Portable device for detecting electric fields in water

Abstract

In our electrically powered world, it is not uncommon for electrical alternating current (AC) supply cables or infrastructure to exist in, or close to water. In the event of faults, poor engineering practices or natural disasters, like floods, hazardous, AC voltage leakages can arise, which can be lethal to persons in the water, in close proximity to the fault. This study aims to prevent electrocution by implementing a device which can detect the presence of potentially-lethal water-borne electric fields. The dissertation presents the design and development of a PCB-based prototype, with the aim of preventing electrocution accidents in water. The proposed device is handheld, portable, and battery operated. It consists of discrete electronic components interfaced with a microcontroller, which performs the necessary processing, to detect alternating voltages and determine whether they are lethal in nature. When an AC supply, such as a faulty cable, is exposed to water, it causes water-borne electric fields. Placing two conductors a distance, d apart, perpendicular to the same electric field, a potential difference is observed across the two conductors. This project exploits this phenomenon to detect the presence of AC voltages in water, by detecting AC potential differences across two probes. The detected potential difference is interfaced to the Analogue to Digital Convertor (ADC) input of a microcontroller such that digital signal processing techniques are used to determine the value of the potential difference and display it on a bar-graph display. This study is mainly concerned with the design and implementation of the interface circuit, built using discrete components and the routines to be executed by the microcontroller. The selection of the best microcontroller and programming language to use is also discussed, leading to the selection of the ATMEGA328PB AVR microcontroller and the C programming language. This dissertation reports on 62 test cases, which show that the proposed device is capable of detecting AC voltages with an average accuracy of 99.13% of the actual voltage. This high level of accuracy confirms that the proposed device meets the functional requirement, is capable of detecting leaking alternating voltages in water, and can potentially save lives.