Juraj Havelka

Multi-variable series infinite impulse response least squares algorithm

The comparison is discussed between the multi- variable LSQ algorithm and newly developed LSQ IIR algorithm; the operation characteristics of both algorithms are analyzed. The obtained analyses results indicate the advantages of LSQ IIR algorithm over the LSQ one. The LSQ IIR algorithm is used in extracting fundamental components of voltage and current waveforms from which the amplitudes and phases of each component are obtained.

Distance protection relays installation prioritization in distribution networks using analytic hierarchy process and cost-benefit analysis

Due to the increasing low capacity distributed generators (DGs) installations and penalization of supply disruptions in electrical distribution grid, it is necessary to invest in the distribution protection system. This paper discusses profitability of installation of relays with distance protection function that could protect lines of different voltage levels, lengths and other relevant attributes. The aim is to determine which lines are worth protecting with distance protection and according to that, order of investment by multi-criteria decisionmaking method — analytic hierarchic process (AHP). The first part is an introduction where the circumstances, potential benefits and problems that may arise in distribution grids are presented. This is followed by theory of distance protection and analytic hierarchy process. The final part describes the criteria that should be considered and the way of applying the AHP method with a real example from Croatian distribution grid.

Numerical phaser estimation algorithms

Continuous development of electrical power systems has resulted in very complex relay protection system with associated numerical protection algorithms. Reliability, selectivity and speed are the basic design requirements for the development of new algorithms. Ideally the amplitude estimation algorithms should determinate the amplitude as fast as possible, theoretically with just one sampled value. Currently there are no algorithms which can do that with a high reliability. Abovementioned requirements are contradictory which makes it impossible to completely fulfil all of them. Current and voltage based phasor estimation algorithms are the core of all numerical protection relays, thus significantly defining protection function performances. A detailed overview of the most common numerical phase estimation algorithms is shown in this paper, including time responses on various input signal combinations. All algorithms are simulated in the LabVIEW development environment.

Method for nonlinear fitting and impedance analysis with LCR meter

In this paper new method for nonlinear fitting application is defined, described and tested. The method used the data acquired with LCR meter, nonlinear models of equivalent circuits, nonlinear fitting algorithm and iterative procedure for minimization mean square error between input data and nonlinear impedance model. The low cost LCR meter has been used and adopted to perform frequency range sweep impedance analysis and substitute more expensive impedance analyzer instruments. The method is tested in laboratory with different RLC circuit structures. Presented method for nonlinear fitting and impedance analysis can be applied on data acquired with different instruments according to application needs.

Testing ATP-EMTP in power system protection

The paper presents an evaluation of the ATP-EMTP in power system protection. A simulation model of an actual power plant and substation were created and short circuits were simulated. The analysis of results is given and compared with actual results of the real measurements.