Current Transformers

This paper presents the comparative advantage of using GRP as material for compact secondary substations (CSS). The analysis is done based on calculations of the expected lifetime of the CSS by processing the measurable top oil temperature of the transformer. The benefits are compared for the equipment in terms of loss of lifetime for three different enclosure materials: glass-fiber-reinforced polyester (GRP), steel and concrete.

This paper presents a new methodology for evaluation of the inuence of instrument transformers (ITs) on performance of protection system. Instrument transform- ers are responsible for delivering accurate power system cur- rent and voltage replicas to protective relays. However, both theoretical research and eld application have shown that, due to their characteristics, conventional ITs may degrade relay performance signicantly . So far, various studies in- vestigated many aspects of the mentioned inuence. The methodology presented in this paper takes systematic ap- proach to the problem: it examines possible criteria and de- nes procedure for evaluation of the inuence. An applica- tion of the methodology is presented, along with the results. Suggestions for the improvement of application of conven- tional instrument transformers are also given.

This paper discusses test set up and methodology which may be used for wind power plant (WPP) protection system evaluation. The test set up cosists of a digital simulator, a number of physical relays and recorders, as well as software for modeling, simulation, signal editing, etc. Correct operation of the WPP protection system is crucial during grid disturbances to prevent unwanted power source disconnection. Since there are no standardized requirements or methodology for testing WPP protection system, evaluation of WPP condition impacts on protective relay operation is challenging. This paper discusses test requirements and test methodology to perform the evaluation in a standardized and comprehensive manner.

Las mediciones eléctricas experimentaron un desarrollo significativo desde el inicio de las aplicaciones eléctricas, tanto en el campo de la energía como en el de las comunicaciones. Los primeros cables telegráficos submarinos impulsaron el desarrollo de galvanómetros y puentes de medición de resistencia. A su vez, la expansión de la energía eléctrica estimuló avances en las mediciones de tensión, corriente y potencia.
En Uruguay, los primeros pasos se dieron con la implementación de cursos universitarios sobre estos temas, la creación de laboratorios y el inicio de la investigación y el desarrollo. Esto fue impulsado principalmente por la Facultad de Ingeniería de la Universidad de la República y la empresa eléctrica estatal UTE.
Este trabajo, dividido en dos partes, presenta en esta primera parte los desarrollos entre los comienzos hasta la década de 1960. Fue durante este período que se consolidó la estructura de los laboratorios nacionales y se definieron las normas básicas para las magnitudes más relevantes para el país. En una segunda parte se analizará el desarrollo de las mediciones eléctricas desde esa época hasta la actualidad.

The connection of generation to distribution networks may cause problems with existing protection schemes, while development of new protection schemes can facilitate an increase in generation capacity. The design and evaluation of a distribution network protection scheme based on distance relays is described. The scheme provides primary and back-up protection of 11 kV circuits. In the UK, voltage transformers and communication schemes are seldom installed on 11 kV circuits. Hence the distance relay restraint signal (voltage) is measured at the secondary winding of a distribution transformer (11/0.433 kV) to reduce costs. The development of the distance relay algorithm is discussed and a selection of simulation test results provided to illustrate the relay performance under fault conditions.

Medium Voltage (MV) Switchgear is an essential component in the electric power distribution system with a working voltage of 20 kV. MW Switchgear consists of Circuit Breaker (CB) and Voltage Transformer (VT). VT is one component that often fails in MW Switchgear in the power distribution system, where conditions cause the VT iron core to saturate. This saturation zone will make whatever capacitance reactance value ( ) that generated from the power system network will be the same value as the inductive reactance value of the inductance VT ( ), which causes the impedance value to be zero. A very wide frequency range will be able to trigger a ferroresonance which results in a large current flowing on the primary side of VT and has the potential to cause failure in VT and MV switchgear, characterized by an explosion. This research will focus on the main causes of ferroresonance emergence due to external disturbance, 20kV VT specification and MV Switchgear. Ferroresonance simulation is c...

