Model diferenčne zaščite energetskega transformatorja na srednjenapetostnem nivoju omrežja

KOBE, TJAŠA (author), Pantoš, Miloš (mentor)

Za zaščito primarne opreme elektroenergetskega omrežja namestimo v sistem zaščitne releje. Njihov namen je zmanjšanje vpliva okvar na delovanje omrežja in preprečevanje škode na opremi ter posledično nastalih stroškov. Diferenčna zaščita je ena izmed najpomembnejših funkcij releja. Preverja tok na primarni in sekundarni strani ščitenega elementa, ki mora biti po 1. Kirchhoffovem zakonu enak. Ob preveliki razliki tokov se zaščita aktivira, razklene odklopnike in izklopi element iz omrežja. Oblikovali smo model diferenčne zaščite energetskega transformatorja na srednjenapetostnem nivoju. Energetski ali močnostni transformatorji pretvarjajo primarno napetost v določenem razmerju na sekundarno in so eden izmed najpomembnejših in najdražjih elementov elektroenergetskega sistema. Njihova zaščita mora biti zato zanesljivo načrtovana in izvedena. Algoritem smo razvili s pomočjo simulacijskega paketa Simulink v Matlabu. Upoštevali smo relevantne moteče dejavnike, ki se pojavljajo v transformatorju (vklopni toki, prevzbujanje transformatorja in nasičenje tokovnih transformatorjev). Prepoznavali smo jih z metodo, ki temelji na harmonski analizi diferenčnega toka in primerno izničili njihov vpliv na zanesljivo delovanje zaščite. Simulirali smo odziv našega algoritma na okvare znotraj in zunaj ščitenega območja. Opazovali smo vpliv nasičenja tokovnikov na ustrezno aktivacijo zaščite in ugotovili, da kljub podaljšanemu odzivnemu času zadostimo kriteriju časovnih omejitev. V zaključku smo navedli še predloge za nadaljnje izboljšave razvitega algoritma.

• Language: Slovenian
• Keywords: diferenčna zaščita, energetski transformator, tokovni transformatorji, nasičenje
• Work type: Master's thesis/paper
• Organization: FE - Faculty of Electrical Engineering
• Year: 2018
• PID: 20.500.12556/RUL-101318
• Publication date in RUL: 28.05.2018

Secondary language

• Language: English
• Title: A model of differential protection of a power transformer on a medium voltage network

Abstract

In order to protect the primary equipment of electricity networks, we install protection relay systems. These aim to minimize the impact of failures on network operation, prevent damage to the equipment and consequently reduce the costs. Differential protection is one of the most important functions of protection relays. It compares the currents on the primary and secondary sides of the protected element, whose sum must be close to zero according to the 1st Kirchhoff's law. In case of big differential current the protection is activated and causes the disconnection of the protected element from the network. We developed a model of differential protection for a power transformer at a medium voltage level. Power transformers convert primary voltage in a given ratio to secondary one, and are among the most important and expensive elements of a power system. Therefore, their protection must be properly planned and implemented. Our algorithm was developed using Simulink, the simulation package in Matlab. We took into account the relevant interfering factors that occur in power transformers (inrush currents, overexcitation conditions and current transformer saturation). These were identified with a method based on harmonic analysis of differential current. Their influence on reliability of the protection was adequately eliminated. We simulated the response of our algorithm on failures within and outside of the protected zone. We observed the influence of current transformer saturation on protection activation, and demonstrated compliance with time requirements. Finally, we provided recommendations for further improvements of the developed algorithm.

• Keywords: differential protection, power transformer, current transformer, saturation