Non-contact Current Measurement Research Articles

Non-Contact Current Measurement for Three-Phase Rectangular Busbars Using TMR Sensors.

This paper proposes a non-contact current measurement method for three-phase rectangular busbars based on TMR (tunneling magneto-resistance) sensors, due to their advantages of large dynamic range, wide bandwidth, light weight, and easy installation. A non-contact current sensor composed of only three TMR sensors is developed and the TMR sensors are respectively placed at a location with a certain distance from the surface of each rectangular busbar to measure the magnetic fields generated by the busbar currents. To calibrate the developed current sensor, i.e., to establish the relationship between the magnetic fields measured by the TMR sensors and the currents flowing in the three-phase rectangular busbars, we designed a thyristor-controlled resistive load as a calibrator, which is connected to a downstream branch of the distribution cabinet. By switching the resistive load, a calibration current, which can be identified from the background current, is generated in one rectangular busbar and its value is measured at the location of the calibrator, and transmitted wirelessly to the location of the TMR sensors. A new and robust method is proposed to extract the voltage components, corresponding to the calibration current, from the voltage waveforms of the TMR sensors. By calculating the proportional coefficients between the calibration currents and the extracted voltage components, online calibration of the current sensor is achieved. We designed and implemented a current measurement system consisting of a current sensor using TMR sensors, a thyristor-controlled resistive load for current sensor calibration, and a data acquisition circuit based on a multi-channel analog-to-digital converter (ADC). Current measurement experiments were performed in a practical distribution cabinet installed in our laboratory. Compared to the measurement results using a commercial current probe with an accuracy of 1%, the relative error of the measured currents in RMS is less than 2.5% and the phase error is less than 1°, while the nonlinearity error of the current sensor is better than 0.8%.

Adaptive positioning current measurement method for multi-conductor system based on linear magnetic sensor array

As transmission and distribution networks now span a wider region, the difficulty of monitoring lines and the incidence of faults are both increased, which reduces the stability of the power system. During the troubleshooting procedure, quick problem identification, line selection, and placement are essential, and non-contact current measurement can be quite helpful. Its advantages include the capacity to monitor high-frequency current and line space position, both of which contain a range of fault characteristics, as well as a high-frequency band, compact size, low cost, and simple installation. In this paper, we present an adaptive positioning current measurement method for multi-conductor systems based on a linear magnetic sensor array. The method detects the position shifts of individual conductors when their locations are displaced to varying degrees using a novel conductor positioning calculation algorithm. Besides, it automatically adjusts the measurement matrix to provide precise current measurements. In the simulations, three-phase parallel currents with an amplitude of 100 A are analyzed based on the parameters of a 15-meter cup-type tensile tower. During the different displacements of the three conductors, the new method calculates the conductor displacements and the current in real-time. For all the three conductor positions change with the maximum amplitude of 2 m, the average error of all the conductor position measurements is about 0.1 m, and the root mean square error (RMSE) of the currents drops from 34.18A to 3.72A with correction, which proves the effectiveness of the algorithm.

Research and Demonstration of Intelligent Multi-Physical Quantity Integration Sensor for Transmission Lines

The digital grid requires sensors to be widely deployed, safe, and reliable. At present, the single functional sensors suffered from redundant sensing system, repeated construction and low utilization rate. Therefore, this paper researched the multi-physical quantity integration sensor for a quad-bundle spacer on 500kV transmission lines. The sensor was composed of self-supplying rings and the monitoring host. Based on the non-contact current measurement technology, energy supply technology, intelligent sensing technology, low power consumption technology, reliability design technology, and other advanced technologies, this paper designed the hardware, software, and protective structure of the sensor, which can monitor the current and temperature of bubbles, channel side image and infrared image on transmission lines, ambient temperature, humidity, and air pressure. Finally, the multi-physical quantity integration sensors have been used on transmission lines in China Southern Power Grid, and the functions were verified. The sensors promote the automation, information, and digitization of monitoring transmission lines.

Measurement of high frequency magnetic properties of electrical steel sheet using prototype Rogowski coil

In order to develop a high-efficiency, low-loss, small, high-power, high-speed rotating motor, it is necessary to accurately measure the magnetic properties of electrical steel sheets under PWM excitation. A shunt resistor is generally used for measuring magnetic characteristics, but non-contact current measurement is required. However, iron cores are used in commercially available current measurement sensors, and it is necessary to consider the effects of core characteristics on high-frequency currents. The authors are focusing on Rogowski coils and developing small current / magnetic field sensors specialized for motor and electrical steel sheet evaluation. In this paper, we make a prototype of Rogowski coil, and report on the evaluation of basic electrical characteristics and the results of application to the measurement of magnetic characteristics of electrical steel sheets under sinusoidal excitation and PWM excitation.

