A Review of Fault Diagnosing Methods in Power Transmission Systems

Transient stability is important in power systems. Disturbances like faults need to be segregated to restore transient stability. A comprehensive review of fault diagnosing methods in the power transmission system is presented in this paper. Typically, voltage and current samples are deployed for analysis. Three tasks/topics; fault detection, classification, and location are presented separately to convey a more logical and comprehensive understanding of the concepts. Feature extractions, transformations with dimensionality reduction methods are discussed. Fault classification and location techniques largely use artificial intelligence (AI) and signal processing methods. After the discussion of overall methods and concepts, advancements and future aspects are discussed. Generalized strengths and weaknesses of different AI and machine learning-based algorithms are assessed. A comparison of different fault detection, classification, and location methods is also presented considering features, inputs, complexity, system used and results. This paper may serve as a guideline for the researchers to understand different methods and techniques in this field

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

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

Fault Location in Transmission Systems Using Synchronized Measurements

Compared with conventional measurements from supervisory control and data acquisition (SCADA) system, phasor measurement units (PMUs) provide time-synchronized and direct measurements of phasors. The availability of synchronized phasor measurements can significantly improve power system protection and analysis. This dissertation is specifically committed to using synchronized measurements for estimation of fault locations in transmission systems. Transmission lines are prone to various short-circuit faults. Accurate fault location is critical for rapid power recovery. Chapter 2 proposes a new fault location method based on sparse wide area measurements. One distinguishing feature of this method is its applicability to both transposed and untransposed transmission lines. In addition, the method is developed based on sparse-wide area measurement that may be taken far away from the faulted line. Shunt capacitances of transmission lines are also fully considered by the algorithm. Moreover, when synchronized measurements from multiple buses are available, an optimal estimator can be used to make the most use of measurements, and to detect and identify potential bad measurements. Most of the existing fault location literatures discuss common shunt faults, including single line-to-ground faults, line-to-line faults, line-to-line-to-ground faults, and three-phase faults. However, in addition to common shunt faults, some complex faults may also occur in power systems. Among these complex faults, evolving fault and inter-circuit fault are two typical examples. Chapter 3 extends the method developed in Chapter 2 to deal with evolving faults. The proposed wide-area fault location methods are immune to fault type evolution, and are applicable to both transposed and untransposed lines. Chapter 4 discusses location of inter-circuit faults. Inter-circuit fault is a type of simultaneous fault, and it is the most common simultaneous fault type. Inter-circuit faults between each circuit in a double-circuit line is the most common inter-circuit fault. A fault location method for inter-circuit faults on double-circuit lines are developed and evaluated in Chapter 4. Chapter 5 puts forward a fault location algorithm, which does not require line parameters information, for series-compensated transmission lines. Two-end synchronized voltage and current measurements are utilized. The proposed method is independent of source impedance and fully considers shunt capacitances of transmission lines

Intermittent earth fault passage indication in compensated distribution networks

An intermittent or restriking earth fault is a special type of earth fault that is common mostly in compensated cable networks. A great deal of effort has gone into protection against this type of fault. However, locating this fault has not received much attention. Therefore, there is a need to have a reliable method for locating this fault to repair the damaged cable. In this paper, the principles of a new method developed for locating transient intermittent earth faults on distribution networks are presented. The proposed method employs negative and zero sequence currents, and no voltage measurement is required, which means the proposed method has the potential to reduce cost when implemented in practice. It is intended mainly for typical intermittent earth faults in cable distribution networks where the typical fault resistance is in the range of a few ohms. Real data obtained from practical field tests is used to explain the phenomenon. A series of disturbance recordings obtained from field tests validate the proposed method.©2021 Elsevier. This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/ This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication.fi=vertaisarvioitu|en=peerReviewed

Non-Directional Earth Fault Passage Indication in Isolated Neutral Distribution Networks

In this paper, two new methods for locating single-phase to ground faults in isolated neutral distribution networks are proposed. The methods are based on the analysis of symmetrical sequence currents. They are solely based on currents, not requiring voltage measurement. The first method employs only the zero sequence current and the second one utilizes the negative sequence current in combination with the zero sequence current. It is revealed why using only zero sequence current with a simple threshold is insufficient and may lead to false results. Using the proposed methods, earth faults with high resistances can be located in isolated neutral distribution networks with overhead lines or cables.© Writers. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license, http://creativecommons.org/licenses/by/4.0/fi=vertaisarvioitu|en=peerReviewed

Development Needs in Automatic Fault Location, Isolation and Supply Restoration of MicroSCADA Pro DMS600

Tightened reliability requirements for the electricity distribution are causing distribution system operators to improve the quality of supply by renovating the network. To achieve a weather-proof distribution network by the end of year 2028, major investments must be made by means of replacing overhead lines with cables and increasing the level of automation in the network. Since the renovation process is rather slow and expensive, DSOs must obtain cost savings in distribution network operation by utilizing existing network automation more efficiently. One of the main solutions is to automatize the fault management and thereby reduce outage duration experienced by the customer. Traditional fault management comprises the co-operation of the network control center and field crews working along the distribution network. An increasing amount of network automation, such as remote-controlled disconnectors, sectionalizing reclosers and fault detectors, is improving the response time of medium network faults when the operator can isolate the fault remotely from the control center. However, multiple simultaneous faults in major electricity disruption can cause personnel of the control center to be overburdened with fault handling and dispatching field crews. Therefore, automatic Fault Location, Isolation, and supply Restoration (FLIR) functionality is considered as a beneficial tool to assist the network operator. While the FLIR performs the first steps of fault management, operator is freed to conduct the operation of field crews repairing failures. MicroSCADA Pro is a product family for electricity distribution control and supervisory by ABB. The current version of MicroSCADA Pro DMS600 4.5 already includes functionality for automatic fault isolation and supply restoration, but it is not used by any DSOs due to functional imperfections. The current fault detection, isolation and supply restoration (FDIR) functionality requires an exact fault location inferred by fault current measurements or fault indicator operations and therefore, it can rarely operate due to lack of initial data. To achieve an efficient operation, a trial switching sequence must be introduced as part of the existing functionality. The method of trial switching is normally used by the operator when fault cannot be located according to measurements and indications. A basic principle of the trial switchings is to divide faulty feeder into minor sections and close the substation circuit breaker against the suspected fault. This is continued until the circuit breaker trips and the fault has been located and isolated into a single disconnector zone. The research for this thesis was carried out by interviews for Finnish DSOs to gather requirements and restrictions for the FLIR functionality. The main objective of the interview process was to familiarize the fault management process of a network control center operator, so as human-like operation of the FLIR could be obtained. Interviews gathered the most important development needs and possible restrictions to ensure the most fluent operation between automation and the network control center operators. For example, automation may not be wanted to restore supply from adjacent feeders during major disturbance, since multiple fault can occur and cause also backup feeder to trip and increase the faulty area. Automatic functionality should not also disturb the operation of network control center, and thus separate fault handling areas should be determined for FLIR to operate

Diagnostic Applications for Micro-Synchrophasor Measurements

This report articulates and justifies the preliminary selection of diagnostic applications for data from micro-synchrophasors (µPMUs) in electric power distribution systems that will be further studied and developed within the scope of the three-year ARPA-e award titled Micro-synchrophasors for Distribution Systems