Pedro Issouribehere

Power quality measurements in a steel industry with electric arc furnaces

Many loads connected to electric power systems can cause power quality problems at all voltage levels and for very different power ratings due to their unbalanced and non-linear behavior characteristics. This paper describes the aspects of power quality at the point of common coupling (PCC) where an arc furnace for steel melting with alternating current is connected. By measurements of Flicker, harmonics content in voltage and current, active and reactive power and power factor, the preservation of the reference levels for the supply voltage and emission limits for the furnace as a customer are evaluated. The evaluation of power quality of contemporary International and Argentinian standards is given. The different phases in the operation of the arc furnace are described in detail and illustrated with measurements.

Measurements and Studies of Harmonics and Switching, Transients in Large HV Shunt Capacitor Banks

Adding capacitors to an electric power system provides well known benefits, including power factor correction, voltage support and increase of active power transfer capacity. However, the capacitor banks modify the harmonic voltages and currents in the network and give rise to current and voltage transients, stressing switching devices and sensitive loads. The first part of the paper describes measurements and studies performed before the installation of 2 x 50 MVAr capacitor banks in a 500-132 kV substation, in the Argentinian Transmission System. By measurements of harmonics content in voltage and current, the IITREE performed some studies to quantify the harmonic voltage in the 132 kV busbar and the harmonic voltages and currents in the capacitors to prevent excessive overload. Switching transients were also studied. The studies carried out with the electromagnetic transients program (EMTP) are presented. The second part of the paper deals with measurements performed after the installation of the 2 x 50 MVAr capacitor banks. These measurements were carried out to verify the harmonic levels in the busbar and in the capacitor bank, and to obtain the current and voltage switching transients. The results of measurements are compared to the ones obtained by studies and simulations.

Perturbation measurements on HV overhead lines using Electric Field Sensors

It is widely known that in most countries there are severe Power Quality rules that Utilities as well as customers have to comply with. Therefore, it is necessary to assess carefully the levels of disturbances. The traditional procedure to determine the origin of such disturbances is to perform field measurements in all the plants containing power electronic equipment, electric arc furnaces, etc., located near the point in which high levels of disturbances have been detected. Nevertheless, in most cases field engineers find it difficult to have access to the plants belonging to Utilities and also to the different industries settled nearby, which are also likely to emit disturbances. In addition, the task of installing the PQ recorder in the electrical cabinets inside the plant demands a considerable time, as well. With the intention of avoiding all the difficulties that can arise when field engineers are searching for a disturbing load, it was considered a great challenge to design a novel device to make the field work simpler. Such a challenge was based on designing a measuring system capable of recording voltage waveforms with no physical contact with the installations and without the assistance of Utilities personnel. In order to achieve this goal an Electric Field Sensor (EFS) was employed in the design of the measuring system. This paper deals with the results of testing an electric field measurement system - completely designed by the authors - for monitoring voltage Flicker and harmonics in overhead power systems [1]-[3]. Some results of field measurements performed in plants containing disturbing loads are shown.

Assessment of Power Quality indices over a decade of control in Argentinian distribution system

The electricity distribution service in the Buenos Aires metropolitan area of Argentina, which was privatized in the early nineties, is carried out by three different Utilities and the control is performed by a Regulatory Agency (ENRE).

Power quality measurements and mitigation of disturbances due to PWM AC drives

Variable speed AC drives are finding their place in all types of industrial and commercial loads. One important application of these drives is in process control, controlling the speed of fans, compressors, pumps and blowers. However, there are many line (source) design parameters frequently overlooked. A pipeline for transporting synthetic crude oil was installed in Argentina and variable frequency drives (VFD) were employed to control the centrifugal pumps, in order to provide flow and pressure control. During the commissioning and start-up program, the IITREE-LAT performed power quality measurements and EMC studies in the petroleum process plants. The first part of the paper deals with the problem of common- mode voltages and its mitigation. In the second part of the paper, the preservation of the reference levels for the supply voltage and emission limits for the petroleum plant as a customer is evaluated by measurements of harmonics content in both voltage and current. An LC resonance problem was found and a practical solution was implemented. The fulfillment of power quality limits for both International and Argentinian standards is assessed. Finally, the behavior of the VFD - in terms of PQ indicators - under different load conditions is analyzed in detail.

Compatibility between Disturbance Emission and Argentinian Power Quality Regulations in Iron and Steel Industries

Measurements and studies developed to mitigate harmonic and flicker emission to public networks are presented in this paper. Two different real cases are analyzed. The first one is a new electric furnace with low power factor, which is added to the load consisting of other existing furnaces. The installation had a reactive compensation bank which, according to measurements and studies, would cause harmonic resonance with weak public networks. As technical solution, a dumped C-type filter was designed, taking advantage of the existing bank, to comply with limits established by ENRE 99/97 and IEEE 519/1992. The other case deals with a 2.5 MW electric arc furnace fed from the public MV network. The carried out measurements harmonics, voltage and current unbalances, active and reactive power, power factor and flicker determined that the high flicker level was the most critical disturbance. In addition, the compensation factors required to comply with reference levels and also to determine the dimension of the suitable static compensator were calculated

Evaluación y diagnóstico de fallas en una trefiladora industrial

An important company located in an Industrial Park on the outskirts of Buenos Aires detected a sudden electrical failure in the plant, which used to affect the normal operation of a brand new wire stripping machine. Naturally, such a failure used to lead to significant losses on the production process. For this reason, the issue needed to be addressed in the short term.

Results on harmonic and flicker control in Buenos Aires public distribution services

The public electric services in Buenos Aires metropolitan area are rendered by 3 private companies, called A, B and C in the text. The control is carried out by the Ente Nacional Regulador de la Electricidad (ENRE). The Instituto de Investigaciones Tecnologicas para Redes y Equipos Electricos (IITREE) of Universidad Nacional de La Plata (UNLP) collaborates in technical assistance. The disturbance-harmonics and flicker-Monitoring Programs started at the beginning of 1997, that is why, so far, an important amount of measurements have been collected. The levels of harmonic representative magnitudes, its behavior throughout the day and the year are analyzed. These levels are compared between the three Utilities in different years. The procedures used for the evaluation of penalties in harmonic and flicker normalized measurements are explained, showing then the transgression of the allowed levels and the unitary sums of the penalties.