Special protection scheme for operation of central Zagreb transmission system

The paper presents a Special Protection Scheme solution for the central Zagreb transmission system. The Central Zagreb transmission system is characterized by a highly meshed network with combined overhead and cable sections and a special operation of the 110 kV cable link between two power plants important for the city’s heat and electricity supply. The Special Protection Scheme is developed using static and dynamic analyses of different network scenarios. Island operation is simulated for a consumption and generation surplus, and an underfrequency load shedding scheme is determined. The Special Protection Scheme architecture is presented with a brief description of the telecommunication infrastructure

Synchronized Measurements Processing Methodology as a Tool for Monitoring Power System Oscillations

Monitoring, protection and control of the electrical power system require the design and implementation of specific applications that are based on analytical methods for the processing of synchronized measurements. Therefore, it is necessary to select the adequate type of mathematical analysis that best suits the requirements of a particular application. This paper describes analytical methods used for the processing of synchronized measured electrical quantities for detection and analysis of the variety of oscillations. The oscillatory phenomena of active power and frequency as a case study of one disturbance in the power system are analyzed. The results of processing the actual synchronized measurements for that case study are presented afterwards. Different data processing methods (spectral analysis methods) are compared, and finally, a recommendation for appropriate methods for processing synchronized measurements in application for recognition, processing and alarming of oscillations of active power is given

Efficiency Considerations and Application Limits of Single-Phase Active Power Filter with Converters for Photoenergy Applications

A new way of connecting PV sources to adaptive voltage active power filter (AV APF) has been compared with classic approach including active power filter (APF). In standard active power filter applications a relatively high DC link voltage (500 V or even more) with a buck converter or lower voltage (approx. 100 V) with boost converter can be used. These two converters appear also in adaptive voltage circuit of AV APF, but in this case it is possible to achieve many different connections of DC source. Benefit of this approach is that the same circuit is used for improving switching conditions in APF and for connection of solar cells. It appears that these two functions support each other and a large variety of DC voltages and currents can be connected to AC mains. Experimental results confirm expectations of increased energy transfer from additional DC source to network, especially for DC voltages being lower than DC link voltage

A State Estimator Using SCADA and Synchronized Phasor Measurements

A state estimator is presented, in which conventional measurements from the SCADA system and synchrophasors available from Phasor Measurement Units (PMUs) are used. A recursive algorithm for the part of the system observable by PMUs is applied, in which multiple sets of synchrophasors are processed. The obtained state estimate is then used together with SCADA measurements in an iterative procedure to estimate the state of the entire power system. The developed methodology was tested on IEEE test systems with 30 and 57 buses as well as on the model of the Croatian transmission system. The proposed solution is comparable in convergence with the classical state estimator and other hybrid models, whereas it enhances state estimation accuracy and filtering of measurement errors

Selectivity of protection devices in auxiliary DC installations

Sustav istosmjernog razvoda u elektroenergetskim postrojenjima je od velike važnosti jer omogućava pouzdano vođenje elektrane i transformatorske stanice kako u normalnom pogonu, te također u slučaju izvanrednog pogonskog stanja, odnosno kvara u postrojenju. Sustav istosmjernog razvoda sastoji se od baterije, ispravljača i instalacija sa pripadnim trošilima. Neki od vitalnih dijelova elektroenergetskih postrojenja kao što su prekidači, zaštita i upravljački uređaji moraju imati besprekidno i pouzdano napajanje jer moraju biti u mogućnosti raditi u svim pogonskim stanjima. Sukladno tome sustav istosmjernog razvoda treba biti najpouzdaniji dio postrojenja. Usprkos svemu u posljednjih trideset godina dogodio se znatan broj kvarova u postrojenjima zbog kvara u sustavu istosmjernog razvoda. U većini slučajeva pogrešno djelovanje bila je posljedica neselektivnosti zaštitnih uređaja. Selektivnost zaštitnih uređaja prepoznata je kao glavni problem prilikom projektiranja sustava istosmjernog razvoda. Dosadašnja praksa proračuna struja kratkog spoja zasnivala se samo na stacionarnom stanju nakon nastanka kratkog spoja, odnosno pojednostavljenom modelu koji je uzimao u obzir samo otpor dijelova sustava istosmjernog razvoda, što ne odgovara stvarnom stanju. U ovom radu predlaže se novi pristup koji ne uzima u obzir samo otpor već i induktivitete i kapacitete dijelova sustava istosmjernog razvoda i također izmjeničnu aktivnu mrežu ispred ispravljača. Razvijeni je i programski paket osnovan na novom pristupu koji uključuje kako provjeru svih glavnih dijelova postojećeg sustava istosmjernog razvoda, već daje i mogućnost projektiranja novog sustava istosmjernog razvoda. Time je omogućeno interaktivno projektiranje sustava istosmjernog razvoda u elektroenergetskom postrojenjima.Auxiliary DC installations in power plants and substations are extremely important because they enable reliable operation in normal operating mode as well as in the case of operating mode failure. Auxiliary DC installation system consists of a battery, a rectifier and installations with corresponding consumers. Some vital parts of electrical plants such as circuit breakers, protection and control devices should have uninterruptible and reliable power supply because they should function in all operating modes. Accordingly, auxiliary DC installations are expected to be the most secure and the most reliable parts of electrical plants. Nevertheless, there have been numerous failures in electrical plants in the past thirty years due to malfunction of auxiliary DC installation operation. In most cases, malfunction was caused by bad selectivity of protection devices. In the past few years protection device selectivity in auxiliary DC installations has been recognized as major problem in planning and designing DC installations. Up to now the practice of short circuit calculation has been based on stationary state only after the short circuit occurred. This thesis propose new approach that considers not only resistances, but also inductances and capacities of auxiliary DC elements as well as the active network in front of the rectifier. As part of this thesis it was developed program package that does not include the testing of main parts of auxiliary DC installations only, but it also gives the possibility of testing any part of the installations in order to reach a satisfactory solution. This makes interactive planning of new plants and substations possible

