This document discusses using the time-integral of leakage current as an index for monitoring overhead insulators under harmonic voltages. It proposes that the time-integral is less sensitive to changes in voltage harmonics compared to other leakage current indices.
The time-integral accounts for the total area under the leakage current waveform over one cycle. It can be expressed as the sum of the integrals of the individual harmonic components in the current. The contribution of higher order harmonics to the total integral is inversely proportional to the harmonic order and reduces their influence.
Experimental data showed that changes in voltage harmonics primarily affect the corresponding harmonic in leakage current, not other harmonics or the fundamental. This causes a small change in the time-
Turbulent Flow in Curved Square Duct: Prediction of Fluid flow and Heat trans...IRJET Journal
This document summarizes a study that used computational fluid dynamics (CFD) to numerically simulate and experimentally investigate turbulent flow and heat transfer characteristics in a curved square duct. Secondary flows were generated in the duct due to imbalances between centrifugal forces and radial pressure gradients. The SST K-ω turbulence model was used to simulate flow. It was found that secondary flow intensities were highest near duct walls and enhanced mixing and heat transfer. Temperature distributions were non-uniform across the duct due to higher velocities near the concave wall carrying away more heat. Numerical results agreed well with experimental measurements.
This document summarizes Mahbod Shafiei's major final project presentation submitted at Budapest University of Technology and Economics. The project involved modeling and simulating a water distribution pipe network in Budapest, Hungary. Key aspects included:
1. Building an EPANET model of the pipe network using population and water demand projections out to 2030.
2. Optimizing the model by adding extra loops to increase pressure while decreasing velocity and pressure drops.
3. Simulating leaks in the network using emitter coefficients and monitoring changes in pressure and flow rates to estimate leak locations.
4. Modeling the effects of pipe breaks by removing pressure from nodes and comparing impacts on other branches with and
Computational Analysis of Turbulent flow heat transfer and pressure loss in D...IRJET Journal
This document discusses computational analysis of turbulent flow, heat transfer, and pressure loss in ducts or pipes with segmental baffles. Segmental baffles are implemented to enhance flow characteristics and thermal performance. Due to the baffles, significant turbulence is generated, increasing friction with the pipe and improving heat transfer but also leading to greater pressure drop. Finite element analysis is conducted using ANSYS Fluent to simulate turbulent flow over a range of Reynolds numbers in smooth and baffled pipes. Results are validated against published experimental and numerical data and show good agreement. Contour plots illustrate increased turbulence and velocity magnitude in baffled pipes compared to smooth pipes.
technoloTwo dimensional numerical simulation of the combined heat transfer in...ijmech
A numerical investigation was conducted to analyze the flow field and heat transfer characteristics in a vertical channel withradiation and blowing from the wall. Hydrodynamic behaviour and heat transfer results are obtained by the solution of the complete Navier–Stokesand energy equations using a control volume finite element method. Turbulent flow with "Low Reynolds Spalart-Allmaras Turbulence Model" and radiation with "Discrete Transfer Radiation Method" had been modeled. In order to have a complete survey, this article has a wide range of study in different domains including velocity profiles at different locations, turbulent viscosity, shear stress, suctioned mass flow rate in different magnitude of the input
Rayleigh number, blowing Reynoldsnumber, radiation parameter, Prandtl number, the ratio of length to width and also ratio of opening thickness to width of the channel. In addition, effects of variation in any of the above non-dimensional numbers on parameters of the flow are clearly illustrated. At the end resultants had been compared with experimental data which demonstrated that in the present study, results have a great accuracy, relative errors are very small and the curve portraits are in a great
agreement with real experiments.
This document provides guidance on sampling principles for hydrological and hydro-meteorological variables. It discusses units of measurement, basic statistics, measurement error, sampling frequency, sampling in space, and network design. The key topics covered include defining sampling terms, describing common statistical distributions, estimating parameters and errors from samples, addressing errors from discrete time and spatial sampling, and designing monitoring networks based on sampling objectives and system characteristics.
THEORETICAL STUDY ON PIPE OF TAPERED THICKNESS WITH AN INTERNAL FLOW TO ESTIM...IAEME Publication
This research study the effect of tapered thickness on the free transverse vibration of clamped – free pipe which have uniform circular cross section conveying water by using Raighly –Ritz method in the two case, the first involves the pipe have a constant wall thickness (t1) at clamped end equal to (1mm & 2mm) while the thickness (t2) at free end changes according to the ratio (t2/t1=0.2, 0.4, 0.6, 0.8, 1). In the second case the thickness at free end (t2) is constant (1mm & 2mm) whereas the thickness at clamped end (t1) changes at ratio (t1/t2=0.2, 0.4, 0.6, 0.8, 1). The pipe has a constant inner radius (Ri) of (1 cm or 2 cm) and different values of length (1m & 2m).
Numerical Investigation of Mixed Convective Flow inside a Straight Pipe and B...iosrjce
The present study deals with a numerical investigation of steady laminar and turbulent mixed
convection heat transfer in a horizontal pipe and bend pipe using air as the working fluid.The thermal boundary
condition chosen is that of uniform temperature at the outer wall. Computations were performed to investigate
the effect of inlet Rayleigh number and Reynolds number in the velocity and temperature profile at inside of the
pipe. The secondary flow is more intense in the upper part of the cross-section. It increases throughout the
cross-section until its intensity reaches a maximum, and then it becomes weak at far downstream. For the
horizontal pipe the value of the L/D ratio becomes more than 10 the secondary flow effects are neutralized and
the velocity profile almost become constant throughout.
THE STUDY OF THE EFFECTS OF RADIATION AND BLOWING FROM THE WALL OF A VERTICAL...ijmech
This article investigates the effects of radiation and blowing from a wall on a turbulent heat transfer in vertical channels with asymmetrical heating. The equations involved were numerically solved with three turbulent models including SpalartAllmaras, R-N-G k-
with"Standard Wall Function" wall nearby model, R-N-G k- with "Enhanced Wall Treatment" wall nearby model and "Ray Tracing" radiation techniques. The results were compares with experimental data and appropriate methods were selected for turbulent modeling. The problem
of Rayleigh number, Reynolds, radiation parameters and Prandtl were solved and the effects of these parameters on the flow lines, lines of constant temperature, radiation, convection, heat transfer caused by blowing and the total heat transfer were determined.
Turbulent Flow in Curved Square Duct: Prediction of Fluid flow and Heat trans...IRJET Journal
This document summarizes a study that used computational fluid dynamics (CFD) to numerically simulate and experimentally investigate turbulent flow and heat transfer characteristics in a curved square duct. Secondary flows were generated in the duct due to imbalances between centrifugal forces and radial pressure gradients. The SST K-ω turbulence model was used to simulate flow. It was found that secondary flow intensities were highest near duct walls and enhanced mixing and heat transfer. Temperature distributions were non-uniform across the duct due to higher velocities near the concave wall carrying away more heat. Numerical results agreed well with experimental measurements.
This document summarizes Mahbod Shafiei's major final project presentation submitted at Budapest University of Technology and Economics. The project involved modeling and simulating a water distribution pipe network in Budapest, Hungary. Key aspects included:
1. Building an EPANET model of the pipe network using population and water demand projections out to 2030.
2. Optimizing the model by adding extra loops to increase pressure while decreasing velocity and pressure drops.
3. Simulating leaks in the network using emitter coefficients and monitoring changes in pressure and flow rates to estimate leak locations.
