P. S. Shenil

Bio: P. S. Shenil is an academic researcher from College of Engineering, Trivandrum. The author has contributed to research in topics: Voltage & Capacitance. The author has an hindex of 3, co-authored 7 publications receiving 26 citations. Previous affiliations of P. S. Shenil include Indian Institute of Technology Madras.

Feasibility study of a non-contact AC voltage measurement system

Abstract: An instrumentation scheme suitable for non-contact measurement of ac voltage of an insulated conductor is presented in this paper The ac voltage of an insulated conductor can be measured by using a suitable probe that forms a capacitive network between the conductor and the ground Basic idea of such a scheme employing online measurement of the capacitances and then using it for the computation of the unknown voltage has been reported earlier We conducted a feasibility of the scheme, and found that its output suffers from effect of various parasitic parameters of the measurement circuit and the sensor In the study, a detailed analysis of the effect of various circuit and parasitic parameters has been conducted and the same is presented in the paper Based on the inference from the analysis, criteria for the design of the sensor electrodes and other circuit components have been accomplished and presented The paper also discusses a simple calibration method to reduce the effect of certain parasitic parameters and hence increase the accuracy of the measurement Moreover a FFT based processing of the measured data has been used in the presented scheme, instead of the complex methods, including analog multiplication, division, etc employed in the earlier reported scheme A prototype of the non-contact ac voltage measurement system has been developed and tested in the laboratory for various frequencies and voltages Worst-case error noticed in the tests conducted was less than 075 %

Development of a Nonintrusive True-RMS AC Voltage Measurement Probe

Abstract: The design and development of a new nonintrusive-type true-rms ac voltage measurement probe are presented in this paper. The measurement circuit of the capacitively coupled nonintrusive voltage sensor is designed to provide an output that is directly proportional to the rms value of unknown ac voltage $\text{V}_{\mathrm {X}}$ , which contains the power frequency (50 or 60 Hz) component along with the typical harmonic frequency components due to nonlinear loads. This is accomplished by a specially designed autobalancing signal conditioning circuit. The existing noncontact probes are designed for a set frequency and will not provide accurate rms value of a signal that has multiple frequency components. The output is independent of the coupling capacitance between the probe electrode and the insulated wire/cable under measurement. Thus, the sensor has low sensitivity to the variation due to the probe-to-wire capacitance, good linearity (0.95%), and accuracy (0.88%) over a range of voltages (0–1000 V) tested. Various parameters that affect the performance of the probe are analyzed, quantified, and discussed in this paper. A prototype of the probe along with the proposed autobalancing circuit has been designed and developed. The prototype has been tested in detail to evaluate the accuracy, linearity, and repeatability. The results obtained established the practicality of the proposed scheme.

Evaluation of a Digitizer Designed to Interface a Non-Intrusive AC Voltage Measurement Probe

Abstract: A low-cost yet efficient digitizer, suitable for a capacitive type non-contact ac voltage probe is presented. The existing measurement scheme for such a probe requires an interfacing circuit, an analog-to-digital converter followed by a processor to compute fast Fourier transform (FFT) to obtain an output. It will be beneficial and less complex if an analog to digital converter can be developed that can directly interface with the probe and get the final output without FFT computation. Such a scheme that operates based on the dual-slope analog-to-digital conversion technique is presented in this paper. Its output is directly proportional to the fundamental component of the unknown ac voltage. Output has negligible sensitivity to the variations in the probe-to-wire capacitance. The proposed scheme has a new and simple compensation approach to accurately obtain the fundamental of the unknown voltage, even if it has significant 3rd harmonics. A detailed analysis of various sources of errors affecting the performance of the scheme is conducted and the details are presented in the paper. A prototype of the proposed scheme has been designed, developed and interfaced with a laboratory-made non-intrusive ac voltage probe and tested for 0–600 V, at two frequencies, 50 Hz and 60 Hz. The output of the digitizer was linear, with worst-case linearity of 0.26%. The effective number of bits observed for the prototype were 11.16 and 11.85 for 50 Hz and 60Hz measurement respectively.

Nonintrusive AC Voltage Measurement Unit Utilizing the Capacitive Coupling to the Power System Ground

Abstract: A fully nonintrusive type ac voltage measurement scheme is presented in this article. Most of the existing noncontact voltage probes require a direct connection to the power system ground. A few other schemes rely on the capacitive coupling between the body of the human operator, holding the probe, and the ground to connect to the power system ground. This is a less reliable method as the direct contact of the hand of the operator to a specified conductive part in the probe is mandatory. Besides, the existing methods do not take care of the effect of the nature of the impedance of the current path through the earth between the human body and the power system ground. In this article, a new measurement approach that provides reliable output from the nonintrusive probe, irrespective of the variations in the probe-to-wire capacitance and impedance between the measurement system and power system ground through the earth, is presented. This includes the capacitive coupling between the measurement system and the earth. A detailed simulation study of the proposed approach has been conducted, and various sources of error and the effects have been quantified. A prototype probe and measurement unit have been developed and tested in the laboratory for a range of distribution voltage (0-600 V), at 50 and 60 Hz. Tests were also conducted in the actual field (distribution voltage). The output was linear with a maximum error of 0.6%.

