Measured Phase Currents Research Articles

Line to Ground Fault Detector in 400 KV Transmission Line by Using Intelligent System

The ability to locate and identify problems in power transmission lines is the most crucial component of power system engineering since it ensures the stable and efficient operation of electrical grids. to minimize downtime, prevent cascading failures, and maintain the power system's stability. problem localization helps identify the precise location of the problem and speeds up the process of restoring the power supply while minimizing the impact on consumers. This paper presents a measurement-based automatic fault localization and detection (ANFIS) technique for transmission lines. High-speed processing of real-time error localization and detection is made possible by the design and implementation of ANFIS. It is suggested that ANFIS for digital distance protection systems be able to discover issues in addition to detecting them. When a transmission experiences a three-phase malfunction Thus, the suggested method can precisely pinpoint the impacted stages. ANFIS has been trained and tested using many kinds of field data. The field data are collected by simulating faults in the Simulink Matlab model depicting the transmission line at various sites between Misan – Kut station 400 Kv along 200 Km using computer software based on Matlab. Phase current and voltage measurements are utilized as ANFIS inputs and are available at the busses. Regarding the kind and detection of defects, The output will demonstrate fault and location identification with an extremely low error percentage through simulated processes; the results also demonstrate that the approach's selectivity and speed are quite dependable and provide adequate performance for applications involving transmission and distribution monitoring; and security. The study emphasizes the criticality of promptly and precisely locating faults in power transmission lines to preserve the stability and security of the power system.

Diagnosis and classification of disturbances in the power distribution network by phasor measurement unit based on fuzzy intelligent system

AbstractThe dynamic nature of distribution networks raises fresh issues with how such electrical systems function. These networks have some characteristics that indicate the need for better monitoring and control capabilities, including dispersed generation employing renewable resources, changing load profiles, and rising reliability requirements. Phasor measurement units (PMUs) offer simultaneous voltage and current phasor measurements at various places and offer a variety of options for gauging the condition and health of the power distribution network. In this regard, a cost‐optimized PMU with some unique features for distribution systems is presented in this work. These features include a fuzzy inference system to determine the root cause of potential electrical disturbances and methods to estimate electrical parameters through measured field data, which are necessities. This study takes into account the modelling of PMUs, utilizing a process for fault detection and classification with a fuzzy inference network. The 9‐bus distribution network's dependability model is built once the components and their functions are first outlined. The proposed model is then used to calculate the availability of the presented model, which has been examined to provide an analogous reliability model for PMUs. Depending on the specific manufacturer, the PMU's design and specs will change. To extract phase and size measurement features for the proposed model adaptive neural‐fuzzy inference system network's training, two PMU structures and associated reliability models are described here. When merging input data for fuzzy neural network prediction using MATLAB software, fuzzy sets are taken into account for error classification analysis.

Implementation and laboratory verification of method utilizing phase and neutral quantities for detection and location of low‐current earth faults in resonant grounded networks

AbstractEarth faults is a challenging fault type to locate in resonant grounded networks due to their naturally low fault current, and the problem increases with an increased fault impedance. This paper describes the detailed implementation and laboratory testing of a method for detection, location and clearing of earth faults with very small fault currents. The method consists of two indicators used in the fault detection stage, where their simultaneous operation ensures selective fault detection and faulty feeder selection. One of these indicators also enables continuous fault indication throughout a sectionalizing process. The laboratory tests demonstrate that both indicators function as intended, and it is the current sensors which ultimately limit the attainable sensitivity. Faults up to 15 kΩ were detected successfully in the laboratory network based on phase current measurements, while the sectionalizing indicator showed much higher sensitivity and functioned as intended in a 50 kΩ fault. Measurements from one field test in a 22 kV network corroborate the laboratory results and demonstrate the expected earth fault indicator response.

