Measurement Current Transformers Research Articles

Simulation and commissioning of a Faraday cup for absolute charge measurements of very high-energy electrons in-air at PEER

The Pulsed Energetic Electrons for Research (PEER) beamline at the ANSTO Australian Synchrotron comprises a 100 MeV linac injector that is currently being developed for ultra-high dose-rate, very high-energy electron radiotherapy research. Previously, dosimetry studies discovered a lack of reliable charge measurement to the in-air end station, though no change in response was recorded in fast current transformer measurements, the only available diagnostic device for measuring charge. This work describes the process of simulating and then commissioning a purpose-built Faraday cup to ascertain absolute in-air charge measurements at PEER. By combining simulation data with experimental results, the PEER Faraday cup is shown to possess a primary electron capture efficiency of (99.22 ± 0.10)%, with a net capture efficiency due to secondary electron emission of (97.87 ± 0.24)%. These results show the PEER Faraday cup performs as intended and, when scaled against simulations, will be suitable for measuring absolute charge at PEER.

Current trajectory coefficient based time domain line protection for battery storage energy stations

On account of distinctive fault signatures, the extensive integration of large-scale battery energy storage stations (BESSs) results in severe performance degradation of relaying protection. Firstly, the performance problems of classic current differential protection and recently proposed cosine similarity coefficient-based pilot protection are illustrated. Subsequently, the trajectories of two current pairs in two-dimensional space, i.e., fault path current and current on BESS-side, fault path current and current on grid-side, are described and relationship of these three currents is analyzed. On this basis, this paper presents current trajectory coefficient-based time domain protection algorithm for transmission lines connecting BESSs. It describes the basic principle of protection algorithm and designs the operating and restraining regions of two current trajectories. The authors widely assessed the performance of proposed protection algorithm under internal fault by varying fault location, type, resistance and operating state of BESS. Furthermore, the security of proposed protection algorithm was also tested under various nonideal conditions, including severe current transformer (CT) saturation, CT measurement error and outliers. The results indicate that proposed protection algorithm offers gratifying performance in operating speed, dependability, security and selectivity, and outperforms current differential protection and recently proposed pilot protection.

Development of a Generalized Scaled-Down Realistic Substation Laboratory Model for Smart Grid Research and Education

This paper introduces a physical scaled-down realistic substation laboratory model development for translational research and education in smart grids. The development of a substation panel with four 3-<inline-formula> <tex-math notation="LaTeX">$\phi $ </tex-math></inline-formula> feeders of 415 V, 65 A rating is described in detail. The developed substation model can be configured to realize seven widely used substation bus bar arrangements. A programmable logic controller (PLC) is used to create interlock mechanisms for mimicking the actual substation operation practices. Provision is made to realize the gang and independent pole operation of circuit breakers, the manual and remote modes of operation, and different types of current transformer arrangements. The substation panel can host up to 10 commercial IEDs, and multiple substation panels can be cascaded to form a bigger station using the master-slave configuration of PLCs. All the potential transformer and current transformer measurements, circuit breaker, isolator, and earth switch status signals are made available for connecting field devices. The developed substation model can be used for advanced research on substation automation using IEC61850, validation of new protection strategies, implementation and testing of new algorithms (such as topology processing, state estimation) for energy management systems (EMS) like how they get implemented in the field.

Perancangan Alat Monitoring Error Current Transformer (AMOR CT) Menggunakan Arduino Mega 2560 dan Cayenne IoT

Current Transformer (CT) is an important component that functions as a tool to regulate the amount of current that enters the kWh Meter on a 3-phase indirect measurement customer. To ensure the accuracy of measuring instruments, especially CT, it is necessary to check whether the installed CT still meets the standards. Current Transformer error (CT error) is the difference between the measured value on the secondary side and the actual value on the primary side of a CT measurement. This final project aims to design a tool that is able to provide information and record CT error value measurement data in real time and display it on the Cayenne IoT. This final project uses Arduino Mega 2560 with PZEM 004T module as a current sensor, GSM 800L module for Arduino connection with Cayenne IoT. Cayenne IoT is used to visualize the data so that the CT measurement conditions can be monitored. Each PZEM 004T will read current changes and the data will be processed by Arduino Mega 2560 and then sent to Cayenne Iot for display, making monitoring and data retrieval easy. After making and testing the tool, it was found that the design tool was able to send measurement results to the Cayenne IoT and was able to provide real-time information and record CT error value measurement data installed on the customer's electrical panel for evaluation materials with the expected measurement results with direct measurements contained in 0% - 0.3% difference in AMOR CT readings with Ampere Tang.

