terminals. The method can be used online following the operation of digital relays or offline using data transferred to a central processor from digital transient recording apparatus. The authors start with a two-terminal line to explain the principles and then present the technique for a three-terminal line. The technique was first tested using data obtained from a steady-state fault analysis program to evaluate the convergence, observability, and uniqueness of the solution. The technique was then tested using EMPT-generated transient data. The test results show the high accuracy of the technique. >

A new fault location technique for two- and three-terminal lines

This paper describes a fault location algorithm for three terminal lines using wavelet transform of the fault initiated transients. The results presented in are extended to the case of three terminal configuration and a new single ended procedure is developed for teed circuits. The algorithm gives accurate results for the case of three terminal lines including series compensated branch, mutual coupled line section and different values of fault resistances. The performance of the algorithm is tested on different scenarios by using ATP/EMTP program and MATLAB Wavelet Toolbox.

Travelling wave based fault location for teed circuits

Earlier work at Texas A&M University led to the development of transmission line fault location algorithms that were based on synchronized sampling of the voltage and current data from the two ends of the line. The line models used in the algorithms were based on lumped parameter models for electrically short lines, or lossless distributed parameter models for electrically long lines. In this paper, the lossless line model is modified to account for the series losses in the line. The line model equations are then solved in the time domain to accurately locate the fault. Testing of the modified algorithm is performed on a power system belonging to the Western Area Power Administration. Extensive EMTP based simulations are used to generate data that are supplied as inputs to the fault location algorithm. To make the testing as realistic as possible, detailed models of instrument transformers are used in the simulation of the various fault cases.

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Fault location using the distributed parameter transmission line model

A technique is presented for accurate fault location on distribution overhead lines and underground cables. A specially designed fault locator unit is used to capture the high-frequency voltage transient signal generated by faults on the distribution line/cable. The travelling time of the high-frequency components is used to determine the fault position. The technique is insensitive to fault type, fault resistance, fault inception angle and system source configuration, and is able to offer very high accuracy in fault location in a distribution system.

Accurate fault location technique for distribution system using fault-generated high-frequency transient voltage signals

This paper delineates a novel analytical and computational approach to fault location for power transmission grids. The proposed methodology involves an online and an offline stage. The online stage is based solely on the utilization of the time-of-arrival (ToA) measurements of traveling waves propagating from the fault-occurrence point to synchronized wide-area monitoring devices installed at strategically selected substations. The captured waveforms are processed together at the time of fault in order to identify the location of the fault under study. The overall performance of the developed technique is demonstrated using Alternative Transients Program (ATP) simulations of fault transients and postprocessing the faulted waveform data via discrete wavelet transform. The applicability of the algorithm is independent of the fault type and can readily be extended to transmission grids of any size.

Traveling-Wave-Based Fault-Location Technique for Transmission Grids Via Wide-Area Synchronized Voltage Measurements

The high frequency components in fault waveforms present undesirable effects to most fault location algorithms and as a consequence filtering of postfault signals, to remove the high frequency transients, is essential for accurate fault location. A fault location algorithm that derives from travelling wave principles can cope with high frequency transients since these basically depend on travelling wave phenomena. The development of such an algorithm is the objective of this paper. Using the telegraph equations as a line model, voltage and current samples taken at one end of a line within the first 5 ms of fault inception are used to generate instantaneous voltage and current profiles for the rest of the transmission line. The voltage and current estimation is based on the solution of the equations of the line model by the method of characteristics. Criteria functions involving any of the square of the voltage, the square of the current, or the product of the two are applied for determination of the fault position. Fault position is given by the peak variation in tangent to the above basic functions. The algorithm finds application in fault location on two and three-terminal networks at both transmission and distribution levels.

A Travelling Wave-Based Fault Locator for Two- and Three-Terminal Networks

Improved mathematical models of transmission lines are used to develop a fault location method which copes with high-frequency transients. The telegraph equations used for a line model are solved by the method of characteristics using voltage and current samples as boundary conditions taken at one end of the line within the first few milliseconds of fault inception. Estimates of voltage and current profiles for the entire length of the transmission line during the fault are obtained. Criteria for fault location are based on a formulation involving these voltage and current estimates. For fault location on multiphase systems the concept of modal analysis is used in enhancing the fault-locating capability of this algorithm.

Fault-location algorithm for multiphase power lines

The grid is a network that connects all the major power stations and load centers in a country (or power system). The constraints to grid operations include generation, transmission, and system control. Remedial actions aimed at addressing these problems are presented. The high point of the recommendations is the adoption of “Distributed Generation Scheme”. In the absence of an accurate load demand, regional sales of electric energy were used to estimate regional demand for electricity. These were in turn used to decide location of new generating plants under the distributed generation scheme.

http://www.akamaiuniversity.us/PJST10_2_486.pdf

A Critical Review of Grid Operations in Nigeria.

Transients in power systems are initiated by abrupt changes to otherwise steady operating conditions. These changes would be as a result of any of the following: opening or closing of circuit breakers, switching conditions, lightning or any other fault condition. For purposes of power system analysis these conditions are simulated using mathematical models. In the formulation of these mathematical models efforts are made to represent changes in transmission line characteristics, such as the variation of line parameters with frequency. Electromagnetic (EM) transients produced by these mathematical models serve as a useful reference in the design of protective devices and fault locators. It is therefore pertinent to examine the effect of faithful reproduction of line characteristics in the simulated transients with respect to the performance of fault locators tested with the simulated transients. Such investigation has shown that the computational burden involved in trying to represent all line characteristics in transients calculations could be saved.

/pdf/simulation-of-electromagnetic-transients-in-power-systems-3hg6mcl429.pdf

A. O. Ibe

Papers

A Travelling Wave-Based Fault Locator for Two- and Three-Terminal Networks

Fault-location algorithm for multiphase power lines

A Critical Review of Grid Operations in Nigeria.

Simulation of Electromagnetic Transients in Power Systems

A travelling wave-based fault locator for two- and three-terminal networks