Simultaneous Identification of Inverter and Machine Nonlinearities for Self-Commissioning of Electrical Synchronous Machine Drives

The proposed identification method allows for a simultaneous estimation of nonlinear output voltage deviations in voltage source inverters (VSIs) and nonlinear synchronous machine models. Based on the identified characteristics with the help of physically inspired structured artificial neural networks (ANNs), an efficient tuning of the current control system can be performed and the nonlinear voltage deviations caused by parasitic effects and dead-time distortions can be accurately compensated for. The identification is performed without position sensor while the rotor is mechanically locked by utilising measured phase currents and reference machine voltages only. Experiments for an interior permanent magnet synchronous machine (IPMSM) and a reluctance synchronous machine (RSM) show that the proposed method is capable of identifying the current dependent self-axis and cross-axis flux linkages, differential inductances and the nonlinear VSI voltage deviations as well as the phase resistance at the same time. The proposed method is fast and generic. Besides the rated machine current, voltage and frequency, no prior system knowledge is required making it applicable for the self-commissioning of any electrical synchronous machine drive.

Microgrid Differential Protection Based on Superimposed Current Angle Employing Synchrophasors

The inclusion of multi-energy distributed generators (DGs), especially inverter-interfaced generators, presents challenges in the microgrid's protection strategy and operational constraints. The work for designing primary protection mechanism for microgrid is continuously progressing. In this regard, this article presents a positive sequence superimposed current differential angle (SCDA) based protection scheme employing only positive sequence current phasor from both ends of the line. The proposed scheme collects current phasor measurements from the low-cost micro-phasor measurement units ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> PMUs). The performance of the proposed scheme is analyzed through simulations on a 7-node microgrid in grid-connected and isolated mode operation under various fault and no-fault situations, and also considering the effect of DG penetration level and DGs types. The simulations are also carried out in the IEEE-33 node network considering C37.118.1 standards-compliant PMUs. Furthermore, a real-time control hardware-in-loop (RTC-HIL) testing is performed to further validate the scheme for practical implementation.

Fundamental PWM Excitation Based Rotor Position Estimation for a Dual Three-Phase Permanent Magnet Synchronous Machine

Two rotor position estimation methods for a dual three-phase (DTP) permanent magnet synchronous machine (PMSM) are investigated in this article, where the rotor position is estimated by exploiting the saliency of the motor through the phase current derivative measurement during the fundamental PWM excitation of a standard six-phase two-level inverter. It is found that in a DTP PMSM, the wide speed range rotor position estimation is possible not only in the torque-producing subspace, but also in the harmonic subspace. The principle and practical implementation of the methods are explained in details. The experimental results verify the effectiveness of the proposed rotor position estimation methods.

Incremental Phase-Current Based Fault Passage Indication for Earth Faults in Resonant Earthed Networks

We propose a method for the fault passage indication of earth faults in resonant-earthed networks, based on phase current measurements alone. This is particularly relevant for electricity distribution systems at medium-voltage levels. The method is based on the relative magnitudes of the phasor changes in the phase currents due to the fault. It is tested for various network types and operation configurations by simulating the network in pscad and using the simulated currents as the input for an implementation of the method in matlab. In over-compensated networks, the method shows reliable detection of the fault passage, with good selectivity and sensitivity for both homogeneous and mixed (cable and overhead line) feeders. However, for the less common under-compensated systems, it has limitations that are described further in this study. The method has good potential for being cost effective since it requires only current measurements, from a single location, at a moderate sampling rate.

Non-Contact Measurement Method of Phase Current Based on Magnetic Field Decoupling Calculation for Three-Phase Four-Core Cable