Fault location in overhead transmission line: A novel non-contact measurement approach for traveling wave-based scheme

Traveling wave fault location methods have gained considerable growth over the years, with the anticipation that power systems will be accurate and reliable everywhere. But the performance of classical traveling wave methods has focused only on traditional current transformer measurement in the literature till date. Therefore, in this paper, an innovative non-contact measurement of traveling wave formulation is proposed to achieve accurate fault location and time of arrival detection on a two-terminal overhead transmission line, since power cable naturally generates magnetic and electrical fields in the surrounding atmosphere. The proposed method solitary depends on the first two and successive time differences between the incident and reflective wave from the fault point of the transmission line. Thus, the proposed scheme does not depend on current transformer measurement that stimulates the accuracy and reliability of the conventional traveling wave fault location method. To ensure an accurate time of arrival waves detection, we exploit the magnetic field sensor array on each tower to measure the quality of current traveling waves generated on the transmission line and locate the transient disturbances as a result of a short circuit. By analyzing the line energization, a comprehensive fault analysis on a 500-kV line was simulated with PSCAD/MATLAB toolbox compared to the two-terminal classical method. The sensitivity analysis demonstrated that the proposed method is much accurate and reliable to be deployed and cost-effective, making it highly useful and efficient in comparison to the classical two terminals traveling wave method with an average error of 0.014%. The effectiveness of the proposed method was verified by laboratory experimental setup.

Measurement Current Transformer Error Compensation by ANN Methodology

Measurement current transformers (MCTs) are an important component in the measurement of electric power. In this era of deregulation, every power distribution company strives for maximum revenue. It could be possible if the errors present in MCTs are reduced. Maharashtra State Electricity Distribution Company (MSEDCL) is one of the power distribution utility in India interested to resolve its problems regarding MCT error compensation. In this article, the MCT error compensation problem was tackled for various operating conditions. These conditions include metrological properties of core, transformation ratio, burden, remanent flux and nature and quantum of load connected on the primary side of MCT. The MCT secondary side waveform is analyzed for various operating conditions, and from these data, the artificial neural network (ANN) is trained. Implementation of the compensation system and data acquisition is done using dSPACE 1104 software. Experimentation is performed in MSEDCL laboratory, and test results demonstrate the effectiveness of the proposed system.

Impact of inductive current transformers on synchrophasor measurement in presence of modulations

Instrument Transformers (ITs) are essential devices for all the measurement tasks, f.i. metering, protection and diagnostics, in electricity grids, since they scale voltage and current down to levels compatible with measuring instruments. At the input of Power Quality (PQ) instruments and Phasor Measurement Units (PMUs), inductive voltage and current transformers (VTs and CTs) are still the most used ITs, even if, their performance in presence of disturbances is not fully assessed. This paper analyses the impact of the inductive CTs on the measurement of fundamental synchrophasors, by a PMU, in presence of a particular class of disturbances, the undesired modulations on current signals. Experimental tests, on two different CTs, show that there are critical situations, where, even compensating CT systematic ratio and phase errors, 1) CT exceeds its accuracy class limit and 2) considering the sole contribution of CT, PMU performance stays very close to the error limits of the standards.

Current Transformer Accuracy Improvement by Digital Compensation Technique

Measurement current transformers (CTs) are extensively used for measurement of energy by power distribution utilities. In this paper, current transformer error compensation unit (CTECU) is developed which is specially intended for providing compensation to all types of measurement CTs. The proposed CTECU is based on determination and application of correction coefficients, which are computed by the ratio and phase angle errors data. Analytical foundation is effectively expressed along with the development of CT error compensation algorithm. CTECU is implemented online in laboratory on 1.0 class and 0.5 class of CTs. The experimental performance is found satisfactory under various operating conditions. The novelty of the proposed algorithm is that it is possible to make conversion of CTs from one class to another class.

LabVIEW‐based real‐time error compensation system for measurement current transformer using piecewise linearisation

This article describes the development of an error compensation algorithm for a measurement current transformer (CT). The flux-magnetising current loops are derived in the proposed algorithm to minimise the number of required loops for computation. At every sampling interval, the exciting current is obtained from these loops and then it is added to the measured secondary current to gain the corrected primary current. The performance is tested using MATLAB program and later, the same code is executed in LabVIEW environment. Performance analysis indicates that the proposed algorithm improved the accuracy of the measurement CT notably even with minimum loops. The experimental test results demonstrate that the compensator is capable to correct the accuracy of the measurement CT in remarkable manner.