The aim of this project was to detect and locate the single ground failure lines that occurs in medium voltage (MV) networks on the transmission lines (TL). Compared with anther faults, single line-to-ground (SLG) is the most frequent. The neural network (NN) algorithm was advanced in order to discover and locate SLG faults. The network is simulated through simulated numerous defects at various locations, as well as changing earth resistance from (or 100 Ω) to TL to gather all of the data. In the electromagnetic transients' program (EMTP) program software, the existing fault have been measured. In addition, the waves were evaluated by utilize MATLAP's fastfourier-transform to calculate the waves of top three of them, On the MV network are fifty hundred faults are simulated all data in the neural network at MATLAB were trained and examined to improve the NN algorithm according to this data. Comparing all the simulated location faults that have been applied with those all locations detected in the NN algorithm, the overall error between them has been found to be very low and not to exceed 0.7. The Simulink circuit was created from this algorithm and checked in order to predict each failure could occur in the future in the MV network.

This paper presents the TrafoGrade system, developed by Energo-Complex Ltd. The main purpose of this tool is to aid a decision-making process regarding the operation of power transformers. The system consists of four modules, the most important being a multi-parameter evaluation of the technical condition of a transformer. The second is an assessment of importance of the unit, which concerns things such as energy security, technical possibilities of a transformer renovation or replacement, as well as reliability of the power supply and costs of its absence. The third module aims to determine prospects for operation of each unit, with an emphasis on technical and economic factors. Lastly, the data is processed by a computer system to support the decision-making process for transformer population management. The article presents an example of implementation of this system in a power distribution company in Poland

ABSTRACT
Ferroresonance in low-voltage networks poses significant challenges to transformer performance, leading to nonlinear oscillations, overheating, and potential failure. This issue is prominent in Nigerian distribution transformers due to frequent switching, aging equipment, and poor grounding. Despite existing system-level mitigation, transformer design optimization for ferroresonance resilience remains underexplored. This study focuses on the multi-objective optimization and development of a 30 kVA low-voltage transformer for improved ferroresonance resilience in Nasarawa state, Nigeria. Utilizing a combined Taguchi-FEM approach, key design parameters like core area, core material, and flux density were optimized, minimizing energy losses and enhancing performance. MATLAB simulations revealed that the optimized transformer had superior resilience, reducing THD from 13.57%–16.78% in the baseline to 3.28%–4.12%, well within IEC standards. Voltage spikes were lowered by 25%, and core saturation reduced to 19.2%, compared to 42% in the baseline. FEA confirmed a 27% reduction in core losses, while OC and SC tests demonstrated an efficiency of 97.15%, outperforming the baseline’s 95.5%. Recommendations include integrating advanced design optimization and enhancing local manufacturing practices. Future work should explore real-time ferroresonance detection and adaptive control systems to mitigate risks further.

A concern with the isolation transformer in a dual active bridge (DAB) DC-DC converter is the DC bias in magnetization. This paper proposes a fluxgate-based current sensor to measure the DC component mixed with a large, high-frequency AC current. Compared with a commercial Hall effect current sensor, the proposed sensor significantly reduces measurement error. This paper presents the working principle and design considerations. A prototype is demonstrated for DC bias elimination control in a DAB converter. 1

The main aim of this paper is to expose a simple and low cost device that allows to measure high frequency cur- rents. The Rogowski coil is a flux-to-voltage transducer for non-intrusive current measurement. Its use is usually asso- ciated to an external circuit for integrating ...

Magnetic field sensors can be used to detect fault detection and location effectively. Quick fault detection can help protect equipment by allowing the disconnection of faulted lines before any significant damage is done. A variety of algorithms continue to be developed to perform this task more accurately and more effectively. Particularly fault impedance (based algorithms) require both current and voltage information. However, it is possible to monitor a transmission system without using current or voltage transformers through the analysis of the magnetic field near the conductors. Since each conductor in a transmission line creates a magnetic field due to the current pass through it. Magnetic field sensors are used and tested using MATLAB through analyzing wave fault detection and location as there is a possibility of analyzing the transmission line system based on the resultant magnetic field produced. The results show that the magnetic field sensors are a viable tool for power transmission line fault detection, so this method is highly recommended to be used based on its efficient and accuracy.

The article presents the results of the research on inductive current transducers in the form of a uniform winding non-magnetic ring with a rigid and flexible construction encompassing the flow of processed current in the frequency range of up to 150 kHz. The results for the developed transducer were related to the results obtained in simulations conducted on the transducer simplified model. The frequency tests of this type of transducers are of key significance in the assessment of the applicability of a given transducer in the measurements of network signals with high-order harmonics, and particularly in the assessment of the construction capacity of inductive current transducers in the form of the Rogowski coil.

