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This paper presents a universal fault location technique for N-terminal (N [??] 3) transmission lines based on synchronized phasor measurement units. The development of the technique is based on two-terminal fault location technique. The proposed algorithm is different from traditional multiterminal fault location techniques. We apply two-terminal fault location technique to N-terminal transmission lines and propose a novel fault section selector/fault locator. The proposed method has a very good tolerance. The proposed approach provides an analytical solution and its computational burden is very low since it does not require iterative operations. An extensive series of simulations were conducted to verify the accuracy of the proposed algorithm. The average fault location error under various fault conditions is well below 1%. Index Terms--Fault location, multiterminal transmission lines, phasor measurement units (PMUs).

This paper presents a concept of fault-location observability and a new fault-location scheme for transmission networks based on synchronized phasor measurement units (PMUs). Using the proposed scheme, minimal PMUs are installed in existing power transmission networks so that the fault, if it occurs, can be located correctly in the network. The scheme combines the fault-location algorithm and the fault-side selector. Extensive simulation results verify the proposed scheme. Index Terms--Fault location, phasor measurement unit (PMU), transmission network.

This paper presents the application of a combined adaptive Fourier filtering technique and fault detector to fast distance protection of transmission lines. The filtering technique is extended from the Fourier filters and can be applied under arbitrary data window length. The proposed filtering technique possesses the advantage of recursive computing, and a decaying dc offset component is removed from fault signals by using an adaptive compensation method. A variable data window scheme is embedded in the technique to adaptively speed up its transient response under various system and fault conditions. A fault detector is developed to initiate the process of the technique. For the sake of speed and security, two phasor estimation methods based on the proposed technique are designed to achieve fast distance protection. An algorithm consisting of the two methods is used to detect internal faults by 'OR' logic. Extensive simulation studies show that the algorithm significantly reduces tripping time of a distance relay and provides better protection performance than that of the conventional filters with fixed data windows. Index Terms--Adaptive filtering, computer relaying, decaying dc offset, digital distance protection, discrete Fourier transform (DFT).

A new fault detection/location technique with consideration of arcing fault discrimination based on phasor measurement units for extremely high voltage/ultra-high voltage transmission lines is presented in this two-paper set. Part I of this two-paper set is mainly aimed at theory and algorithm derivation. The proposed fault detection technique for both arcing and permanent faults is achieved by a combination of a fault detection index |M| and a fault location index |D|, which are obtained by processing synchronized fundamental phasors. One is to detect the occurrence of a fault and the other is to distinguish between in-zone and out-of-zone faults. Furthermore, for discriminating between arcing and permanent faults, the proposed technique estimates the amplitude of arc voltage by least error squares method through the measured synchronized harmonic phasors caused by the nonlinear are behavior. Then, the discrimination will be achieved by comparing the estimated amplitude of are voltage to a given threshold value. In addition, in order to eliminate the error caused by exponentially decaying dc offset on the computations of fundamental and harmonic phasors, an extended discrete Fourier transform algorithm is also presented. Index Terms--Arcing fault discrimination, extended discrete Fourier transform (EDFT), fault detection, fault location, phasor measurement unit (PMU).

This paper presents a new adaptive fault protection scheme for transmission lines using synchronized phasor measurements. The work includes fault detection, direction discrimination, classification, and location. Both fault-detection and fault-location indices are derived by using two-terminal synchronized measurements incorporated with distributed line model and modal transformation theory. The fault-detection index is composed of two complex phasors and the angle difference between the two phasors determines whether the fault is internal or external to the protected zone. The fault types can be classified by the modal fault-detection index. The proposed scheme also combines online parameter estimation to ensure protection scheme performance and achieve adaptive protection. Extensive simulation studies show that the proposed scheme provides a fast relay response and high accuracy in fault location under various system and fault conditions. The proposed method responds very well with regards to dependability, security, and sensitivity (high-resistance fault coverage). Index Terms--Computer relaying, digital protection, global positioning system (GPS), phasor measurement unit (PMU), transmission-line protection.