4. Modeling the effects of pipe breaks by removing pressure from nodes and comparing impacts on other branches with and
Computational Analysis of Turbulent flow heat transfer and pressure loss in D...IRJET Journal
This document discusses computational analysis of turbulent flow, heat transfer, and pressure loss in ducts or pipes with segmental baffles. Segmental baffles are implemented to enhance flow characteristics and thermal performance. Due to the baffles, significant turbulence is generated, increasing friction with the pipe and improving heat transfer but also leading to greater pressure drop. Finite element analysis is conducted using ANSYS Fluent to simulate turbulent flow over a range of Reynolds numbers in smooth and baffled pipes. Results are validated against published experimental and numerical data and show good agreement. Contour plots illustrate increased turbulence and velocity magnitude in baffled pipes compared to smooth pipes.
technoloTwo dimensional numerical simulation of the combined heat transfer in...ijmech
A numerical investigation was conducted to analyze the flow field and heat transfer characteristics in a vertical channel withradiation and blowing from the wall. Hydrodynamic behaviour and heat transfer results are obtained by the solution of the complete Navier–Stokesand energy equations using a control volume finite element method. Turbulent flow with "Low Reynolds Spalart-Allmaras Turbulence Model" and radiation with "Discrete Transfer Radiation Method" had been modeled. In order to have a complete survey, this article has a wide range of study in different domains including velocity profiles at different locations, turbulent viscosity, shear stress, suctioned mass flow rate in different magnitude of the input
Rayleigh number, blowing Reynoldsnumber, radiation parameter, Prandtl number, the ratio of length to width and also ratio of opening thickness to width of the channel. In addition, effects of variation in any of the above non-dimensional numbers on parameters of the flow are clearly illustrated. At the end resultants had been compared with experimental data which demonstrated that in the present study, results have a great accuracy, relative errors are very small and the curve portraits are in a great
agreement with real experiments.
This document provides guidance on sampling principles for hydrological and hydro-meteorological variables. It discusses units of measurement, basic statistics, measurement error, sampling frequency, sampling in space, and network design. The key topics covered include defining sampling terms, describing common statistical distributions, estimating parameters and errors from samples, addressing errors from discrete time and spatial sampling, and designing monitoring networks based on sampling objectives and system characteristics.
THEORETICAL STUDY ON PIPE OF TAPERED THICKNESS WITH AN INTERNAL FLOW TO ESTIM...IAEME Publication
This research study the effect of tapered thickness on the free transverse vibration of clamped – free pipe which have uniform circular cross section conveying water by using Raighly –Ritz method in the two case, the first involves the pipe have a constant wall thickness (t1) at clamped end equal to (1mm & 2mm) while the thickness (t2) at free end changes according to the ratio (t2/t1=0.2, 0.4, 0.6, 0.8, 1). In the second case the thickness at free end (t2) is constant (1mm & 2mm) whereas the thickness at clamped end (t1) changes at ratio (t1/t2=0.2, 0.4, 0.6, 0.8, 1). The pipe has a constant inner radius (Ri) of (1 cm or 2 cm) and different values of length (1m & 2m).
Numerical Investigation of Mixed Convective Flow inside a Straight Pipe and B...iosrjce
The present study deals with a numerical investigation of steady laminar and turbulent mixed
convection heat transfer in a horizontal pipe and bend pipe using air as the working fluid.The thermal boundary
condition chosen is that of uniform temperature at the outer wall. Computations were performed to investigate
the effect of inlet Rayleigh number and Reynolds number in the velocity and temperature profile at inside of the
pipe. The secondary flow is more intense in the upper part of the cross-section. It increases throughout the
cross-section until its intensity reaches a maximum, and then it becomes weak at far downstream. For the
horizontal pipe the value of the L/D ratio becomes more than 10 the secondary flow effects are neutralized and
the velocity profile almost become constant throughout.
THE STUDY OF THE EFFECTS OF RADIATION AND BLOWING FROM THE WALL OF A VERTICAL...ijmech
This article investigates the effects of radiation and blowing from a wall on a turbulent heat transfer in vertical channels with asymmetrical heating. The equations involved were numerically solved with three turbulent models including SpalartAllmaras, R-N-G k-
with"Standard Wall Function" wall nearby model, R-N-G k- with "Enhanced Wall Treatment" wall nearby model and "Ray Tracing" radiation techniques. The results were compares with experimental data and appropriate methods were selected for turbulent modeling. The problem
of Rayleigh number, Reynolds, radiation parameters and Prandtl were solved and the effects of these parameters on the flow lines, lines of constant temperature, radiation, convection, heat transfer caused by blowing and the total heat transfer were determined.
This document summarizes research on multiphase flow instrumentation and measurement techniques being developed in Brazil. It describes three sensors: 1) A resonant cavity sensor that measures water cut using resonance frequency shifts; 2) An electrical capacitance tomograph that estimates phase fractions using capacitance measurements between electrode pairs; 3) A wire-mesh sensor that provides 2D phase distribution images using conductivity or capacitance measurements at wire crossings. Experiments show the techniques can accurately measure phase fractions in oil-water and air-water flows.
Sensoring Leakage Current to Predict Pollution Levels to Improve Transmission...Yayah Zakaria
Pollution insulator is a serious threat to the safety operations of electric power systems. Leakage current detection is widely employed in transmission line insulators to assess pollution levels. This paper presents the prediction of pollution levels on insulators based on simulated leakage current and voltage in a transmission tower.The simulation parameters are based on improved transmission line model with leakage current resistance insertion between buses. Artificial neural network (ANN) is employed to predict the level of pollution with different locations of simulated leakage current and voltage between two buses. With a sufficient number of training, the test results showed a significant potential for pollution level prediction
with more than 95% Correct Classification Rate (CCR) and output of the ANN showed high agreement with Simulink results.
Sensoring Leakage Current to Predict Pollution Levels to Improve Transmission...IJECEIAES
This document discusses using artificial neural networks (ANN) to predict pollution levels on transmission line insulators based on simulated leakage current and voltage data. Simulation data is collected from a 5-bus test system model with an improved transmission line model that includes a leakage current resistance parameter. Leakage current and voltage are measured at different locations along short and medium transmission lines for different pollution levels. This data is used to train an ANN using a feedforward backpropagation algorithm. Test results showed the ANN could predict pollution levels with over 95% accuracy based on the training data. The ANN is able to classify pollution levels into three categories: low, medium, and high pollution.
EFFECT OF EQUAL AND MISMATCHED SIGNAL TRANSITION TIME ON POWER DISSIPATION IN...VLSICS Design
High density chips have introduced problems like crosstalk noise and power dissipation. The mismatching in transition time of the inputs occurs because different lengths of interconnects lead to different parasitic values. This paper presents the analysis of the effect of equal and unequal (mismatched) transition time of inputs on power dissipation in coupled interconnects. Further, the effect of signal skew on transition time is analysed. To demonstrate the effects, a model of two distributed RLC lines coupled capacitively and inductively is taken into consideration. Each interconnect line is 4mm long and terminated by capacitive load of 30fF. The analysis is carried out for simultaneously switching lines. The results are obtained through SPICE simulations and waveforms are generated.
