S.X. Duarte

A Power-Quality Index to Assess the Impact of Voltage Harmonic Distortions and Unbalance to Three-Phase Induction Motors

This paper discusses the need to simultaneously monitor voltage unbalance and harmonic distortions in addition to root-mean-square voltage values. An alternative way to obtain the parameters related to voltage unbalance at fundamental frequency as well as voltage harmonic distortions is here proposed, which is based on the representation of instantaneous values at the dq axes and at the instantaneous Euclidean norm. A new power-quality (PQ) index is then proposed to combine the effects of voltage unbalance and harmonic distortions. This new index is easily implemented into existing electronic power meters. This PQ index is determined from the analysis of temperature rise in induction motor windings, which were tested for long periods of time. This paper also shows that these voltage disturbances, which are harmful to the lifetime expectancy of motors, can be measured by alternative ways in relation to conventional methods. Although this paper deals with induction motors only, the results show the relevance for further studies on other pieces of equipment.

Influence of RMS variation measurement protocols on electrical system performance indices for voltage sags and swells

This paper presents an evaluation study for measurement protocols of characteristic parameters related to short duration voltage variations (SDVs). The evaluation of possible differences in the magnitude and the duration of SDVs produced by different protocols is of great importance, for the electrical system performance indices related to voltage sags and swells are in practice obtained by measuring instruments. The study made use of a digital simulator that generated voltage conditions resultant of faults in a distribution network. Several measurement protocols for SDVs were applied and an overall comparison was performed.

Evaluating the risk of equipment disruption related to voltage sags

This paper presents a methodology for risk analysis applied to voltage sags in distribution networks. The basis of the methodology is presented, as well as the description of its implementation. Two evaluations are performed for a given distribution network: frequency of occurrence of voltage sags and the impact of the voltage sags on customer loads in statistical basis. Fault events are simulated using the Monte Carlo method, in which variables related to faults are determined according to their probability distributions. The magnitude and the duration of voltage sags and occurrence of interruptions are determined in the network points by considering the fault conditions and the line overcurrent protection devices characteristics. The results presented are indices of sag events and equipment breakdown for any desired voltage tolerance curves, which allows mapping the network in respect to risk, associated to sag events. The emphasis of the studies lies upon the practical questions that appear when industries already installed or planning installation are faced with decisions which are influenced by the rate of occurrence of voltage sags.

A methodology for monitoring harmonic distortions in electric power distribution systems

This paper deals with a methodology for the assessment of power quality indices in electric power distribution system, particularly related to voltage harmonic distortions. The paper also presents a proposal for a measurement protocol, a testing procedure to evaluate existing power quality meters and recommendations for the introduction of consistent harmonic assessment indices and parameters to support the implementation of power quality standards in distribution systems.

Methodology for support and analysis of indemnity requests due to electrical equipment damaged in Eletropaulo customers

This paper presents a management system basis for analysis and technical support in order to attend indemnity customers after electrical equipment damages. This system is already in use by Eletropaulo, but now is being improved. The job includes solicitation studies that costumers are subjected to, that are performed by computational simulations; automatic collect system data optimization and the improvement of the analysis program (PID). Diagnosis are automatically generated by this program and the engineer is able to take a brief decision. It is presented a general overview of all the project, including computational studies realized with aid of ATP (Alternative Transients Program).

A methodology for the assessment of short duration voltage variations in electric power distribution systems

This paper deals with a new methodology for the assessment of power quality indices in electric power distribution systems. Power quality indices concerning short duration voltage variations, i.e. voltage sags and swells, are particularly introduced taking into account the needs for establishing power quality standards. The paper also presents a new proposal for a measurement protocol, a testing procedure to evaluate existing power quality meters and recommendations for the introduction of consistent assessment indices and parameters concerning this important power quality phenomenon.

A Portable Voltage Regulator as an innovative smart grid solution

This article focuses on the developing of a Portable Voltage Regulator for Low Voltage Networks (PVRLVN), for single phase, two phases and three phases networks. This one is an effective equipment to regulate voltage in customer since the time established by the regulatory standards is a factor that limits the planning and the execution of corrective actions. The first PVRLVN (for two phases network) was developed inside a Research & Development Project financed by AES Eletropaulo, a Brazilian energy distribution company. Then, the PVRLVN for single phase and three phases were developed, designed and tested in a laboratory and in a real grid. Those were installed in several different locations in actual network of the AES Eletropaulo and AES Sul, both Brazilian distribution companies. Also, software for simulating alternatives and works to amend voltage levels provided to affected low voltage customers was developed.

A Laboratory infrastructure to support utilities in attaining power quality and Smart Grid goals

The Advanced Distribution Automation (ADA) and new technologies that come with smart grids bring great benefits to power quality and reliability [1]. However, the introduction of new technologies into existing power networks is a major challenge for power distribution utilities. This paper deals with the development and application of the Smart Grid Laboratory of São Paulo University (USP) designed to be a platform for real-time testing of IEDs (Intelligent Electronic Devices) and Smart Grid functionalities in a controlled environment in order to assist distribution utilities in all stages of Smart Grid implementation and to improve power quality.

Portable voltage regulator: An industrial solution for amending voltage in low voltage networks

This article focuses on the developing of a Portable Voltage Regulator for Low Voltage Networks (PVRL VN), for single phase, two phases and three phases networks, which envisages meeting the regulations, given that the time established by the regulatory standards is a factor that limits the planning and the execution of corrective actions. The first PVRLVN was developed inside a Research & Development Project financed by AES Eletropaulo, an energy distribution company with more than 5,8 million customers in the greatest city of Brazil. This PVRLVN, with the portability to be installed on a pole near customers with voltage problems, was developed, designed and tested in a laboratory and also in a real grid to be a temporary equipment that would adjust the voltage of the grid continuously to the right level until a definitive solution be done by the utility, avoiding penalties. The developed regulators were installed in several different locations in actual network of the AES Eletropaulo and AES SuI, both Brazilian local distribution companies.

UPS with communication and power Grid monitoring functions for traffic light systems

Some customers; like hospitals, fire departments and traffic control; have special needs related to power supply. Sooner the power outage diagnostic, sooner the maintenance and the time without energy is reduced. Power quality problems can disturb traffic semaphores controls and the utilities do not have a real-time monitoring system for the low-voltage grid. An UPS with batteries was developed, for traffic semaphores with LED lamps, with a communication channel. This equipment can supply the semaphores during power failure and can transmit self diagnostic and information about the grid status to the utility.