Sharif Digital Repository

In this paper, a new algorithm for fault detection/location on transmission line based on linear state estimation is presented. The proposed technique uses phasor measurements from PMU's. Fault location and voltage of fault point are added as the new state variables in a linear state estimator based on PMU data. In addition, by using the ability of bad data identification in the state estimation, a new scheme for fault location and identification of faulted transmission line is proposed. For test and validation of the proposed algorithm, simulation results on a six bus test case are presented. ©2009 IEEE  

This paper presents a novel approach for fault location of overhead transmission lines by voltage and current measurements in a remote substation. The method is applicable when not all of the transmission lines in an area are equipped with fault-locators, although there may be a critical substation (CS) in the area equipped with a digital fault recorder (DFR). In the proposed method, the circuit equations of the network are used to find the transfer function between the fault location and each voltage and current measurement in the CS. Next, two auxiliary variables are defined to transform the nonlinear fault location estimation problem into a linear least squares problem. A closed-form... 

This study presents a novel method for fault location of transmission lines by multiple fault current measurements. In contrast to conventional methods, it is proposed to utilise several current measurements, which may be far from the faulted line. The circuit equations of the network are used to express each fault current as a function of fault location. Fault location is then estimated using a least-squares estimation technique. To achieve a robust estimation of fault location, statistical hypotheses-testing is employed for identifying erroneous measurements. The method is applicable to both synchronised and unsynchronised measurements. Moreover, fault location can be estimated regardless... 

In this paper, an accurate fault location algorithm for series compensated power transmission lines is presented. Distributed time domain model is used for modeling of the transmission lines. The algorithm makes use of two subroutines for estimation of the fault distance - one for faults behind the series capacitors and another one for faults in front of the series capacitors. Then a special procedure to select the correct solution is utilized. Samples of voltages and currents at both ends of the line are taken synchronously and used to calculate the location of the fault. The proposed algorithm is independent of fault resistance and does not require any knowledge of source impedance. The... 

In this paper we propose a new fault location algorithm for power transmission lines based on one terminal voltage and current data. A distributed time domain model of the line is used as a basis for algorithm development. The suggested technique only takes advantage of post-fault voltage and current samples taken at one end of the line and does not require filtering of DC offset and high-frequency components of the recorded signals, which are present during transient conditions. Another advantage of the proposed method is the application of a very narrow window of data i. e. less than 1/4 of a cycle. The paper also proposes two different algorithms for lossless and lossy line models.... 

In this paper, an accurate fault location algorithm for series compensated power transmission lines is presented. A distributed time domain model is used for modeling of the transmission lines. The algorithm makes use of two subroutines for estimation of the fault distance-one for faults behind the series capacitors and another one for faults in front of the series capacitors. Then a special procedure to select the correct solution is utilized. Samples of voltages and currents at both ends of the line are taken synchronously and used to calculate the location of the fault. The proposed algorithm is independent of fault resistance and does not require any knowledge of source impedance. The... 

The accurate fault location is an important criterion for protection system. Accurate and fast fault location decreases the outage time, consumers dissatisfaction and operation cost. Different methods have been proposed to determine the fault location. The impedance-based methods are usually used to protect power systems. The accuracy of these methods depends on system parameters and the structure of power systems. Also, these methods require an iterative process, the phase alignment and a high volume of data. Another algorithm has been newly presented based on negative sequence parameters, which is not iterative and the amount of data communicated between relays is small. Besides, this... 

In this paper, the problem of placing a minimum number of phasor measurement units (PMUs) in a transmission system is considered so that faults on all lines of the network can be diagnosed and located irrespective of their locations. For this purpose, a PMU placement algorithm is applied to calculate the required data for impedance-based fault location of any fault line in the network, achieving the full potential of the circuit laws throughout the system. Another algorithm is then proposed to compute the voltage and current values of the fault line for fault-location purposes. Moreover, as many networks are already equipped with PMUs, the proposed algorithm makes it possible to locate... 

Power system equipments are normally designed for a specific system and load situation. This situation could change significantly as a result of the system expansion or aging. Among the system equipments, circuit breakers are more sensitive to the system expansion and they must be able to isolate the faulty components if a fault occurs. As the system load increases in the future, the power network must be expanded. In this situation, either the switching equipments must be replaced in order to be able to respond to the new fault current or the fault current must be limited to the interrupting capability of the existing circuit breakers. Application of Fault current Limiters (FCL) serves as a... 

A short circuit fault in an AC railway supply system could have undesired consequences; including high-amplitude current flow in the power path, the rail potential rise in the fault vicinity. This paper studies the problem of the rail voltage rise in Tehran-Karaj railway system by the use of a steady state circuit model for the AC autotransformer during a phase-to-ground fault. By using this model, all the currents and voltages of the system can be easily calculated for all possible short circuit fault locations. With the help of the derived analytical model, one can also predict the possible fault locations which may cause the protection system to operate. The estimation of the system... 

This paper presents an efficient High-Level Synthesis (HLS) approach to improve RT-Level concurrent testing. The proposed method used for both fault detection and fault location. At first the available resources are used in their dead intervals to test active resources for fault detection, and then some changes are applied to the RT-Level controller to locate the faults. The fault detection step is based on a genetic algorithm (GA) search technique. This genetic algorithm is applied to the design after high level synthesis process to explore the test map. The proposed method has been evaluated based on dependability enhancement and area/latency overhead imposed to different benchmarks after... 

The main concern of steganography (image hiding) methods is to embed a secret image into a host image in such a way that it causes minimum distortion to the host; to make it possible to extract a version of secret image from the host in such a way that the extracted version of secret image be as similar as possible to its original version (this should be possible even after usual attacks on the host image), and to provide ways of embedding secret images with larger size into a given host image. In this paper we propose a method that covers all above mentioned concerns by suggesting the idea of finding from an image data base, the most suitable host for a given secret image. In our method,...