FLOW DISTRIBUTION NETWORK ANALYSIS FOR DISCHARGE SIDE OF CENTRIFUGAL PUMPijiert bestjournal
A computational fluid dynamics (CFD) analysis has been conducted to f ind the pressure losses for dividing and combining fluid flow through a junction of discharge system. Si mulations are performed for a range of flow ratios and equations are developed for pressure loss coeff icients at junctions. A mathematical model based on successive approximations then would be employed to estim ate the pressure losses. The proposed CFD based strategy can be used for the analysis of all the thr ee pipe branches of some diameter are selected along with equal length so that only the effect of bend angle can be studied. The effect of bend angle,pipe diameter,pipe length,Reynolds number on the resistance coeffi cient is studied. The software used is CATIA for modeling and ANSYS fluent for analysis purpose.
An Analysis of Harmonic and Interharmonic Contribution of Electric Arc Furnac...IJECEIAES
Fast and accurate detection of the harmonic and interharmonic contribution of electric arc furnace (EAF) is crucial in identifying and to mitigate the undesired effects to the system. In this paper, periodogram, a fast and accurate technique is introduced for the analysis of the contribution. Based on a rule-based classifier and the threshold settings that referred to the IEEE Standard 1159 2009, the analysis of the harmonic and interharmonic contribution of EAF are carried out successfully. Moreover, the impact of contribution is measured using total harmonic distortion (THD) and total non-harmonic distortion (TnHD). In addition, periodogram also gives 100 percent correct detection and able to analyze the contribution impact. It is proven that the proposed method is accurate, fast and cost efficient for analyzing the impact of harmonic and interharmonic of EAF.
Accurate leakage current models for MOSFET nanoscale devices IJECEIAES
This paper underlines a closed form of MOSFET transistor’s leakage current mechanisms in the sub 100nmparadigm.The incorporation of drain induced barrier lowering (DIBL), Gate Induced Drain Lowering (GIDL) and body effect (m) on the sub-threshold leakage (I sub ) was investigated in detail. The Band-To-Band Tunneling (I BTBT ) due to the source and Drain PN reverse junction were also modeled with a close and accurate model using a rectangular approximation method (RJA). The three types of gate leakage (I G ) were also modeled and analyzed for parasitic (I GO ), inversion channel (I GC ), and gate substrate (I GB ). In addition, the leakage resources due to the aggressive reduction in the oxide thickness (<5nm) have been investigated. Simulation results using HSPICE exhibits a tremendous agreement with the BSIM4 model. The dominant value of the sub-threshold leakage was due to the DIBL and GIDL effects. Various recommendations regarding minimizing the leakage current at both device level and the circuit level were suggested at the end of this paper.
A novel fuzzy based controller to reduce circulating currents in parallel int...IJECEIAES
This paper exhibits suppression strategy of low frequency circulating current components for parallel inter-leaved converters. Here inverters are parallelized by magnetically coupled inductors. Traditionally, carrier interleaved technique was used to get lower distorted output voltage, but it gives a higher circulating currents to flow through the Two-VSC‘s. The mutual inductance of the coupled inductors (CI) is utilized for minimizing circulating currents of high frequency components. Nevertheless, CI can‘t have capability to riddle the components generated by low frequency. When these circulating currents extremely increases may leads to CI saturation, elevated switching losses and diminishes the entire performance of system. Here author identified a novel control technique for a grid-connected parallel inter-leaved converter depending on approach of energy shaping control (ECS). This controller diminishes the value of the low frequency components of circulating current (LFCC). The performance of the proposed circuit is evaluated in simulation mode and correlated with the conventional proportional integral control (PIC) and the linear quadratic control (LQC). The Fuzzy controller is also included in this work to enhance the converter performance effectively and to diminish the circulating currents along with the healthy harmonic performance analysis.
Power quality improvement in a weak bus system using facts controllereSAT Journals
Abstract Power quality management is the main problem that the industry is facing today. This is mainly affected by the generation of harmonics. The growing use of electronic equipment produces a large amount of harmonics in distribution systems because of non-sinusoidal currents consumed by non-linear loads. As we know for the better quality of power, the voltage and current waveforms should be sinusoidal, but in actual practice it is somewhat disturbed and this phenomenon is called “Harmonic Distortion”. Voltage harmonics are generally present in supply of power from utility. Even though electronic and non-linear devices are flexible, economical and energy efficient, they may degrade power quality by creating harmonic currents and consuming excessive reactive power. The STATCOM as FACTS controller can be applied to a single non-linear load or many. It provides controlled current injection to remove harmonic current from the source side of electric system and also can improve the power factor. Keywords-: Controller design, PI Controller, FACTS and STATCOM.
An approach to Measure Transition Density of Binary Sequences for X-filling b...IJECEIAES
Switching activity and Transition density computation is an essential stage for dynamic power estimation and testing time reduction. The study of switching activity, transition densities and weighted switching activities of pseudo random binary sequences generated by Linear Feedback shift registers and Feed Forward shift registers plays a crucial role in design approaches of Built-In Self Test, cryptosystems, secure scan designs and other applications. This paper proposed an approach to find transition densities, which plays an important role in choosing of test pattern generator We have analyze conventional and proposed designs using our approache, This work also describes the testing time of benchmark circuits. The outcome of this paper is presented in the form of algorithm, theorems with proofs and analyses table which strongly support the same. The proposed algorithm reduces switching activity and testing time up to 51.56% and 84.61% respectively.
A Fast Localization of Multiple Harmonic Sources for Rectifier Loads by Utili...TELKOMNIKA JOURNAL
This paper introduces a fast method to localize the multiple harmonic sources (MHS) for rectifier
based loads in power distribution system by utilizing periodogram technique with a single-point
measurement approach at the point of common coupling (PCC). The periodogram is a fast and accurate
technique for analyzing and distinguishing MHS location in power system. Matlab simulation is carried out
several unique cases on IEEE test feeder cases due to validate the proposed method. The identification of
MHS location is based on the significant relationship of spectral impedance which are fundamental
impedance (Z1) and harmonic impedance (Zh) that's extracted from an impedance power spectrum. It is
verified that the proposed method is fast, accurate, and cost efficient in localizing MHS. In addition, this
method also contributes 100% correct identification of MHS location.
IRJET- Remote Monitoring of Critical Parameters of HV SubstationIRJET Journal
This document presents a new approach for remote monitoring of critical electrical parameters in high voltage substations using non-contact hall sensors and wireless communication. Hall sensors can measure current in a conductor without direct contact and produce a voltage signal proportional to the current. This signal is sent to a microcontroller which converts it to a digital signal containing the current value. The value is displayed on an LCD screen. A simulation and hardware prototype were developed to validate the concept. The system allows accurate and effective non-contact monitoring of equipment parameters in remote HV substations.
This document summarizes various regulator collections that can be used to control a parallel active power filter. It discusses fuzzy logic, PWM, space vector PWM (SVPWM), new space vector PWM (NSVPWM), and hysteresis regulators. It provides block diagrams and equations to describe how each regulator works. The document also proposes a new method of using NSVPWM with hysteresis control to regulate harmonic currents injected by the active filter while maintaining a fixed switching frequency.
Fuzzy logic approach to control the magnetization level in the magnetic 2IAEME Publication
This document describes a fuzzy logic approach to control the magnetization level in the magnetic core of a welding transformer. The goal is to prevent saturation of the core which can cause current spikes that lead to system shutdown. A fuzzy logic controller is proposed to maintain the magnetization level and welding current within optimal limits through closed-loop control of the transformer's primary voltage. Membership functions define the inputs of core flux level and welding current and the single output of primary voltage. Rules are defined so that if the flux or current exceed limits, the voltage direction is reversed to reduce the flux level. The Mamdani algorithm is used to implement the fuzzy logic controller as a replacement for one of the previously used hysteresis controllers.
