Series Capacitor Compensated Transmission Line Research Articles

Series capacitor-compensated double-circuit transmission line directional relay system using a fuzzy expert system with a Haar wavelet

Series capacitor-compensated double-circuit transmission line directional relay system using a fuzzy expert system with a Haar wavelet

Local current-based method for fault identification and location on series capacitor-compensated transmission line with different configurations

This paper proposes a new efficient method for fault detection, faulty phase selection, and fault point identification on series capacitor-compensated transmission line. The method is based on sensing only the three phase current at the relay site. A reverse synchronous reference frame (RSRF) approach is proposed for fast fault detection and classification. Then, an analytical algorithm based on symmetrical components theory is presented for accurate estimation of fault location. Three possible arrangements of the series capacitor bank (SCB) on the line are analyzed. The SCB and the associated protective metal oxide surge arrestor (MOV) are modeled thoroughly to characterize its behavior during fault. In addition to its simplicity and practicality, the proposed scheme is equipped with decaying DC offset removal technique that allows fast extraction of the current phasors within one fundamental cycle. The proposed method works well for all ground and non-ground faults; it does not need pre-fault information; does not require any communication facilities; avoids high voltage measurement; and works smoothly for a wide range of fault resistance values. The efficacy of the proposed method is proved by a large number of simulated cases under a variety of operating conditions.

Fault detection during power swing in thyristor-controlled series capacitor-compensated transmission lines

Fault detection during power swing in compensated transmission lines by Thyristor Controlled Series Capacitors (TCSCs) is a challenging problem and conventional detection methods might not be accurate. In this paper, a high speed fault detection approach based on Mathematical Morphology is proposed. The proposed method uses voltage and current signals for fault and swing detections, respectively. The performance of the proposed method is evaluated using two simulation case studies simulated in PSCAD/EMTDC: (i) a single machine infinite bus network and (ii) IEEE standard 9 bus three machine network. It is shown that the proposed approach is not sensitive to nonlinear behavior of TCSCs and it is capable of detecting all types of faults, including three-phase ones, during power swing accurately. In addition, due to low computational complexity, the proposed method provides significantly high detection speed.

Single-end current-based algorithm for fault location in series capacitor compensated transmission lines

The performance of protection functions in the series capacitor compensated transmission lines (SCCTLs) is affected by the capacitors protection system operating. One of these protection functions is the fault locator. This paper presents a highly accurate fault location algorithm in the SCCTLs for the single line to ground (SLG) faults, as the most common type of faults in transmission systems. The proposed algorithm identifies the fault location using the current phasors measured at only one side the faulty line, which makes it a low-cost and high reliable one. Therefore, the proposed algorithm can be easily implemented on numerical relays as it does not require communication channel to acquire remote data. In the proposed algorithm, after fault signal processing, the initial fault locations are obtained through moving the sampling window. Finally the exact fault location is calculated using the initial fault locations data and an outlier data removal technique. In order to evaluate the proposed algorithm, a test system is simulated in DIgSILENT software and processing process is implemented in MATLAB software. The obtained results show high accuracy and efficiency of the proposed method.

A DMWT-Based Relaying Scheme for the Recognition of Shunt Faults Including Ground Faults in a Two-Terminal Series Capacitor Compensated Transmission Line

A DMWT-Based Relaying Scheme for the Recognition of Shunt Faults Including Ground Faults in a Two-Terminal Series Capacitor Compensated Transmission Line

Modal Control Design of Damping Controllers for Thyristor-Controlled Series Capacitor to Stabilize Common-Mode Torsional Oscillations of a Series-Capacitor Compensated Power System

This paper proposes a unified approach based on modal control theory to design damping controllers of a thyristor-controlled series capacitor (TCSC) for stabilizing the inherent common-mode torsional interactions occurred in a series-capacitor compensated power system. The studied power system includes two nonidentical turbine-generator sets connected to an infinite bus through a common series-capacitor compensated transmission line. The employed TCSC is properly connected in parallel with a part of the series-capacitor bank of the compensated transmission line. The damping controllers of the TCSC employ the speed deviations of both turbine-generator sets as input signals to stabilize unstable torsional modes of the studied system by increasing the damping of these modes. Both frequency-domain approach based on eigenvalue analysis and time-domain scheme based on nonlinear-model simulations under different disturbance conditions are systematically performed. It can be concluded from the simulated results that the employed TCSC joined with the damping controllers designed by using modal control theory can effectively stabilize the common-mode torsional oscillations of the studied series-capacitor compensated system.