Primjena neuronskih mreža u postupku podešenja distantne zaštite visokonaponskih prijenosnih vodova

U ovom radu je rješavana problematika distantne zaštite visokonaponskih prijenosnih vodova korištenjem neuronskih mreža. Tijekom rada razvijeni su algoritmi za zaštitu koji rješavaju osnovne probleme zaštite i to napajanje kvara s obje strane voda preko otpora na mjestu kvara i zaštita dvostrukih vodova obzirom na međuinduktivitet između pojedinih vodova. U uvodnom dijelu rada prikazane su teorijske osnove distantne zaštite visokonaponskih prijenosnih vodova, osnovni principi i definicija adaptivne zaštite i osnove korištenih neuronskih mreža. Razvijeni adaptivni modeli su osnovani na neuronskim mrežama i to dva tipa: višeslojni perceptron i Kohonenova samoorganizirajuća mreža. Za svaki od modela razrađen je kompletan model izvedbe, učenja i primjene. Korištenje modela zasnovanog na Kohonenovoj mreži predstavlja novost u odnosu na višeslojni perceptron koji je do sada uglavnom bio korišten. Uvođenjem Kohonenove mreže iskorišteno je svojstvo da se svi raznmatrani problemi svode na rješavanje binarnog problema. Svaki od adaptivnih distantnih modela zaštite koristio je za simulaciju programski paket, razvijen prilikom izrade ovog rada, koji omogućava kreiranje, učenje i provjeru neuronskih mreža - višeslojnog perceptrona i Kohonenove mreže. Programski paket je uspoređen i s nekim drugim programima koji se koriste u svijetu, te je pokazao zadovoljavajuće rezultate. Razvijeni modeli zaštite teoretski su provjereni na dijelu prijenosnog sustava Hrvatske elektroprivrede: na 110 kV-nom vod Plomin - Lovran i 400 kV-nom vod Žerjavinec - Héviz. Analizom rezultata provjere teorijski je potvrđena primjenljivost razvijenih modela, te se pokazala prednost pri korištenju modela zasnovanih na Kohonenovim mrežama.This thesis deals with problems related to distance protection of transmission lines using artificial neural networks. In the thesis algorithms for protection were developed for solving basic problems: two terminal transmission lines with fault resistance and double - circuit lines with mutual coupling impedance. The introduction presents the theoretical principles of distance protection of transmission lines, basic principles and definitions of adaptive protection with basics of the neural networks used later. Developed adaptive models are based on two neural networks: multi - layered perceptron and Kohonen self - organizing map. For each model full installation scheme, program of learning and testing was created. Model based on Kohonen map is original contribution in the thesis. Kohonen map was introduced in order to transform the mentioned problems to the binary ones. Each adaptive protection model used the program package developed during the work on the thesis. The program package permits creation, learning and testing of neural networks - multi - layered perceptron and Kohonen map. It was compared with other program packages used worldwide. Developed models were theoretically tested on part of the transmission system of the Croatian electricity - 110 kV transmission line Plomin - Lovran and 400 kV transmission line Žerjavinec - Héviz. The results showed that the models are applicable. Also it was shown that the models based on Kohonen map gave better results

Primjena neuronskih mreža u postupku podešenja distantne zaštite visokonaponskih prijenosnih vodova

