Voltage Response Measurements Research Articles

A Method for Assessing the Degradation of PVC-Insulated Low-Voltage Distribution Cables Exposed to Short-Term Cyclic Aging

The distribution grid comprises cables with diverse constructions. The insulating material used in low-voltage (LV) distribution cables is predominantly PVC. Furthermore, the presence of cables with different structures in the grid poses challenges in detecting the aging of the cable network. Finding a universal and dependable condition-monitoring technique that can be applied to various types of cables is indeed a challenge. The diverse construction and materials used in different cables make it difficult to identify a single monitoring approach that can effectively assess the condition of all cables. To address this issue, this study aims to compare the thermal aging behavior of different LV distribution cables with various structures, i.e., one cable contains a PVC belting layer, while the other contains filler material. The growing adoption of distributed generation sources, electric vehicles, and new consumer appliances in low-voltage distribution grids can lead to short, repetitive overloads on the low-voltage cable network. Hence, these cable samples were exposed to short-term cyclic accelerated aging in the climate chamber at 110 °C. The cable’s overall behavior under thermal stress was evaluated through frequency and time domain electrical measurements (including tan δ and extended voltage response) and a mechanical measurement (Shore D). The tan δ was measured in the frequency range of 20 Hz–500 kHz by using the Wayne-Kerr impedance analyzer. The extended voltage response measurement was conducted using a C# application developed in-house specifically for laboratory measurements in the .NET environment. The study observed a strong correlation between the different measurement methods used, indicating that electrical methods have the potential to be adopted as a non-destructive condition-monitoring technique.

Determination of Trap Distribution Based on Voltage Response Measurement for Condition Monitoring of Nuclear Power Plant I&C Cables

Determination of Trap Distribution Based on Voltage Response Measurement for Condition Monitoring of Nuclear Power Plant I&C Cables

Study on the Behavior of Low-Voltage Cable Insulation Subjected to Thermal Cycle Treatment

Abstract The paper presents a study on the effects of thermal aging on a low-voltage cable. Cable samples with a length of 50 cm were subjected to thermal cycling from +140 °C to −20 °C in a climate chamber with controlled temperature. This treatment compares the short-term failure or the emergency overload of some cables under real operating conditions at low temperatures. The effect of the temperature cycle is investigated through electrical measurements such as dielectric spectroscopy, voltage response measurements, and mechanical measurements such as Shore D hardness investigation. The results revealed that the thermal cycles of accelerated aging caused the plasticizer to diffuse into the jacket and then be released into the environment. At the same time, the thermal shocks produced microcracks in the cable jacket, accelerating the removal of the plasticizer.

An effective method to avoid charge leakage along the surface in voltage response measurement.

The voltage response measurement is a non-destructive method to diagnose the aging condition of insulation and is used extensively. The characteristics about the volume polarization and resistance can be obtained by analyzing the measured decay or return voltage of a charged dielectric, which is important for aging diagnosis. To eliminate the influence of the charges leaking along the sample surface on the voltage response analysis, we present an effective three electrode configuration with a potential guard electrode. The voltage decay results show that adopting electrodes with a potential guard electrode can effectively avoid charge leakage along the sample surface.

Parameterization of Debye Model for Dielectrics Using Voltage Response Measurements and a Benchmark Problem

The Voltage Response measurement since its introduction in the 1960s has been used successfully for the diagnostics of electrical insulation. The method is based on two quantities of decay and return voltage slopes and can be used to study the conduction and polarization processes inside the insulation. Extended Voltage Response method, being an advanced version of the Voltage Response measurement helps in further studying the polarization process by using a large polarization spectrum and hence dielectric relaxation processes. These dielectric relaxation processes can be modeled by the Debye model. Since as most of the techniques used for diagnostic purpose does not give the information about the conduction and polarization processes separately, it is difficult to determine the R-C parameters of the Debye model. The Voltage Response technique is very useful in this regard because of the two voltage slopes. The paper shows a novel experimental benchmark for testing the function fitting methodologies of the Voltage Response methodologies, which helps in determining the R-C parameters. Moreover, the problem can be used for testing the novel genetic, evolutionary algorithms, where benchmarking is an actual challenge. The proposed nonlinear function fitting method uses the genetic algorithms via the Ārtap framework, which lets it possible to select the most accurate optimization algorithm from the provided list of the algorithms and achieve better fitting precision, faster calculation time or more powerful processing ability.

Dielectric Measurement Based Deducted Quantities to Track Repetitive, Short-Term Thermal Aging of Polyvinyl Chloride (PVC) Cable Insulation.