An Improved Pilot Relaying Scheme for Shunt Compensated Transmission Line Protection Based on Superimposed Reactive Power Coefficients

The fault component power and energy based relaying schemes have limitation during double-phase to ground fault due to the mutual coupling effect. This article presents a superimposed reactive power coefficient (SRPC) based pilot relaying scheme for the protection of shunt compensated transmission line. SRPC of a phase is defined as the ratio of integrated superimposed reactive power (SRP) of that phase to the maximum magnitude of integrated SRPs among all three phases. If SRPC of any phase is found less than −0.5, an internal fault is detected and that phase is considered as a faulty phase. If no phase possesses SRPC less than −0.5, the fault is an external fault. The algorithm will start only if the superimposed differential current of any phase is found more than 50% of pre-fault differential current. The results are obtained using PSCAD/EMTDC software for different conditions, such as different fault resistances, fault locations, static VAR compensator locations, and source impedances. The proposed scheme is found robust and accurate for all the cases considered. The performance of the proposed scheme is superior to the recently proposed similar type of scheme and is unaffected from capacitive coupled voltage transformer and current transformer measurement errors and synchronization error.

The Application of Rogowski Coil in Power System

The traditional current transformer measurement device cannot meet the requirements of the rapid development in the current power system because of the outdated structure while the Rogowski coil has significant advantages. This article introduces some applications of Rogowski coil in power system. Now the research and application of Rogowski coil current transformer has become one of the most important research directions. Rogowski coil today has been widely used in electric power system.

A cryogenic sensing element for measurement current transformers

The design of a cryogenic sensing element for superconducting DC current transformers working up to 100 kA at 4.2 K is proposed. Limitations of μ-metal magnetic characteristics at cryogenic conditions are overcome by a soft Ni 81-Mo 5-Fe magnetic alloy (referred to as cryogenic permalloy). An optimized geometrical design allows cores saturation due to mechanical constraints to be avoided. The effectiveness of the design is demonstrated through electromagnetic simulations exploiting measurement results from the characterization of cryogenic permalloy samples. Moreover, a preliminary lab-scale cryogenic DCCT prototype for a nominal current of 20 kA is implemented and characterized. A typical precision of the transducer below ±0.05% is achieved along with nonlinearity better than ±0.05%.

Correction of saturated current from measurement current transformer

The suggested study presents an easy and effective way to compensate for the distorted secondary current of measurement-type current transformers (CTs). The suggested compensating algorithm is based on estimating the magnetising current from a Frohlich hysteresis approach. The efficiency of the proposed technique was first proved using computer simulations. The prototype compensating device was then tested in a laboratory environment using a 5/1A, 10VA, C0,5 measurement-type CT. The proposed compensation algorithm is dependent on CT burden and X/R ratio of the line where CT is connected. The outcomes of the study demonstrate that the technique is able to reconstruct the secondary current with an acceptable error and can be applied to any measurement-type CT regardless of its size and winding topology.

Development of a compensation algorithm for a measurement current transformer

An exciting current resulted from the hysteresis characteristics of the core causes an error of a measurement current transformer (CT). To produce the high accuracy measurement CT, it is designed to minimise the exciting current. This requires a large cross-section of the core and the high permeability core. If the exciting current can be estimated exactly and compensated, the accuracy of the measurement CT can be improved significantly. This study describes the development of a compensation algorithm for a measurement CT. The proposed compensation algorithm decomposes the exciting current into the core-loss current and the magnetising current. The algorithm uses not the hysteresis curve but the flux-magnetising current curve to minimise the number of required curves for interpolation. The exciting current at every sampling interval is obtained by summing the core-loss current and the magnetising current and then added to the measured secondary current to obtain the correct primary current. The test results using Electromagnetic Transients Program (EMTP)-generated data indicate that the proposed algorithm can improve the accuracy of the measurement CT significantly even with a couple of the curves. The experimental test results indicate that the compensator can improve the accuracy of the CT significantly from 2.5 to 0.1%.