Fuzzy logic approach to control the magnetization level in the magnetic 2IAEME Publication
This document describes a fuzzy logic approach to control magnetization levels in the magnetic core of a welding transformer. The fuzzy logic controller is proposed to work alongside an artificial neural network-based detector of magnetic saturation. Membership functions are defined for the controller inputs of flux and welding current, and output of transformer primary voltage. Rules are defined so that if flux or current exceed limits, the voltage direction is reversed to reduce flux. Simulation results show the controller maintains flux and current within limits, preventing current spikes that could cause overcurrent protection and system shutdown. The fuzzy logic approach provides an alternative to typically used hysteresis controllers.
Transient response of grounding systems under impulse lightning currentHimmelstern
This document summarizes research on modeling the transient response of grounding systems during lightning strikes. It develops a lumped parameter model using transmission line theory to represent the distributed parameters of grounding conductors. The model accounts for time-varying soil properties like resistivity and ionization around electrodes during high current injections. Simulation results show the model can accurately estimate voltages along the grounding system under different lightning impulse currents and validate analytical methods.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Temporary voltage swells and sags appear with high frequency in electric power systems, and they significantly affect sensitive loads such as industrial manufacturing or communication devices. This paper presents a strategy to design proportional-resonant controllers for three full-bridge voltage-source converters with a common DC-link in dynamic voltage restorer systems. The proposed controllers allow the system to quickly overcome temporary unbalanced voltage sags. Simulation results carried out in MATLAB/Simulink and experimental results implemented in a Typhoon HIL402 device demonstrate the ability of the proposed design method. The results show that the system with the proposed controllers can ride-through single-phase or double-phase voltage sags up to 55% and three-phase voltage sags up to 70% in a duration less than one grid-voltage cycle.
Accurate harmonic source identification using S-transformTELKOMNIKA JOURNAL
This document discusses accurate harmonic source identification in power distribution systems using time-frequency analysis with the S-transform. The key points are:
1. The S-transform is proposed for harmonic source identification as it provides better frequency resolution for low frequencies and time resolution for high frequencies compared to other time-frequency analysis techniques.
2. The method involves measuring voltage and current at the point of common coupling and applying the S-transform to obtain the time-frequency representation of the signals.
3. Spectral impedances are extracted from the time-frequency impedance representation, including the fundamental impedance and harmonic impedances. The relationship between these impedances is then used to identify the harmonic source location.
A Smart Flow Measurement System Adaptive to Different Variation Using Ultraso...Sheikh R Manihar Ahmed
This Paper Explain the Design of a Smart Flow measurement Technique using Ultrasonic Flow Meter for custody transfer quality. The objective of the work are; (i) to extend the linearity range of measurement to 100% of the input range, (ii) to make the measurement system adaptive to variations in pipe diameter, liquid density, and liquid temperature. An Accurate flow measurement is an essential requirement both from qualitative and economic points of view. Among the non contact type of flow measurement, ultrasonic flow measurement is widely used to measure flow, because of its advantage like high resolution and less interference of noise on output. However, non linear characteristics of Ultrasonic flow meters have restricted its use. An optimal Computational Logic is considered by comparing various schemes and algorithms based on minimization of Mean Square Error and Regression close to one. The output of ultrasonic flow meter is frequency. It is converted to voltage by using a frequency to voltage converter. An optimal Computational logic block is added in cascade to frequency to voltage converter. This arrangement helps to linearise the overall system for 100% of full scale and makes it adaptive to variations in pipe diameter, liquid density, and liquid temperature. Since the proposed Smart flow measurement technique produces output which is adaptive to variations in pipe diameter, liquid density, and liquid temperature, the present technique avoids the requirement of repeated calibration every time there is change in liquid, and/or pipe diameter, and/or liquid temperature. The results show that proposed measurement technique achieves the objectives quite satisfactorily.
This document summarizes research on multiphase flow instrumentation and measurement techniques being developed in Brazil. It describes three sensors: 1) A resonant cavity sensor that measures water cut using resonance frequency shifts; 2) An electrical capacitance tomograph that estimates phase fractions using capacitance measurements between electrode pairs; 3) A wire-mesh sensor that provides 2D phase distribution images using conductivity or capacitance measurements at wire crossings. Experiments show the techniques can accurately measure phase fractions in oil-water and air-water flows.
Sensoring Leakage Current to Predict Pollution Levels to Improve Transmission...Yayah Zakaria
Pollution insulator is a serious threat to the safety operations of electric power systems. Leakage current detection is widely employed in transmission line insulators to assess pollution levels. This paper presents the prediction of pollution levels on insulators based on simulated leakage current and voltage in a transmission tower.The simulation parameters are based on improved transmission line model with leakage current resistance insertion between buses. Artificial neural network (ANN) is employed to predict the level of pollution with different locations of simulated leakage current and voltage between two buses. With a sufficient number of training, the test results showed a significant potential for pollution level prediction
with more than 95% Correct Classification Rate (CCR) and output of the ANN showed high agreement with Simulink results.
Sensoring Leakage Current to Predict Pollution Levels to Improve Transmission...IJECEIAES
This document discusses using artificial neural networks (ANN) to predict pollution levels on transmission line insulators based on simulated leakage current and voltage data. Simulation data is collected from a 5-bus test system model with an improved transmission line model that includes a leakage current resistance parameter. Leakage current and voltage are measured at different locations along short and medium transmission lines for different pollution levels. This data is used to train an ANN using a feedforward backpropagation algorithm. Test results showed the ANN could predict pollution levels with over 95% accuracy based on the training data. The ANN is able to classify pollution levels into three categories: low, medium, and high pollution.
EFFECT OF EQUAL AND MISMATCHED SIGNAL TRANSITION TIME ON POWER DISSIPATION IN...VLSICS Design
High density chips have introduced problems like crosstalk noise and power dissipation. The mismatching in transition time of the inputs occurs because different lengths of interconnects lead to different parasitic values. This paper presents the analysis of the effect of equal and unequal (mismatched) transition time of inputs on power dissipation in coupled interconnects. Further, the effect of signal skew on transition time is analysed. To demonstrate the effects, a model of two distributed RLC lines coupled capacitively and inductively is taken into consideration. Each interconnect line is 4mm long and terminated by capacitive load of 30fF. The analysis is carried out for simultaneously switching lines. The results are obtained through SPICE simulations and waveforms are generated.
FLOW DISTRIBUTION NETWORK ANALYSIS FOR DISCHARGE SIDE OF CENTRIFUGAL PUMPijiert bestjournal
A computational fluid dynamics (CFD) analysis has been conducted to f ind the pressure losses for dividing and combining fluid flow through a junction of discharge system. Si mulations are performed for a range of flow ratios and equations are developed for pressure loss coeff icients at junctions. A mathematical model based on successive approximations then would be employed to estim ate the pressure losses. The proposed CFD based strategy can be used for the analysis of all the thr ee pipe branches of some diameter are selected along with equal length so that only the effect of bend angle can be studied. The effect of bend angle,pipe diameter,pipe length,Reynolds number on the resistance coeffi cient is studied. The software used is CATIA for modeling and ANSYS fluent for analysis purpose.
