348 research outputs found

    Accurate location of high impedance and temporary faults in radial distribution networks using distributed travelling wave observers

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    This thesis addresses a novel method for fault location in radial distribution networks and provides a new vision for the optimal deployment of synchronised voltage travelling wave (TW) observers in distribution networks. The proposed method can locate high impedance and temporary faults. The delay effect of transformers is demonstrated by theory and laboratory tests. A new method to eliminate the transformer’s effect on the accuracy of the fault location algorithm is presented

    High voltage covered conductor overhead lines: detection of incipient tree faults

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    The aim of this thesis is the study of a new type of high voltage overhead power line, made by means of an insulation layer located around the conductor: these are the covered conductor lines. In particular, the work focuses on the study of the behaviour of these conductors when they get in contact with the vegetation around, which can touch or fall on the line.ope

    Novel methods for earth fault passage indication in non-effectively grounded electricity distribution networks

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    Electricity distribution networks are commonly subject to supply interruptions and outages caused by faults. This dissertation focuses on medium voltage distribution networks, which typically consist of primary substations having multiple feeders along which secondary substations are located. When a permanent fault occurs on a segment (the part linking two consecutive secondary substations) of a distribution feeder, the faulted segment needs to be identified and isolated. Identifying the faulted segment can be realized through fault passage indicators. This is a straightforward task when the fault type is a short circuit, as these types of faults involve large currents. However, faulted segment identification for earth faults in non-effectively grounded medium voltage distribution networks has remained a challenge as the earth fault current in those networks is typically relatively small. Therefore, the main objective of this dissertation was to develop novel methods for locating single-phase earth faults in medium voltage distribution networks and validating them through simulations and real system measurements. After comprehensive review of state-of-the-art approaches presented in the literature, the dissertation proposes innovative methods for earth fault passage indication aimed at non-effectively grounded urban or rural distribution networks with radial feeders. The proposed methods are underpinned by a theoretical analysis based on the symmetrical components of the currents on a distribution feeder under an earth fault condition. The comparison of the sequence currents collected from various measuring points on the network forms the backbone of the methods. For practical implementation, current measurements need to be transferred to a central location for processing and decision making, but this can be done without accurate time synchronization. The proposed methods were developed and verified through simulations and empirical data. This work is a product of close collaboration between academia and industry that enabled the validation of the proposed methods with the help of empirical data that was provided by system operators and relay manufacturers. The results obtained from simulations and field tests show the efficacy of utilizing sequence current quantities, in the manner proposed in this work, for identifying the passage of earth faults with fault resistances ranging from zero to several kilo-ohms. In practice, the methods are reliable as long as the current measurements are accurate enough.Sähkönjakeluverkoissa esiintyy vikoja, jotka aiheuttavat sähkönjakelun keskeytyksiä eli sähkökatkoja. Tämä väitöskirja käsittelee keskijänniteverkkoja, jotka koostuvat sähköasemista ja niiltä lähtevistä johtolähdöistä. Johtolähtöjen varrella sijaitsevat pienjänniteverkkoa syöttävät muuntamot. Kun jollain johto-osuudella (tässä ns. muuntamovälillä, joka yhdistää kaksi peräkkäistä muuntamoa) ilmenee pysyvä vika, viallinen johto-osuus on tunnistettava ja erotettava. Viallisen johto-osuuden tunnistaminen tapahtuu vianilmaisimien avulla. Viallisen johto-osuuden tunnistaminen on yksinkertaista, kun vikatyyppi on oikosulku, sillä oikosuluille ominaista ovat yleensä suuret vikavirrat. Haasteena on kuitenkin edelleen viallisten johto-osuuksien tunnistaminen maasulkutilanteissa ei-tehollisesti maadoitetuissa keskijänniteverkoissa, joissa maasulkuvirta on tyypillisesti hyvin pieni. Tämän väitöskirjana tavoitteena on ollut kehittää uusia menetelmiä maasulkuvikojen paikantamiseen keskijänniteverkossa ja varmentaa niiden toimivuus simuloinnein ja todellisesta verkosta saatujen mittausten avulla. Kattavan kirjallisuuskatsauksen jälkeen tässä väitöskirjassa esitellään innovatiivisia menetelmiä vikavirran reitin ilmaisuun jakeluverkkojen maasuluissa. Ehdotetut menetelmät tukeutuvat teoreettiseen analyysiin, jossa johtolähdön virrat maasulkutilanteessa on kuvattu symmetristen komponenttien avulla. Menetelmät perustuvat verkon eri pisteissä mitattuihin virran symmetristen komponenttien vertailuun. Käytännön toteutuksessa nämä mittaukset tulee siirtää keskitettyyn järjestelmään prosessointia ja päätöksentekoa varten, mutta tämä voidaan tehdä ilman tarkkaa aikasynkronointia. Ehdotettujen menetelmien kehittämisessä ja testaamisessa hyödynnettiin simulointeja ja kokeellista mittausdataa. Yhteistyö teollisuuden kanssa mahdollisti menetelmien toiminnan todentamisen hyödyntäen todellisista verkoista mitattua dataa, jota saatiin sekä verkkoyhtiöiltä että laitevalmistajilta. Simulointien tulokset ja mittaukset todellisessa verkossa tehdyistä testeistä osoittavat, että virran symmetriset komponentit toimivat hyvin vian paikannuksessa kun vikaresistanssi on nollan ja muutaman tuhannen ohmin välillä. Käytännössä menetelmien luotettavuus riippuu virran mittauksen tarkkuudesta.fi=vertaisarvioitu|en=peerReviewed

