Academic literature on the topic 'Directional earth-fault protection'

In distribution 6–10 kV networks with an insulated neutral for earth fault protection, zero sequence current directional protection devices are commonly used. According to the operation data, the main disadvantage of such kind of protection is the possibility of their functioning failures in transient conditions with the most dangerous for network intermittent arc earth faults. It is known that most earth faults in 6–10 kV networks, primarily in the initial stage of insulation damage, have an intermittent arc. Operation failures of zero sequence current directional protection in case of arc faults reduce the operational reliability of the protected network and, as a result, the reliability of power supply to consumers. Nowadays, new developments of electrical power systems relay protection devices, including earth fault protection of medium voltage distribution electrical networks, are implemented only on a microprocessor base. Therefore, the selection and justification of the implementation principles of zero sequence current directional protection which can provide high dynamic stability of functioning is a relevant objective. When analyzing the dynamic stability of the functioning of zero sequence directional current protection, regarding the complexity of transients during intermittent arc earth faults in medium voltage electrical networks with an isolated neutral, the simulation in Matlab using SimPowerSystem and Simulink was carried out. This study focuses on transient currents and voltages as the main factor influencing dynamic stability of the functioning of zero sequence current directional protection. The impact of other factors, for example, the inaccuracies of the primary zero sequence current and voltage transducers, the scheme of formation of compared quantities, etc. was not taken into account in simulation models. The study has allowed determining the causes of possible functioning failures of digital current earth fault directional protection in dynamic operation modes. It has been shown that the usage of orthogonal components of fundamental frequency of zero sequence voltage and current in current directional protection devices eliminates the failure of their operation with any kind of arc earth faults. To ensure high dynamic stability of operation under the influence of transients during arc intermittent earth faults, current directional protection for this type of damage should be performed on the basis of monitoring the phase relationships of the fundamental frequency components of 50 Hz of zero sequence voltage and current, but not their full values.

Overcurrent and earth fault protective equipment employing time grading and directional detection cannot provide correct discrimination on all power networks and in many cases clearing times for some faults would not be acceptable. Differential protection is an alternative overcurrent protective scheme, which is used to protect individual sections of networks or pieces of equipment, such as transformers, generators, e.t.c. Thus, where protection co-ordination is difficult using time delayed over current and earth fault protection, or where fast fault clearance is critical, then differential protection may be used. Kirchhoff’s first law, which states that the sum of the currents flowing to a node must be equal to the sum of the currents flowing out from it is the basic principle of the differential protection scheme. It detects the difference between the current entering a section and that leaving it. Under normal operating conditions, the current leaving the protected unit would be equal to that entering it at every instant. If the current flowing into the protected unit is the same as the current leaving, then the fault is not in the protected unit and the protective equipment or relay should not operate. If there is a difference in either the phase or magnitude between input and output, then the fault is in the protected unit and the protection should operate. This paper investigates how power transformers can be protected using the current-differential protection schemes.

This work aims to study relay protection and automation in insulated neutral networks to identify additional criteria for choosing the type of earthing. To calculate the single-phase earth fault currents as a function of the operating modes of the electrical substation, the 10 kV network of the electrical substation was simulated in the software package. The advantages and disadvantages of centralized and non-centralized protections are shown. The paper presents the sequence of actions necessary for the correct operation of directional zero sequence protection.

A novel algorithm is proposed for the purpose of improving the reliability and sensibility of fault component identification of wide area backup protection. The algorithm, called earth impedance comparison protection (EICP), is realized by comparing the ratios of different nodes, and the ratio is obtained by the bus voltage to the differential current. The advantages of EICP are verified in this paper using the measurement function of wide-area measurement system. The results of case studies show that EICP is superior to the current differential protection in terms of the sensitivity and to the directional pilot protection in terms of the dependability. The satisfactory results can be obtained when the EICP method is applied in the event of abnormal operations of protective relays and circuit breakers, measurement error scenarios or substation DC failure.

