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It is common in engineering to model time-dependent variables as diffusion process represented by stochastic differential equations. This is usually helpful when empirical datasets describing time evolution of variables are available. This helps in accurate estimation of parameters of the stochastic differential equation which describes the dynamic system. Additionally, it helps in characterization...
This paper deals with the solution of transient phenomena during the connection of the photovoltaic power plants. There was investigated the impact of the failure of current protection for renewable energy sources during the network disconnection. There was verified the possibility of network operation during the islanding operation. Failure of network protection represents the significant hazard...
This work proposes different methods to calculate the sensitivity of system parameters based on graphic analysis. From percentages variations in base values of the parameters, one-at-a-time measures are taken to the construction of a graph that expresses the impact on the output caused by variations in the inputs. Two case studies are proposed, with simulated and experimental data, in which the proposed...
Predictive maintenance of high voltage devices is a major issue for all power providers, due to costs and complexity. This article provides some theoretical and experimental principles which can be useful for all maintenance operations performed on high voltage switching devices and some simple methods applicable for assessing the status of all their contacts. Some of the aspects described here are...
Island operation possibility plays nowadays an important role in the view of preserving a part of the power system working during close-to-blackout emergency states such as collapsing power system divided in to smaller parts. Unfortunately following paper shows that not all regulation tools available for the transmission system operator (TSO) which are secured by the national grid code might be used...
The insulating liquids for power transformers are still evolving area. The current trend is to move away from currently used mineral oil because it poses a threat to the environment and use the renewable, biodegradable nature ester oils instead. These oils are now well known but what keeps them from widespread usage are unbalanced properties. In some areas these natural oils excel (fire point, sulfur...
The process of insulation coordination of power systems is conditioned by a number of factors, among which the improvement of methods of surge analyses occupy a special position. The use of statistical procedures in coordination of insulation of overhead power lines requires knowing statistical distributions of surges and reliability of their parameters. Establishing the type of distribution and the...
The purpose of this work is to develop devices capable of identifying sign language characters and comparing them in order to verify layout with better accuracy and robustness. The recognition is performed using Artificial Neural Networks and all the input data are signals from flex sensors, accelerometers and gyroscopes, positioned differently on each device. After being trained, validated and tested,...
Natural oils are divided into vegetable and mineral oils. Compared with vegetable oils, the mineral oils show better dielectric properties, however, they are rather dangerous for the living environment and their flammability is higher. The vegetable oils are composed of natural ester molecules with a triacylglycerol structure. The mineral oils are a mixture of hydrocarbons produced from crude oil...
Most of the electricity produced in nuclear power plants comes from pressurized water nuclear reactors. Currently, the main fuel of pressurized water nuclear reactors is enriched uranium. The thermal energy is produced by fission of uranium 235 using slow (thermal) neutrons. Generation IV reactors are already contemplate obtaining thermal energy from the fission of uranium 238 using fast neutron....
Any failure of a power transformer can result in serious consequences for a power system. Bushing failures, mechanically damaged windings or deterioration of solid insulation may cause unexpected power line cut-offs and financial losses to a company. Faulty operation of the on-load tap changer (OLTC) caused by increased contact resistance, contact misalignment or broken drive mechanism also reduces...
The train velocity is needed to be known for many purposes like the train safety systems or a slip control. The train velocity is typically determined from wheelsets velocity. The wheelset velocity is different with the train velocity due to a slip velocity that is needed for a force transmission between wheels and rails. The train velocity measured by this way is the only estimation of the train...
This paper deals with the operating of so called low-cost lighting systems fitted with LED light sources. The reason for drawing up the paper was a notification of qualitative changes in luminous flux of implemented lighting systems. It is currently possible to produce relatively cheap LED luminaires fitted with available white LED. Since the low-priced LED go hand in hand with their qualities, these...
Direct torque control (DTC) is one of the best performing strategies for induction motor control in many applications. However, this method suffers from a few disadvantages. Very important one is the presence of ripples in the torque waveform. The main reason of their presence is the inaccurate model of the motor. This paper utilizes Luenberger observer to calculate the model of the motor instead...
This paper is focused on the description of phenomenon called "floating water bridge" and several experiments in our high voltage laboratory which are joined with this phenomenon. Water bridges bring some new knowledge in chemistry, electrochemistry, lighting technology and high voltage field. In this paper we will be dedicated space for describing the properties of water bridges in the...
This paper is a contribution to solid air exhale analysis, regarding to outer insulation design. It describes the method of exhale collection, their composition measurement and their chemical analysis. Further proposals are made in conclusion for solid exhale analysis.
The pollution of external insulation of power equipment has a significant impact on the lifetime of electrical equipment. The paper is focused on the possibility of using monitoring leakage current through the external insulation of hv surge arresters as indicator of pollution. In the experiment the modified procedure for the preparation of the polluting layer was used. The leakage current on the...
Evaluation of current-carrying capacity of power cables and selection of cross-sectional area of their conductors are mainly performed in accordance with requirements of EN, IEC or IEEE standards. However, these standards do not provide all methods of cables installation and location which occur in practice. Thus, in some cases, performance of advanced modeling of various thermal phenomena, affecting...
Harmonic voltage compensation of the load connected to the point of common coupling (PCC) by using a series of active power filter (SAPF) based on a single phase cascaded multilevel inverter is proposed. The proposed multilevel inverter are presented in detail. The inverter has the ability of acting as a harmonic source when the reference is a non-sinusoidal signal. To achieve this, a simple control...
This paper is focused on challenges related to an increased quantity of distribution energy resources connected to the distribution network within the context of newly defined requirements ENTSO-E, follow-up European standards TS 50549 and codes of distribution system operators on regulation of voltage through control of the reactive power in terms of P-Q diagram. A high number of connected and operated...
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