    Time domain analysis of switching transient fields in high voltage substations

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    Switching operations of circuit breakers and disconnect switches generate transient currents propagating along the substation busbars. At the moment of switching, the busbars temporarily acts as antennae radiating transient electromagnetic fields within the substations. The radiated fields may interfere and disrupt normal operations of electronic equipment used within the substation for measurement, control and communication purposes. Hence there is the need to fully characterise the substation electromagnetic environment as early as the design stage of substation planning and operation to ensure safe operations of the electronic equipment. This paper deals with the computation of transient electromagnetic fields due to switching within a high voltage air-insulated substation (AIS) using the finite difference time domain (FDTD) metho

    Fault Location Based on Synchronized Measurements: A Comprehensive Survey

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    Automatic fault location in electrical distribution networks with distributed generation

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    Nowadays the electrical network is continuously evolving due to the increasing deployment of Information Technologies and the Distribution Energy Resources. This scenario affects directly to the quality of service in the electrical distribution networks. For this reason, the Power Quality is a key important concern to make the electrical network evolve towards a Smart Grid. Power quality is defined through three important focal points: availability, wave quality and commercial quality. The presence of the Distribution Energy Resources in the current electrical distribution network is showing a new scenario where the fault detection is more complex due to the flow current is in both directions. This thesis is focused in the analysis of several methods to locate a fault in electrical distribution network and also how the current communication standards can improve considerably this fault location. It is important to remark that the main contribution of this thesis is in the analysis of several propositions and algorithms to enhance the fault location in a distribution network using the current Intelligent Electronic Device with international standards such as IEC 61850. All of these algorithms have been focused to work in a mesh distribution networks. Another important contribution of this thesis is in the adaptive protection system in order to isolate correctly the fault in a ring system distribution. Although this proposition could be extended to a mesh network where the elements of the network can operate under a fault. Finally, the thesis concludes that the use of communication standards and Internet of Things with current developed Intelligent Electronic Devices technology can contribute significantly to enhance the current and future electrical network distribution.La xarxa elèctrica evoluciona contínuament a causa del creixent desplegament de les Tecnologies de la Informació i dels Recursos Energètics Distribuïts. Aquest escenari afecta directament a la qualitat de servei de les xarxes de distribució elèctrica. Per aquest motiu, el mantenir i millorar el nivell de qualitat d'energia és un punt clau per fer evolucionar la xarxa elèctrica cap a una xarxa Smart Grid. Aquesta qualitat de l'energia es defineix per medi de de tres punts importants: disponibilitat, qualitat d'ona i qualitat comercial. La presència dels Recursos Energètics Distribuïts mostra un nou escenari en què la detecció de defectes es complica afectant a la disponibilitat del servei. Aquesta tesi es centra principalment en l'anàlisi de diversos mètodes per localitzar un defecte a la xarxa de distribució elèctrica i també en com l'ús dels estàndards de comunicació actuals poden contribuir considerablement a la localització del defecte. És important remarcar que la principal contribució d'aquest document ha estat en l'anàlisi de diverses proposicions i algoritmes per millorar la localització de faltes en una xarxa de distribució utilitzant Dispositius Electrònics Intel·ligents amb estàndards internacionals com l'IEC 61850. Tots aquests algoritmes han estat definits per treballar en xarxes de distribució mallades. Una altra contribució important d'aquesta tesi es troba en el sistema de protecció adaptatiu per tal d'aïllar correctament el defecte en una distribució del sistema d'anell amb interruptors automàtics. Aquesta proposta es podria ampliar a una xarxa mallada. Finalment, la tesi conclou amb que l'ús d'estàndards de comunicació i l'Internet of Things en combinació amb Dispositius Electrònics Intel·ligents, desenvolupats actualment, poden contribuir significativament a millorar la distribució de la xarxa elèctrica actual i futura.Postprint (published version

    Impedance based fault location in power distribution systems

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    This thesis presents an investigation into impedance based fault location methods which directly use the fault transient as an excitation source to provide fast and accurate fault locations in small distribution systems such as the modem marine and aircraft power systems which have Integrated Power System (IPS) configuration. Fast and accurate fault location on un-exposed power distribution lines is of vital importance to expedite service restoration and improving the reliability of the power system. Two fault location algorithms are developed: the single-ended method and the double-ended method. The singled-ended algorithm which captures current and voltage waveforms from one end of the distribution cable estimates the fault locations using an iteration calculation. The double-ended method has a simple algorithm and is robust to different fault situations but requires additional data measured from the remote end of the cable. Both simulation and experimental tests have been done and the results are good enough to validate that the developed methods can locate fault positions using a 12ms window and otter an accuracy of within 1m in the proposed distribution system. The advantages and disadvantages of the proposed fault location methods are investigated under different fault situations. The possibility of employing the two methods in protection of faults in a marine power system is demonstrated. Due to the special characteristics of the marine power system, an active method which simply involves adding an IGBT switch is proposed for the earth fault protection
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