Power System Impedance Estimation Using a Fast Voltage and Current Changes Measurements

Abstract

Equivalent power system impedance is an important electrical quantity from many points of view. Areas in which this parameter plays an important role include, in particular: Voltage stability analysis, power quality, or fault condition analysis. Power system impedance estimation in real operation conditions can be performed by one of the non-invasive methods described by different authors. This paper aims to investigate and compare seven different methods for power system impedance estimation based on voltage and current variations measurement. After a brief description of selected methods, these methods were applied for power system impedance estimation in the case of two simple simulation tests and then in the case of three real measured data. Voltage and current changes used for power system impedance estimation in real conditions were measured in high voltage (HV) and medium voltage (MV) substations feeding steel mill with the electric arc furnace (EAF) operation. As the results presented in this paper have shown, not all of the methods analyzed are suitable for determining the power system impedance based on the fast step changes of voltage and current that occur, for example, during an EAF operation. Indeed, some of the tested methods were originally designed to determine the power system impedance from changes in voltages and currents recorded at steady state.

Evaluation of Flicker of Light Generated by Arc Furnaces

“…With the measurement data of the flicker indicators at the level of 110 kV, the values of the indicators at the level of 400 kV can be determined: P st (A) = P st (B) × 0.17 (7) Figure 9 shows changes in flicker indicators recorded during one week and determined theoretically with the calculated TC AB = 0.17 propagation coefficient. Figure 8 shows changes of Pst short-term flicker severity recorded simultaneously during one week of measurements at two points: steelworks supply line (Pst_Point A_meas), EAF supply line (Pst_Point B_meas) and determined by Formula (5) (Pst_Point B_cal).…”

“…The publications [1][2][3][4][5][6][7] show the mechanism of the flicker of light, which is the effect of voltage fluctuations. The publication [8] presents, among others, methods of limiting voltage fluctuations through the use of energy storage.…”

Artificial Neural Network-Based Constrained Predictive Real-Time Parameter Adaptation Controller for Grid-Tied VSCs

“…Active methods intentionally disturb the grid and then perform data analysis. Some of the examples of active techniques are frequency [16], [18], [21], [28], [29], transient voltage [30], [31], and current impulse injection [32]. The frequency injection technique is divided into insection of a single frequency such as 75 Hz [16], 300 Hz [18], and 600 Hz [29], dual frequencies such as 400 Hz and 600 Hz [29], and a large spectrum of frequencies [21].…”

Modeling of Voltage Fluctuations Generated by Arc Furnaces

“…Publication [22] discusses a method for selecting the elements of a C-type filter working with a conventional LC-type filter for compensating reactive power and filtering out higher harmonics generated by arc furnaces and ladle furnaces. The assessment of the parameters of the power supply network for arc furnaces based on the measurements of currents and voltages is presented in publication [23]. The single-phase equivalent diagram of the arc furnace supply network is being considered (similarly to the presented article).…”