U ovom radu je rješavana problematika distantne zaštite visokonaponskih prijenosnih vodova korištenjem neuronskih mreža. Tijekom rada razvijeni su algoritmi za zaštitu koji rješavaju osnovne probleme zaštite i to napajanje kvara s obje strane voda preko otpora na mjestu kvara i zaštita dvostrukih vodova obzirom na međuinduktivitet između pojedinih vodova. U uvodnom dijelu rada prikazane su teorijske osnove distantne zaštite visokonaponskih prijenosnih vodova, osnovni principi i definicija adaptivne zaštite i osnove korištenih neuronskih mreža. Razvijeni adaptivni modeli su osnovani na neuronskim mrežama i to dva tipa: višeslojni perceptron i Kohonenova samoorganizirajuća mreža. Za svaki od modela razrađen je kompletan model izvedbe, učenja i primjene. Korištenje modela zasnovanog na Kohonenovoj mreži predstavlja novost u odnosu na višeslojni perceptron koji je do sada uglavnom bio korišten. Uvođenjem Kohonenove mreže iskorišteno je svojstvo da se svi raznmatrani problemi svode na rješavanje binarnog problema. Svaki od adaptivnih distantnih modela zaštite koristio je za simulaciju programski paket, razvijen prilikom izrade ovog rada, koji omogućava kreiranje, učenje i provjeru neuronskih mreža - višeslojnog perceptrona i Kohonenove mreže. Programski paket je uspoređen i s nekim drugim programima koji se koriste u svijetu, te je pokazao zadovoljavajuće rezultate. Razvijeni modeli zaštite teoretski su provjereni na dijelu prijenosnog sustava Hrvatske elektroprivrede: na 110 kV-nom vod Plomin - Lovran i 400 kV-nom vod Žerjavinec - Héviz. Analizom rezultata provjere teorijski je potvrđena primjenljivost razvijenih modela, te se pokazala prednost pri korištenju modela zasnovanih na Kohonenovim mrežama.This thesis deals with problems related to distance protection of transmission lines using artificial neural networks. In the thesis algorithms for protection were developed for solving basic problems: two terminal transmission lines with fault resistance and double - circuit lines with mutual coupling impedance. The introduction presents the theoretical principles of distance protection of transmission lines, basic principles and definitions of adaptive protection with basics of the neural networks used later. Developed adaptive models are based on two neural networks: multi - layered perceptron and Kohonen self - organizing map. For each model full installation scheme, program of learning and testing was created. Model based on Kohonen map is original contribution in the thesis. Kohonen map was introduced in order to transform the mentioned problems to the binary ones. Each adaptive protection model used the program package developed during the work on the thesis. The program package permits creation, learning and testing of neural networks - multi - layered perceptron and Kohonen map. It was compared with other program packages used worldwide. Developed models were theoretically tested on part of the transmission system of the Croatian electricity - 110 kV transmission line Plomin - Lovran and 400 kV transmission line Žerjavinec - Héviz. The results showed that the models are applicable. Also it was shown that the models based on Kohonen map gave better results

Selectivity of protection devices in auxiliary DC installations

Sustav istosmjernog razvoda u elektroenergetskim postrojenjima je od velike važnosti jer omogućava pouzdano vođenje elektrane i transformatorske stanice kako u normalnom pogonu, te također u slučaju izvanrednog pogonskog stanja, odnosno kvara u postrojenju. Sustav istosmjernog razvoda sastoji se od baterije, ispravljača i instalacija sa pripadnim trošilima. Neki od vitalnih dijelova elektroenergetskih postrojenja kao što su prekidači, zaštita i upravljački uređaji moraju imati besprekidno i pouzdano napajanje jer moraju biti u mogućnosti raditi u svim pogonskim stanjima. Sukladno tome sustav istosmjernog razvoda treba biti najpouzdaniji dio postrojenja. Usprkos svemu u posljednjih trideset godina dogodio se znatan broj kvarova u postrojenjima zbog kvara u sustavu istosmjernog razvoda. U većini slučajeva pogrešno djelovanje bila je posljedica neselektivnosti zaštitnih uređaja. Selektivnost zaštitnih uređaja prepoznata je kao glavni problem prilikom projektiranja sustava istosmjernog razvoda. Dosadašnja praksa proračuna struja kratkog spoja zasnivala se samo na stacionarnom stanju nakon nastanka kratkog spoja, odnosno pojednostavljenom modelu koji je uzimao u obzir samo otpor dijelova sustava istosmjernog razvoda, što ne odgovara stvarnom stanju. U ovom radu predlaže se novi pristup koji ne uzima u obzir samo otpor već i induktivitete i kapacitete dijelova sustava istosmjernog razvoda i također izmjeničnu aktivnu mrežu ispred ispravljača. Razvijeni je i programski paket osnovan na novom pristupu koji uključuje kako provjeru svih glavnih dijelova postojećeg sustava istosmjernog razvoda, već daje i mogućnost projektiranja novog sustava istosmjernog razvoda. Time je omogućeno interaktivno projektiranje sustava istosmjernog razvoda u elektroenergetskom postrojenjima.Auxiliary DC installations in power plants and substations are extremely important because they enable reliable operation in normal operating mode as well as in the case of operating mode failure. Auxiliary DC installation system consists of a battery, a rectifier and installations with corresponding consumers. Some vital parts of electrical plants such as circuit breakers, protection and control devices should have uninterruptible and reliable power supply because they should function in all operating modes. Accordingly, auxiliary DC installations are expected to be the most secure and the most reliable parts of electrical plants. Nevertheless, there have been numerous failures in electrical plants in the past thirty years due to malfunction of auxiliary DC installation operation. In most cases, malfunction was caused by bad selectivity of protection devices. In the past few years protection device selectivity in auxiliary DC installations has been recognized as major problem in planning and designing DC installations. Up to now the practice of short circuit calculation has been based on stationary state only after the short circuit occurred. This thesis propose new approach that considers not only resistances, but also inductances and capacities of auxiliary DC elements as well as the active network in front of the rectifier. As part of this thesis it was developed program package that does not include the testing of main parts of auxiliary DC installations only, but it also gives the possibility of testing any part of the installations in order to reach a satisfactory solution. This makes interactive planning of new plants and substations possible