This paper presents a novel technique for three phase transformer protection, which the method effectively identify magnetizing inrush currents from internal fault currents. This technique employs symmetrical components. When transformer is switched, inrush current happens. This current have some features, which it is enough for identify itself. In this paper, by extract these features, a new criterion is proposed to discriminate inrush currents from internal faults in power transformers. In faulty time such as switching or short circuit, the value of negative sequence for differential current is different from positive sequence value. Helping this feature, new criterion is introduced. Simulations show this criterion works properly in over-flux and CT saturation condition too. The simulated results presented clearly, the proposed algorithm can accurately discriminate between an internal fault and a magnetizing inrush current in power transformer protection in all cases.

People often believe that power factor/dissipation factor testing at power frequency (50/60 Hz) usually exhibits a flat response as a function of test voltage if the insulation is in good condition. Dielectric Frequency Response, DFR is the extension of power factor testing except that the measurement is performed from 1 kHz down to typically 1 mHz. It is a very useful tool for evaluating the moisture content in solid insulation of HV and EHV components such as power transformers, bushings, instrument transformers and PILC cables. The voltage dependent phenomenon also called "the Garton effect", caused by paper absorbing electric charges in oil is investigated. The application of DFR in HV and EHV substations required a conceptual analysis of the phenomenon to better interpret the condition of the insulation system while increasing the signal to noise ratio to minimize the effect of surrounding interference. As a result of this work, authors provide practical recommendations regarding test voltages and frequency ranges to be used under high interference environments. The wide application of the method is supported with experimental field data.

The paper discusses the distribution of the thermal field in the magnetic core of a mono-phase transformer aggregate including the main and the voltage-adding transformer. The main aim of the analysis is to locate the most overheating section of the magnetic system studied and to investigate this overheat in the different overloads. The experimental data are compared with the simulation ones and the resulting error is less than 5 %.

The load losses of the transformers increase considerably with the presence of harmonic distortion in the currents. Its increase can be determined using an analytical method based on ANSI/IEEE Standard C57.110. On the other hand, when it comes to three-phase banks with transformers of different capacities, delta connections, or incomplete connections, the analytical method does not allow the losses to be accurately estimated, which is why digital simulation is necessary. This work presents an adjusted model to determine the load losses in a three-phase bank of three single-phase transformers with different connection schemes. The model allows for determining load and electrical losses and calculating total additional losses. It is also possible to decide on the load capacity of the bank's transformers, the power factor, and the efficiency with which they operate under these conditions

The paper deals with the recording and analysis of electric quantities waveforms from the components of a synchronous generator. The quality parameters of powers are determined in distorting and unbalanced regimes. Based on the relations used for the determination of the quality factors of electric quantities and respectively for the determination of the active and reactive powers, an analysis is made. It is concerned with the waveforms from: the main generator stator, the auxiliary generator stator before the fully controlled rectifier with thyristors and from the main generator rotor. Possible interdependencies between these quantities are determined.

The paper presents the influence of a distorting element (D) from a power group over the lifetime of some test voltage transformers (T). D is a three phase rectifier fully controlled with thyristors and T are used to monitor the power group and measure the voltages across the main generator terminals. One presents the structure of the monitored power group's components, focusing on the electric quantities that disturb the operation of T. A short description of the complex data acquisition system specially conceived for this purpose is provided. Recorded quantities corresponding to the voltages and currents from the main generator terminals are presented. Data corresponding to the currents recorded at the excitation transformer terminals are also analyzed. The recorded quantities are processed and the voltage/current harmonic components are presented as graphs or tables. One determined various categories of powers flowing through the main generator and respectively through the primary winding transformer. The power flow is distinctly considered along fundamental and respectively along higher harmonics. Significant conclusions are drawn with respect to their influence over the voltage transformers.

