Current Sensing in LV Distribution Panels through the use of Magnetic Field Sensors

Abstract

In power systems currents that usually flow through flat copper or aluminium conductors called bus bars. Therefore, there is a practical demand for bus bars to be employed in current measurement applications. The present investigation, taking into account this practical demand, has as its objective the development of a cheap and automatic current monitoring system applicable to electrical bus bars. The requirement to develop a low cost system is the first step in order to obtain a possible future industrial production of this system and it affected the choice of the hardware tools used in this project. The bus bars taken into consideration in this project are employed in an electrical LV distribution panel intended for use in the industrial sector. The panel is employed for the supply of four different 3-phase circuits that provide energy to distinct groups of electrical loads. This automatic system of monitoring has the purpose of measuring the current flowing through every bar with the future goal to check, at any time, electrical information of the electrical system, such as the load curve that denotes every circuit. The application developed in this investigation assumes that the magnetic field around a bus bar, at a certain distance, is proportional to the applied current at all times. Thus, it is possible to find out the electrical information of a bus bar by measuring and analysing the emanated magnetic field. In order to analyse the Magnetic field, it has been taken into consideration, principally for the cost-effectiveness, the implementation of a number of Magnetoresistive sensors installed into the panel and supported by an Arduino® board, specially programmed for the case in study. The main develop of the project was realized using a 3D model of the distribution panel, designed with the support of the Solidworks® software and subsequently implemented in the COMSOL Multiphysics® simulation software for FEM analysis. The use of the FEM simulation software has been fundamental in order to find out the correct position and configuration of the sensors. The main goal obtained with the FEM simulations it was the elimination of the influence of stray MFs in the sensors measures through the setting of an anti-differential configuration of the sensors. At the end of the work it has been reached an advanced level of the project, with the correct functioning of the simulating measurement system and the implementation of an Arduino® algorithm to control the board supported the sensors. The correct functioning of the simulating system was figure out with a graphical study of the measured currents trends, developed in a Matlab® environment.