The effect of short-term (3- and 6-h-long) periodic thermal aging was investigated at three different temperatures on PVC cables and PVC films. Three different temperatures (110, 125, and 140 °C) were used for aging PVC cables and one (110 °C) for PVC films. PVC films were prepared for the investigation containing 0, 30, 40, and 50 weight percent of dioctyl phthalate plasticizer (DOP). The effect of short-term thermal aging was monitored by electrical (dielectric spectrum and voltage response measurement) and mechanical (Shore D hardness) methods. From the loss factor measurements, different deducted quantities were calculated and compared with Shore D hardness, which has been shown to be a parameter reflecting the effect of short-term thermal aging on PVC insulation. The measurements revealed that Shore D hardness is not the best property for monitoring aging. Instead, increasing dissipated power and the shifting behavior of tan δ–frequency curves proved to be the best phenomena for assessing the impact of thermal aging. Simple deducted quantities may provide a basis for following short-term thermal aging.

Dielectric loss and extended voltage response measurements for low-voltage power cables used in nuclear power plant: potential methods for aging detection due to thermal stress

This paper discusses the effect of thermal stress on the electrical properties, conduction and polarization, of low-voltage CSPE/XLPE-based power cables used in a nuclear power plant. The cables were subjected to an accelerated thermal stress at 120°C for an equivalent service period of 20, 40, 60 and 80 years. The capacitance, tanδ, resistivity at different frequencies and extended voltage response were the methods used for the investigation. A significant variation in the values of tanδ at low frequency, i.e., at 100 Hz, was observed. For the extended voltage response measurement, the decay voltage slope increased, showing the increase in the conduction particles inside the insulation material. While the decrease in return voltage slope showed that the slow polarization processes occurring at very low frequencies were decreased with aging. A strong correlation between the tanδ and decay voltage slope was also observed, which increased as the insulation aging increased. The results showed that the methods could be used for the in situ measurement of conduction and polarization phenomenon in the low-voltage cables, and hence helping in the assessment of the condition of cable insulation.

Combination of voltage response method with non-contact electrostatic voltage measurement to determine the dielectric response of insulating materials

The paper introduces the development of a new voltage response measurement method to determine the dielectric response function of insulating materials. This new method is based on a non-contact electrostatic voltage follower. In this technique, the voltage of the measuring probe follows the surface potential. The probe voltage is connected to the guarding electrode and helps to increase the impedance of the equipment. The paper introduces the built-up of the equipment and the relationship between the slopes of decay and return voltages and the dielectric response function.

High Responsivity Mg<italic>x</italic>Zn1–<italic>x</italic>O Based Ultraviolet Photodetector Fabricated by Dual Ion Beam Sputtering

Mg x Zn1– x O ( $x = 0.05$ , 0.15 and 0.20) based metal–semiconductor–metal ultraviolet (UV) photodetectors were fabricated on Si substrate using dual-ion-beam sputtering. The performances of fabricated photodetectors were studied by current–voltage, spectral photoresponse, and temporal response measurements. The values of peak responsivity of photodetectors were 0.4, 0.31, and 0.27 A/W with corresponding external quantum efficiency of 146%, 110%, and 105% for $x = 0.05$ , 0.15 and 0.20, respectively. The cutoff wavelength and UV/visible rejection ratio of fabricated photodetectors decrease over 360–330 nm and 341.8–115.3, respectively, with increase in Mg concentration. The variation in specific detectivity and noise equivalent power with Mg concentration variation is also reported.

Distribution of Te Inclusions in CdMnTe Crystal Grown by Traveling Heater Method

This study investigated Te inclusions in CdMnTe crystals grown by the traveling heater method (THM). Three CdMnTe ingots were grown under different growth temperatures of 850°C, 900°C, and 950°C by the THM method. In the CdMnTe ingots, the concentration of Te inclusion was lower in the middle-to-deposit part, and the size of Te inclusions kept growing till the last-to-deposit part. The concentrations of Te inclusions along the CdMnTe ingots were in the range of 104–106 cm−3, with the size in the range of 3–16 μm. CdMnTe crystals grown under 900°C had the lowest density and size of Te inclusion, due to the smooth and near-planar growth interface as revealed by infrared (IR) transmission microscopy. The relationship between the origin of Te inclusions and growth interface was analyzed during the THM growth of CdMnTe. IR transmission spectrometry was used to characterize Te inclusions in CdMnTe crystals. Current–voltage (I–V) and energy response measurements were carried out to reveal the resistivity (ρ) and energy resolution of CdMnTe detectors. The effects of Te inclusions on the optical and electrical properties of CdMnTe crystals for nuclear detector applications are discussed.