In oil immersed power transformers, tank resonance can add a significant contribution to the generated noise. In the current study, we present a systematic procedure to first detect the resonance in the tank and then controlling its effect on noise. This is done by either shifting resonance frequencies or damping the resulting vibrations via optimizing additional outer stiffeners. The procedure consists of measurement, simulation and modelling. The study shows the ability to predict the natural frequencies of the tank with a high accuracy, which is validated by applying hummer-test in specific places on the tank walls. Noise measurements are conducted before and after applying the outer stiffeners on the transformer walls with and without radiators. Results show that by following the presented procedure for a case study transformer it is possible to reduce the noise by about 5 dB. Introduction The transformer tank is mechanically, acoustically and electromagnetically connected to th...

The paper deals with the recording and analysis of electric quantities waveforms from the components of a synchronous generator. The quality parameters of powers are determined in distorting and unbalanced regimes. Based on the relations used for the determination of the quality factors of electric quantities and respectively for the determination of the active and reactive powers, an analysis is made. It is concerned with the waveforms from: the main generator stator, the auxiliary generator stator before the fully controlled rectifier with thyristors and from the main generator rotor. Possible interdependencies between these quantities are determined.

The safety of the electrical energy supply is one of the most critical issues for companies engaged in production. The internal distribution network, which will provide the energy for the production elements, is essential. Power Transformers, which energize the loads fed from the electricity distribution network, are backed up in a way suitable for parallel operation for energy supply security. As a result of this situation, in case of a predictive failure in one of the transformers, energy supply safety is ensured since the other transformer is designed to carry the load alone. When one of these identical transformers is damaged, the relative short-circuit voltage of the new transformer to be integrated into the system may be different. The transformers with different short-circuit voltages are not shared their load equally. For this reason, the total amount of load that they can be loaded, the relative short-circuit voltage that will occur, and the load rates they are loaded change. In this study, a detailed analysis of two transformers with different relative short-circuit voltages and operating in parallel was made, both theoretically and as a result of the application, with the information obtained through the SCADA program. The theoretical values were calculated as a result of the analysis, the SCADA values were compared, and the margin of safety between them was established. It has been shown that the safety margin will protect against overload on a low short-circuit transformer. After the commissioning, the load rating needs to check and it can be regulated in line with the load rates that will occur after commissioning.

Methods for performing tests specified in IEEE Std C57.12.00-1993 and other standards applicable to liquid-immersed distribution, power, and regulating transformers are described. Instrument transformers, step-voltage and induction voltage regulators, arc furnace transformers, rectifier transformers, specialty transformers, grounding transformers, and mine transformers are excluded. This standard covers resistance measurements, polarity and phase-relation tests, ratio tests, noload-loss and excitation current measurements, impedance and load loss measurements, dielectric tests, temperature tests, short-circuit tests, audible sound level measurements, calculated data, and certified test data.

An outbreak of severe acute respiratory syndrome coronavirus infection occurred in Wuhan, China at the end of December 2019 and spread of this virus already reached to almost 210 countries around the world. WHO declared COVID-19 as ‘global pandemic’ on 11 March, 2020 and accounted South Asia as the high-risk region. Nepal, a landlocked country bordering two most populous countries, India and China, was expected to have high number of cases of COVID-19 due to its proximity to the highly infected country China, and lately spreading country India. Also, many of the Nepali people are engaged in the businesses related with China and India. However, there has been very few reported cases in Nepal. The first case was reported on 24th January 2020, one and half months after the first case was confirmed in China. It took almost three months for the number of cases to reach 45 and to kick off the community spread stage of the pandemic. This research presented the detailed situation of the cas...

The aim of this research was to study the epidemiological characteristics of cervical cancer in Uzbekistan, to compare the data obtained with studies conducted in the world. Define a strategy for preventive measures aimed at preventing cervical cancer by introducing a cervical cancer screening system, as well as introducing vaccination against human papillomavirus infection.

An experimental, non-destructive and non-invasive technique for the quick and accurate detection of the internal conditions of electromagnetic reactors for HVDC systems has been used successfully. This technique involves the application of mechanical vibrations, in scanning to find resonance frequencies and the maintenance of vibrations in these frequencies with discrete evaluation of the electrical impedance of the reactor. With the vibrations, it was identified that the unit contained moving and non-static parts as expected in healthy units. And yet, those moving parts could be moved permanently when vibrations in the resonant frequencies were applied, in safe amplitudes so as not to cause other damages.

