Nelson M. Matsuo

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.

Calibration of High Voltage Transducers for Power Quality Measurements in Electric Networks

The term power quality is, in general, closely related to the quality of the voltage. Considering the widespread presence of sensitive loads in the electric grid, and the increasing awareness of the consumers concerning the quality of the power supply, the control and measurement of power quality parameters regarding harmonics, interharmonics, sags, swells, and others are increasingly becoming much more important. Most of the necessary calibration procedures for power quality monitors and power quality analyzers are already defined in the international standards, mainly in the IEC 61000 series (IEC, 1995) and ANSI/IEEE Standards. This chapter presents results of a research which aimed to develop a methodology for the calibration of high voltage transducers for power quality measurements in high voltage networks, considering that such kind of procedures have not been established in the pertinent standards yet (Bradley et al., 1985; Seljeseth et al., 1998). In this research it is also considered that the conventional high voltage laboratory is not suitable for power quality tests. Thus, some improvements are needed regarding such matter. In this development, modelling and computer simulation using ATP – Alternative Transients Program (ATP, 1987) were used to assess both the frequency response of the test setup, and the design of the reactive compensation of the test circuit.

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.

Computerized system for detection of high impedance faults in MV overhead distribution lines

This paper presents a computerized system for detection of high impedance faults (HIF) in MV distribution feeders. This system has been developed in an R&D Project of AES Eletrpaulo. A HIF occurs when an energized conductor makes contact with objects with a high resistance and there are no significant increases in current. It is common to associate HIF to situations in which there is fallen primary conductor, creating risk of fatal accidents due its proximity to people. This is the main focus of this project. This type of fault cannot be detected by traditional overcurrent protection devices. The method developed herein relies on the use of variables obtained from power quality meters installed at the feeders in the substation, measuring quantities such as current harmonics, sequence components amongst others, with which some indices are calculated to detect the occurrence of a HIF event using artificial neural networks (ANN). The proposed system was implemented and installed in an AES Eletropaulo substation.

Locating power quality meters in order to perform harmonic state estimation

The aim of this paper is to present a methodology that defines the most suitable places for installing power quality meters in power system networks, in order to guarantee that all state variables may be directly or indirectly monitored. Initially, the methodology established connectivity rules based on Kirchhoffs Current and Voltage Laws that allows one to verify if all the state variables will be monitored by a possible monitoring system configuration. Then, a branch-and-bound searching algorithm was developed, in order to determine the optimal monitoring system configuration for the IEEE 14-bus system. The effectiveness towards the harmonic state estimation of the achieved monitoring systems configurations are checked with a time domain reference case.