This paper proposes a novel adaptive relaying scheme based on phasor-measurement units (PMUs) for transmission lines. The proposed adaptive relaying scheme can provide an extremely accurate discrimination between in-zone and out-of-zone faults. Two novel and composite fault discrimination indices in terms of Clarke components of synchronized voltage and current phasors at two ends of a line are derived. A line parameter estimation algorithm is developed and built in the newly designed relay to solve the uncertainty problem of line parameters. The proposed relaying scheme is independent of fault types, fault locations, fault path resistance, fault inception angles, and the variations of source impedance. The tripping decision time of the designed relay is very fast and almost held well within 6 ms for most fault events. All of the EMTP simulation results show that the proposed adaptive relaying scheme provides a high level of dependability and security. Index Terms--Adaptive relaying, global positioning system (GPS), line relaying, phasor-measurement unit (PMU).

This paper presents a new fault location algorithm based on phasor measurement units (PMUs) for series compensated lines. Traditionally, the voltage drop of series device is computed by the device model in the fault locator of series compensated lines, but using this approach errors are induced by the inaccuracy of the series device model or the uncertainty operation mode of the series device. The proposed algorithm does not utilize the series device model and knowledge of the operation mode of the series device to compute the voltage drop during the fault period. Instead, the proposed algorithm uses two-step algorithm, prelocation step and correction step, to calculate the voltage drop and fault location. The proposed technique can be easily applied to any series FACTS compensated line. EMTP generated data using a 30-km 34-kV transmission line has been used to test the accuracy of the proposed algorithm. The tested cases include various fault types, fault locations, fault resistances, fault inception angles, etc. The study also considers the effect of various operation modes of the compensated device during the fault period. Simulation results indicate that the proposed algorithm can achieve up to 99.95% accuracy for most tested cases. Index Terms--FACTS, series compensation, synchronized phasor measurement units.

A precise digital algorithm based on Discrete Fourier Transforms (DFT) to estimate the frequency of a sinusoid with harmonics in real-time is proposed. This algorithm that we called the Smart Discrete Fourier Transforms (SDFT) smartly avoids the errors that arise when frequency deviates from the nominal frequency, and keeps all the advantages of the DFT e.g., immune to harmonics and the recursive computing can be used in SDFT. These make the SDFT more accurate than conventional DFT based techniques. In addition, this method is recursive and very easy to implement, so it is very suitable for use in real-time. We provide the simulation results compared with a conventional DFT method and second-order Prony method to validate the claimed benefits of SDFT. Index Terms--Discrete Fourier Transforms (DFT), frequency estimation, phasor measurement.

Part I of this paper set sets forth theory and algorithms for adaptive fault detection/location technique, which is based on Phasor Measurement Unit (PMU). This paper is Part II of this paper set. A new timing device named 'Global Synchronism Clock Generator, GSCG' including its hardware and software design is described in this paper. Experimental results show that the synchronized error of rising edge between the two GSCGs clock is well within 1 ps when the clock frequency is below 2.499 MHz. The measurement results between Chung-Jeng and Chang-Te 161 kV substations of Taiwan Power company by PMU equipped with GSCG is presented and the accuracy for estimating parameters of line is verified. The new developed DFT based method (termed as Smart Discrete Fourier Transform, SDFT) and line parameter estimation algorithm are combined with PMU configuration to form the adaptive fault detector/locator system. Simulation results have shown that SDFT method can extract exact phasors in the presence of frequency deviation and harmonics. The parameter estimation algorithm can also trace exact parameters very well. The SDFT method and parameter estimation algorithm can achieve accuracies of up to 99.999% and 99.99%, respectively. The EMTP is used to simulate a 345 kV transmission line of Taipower System. Results have shown that the proposed technique yields correct results independent of fault types and is insensitive to the variation of source impedance, fault impedance, and line loading. The accuracy of fault location estimation achieved can be up to 99.9% for many simulated cases. The proposed technique will be very suitable for implementation in an integrated digital protection and control system for transmission substations. Index Terms--Discrete Fourier transforms (DFT), fault detection/location index, phasor measurement unit (PMU).