A concern with the isolation transformer in a dual active bridge (DAB) DC-DC converter is the DC bias in magnetization. This paper proposes a fluxgate-based current sensor to measure the DC component mixed with a large, high-frequency AC current. Compared with a commercial Hall effect current sensor, the proposed sensor significantly reduces measurement error. This paper presents the working principle and design considerations. A prototype is demonstrated for DC bias elimination control in a DAB converter. 1

Se presentan los modelos de transformadores de corriente, monofásicos y trifásicos, utilizando MATLAB/ SIMULINK. Estos modelos pueden ser conectados con los modelos de la biblioteca de Power System Blockset del propio SIMULINK para completar los modelos y análisis relacionados con las protecciones eléctricas. Las máscaras dinámicas realizadas permiten una flexibilidad superior para el usuario, dado que pueden configurar el modelo según las necesidades de la investigación que se realiza. Palabras clave: transformadores de corriente, modelación y simulación, SIMULINK TIn this work are shown the models of the three-phase and single-phase current transformers using MATLAB/Simulink. Theses models can be connected to the models that belong to the Power System Blockset to complete models and analysis related with Protective Relaying. The dynamic masks made in this work, allow a major flexibility to the users, because of now, the users can configure the model depending of the researching goals.

This paper describes the instrumentation systems and test methodologies used for simultaneously measuring voltage and current harmonic magnitudes at the harmonic source and at remote feeder locations on each of two distribution systems. Results obtained from the two sets of field tests are presented and recommendations are offered for measuring distribution system harmonics.

This paper presents an approach for assessment of effect of different switching transient on current transformer saturation. This has been achieved by wavelet transform. Secondary signal of current transformer is captured and decomposed wherefrom approximate and detail coefficients have been estimated. Then different useful parameter like Skewness of approximate and detail coefficients are determined. Simulated result shows significant changes of those values for different conditions, wherefrom, saturation of current transformer is detected and switching time corresponding to the switching transients at the primary side which causes the saturation is assessed.

A series of previous papers has provided information regarding the arc flash hazard and methods of calculating its potential impact on persons working on or near the equipment. This paper extends that base of information by focusing on the arcing current level and duration in low-voltage circuits protected by circuit breakers (CBs). It describes a method of calculating incident energy and the flash protection boundary due to arcing occurrences in equipment protected by CBs. This method provides convenient procedures for determining these values for generic situations in which some details of the CB are not known. Further, it provides a process for determining these values in typical feeder and branch circuit applications involving common transformers and cable sizes and lengths. The values are needed to determine safe work practices and appropriate Personal Protective Equipment to comply with NFPA 70E, Standard for Electrical Safety Requirements for Employee Workplaces.

I welcome the growing interest in arc-flash studies and thank Stokes and Sweeting for their interesting paper [1]. R. Lee certainly made many simplifying assumptions. The great value of his paper is that it succeeded in relating theoretical electrical power system arcing fault energy to the possible incident energy on employees in a quantitative way. Granted that it was crude, but it was the starting point for all arc-flash incident energy studies and programs. The Stokes and Sweeting paper is very critical of Lee's analysis and model. One test of the value of a model is looking at how well it compares to other models. Many people have found that Lee's method gives results that are remarkably close to the results obtained by applying IEEE 1584 to 480-V cases. In the 1584 guide, the Lee method is recommended only for cases over 15 kV or with bus spacing greater than 150 mm, and results are recognized to be very conservative for those cases. It should be noted that almost all industrial, commercial, and utility generation plant cases encountered in actual arc-flash studies involve possible arcs in enclosed equipment with tight bus spacing and a system voltage under 15 kV. IEEE 1584 offers an empirically derived model for those cases. Under arc modeling, [1] speaks of arcs self extinguishing in < 10 or < 40 ms. In the testing sponsored by the P1584 Working Group, we also experienced this problem. Depending on voltage, electrode spacing, box size, and perhaps other factors, the arc may or may not be sustained-the arc may last only until the trigger wire is burned away. However, test setups can be changed so that the arc will be sustained until switched off. Only test results obtained while using these setups were included in the P1584 Working Group test database. This enabled the development of a model that simulates the realworld case where protection may be set for a relatively long time. Reference [1] describes tests involving long horizontal electrodes pointed to the location where an employee might stand when operating the equipment. In these tests, the arc extended a considerable distance from the electrode tips toward the likely employee's location. While the authors of [1] told me that this type of equipment is used in Australia, I have never seen it. Later testing by others has been conducted to compare the results of testing with horizontal electrodes of long lengths and very short lengths, of the type that is common in standard North American and European equipment. These tests showed that the possible arc projection distance is much shorter for equipment with short horizontal buses. The IEEE Standards Association has approved the development of a second edition of the 1584 guide to extend the range of applications and to improve the preciseness of the calculations relative to realworld equipment. This next edition is expected to address different bus configurations and additional arc-flash hazards. A test program is being planned by a joint IEEE/NFPA Collaboration.

