Study of current measurement method based on circular magnetic field sensing array

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. Classic core-based instrument transformers are more prone to magnetic saturation. This affects the measurement accuracy of such transformers and limits their applications in measuring large direct current (DC). Moreover, protection and control systems may exhibit malfunctions due to such measurement errors. This paper presents a more accurate method for current measurement based on a circular magnetic field sensing array. The proposed measurement approach utilizes multiple hall sensors that are evenly distributed on a circle. The average value of all hall sensors is regarded as the final measurement. The calculation model is established in the case of magnetic field interference of the parallel wire, and the simulation results show that the error decreases significantly when the number of hall sensors n is greater than 8. The measurement error is less than 0.06% when the wire spacing is greater than 2.5 times the radius of the sensor array. A simulation study on the off-center primary conductor is conducted, and a kind of hall sensor compensation method is adopted to improve the accuracy. The simulation and test results indicate that the measurement error of the system is less than 0.1%

Determination of the speed of a microprocessor relay protection device of open architecture with a reed switch and the industrial internet of things

The paper presents the development of a microprocessor-based relay protection device on open architecture. Currently, there is a problem with modern microprocessor relay protection: the impossibility to replace the damaged element with alternatives from other manufacturers. The solution to this problem is the use of devices with open architecture. The study developed a structural model of a microprocessor-based relay protection device based on an open architecture with the industrial Internet of things application. Open architecture is achieved through open protocols and the principle of modularity. The industrial Internet of things technology transfers the control action of triggering blocking. A microprocessor-based relay protection device prototype based on an open architecture was developed. The simulation of the developed device was conducted. The appearance of higher harmonics and aperiodic components in the short-circuit current was not considered during modeling. Due to the study's limitations in the form of lack of load, current and voltage sensors, such as Hall sensors, and inductance coils, the subject of this study is only the speed of operation. A high multiplicity current generation setup was assembled for experimental testing. The developed relay protection device on an open architecture trips faster than the traditional solution. The application of the Internet of Things allowed it to ensure the blocking of non-selective tripping. The obtained results are provided by structural simplification compared to traditional solutions and speed of information transfer with the application of the Internet of things. The developed open architecture device with the industrial Internet of things technology application gives new possibilities for relay protection systems, including flexibility to meet the requirements in connection with the introduction of distributed powe