Transients in no-load condition of power transformer 20/0,4 kV

Ovaj rad predstavlja inovativan pristup u analizu prijelaznih pojava u elektroenergetskom sustavu korištenjem novopredloženih načina obrade podataka dobivenih iz procesora ugrađenog u moderne zaštitne releje u elektroenergetskom sustavu. Prijelazne pojave se precizno registriraju tijekom uključivanja energetskog transformatora i puštanja u prazni hod. Analizirani su energetski transformatori 20/0,4 kV u TS 110/20 kV Osijek-4 koji služe za opskrbu električnom energijom vlastitih potreba transformatorske stanice. U radu su grafički prikazani vremenski odzivi glavnih električnih parametara kao i Fourierova analiza viših harmonika.Innovative approach in power system transient analysis is presented in the paper, applying a new proposed method to process data obtained from processor built in modern protection power relays. The transients, described here appeared precisely while turning the power transformer on and setting it in the no-load condition. The analyzed power transformers 20/0,4 kV are installed to meet the auxiliary needs of the transformer substation TS 110/20 kV Osijek-4 with electric power. Time response graphic presentations of main power parameters and Fourier analysis of higher harmonics are presented in this paper

Measurement Procedure for Commercial Loss Reduction in a Distribution Power System

Total power losses in a power system consist of technical losses and commercial losses. Commercial losses are 30-40 % of total losses and appear as a result of unreliable measurement devices for electricity registering and wilful unauthorised consumption of electricity. It is almost impossible to find illegal connections in a distribution power system due to hidden main power cables in the house walls or underground. A proposed and elaborated measurement procedure based on time domain reflectometer successfully solves the problem described

Postupak za određivanje harmonične distorzije uzduž distribucijske mreže

This paper underlines the importance of permanent power quality measures in distribution network and proposes the interval and event (change in topology) based time schedule of measurements in depth of the network. Some nodes do not need to be measured during 7 days according to EN 50160 to realize that there are great problems to solve in a new technical resolution. Similar to the trend of entropy, true harmonic distortion (THD) in distribution power system is expected to increment, so - momentary measures are sufficient to mark subparts of the power system with unsatisfactory level of power quality. The most important problem to solve is to mark the consumer\u27s generated harmonic distortion. Importance and benefit of the proposed method is to save the time needed to name causes of disturbances (consumer or device) and to anticipate the repairing of power quality. A new flow-chart is suggested for recognition of the consumer THD generation amount. Also, it leads to better technical or managing decision making during maintenance and investment planning activities. Further results of systematic planned measures that need to be done along the distribution power network, will enable global recognition of THD causes in network and simultaneously give exact solutions.Ovaj članak naglašava važnost stalnog mjerenja kvalitete električne energije u distribucijskoj mreži i predlaže vremenski raspored mjerenja po dubini mreže određen vremenskim intervalom ili događajem (promjena u topologiji mreže). Neki čvorovi ne moraju biti stalno mjereni tijekom 7 dana prema normi EN 50160 da se zaključi da postoje veliki problemi vezani za kvalitetu za novo stanje mreže koje treba riješiti. Slično kao ponašanje entropije, za udio harmoničnog izobličenja (THD-a) u distribucijskoj mreži očekuje se da isključivo raste tako da su trenutačna mjerenja dovoljna da se označe dijelovi distribucijskog sustava koji nemaju zadovoljavajuću razinu kvalitete. Najvažniji problem kojega treba riješiti je odrediti kupca koji proizvodi harmonično izobličenje. Važnost i korisnost predložene metode je ušteda vremena za određivanje uzroka poremećaja (kupca ili uređaja) kao i za predviđanje načina za poboljšanje kvalitete električne energije. Predložen je novi dijagram toka za prepoznavanje količine proizvedenog THD-a od strane određenog kupca. Također, uporabom ove nove metode mjerenja kvalitete olakšava se donošenje odluka u tehničkom i organizacijskom segmentu tijekom aktivnosti održavanja i planiranja investicija. Daljnji rezultati sistematski planiranih mjerenja uzduž distribucijske mreže omogućit će globalno prepoznavanje veličine uzroka harmoničnog izobličenja i istovremeno dati određena rješenja

Utjecaj vjetroelektrana na rad elektroenergetskog sustava – 1. dio: Pogon vjetroelektrana i kriteriji priključenja na mrežu

For the purpose of a comprehensive review of power system operation with the connection of wind power plants, this review is presented in two articles. The first article presents the main concepts of wind power plants, technical possibilities of wind power plant operation and all requested criteria for connecting the wind power plant to the power system. In the second article the power quality after connecting wind power plant to the distribution network, energy losses in distribution network with connected wind power plant and feasibility and development of electrical energy production with wind power plants in the power system of the Republic Croatia are considered.Zbog sveobuhvatnosti pregleda rada elektroenergetskog sustava s priključenim vjetroelektranama pregled se prikazuje u dva članka. U prvom članku prikazani su osnovni pojmovi o vjetroelektranama, tehničke mogućnosti pogona vjetroelektrana i svi zahtijevani kriteriji priključenja vjetroelektrane na elektroenergetski sustav. U drugom članku razmatra se kvaliteta električne energije nakon priključenja vjetroelektrane na distribucijsku mrežu, gubici energije u distribucijskoj mreži s priključenom vjetroelektranom, te mogućnost proizvodnje i razvoj proizvodnje električne energije s vjetroelektranama u elektroenergetskom sustavu Republike Hrvatske