Final report on supplementary comparison EURAMET.EM-S19 (EURAMET project no 688): Bilateral comparison of measurements of current transformers (CTs) between BIM and UME

This report presents the results of a bilateral comparison on current transformer measurements between BIM (Bulgarian Institute of Metrology) and UME (TÜBÍTAK Ulusal Metroloji Enstitüsü/NMI of Turkey). The current ratios between 5 A/5 A and 1000 A/5 A were measured at a frequency of 50 Hz with a burden of 5 VA at unity power factor and with different percentage of rated current.The main objective of the comparison was to demonstrate equivalence of metrological practice and to check the correctness of the calibration results. The results of the measurements showed a good agreement between BIM and UME both for the ratio errors and for phase displacements.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by EURAMET, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Detection and Correction of Saturated Current Transformer Measurements Using Decaying DC Components

When fault currents contain decaying dc components, current transformers (CTs) face the risk of becoming saturated. Traditionally, fault current waveform or CT model analyses were used to detect CT saturation. This paper analyzes the decaying dc components in fault currents to detect CT saturation. The decaying dc component in fault currents is first estimated using phasor-based computations. Such a component is then used to define a detection index. The proposed detection index can be easily used to detect CT saturation because its value in an unsaturated period is within a pre-known range. After CT saturation has been detected, the current samples and phasors in the latest unsaturated period are used to correct the saturated current samples. The proposed algorithm was tested using MATLAB/SIMULINK simulator and realized on a DSP Starter Kit to demonstrate its effectiveness and applicability.

A Simple Method for the Calibration of Traditional and Electronic Measurement Current and Voltage Transformers

The calibration of measurement transformers represents a classical task in the practice of electrical measurements. Most commercial instruments that are expressly designed for this purpose found their working principle on a scheme that is based on the idea of Kusters and Moore. Although they can assure very high accuracy, the need to employ a high-performance electromagnetic circuit makes them very expensive and usually not suitable for measurements at frequencies that are higher than 50 or 60 Hz. For this reason, these kinds of instruments cannot be employed for the calibration of the new generation of current and voltage transducers, such as electronic measurement transformers, whose employment is growing in all the applications where wide bandwidth is required. In this paper, a new method for the calibration of electromagnetic voltage and current measurement transformers (VTs and CTs) and electronic voltage and current measurement transformers (EVTs and ECTs) is discussed, and a deep metrological characterization is carried out. The novelty of the proposed method is represented by a completely different approach to the measurement of the ratio and phase errors of the measurement transformers. The method is based on the proper digital signal processing of the signals that are collected at the secondaries of the transformer under test and of a reference transformer when the same signal is applied to their primary. Since no auxiliary electromagnetic circuits are required, this solution can be easily implemented in a simple and cost-effective way. In spite of its simplicity, the tests that are developed on a prototype clearly point out that the proposed system is suitable for the calibration of measurement transformers with precision class up to 0.1 in the frequency range from 50 Hz to 1 kHz.

Final report EUROMET.EM-S11 on EUROMET Projects 473 and 612: Comparison of the measurement of current transformers (CTs)

The Euromet comparison entitled 'Comparison of the measurement of current transformers' was carried out over two projects with NPL as pilot laboratory and thirteen other participating European National Measurement Institutes (NMI). Current transformer measurements made by the participating NMIs support a large number of measurements made in the electrical generation, supply and distribution industries in their own countries. They also support many transformer manufacturers who rely on national standards as a source of traceability. The current (ratio) errors and phase displacement of each ratio of the uncompensated current transformer transfer standard were determined at a defined frequency, burden and power factor, using each participant's standard measuring method and equipment.The results supplied by each participant generally show good agreement but with a few exceptions over the whole range of measured values. Deviations from the comparison reference value were mostly within the quoted uncertainties, but again with a few exceptions. A summary of outlying results compared to laboratories' declared Calibration and Measurement Capabilities (CMC) is given in the conclusion. In several cases participants have been making current transformer measurements with new measurement systems and techniques, and in one case for the first time; therefore a large amount of experience in the measurement and interpretation of results has been obtained from this comparison.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by EURAMET, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Metodologias para avaliação e diagnóstico do estado de isolamentos de papel impregnado com óleo mineral

O isolamento elétrico mais comumente utilizado em subestações de média, alta ou extra alta tensão é o de celulose impregnada com óleo mineral isolante, em função de sua eficácia e custo reduzido. Sua utilização abrange transformadores de potência e suas buchas, reatores e transformadores de medição de corrente e tensão. Este artigo discute as metodologias tradicionais utilizadas na análise de estado e no diagnóstico do isolamento a partir do fator de dissipação e da concentração de gases dissolvidos no óleo, considerando os principais fatores que afetam estes valores. São também abordados alguns aspectos que causam incerteza na medição e nas metodologias de análise. É apresentada a modelagem de uma rede neural artificial para diagnóstico e identificação de estado do isolamento a partir de dados de concentração de gases dissolvidos no óleo, sendo os resultados obtidos comparados com os das metodologias tradicionais baseadas em normas.