Arturo S. Bretas

Distribution Systems High-Impedance Fault Location: A Parameter Estimation Approach

High-impedance fault location has always been a challenge for protection engineering. On the other hand, if this task is successfully realized, maintenance action could be performed in order to avoid potential injuries. For an effective protection scheme, high-impedance fault location should be performed, but a lack of research on this area is noted. This paper proposes a new analytical formulation for high-impedance fault location in power systems. The approach is developed in the time domain, considering a high-impedance fault model consisting of two antiparallel diodes. Using this model, the fault distance and parameters are estimated as a minimization problem. First, a linear least square-based estimator is applied without consideration of line capacitance. Second, a steepest descent-based estimator is proposed in order to consider the line capacitance. Studies were carried out with the IEEE 13 bus modeled in the Alternate Transients Program. Encouraging test results are found indicating the methods potential for real-life applications.

Bad data analysis in distribution state estimation considering load models

This paper presents a study of bad data analysis in distribution state estimation considering pseudo-measurements given by load models. The bad data analysis is performed using the residual analysis, based on chi-square and normalized residual tests, and the geometrical approach, based on the use of composed measurement error and composed normalized error. This is the first work that assesses the geometrical analysis for distribution systems. A numerical study is conducted considering a 69-bus distribution system with advanced metering infrastructure. The results show a potential improvement using the geometrical analysis.

A Distributed Control Approach for Enhancing Smart Grid Transient Stability and Resilience

Increasing deployment of information technologies and low-inertia renewable energy sources into smart grid fuel the uncertainties and reveal security and transient stability problems. Enhancing the stability margins of smart grids despite the cyber and physical disturbances emerges the need for cyber-aware robust controller design. Therefore, a distributed nonlinear robust controller is proposed to improve the transient stability margins of synchronous generators (SG) in the presence of excessive communication delay and cyber-physical disturbances. The proposed controller uses phasor measurement units to receive real-time measurements and actuates distributed storage systems to inject or absorb power in order to accelerate stabilization of frequency oscillations of SG following a disturbance. The communication dependency exposes time delay and cyber-security issues since latency is inherent and can be excessive during an attack such as denial of service. In addition, uncertainties in measurements challenge the stabilization process. Hence, the proposed controller is designed for robustness to delay and additive disturbances. A novel time delay compensation technique is developed to inject delay-free control signal into the closed-loop system. To guarantee that all tracking error signals are globally uniformly ultimately bounded, novel Lyapunov–Krasovskii functionals are used in the Lyapunov-based stability analysis. The simulation results validate the feasibility of the proposed control framework and robustness under cyber-physical practical limitations.

Nontechnical Losses detection: A Discrete Cosine Transform and Optimum-Path Forest based approach

This paper presents a Discrete Cosine Transform (DCT) and Optimum-Path Forest (OPF) based approach for Nontechnical Losses (NTL) detection. NTL decrease the economic efficiency of distribution utilities, which harms the entire society since energy prices increase as a consequence. Pattern Recognition based approaches have been applied to identify these losses so that the problems related to NTL may be corrected through on-site inspections. One of the main characteristics of NTL is the decrease in the customers measured monthly-consumed energy, caused by frauds or failure of the energy meter, which is called “consumption step”. This record of kWh consumption can be treated as a time-series and then benefit from the knowledge available in this area. In this paper DCT and OPF were used as a means of implementing automatic feature extraction. The pro-posed method was compared with an OPF based approach previously proposed by the authors. Test results show that feature extraction using DCT can provide a more compact and efficient way of representing data, improving the performance of previously developed methods by the authors.

Smart distribution power losses estimation: A hybrid state estimation approach

This paper presents a method to estimate and identify technical and non-technical power losses in distribution systems based in a hybrid state estimation approach. The proposed method is divided in two steps. In the first step, non-technical power losses are detected, identified and corrected using a geometrical based state estimator technique. In the second step, a pattern recognition technique is applied on consumers aiming intelligent weight of load measurements. On this second step, power losses are estimated with the updated weight matrix. The proposed approach was numerically analyzed in a 69-bus distribution system considering an advanced metering infrastructure. The results show a potential improvement of the proposed method when compared with the state-of-the-art residual based state estimator approach.

Discussion on “A New Framework for Detection and Identification of Network Parameter Errors”

The authors present an interesting method on Normalized Lagrange Multiplier test for network parameter errors identification. The authors state that validation has so far been solely based on extensive simulations. They also state that the paper presents a new framework by which: (1) the normalized Lagrange multiplier test is re-formulated from the perspective of hypothesis testing, enabling proper handling of missing bad parameter cases; (2) formal proofs are given for the combined utilization of normalized Lagrange multiplier test and normalized residual test for simultaneous handling of measurement and parameter errors; and (3) the concepts of detectability and identifiability for measurement errors are extended to parameter errors, and a systematic approach for identifying critical parameters and critical k-tuples is provided. However, in the paper section II, they present in the problem formulation: \begin{equation*} z=h\left ({x,p_{e}}\right )+e \tag{1}\end{equation*} where

Comparative performance of impulsive grounding systems embedded in concrete: An experiment in reduced scale

z

Fault location in Distribution Network with Inverter-Interfaced Distributed Energy Resources in limiting current

is the measurement vector,

Performance assessment of an optimal load control algorithm for providing contingency service

x

A distributed approach for DG integration and power quality management in railway power systems

is the state vector,