Combined DFT and Fuzzy Based Faulty Phase Selection and Classification in a Series Compensated Transmission Line

The conventional distance protection scheme malfunctions sometimes in case of a fixed series capacitor compensated transmission line due to the change in relaying impedance of the protected line during faulty conditions. In order to mitigate this problem, a combined discrete Fourier transform and fuzzy (CDFTF) based algorithm has been proposed in this paper. This method has been tested on a 400 km, 735 kV series compensated transmission line network and WSCC 3-machine 9-bus system for all fault types using MATLAB/Simulink and PSCAD platforms, respectively. A fixed series capacitor is located at the middle of the protected line. The fundamental components of phase currents, phase voltages, and zero-sequence current are fed as inputs to the proposed scheme. The fault detection, faulty phase selection, and fault classification are achieved within 1/2–1 cycle of power frequency. The proposed CDFTF-based scheme is less complex and is better than other data mining techniques which require huge training and testing time. Test results corroborate the proposed scheme reliability with wide variations in fault location, fault resistance, fault inception angle, evolving faults, compensation level, and heavy load interconnection. The results discussed in this work indicate that the proposed technique is resilient to wide variations in fault and system conditions.

Wavelet Transform Approach for Fault Detection of Three Phase Transmission Line Compensated with Series Capacitor

This paper proposes fault detection technique for the protection of series capacitor compensated three phase transmission line using wavelet transform. Three phase series capacitor compensated transmission line is modeled and the proposed fault detection technique has been developed and tested using Simscape Power Systems toolbox of MATLAB software. Proposed scheme is tested by variations of parameters like fault type, fault resistance, ground resistance, fault location and fault inception time. The test results confirmed successful detection of fault.

A Contemporary Discrete Wavelet Transform Based Twelve Phase Series Capacitor Compensated Transmission Line Protection

A Contemporary Discrete Wavelet Transform Based Twelve Phase Series Capacitor Compensated Transmission Line Protection

Impedance-Based Fault Location Algorithm for Ground Faults in Series-Capacitor-Compensated Transmission Lines

Locating a fault in a series-capacitor-compensated transmission line (SCCTL) is a challenging task due to the action of a metal-oxide varistor a nonlinear element present as a part of the protection system of the series capacitor. In this paper, an accurate fault-location algorithm that uses synchronized measurements from both ends of the SCCTL is presented which provides fault-location results without using the model of MOV or natural fault loop for single-phase-to-ground, and double-phase-to-ground faults. Another salient feature of the proposed technique is that the subroutines for locating faults in different sections transmission line yield almost identical fault-location results regardless of which section the transmission line is faulted. The proposed technique could also be extended to the double-circuit transmission lines. First, the proposed technique is introduced and its features are elaborated through detailed mathematical analysis. Thereafter, a 500- $\text{kV}$ system with an SCCTL is designed in PSCAD, while the fault-location algorithm is modeled in MATLAB. The proposed algorithm is tested through simulations covering various fault scenarios in an SCCTL. For performance evaluation, the comparative analysis of the proposed technique with a well-known existing technique is performed in this paper.

An artificial neural network-based solution to locate the multilocation faults in double circuit series capacitor compensated transmission lines

During thunder storms, multilocation faults may occur at different locations in different phases of the 3 phase transmission lines at same or different time. This paper proposes an artificial neural network-based solution to locate the multilocation faults in double-circuit series capacitor compensated transmission lines (SCCTLs), unlike previous works that only locate the fault at single location. Although various fault location schemes have been proposed for normal shunt faults occurring at 1 location in SCCTL, nevertheless, finding the locations of multilocation faults in double circuit SCCTL has not been addressed so far. The proposed artificial neural network-based method determines the location of multilocation faults by using current and voltage signals of 1 end of line only, thus avoiding the need of communication link. The signals are preprocessed by using discrete wavelet transform. A comparative study of various neural networks such as feed-forward back-propagation network with Levenberg-Marquardt algorithm, Elman recurrent neural network with gradient descent algorithm, radial basis function neural network has been carried out. The proposed method is not affected by variation in different parameters viz. fault type, fault location, fault inception angle, fault resistance, degree of series compensation, and location of series capacitor. The key advantage of the method is that it correctly estimates the locations of multilocation faults as well as single-location fault, thus making it more reliable and accurate as compared to conventional fault location schemes.