Primjena neuronskih mreža u postupku podešenja distantne zaštite visokonaponskih prijenosnih vodova

U ovom radu je rješavana problematika distantne zaštite visokonaponskih prijenosnih vodova korištenjem neuronskih mreža. Tijekom rada razvijeni su algoritmi za zaštitu koji rješavaju osnovne probleme zaštite i to napajanje kvara s obje strane voda preko otpora na mjestu kvara i zaštita dvostrukih vodova obzirom na međuinduktivitet između pojedinih vodova. U uvodnom dijelu rada prikazane su teorijske osnove distantne zaštite visokonaponskih prijenosnih vodova, osnovni principi i definicija adaptivne zaštite i osnove korištenih neuronskih mreža. Razvijeni adaptivni modeli su osnovani na neuronskim mrežama i to dva tipa: višeslojni perceptron i Kohonenova samoorganizirajuća mreža. Za svaki od modela razrađen je kompletan model izvedbe, učenja i primjene. Korištenje modela zasnovanog na Kohonenovoj mreži predstavlja novost u odnosu na višeslojni perceptron koji je do sada uglavnom bio korišten. Uvođenjem Kohonenove mreže iskorišteno je svojstvo da se svi raznmatrani problemi svode na rješavanje binarnog problema. Svaki od adaptivnih distantnih modela zaštite koristio je za simulaciju programski paket, razvijen prilikom izrade ovog rada, koji omogućava kreiranje, učenje i provjeru neuronskih mreža - višeslojnog perceptrona i Kohonenove mreže. Programski paket je uspoređen i s nekim drugim programima koji se koriste u svijetu, te je pokazao zadovoljavajuće rezultate. Razvijeni modeli zaštite teoretski su provjereni na dijelu prijenosnog sustava Hrvatske elektroprivrede: na 110 kV-nom vod Plomin - Lovran i 400 kV-nom vod Žerjavinec - Héviz. Analizom rezultata provjere teorijski je potvrđena primjenljivost razvijenih modela, te se pokazala prednost pri korištenju modela zasnovanih na Kohonenovim mrežama.This thesis deals with problems related to distance protection of transmission lines using artificial neural networks. In the thesis algorithms for protection were developed for solving basic problems: two terminal transmission lines with fault resistance and double - circuit lines with mutual coupling impedance. The introduction presents the theoretical principles of distance protection of transmission lines, basic principles and definitions of adaptive protection with basics of the neural networks used later. Developed adaptive models are based on two neural networks: multi - layered perceptron and Kohonen self - organizing map. For each model full installation scheme, program of learning and testing was created. Model based on Kohonen map is original contribution in the thesis. Kohonen map was introduced in order to transform the mentioned problems to the binary ones. Each adaptive protection model used the program package developed during the work on the thesis. The program package permits creation, learning and testing of neural networks - multi - layered perceptron and Kohonen map. It was compared with other program packages used worldwide. Developed models were theoretically tested on part of the transmission system of the Croatian electricity - 110 kV transmission line Plomin - Lovran and 400 kV transmission line Žerjavinec - Héviz. The results showed that the models are applicable. Also it was shown that the models based on Kohonen map gave better results