As one of the important parameters characterizing the cable’s operation status, an accurate measurement of the current is particularly important for the cable’s reliable operation and status monitoring. Aiming at the problem that the sum of the current phasors of multiphase cables is 0 when running in a steady state, and that the traditional mutual inductance current measurement method cannot be used for the phase current measurement of such cables, or that the insulation layer needs to be damaged, this paper proposes a non-contact measurement method of three-phase cable current, based on the magnetic field decoupling calculation. When combined with the actual parameters of the three-phase cable, the analytical calculation model of the magnetic field distribution of the three-phase cable is established. The relationship between the output ratio of the sensor and the deflection angle is obtained through theoretical derivation, the magnetic field coupling coefficient matrix is determined, and the transfer relationship between the output of the magnetic sensor and the current of each phase is clarified; an array magnetic field sensor is designed, which can sense the information of the adjacent magnetic field independently and is used for the reconstruction of three-phase currents. The effectiveness of the proposed method was tested on the built three-phase four-core cable current measurement test platform. The experimental results show that under the three-phase current balance, the measurement error of phase A, phase B and phase C is less than 2.8%, and the waveform and phase angle of the three-phase current can be well restored, which verifies the three-phase current measurement method proposed in this paper.

Data-Driven Time-Varying Inertia Estimation of Inverter-Based Resources

This letter proposes a data-driven inertia estimator for inverter-based resources (IBRs) with grid-forming control. It is able to track both constant and time-varying inertia. By utilizing the Thevenin equivalent, the virtual frequency inside IBRs is first estimated with only its terminal voltage and current phasor measurements. The virtual frequency and the measurements are then used together to derive the state-space swing equation model. Then, an enhanced adaptive Unscented Kalman filter (EAUKF) is developed to estimate IBR inertia. Numerical results on the modified IEEE 39-bus power system demonstrate that the proposed inertia estimator remarkably outperforms the existing state-of-art methods both in tracking speed and accuracy.

Low-Cost Realization of Feature Position Estimation Scheme for Switched Reluctance Motor

This letter proposes a low-cost feature position estimation scheme for singly excited SRM without using lookup tables. This scheme uses the particular flux linkage versus current curve, corresponding to the commutation angle, to generate a flux-linkage reference. Phase commutation is executed at the instant when the online estimated flux linkage reaches this reference threshold. So, this letter, initially, proposes a novel analytical method to compute the reference flux linkage from phase currents. Then, a new approach is presented that maps the individual measured phase currents and estimated flux linkages into corresponding unified signals to reduce the computational burden. Thereafter, the mutual coupling among phases is shown as a cause of serious error in the thresholding operation, and a design criterion to avoid this error is derived. Performance of the proposed sensorless scheme is experimentally validated on a 1 kW, 3000 r/min, 6/4 SRM-based laboratory prototype.

Phase Current Measurement Method for Switched Reluctance Motors With One Current Sensor

Accurate phase currents are necessary for the control and protection of motor drives. In this article, a novel phase current reconstruction strategy for switched reluctance motors (SRMs) with single current sensor is proposed. Firstly, the characteristic of the unsaturated phase inductance is analyzed. Secondly, the location of the single current sensor is rearranged, and all phase currents flow through the sensor in positive direction. The phase current in unsaturated region is directly obtained by dividing the flux linkage by the unsaturated inductance. In the linear region, the phase current is calculated by solving the similar triangles according to the relationship between the unsaturated inductance and saturated inductance. Finally, the overall control strategies of SRM drive integrated with the proposed phase current reconstruction method are implemented. The proposed method can be used for different chopping modes and different control strategies. Simulations and experiments on a three-phase 12/8 SRM validate the effectiveness of the proposed phase current reconstruction scheme.

An Integrated Driving/Charging Four-Phase Switched Reluctance Motor Drive With Reduced Current Sensors for Electric Vehicle Application

This article proposes an integrated power converter (IPC) with driving/charging capabilities for four-phase switched reluctance motor (SRM) drive-based electric vehicle (EV) application. With the proposed IPC, only two current sensors are employed for measuring phase currents under all operating conditions. The proposed IPC integrates three circuits. First, during the SRM driving mode, the proposed IPC is utilized as an improved Miller converter. Second, during battery charging mode, the proposed IPC is utilized as an on-board battery charger, which is based on a bridgeless boost power factor correction circuit (PFCC) that incorporates two dc–dc boost converters. The on-board battery charger is realized by utilizing the existing power electronic switches in the proposed IPC and all the phase windings as charging inductors. Third, a front-end bidirectional dc–dc converter is employed for maintaining voltage and current balance between IPC dc-bus and battery. During driving mode, the front-end converter boosts the battery voltage to the IPC dc bus voltage. And during regeneration/braking, the stored magnetic energy is used to charge the battery in constant-current (CC) mode via the front-end converter. During battery charging via ac grid, the bridgeless boost PFCC and the front-end converter operating in buck mode charge the battery in CC/constant-voltage (CV) modes without stepping down the ac grid voltage. The claims of the proposed IPC are validated through simulation and experimental verifications.

