Euler C. T. Macedo

Wavelet transform processing applied to partial discharge evaluation

Partial Discharge (PD) is characterized by high frequency current pulses that occur in high voltage (HV) electrical equipments originated from gas ionization process when damaged insulation is submitted to high values of electric field [1]. PD monitoring is a useful method of assessing the aging degree of the insulation, manufacturing defects or chemical/mechanical damage. Many sources of noise (e.g. radio transmissions, commutator noise from rotating machines, power electronics switching circuits, corona discharge, etc.) can directly affect the PD estimation. Among the many mathematical techniques that can be applied to de-noise PD signals, the wavelet transform is one of the most powerful. It can simultaneously supply information about the pulse occurrence, time and pulse spectrum, and also de-noise in-field measured PD signals. In this paper is described the application of wavelet transform in the suppression of the main types of noise that can affect the observation and analysis of PD signals in high voltage apparatus. In addition, is presented a study that indicates the appropriated mother-wavelet for this application based on the cross-correlation factor.

A system for dynamic contact resistance with Arduino platform on MV and HV circuit breaker

The paper describes the use of Arduino platform in developing a solution for measuring and processing the dynamic contact resistance curve in high voltage circuit breakers (CB). The system is capable of supply a current test of 300 A between the breaker contacts. The current signal circuit is achieved by the combination of a voltage source based on a stationary battery 12 V / 220 Ah and current limiting resistor from 0.4 to 1.2 Ω. The dynamic resistance measurement (DRM) signals are acquired by an auxiliary circuit which communicates with two analog channels Arduino platform. The voltage and current signals are acquired and stored on the Arduino microcontroller and in the sequence are sent to personal computer to be evaluated by a Matlab© based routine used for digital filtering of noise and generate the dynamic contact resistance curve. The Arduino platform used in this research was the Arduino Mega, with 6 analog input pin, with a 16 bits A/D converter.

ZnO Surge Arresters Diagnosis Using Microcontroller

Surge arresters are equipments used for the power electrical systems protection. They limit the voltage level during the occurrence of switching and atmospheric surges. A surge arrester failure can cause the equipments insulation breakdown or flashover, or even the surge arrester explosion. To avoid this problem, the maintenance of these equipments is made by means of regular monitoring. Measurement of the resistive leakage current and analysis of its harmonic components is one of the most used techniques to evaluate the degradation level of metal oxide surge arresters. In this paper is presented a new measurement technique for the resistive component of leakage current based on the orthogonal position between this component and the capacitive component. The technique is accomplished by means of inductive current sensors based on nanocrystalline alloys and a PIC microcontroller to provide the measurement of the first, third and fifth harmonic components of the resistive leakage current in the arrester.

Monitoring and Diagnosis of ZnO Arresters

Surge arresters are part of the protection system of electrical substations and transmission and distribution networks. They avoid damages in equipments of main importance for the electric system, such as power transformers, not allowing them to be reached by overvoltages. An arrester presenting any kind of failure may not actuate in a satisfactory way during the occurrence of an electric surge. As a consequence, it will present an overheating which can lead to its complete degradation and exposing the system that should be protected and bringing risk to those who are working nearby [1]. In order to avoid this kind of problem, several monitoring techniques are used. The measurement of leakage current and the thermal analysis are the most used of these techniques. A work being developed in the High Voltage Laboratory of the Universidade Federal de Campina Grande together with the Companhia Hidreletrica do Sao Francisco has the main purpose of developing a technique to be used for arrester monitoring by means of continuous analysis of its leakage current and variations on its thermal patterns, resulting in a useful tool for the diagnosis and preview of failures in ZnO arresters.

Lead acid battery SoC estimation based on extended Kalman Filter method considering different temperature conditions

State of Charge (SoC) is the most important parameter to be estimated on a Battery Management System (BMS). Improper SoC management can cause faster battery degradation, reduce its operational lifetime and, on extreme cases of overcharge, it may lead to an explosion. In addition, batteries are complex electrochemical systems, and both the electrical components and chemical reactions vary significantly with changes in temperature. In this paper, it is presented the effect of the temperature on the Lead Acid battery SoC estimation. The data collection was performed varying the battery temperature, under a range of 10oC to 70oC. To determine the model parameters from the used battery, several data acquisition was performed. To obtain the SoC estimation it was implemented the Extended Kalman Filter that provide satisfactory results. The simulated results were obtained using the MATLAB environment. To verify the effectiveness and the performance of the implemented Kalman Filter it was applied the EKF for estimate the SoC of a Lead Acid battery described in the Introduction Section. It is important to realize that is a comparative study and the only evaluation comparison with the SoC estimation that we can do uses the Open Circuit Voltage (OCV).

