J. A. Jardini

Daily load profiles for residential, commercial and industrial low voltage consumers

This paper presents the results of the study carried out for the determination of the residential, commercial and industrial consumers daily load curves based on field measurements performed by the Utilities of Electric Energy of Sao Paulo State, Brazil. A methodology for the aggregation of these loads to determine the expected loading in equipment of in a preset part of the distribution network by using the representative daily curves of each consumers activity and the monthly energy consumption of the connected consumers is also presented.

Identiffication of Synchronous Machine Parameters Using Load Rejection Test Data

This work shows a computational methodology for the determination of synchronous machines parameters using load rejection test data. By machine modeling one can obtain the quadrature parameters through a load rejection under an arbitrary reference, reducing the present difficulties. The proposed method is applied to a real machine.

A standstill frequency response method for large salient pole synchronous machines

In this article, a Standstill Frequency Response Test (SSFR) is proposed, with the aim of determining the direct and quadrature axis operational impedances for salient pole synchronous machines. The method is applied with the rotor at standstill in a given arbitrary position, thus avoiding the difficulties in rotor mechanical alignment and rendering it suitable for large salient pole synchronous machines of hydroelectric power plants.

Expert system for the assessment of power transformer insulation condition based on type-2 fuzzy logic systems

An efficient expert system for the power transformer condition assessment is presented in this paper. Through the application of Duvals triangle and the method of the gas ratios a first assessment of the transformer condition is obtained in the form of a dissolved gas analysis (DGA) diagnosis according IEC 60599. As a second step, a knowledge mining procedure is performed, by conducting surveys whose results are fed into a first Type-2 Fuzzy Logic System (T2-FLS), in order to initially evaluate the condition of the equipment taking only the results of dissolved gas analysis into account. The output of this first T2-FLS is used as the input of a second T2-FLS, which additionally weighs up the condition of the paper-oil system. The output of this last T2-FLS is given in terms of words easily understandable by the maintenance personnel. The proposed assessing methodology has been validated for several cases of transformers in service.

Synchronous machines parameters identification using load rejection test data

This work shows a computational methodology for the determination of synchronous machines parameters using load rejection test data. The quadrature axis parameters are obtained with a rejection under an arbitrary reference, reducing the present difficulties.

Distribution transformer loading evaluation based on load profiles measurements

This paper presents a methodology for residential distribution transformer loading evaluation. The transformer daily load profiles are applied to determine the expected loss of life. Different calculation alternatives are used and compared. It proposes a methodology which includes the load curve shape obtained by measurements.

Power Transmission Over Long Distances: Economic Comparison Between HVDC and Half-Wavelength Line

In this paper, the economics of some alternative solutions for point-to-point transmission of bulk power over long distances, namely, HVDC and half-wavelength lines (HWLL), are evaluated. Also, the main technical aspects of the half-wave length transmission technology in order to define the line design and its required equipment are discussed. A two-line, 2500 km transmission system (which is half the wavelength of a 60 Hz power frequency) carrying 6000 MW is used as the base case to perform the comparison. Finally, issues related to the sensitivity of such a cost comparison between the HVDC and HWLL alternative is presented.

An experiment using an object-oriented standard-IEC 61850 to integrate IEDs systems in substations

The integration of microprocessed equipment from different manufacturers has been a difficulty in the automation of power substations, considering that the development of protocol converters is a demanding task, with questionable and costly results for the utilities. Even with the adoption of protocols that were particularly developed for the electric power sector, such as the IEC 60870-5 and the DNP, failed to solve all problems, as it only facilitates the communication between equipments, and a considerable engineering effort still must be made in the integration of such data. In response to such needs, the EPRI issued a set of recommendation standards that is now known as UCA. The IEC organization is working on the integration of UCA protocols, models and services for substations by means of the IEC 61850 standard. This article introduces the use of such protocol in substation automation from the users viewpoint, analyzing the needed requirements to implement and integrate equipments using the IEC 61850 standard.

Feasibility of Electronic Tap-Changing Stabilizers for Medium Voltage Lines—Precedents and New Configurations

Thyristor-based onload tap-changing AC voltage stabilizers are cheap and robust. They have replaced most mechanical tap-changers in low voltage applications from 300 VA to 300 kVA. Nevertheless, this replacement hardily applies to tap-changers associated to transformers feeding medium-voltage lines (typically 69 kV primary, 34.5 kV line, 10 MVA) which need periodical maintenance of contacts and oil. The Electric Power Research Institute (EPRI) has studied the feasibility of this replacement. It detected economical problems derived from the need for series association of thyristors to manage the high voltages involved, and from the current overload developed under line fault. The paper reviews the configurations used in that field and proposes new solutions, using a compensating transformer in the main circuit and multi-winding coils in the commutating circuit, with reduced overload effect and no series association of thyristors, drastically decreasing their number and rating. The stabilizer can be installed at any point of the line and the electronic circuit can be fixed to ground. Subsequent works study and synthesize several commutating circuits in detail.

Mobile robot for hot spot monitoring in electric power substation

This article describes the development of an unmanned monitoring system for the detection of hot spots inside a power substation. It uses an infrared camera connected to a robot which moves along the substation via a steel cable inside the substation. The robot is remotely controlled by a wireless system, operating at a frequency of 2.45 GHz (WiFi). The camera is dynamically directed to different substation components through a pan-tilt system. The whole structure is controlled by a microcomputer software located in a control room, around 200 m away from the robot. Aside of controlling the robot pan-tilt movements, the software also performs the data acquisition and analysis of thermographic images, thus detecting the referred hot spots.