Quasi-Static Current Measurement with Field-Modulated Spin-Valve GMR Sensors.

A non-contact current measurement device comprised of a GMR sensor and a ferrite ring core was investigated. The sensor chip employed a high-sensitivity spin-valve full-bridge GMR sensor of which the direct output has non-negligible hysteresis and a limited linear range. By applying an AC modulation current to modulate the output of the GMR sensor, the hysteresis was reduced, and the linear range was over ±0.5 A. The resolution for DC and quasi-static current measurement was 0.1 mA at a 10 Hz bandwidth. The output in proportion to the measured current was obtained either by demodulating the current-sensitive AC signal or by employing the filtered output of the intrinsically nonlinear spin-valve response. The proposed current sensing scheme is suitable for quasi-static current measurement from DC to over 100 Hz.

Interference‐rejecting current measurement method with tunnel magnetoresistive magnetic sensor array

Innovative methods for wide range measurement of electric current remains an active research problem in modern power systems. Conventional methods based on magnetic field readouts have realized non-contact current measurement by interpreting magnetic flux density into electric current, such as Hall effect and Rogowski Coil arrangement. TMR magnetic sensor has spread its application for current measurement due to its miniaturization, low cost, high response frequency and high sensitivity. However, due to the superposition of unwanted magnetic field, the magnetic fieldunder measurement is strongly affected. In this paper, a four-sensor array design is proposed to solve this problem. Transcendental equations, which can not only calculate the current under measurement but also the interference current at random places, are constructed. Numerical simulations, finite element analysis (FEA) of the field and laboratory experiments were performed to verify the proposed method. It is shown that when targeted current is 100 A and interference is 820 A, the largest simulated error is 3.92 × 10−10; when targeted current is 100 A and interference is 1000 A, error with FEA is 2.3796%, when targeted current and interference are both 500 A, experimental error is 4.14%. This verifies the effectiveness of the proposed method.

Research on Non-Contact Weak Current Detection Technology

With the continuous development of industrial technology, the weak current plays an increasingly important role in all fields of life. In order to facilitate the user to carry, the study of contactless weak current measurement technology is also emerging. This article’s design idea is based on two-dimensional reluctance sensor device built non-contact weak current detection system. The system uses the reluctance sensor HMC1002 to collect the current signal and the temperature sensor DS18B20 to compensate the temperature. The signals collected by the reluctance sensor and the temperature sensor are extremely weak. After being amplified by the amplifying circuit, the signal is conducive to subsequent detection and processing. Filter circuit can filter out interference signals to achieve the goal of improving accuracy. After the corresponding algorithm of the microcontroller will convert the signal voltage, easy to read and store, thus designing a non-contact current measurement capable of detecting weak currents and achieving higher accuracy.

磁気センサによる非接触高精度電流検出技術

磁気センサによる非接触高精度電流検出技術

Non-contact Current Measurement in Power Transmission Lines

This project deals with the technique of measurement of current in power transmission lines without the need for actual contact with the wires. Magnetic fields emitted by the wires are sensed using ...

521 電磁現象を利用した微細金属配線の非接触電流測定(材料力学III)

521 電磁現象を利用した微細金属配線の非接触電流測定(材料力学III)

Non-contact current measurement with cobalt-coated microcantilevers

A magnetic field detection system that uses a cobalt-coated microcantilever as the detector element is demonstrated. Three different microcantilever geometries are investigated. This research also demonstrates a novel microcantilever readout technique using a dual fiber optical readout. The cantilever sensors are shown to detect changes in current as small as 0.1 A and the ability to measures current up to 5 mm from the sensor.

Non-contact Current Measurement in Small Electric Parts by Using a Non-contact Thermometer

This paper describes a non-contact current measurement in small electric parts by using a non-contact thermometer. When the small electric parts are used in a small machine or device, it is difficult for a conventional current sensor to measure current in the small electric parts. Assuming that the temperature rise of the parts is proportional to the power consumption, the temperature rise and the resistance of the parts are used to obtain the current through the electric parts. In our experiment, the relationship between the current, temperature rise and power consumption is clarified. The power consumption is proportional to the temperature rise and the current is in proportion to the square root of the temperature rise. The method how to measure the current without contact is explained.

Non-contact current measurement system using SQUID

We have developed a non-contact current measurement system, which converts magnetic flux distribution measured with high sensitivity using DC-SQUID into current distribution. The DC-SQUID is composed of Nb/AlO x /Nb junctions with high thermal reliability, and a pickup coil. The diameter of the pickup coil and the standoff distance between the DC-SQUID and samples, which are important parameters for the spatial resolution, are respectively 200 and 500 μm . The spatial resolution is 200 μm and the current noise density calculated from the magnetic noise is 6.8 nA/ Hz . We have applied the system to a solar cell to visualize the area, which does not generate electrical power.