A thermoelectric module thermal-cycling testing platform with automated measurement capabilities

Thermoelectric Modules (TEM) are used in areas such as precision temperature control applications, cooling system, energy harvesting, etc. The fully characterization of TEM is very important, mainly with respect to its degradation. In order to evaluate degradation, thermal cycling application is one of the most used methods. In this work it is described a complete thermal-cycling testing platform of TEM that is capable of measuring parameters such as Seebeck coefficient (α), thermal conductivity (λ), Figure of Merit (ZT) and others in an automatic way. Experimental results show the effectivity of the proposed testing platform.

Design of an intelligent electronic device based on TivaC platform for smart grid applications

Smart Grid (SG) can be defined as a modern electric power grid infrastructure for improved efficiency, reliability and safety, with smooth integration of renewable and alternative energy sources, through automated control and modern communications technologies. The increased need for more effective control on electrical power systems has led to the development and the increased research interest on SG. The construction of SG involves the positive transformation of traditional electricity networks, with one-way power flow, to a system with a new technology, by adding intelligent sensors, distributed generation and storage system, back-end information systems, smart meters and communications networks, to permit two-way power flow with communication and control. All this information should be obtained from the network. So, the development and implementation of Intelligent Electronic Device (IED) improves the efficiency, reliability and security of the electric power system. This paper presents the development of an IED, based on TivaC platform for Smart Grid applications, with high capacity processing, communication features, portability/versatility, low cost, easy integration (interoperability) and maintenance. For the communication the proposed IED uses the Hybrid Network Architecture (HNA) concept and open source programming.

An Envelope Detector as a Trading Cost Technique for Radiometric Partial Discharge Detection

Partial discharge (PD) measurement is an established high voltage insulation monitoring technique used to facilitate the detection of incipient faults in high voltage apparatus. Based on the great importance of the power system, is constant the research about the nature and characteristics of PD sources. A low-cost, free-standing, radiometric, partial discharge wireless sensor network (PD WSN) is described for application to real-time condition monitoring, asset management and operations optimization in the future smart grid. The proposed PD WSN is based on a novel approach to PD location which obviates the need for synchronization between sensors thereby improving scalability. In this paper, the progress in the development of a PD WSN prototype is described. For the proposed evaluation of PD signals, several measurements were performed using a diskcone antenna and a commercial system based on the IEC 60270 standard. Early progress in the development of components for a PD detection system using a network of free-standing radiometers for monitoring of electricity substations has been also presented.

Estimation of lithium-ion battery model parameters using experimental data

Lithium battery cells are commonly modeled using an equivalent circuit with large lookup tables for each circuit element, allowing flexibility for the model to match measured data as close as possible. Pulse discharge curves and charge curves are collected experimentally to characterize the battery performance at various operating points. It can be extremely difficult to fit the simulation model to the experimental data using optimization algorithms, due to the number of values in the lookup tables. This paper describes a detailed procedure of how estimate the battery model parameters using experimental data. the experiment is realized with a computer that realize the control of charge and discharge process sending SCPI commands via serial communication to the Four Quadrant Power Supply from Kepco Inc. with 100V and 10A as limits. The estimation of each battery model parameter is made to lithium-ion battery with a capacity of 20 Ah, and the presented methodology can be easily adapted to any type of battery. The mean objective of the results is estimate the battery parameters to posteriorly use the battery model to estimate the SoC by adaptive method. As results, after the estimation of each parameter, it is possible to observe the resistances exponential behavior, where they decrease as SoC decrease. As conclusions, this paper can contribute to the field of measurement of magnetic and non electric quantities, where it helps to determine the Battery Equivalent Circuit Model and its parameters.

A simple circuit for characterization of photovoltaic module under uniform radiation and shading conditions

This paper proposes a practical method for characterization of photovoltaic (PV) systems under uniform radiation and under shading conditions, based on voltage and current graphics. A simple circuit to detect these shading conditions is projected to enhance the visualization of disturb caused by blocking one or more cells of the PV module. Therefore, this circuit is very interactive, because the curve changes instantly when the shading condition occurs. Thanks to it, this project is quite useful for educational purposes, in study of characterization of photovoltaic systems curves. The characteristic curves of the PV system under uniform radiation are necessary to compare with experimental results. Using an oscilloscope, the curves of a PV module under uniform radiation and partial shading are analyzed.