An Analysis of Harmonic and Interharmonic Contribution of Electric Arc Furnac...IJECEIAES
Fast and accurate detection of the harmonic and interharmonic contribution of electric arc furnace (EAF) is crucial in identifying and to mitigate the undesired effects to the system. In this paper, periodogram, a fast and accurate technique is introduced for the analysis of the contribution. Based on a rule-based classifier and the threshold settings that referred to the IEEE Standard 1159 2009, the analysis of the harmonic and interharmonic contribution of EAF are carried out successfully. Moreover, the impact of contribution is measured using total harmonic distortion (THD) and total non-harmonic distortion (TnHD). In addition, periodogram also gives 100 percent correct detection and able to analyze the contribution impact. It is proven that the proposed method is accurate, fast and cost efficient for analyzing the impact of harmonic and interharmonic of EAF.
Accurate leakage current models for MOSFET nanoscale devices IJECEIAES
This paper underlines a closed form of MOSFET transistor’s leakage current mechanisms in the sub 100nmparadigm.The incorporation of drain induced barrier lowering (DIBL), Gate Induced Drain Lowering (GIDL) and body effect (m) on the sub-threshold leakage (I sub ) was investigated in detail. The Band-To-Band Tunneling (I BTBT ) due to the source and Drain PN reverse junction were also modeled with a close and accurate model using a rectangular approximation method (RJA). The three types of gate leakage (I G ) were also modeled and analyzed for parasitic (I GO ), inversion channel (I GC ), and gate substrate (I GB ). In addition, the leakage resources due to the aggressive reduction in the oxide thickness (<5nm) have been investigated. Simulation results using HSPICE exhibits a tremendous agreement with the BSIM4 model. The dominant value of the sub-threshold leakage was due to the DIBL and GIDL effects. Various recommendations regarding minimizing the leakage current at both device level and the circuit level were suggested at the end of this paper.
A novel fuzzy based controller to reduce circulating currents in parallel int...IJECEIAES
This paper exhibits suppression strategy of low frequency circulating current components for parallel inter-leaved converters. Here inverters are parallelized by magnetically coupled inductors. Traditionally, carrier interleaved technique was used to get lower distorted output voltage, but it gives a higher circulating currents to flow through the Two-VSC‘s. The mutual inductance of the coupled inductors (CI) is utilized for minimizing circulating currents of high frequency components. Nevertheless, CI can‘t have capability to riddle the components generated by low frequency. When these circulating currents extremely increases may leads to CI saturation, elevated switching losses and diminishes the entire performance of system. Here author identified a novel control technique for a grid-connected parallel inter-leaved converter depending on approach of energy shaping control (ECS). This controller diminishes the value of the low frequency components of circulating current (LFCC). The performance of the proposed circuit is evaluated in simulation mode and correlated with the conventional proportional integral control (PIC) and the linear quadratic control (LQC). The Fuzzy controller is also included in this work to enhance the converter performance effectively and to diminish the circulating currents along with the healthy harmonic performance analysis.
Power quality improvement in a weak bus system using facts controllereSAT Journals
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2. GHOSH et al.: NOVEL LEAKAGE CURRENT INDEX FOR THE FIELD MONITORING OF OVERHEAD INSULATORS UNDER HARMONIC VOLTAGE 1569
Fig. 1. Schematic arrangement of a typical online leakage current mon-
itoring system showing the effect of voltage harmonics on leakage cur-
rent pattern.
of distributed generating units, renewable energy sources and
associated power electronic components, injection of harmonics
into the system voltage has become a serious issue for the power
network [20], [21]. As a result of frequent variations in the
harmonic content of voltage waveform arising out of changing
nonlinear loads, the corresponding leakage current signal will
change. This is demonstrated in Fig. 1, which shows a schematic
arrangement of a typical online leakage current monitoring
system for overhead insulators [4], [23]. In the absence of
voltage information, the change in leakage current waveform
from LC1 to LC2 will be attributed to changes in surface
contamination, when in reality, the changes are emanating from
voltage harmonics. Therefore, the presence of harmonics in
the voltage can render most leakage current monitoring indices
ineffective, including third-to-fifth harmonic ratios, phase
angle or cumulative charge of individual frequency bands,
which are otherwise known as reliable indicators of insulator
condition.
Keeping this in mind, an alternative approach for condition
monitoring of insulators has been presented in this paper, based
on the instantaneous values of time-integral of leakage current.
Experiments have been carried out in the laboratory to under-
stand the changes in leakage current parameters from contam-
inated insulators exposed to different nonsinusoidal voltages
having varying harmonic content [23]. It has been shown that
the instantaneous value of time-integral, equivalent to the cu-
mulative charge, can exhibit low sensitivity to the presence of
voltage harmonics, an aspect that has not been explored pre-
viously in the context of leakage current measurement for in-
sulator monitoring. The contribution of a particular harmonic
towards the overall time-integral of the leakage current wave-
form has been shown to be inversely proportional to the order
of the harmonics. As a result, any change in the harmonic con-
tent of the system voltage has comparatively a smaller effect on
the time-integral of the leakage current as compared to other
traditional monitoring indices. Therefore, the proposed index
may be used in combination with other traditional monitoring
indices to improve the reliability of the monitoring system under
Fig. 2. Typical leakage current signal and its constituent fundamental
and third harmonic components.
field conditions. The method has been validated through offline
and online implementation of a measurement algorithm in the
laboratory.
II. TIME-INTEGRAL APPROACH OF ANALYZING
LEAKAGE CURRENT
A. Theoretical Background
The time-integral of the leakage current gives the absolute
area under the leakage current waveform. The time-integral Q
of a time-varying leakage current signal s(t) can be expressed as
Q =
s(t)|dt. (1)
Let us consider that the leakage current signal s(t) comprises
of the fundamental s1(t) along with a third harmonic component
s3(t), such that s(t) may be expressed as the sum of the individual
harmonics s1(t) and s3(t) as follows:
s(t) = s1(t) + s3(t). (2)
Let the fundamental and third harmonic components be rep-
resented as time-varying signals given by
s1 = A1 sin (ωt) (3)
s3 = A3 sin (3ωt + θ3) (4)
where A1 and A3 are the amplitudes of the fundamental and
third harmonic components, respectively, ω is the fundamental
frequency and θ3 is the phase difference between the fundamen-
tal and third harmonic. The signal s(t) along with its constituent
harmonics have been shown in Fig. 2.
The time-integral of the signal over one cycle, having time
period T, may also be expressed in terms of s(t) as in (5) or in
terms of s1(t) and s3(t) as in (6),
Q = 2
T /2
0
s(t)dt (5)
Q = 2
T /2
0
(s1(t) + s3(t))dt. (6)
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3. 1570 IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 65, NO. 2, FEBRUARY 2018
The time-integral Q in (6) may be represented as the sum of
individual time-integrals under the fundamental and the third
harmonic, Q1 and Q3, respectively, given by
Q = Q1 + Q3 (7)
where Q1 and Q3 are expressed as
Q1 = 2
T /2
0
s1(t)dt (8)
Q3 = 2
T /2
0
s3(t)dt. (9)
Based on (9) and referring to Fig. 2, it may be observed that in
the positive half cycle of leakage current in the interval [0, T/2],
the shaded areas under the third harmonic component represent
sections that have the same area but of opposite polarity, and
thus will cancel each other. This is also true for the shaded areas
in the interval [T/2, T], and may be mathematically validated by
combining (3) and (4) with (8) and (9).The time-integrals Q1
and Q3 can therefore be written as
Q1 = 2
T /2
0
A1 sin (ωt)dt (10)
Q3 = 2
T /2
0
A3 sin (3ωt + θ3)dt. (11)
Simplifying Q1 and Q3 in (10) and (11) will give the individ-
ual time-integral values as
Q1 =
4A1
ω
(12)
Q3 =
4A3
3ω
cosθ3. (13)
Let P3 represent the peak value of the third harmonic com-
ponent expressed in per unit of the fundamental A1. Then, the
amplitude of the third harmonic component A3 in (13) may be
represented as P3 p.u. of A1. Therefore, Q3 may be rewritten as
a function of the fundamental amplitude A1 as follows:
Q3 =
4P3A1
3ω
cosθ3. (14)
Now, combining (12) and (14), Q3 may be expressed as
Q3 =
P3
3
Q1 cosθ3. (15)
In general, the expression for the contribution of the time-
integral for the kth-order harmonic Qk as a function of the
fundamental component time-integral may be expressed as
Qk =
Pk
k
Q1 cosθk (16)
where Pk represents the amplitude of the kth-order harmonic
expressed in per unit of the fundamental peak value and θk
represents the phase difference between the fundamental and
kth-order harmonic. θk may be determined from the harmonic
information extracted from the leakage current waveform us-
ing any harmonic extraction technique. In this work, the syn-
chronous detection or coherent detection technique has been
used to extract the individual harmonics [24], and θk has been
determined from the extracted harmonic information.
