Influence of External Current on Yokeless Electric Current Transducers

Abstract

Yokeless electric current transducers have compact size, but they are sensitive to external magnetic fields, including those caused by electric currents in their vicinity. It is often believed that this unwanted sensitivity can be effectively suppressed by using a differential sensor. In this paper, we investigate the effect of external current with arbitrary position on busbar differential current sensor. We show the main disadvantage of the differential current sensor: increased sensitivity to currents in the transversal direction, which are not sensed by a single sensor. We analyze by finite element method simulation also the influence of real conductor size and uneven density of ac currents. The results were verified on 1000 A current transducer using a pair of microfluxgate sensors. The realistic suppression of close currents depends on the conductor angular position and in 10 cm distance it can be as low as 50, but it can be corrected if the geometry is known.

Circular Array of Magnetic Sensors for Current Measurement: Analysis for Error Caused by Position of Conductor

“…For that reason, the combination of the relative error, ε dβ , caused by un-centeredness and un-perpendicularity become more necessary to consider together. In Figure 4, ε dβ is calculated by Equation (11) with N = 8, r 0 = 40 mm; it can be seen that the relative errors are retained within 0.5% of the major region of d and β. With the approximate region of −10 mm< d <10 mm and −30 • < β < 30 • , the relative errors stay within 0.077%, and increase rapidly as the absolute value of d and β both increase.…”

Contactless measurement of electric current using magnetic sensors

“…The realization and the optimization of gradiometric current transducers based on Hall effect sensors are described in [15] and [16]. The influence of the external current on the gradiometric busbar sensor is analyzed in [78]. Complete suppression of external fields and gradients requires more sensors [79].…”

“…For this type of gradiometric sensor, there is also limited rejection of the signal from external currents: current at a distance of 14 cm is suppressed only by a factor of 66 [78]. This can be improved to 1300 by using a larger number of sensors [79].…”

Three-Phase Busbar Current Transducer

“…T he theoretical framework for the analytical model is developed. T he Ampere's law is used for analytical calculation of the parasitic response to the external current [Ripka 2017]. For the differential configuration with the spacing of 2s, the parasitic response to the idealized external current I in the distance v in the same plane is…”