The paper demonstrates improving the reliability of power supply and operating safety of power receivers in electric networks of 6-10 kV, by controlling the neutral mode in extended electric networks of 6-10 kV with capacitive earth fault currents above 15 A. The purpose of the study is to increase the reliability of power supply and the safety of operation of power receivers in such electric networks, the establishment of patterns in controlling the neutral mode in extended 6-10 kV electric networks with capacitive earth fault currents above 15 A, as well as the development of a method and device automatic detection of single-phase earth fault current. Grounding methods and neutral modes in electric networks with a voltage of 6-10 kV are considered. The method and device for automatically determining the current of a single-phase earth fault were developed. In the result, the relationship between the active and inductive components of the neutral current during series RL grounding of the network Ia/IL=(0.5÷0.3) was established, which ensures reliable operation of the SPEF protection of both current and directional principles including the changes of capacity abruptly networks caused by switching outgoing lines.

The substation is one of the components in the electric power distribution system which plays a very important role because it is the connection between electricity services to customers. In the electric power distribution system, there are disturbances that often occur, one of which is a short circuit. For that, the way to overcome this is using the Distance Relay protection system, OCR / GFR and DEF. The purpose of writing this research is to determine the value of setting relay distance, setting Over Current Rele and Directional Earth Fault relay in order to secure the 70 kV transmission network connected to GI Banaran, which is then simulated using DigSILENT 15.1 software on the Pare line by calculating symmetrical and asymmetrical disturbances. including 3-phase disturbance on February 1, 2018. The simulation results show that the 3-phase disturbance occurs at Zone 1 relay distance of the Banaran Bay Pare substation with a trip time of 0.02 seconds with a fault impedance of 0.083 ohms below the relay impedance value of 0.887 ohms. The coordination between the distance relay on the side of the Banaran Bay Pare substation has worked well because there is no error reading the relay when it will cut off the disturbance.

Manufactures of power system products face an increased pressure to reduce the time tomarket of their development process without compromising quality. Moreover the operationof power systems needs to be performed in a secure and reliable manner. One ofthe key systems to guarantee those stringent requirements is the protection system. Theobjective of this Master’s thesis is the development of a protection system, which solidlyrelies on Commerciall-o↵-the-Shelf (COTS) components as well as on the developed protectionfunctions. Thereby it is shown that the tight cost requirements can be fulfilledwithout jeopardising the reliability and security performance.This project comprises the development of a definite-time directional overcurrent andearth fault protection. The applied development process is based on a model-based-designapproach, which comprises the definition of the requirements, the design phase, the implementationon the target system and the test phase. As part of this thesis each stageis described and executed. Moreover MATLAB/Simulink was used as development environment,since it perfectly supports the model-based-design approach. The consideredfunctional requirements are mostly based on the standard IEC 60255-151. The developedprotection algorithm runs on a realtime linux system and the interface to the process isbased on the EtherCAT protocol and their corresponding I/O modules. Lastly, the testphase is based on a functional performance test, a type test according to IEC 60255-151,a longterm test and an evaluation of the EMC performance of the used I/O modules.The results of the type tests showed that a IEC 60255-151 compliant solution is yield.Moreover the functional performance test proofed that the developed protection functionoperate as intended for various fault scenarios. Lastly, the realtime performance of protectionsystem has to be further analysed and adapted in order to achieve satisfactorybehaviour.i
Tillverkare av elkraftskomponenter st°ar inf¨or ¨okade utmaningar f¨or att minska tiden f¨orproduktutveckling utan att kompromissa med kvalit´en.Utmaningen blir st¨orre n¨ar ett s¨akert och tillf¨orlitligt elkraftsystem m°aste uppfyllas. Ettav de viktigaste systemen f¨or att garantera dessa krav ¨ar skyddssystemet. Syftet meddetta examensarbete kommer f¨oljaktligen bli att utveckla ett skyddssystem som f¨orlitarsig p°a Commerciall-o↵-the-Shelf (COTS) komponenter och som dessutom tar h¨ansyn tillskyddssystems funktioner. Fr°an detta skyddssystem kan det p°avisas att det ¨ar m¨ojligt attunder ett begr¨ansat tidsspann uppfylla marknadens krav utan att ¨aventyra tillf¨orlitlighetenoch s¨akerheten.Detta projekt innefattar utvecklingen av ett riktat ¨overstr¨omsskydd och ett jordfelsskydd.Utvecklingsprocess bygger p°aen modellbaserad design, som omfattar faserna prestandakrav,konstruktionsfas, implementering och prestandatest av systemet. Som en del av detta arbetekommer varje steg beskrivas utf¨orligt och genomf¨oras. MATLAB/Simulink anv¨andessom utvecklingsverktyg, eftersom den har st¨od f¨or modellbaserad design. De prestandakravsom anses ¨ar f¨or det mesta baserad p°a IEC 60255-151 standarden. Den utvecklade skyddsalgoritmenimplementerat i ett Linux system i realtid, gr¨anssnittet f¨or processen ¨arbaserad p°a EtherCAT protokollet och deras korresponderade I/O moduler. Testfasen ˜A¤rindelat i fyra olika tester kallade prestandatest, typtest enligt IEC 60255-151, realtidstestoch utv¨ardering av EMC prestandan av de anv¨anda I/O modulerna.Resultatet av prestandatest visar att en IEC 60255-151 kompatibel l¨osningen g°ar attuppn°a. Dessutom visar prestandatestet att de utvecklade skyddsfunktionerna fungeradesom planerat f¨or olika fel scenarion. Realtidsprestanda av skyddssystemet beh¨overemellertid ytterligare analyseras och anpassas f¨or att uppn°atillfredsst¨allande resultat.

