In this paper Adaptive Chirp transform (ACT) and Chirp-z transform (CZT) for measurements of frequency spectrum are presented. Algorithms are adjusted according to IEC 61000-4-7 standard. Interpolated ACT with narrowed frequency span is used for Phase Lock Loop (PLL) synchronization. The CZT is used along with windows function, to obtain the amplitudes of signal harmonics and interharmonics. Window function length is defined by PLL. All parts of proposed algorithm are tested through various simulations with changing parameters of analysed signals. This paper shows that CZT can be adjusted to synchronization and measurement of frequency spectrum. Results are comparable to the traditional approach (DFT) and completely satisfy the needs according to standard IEC 61000-4-7.

We present two stochastic modelling approaches to improve state estimation in low and medium-voltage grids. First, a dynamic model for a disturbance observer state estimation is proposed, which introduces a stochastic component into the disturbance dynamics. Second, an approach based on a stochastic electrical power generation model is considered. This model is based on PV data and incorporates information about the seasons and the type of the PV generation units.

The paper deals with the use of the Huang Hilbert Transform (HHT) for the analysis of transient signals in non linear circuits. Differently from traditional methods that decompose a signal as the sum of apriori adopted waveforms, HHT procedure decomposes the signal of interest in oscillatory modes aposteriori determined, in dependence on the signal characteristics, giving, thus, a better information about the physical characteristics of the observed system.
The performance of the proposed analysis method has been evaluated by applying the HHT to the current acquired from an actual RLC circuit during its free natural oscillation. The circuit involves a saturable inductor, therefore the HHT capability of providing physically meaningful information accounting for both non stationarity and non linearity has been appreciated.

Paper presents a study under the Quality of Service in modern wireless sensor networks. Such a networks are characterized by small amount of data transmitted in fixed periods. Very often this data must by transmitted in real time so data transmission delays should be well known. This article shows multimode network simulated in packet OPNET Modeler. Also nowadays the quality of services is very important especially in multi-nodes systems such a home automation or measurement systems.

The purpose of this paper is to show as the optimal linear filtering of measurements during calibration of the instrument can simultaneously consider the factors that affect the accuracy of estimates. The Kalman filter or linear quadratic estimation allows taking into account the previous changes of the device characteristics, the correlation between the points in the measurement range and working space.