Zbigniew Olczykowski

Electric arc furnaces represent some of the most significant consumers directly integrated into power systems. The electric arc used to melt the charge generates various disturbances that can adversely affect power quality in the supply network. These disturbances arise from the dynamic fluctuations in the arc length as it traverses the scrap material. A viable approach to mitigating these disturbances involves the implementation of Static Var Compensator (SVC) systems. This study conducts a comprehensive analysis of the efficacy of fast-acting compensators in attenuating voltage disturbances generated by arc furnaces. The investigation is grounded in empirical data obtained from various voltage levels within the network that supplies power to these arc devices.

Electric traction vehicles require a power supply with appropriate voltage parameters. In Poland, a direct voltage power supply system has been adopted. This requires the use of traction substations with the conversion of alternating voltage to direct voltage, which generates a number of disturbances related to the quality of electric power. Dynamic changes in the substation load resulting from the movement of traction vehicles are another cause of voltage changes. The article presents an analysis of measurement results carried out simultaneously in systems powering various traction substations and non-traction demand lines. Due to the fact that non-traction demand lines supply both recipients related to the movement of traction vehicles (including railway stations) and other industrial and municipal recipients, the quality of energy is therefore very important.

Arc devices are among the receivers with the highest power connected to power systems. Due to dynamic load changes, these receivers generate a number of disturbances that affect the quality of electric power. The most important disturbances include voltage fluctuations. It is also worth mentioning the asymmetry and deformation of the supply voltage curve. This article discusses the mutual interaction of receivers operating in parallel, operating stably, and devices with dynamic current consumption. Calculations based on model tests and the results of parameters characterizing the quality of energy, which were recorded in the line supplying the steelworks, are presented. The power supply conditions (power of the short-circuit network) were assessed to influence the degree of suppression of voltage fluctuations by loads with stable current consumption.

Rail transport in Poland uses direct current electric traction to power vehicles (locomotives and multiple units). It is therefore necessary to convert the AC voltage of the power system into the DC voltage of the traction system. The conversion of alternating voltage into direct voltage takes place in traction substations. Rectifier units installed at traction substations are used for this purpose. As a result, electric traction should be classified as non-linear consumers. In addition, the traction substation load changes dynamically. All this makes the electric traction a recipient generating a number of disturbances to the network. These disturbances affect the quality of electricity in the power system from which the traction substations are supplied, and the quality of energy in auxiliary and non-traction lines. The article presents the results of the analysis of measurements of electricity quality indicators recorded at selected points of the traction substation line. Parameters characterizing the quality of electricity were recorded, among others, in in the main line supplying the traction substation, non-traction needs line and auxiliary circuits. The presented article is another in a series of publications related to the assessment of the impact of DC electric traction on the power system.

In Poland, rail transport is powered by the electric system with the use of traction substations that supply the electric traction with DC voltage of 3 kV. The necessity to change the alternating voltage to the constant and changing loads of the substation cause the electric traction to be a recipient, generating a number of disturbances to the network. These disturbances affect the quality of electricity in the power system from which traction substations are supplied, and the power quality in auxiliary and non-traction lines. This article analyzes the measurements of power quality indicators recorded at selected points of the traction substation system. The parameters characterizing the power quality were recorded, among others, in the main lines supplying traction substations, non-traction lines and auxiliary circuits. The presented article is the first in a series of publications related to the assessment of the impact of DC electric traction on the power system. The recorded data will be the basis for computer simulations defining, inter alia, the impact of power supply conditions for traction substations on the power system and to propose methods of reducing disturbances generated by a dynamically changing substation load.

The article presents the susceptibility coefficients active power k_p and reactive power k_q, as proposed by the author. These coefficients reflect the reaction of arc furnaces (change of the furnace operating point) to supply voltage fluctuations. The considerations were based on the model of the arc device in which the electric arc was replaced with a voltage source with an amplitude dependent on the length of the arc. In the case of voltage fluctuations, such a model gives an assessment of the arc device’s behavior closer to reality than the model used, based on replacing the arc with resistance. An example of the application of the k_p and k_q coefficients in a practical solution is presented.

Due to high unit capacities, electric arc furnaces are among the receivers that significantly affect the power system from which they are supplied. Arc furnaces generate a number of disturbances to the power grid, including fast-changing voltage fluctuations causing the phenomenon of flickering light, asymmetry, and deformation of the voltage curve. The main issues discussed in the article are problems related to the distortion of current and voltage waveforms, resulting from the operation of electric arc furnaces. An analysis of the indices characterizing the voltage distortion recorded in the supply network of the arc furnaces is presented. The changes in the range of current and voltage waveform deformation in individual smelting phases in the arc furnace are also presented. Furthermore, the changes in the degree of deformation of the current and voltage waveforms in the individual smelting phases in an arc furnace are presented. A multi-voltage electric arc model used in computer simulations is proposed.

In the case of three-phase arc furnaces, two types of asymmetry can be distinguished: constructional and operational. The structural asymmetry is related to the construction of high-current circuits supplying the arc furnace. The knowledge of the parameters of the high-current circuit allows to determine the operating characteristics of the arc device. The author proposed a method for calculating the real values of the resistance and reactance of the high-current circuit. For this purpose, tests were made to short-circuit the electrodes with the charge. During the short-circuit, with the use of a power quality analyzer, measurements of electrical indicators were carried out, which allow to determine the parameters of the high-current circuit. A new method for determining voltage operational unbalance is also presented in this paper. The theoretical considerations presented in the article were verified in industrial conditions.

Due to the dynamic nature of load changes, arc devices are receivers that generate disturbances to the network that affect the power quality. The main disturbance generated by these receivers are voltage fluctuations. One of the effects of voltage fluctuations is the flicker of light caused by lighting receivers. The article presents an analysis of changes indicators flicker of light measured in networks supplying arc furnaces. The propagation of voltage fluctuations to the lines supplying lighting receivers was analyzed. The network parameters influencing the amount of light flicker were estimated. The paper presents a method for calculating the increased flicker of light when several electric arc furnaces are operated in parallel. The conclusions regarding the use of the presented research in practical applications are given in the summary.

Arc furnaces can be classified as electricity receivers, which largely affect the quality of electricity in the power system. Voltage fluctuations are the main disturbance generated by arc furnaces. The effects of voltage fluctuations include the phenomenon of flickering light. Apart from voltage fluctuations, arc devices, to a lesser extent, are the source of current and voltage asymmetry, voltage curve distortion, and voltage dips. The main purpose of theoretical considerations is to assess the voltage fluctuations generated by arc furnaces. The article presents a model of an arc device in which the arc has been replaced by a voltage whose value depends on the arc length. It presents also the results of the analysis of measurements of the parameters characterizing voltage fluctuations and flicker indicators.