An efficient digitizer for non-intrusive ac voltage measurement

Abstract: This paper presents a new low-cost but reliable digitizer, which in combination with a capacitive non-contact ac voltage probe provides a digital output that is directly proportional to the unknown voltage being measured by the probe. The digitizer is designed such that it not only digitizes the signal but also implements the necessary computations required to get the final output directly, with negligible sensitivity to the probe-to-wire capacitance. It was otherwise implemented in earlier approaches using typical Analog to Digital Converter and computation of FFT of the ADC data. The new digitizer utilizes the principle of dual-slope A/D conversion, hence processes high accuracy over the full-scale range. A prototype of the proposed digitizer has been designed, developed and interfaced with a laboratory made non-intrusive ac voltage probe and tested for 0–120 V range at 60 Hz. The measurement was compared with the conventional direct method and the worst-case error was less than 0.85%.

Noncontact RF Voltage Sensing of a Printed Trace via a Capacitive-Coupled Probe

Abstract: This paper presents a noncontact radio frequency voltage sensing of a printed trace by using a capacitive-coupled probe. The noncontact voltage sensing is demonstrated by using an open-end coaxial probe, and achieved through the transfer factor from the printed trace to the probe and a reconstruction algorithm. To validate the voltage sensing, known periodic, and pulse voltages are injected into the printed trace and compared with the reconstructed waveforms. Our results demonstrate that the voltage sensing method can be used for measurement of a random waveform with period even down to 1 ns and single pulse with rise time down to 2 ns. In consideration of the flexible relocation of the probe, the voltage sensing accuracy caused by spatial errors is also investigated.

A Noncontact Voltage Measurement System for Power-Line Voltage Waveforms

Abstract: This paper presents the design and implementation details of a complete noncontact (NC) voltage acquisition system, which allows the measurement of power-line voltage waveforms without galvanic contact. The system is composed by a novel capacitive probe, an analog front end (AFE), and a microcontroller-based digital signal processing stage. A deep experimental characterization of the noncontact measurement system was performed. The tests reported a high linearity (maximum nonlinearity of ±0.2%), a low input-referred noise (11 mVrms), and a low-frequency response distortion. Measurements of ±330-V triangular waveform signals were performed with maximum instantaneous errors below ±1.5 V. The power-line voltage (220 Vrms at 50 Hz) was acquired without galvanic contact with an instantaneous error lower than ±3 V, whereas the mean error on rms voltage measurements was 0.32% and the maximum 0.7%. A two-day continuous measurement of power-line voltage was accomplished for testing system’s stability, resulting in negligible accuracy variations.

Development of a Nonintrusive True-RMS AC Voltage Measurement Probe

Abstract: The design and development of a new nonintrusive-type true-rms ac voltage measurement probe are presented in this paper. The measurement circuit of the capacitively coupled nonintrusive voltage sensor is designed to provide an output that is directly proportional to the rms value of unknown ac voltage $\text{V}_{\mathrm {X}}$ , which contains the power frequency (50 or 60 Hz) component along with the typical harmonic frequency components due to nonlinear loads. This is accomplished by a specially designed autobalancing signal conditioning circuit. The existing noncontact probes are designed for a set frequency and will not provide accurate rms value of a signal that has multiple frequency components. The output is independent of the coupling capacitance between the probe electrode and the insulated wire/cable under measurement. Thus, the sensor has low sensitivity to the variation due to the probe-to-wire capacitance, good linearity (0.95%), and accuracy (0.88%) over a range of voltages (0–1000 V) tested. Various parameters that affect the performance of the probe are analyzed, quantified, and discussed in this paper. A prototype of the probe along with the proposed autobalancing circuit has been designed and developed. The prototype has been tested in detail to evaluate the accuracy, linearity, and repeatability. The results obtained established the practicality of the proposed scheme.

Noncontact AC Voltage Measurements: Error and Noise Analysis

Abstract: A capacitive noncontact ac voltage measurement technique and its feasibility to measure arbitrary waveform signals are analyzed. The method provides self-calibration of the scale factor, an important feature considering the high variability that coupling capacitances present. The analysis of several errors related to the technique is performed, showing the impact of different design parameters on the final accuracy. Scaling errors due to the electronic circuit can be constrained to less than 0.5%, and can be disaffected, whereas those due to the frequency dependence of cable sheath permittivity can be up to 3% for polyvinyl chloride sheathed cables. This error is not controllable by electronic design but requires working on electrode probe. A noise model is also proposed and experimentally validated, showing that signal-to-noise ratios of up to 100 dB are achievable with common components. A functional prototype was built and tested by acquiring power-line voltage and other arbitrary signals without contact. Instantaneous voltage signals were acquired by the proposed technique and contrasted with those acquired directly. For the measurement of power-line voltage and using the self-calibration feature, the instantaneous error was lower than 7 V (2.2%) for a ±1300 V measurement range at 50 Hz. If manual correction is applied, the error can be reduced to 0.28 $\text{V}_{\text {rms}}$ (0.12%).

Non-contact long range AC voltage measurement

Abstract: Safety requirements and physical constraints often prohibit contacting high voltage terminals. This limits the options for monitoring and maintaining high voltage machinery and power distribution grids. We present a non-contact AC (alternating current) voltage and frequency measurement system with 600 mm of operation range to overcome this issue. The method relies on measuring the electric potential of an AC voltage source using a single capacitive electrometer. Simultaneously, the distance from the AC source is measured using time-of-flight sensors. By combining the data from both sensors, AC voltages can be measured accurately without the need for any galvanic contact. The system is packaged in a handheld battery powered form factor. Measurements of voltages between 25 VRMS and 250 VRMS and distances from 25 mm to 600 mm demonstrated accuracy within 4%. Furthermore, frequencies between 5 Hz to 500 Hz were measured with 10 mHz of resolution. The presented technique can be used as a test and measurement instrument where the source terminals are inaccessible or as a wearable safety device in high-voltage environments.