Experimental Testing of PV Module Performance

This study compares the manufacturer\u27s technical data of several PV modules with real measured outdoor technical data. The irradiance effect on several PV modules is examined by the changing a tilt angle and comparing different meteorological situations of sky clearness (clouds) on the modules mounted outdoor and exposed to Sun. Also, the influence of temperature and dust on the performance of a PV panel is under research using measurement methods described in the paper. The measured current and voltage data at the clean surface of the PV module correspond to the declared data of the PV module manufacturer, and in the case of fouling of the module surface with dust, a power drop of 7.39% was measured

A New Protection System Design of Active MV Distribution Network

The increasing implementation of renewable energy sources (RES), along with the diversity of energy source types, has additionally imposed significant operational and management problems in distribution networks. These problems are manifested in voltage regulations, system stability and coordination of protection, both in the distribution and transmission networks. For the medium voltage (MV) network, this includes new energy sources and higher amounts of fault currents, invisibility of several faults in the existing protection scheme, reduction of the range of protection devices and reduction of the possibility of detecting small fault currents with existing protection relays. Such changes significantly reduce the possibility of proper distribution system protection, both in subordinate and superior networks. The subject of this paper is the presentation of a new concept of the use of automation in the management and arrangement of power system protection dependent on the scheme and configuration of an active MV network. The goals of this analysis and research are to find and define the necessary architecture in which the scheme and appearance of the MV network should be automatically detected, and based on network topology to establish new settings of protection devices (ground fault, overcurrent and short circuit protection). The contributions of generation units of RES in the MV network must be considered. This paper specifically analyses the problems of power system management with simultaneous harmonization of protection systems both in the transmission and in the radial distribution network, offering optimization algorithms that have the ability of achieving the optimal solution. The implementation of the proposed technique was tested on a radial connection integrated with a microgrid (MG) which has the possibility of two-way power supply. The obtained results indicate that the proposed technique can solve described problems in the coordination of protection system and network management, even with the dynamic character of operation mode of the networks

Air Quality Supervision System using the IoT Platform

This paper presents the idea of the Internet of Things (IoT) platform, which is demonstrated by creating a device that measures air quality, collects and processes real-time data, and presents it in a web application. The device comprises a microcontroller board called Wemos D1 Mini, which is powered by an ESP8266 microchip. It also consists of two sensors, CCS811, which measures air particle quantity, and BME280, which measures air temperature, pressure, and humidity. The device is wirelessly connected to an MQTT broker using a Wi-Fi network and the MQTT protocol. The paper also provides detailed information on the functioning and usage of the MQTT protocol along with guidelines for programming and configuring the MQTT broker for both Wemos D1 and Raspberry Pi

Analysis of Transitional Occurrences of Low Voltage Welding Transformer

The purpose of this paper is to demonstrate and analyse transition events that occur when the loaded transformer is turned on and off within the welding device. The purpose of the welder is to provide a high quality and stable voltage during the ignition of the arc, and often during the ignition of the arc the transformer comes from its no-load state to the work-load state, depending on the diameter of the electrode that the arc melts. The welding currents of the MIG/MAG (Metal Inert/Active Gas) process are not less than 100 A, about 350 A, at a voltage of the arc of 35 V (DC). In this paper, the MATLAB/PSB programme package is used to analyse the no-load inrush currents and the loaded inrush currents of welding transformers. Current and voltage waveforms were recorded on the primary side of the transformer, as well as the harmonic content of the transformer primary currents, with indicator calculation of the current waveform distortion - THDi

Monitoring and Regulation of Indoor Conditions

This paper presents research of energy performance analysis performed by Building Energy Management System (BEMS). BEMS is a system/platform integrated with building and it is an enormous improvement in a process to develop nearly zero energy buildings (nZEB). Near zero energy consumption stands for energy efficient idea of energy independent buildings for their function during their life time. Here, BEMS with function of monitoring and regulation of cooling energy demand is developed. BEMS regulates function of ventilation fan in area below tin roof and improves working conditions by inside building temperature reduction during summer period. Described technical solution is designed inside RESCUE IPA CBC project

System Control and Data Acquisition of University Photovoltaic Power Plant

The paper deals with design of System Control and Data Acquisition (SCADA) of Photovoltaic power plant FERIT 1, its configuration and connection with server unit for data archiving and removal approach by either android or PC devices. SCADA is developed according to ideas and need for scientific research of data generated by photovoltaic power plant built on the roof of the Faculty of Electrical Engineering, Computer Science and Information Technology Osijek in Osijek, Croatia. Designed system enables real-time analysis and of course subsequent time analyses based on storing data of high frequency measurement samples of photovoltaic (PV) power plant. The first part of the paper describes hardware components and system configuration and the second part deals with software background. Measurements of PV parameters and meteorological conditions are continuously performed, and these data are stored locally and instantaneously stored also on remote servers. Acquired measurement data is presented by graphics on developed web server platform. Developed SCADA presented in the paper is unique, adaptable open source which enables long-term performance of power plant and its components\u27 function