A Novel Fault Classification Scheme for Series Capacitor Compensated Transmission Line Based on Bagged Tree Ensemble Classifier

This paper presents a novel intelligent fault classification scheme for fixed series capacitor compensated transmission line. The singular value decomposition principle is applied along with the fast discrete orthonormal S-transform (FDOST) and bagged tree ensemble classifier for classification of faults under different scenarios. Classification input features are extracted from 1/2 cycle post-fault current data through the FDOST. The feasibility of the proposed relaying scheme is tested on a modified WSCC 3-machine 9-bus system under different fault conditions using PSCAD/EMTDC, and the results indicate the proposed scheme to be fast and accurate. The robustness of the proposed scheme to noise and current transformer saturation is also established. The obtained results under different fault scenarios confirm the efficacy of the proposed scheme.

A non-unit protection scheme for double circuit series capacitor compensated transmission lines

This paper presents a non-unit protection scheme for series capacitor compensated transmission lines (SCCTL) using discrete wavelet transform and k-nearest neighbor (k-NN) algorithm. All the protective relaying functions such as fault detection, fault classification, faulty phase identification and fault location estimation have been considered in this work. Such a comprehensive work providing all protective relaying functions for protection of double circuit SCCTL utilizing k-NN has not been reported so far. The signal processing and feature extraction are done using discrete wavelet transform due to its capability to differentiate between high and low frequency transient components. For fault detection and classification, only approximate wavelet coefficient of current signal up to level 1 has been used; while for k-NN location estimation, both voltage and current signals of the two circuits are decomposed up to level 3 have been used. Finally, the standard deviation of one cycle pre-fault and one cycle post-fault samples of the approximate wavelet coefficients are calculated to form the feature vector for the k-NN-based algorithm. The performance of the proposed technique is evaluated for large number of fault events with variation in fault type including inter-circuit faults, fault inception angle, fault location and fault resistance. The change in position of series capacitor and different degree of compensation has been discussed. The accuracy of the proposed k-NN-based fault detection and classification module is 100% for all the tested fault cases with a decision period of less than half cycle. The k-NN-based fault location scheme estimates the location of fault with ≤1% error for most of the tested fault cases, which is an exceptional attribute of the proposed scheme as compared with 10–15% error of conventional distance relaying scheme.

Supplementary Impedance-Based Fault-Location Algorithm for Series-Compensated Lines

This paper presents a new impedance-based supplementary fault-location algorithm for series capacitor-compensated transmission lines (SCCTLs), which improves the accuracy of the existing fault-location algorithms. The proposed algorithm utilizes the fact that the metal–oxide varistor (MOV) may become bypassed in faulted or all phases before the interruption of fault for certain fault scenarios. The removal of the nonlinear element, that is, MOV from the fault loop enables the proposed algorithm to provide more accurate fault-location results compared to the most advanced impedance-based technique. Another major advantage of the proposed algorithm is that the dedicated subroutines are not required for the location of a fault in a particular section of the transmission line. The proposed fault-location algorithm is rigorously tested for various fault scenarios in the 500-kV SCCTL simulated in PSCAD. The performance of the proposed algorithm is compared to a well-known existing impedance-based fault-location algorithm for SCCTLs to illustrate higher accuracy and improved sensitivity of the proposed technique.

Improved fault location algorithm for multi‐location faults, transforming faults and shunt faults in thyristor controlled series capacitor compensated transmission line

Fault location estimation in series compensated transmission lines is quite difficult because a non-linear current dependent circuit appears between the substation and fault point. In particular, the faults which occur at different locations at the same time in different phases known as multi-location faults has not been addressed by researchers. Other types of fault that may occur in transmission lines are transforming faults where one type of fault transforms to another type fault after some time. In this study, a fault location estimation scheme using artificial neural network (ANN) is presented for multi-location faults, transforming faults as well as for commonly occurring shunt faults in thyristor controlled series capacitor (TCSC) compensated transmission line. DB-4 wavelet is used for pre-processing of the three-phase current and voltage signals. The shunt capacitance of the line is considered based on distributed parameter line model. Feasibility of the ANN-based fault location algorithm is tested under a wide variation of parameters, such as fault type, location, fault resistance and fault inception angle. Fault location errors are within 0.001–1% range.