Effect of Stoichiometry on the Lifetime and Doping Concentration of Polycrystalline CdTe

The effect of gas phase Cd/Te deposition ratio on the minority carrier lifetime and doping concentration of polycrystalline cadmium telluride (CdTe) was investigated. CdTe thin films were deposited by the elemental vapor transport (EVT) with various Cd/Te gas phase ratios. The films were fabricated into solar cells, and characterized by current–voltage ( JV ) and spectral response measurements. The minority carrier lifetime was measured using time-resolved photoluminescence measurements. Capacitance–voltage ( CV ) measurements indicated a change in doping concentration as a function of gas phase Cd/Te ratio. Films deposited under Te-rich deposition conditions exhibited superior electrical characteristics. Minority carrier lifetimes up to 7 ns and doping concentrations on the order of 1015 cm–3 were measured for CdCl2 heat-treated Te-rich deposited films. The addition of controlled amounts of Cu increased the doping concentration up to 1016 cm–3, however lowered the carrier lifetimes to less than 1 ns. EVT deposited CdTe solar cells exhibited $V_{{\rm{OC}}}$ of 800 mV without Cu and up to 850 mV with Cu doping.

Electrodeposited Cu2O homojunction solar cells: Fabrication of a cell of high short circuit photocurrent

A Cu2O homojunction solar cell was fabricated using a consecutive electrodeposition method of deposition of an n-Cu2O film followed by a p-Cu2O film, in two different acetate baths. Both n-type and p-type film growth conditions were optimized separately to yield high photocurrents in a photoelctrochemical (PEC) cell. Further, the resulted bi-layer films were investigated in the PEC for the verification of the formation of the p-n homojunction. In addition, p-Cu2O film surfaces of the bi-layers were sulphided using Na2S and (NH4)2S in order to improve the photoresponse of the homojunction before depositing a Au film for the solar cell device. The structural, morphological and optoelectronic properties of the Cu2O films were investigated using X-ray diffraction (XRD), scanning electron micrographs (SEMs), dark and light current–voltage (I-V) and spectral response measurements and observed that the films are of good quality. Incident photon to current efficiency (IPCE) and I-V characteristics of the solar cell device demonstrated that the Cu2O homojunction can produce a high short circuit current density Jsc. However, the overall conversion efficiency of the device is low due to poor fill factor and Voc. The solar cell characteristics of the structure Ti/n-Cu2O/p-Cu2O/Au were Voc=287.0±0.1mV, Jsc=12.4±0. 1mA/cm2, FF=25±2% and η=0.89±0.02%, under AM 1.5 illumination. The record high Jsc value of the device demonstrates the prospect being improved the efficiency of Cu2O homojunction solar cells by optimizing deposition, pretreatment and post treatment processes.

Anion Effects on the Ion Exchange Process and the Deformation Property of Ionic Polymer Metal Composite Actuators.

An ionic polymer-metal composite (IPMC) actuator composed of a thin perfluorinated ionomer membrane with electrodes plated on both surfaces undergoes a large bending motion when a low electric field is applied across its thickness. Such actuators are soft, lightweight, and able to operate in solutions and thus show promise with regard to a wide range of applications, including MEMS sensors, artificial muscles, biomimetic systems, and medical devices. However, the variations induced by changing the type of anion on the device deformation properties are not well understood; therefore, the present study investigated the effects of different anions on the ion exchange process and the deformation behavior of IPMC actuators with palladium electrodes. Ion exchange was carried out in solutions incorporating various anions and the actuator tip displacement in deionized water was subsequently measured while applying a step voltage. In the step voltage response measurements, larger anions such as nitrate or sulfate led to a more pronounced tip displacement compared to that obtained with smaller anions such as hydroxide or chloride. In AC impedance measurements, larger anions generated greater ion conductivity and a larger double-layer capacitance at the cathode. Based on these mechanical and electrochemical measurements, it is concluded that the presence of larger anions in the ion exchange solution induces a greater degree of double-layer capacitance at the cathode and results in enhanced tip deformation of the IPMC actuators.