It may be observed from (16) that for a particular value of
Q1, if the fundamental current component is in phase with the
kth-order harmonic component, then the contribution of Qk to-
wards the overall time-integral is the maximum, and is equal to
one cycle of the kth-order harmonic component. This is because
in each interval [0, T/2] and [T/2, T], the time-integral of the
successive half cycles of kth harmonic in the interval will yield
equal areas of opposite polarity and the overall time-integral
for the first (k–1) cycles will be zero. As θk increases, the con-
tribution of Qk as a percentage of Q1 starts reducing due to
the factor cos θk . It needs to be emphasized here that θk is an
essential parameter that can be affected by external factors such
as contamination and humidity [16], [17] as well as voltage
waveforms. However, the advantage of the proposed monitor-
ing index is that irrespective of influence of external factors, the
contribution of the kth-order harmonic towards the time-integral
is limited to a maximum of one cycle of the harmonic. Also, Qk
reduces as the value of k (order of harmonics) increases, further
minimizing the influence of θk for higher order harmonics.
In the case of a practical leakage current waveform, there
will be multiple harmonics in the waveform as against only a
particular harmonic as has been discussed so far. In such cases,
the effect of the time-integral of the individual harmonics will
be additive and may be expressed as
Q =
N
k=1
Qk . (17)
B. Time-Integral Approach as an Index for Identifying
Voltage Distortion-Induced Leakage Current Changes
Leakage current can flow over an insulator surface when the
surface is exposed to contamination and is sufficiently humid.
When the insulator surface is dry, leakage current on the insu-
lator surface will be insignificant, irrespective of the degree of
contamination [25]. On the other hand, under wet conditions
and in the presence of contaminants, a significant amount of
leakage current can flow on the insulator surface. The contami-
nants, which include salt deposits from the environment, tend to
form a conducting layer on the insulator surface in the presence
of moisture [11], [14]. As the degree of contamination increases
with time, the electrolytic dissociation of the salt increases,
thereby increasing the conductivity and raising the magnitude
of the leakage current. Higher magnitude leakage current gives
rise to the possibility of nonuniform heating and formation of
dry-bands, which induces nonlinearity on the insulator surface
[16]. Therefore, a change in the contamination affects the funda-
mental leakage current component due to changes in the surface
conductivity and a change in the harmonics due to surface non-
linearity.
On the other hand, any change in the voltage harmonics at a
given contamination level will change only the corresponding
order of harmonics in the leakage current. This is because the
injection of kth-order harmonic in the system voltage will in-
duce a corresponding change in the kth harmonic in the leakage
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4. GHOSH et al.: NOVEL LEAKAGE CURRENT INDEX FOR THE FIELD MONITORING OF OVERHEAD INSULATORS UNDER HARMONIC VOLTAGE 1571
TABLE I
INSULATOR SAMPLES TESTED
Insulator No. Service History Degree of Aging
Insulator 1 20 Years Severe Corrosion
Insulator 2 10 Years Mild Corrosion
Insulator 3 5 Years Light Corrosion
current, and will not affect the fundamental or any harmonic
other than the kth order. Therefore, a small deviation of the
harmonics in the voltage under a specific contamination level
and humidity should produce a small change in the time inte-
gral of the leakage current as expressed in (16), while a change
in environmental conditions such as contamination or humidity
should induce a comparatively larger change due to changes
in the surface conductivity. This property of the time-integral
can be effective in identifying distortion-induced changes from
contamination-induced changes in leakage current when used
along with traditional monitoring indices.
III. EXPERIMENTAL SETUP
A. Test Samples
The test objects used for the experiments consisted of three
naturally aged 11 kV single-disc cap and pin porcelain insu-
lators collected from the local power transmission company.
The degree of aging and service history of the insulators has
been elaborated in Table I. The insulators were contaminated
using the solid layer method to produce a uniform layer of con-
tamination according to IEC 60507. The contamination slurry
was prepared by mixing different proportions of NaCl with
40 g of Kaolin in 1 L of distilled water to give contamination
layers having ESDD in the range of 0.03–0.05 mg/cm2
and
0.07–0.09 mg/cm2
. The two contamination levels are hence-
forth denoted as contamination level 1 (light) and contamination
level 2 (moderate).
B. Experimental Setup
The experimental setup consists of a programmable high volt-
age harmonic waveform generator capable of supplying a peak
voltage of 20 kV. Different voltage waveforms with different
harmonic contents are applied to the samples under test. The
root-mean-square value of the fundamental component of the
applied voltage waveforms has been maintained at 11 kVrms,
and different harmonics have been injected into the applied
voltage. The applied voltage waveforms are measured with the
help of a digital storage oscilloscope across a resistive voltage
divider via a protective unit. The leakage current is made to
flow to earth via a 10-kΩ noninductive shunt resistor. The volt-
age drop across the shunt resistor was measured by the digital
storage oscilloscope via a protective unit. The data were sam-
pled at a sampling frequency of 50 kHz. The voltage and current
waveforms were stored for offline analysis. The schematic of the
experimental arrangement in the laboratory has been shown in
Fig. 3.
Fig. 3. Schematic of experimental setup in the laboratory.
TABLE II
VOLTAGE WAVEFORMS EMPLOYED FOR STUDYING CHANGES IN LEAKAGE
CURRENT PATTERN
Voltage Waveform Fundamental Harmonic Content
Third Fifth Seventh Ninth
V0 100% – – – –
V1 100% 3% – – –
V2 100% 5% – – –
V3 100% 8% – – –
V4 100% – 3% – –
V5 100% – 5% – –
V6 100% – 8% – –
V7 100% – – 3% –
V8 100% – – 5% –
V9 100% – – 8% –
V10 100% – – – 3%
V11 100% – – – 5%
V12 100% – – – 8%
V13 100% 3% 3% – –
V14 100% 3% – 3% –
V15 100% – 3% 3% –
C. Voltage Waveforms
For testing the insulators under different contamination lev-
els, a set of 16 different voltage waveforms having different
degrees of harmonic distortion have been used, as shown in
Table II. Voltage waveform V0 denotes a purely sinusoidal volt-
age while V1 through V12 contain a single harmonic component
each of varying harmonic percentages. Voltage waveforms V13,
V14, and V15 are composite waveforms having two different
harmonics.
