Directional relays based on digital phase comparator

[Z. Stojanović]

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Elektrotehnika - Elektroenergetski sistemi / Electrical engineering - Power Systems

U ovoj doktorskoj disertaciji predstavljen je nov algoritam za usmereni relej baziran na digitalnoj faznoj komparaciji. Za realizaciju digitalnog faznog komparatora pošlo se od ideje da se ne računa fazni pomeraj između struje i referentnog napona, već energija odnosno integral trenutne snage signala na intervalu dužine polovine osnovne periode napona ili struje. Interval integracije je polovina osnovne periode jer je frekvencija trenutne snage dva puta veća u odnosu na frekvenciju ulaznih signala. Algoritam usmerenog releja koji se bazira na integralu trenutne snage signala ima osobine faznog komparatora. Podešavanje maksimalne osetljivosti releja vrši se direktno iz naponskog ili strujnog registra. U odnosu na dosadašnja rešenja, ovakvim pristupom eliminisana je potreba za impedansom modela voda Zm. Izlaz koji generiše usmereni relej ograničen je na intervalu ±1, deljenjem srednje snage signala prividnom snagom. Na taj način omogućeno je jednostavno zadavanje praga reagovanja ili blokiranja releja, koji je različit od nule. Opisani postupak u proračunima koristi samo jednostavne matematičke operacije (sabiranje, množenje i deljenje) zbog čega u maloj meri koristi procesorsko vreme. Zbog postojanja viših harmonika i jednosmerne komponente u ulaznim signalima algoritam je u nastavku proširen digitalnim Fourierovim filtrom. To je otvorilo mogućnost regulacije osetljivosti releja korišćenjem sinusne i kosinusne komponente Fourierovog reda. Brzina reagovanja releja zavisi od režima koji je prethodio kvaru i podešenog praga reagovanja. Kreće se od trenutnog dejstva do 10 ms, što relej svrstava u one sa brzim odzivom. Opisani algoritam može umesto trenutnih vrednosti signala da koristi njihove priraštaje čime se dobija ultrabrzi usmereni relej. Vreme odziva ovog releja je manje od 5 ms i nema zonu neosetljivosti. U nastavku disertacije izloženo je nekoliko specifičnih primena digitalnog faznog komparatora na realnim problemima. Svaki od algoritama detaljno je testiran serijom računarski generisanih signala...

In this doctorial dissertation, a new algorithm for directional relay based on digital phase comparison is presented. The basic idea for realization of digital phase comparator is as follows: instead of calculating phase shift between the reference voltage and current, this algorithm calculates energy i.e. integral of the instantaneous power over one half-period of the voltage or current signal. The integration interval is the half-period because the frequency of the instantaneous power is two times higher than the frequency of the input signals. The algorithm for the directional element based on the integral of instantaneous power possesses the features of the phase comparator. The adjustment of relay sensitivity is performed directly from voltage or current register. In comparison to existing solutions, this approach eliminates the necessity for the line or network model impedance Zm. The output signal, generated by the directional element is limited to interval ±1, by division of the average signal power with the apparent power. This way, the tripping or blocking threshold setting different than zero is enabled. The described procedure uses only simple mathematical operations (addition, multiplication and division) for calculations resulting in small CPU time occupation. Due to existence of higher harmonics and/or direct component in input signals, the algorithm is extended by Fourier filter. This opened a possibility for rough regulation of the relay sensitivity by using only sine or cosine component of the Fourier series. The relay tripping time depends upon the regime before the fault occurrence and the adjusted tripping threshold. It varies from the instantaneous tripping to 10 ms so the relay is characterized by high speed of response. Instead of instantaneous values of the input signals, the described algorithm can use their increments and therefore further increase the speed of response. The tripping time of this relay is less than 5 ms and operates without dead tripping zone. In the following chapters of dissertation, several specific applications of digital phase comparator on practical problems are investigated. Each algorithm is tested in detail with the series of computer-generated signals...

relejna zaštita, digitalni releji, usmereni releji, fazni komparator, usmerena zemljospojna zaštita

relay protection, digital relaying, directional element, phase comparator, directional earth-fault protection

621.318

Usmereni releji

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