The main reasons for installation of power quality meters in distribution transformer substations are power quality monitoring and global evolution of electrical network towards the ‘smart grid’. In case that all measurements from the meters are properly synchronised and centralised, new possibilities of control or evaluation of the network are enabled. This contribution proposes the possibility for an earth fault localisation with the aid of synchronised data recorded on the low‐voltage side of the medium voltage/low voltage transformers in compensated neutral distribution networks which are equipped with auxiliary resistor for short‐time increasing of the active part of the fault current. The described method uses voltage sags evoked by connecting of the auxiliary resistor for locating the faulty section. The proposed method is tested with the help of numerical model which presents a part of the distribution network.

The paper describes a unified methodology which takes into account the advantages and disadvantages of different Power Line Communication (PLC) technologies suitable for Smart Metering deployment. The methodology should provide a detailed evaluation of PLC technologies based on a clear definition of the different parameters and their measurement. Based on this methodology, we should be able to provide a comparison of the selected technologies and the methodology should also provide data for the design of a telecommunication infrastructure for Smart Metering/Smart Grids. In this paper and based on this methodology, we also present the performance tests carried out in laboratory environment on low voltage and in on-field conditions on medium voltage.DOI: http://dx.doi.org/10.5755/j01.eie.24.3.20983

This paper presents the concept of the impact of harmonic distortion on a digital protection relay. The aim is to verify and determine the reasons of a mal-trip or failure to trip the protection relays; the suggested solution of the harmonic distortion is explained by a mathematical model in the Matlab Simulink programming environment. The digital relays have been tested under harmonic distortions in order to verify the function of the relays algorithm under abnormal conditions. The comparison between the protection relay algorithm under abnormal conditions and a mathematical model in the Matlab Simulink programming environment based on injected harmonics of high values is provided. The test is separated into different levels; the first level is based on the harmonic effect of an individual harmonic and mixed harmonics. The test includes the effect of the harmonics in the location of the fault point into distance protection zones. This paper is a new proposal in the signal processing of power quality disturbances using Matlab Simulink and the power quality impact on the measurements of the power system quantities; the test simulates the function of protection in power systems in terms of calculating the current and voltage values of short circuits and their faults. The paper includes several tests: frequency variations and decomposition of voltage waveforms with Fourier transforms (model) and commercial relay, the effect of the power factor on the location of fault points, the relation between the tripping time and the total harmonic distortion (THD) levels in a commercial relay, and a comparison of the THD capture between the commercial relay and the model.

The aim of the paper is to describe procedures for systematical determination of immunity of lamps to supply voltage variations caused by interharmonics. The curve of lamp immunity is presented as an interharmonic magnitude versus interharmonic frequency curve and is called interharmonic-flicker curve. The interharmonic-flicker curves of lamps are determined by utilizing a modified concept for measurement of a lamp gain factor in frequency domain and by utilizing the published limits on voltage flicker. Another described method for establishing the interharmonic-flicker curves of lamps is the method based on measuring the luminous flux flicker curve which is defined by utilizing the published limits on voltage flicker as well. Further a complex measured data file of interharmonic-flicker curves in various combinations of discharge lamps (fluorescent lamps and high intensity discharge lamps) and ballasts are pointed. Measured and compared combinations include various types of discharge lamps, various wattages, modes of operation of the ballast and its specific designs and dimensioning of circuit elements etc. Finally, determined interharmonic-flicker curves of chosen lamps are used for proposal approach how to revise the compatibility level for interharmonic voltages relating to flicker.

In general, the power quality analysis is a very complex issue and it requires a long-term measurement in real distribution networks. Moreover, the voltage has to be within specific voltage tolerance for the low-voltage distribution network. In this paper the measurement of the low-voltage network after the connection of a small photovoltaic power plant is evaluated. Therefore, the influence on the changes of the voltage, flicker and total harmonic distortion by connected power plant under different operating states is described in the paper. The main task of the article is to present the results of the voltage quality measurements carried out in low-voltage distribution network.