Power-system protection

About: Power-system protection is a research topic. Over the lifetime, 6353 publications have been published within this topic receiving 117961 citations.

Series compensated line protection enhancement by modified pilot relaying schemes

Abstract: In this paper, a comprehensive analysis of the impact of series capacitor on the performance of communication-aided distance protection schemes of transmission lines is presented. It is shown that not only the series capacitor and its overvoltage protection affect the distance protection of its line, but also the adjacent lines would experience protection problems. Mitigation of this problem is proposed by using new communication-aided schemes. The proposed schemes use the information available at the substation to inhibit relay malfunctions. The performance of the techniques is studied for different series capacitor locations in the transmission line. Real Time Digital Simulator (RTDS) and four sophisticated commercial relays are used for testing. The results verify the impact of series capacitor on the conventional communication-aided schemes and also the effectiveness of the proposed methods

Transmission line faults detection, classification and location using artificial neural network

Abstract: Transmission lines, among the other electrical power system components, suffer from unexpected failures due to various random causes. These failures interrupt the reliability of the operation of the power system. When unpredicted faults occur protective systems are required to prevent the propagation of these faults and safeguard the system against the abnormal operation resulting from them. The functions of these protective systems are to detect and classify faults as well as to determine the location of the faulty line as in the voltage and/or current line magnitudes. Then after the protective relay sends a trip signal to a circuit breaker(s) in order to disconnect (isolate) the faulty line.The features of neural networks, such as their ability to learn, generalize and parallel processing, among others, have made their applications for many systems ideal. The use of neural networks as pattern classifiers is among their most common and powerful applications. This paper presents the use of back-propagation (BP) neural network architecture as an alternative method for fault detection, classification and isolation in a transmission line system. The main goal is the implementation of complete scheme for distance protection of a transmission line system. In order to perform this, the distance protection task is subdivided into different neural networks for fault detection, fault identification (classification) as well as fault location in different zones. Three common faults were discussed; single phase to ground faults, double phase faults and double phase to ground faults. The result provides a reliable and an attractive alternative approach for the development of a protection relaying system for the power transmission systems.

Multi neural network based fault area estimation for high speed protective relaying

Abstract: The aim of this paper is to present a new approach to fault area estimation for high-speed relaying using feedforward neural networks. The suggested framework makes use of neurocomputing technology and pattern-recognition concepts. In contrast to conventional algorithms, our neural fault area estimator (NFAE) determines the fault area directly. This approach leads to very short propagation times and reliable classification results. Important attributes of artificial neural networks (ANNs) are their ability to learn nonlinear functions and their large input error tolerance. The obtained results indicate that these characteristics still result in reliable behaviour even if nonideal (real-world) effects pertain. A comparison of classification quality with conventional algorithms by simulating certain faults on a parallel transmission line shows the approaches advanced capability for protective relaying.

Multi-agents based protection for distributed generation systems

Abstract: As a result of deregulation, distributed generation (DG) systems with distributed generators installed in the middle or low voltage networks become popular in distribution systems. Traditional protections developed in radial systems are difficult in coordination and in protecting against high impedance fault (HIF), sometimes it may cause nuisance tripping in the DG systems. A decentralized multi-agent based protection with capability of HIF detection, fault location and load shedding for the DG systems is proposed in the paper. Digital relay is designed as a relay agent which is capable of searching for information from other relay agents, interacting with other relay agents and performing tasks of protection with autonomy and cooperating. The agent based protection scheme is also presented. EMTP simulation results show that the proposed agent based protection scheme can remove the influence of load switching operations, protect against HIF, electric shock. The prototype of relay agent is developed, the research is now in progress on testing the prototype in dynamic power system.

A Hybrid Method for Power System Frequency Estimation

Abstract: Power system frequency is a critical parameter of voltage and current measurements for many applications, such as power quality, monitoring, and protection. This paper presents a hybrid approach for frequency estimation based on Taylor series expansion and Fourier algorithm. The method is derived using a dynamic signal model with varying parameters. The changing envelope of a power signal within an observation data window is approximated with a second-order Taylor series. A Fourier algorithm-based method is proposed to compute the parameters of such signal model. The algorithm using the linear model approach aimed at alleviating the computational complexity is also presented. The comparison of the performance under various conditions between the two approaches is conducted. Inheriting from the use of Fourier algorithm, this hybrid algorithm is immune to power system harmonics. It achieves excellent performance for signals with dynamic variations. The performance is investigated and compared with other techniques through simulations for various scenarios observed in real power systems. Experimental studies demonstrate the advantages of the proposed algorithm.