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.

Bracing for the geomagnetic storms

Abstract: As solar activity moves toward an 11 year peak, utility engineers are girding for the effects of massive magnetic disturbances. The nature of the geomagnetic disturbances is examined. The way in which geomagnetically induced current (GIC) affects power systems is explained. Virtually all power equipment, operation, and protection problems due to GIC are traceable to two direct effects: the half-cycle saturation of power transformers and the half-cycle saturation of the current transformers used with protective relay systems. Of the two, the former, with its numerous secondary effects, has been the more serious. As an example, a blackout due to solar disturbances, which happened to the Hydro-Quebec system in Mark 1989, is described. The factors that make power networks especially vulnerable today and the difficulty of predicting episodes are considered. >

Behaviour of grounding systems excited by high impulse currents: the model and its validation

Abstract: The behaviour of grounding systems excited by high impulse currents (such as lightning strokes or phase to ground faults) considerably differs from that at low-frequency and at low-current: inductive behaviour can become more and more important with respect to resistive behaviour and, in addition, these currents can generate soil breakdown (which makes the impulse response typically nonlinear). Many experimental tests confirm these aspects. In order to obtain a correct design of electrical systems, with respect to the protection of installations against anomalous events, it is fundamental to predict the impulse characteristics of grounding systems. An efficient solution to this problem may be obtained by a mathematical model based on a circuit approach. The development of this model (which is able to simulate complex grounding systems when nonlinear ionization phenomena take place) is described in this paper. The model has been validated by comparing the numerical results both with experimental tests and with the simulations executed by various approaches.

A Fast and Accurate Synchronization Technique for Extraction of Symmetrical Components

Abstract: This paper introduces an approach for the real-time extraction of the frequency, phase angle, and symmetrical components of the grid signal, which is of great importance for many applications in power systems such as power quality and protection The proposed method is based on the concept of the adaptive notch filter that provides a fast and accurate estimation of the symmetrical components in the presence of frequency and amplitude variations In addition, the system offers a high degree of immunity and insensitivity to power system disturbances, harmonics, and other types of pollutions that exist in the grid signal The simplicity of the structure makes the method suitable for both software and hardware implementations Moreover, this very simple and very powerful tool can be used as a synchronization technique, which further simplifies the control issues currently challenging the integration of distributed energy technologies into the electricity grid Mathematical derivations are presented to describe the principles of operation, and experimental results confirm the validity of the analytical work

A Traveling-Wave-Based Protection Technique Using Wavelet/PCA Analysis

Abstract: This paper proposes a powerful high-speed traveling-wave-based technique for the protection of power transmission lines. The proposed technique uses principal component analysis to identify the dominant pattern of the signals preprocessed by wavelet transform. The proposed protection algorithm presents a discriminating method based on the polarity, magnitude, and time interval between the detected traveling waves at the relay location. A supplemental algorithm consisting of a high-set overcurrent relay as well as an impedance-based relay is also proposed. This is done to overcome the well-known shortcomings of traveling-wave-based protection techniques for the detection of very close-in faults and single-phase-to-ground faults occurring at small voltage magnitudes. The proposed technique is evaluated for the protection of a two-terminal transmission line. Extensive simulation studies using PSCAD/EMTDC software indicate that the proposed approach is reliable for rapid and correct identification of various fault cases. It identifies most of the internal faults very rapidly in less than 2 ms. In addition, the proposed technique presents high noise immunity.

Graphical Methods for Defense Against False-Data Injection Attacks on Power System State Estimation

Abstract: The normal operation of power system relies on accurate state estimation that faithfully reflects the physical aspects of the electrical power grids. However, recent research shows that carefully synthesized false-data injection attacks can bypass the security system and introduce arbitrary errors to state estimates. In this paper, we use graphical methods to study defending mechanisms against false-data injection attacks on power system state estimation. By securing carefully selected meter measurements, no false data injection attack can be launched to compromise any set of state variables. We characterize the optimal protection problem, which protects the state variables with minimum number of measurements, as a variant Steiner tree problem in a graph. Based on the graphical characterization, we propose both exact and reduced-complexity approximation algorithms. In particular, we show that the proposed tree-pruning based approximation algorithm significantly reduces computational complexity, while yielding negligible performance degradation compared with the optimal algorithms. The advantageous performance of the proposed defending mechanisms is verified in IEEE standard power system testcases.