The article presents the novel findings on the dependence of voltage fluctuation severity on voltage distortion caused by power electronic loads. The results indicate the need to modify the recommended limitation of the IEC flickermeter bandwidth to cut-off frequency at least 450 Hz by the IEC standard, to consider the possible obnoxious voltage fluctuation caused by power electronic devices. The real voltage distortion of the “clipped sine” or “sharpened sine” type, resulting from nonlinear currents, the flow of which is forced by power electronic devices, was considered in the research. The basics of indicator P _st /P _lt measurement by IEC flickermeter are discussed, and the influence of sinusoidal supply voltage distortion on the indicator P _st measurement was investigated. The analytical model of IEC flickermeter signal chain was proposed to explain the influence of supply voltage distortion on the indicator P _st measurement. This model was verified by comparing the results of numerical simulations and laboratory measurements.

Power quality is described by voltage fluctuation measures. Voltage fluctuation is understood as “a series of voltage changes or a continuous variation of the rms or peak value of the voltage.” Voltage variation is most often manifested by flicker, which might become obnoxious at a high enough intensity. One of the standard measures of voltage fluctuation is $\boldsymbol {P}_{st}$ indicator. One of its major flaws is its limited diagnostic capabilities. Voltage fluctuation indices are the measure, which provides much bigger range of diagnostic capabilities. However, it has not been acknowledged as a standard measure. The initial part of this paper includes the description of the accepted method of reproducing voltage variation. It also presents general characteristics of the $\boldsymbol {P}_{st}$ indicator and voltage fluctuation indices. The next part of this paper describes the methods of converting voltage fluctuation indices into $\boldsymbol {P}_{st}$ indicator and vice versa. The capability of estimating the $\boldsymbol {P}_{st}$ indicator on the basis of the indices has been confirmed. Three examples of measurement results of both these measures in low-voltage (LV) power grids have been presented. These results have proved the connection between the estimated values (on the basis of voltage fluctuation indices) and the results of the $\boldsymbol {P}_{st}$ indicator measurements.

The results of the laboratory research concerning a dependence of flicker vision on voltage fluctuations are presented in the paper. The research was realized on a designed measuring stand, which included an examined light source, a voltage generator with amplitude modulation supplying the light source and a positioning system of the observer with respect to the observed surface. In this research, the following light sources were used: one incandescent lamp and four LED luminaires by different producers. The research results formulate a conclusion concerning the description of the influence of voltage fluctuations on flicker viewing for selected light sources. The research results indicate that LED luminaires are less susceptible to voltage fluctuations than incandescent bulbs and that flicker vision strongly depends on the type of LED source.

Monitoring the temperature of a semiconductor component allows for the prediction of potential failures, optimization of the selected cooling system, and extension of the useful life of the semiconductor component. There are many methods of measuring the crystal temperature of the semiconductor element referred to as a die. The resolution and accuracy of the measurements depend on the chosen method. This paper describes known methods for measuring and imaging the temperature distribution on the die surface of a semiconductor device. Relationships are also described that allow one to determine the die temperature on the basis of the case temperature. Current trends and directions of development for die temperature measurement methods are indicated.

This article addresses the problem of proper flicker severity assessment by smart energy meters. Flicker severity occurs for a typical voltage “clipped cosine” distortion caused by operation of power electronic devices in the power grid. The voltage distortion caused only by higher harmonics does not cause voltage fluctuations, and therefore does not cause flicker. This article presents the research results for some models of advanced metering infrastructure (AMI) smart meters, for which irregularities are observed in the voltage variation severity assessment if the typical voltage distortion occurs in the power grid. Possible mistakes in implementation of flickermeter signal chain as defined by International Electrotechnical Commission (IEC) in smart meters that influence the measurement results have been explained. The analysis of the influence of typical voltage distortion on the indicator $P_{st}$ measurement has been carried out analytically and in numerical simulation studies using the modeled flickermeter signal chain.