A correct and rapid inference is required for practical use of an on-line fault diagnosis in power substations. This paper proposes a novel approach for on-line fault section estimations and fault types identification using the hybrid cause-effect network/fuzzy rule-based method in distribution substations. A cause-effect network, which is well suited to parallel processing, represents the functions of protective relays and circuit breakers for selection of faulted sections. Therefore the inference speed can be improved significantly. In order to deal with the uncertainties involved in the process of clarifying faults, a fuzzy rule-based method is derived. The proposed approach has been practically verified by testing on a typical Taiwan Power Company's (Taipower) secondary substation. The experimental results reveal that the correct and rapid diagnosis is obtained even for the fault domains involving multiple faults and failure operations of protective devices. Moreover, it is easy to implement and transplant into different substations. Index Terms--Fault diagnosis, Cause-effect network, Fuzzy rule-based method.

A series of precise digital algorithms based on Discrete Fourier Transforms (DFT) to calculate the frequency and phasor in real-time are proposed. These algorithms that we called the Smart Discrete Fourier Transforms (SDFT) family not only keep all of the advantages of DFT but also smartly take frequency deviation, and harmonics into consideration. These make the SDFT family more accurate than the other methods. Besides, SDFT family is recursive and very easy to implement, so it is very suitable for use in real-time. We provide the simulation results compared with conventional DFT method and second-order Prony method to validate the claimed benefits of SDFT. Index Terms--Discrete Fourier Transforms (DFT), Frequency estimation, phasor measurement.

An adaptive fault detection/location technique based on Phasor Measurement Unit (PMU) for an EHV/UHV transmission line is presented in this two paper set. This paper is Part I of this set. A fault detection/location index in terms of Clarke components of the synchronized voltage and current phasors is derived. The line parameter estimation algorithm is also developed to solve the uncertainty of parameters caused by aging of transmission lines. This paper also proposes a new Discrete Fourier Transform (DFT) based algorithm (termed as Smart Discrete Fourier Transform, SDFT) to eliminate system noise and measurement errors such that extremely accurate fundamental frequency components can be extracted for calculation of fault detection/location index. The EMTP was used to simulate a high voltage transmission line with faults at various locations. To simulate errors involved in measurements, Gaussian-type noise has been added to the raw output data generated by EMTP. Results have shown that the new DFT based method can extract exact phasors in the presence of frequency deviation and harmonics. The parameter estimation algorithm can also trace exact parameters very well. The accuracy of both new DFT based method and parameter estimation algorithm can achieve even up to 99.999% and 99.99% respectively, and will be presented in Part H. The accuracy of fault location estimation by the proposed technique can achieve even up to 99.9 % in the performance evaluation, which is also presented in Part II. Index Terms--Fault Detection/Location Index, Discrete Fourier Transforms (DFT), Phasor Measurement Unit (PMU).

A new method for estimating fault sections in power substations is proposed. In this paper, the knowledge representation and inference procedures based on the cause-effect networks (CE-Nets) and rule matrix transformation techniques are presented. The matrix based inference procedures are proposed to estimate the possible fault sections through simple matrix operations by transforming the established CE-Nets into matrix forms. The method is superior to existing production systems in the inference speed and the process of implementation. By testing on a typical Taiwan Power Company's (Taipower) secondary substation, the experimental results show that the effectiveness of the proposed method even for the fault domains involving multiple faults and failure operations of protective devices. Moreover, it is easy to implement and transplant into different substations. Index Terms--Cause-effect network, fault diagnosis, rule matrix.

The theory and algorithms of the proposed technique have been presented in Part I of this two-paper set. In Part II of this two-paper set, the proposed technique is evaluated by considerable simulation cases simulated by the Mattab/Power system Blockset simulator. For the proposed fault detector, the trip time achieved can be up to 3.25 ms and the average value of trip times is about 8 ms for both permanent and arcing faults on transmission lines. For the proposed fault locator, the accuracy can be up to 99.99% and the error does not exceed 0.45%. Moreover, the proposed arcing fault discriminator can discriminate between arcing and permanent faults within four cycles after fault inception. It has proven to be an effective tool to block reclosing on the permanent faults in the computer simulations. The simulation results also demonstrate that the presented extended discrete Fourier transform algorithm eliminates effectively the error caused by exponentially decaying dc offset on fundamental and harmonic phasor computations. Finally, a test case using the real-life measured data proves the feasibility of the proposed technique. [ABSTRACT FROM AUTHOR]