IV. APPLICATION TO EXPERIMENTAL DATA FROM
CONTAMINATED INSULATORS
A. Leakage Current Waveforms and Harmonic Content
The 16 different voltage waveforms tabulated in Table II have
been applied to each contaminated insulator, and the leakage
currents were recorded in the laboratory. Some typical applied
voltage waveforms along with the corresponding leakage cur-
rent waveforms have been shown in Fig. 4 for insulator 2 and
a constant contamination level 2. It may be observed that there
are significant variations in the leakage current pattern and har-
monic content due to changes in voltage harmonics. Fig. 5 shows
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5. 1572 IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 65, NO. 2, FEBRUARY 2018
Fig. 4. Different voltage waveforms (a) V3, (b) V6, (c) V9, (d) V12, and
(e) V15 applied to insulator 2 at contamination level 2, and (f)–(j) the
corresponding leakage currents recorded.
Fig. 5. Changes in leakage current harmonic content for different volt-
age waveforms for insulator 2, contamination level 2.
the changes in the harmonic content of leakage current on insu-
lator 2 at contamination level 2, for the different applied voltage
waveforms for insulator 2, contamination level 2. Such varia-
tions in harmonics are entirely on account of changes in applied
voltage waveforms and not due to changes in surface contam-
ination, making it difficult to monitor the insulators based on
harmonic characteristics.
B. Effect of Voltage Waveform on θk
The influence of voltage waveform on θk has been shown in
Fig. 6 for the third-, fifth-, seventh-, and ninth-order harmonics.
For applied voltage V0, the θk represents the phase difference
between the fundamental and kth harmonic of leakage current
in the absence of harmonics in applied voltage. However, when
a kth-order harmonic is present in the voltage, the θk will be sig-
Fig. 6. Influence of voltage waveform on θk for different order of
harmonics.
Fig. 7. Time-integral of leakage current under different voltage wave-
forms for the three insulators and two contamination levels.
nificantly affected as has been shown in Fig. 6. Typically, V1,
V2, and V3 contain 3%, 5%, and 8% of third harmonic, respec-
tively, and therefore θ3 will deviate from its value corresponding
to voltage waveform V0. In general, significant changes in θk are
observed when the voltage waveforms consist of the kth-order
voltage harmonics, as shown in Fig. 6.
C. Time-Integral of Leakage Current Waveforms
The time-integral of the leakage current was determined for
100 ms sections of waveforms under the 16 applied voltages
for the three insulators, each contaminated to the two levels.
The time-integral values obtained have been shown in Fig. 7
in logarithmic scale. It may be observed from Fig. 7 that the
time-integral of leakage current for any of the insulators at any
contamination level shows little variation with changes in the
harmonic distortion of applied voltage. It is also evident that as
the contamination level changes, there is a marked change in
the value of the time-integral of leakage current, which happens
as a result of the change in surface conductivity of insulators
arising from higher level of contamination.
The time-integral computed from the recorded leakage cur-
rent waveform can also be compared with the time-integral com-
puted from the individual harmonics of leakage current using
the amplitudes and phases of the individual harmonics extracted
from the leakage current waveform. The error between the
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6. GHOSH et al.: NOVEL LEAKAGE CURRENT INDEX FOR THE FIELD MONITORING OF OVERHEAD INSULATORS UNDER HARMONIC VOLTAGE 1573
Fig. 8. Error between time-integral determined from recorded signal
and time-integral obtained from individual harmonics under different
voltages.
time-integral obtained from the individual harmonic compo-
nents and the time-integral obtained directly from the recorded
leakage current has been shown for the different insulators in
Fig. 8. The error between the time-integrals is observed to fall
within a range of approximately ± 2%. This helps in validating
that the practical values of time-integral obtained is in agree-
ment with the theoretical values obtained from (16) discussed
earlier in Section II-A.
D. Sensitivity Analysis of Time-Integral of Leakage
Current With Respect to Voltage Distortions
It has been highlighted previously that the sensitivity of a
monitoring index towards harmonic distortions in system volt-
age is an important criterion for insulator monitoring. Therefore,
the sensitivity of the time-integral towards changes in the total
harmonic distortion (THD) of voltage waveforms needs to be
evaluated against commonly used monitoring indices. In this
section, the sensitivity of leakage current time-integral with re-
spect to voltage distortion has been compared with indices such
as the THD and third-to-fifth harmonic ratio of leakage current
[18], [19]. The sensitivity parameters SQ , STHDi, and SR3/5
have been defined as changes in time-integral, THD, and ratio
of third-to-fifth harmonic ratios of leakage current for a unit
change in THD of voltage and have been depicted in (18)–(20).
The change in parameters used to compute the sensitivities is
determined with respect to the parameter values for purely si-
nusoidal voltage waveform V0 as base
SQ =
ΔQ/Q
ΔTHDv /THDv
(18)
STHDi
=
ΔTHDi/THDi
ΔTHDv /THDv
(19)
SR3 / 5
=
ΔR3/5/R3/5
ΔTHDv /THDv
. (20)
Fig. 9 shows the sensitivity of the three parameters for
different applied voltage waveforms for insulator no. 1 at
Fig. 9. Sensitivity of the different monitoring parameters at different ap-
plied voltage waveforms with respect to their values for a pure sinusoidal
voltage waveform for insulator 1 contamination level 1.
Fig. 10. Histograms showing the occurrences of absolute sensitivity
values for all acquired waveforms (a) SQ , (b) STHDi
, and (c) SR3 / 5
.
contamination level 1. As may be observed, SR3 / 5
, which is
a widely reported parameter for insulator monitoring shows a
high sensitivity to the changes in voltage harmonics. The har-
monic distortion of leakage current is also highly sensitive to
voltage harmonics. However, the time-integral exhibits signifi-
cantly low sensitivity compared to the other parameters.
The sensitivities of the three parameters have been deter-
mined under the different applied voltage waveforms for all
the three insulators at both contamination levels. A total of 90
sensitivity values are obtained for each parameter (3 insulators,
2 contamination levels, and 15 voltage waveforms). In order to
have a better insight into the typical sensitivity of the parameters
irrespective of contamination level or insulator aging, the sen-
sitivity for each parameter has been represented in the form of
histograms in Fig. 10. The histogram represents the number of
occurrences of absolute sensitivity values obtained for different
cases, after rounding off the sensitivity to the nearest multiple
of 0.1. The percentage occurrences along the y-axis, therefore,
represent the number of cases out of the 90 recorded wave-
forms, which have sensitivity values close to the corresponding
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7. 1574 IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 65, NO. 2, FEBRUARY 2018
Fig 11. (a) Typical setup for implementing the measurement algorithm. (b) Schematic representation of the implemented measurement algorithm.
absolute sensitivity depicted along the x-axis. The difference in
sensitivity values for the three parameters is readily available
from a visual inspection of the histograms. Fig. 10(a) shows
that approximately 75% of the signals have sensitivity close
to 0.1 and over 95% of the sensitivity values for time-integral
are under 0.3. In comparison, Fig. 10(b) and (c) shows that a
much larger percentage of the sensitivity parameter has values
above 0.5.
V. ONLINE IMPLEMENTATION OF PROPOSED TECHNIQUE
The proposed time-integral based monitoring index was im-
plemented in an online measurement unit in the laboratory. The
algorithm deployed in the unit computes the time-integral of
the leakage current as well as the third-to-fifth harmonic ra-
tios within a given window, to enable us to compare between
the two indices. The test setup shown in Fig. 11(a) consists
of a contaminated porcelain insulator placed inside a humidity
chamber and connected to the programmable harmonic voltage
generator. Fig. 11(b) shows the schematic of the implemented
measurement algorithm. While testing the system in the labora-
tory, the field conditions were simulated in the following way:
the applied voltage waveforms were programmed to change ran-
domly every 15 min [26]. The data were stored every 15 min to
track the changes in leakage current with voltage waveform.
