José Rubens Macedo

Real time power quality monitoring system according to new Brazilian regulation policies

This work is about a developed and implemented power quality digital meter to comply with the new Brazilian standard to regulate the Power Quality in Brazil. The objective of this work has been to develop a low cost device able to monitor the main indices of standard such as the steady state rms voltage, harmonic distortion, fluctuation voltage, unbalance voltage, voltage sags and swells and power supply interruptions in real-time. Through a cellular module the device meter is remotely controlled and configured. This way, it can send periodically measurements and information data to a remote server. Other discussed point has been the power quality indices of the standard.

Two-Wire Distribution System for Power Supply to Three-Phase Rural Facilities

Nowadays, the electric power supply to rural facilities is commonly composed by single-phase medium voltage grids. Eventually, some of these rural facilities require the use of more significant driving loads, making necessary the replacing of the single-phase networks by a new medium voltage three-phase network. Thus, despite the fact it is a new or an existing facility, the construction costs related to a new medium voltage three-phase grid, which may have some miles long, could cripple investment to be made by the farmer as well as increase utility tariffs due to higher costs of the three-phase distribution networks in rural areas. In this context, this paper presents an innovative and low cost power supply to attend three-phase rural facilities through a new two-wire distribution system.

In search of the equivalent neutral path resistance and the effective voltage for compliance with IEEE Std 1459-2010

This paper presents a practical method for a real-time measurement of the ratio ρ = rneq/r (r = line resistance, rneq = equivalent neutral path resistance) of a three-phase four-wire distribution feeder and advocates the possibility of ignoring the zero-sequence voltage component due to its reduced magnitude in practical situations. The ratio ρ has a significant impact on the value of the apparent power as defined in IEEE Std 1459-2010. In practical terms, this quantity is time variable being a function of soil moisture and temperature. This work presents a proposal for measuring the equivalent neutral path resistance considering the smart metering technologies currently available.

An evaluation of shunt active filtering techniques in the era of smart grids

This paper presents a comparative evaluation of two commonly used active filter methods. In the first method the active filter performance is based on injection of harmonic currents 180o out of phase with the harmonics produced by the non-linear loads that must be compensated. Therefore, the compensated line current is equal the 50/60 Hz positive sequence current. In the second method the line current is adjusted to have a waveform that is a replace of the voltage waveform. Thus, the non-linear load and the active filter perform like a unity power factor non-linear load. The preliminary results show that the second method is slightly more effective than the first method. It leads to less voltage distortion and reduced distribution line losses. Additionally, it is shown that the second method could be even more advantageous considering the supraharmonic currents generated by the actual distribution systems based on smart grids, modern electronic loads and distributed generation devices.

Análise de desempenho do flickermeter na presença de componentes inter-harmônicas

Until the beginning of the first decade of this century it was believed that the appearance of the phenomenon of voltage fluctuation, and eventually flicker, was necessarily related to the abrupt changes, repetitive or random, in reactive power required by some loads like, for example, electric arc furnaces and hot strip mills. Concomitantly, the IEC flickermeter protocol was developed in this specific context. In this sense, the present paper shows some simulation results, as well as results obtained in the laboratory, showing problems in the quantification of voltage fluctuations by the IEC flickermeter, when interharmonic voltages are superimposed on the fundamental frequency.

Método da superposição modificado como uma nova proposta para atribuição de responsabilidades sobre as distorções harmônicas

Faced with the guidelines contained in documents approved by the National Electric Power Agency PRODIST - Module 8, among other indicators of electric power supply quality, the harmonic distortion emerges as an important issue. The mentioned regulation takes into account specific matters such as definitions, measurement procedures, benchmarks, etc. Having this in mind and recognizing that the mitigation techniques will often involve financial costs to fit the measured values to the recommended ones, the search for ways to determine the level of contribution between the supplier and the consumer appears as an important subject at sharing the technical and economical responsibilities. In general, the published approaches at attempting to provide the utility and consumer involvement are based on frequency domain techniques and superposition principles. Although the idea is quite simple, the required data are derived from harmonic measurement and the equivalent source and load harmonic impedance, being these parameters very hard to be obtained. Within this context, the present paper aims at providing means to apply the classical referred method to evaluate the required harmonic contribution throughout a strategy to overcome the difficulties here mentioned.

Modified superposition method for assignment of responsibilities on harmonic distortions

Considering the guidelines contained in documents such as the IEEE Standard 519 and IEC 61000-3-6 that includes, among other indexes of power quality, the thematic of the harmonic distortion, the mentioned text refers to issues associated with definitions, measuring procedures, reference values, etc. Taking under consideration these determinations, and recognizing that the mitigating solutions for the adequacy of performance indexes involve significant financial costs, the proposition of finding ways to determine the responsibility for possible violations of pre-established limits for harmonic distortion arises. Among the proposals found to detect the contribution portions coming from the supplier and the customer, it is noteworthy that, in general, the methodologies based on principles use the frequency domain harmonized with the superposition of effects. Despite the simplicity of this procedure, it is emphasized that it relies on measuring information and on the previous knowledge of the equivalent harmonic impedances of the utility and customer, whose information are of difficult access. In this context, this paper is focused on a feasibility proposition to solve the above mentioned difficulties in obtaining the percentage of responsibility between the parties.

Modelagem, construção e análise de desempenho do flickermeter IEC

O presente trabalho apresenta a modelagem passo a passo do flickermeter baseado no protocolo IEC 61000-4-15, implementado em ambiente computacional Matlab-Simulink®. O referido modelo constitui uma ferramenta de grande utilidade nas simulacoes e estudos associados com a qualidade da energia eletrica, notadamente relacionados com o fenomeno da flutuacao de tensao nos sistemas de potencia. Adicionalmente, o trabalho apresenta uma nova proposta de implementacao do bloco 5 do flickermeter IEC, responsavel pela analise estatstica dos registros de sensacao instantânea de flicker e pelo calculo do indicador de severidade de flicker de curta duracao (Pst). Por fim, sao apresentados os resultados dos testes de calibracao do modelo desenvolvido, assim como os testes de desempenho de um medidor (hardware) desenvolvido utilizando-se o modelo de flickermeter proposto no presente trabalho.

Power quality real-time Monitoring System for the new Brazilian standard

This work deals with the development of a digital power quality meter to comply with the new standard which regulates the Power Quality requirements in Brazil. The purpose was to develop a low cost device able to monitor the main standard indices such as the steady state RMS voltage, harmonic distortion, voltage fluctuation, voltage unbalance, voltage sags and swells, and power supply interruptions in real-time. Through a cellular module the device meter can send measurements and data to a remote server, as well as be remotely controlled and configured. Other discussed point is the power quality indices of the new standard.