Development Of Non-Contact Voltage Measurement Device

In the field of electrical sensing and detection,voltage and current measurements are available in a variety of ways.Among them,the non-contact current measurement is realized using Rogowski coil and other devices by measuring the magnetic field around the line to be tested.In the whole measurement process the device does not need to touch the metal part of the line to be tested,and the measurement process is safe and convenient,and does not need to damage the Insulation of the line or find line terminals.Besides,there is no need to cut off the power and there are many other advantages.However,in the field of voltage measurement,especially at the 220/380 V voltage level,a non-contact voltage measurement method is lacking.Current voltage measurement device need to be in contact with the metal part of the line to be tested to realize voltage measurement.However,in the actual measuring process,voltage may not be measured in some place where is not available to break the insulation,or even in the position where the insulation layer cannot be broken to find the metal contact point.Moreover,the traditional voltage measuring terminal must cut off the power during the installation of the device used to measure voltage,hanging on the line to be tested,which is not convenient for the installation of the temporarily established voltage monitoring point.In view of the above problems,this paper develops a non-contact voltage measuring device that can realize the line voltage measurement without breaking the line insulation and only need to attach the measuring probe to the surface of the insulation layer of the line to be tested.In this paper,the non-contact voltage measurement is realized based on the principle of electric field coupling.Firstly,this paper analyzes the traditional non-contact voltage measurement scheme,and points out that the existing scheme can not calculate the parasitic capacitance value formed between the line to be tested and the device probe in real time,which will lead to measurement error when measuring different types of lines.Then,this paper proposes a new non-contact voltage measurement scheme based on topology transformation,which can solve the unknown parasitic capacitance value and calculate the voltage to be measured,thus eliminating the measurement error caused by the unknown parasitic capacitance between the line under test and the probe.The device is composed of an FPGA core board,a relay unit,an amplifying unit,a collecting unit,a power supply unit,a communication unit and peripheral functional units.This paper completed the hardware design of each functional module of the device and the preliminary design of the digital signal processing program based on FPGA platform.Finally,the physical map of the measuring device prototype is given,and the prototype is subjected to digital filtering and voltage measurement effect testing.The test results show that the digital filtering can effectively filter out the high-frequency noise,and the non-contact voltage measurement test result shows that the measurement error can be controlled within a certain range,which proves that the non-contact voltage measuring device developed in this paper has practical value.