In this paper, design and optimization method of a three-phase dual-active-bridge DC/DC converter is discussed. Three single phase transformers connected in star-star configuration were designed with large leakage inductance aiming to eliminate the need for external inductors. Switching frequency, peak flux density, number of turns, number of layers, etc., were optimized using non-linear programming technique for minimizing the overall converter loss. Experimental results on a 10 kW prototype show that the optimized converter can operate efficiently an efficacy of up to 98.65% and a low-temperature rise of less than 70 degrees Celsius on both transformers and semiconductor devices.

Distribution Network (DN) face sundry transient conditions, resulting in incorrect detection of fault and maloperation based on load type, capacity, and number of transformers in the operation mode. In this paper, a novel method is proposed to provide separability while increasing fault detection capability from other transient conditions in the DN, all in all by using the recorded currents at the beginning of feeder. Using current components of Park transformation, the method proposes a novel pattern, based on the graph of component d compared to component q of the current recorded at the beginning of the feeder, for analyzing transience in normal and faulty operation modes of the network. Fault curves and other transient trends of the DN, such as inrush current, inherit different characteristics that can be detected through classification. In this method, healthy and faulty operating modes are well distinguished in less than 2 ms. A sample of DN together with a real distribution feeder of Iran's Electricity Distribution Company is used to evaluate the proposed method. Simulation results verify the validity and accuracy of the proposed method.

Utilising powder cores in many power electronics applications have gained much attention due to the attractive magnetic properties of powder core materials. However, the magnetic flux density distribution is non-uniform along the core because the flux is dependent on the core geometry and due to the low relative permeability of the powder core material. The non-uniformity of the magnetic flux density distribution may cause huge calculation errors of core losses. Understanding the effect of the magnetic flux non-uniformity in the powder cores allows the circuit designer to accurately estimate the core losses in powder cores. This work addresses the negative effect of the inherent non-uniform magnetic flux density distribution on the core loss. Furthermore, an equivalent circuit to consider the non-uniform of the magnetic flux density distribution is proposed. The proposed circuit enables the core loss to be estimated more precisely. A reduction of 12% in the core loss measurement error has been reported while utilising the proposed circuit compared to traditional equivalent circuits. Along with the theoretical discussion, finite element method simulation and experimental results are also presented to evaluate the proposed core loss calculation method.

The transmission line of electrical energy generated by the power plant is usually located far from the load center to be distributed to the community. The substation is part of a distribution transmission line that acts as a control center and consists of a collection of extra high voltage equipment. Routine maintenance of the power transformer as the main equipment of the substation must be scheduled so that its performance remains reliable. The proposed method of this research is to analyze the condition of the transformer through testing when it is off, to the calculation of the transformer ratio to determine the condition of the transformer windings using the calculation of the formula and measurement of the Raytech Transformer Turn Ration measuring instrument. In this research, the Raytech Transformer Turn Ratio measurement tool is used to determine the ratio of the winding input voltage of 20,000 volts and the output voltage of 400 volts on the power transformer. At a voltage...

Power inductors are used for compensating VAR generated by long EHV transmission lines and in electronic circuits. For the EHV-lines, the rating of the inductor is decided upon by techno-economic considerations on the basis of the line-susceptance. It is a high voltage high current device, absorbing little active power and large reactive power. The cost is quite high-hence the design should be made cost-optimally. The 3-phase power inductor is similar in construction to a 3-phase core-type transformer with the exception that it has only one winding per phase and each limb is provided with an air-gap, the length of which is decided upon by the inductance required. In this paper, a design methodology based on sequential gradient search technique and the corresponding algorithm leading to cost-optimal design of a 3-phase EHV power inductor has been presented. The case-study has been made on a 220 kV long line of NHPC running from Chukha HPS to Birpara of Coochbihar.

