Current Transformer Saturation Detection with Genetically Optimized Neural Networks

Application of the genetic algorithm (GA) for optimization of artificial neural network (ANN) based CT saturation detector is presented. To determine the most suitable ANN topology for the CT state classifier the rules of evolutionary improvement of the characteristics of individuals by concurrence and heredity are used. The proposed genetic optimization principles were implemented in MATLAB programming code. The initial as well as further consecutive network populations were created, trained and graded in a closed loop until the selection criterion was fulfilled. Various aspects of genetic optimization have been studied, including ANN quality assessment, versions of genetic operations etc. The developed optimized neural CT saturation detector has been tested with EMTP-ATP generated signals, proving better performance than traditionally used algorithms and methods

Short-Circuit Current Contribution from Large Scale PV Power Plant in the Context of Distribution Power System Protection

The interconnection of distributed generators (DG) to existing network may give rise to many technical problems. To ensure appropriate power quality and stability of the grid these problems should be recognized and solved. For this purpose, behaviour of such energy sources, under various disturbances, must be studied and known to the distribution grid operators. In this paper fault current contribution from large scale photovoltaic (PV) power plant as well as protection issues concerning such DGs are discussed. The mentioned problems were investigated in PSCAD model of 50 MW grid--connected PV power plant where various operating condition of the network and penetration levels of PV were considered

Solutions for integrating agglomeration railways with other modes of transport on the example of the Łódź Metropolitan Railway (ŁKA)

Artykuł przedstawia przykłady rozwiązań integrujących system kolei aglomeracyjnej z innymi systemami transportowymi, jakie wdrożono w województwie łódzkim. Łódzka Kolej Aglomeracyjna (ŁKA) jest systemem kolei aglomeracyjnej uruchomionym w województwie łódzkim w 2014 roku w pięciu promienistych relacjach: Łódź – Zgierz/ Kutno/ Sieradz/ Koluszki/ Łowicz Główny. Od tego czasu oferta przewozowa ŁKA systematycznie jest rozwijana: otwierane są nowe połączenia kolejowe, zwiększana jest praca przewozowa, jak również doskonalona jest jakość świadczonych usług, m.in. poprzez integrację kolei z innymi systemami transportowymi. Wartymi szerszej uwagi, jak również zaadoptowania w innych rejonach w kraju, są rozwiązania z zakresu integracji taryfowej, a wręcz wspólne honorowanie biletów kolejowych i publicznego transportu zbiorowego, integracja kolejowo-autobusowa przeciwdziałająca wykluczeniu transportowemu, czy też integracja kolei z systemem rowerów publicznych. Zaprezentowane rozwiązania są tym bardziej ciekawe, że niekoniecznie mają one charakter punktowy, a systemowy.This article presents examples of solutions integrating the agglomeration railway system with other transport systems that have been implemented in the Łódź Voivodeship. Łódź Metropolitan Railway (ŁKA) is an agglomeration railway system launched in the Łódź Voivodeship in 2014 with five radial routes: Łódź – Zgierz/ Kutno/ Sieradz/ Koluszki/ Łowicz Główny. Since then, ŁKA’s transport offer has been systematically developed: new train connections have been opened, transport workload has been increased, and the quality of services has been improved, including through the integration of railways with other transport systems. Solutions in the area of tariff integration, or even joint honouring of rail tickets and public transport tickets, rail-bus integration counteracting transport exclusion or integration of railways with the public bicycle system are worth wider attention and adoption in other regions of the country. The presented solutions are all the more interesting, as they are not necessarily point-topoint, but systemic in nature

Ultrasaturation Phenomenon in Power Transformers—Myths and Reality

In this paper, the ultrasaturation phenomenon of power transformers during their energization is studied. It is shown that under special conditions, the currents observed after transformer switching on do not contain enough restraining information (e.g., second harmonic), which may lead to protection maloperation. This paper concentrates on a thorough explanation of the problem and possible causes of ultrasaturation. Theoretical investigations are supported and illustrated with simulation studies performed both with MATLAB and Electromagnetic Transients Program–Alternative Transients Program. The outcomes of this research can further be used as hints for substation operation personnel as well as for the development of new protection stabilization criteria, which is not discussed further in this paper

A Case Study on Distributed Energy Resources and Energy-Storage Systems in a Virtual Power Plant Concept: Technical Aspects

The article presents calculations and power flow of a real virtual power plant (VPP), containing a fragment of low and medium voltage distribution network. The VPP contains a hydropower plant (HPP), a photovoltaic system (PV) and energy storage system (ESS). The purpose of this article is to summarize the requirements for connection of generating units to the grid. Paper discusses the impact of the requirements on the maximum installed capacity of distributed energy resource (DER) systems and on the parameters of the energy storage unit. Firstly, a comprehensive review of VPP definitions, aims, as well as the characteristics of the investigated case study of the VPP project is presented. Then, requirements related to the regulation, protection and integration of DER and ESS with power systems are discussed. Finally, investigations related to influence of DER and ESS on power network condition are presented. One of the outcomes of the paper is the method of identifying the maximum power capacity of DER and ESS in accordance with technical network requirements. The applied method uses analytic calculations, as well as simulations using Matlab environment, combined with real measurement data. The obtained results allow the influence of the operating conditions of particular DER and ESS on power flow and voltage condition to be identified, the maximum power capacity of ESS intended for the planed VPP to be determined, as well as the influence of power control strategies implemented in a PV power plant on resources available for the planning and control of a VPP to be specified. Technical limitations of the DER and ESS are used as input conditions for the economic simulations presented in the accompanying paper, which is focused on investigations of economic efficiency