Low Power Contactless Voltage Sensor for Low Voltage Power Systems

• Published in: Sensors (Basel, Switzerland) Vol. 19; no. 16; p. 3513
• Main Authors: Delle Femine, Antonio, Gallo, Daniele, Landi, Carmine, Lo Schiavo, Alessandro, Luiso, Mario
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 11.08.2019; MDPI
• Subjects: Accuracy; Analog circuits; Circuit design; contactless; Electrical measurement; Electricity distribution; Electrodes; Harmonic distortion; Internet of Things; Line voltage; low power; Low voltage; non-sinusoidal conditions; Operational amplifiers; Power cables; Power lines; Power supply; power system measurements; sensor; Sensors; Sine waves; voltage measurement; Italy; power system measurements; low power; sensor; contactless; non-sinusoidal conditions; voltage measurement
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s19163513

Contactless measurements represent the desirable solution in many contexts, where minimal cabling is required or, in general, cabling is not possible. This paper presents a new contactless voltage sensor for low voltage power systems. It is based on a contactless capacitive probe, which surrounds the power cable. It has two concentric electrodes insulated by a shield. A low power analog conditioning circuit evaluates the power line voltage by measuring the current in one of the capacitances of the probe. All the single stages of the circuit have been designed by using low-power rail-to-rail operational amplifiers, supplied at 3.3 V, in order to minimize the power absorption. The sensor has been characterized in various conditions, with sine waves and distorted signals, varying the frequency and the harmonic distortion. The influence of the current, flowing into the power cable, on the voltage measurement has been evaluated too. It shows a good accuracy (lower than 0.3%) from 100 V to 300 V, with a power consumption less than 5 mW.