As the key metering equipment of the high-voltage transmission network, the high-voltage potential transformer (HVPT) needs manual maintenance to ensure that its operating status complies with relevant regulations. Due to the requirement of power outages, the manual maintenance could only be conducted at regular intervals and the measurement error of HVPT remains unknown during the operation. To address the issue, this paper proposes an on-line anomaly detection method for the measurement error of HVPT with high applicability to the complex power system. By taking advantage of the multi-bus structure, the abnormal HVPTs can be detected and located based on the in-phase relation between the HVPTs connected to the same phase and the three-phase relation within the HVPT groups. This method is data-driven and will not affect the operation of the power system. The effectiveness of the proposed method is verified in a 220 kV substation.

The system presented in this document aims to reduce the penalty for Industrial Units using automatic power factor correction units. The microcontroller used in this project is Arduino Uno. Two zero-cross detectors are used to detect voltage and current zero-crossings. The time dif erence between the zero voltage pulse and the zero current pulse is created by the appropriate operational amplifier circuit in comparison mode and fed to the two interrupt pins of the microcontroller. The program takes over to open the appropriate number of relays from its outputs and insert a shunt capacitor into the load circuit until the power factor reaches unity. The capacitor bank and relays are interfaced with the microcontroller using a relay driver. It shows the delay time between current and voltage on the LCD screen. In addition, this project can be developed by using thyristor control switches instead of relay control to prevent contact pitting, which is often encountered in switched capacitors due to high inrush current

Current transformers (CTs) are used to transform large primary currents to a small secondary current. Since most standard equipment&#39;s are not designed to handle large primary currents the CTs have an important part in any electrical system for the purpose of Metering and Protection both of which are integral in Power system. Now a days due to advancement in solid state technology, the operation times of the protective relays have come to a few cycles from few seconds. Thus, in such a scenario it becomes important to study the transient response of the current transformers as it will play a vital role in the operating of the protective devices. This paper shows the steady state and transient behavior of current transformers and how it changes with change in connected burden. The transient and steady state response will be captured using the data acquisition software LabVIEW. Analysis is done on the real time data gathered using LabVIEW. Variation of current transformer characteri...

Power transformer protection performs an essential role in power systems, ensuring a reliable power supply to the customers. One of the main challenges in differential protection of the transformers is to correctly discriminate inrush currents from internal faults and prevent the maloperation of the differential relay. In this regard, a novel differential protection method is proposed, which decomposes the differential current signal to multiple energy levels through the multi-resolution analysis (MRA) and selects the most useful feature to feed to the bidirectional gated recurrent unit (BIGRU) to classify the events. The use of the BIGRU results in the high accuracy and low implementation complexity of the proposed approach. Various simulations carried out on a 70 MVA transformer demonstrate that the proposed approach has an accuracy of 99.70% in discriminating inrush currents from internal faults in less than one-eighth of the power cycle.

Power transformer protection performs an essential role in power systems, ensuring a reliable power supply to the customers. One of the main challenges in differential protection of the transformers is to correctly discriminate inrush currents from internal faults and prevent the maloperation of the differential relay. In this regard, a novel differential protection method is proposed, which decomposes the differential current signal to multiple energy levels through the multi-resolution analysis (MRA) and selects the most useful feature to feed to the bidirectional gated recurrent unit (BIGRU) to classify the events. The use of the BIGRU results in the high accuracy and low implementation complexity of the proposed approach. Various simulations carried out on a 70 MVA transformer demonstrate that the proposed approach has an accuracy of 99.70% in discriminating inrush currents from internal faults in less than one-eighth of the power cycle.