Utfört examensarbete undersöker vinkelfelet i mätkretsen för riktade jordfelsskydd och hur det påverkar dess felbortkoppling. Uppkomna vinkelfel i mätkretsen kan påverka det riktade jordfelsskyddet så att verklig felström och uppmätt felström inte stämmer överens, vilket kan leda till uteblivna eller obefogade felbortkopplingar. Vattenfall ställer krav på att vinkelfelet får uppgå till max ±2 grader för mätkretsen. Eftersom vinkelfelet i många fall har en hög påverkan på jordfelsskyddets noggrannhet undersöks vad Vattenfalls vinkelkrav egentligen innebär. Största orsaken till vinkelfelet uppstår oftast i strömtransformatorn och därför undersöks hur mycket två strömtransformatorer med olika klassificeringar som är vanliga i elnätet påverkar vinkelfelet i mätkretsen. Jordfel är det vanligast uppkomna felet i mellanspänningsnät och dess storlek beror till stor del på hur mycket kapacitivt bidrag som finns på linjerna samt värdet på nollpunktsresistorn. Det kapacitiva bidraget från linjen kompenseras centralt i fördelningsstationen och ibland lokalt ute på ledningen. Den högst tillåtna centralt kompenserade delen av en linje får vara 30 A, vid reservdrift av en linje kan denna del uppgå till 60 A. Vinkelfelet har en högre påverkan vid stora kapacitiva bidrag och vid låga värden på nollpunktsresistorn. I många fall sitter det flera riktade jordfelsskydd på samma linje där selektivitet alltid eftersträvas. Vinkelfelet kan ha en negativ påverkan på denna selektivitet. Genom beräkningar, simuleringar och provningar har ett antal slutsatser dragits. Vattenfalls vinkelkrav ger en otydlig bild angående tillåten påverkan på jordfelsskyddet. Med rätt val av strömtransformator påvisas att det troligtvis är möjligt att skärpa vinkelkravet. För att minska vinkelfelets påverkan kan den högst tillåtna centralt kompenserade delen minskas och/eller öka värdet på nollpunktsresistorn. En beloppsselektivitet på 1000 Ω kan inte alltid tillämpas då vissa fall kräver en beloppsselektivitet på 2000 Ω. Genom att sätta nollpunktsspänningen som utlösningsvillkor och nollpunktsströmmen som frigivningsvillkor kan enligt studien troligen ett noggrannare jordfelsskydd uppnås.
This bachelor's thesis examines the angular error in the measurement circuit for directional earth-fault protection and how this error affects the fault disconnection. Angular errors in the measurement circuit can affect the directional earth-fault protection in such a way that the real fault current and the measured fault current do not match. This can lead to missed or unwarranted fault disconnections. Vattenfall has a requirement which states that the angular error must not exceed ±2 degrees for the measurement circuit. Since the angular error in many cases has a high impact on the earth-fault accuracy, an investigation concerning what Vattenfalls angle requirement really means. The main cause of the angular error usually occurs in the current transformers and therefore two commonly used current transformers in the grid with different classifications and their impact on the angular error in the measurement circuit are examined. Ground fault is the most common fault which occurs in a distribution network, its size depends largely on the amount of capacitive current which the grid contributes with as well as the size of the neutral grounding resistor. The capacitive contribution of the grid compensates centrally in the distribution station and sometimes locally on the line. The maximum permitted centrally compensated part of a line is limited to 30 A, this central part can go up to 60 A in case the line needs to be fed from a second distribution station. The angular error has a higher impact if the capacitive contribution is high and for low values of the neutral grounding resistor. In many cases more than one earth-fault protection are found on the same line, in these cases selectivity is always pursued. The angular error may have a negative effect on the selectivity. By calculations, simulations and tests a number of conclusions can be drawn. Vattenfalls angle requirement gives an unclear picture concerning the permitted impact on the earthfault protection. Moreover selecting the correct current transformer demonstrates that the angular requirement can probably be sharpened. To reduce the influence of the angular error the maximum permitted centrally compensated part be reduced and/or the value of the neutral grounding resistor can be increased. A selectivity of 1000 Ω can not always be applied since certain cases require a selectivity of 2000 Ω. By setting the zero sequence voltage as the trigger condition and the zero sequence current as the realese condition, according to this study it may be possible to achieve a more accurate earth-fault protection.

