C. P. Gupta

Probabilistic assessment of financial losses due to interruptions and voltage sags - part II: practical implementation

The second part of this paper presents a practical implementation and application of the methodology for the stochastic assessment of the annual financial losses due to interruptions and voltage sags discussed in the first part of this paper. The costs of interruptions and voltage sags are determined separately and then combined in order to estimate the total financial losses in the network. The methodology is illustrated on a generic realistic distribution network with all relevant network components modeled appropriately. Finally, different network topologies are compared taking into account total financial losses in the network. It is shown that the inclusion of the financial losses due to voltage sags that may account for up to about 20% of the interruption costs may alter the network topology ranking.

Comprehensive Adaptive Distance Relaying Scheme for Parallel Transmission Lines

Reach accuracy of a distance relay is adversely affected by prefault system conditions, ground fault resistance, shunt capacitance, and mutual coupling of parallel lines. This paper presents a comprehensive adaptive relaying scheme for stand-alone distance protection of parallel transmission lines under a single-line-to-ground fault condition taking into account all of these factors. The proposed adaptive scheme is based on the back-propagation neural network used for training and adaptation. The relay acts as a stand-alone relay, which does not require a separate communication channel for real-time data transmission during faults. The simulation results show significant improvement in the relay selectivity.

Discrete wavelet transform and probabilistic neural network based algorithm for classification of fault on transmission systems

This paper presents the development of an algorithm based on discrete wavelet transform (DWT) and probabilistic neural network (PNN) for classifying the power system faults. The proposed technique consists of a preprocessing unit based on discrete wavelet transform in combination with PNN. The DWT acts as extractor of distinctive features in the input current signal, which are collected at source end. The information is then fed into PNN for classifying the faults. It can be used for off-line process using the data stored in the digital recording apparatus. Extensive simulation studies carried out using MATLAB show that the proposed algorithm not only provides an accepted degree of accuracy in fault classification under different fault conditions but it is also reliable, fast and computationally efficient tool.

A particle swarm optimisation based technique of harmonic elimination and voltage control in pulse-width modulated inverters

A particle swarm optimisation (PSO) based method is presented for selective harmonics elimination (SHE) solution in pulse-width modulated (PWM). PSO is used to determine the switching pulses by solving the non-linear equations formed with the Fourier analysis of the output waveform which enables the control of the fundamental component. The application of the proposed method to single phase and three phase inverter is demonstrated with respect to harmonic distortion by eliminating the unwanted lower harmonic component up to 19th order. The selected performance features are validated by relevant waveforms, which are obtained by simulation of different examples with the use of MATLAB software, which shows the better perform of the proposed method.

Fault Classification Scheme Based on the Adaptive Resonance Theory Neural Network for Protection of Transmission Lines

Abstract This article presents a new approach to classify various types of power system faults using wavelet transforms and the adaptive resonance theory. The key idea underlying the approach is to decompose a given disturbance signal into other signals, which represents a smoothed and detailed version of the original signal. The proposed technique consists of a preprocessing unit based on discrete wavelet transform in combination with adaptive resonance theory. Through wavelet analysis, faults are decomposed into a series of wavelet components, each of which is a time-domain signal that covers a specific octave frequency band. The parameters selected for fault classification are the detailed coefficients of all phase current signals that are collected only at the sending end of a transmission line. The information is then fed into adaptive resonance theory for classifying the faults. The study is performed on a sample power system network. Extensive simulation studies carried out using MATLAB (http://www.mathworks.com) shows that the proposed algorithm not only provides an accepted degree of accuracy in fault classification under different fault conditions, but it is also reliable, fast, and computationally efficient tool.

Modified PSO and wavelet transform-based fault classification on transmission systems

This paper presents the development of an algorithm based on discrete wavelet transform (DWT) and particle swarm optimisation (PSO) for classifying the power system faults. The proposed technique consists of a preprocessing unit based on DWT in combination with PSO. The DWT acts as extractor of distinctive features in the input current signal, which are collected at source end. The information is then fed into PSO for classifying the faults. It can also be used for offline processing of data stored in digital recorders. Extensive simulation studies carried out using MATLAB show that the proposed algorithm not only provides an acceptable degree of accuracy in fault classification of 400 kV transmission system under various fault conditions when compared to the results obtained using probabilistic neural network (PNN) method, but is reliable, fast and computationally efficient too.

Area of vulnerability for prediction of voltage sags by an analytical method in indian distribution systems

This paper proposes an analytical method for voltage sags prediction in distribution systems. The method is based on the ZBus matrix of the distribution network, from which one can immediately build a second matrix that can be called the ldquovoltage sags matrixrdquo as it compactly provides valuable information about voltage sags throughout the distribution systems. The paper also describes graphical ways to present the effect of a fault on the distribution systems and the area where faults cause severe sags on a given load: affected area and area of vulnerability respectively. An Indian distribution system is used to illustrate the ideas.

Minimization of Financial Losses due to Voltage Sag in an Indian Distribution System using D-STATCOM

Voltage sag can cause considerable financial damage in an industry containing sensitive equipment. Many solutions exist to minimize financial losses due to voltage sag, varying from modification within the process itself to restructuring the supplying grid. In many cases the only possibility to minimize the financial losses is to install mitigation devices between the grid and the sensitive process such as power electronics devices Uninterruptible Power Supply (UPS). However, protecting the entire process by a dynamic or static UPS often turns out to be too expensive. This paper presents the minimization of financial losses due to voltage sag produced by balanced and unbalanced short circuit that occur at distribution system bus and along the transmission line using system impedance matrix (Z Bus) which incorporates D-STATCOM. The overall financial losses due to voltage sag could significantly change depending on the location of D-STATCOM used. In order to have an assessment of financial losses in real distribution systems, the classical static fault calculation should be amended to incorporate the effect of installation of these devices on financial losses. The cost-benefit analyses of inducting D-STATCOM for mitigating the effects of voltage sags have also been performed.Case studies based on a real Indian distribution system are used to illustrate the modeling method and the effectiveness of these devices in voltage sag mitigation.

Assessment of Financial Losses due to Voltage Sags in an Indian Distribution System

This paper presents a practical implementation of stochastic assessment of the annual financial losses due to voltage sags taking into account the uncertainties involved with the sensitivity and interconnection of equipments participating in an individual process, customer types and location of the process in the system network. The methodology is applied to the distribution system of Haridwar district of Uttarakhand state, India.

The Method of Fault Position for Assessment of Voltage Sags in Distribution Systems

This paper focuses on the method of fault position for stochastic prediction of balanced and unbalanced voltage sags in a distribution system. The theoretical background about the short circuit analysis is presented and residual phase voltage equations for balanced and unbalanced fault are derived. Thereafter area of vulnerability based on the assessment of voltage sags have been presented for an Indian distribution system.