This study thoroughly studies overvoltages appearing on the isolated phase (s) of shunt reactor compensated transmission-lines when remaining phases are left energised. The voltage that appears on the isolated phase would settle to a steady-state component induced from the energised phases. This endures until all other phases are disconnected or the isolated phase is re-energised. Reactors with different zero-and positive-sequence reactances are less common but not rare. Taking this point into account, a general model is introduced for three-phase reactors involving those with interphase magnetic coupling. Accordingly, a rigorous analytical formulation is developed to prevent open-phase damaging overvoltages. As proposed, this is achieved by installing a suitable neutral reactor whose optimal value is obtained using the extracted closed-form equations. It is shown that in the case of shunt reactors with interphase magnetic coupling, open-phase overvoltages are more likely to arise even for small degrees of compensation. Based on the defined objectives, a range is determined for the neutral reactance in which no openphase overvoltage would appear. This provides a high flexibility in sizing the neutral reactor considering technical and economical limitations. The accuracy of the employed models and effectiveness of the optimised neutral reactance are further illustrated through extensive simulation studies using the electromagnetic transient program EMTP-RV.

This study presents an adaptive data window algorithm for fast and accurate signal phasor estimation. The proposed approach is based on weighted least error squares algorithm as well as variable data window estimation technique. An adaptive model is used for the input signal during the two stages. The first stage is considered to accelerate the relay first zone operation. This is done through applying a forgetting factor in the cost function computation, by which the effect of older samples on the estimation is reduced to decrease the initial inertia of the phasor estimator. The second stage starts one cycle after occurrence of the fault. This algorithm is used to improve the estimation accuracy and helps to obtain better estimation for the fault location. To verify the performance of the proposed algorithm, various simulation studies are carried out. The algorithm is also evaluated using some field data recorded from a high-voltage transmission system. The obtained results confirm accurate, fast and reliable response of the proposed algorithm. It not only accelerates the relay operation but also improves the digital filters' capability of reducing the estimation error because of power system frequency deviation, harmonics, inter-harmonics and decaying dc component.

One of the most important components of its role in power generation systems is generators. The Generator is a power generating machine,generated by receiving mechanical power and converting it to electricity. Any interference in the generator may interfere with the operation of the power plant system. Therefore, in a generator at the center of the plant would be equipped with a protective device that can protect the generator in order to avoid unwanted interference. One of them is by using Over Voltage Relay. Over voltage relay is a relay that works based on an increase in voltage reaching or exceeding its setting value.From analysis of protection system in the turbin generator quantity 118,2Vdc, produce voltage 7044 Vac in the no load condition. By giving load in quantity 2772 KW, so the voltage will be 6815 Vac.As much as using the load so the voltage which is plant will be so small. So it must be done by using voltage relay

The increasingly rapid development of technology has given rise to simulation methods used in circuit specifically in dynamic electricity. One of them is the NI-Multisim application which is useful for determining current and voltage values efficiently and effectively with a circuit design that is built first in the application. Research activities were carried out by simulating Khirchoff's law on NI Multisim by building a circuit scheme based on the circuit composition, namely resistance, voltage source and using voltage measuring instruments and current measuring instruments which are all arranged in such a way by referring to electrical circuit theory. The results of this research are that there is a difference in the total resistance value between the values in the circuit kit module practice and the use of Multisim. However, the difference is very small with an error of around 7.83% for the series-parallel circuit. The current value for each resistance which is connected in a mixed manner can be seen that the practical and theoretical values have an error value of 0% to 24.24% respectively located at R3 at the 6V voltage source and R2 at 12V. The current in I3 is equal to the sum of the current in I2 and the current in I1 for each specified voltage variation. The measurement values with the Khirchoff kit module are different from the NI Multisim simulation, but the differences are still relatively small, ranging from 6% to 28%.

In this paper, we propose a method for the identification of the differential inductance of saturable ferrite inductors adopted in DC–DC converters, considering the influence of the operating temperature. The inductor temperature rise is caused mainly by its losses, neglecting the heating contribution by the other components forming the converter layout. When the ohmic losses caused by the average current represent the principal portion of the inductor power losses, the steady-state temperature of the component can be related to the average current value. Under this assumption, usual for saturable inductors in DC–DC converters, the presented experimental setup and characterization method allow identifying a DC thermal steady-state differential inductance profile of a ferrite inductor. The curve is obtained from experimental measurements of the inductor voltage and current waveforms, at different average current values, that lead the component to operate from the linear region of the...

The increased availability and power of scientific visualization tools in recent years has made it possible to construct useful tools for examining complex physical phenomena. This paper illustrates how such visualization tools can be used to examine the influence that geometrical shape and material characteristics can have on the distribution of magnetic flux in some example ferrite cores.