차단 주파수 가변형 HPF를 이용한 듀얼 3상 인버터의 스위치 개방 고장 검출 기법

This paper proposes a technique for detecting individual open fault on the top and bottom of a dual three-phase inverter. In general, the switching devices have a high failure rate in the dual three-phase inverter. Especially, the switching devices may fail due to high switching frequency and thermal, electrical, and mechanical stress. As a result, the proposed method normalizes the measured phase currents and detects failures through integrators and HPF with variable cut-off frequency. Therefore, the proposed algorithm can stably detect fault even in the steady state and transient state where the rotor speed is changed. The effectiveness and usefulness of the proposed method are verified through several experiments.

3-레그형 2상 인버터에서의 전류 복원 영역 확장

For measuring phase currents of two-phase motors driven by the three-leg inverters, the leg shunt resistors inserted between the lower switch of each inverter leg and the negative DC rail can be used instead of the expensive Hall-effect sensors. The two-leg shunt method using shunt resistors located on the two-phase legs has a limited current measurement range. In addition to this method, the three-leg shunt method can reconstruct the immeasurable phase currents by using an additional shunt resistor on a neutral leg. Therefore, the current measurement range can be wider than that in the two-leg shunt method. However, this method cannot properly reconstruct the currents in the specific areas where the voltage modulation index of the inverter is high, thereby decreasing the DC voltage utilization rate, and increasing the torque ripple of the motors. To improve this problem, this paper analyzed the current reconstruction areas of a three-leg type two-phase inverter applied CPWM(Continuous Pulse Width Modulation) method, and proposed a simple technique to expand the areas. The proposed technique can expand the current reconstruction areas by securing the turn-on time of the inverter lower switches utilizing the DPWM(Discontinuous PWM) method, which results in the improvement of DC voltage utilization rate.

A Coreless Current Probe for Multicore Cables

To measure the current on each conductor in a three-phase three-core cable or a three-phase four-core cable without an armor or the armor that is made of nonmagnetic material, one has to remove its sheath/armor and applies a traditional device, such as a current transformer (CT) to each conductor, which is invasive and inconvenient. In this article, a Coreless current probe, composed of a tunnel-magnetoresistance (TMR)-based magnetic sensor array, is presented to nondestructively achieve current measurement for multicore cables. The conductor positions, incline angles, and current phasors of a multicore cable are simultaneously identified by solving a nonlinear least square (NLLS) problem. The current waveforms are reconstructed in real time through a real-valued matrix multiplication using the measured time-domain TMR sensor voltage signals. Both simulation and experiment are performed to validate the feasibility of the proposed method. The simulation study is first conducted and demonstrates that a maximum relative current amplitude error of less than 5% and a maximum phase error of lower than 4° can be achieved, and three-phase current waveforms with many harmonics are also successfully reconstructed by simulation. A prototype Coreless current probe is designed and fabricated. The experimental study involving fundamental current phasor measurement and current waveform reconstruction is subsequently performed on a three-phase three-core cable. The experimental results indicate that the maximum relative current amplitude error and phase error, respectively, have average values of 5.44% and 2.58°. Meanwhile, three-phase current waveforms with many harmonics generated by three types of appliances are also successfully reconstructed.