Master's thesis deals with use of electronic instrument transformers (sensors) in the protection system in medium-voltage substation. Substation consists of 2 incoming feeders, 2 outgoing feeders for motors, 2 outgoing feeders for power transformers, measuring, bus coupler and bus riser feeder. Incoming feeders are connected to distribution system E.ON by cable lines which were proposed. Protected machines (power transformers and motors with rated power) are connected to switchgear panels of UniGear ZS1 type by cable lines too. Proposed protection system is based on the short-circuit conditions, standard CSN 33 3051 recommendations as well as theoretical backgrounds acquired from technical papers and other publicated literature according to the bibliography. For selected protection functions are defined their parameters. Control, monitoring and protection functions provides REF 542plus relay. Consequently, secondary tests which are part of the commissioning, are given in the practical part of thesis. Secondary tests were performed by relay test system FREJA 300 by Megger. Results of tests are displayed in tripping characteristics.

The aim of this Master´s thesis is use of instrument transformers and sensors on field of industry protection. We will compare current and voltage transformers, current sensor – based on Rogowski coil, voltage sensor – based on voltage divider. By this measure devices, we can monitoring values of analog quantities in medium voltage switchgear. It is impossible to compare, measure and analyze without this measure devices. There is protection terminal REF542plus, which can compile this values. The REF542plus ability are measuring, monitoring, remote control and protection. First, we will discuss about theory of sensors and convential instrument transformers and analysis of analog signal. We will compare analog input channel on sensor´s analog module and transformer´s analog module. There are few differences between type of analog modules. For analog signal analysis are important frequency filters and Analog/ Digital Convertor (sigma-delta). We will describe functions and options of REF542plus. In practical part of this project, we will test protection functions of protection terminal. First, protection terminal will be connected to sensors. Second protection terminal will be connected to transformers. For testing we chose Earth-fault directional protection and differential protection. We will make only secondary tests. That´s mean, input analog quantities to REF542plus will be simulated by tester. In all we will verify quality of protection. We will focus on lower settings of protection and we will inject protection by low current. Objectives are testing of trip characteristics and measuring of trip time.