Fig. 12 demonstrates the results obtained over a 3-h window,
where both the time-integral and third-to-fifth harmonic ratio
recorded every 15 min have been shown, along with the applied
voltages. The relative humidity values have been changed after
every 1 h. It may be observed that when the humidity is in
the range of 50%–55%, the time-integral is close to 12.5 μC
irrespective of the voltage waveforms, while the third-to-fifth-
harmonic ratio varies over a much wider range. As the humidity
increases, the time-integral increases to approximately 16 μC at
a relative humidity of 65% and 20 μC at relative humidity of
80%–90%.
It needs to be emphasized here that the online implementation
done at a constant contamination with varying humidity serves
as a good validation technique for the measurement unit since
changes in contamination and humidity represent two differ-
ent field conditions. Also, during the experiments, although the
Fig. 12. Time-integral and third-to-fifth harmonic ratios of leakage cur-
rent obtained from hardware device over a period of 3 h in the laboratory,
under constant contamination and changing humidity.
TABLE III
COMPARISON OF THIRD-TO-FIFTH-HARMONIC RATIOS AND TIME-INTEGRAL
OF LEAKAGE CURRENT UNDER DIFFERENT ESDD AND CONSTANT HUMIDITY
ESDD Voltage Waveform Third/Fifth Time-
(mg/cm2
) Harmonic Ratio Integral
0.05 V0 (Sinusoidal) 4.12 71.1
V2 (5% of third harmonic) 4.47 70.8
V5 (5% of fifth Harmonic) 0.26 70.1
V8 (5% of seventh Harmonic) 3.46 72.3
0.12 V0 (Sinusoidal) 5.28 123.9
V2 (5% of third harmonic) 7.43 124.8
V5 (5% of fifth Harmonic) 0.36 122.1
V8 (5% of seventh Harmonic) 7.69 125.5
0.16 V0 (Sinusoidal) 7.31 172.0
V2 (5% of third harmonic) 5.09 171.4
V5 (5% of fifth Harmonic) 0.42 169.1
V8 (5% of seventh Harmonic) 6.51 172.3
leakage current magnitudes were observed to increase with an
increase in humidity, but the overall leakage current was stable,
making it possible to accurately study the effect of environmen-
tal factors on the time-integral of leakage current.
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8. GHOSH et al.: NOVEL LEAKAGE CURRENT INDEX FOR THE FIELD MONITORING OF OVERHEAD INSULATORS UNDER HARMONIC VOLTAGE 1575
Table III presents a comparison between the time-integral
and third-to-fifth harmonic ratios at three different ESDD lev-
els and constant humidity under different voltage waveforms.
It may be observed that the third-to-fifth harmonic ratio is sig-
nificantly affected by the harmonics in voltage waveform at a
given ESDD and becomes inaccurate as a monitoring index. In
comparison, while the time-integral remains fairly stable under
constant ESDD irrespective of harmonics in voltage waveforms,
an increase in the ESDD is accompanied by an increase in the
time-integral of leakage current, making it a reliable index for
insulator monitoring.
VI. CONCLUSION
In this paper, a novel online monitoring index based on the in-
stantaneous time-integral of leakage current has been proposed
for monitoring and diagnosis of overhead insulators. The major
contribution of the proposed method is that the time-integral
based index, which is equivalent to the cumulative charge, ex-
hibits a significantly lower sensitivity to changes in voltage
harmonics as compared to previously reported popular leakage
current indices. It has been mathematically demonstrated that
the contribution of the time-integral of any harmonic compo-
nent towards the overall time-integral is directly proportional
to the peak magnitude of the harmonic expressed as per unit
of the magnitude of fundamental and the cosine of the phase
angle between the harmonic and the fundamental, while it is
inversely proportional to the order of the harmonics. Since the
time-integral is inversely proportional to the order of harmonics,
the maximum contribution of the harmonic component towards
the time-integral of the overall leakage current is limited to a
maximum of one cycle of the harmonic, which makes the pro-
posed index less sensitive to harmonic changes as compared
to other indices. It needs to be emphasized here that the exact
value of the time-integral will be dependent on the phase angle
θk , which is influenced by external factors such as contamina-
tion, humidity, and voltage harmonics. Therefore, it is further
possible to improve the efficiency of the proposed method by
investigating in detail the nature in which θk is influenced by the
external factors under field conditions. This could be a potential
research area for further development and future applications of
the proposed technique.
It has been highlighted that while the time-integral exhibits
low-sensitivity to leakage current changes on account of volt-
age distortions, it is sensitive to change in the degree of surface
contamination. The results have been validated using both lab-
oratory recorded offline data as well as online implementation.
The results obtained demonstrate that the proposed index may
be effectively employed along with other traditional monitor-
ing indices to discriminate between voltage distortion-induced
changes from contamination-induced changes in leakage cur-
rent, thereby making the technique suitable for possible on-field
implementation.
ACKNOWLEDGMENT
The authors would like to thank Dr. S. Dalai, Assistant Profes-
sor, Department of Electrical Engineering, Jadavpur University,
and A. Kumar, Jadavpur University, for their active interest and
support in carrying out this research work.
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Riddhi Ghosh (M’16) received the B.E. degree
in electrical engineering and the M.E.E. degree
in high-voltage engineering from Jadavpur Uni-
versity, Kolkata, India, in 2007 and 2012, respec-
tively, where he is currently working toward the
Ph.D. degree in electrical engineering.
He is currently a Research Fellow with the
High Tension Laboratory, Department of Elec-
trical Engineering, Jadavpur University. His re-
search interests include advanced techniques
for data acquisition and signal analysis for re-
mote condition monitoring of high-voltage systems.
Biswendu Chatterjee (M’12–SM’17) received
the M.E.E. and Ph.D. degrees in engineering
from Jadavpur University, Kolkata, India, in 2004
and 2009, respectively.
He is currently an Assistant Professor
with the Department of Electrical Engineering,
Jadavpur University. He has published more
than 40 research papers of which 21 are in re-
puted international journals. He has also au-
thored one book and has one U.S. patent in
his name. His current research interests in-
clude data acquisition and condition monitoring related to high voltage
systems.
Sivaji Chakravorti (M’90–SM’00) received the
Ph.D. degree in electrical engineering from Ja-
davpur University, Kolkata, India, in 1993.
Since 2003, he has been serving as a Pro-
fessor with the Department of Electrical Engi-
neering, Jadavpur University. He worked at the
Technical University Munich as a Humboldt Re-
search Fellow during 1995–1996, 1999, and
2007. He served as a Development Engineer
with Siemens AG, Berlin, Germany, in 1998.
He was a US-NSF Guest Scientist with Virginia
Tech, in 2003. He is currently a Director of the National Institute of Tech-
nology, Calicut, India. He has published more than 160 research papers,
has authored two books, and developed three online courses. His cur-
rent research interests include numerical field computation, condition
monitoring of transformers, signal conditioning in high-voltage systems,
application of artificial intelligence in high-voltage systems, and life-long
learning techniques.
Dr. Chakravorti is a Fellow of the Indian National Academy of En-
gineering and a Distinguished Lecturer of the IEEE Power and Energy
Society.
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