This paper presents a computationally efficient method for modelling an impact of the converter drive on the power grid. The formalized variable structure method (FVSM) allows for comprehensive studies of the effect on the power grid and examining the relation between this effect and the number of drive and feeding line parameters. In order to obtain a comprehensive model along with the model of the power grid, the parameters that are applied originate from a drive of a coal-fired power station. These parameters have been determined based on assessment and estimation. The estimation process was conducted with the aid of a model that allows for the commutation of power electronic elements. The authors confirmed that the model was correct by comparing empirical and theoretical voltage and current waveforms. Harmonic content of the voltage and current in the power grid which feeds the drive are considered to be the measure of the converter drive impact on the power grid. The standard method for the reduction of a harmonic content in the voltage and current involves the application of line reactors and distribution or converter transformers. As an example, the authors determine the impact of the drive on the power grid with respect to the adopted parameters of the line reactor. This example presents FVSM abilities with regard to simulation of complex systems that contain power grid components and converter drives.
The aim of the presented work was to examine the reliability assessment model on the example of a selected power grid object. The analyzed object was tested based on assumptions about technological breaks that were caused by overvoltage, among others. The study was conducted to check the reliability of integral elements of the power grid object and to assess the change in reliability level as a function of the frequency of inspections. The test results are to determine the optimal frequency of inspections of individual power grid objects in order to increase its reliability. In addition, the possibility of correlating optimal inspection periods resulting from the findings of this paper with periodic inspections of power network facilities was assessed.
The paper looks at the issues of operation safety of the national power grid and the characteristics
of the national power grid in the areas of transmission and distribution. The issues of
operation safety of the national transmission and distribution grid were discussed as well as threats
to operation safety and security of the electricity supply related to these grids. Failures in the
transmission and distribution grid in 2017, caused by extreme weather conditions such as: a violent
storm at the night of 11/12.08.2017, hurricane Ksawery on 5–8.10.2017, and hurricane Grzegorz on
29–30.10.2017, the effects of which affected tens of thousands of electricity consumers and led to
significant interruptions in the supply of electricity were presented. At present, the national power
(transmission and distribution) grid does not pose a threat to the operation safety and security of
the electricity supply, and is adapted to the current typical conditions of electricity demand and the
performance of tasks during a normal state of affairs, but locally may pose threats, especially in
extreme weather conditions. A potentially high threat to the operation safety of the national power
grid is closely linked to: age, technical condition and the degree of depletion of the transmission and
distribution grids, and their high failure rate due to weather anomalies. Therefore, it is necessary
to develop and modernize the 400 and 220 kV transmission grids, cross-border interconnections,
and the 110 kV distribution grid (especially in the area of large urban agglomerations), and the MV
distribution grid (especially in rural areas). The challenges faced by the transmission and distribution
grid operators within the scope of investment and operating activities, with a view to avoiding
or at least reducing the scale of grid failures in the case of future sudden high-intensity atmospheric
phenomena, are presented.
The effectiveness of lightning protection on the power and distribution grid is a significant factor, which influences the power distribution reliability and the failure rate of system elements. As part of this article, a mathematical model will be presented, taking into account selected parameters that affect the assessment of the lightning hazard of an overhead line. The proposed model will consider the location of the object near the line and the adjustment of line conductor overhangs. Moreover, the mentioned mathematical model allows for analyzing the impact of considered parameters on the protection level of the power system, and transient overvoltages that occur in this system. The article contains also a detailed description of an effective and fast method to assess the lightning discharge impact on the power system with insufficient data. The introduced model was tested to verify the correctness of its operation by comparison of calculation results and functional data. High convergence of calculated and functional data and uncomplicated model structure ensure a wide range of applications for the proposed solution to easily prevent emergency situations in the power system. Furthermore, the described model gives the opportunity to assess the reduction of the range of selectivity zone associated with the power line, in conjunction with the impact of constructional peculiarities and a near object.
We introduce seven new versions of the Kirchhoff-Law-Johnson-(like)-Noise (KLJN) classical physical secure key exchange scheme and a new transient protocol for practically-perfect security. While these practical improvements offer progressively enhanced security and/or speed for non-ideal conditions, the fundamental physical laws providing the security remain the same.
In the "intelligent" KLJN (iKLJN) scheme, Alice and Bob utilize the fact that they exactly know not only their own resistor value but also the stochastic time function of their own noise, which they generate before feeding it into the loop. By using this extra information, they can reduce the duration of exchanging a single bit and in this way they achieve not only higher speed but also an enhanced security because Eve’s information will significantly be reduced due to smaller statistics.
In the "multiple" KLJN (MKLJN) system, Alice and Bob have publicly known identical sets of different resistors with a proper, publicly known truth table about the bit-interpretation of their combination. In this new situation, for Eve to succeed, it is not enough to find out which end has the higher resistor. Eve must exactly identify the actual resistor values at both sides.
In the "keyed" KLJN (KKLJN) system, by using secure communication with a formerly shared key, Alice and Bob share a proper time-dependent truth table for the bit-interpretation of the resistor situation for each secure bit exchange step during generating the next key. In this new situation, for Eve to succeed, it is not enough to find out the resistor values at the two ends. Eve must also know the former key.
The remaining four KLJN schemes are the combinations of the above protocols to synergically enhance the security properties. These are: the "intelligent-multiple" (iMKLJN), the "intelligent-keyed" (iKKLJN), the "keyed-multiple" (KMKLJN) and the "intelligent-keyed-multiple" (iKMKLJN) KLJN key exchange systems.
Finally, we introduce a new transient-protocol offering practically-perfect security without privacy amplification, which is not needed in practical applications but it is shown for the sake of ongoing discussions.
Distributed generation is an issue intensively studied in recent years. It concerns, among others protection systems of distributed generation units connected to electric power grids. The main goal of this paper is to present the issue of functional reliability of selected passive loss of mains (LoM) protection systems, i.e. methods of detecting island operation in distribution power grids, which are implemented in PV inverters installed in sample MV and LV grids, typical for Polish conditions. First, different methods of detecting island operation have been distinguished and shortly characterized. Some problems concerning their action have also been presented. Then commonly used passive methods of island grid operation detection have been described. Next sample distribution grid has been presented and chosen disturbances modelled in the grid to test mentioned passive methods have been defined. For each of the determined type of disturbance the dynamic simulation has been carried out, as well as voltage and frequency plots for two selected RES nodes have been recorded and observed. All considered passive methods of island grid operation detection have been implemented in a Matlab/Simulink environment. Models of RoCoF, U/OVP and U/ OFP algorithms have been presented in diagrams. Then, results of carried out extensive studies have been shown in tables and discussed. The results are a consequence of a realized research project concerning electric grids in rural areas. Summary, final conclusions, and future research possibilities constitute the last part of the paper. The conclusions are mainly concentrated on evaluation of action of passive methods of island operation detection as well as possibility of using the methods in Polish conditions, particularly in rural distribution grids.