Identification of AC Distribution Networks With Recursive Least Squares and Optimal Design of Experiment

The increasing penetration of intermittent distributed energy resources in power networks calls for novel planning and control methodologies which hinge on detailed knowledge of the grid. However, reliable information concerning the system topology and parameters may be missing or outdated for temporally varying electric distribution networks. This brief proposes an online learning procedure to estimate the network admittance matrix capturing topological information and line parameters. We start off by providing a recursive identification algorithm exploiting phasor measurements of voltages and currents. With the goal of accelerating convergence, we subsequently complement our base algorithm with a design-of-experiment procedure which maximizes the information content of data at each step by computing optimal voltage excitations. Our approach improves on existing techniques, and its effectiveness is substantiated by numerical studies on a modified IEEE testbed.

An Improved Noniterative Parameter-Free Fault Location Method on Untransposed Transmission Lines Using Multi-Section Models

This paper proposes an improved noniterative fault location method on untransposed transmission lines without utilizing line parameters. Two-end three phase voltage and current phasor measurements before and during the fault are typically required. First, the parameter-free fault location problem is formulated through multi-section transmission line models, and the necessary condition of noniterative solutions is carefully investigated to determine the maximum possible section number of the multi-section line model. Afterwards, with the determined section number, the analytical solution of the fault location is derived with full utilization of the inherent characteristics of the line parameter matrices. Instead of solving all the parameters, two key variables inside the parameter matrices are extracted and the fault location is obtained by analytically solving a polynomial equation. The method provides a closed-form analytical solution, and therefore avoids convergence issues of iterative algorithms. In addition, line asymmetry of untransposed transmission lines are fully considered to minimize fault location errors. Extensive numerical experiments show that the proposed method has improved fault location accuracy compared to the existing method, with different fault types, locations and impedances.

Normalized Dynamic Time Warping Distance Based Auxiliary Restraint Scheme for Restricted Earth Fault Protection of Converter Transformers

Converter transformers are one of the most important and costly equipment in High Voltage Direct Current (HVDC) transmission systems. They require sensitive and reliable protections. However, the maloperation of restricted earth fault (REF) protection of converter transformers caused by unloaded energization of converter transformers has been reported. Aiming at this problem, the saturation and measurement distortion of the current transformer on neutral line (CTN) and the resulting maloperation mechanism of REF protection are analyzed firstly. Then, an auxiliary restraint scheme of REF protection of converter transformers is proposed exploiting the similarity between the waveforms of the zero-sequence current on neutral line and the calculated zero-sequence current from measured phase currents under magnetizing inrush and fault conditions. The proposed auxiliary restraint scheme is based on normalized dynamic time warping distance (DTWD), which has strong robustness against CT saturation. The proposed auxiliary restraint scheme is verified by simulations and practical data recorded on-site.

PMU-Based State Estimation for Networks Containing LCC-HVDC Links

This letter proposes an equality-constrained weighted least squares (WLS) state estimation model for networks containing LCC-HVDC links. Voltage and current phasor measurements for the AC network are provided by phasor measurement units (PMUs) and DC voltage and current measurements for the DC transmission lines are acquired by appropriate DC sensors. AC&#x002F;DC coupling equations and zero injections are treated as equality constraints. Simulation results for a 6-bus hybrid AC&#x002F;DC network are shown to validate the proposed model and algorithm.

Modeling and Detection of Phase Current Sensor Gain Faults in PMSM Drives

The fault of current sensors in AC electric drives can cause inaccurate tracking of the control reference and torque oscillations, that can lead to damage of mechanical components. Therefore, the development of accurate detection techniques of these faults plays a crucial role for the proper management of the electric drive and for the fault isolation and estimation. In the paper, a model-based method for the detection of phase current sensor gain faults in a Permanent Magnet Synchronous Motor (PMSM) drive with Field Oriented Control (FOC) is proposed. At first, a mathematical model is presented, which allows an accurate determination of the analytical closed-form expression of the steady-state stator currents, taking into account the effects both of the current control regulators and of any current sensors gain faults. Starting from this model, a low-computation algorithm has been carried out, which allows not only to detect and isolate the current sensors affected by the gain fault, but also to estimate the gain values starting from the measured phase currents and motor speed. The model and the diagnostic algorithm performance is verified by means of numerical and experimental results.