Enhanced Phasor Estimation Technique for Fault Location in Series-Compensated Lines

Accurate phasor-based fault location in series capacitor-compensated transmission lines is a challenging task due to the presence of subsynchronous frequency components in the measured voltage and current signals. In this letter, an enhanced technique is proposed based on Prony analysis and discrete Fourier transform to accurately estimate voltage and current phasors for the purpose of offline fault location. A comprehensive simulation and fault-location analysis is performed using PSCAD and Matlab to establish the successful application of the proposed technique to the fault location.

Real time digital simulator implementation of data-mining-based integrated impedance relay for compensated lines

Summary The paper presents integrated impedance-based intelligent relaying for thyristor-controlled series capacitor-compensated transmission lines on Real Time Digital Simulator platform. Integrated impedance is defined as the ratio of sum of the voltage phasors across two ends of the transmission line to the sum of the current phasors through two ends of the same transmission line. The imaginary part of integrated impedance of the transmission line is used as input to a data-mining model known as decision tree that determines whether the fault is within the protected zone or not. Critical issues such as power swing and fault during power swing are also included during validation of the relay on Real time digital simulator platform. The test results obtained indicate that the proposed integrated impedance-based intelligent relaying is highly dependable and secure for protection of extra high voltage transmission lines including thyristor-controlled series capacitor. Copyright © 2014 John Wiley & Sons, Ltd.

Stochastic evaluation of transient recovery voltages across circuit breakers of series capacitor compensated transmission lines

This paper presents a Monte Carlo based approach to evaluate the maximum transient recovery voltages induced across circuit breaker poles during clearing a fault on a series capacitor compensated transmission line. In this context, investigations have been conducted on a sample power system model taking into consideration the uncertainty of several factors associated with the practical operation of a power system. A risk index that reflects the likelihood that the transient recovery voltage induced across circuit breaker poles exceeds its design value is also presented.

Reducing dead time for single-phase auto-reclosing on a series-capacitor compensated transmission line

This paper presents a single-phase auto-reclosing study of a 500 kV Vietnamese transmission line. The success of the single-phase auto-reclosing depends on the extinction of the secondary arc. Therefore, the influences of several factors such as shunt and neutral reactors, faulted phase and location, capacitive and inductive coupling and series capacitor discharge on the extinction of secondary arc are investigated. This paper presents the influence of single-phase auto-reclosing on the transient stability of the Vietnam system. A new method in order to reduce the dead time for single-phase auto-reclosing is proposed.

A bifurcation analysis of subsynchronous oscillations in power systems

A bifurcation analysis is used to investigate the complex dynamics of a heavily loaded turbine-generator system connected to an infinite busbar through a series capacitor-compensated transmission line. It reveals the existence of self-excited subsynchronous torsional oscillations of a 5-mass rotor, which may eventually lead to the destruction of the shaft or the loss of synchronism of the generator. Specifically, we show that, as the capacitor-compensation value increases and reaches a critical value, called supercritical Hopf bifurcation, the system around the operating point undergoes small single-period oscillations with constant amplitude. This in turn results in a small limit-cycle attractor. As the compensation level increases further, the amplitude of oscillation grows until a secondary Hopf bifurcation is reached. There, the oscillations characterize themselves by two incommensurate periods and bounded amplitudes, signifying the transformation of the limit cycle into two-period quasiperiodic motion called a two-torus attractor. When the capacitor-compensation level passes a third critical value, the amplitude of oscillations becomes unbounded following the destruction of the two-torus attractor and its basin of attraction in a so-called bluesky catastrophe. Interestingly, this scenario repeats itself in the vicinity of three supercritical Hopf bifurcations. The bifurcation analysis is validated with numerical solutions of the differential equations that govern the power system.