Influence of annealing temperature on morphological, optical and UV detection properties of ZnO nanowires grown by chemical bath deposition

Chemical solution deposition is a low-temperature method with possibly the lowest-cost for growing zinc oxide (ZnO) nanowires (NWs) on an amorphous glass substrate. A ZnO seed layer is needed to initialize the uniform growth of oriented nanowires. In the present work, we deposited the seed layer onto the glass substrate using radio frequency magnetron sputtering system. The ZnO NWs were fabricated on the seeded substrate by immersing them in a chemical bath containing zinc nitrate and hexamethylenetetramine (HTMA) aqueous solution. Several properties of as-grown ZnO NWs and annealed ZnO NWs at different temperatures in pure oxygen atmosphere were investigated. Well-defined ZnO nanowires almost perpendicular to substrate surface were observed through field emission scanning electron microscopy micrographs. X-ray diffraction measurements showed that all ZnO samples possessed a typical wurtzite structure with high crystallinity and no other impurity phases. The results of UV–Visible spectroscopy and room temperature photoluminescence implied that increasing the annealing temperature could have a significant influence on the performance of samples. The ZnO-based interdigitated metal–semiconductor–metal (MSM) was produced using the thermal evaporation of silver contacts. The results of current–voltage and transient response measurements demonstrate that despite using the low-cost thin film techniques, high responsivity was obtained.

Influence of Ambient Humidity on the Voltage Response of Ionic Polymer-Metal Composite Sensor.

Electrical potential based on ion migration exists not only in natural systems but also in ionic polymer materials. In order to investigate the influence of ambient humidity on voltage response, classical Au-Nafion IPMC was chosen as the reference sample. Voltage response under a bending deformation was measured in two ways: first, continuous measurement of voltage response in the process of absorption and desorption of water to study the tendency of voltage variation at all water states; second, measurements at multiple fixed ambient humidity levels to characterize the process of voltage response quantitatively. Ambient humidity influences the voltage response mainly by varying water content in ionic polymer. Under a step bending, the amplitude of initial voltage peak first increases and then decreases as the ambient humidity and the inherent water content decrease. This tendency is explained semiquantitatively by mass storage capacity related to the stretchable state of the Nafion polymer network. Following the initial peak, the voltage shows a slow decay to a steady state, which is first characterized in this paper. The relative voltage decay during the steady state always decreases as the ambient humidity is lowered. It is ascribed to progressive increase of the ratio between the water molecules in the cation hydration shell to the free water. Under sinusoidal mechanical bending excitation in the range of 0.1-10 Hz, the voltage magnitude increases with frequency at high ambient humidity but decreases with frequency at low ambient humidity. The relationship is mainly controlled by the voltage decay effect and the response speed.

Characterization of dielectric materials by the extension of voltage response method

The voltage response method measures the decay and return voltages on a charged and shorted dielectric and from the slopes of these voltages the specific conductivity and the polarization conductivity of the material can be determined. These two numbers can characterize the main dielectric processes, namely the conductivity and the polarization, however the phenomenon of polarization is the sum of numerous elementary polarization processes with different intensities and time constants. By changing the shorting time of a charged insulation the elementary polarization processes can be examined separately and the whole polarization spectrum can be investigated more precisely. This paper introduces how the voltage response measurement technique is extended by the variation of discharging times and the mathematical model of the measurement is described. Measurements on a model dielectric and on a dielectric material were carried out and the results have been compared by the results of the calculations.

Pioneering Application of Corona Charge-Kelvin Probe Metrology to Noncontact Characterization of In0.53 Ga0.47 As/Al2O3/HfO2 Stack

ABSTRACTWe report the first successful application of corona charging noncontact C-V and I-V metrology to interface and dielectric characterization of high-k/III-V structures. The metrology, which has been commonly used in Si IC manufacturing, uses incremental corona charge dosing, ΔQC, on the dielectric surface, and the measurement of surface voltage response, ΔVS, using a Kelvin-probe. Its application to In0.53Ga0.47As with a high-k stack required modifications related to the effects of dielectric trap induced voltage transients. The developed Corona Charge-Kelvin Probe Metrology adopted strictly differential measurements using ΔQC and ΔV, and corresponding differential capacitance rather than measurements based on total global charge, Q, and voltage, V, values.Electrical characterization data including interface trap density, electrical oxide thickness, and dielectric leakage are presented for a sample containing an In0.53 Ga0.47 As channel overlaid with a bilayer (2nm Al2O3/5nm HfO2) dielectric stack that is considered to be very promising for application in performance NFETs with high-mobility channels.

Investigation of temperature dependence of dielectric processes in thermally aged PVC insulation

Abstract The temperature dependence of dielectric processes was investigated of PVC cable insulation. For the investigation voltage response measurement was used, since this method ensures the independent investigation of conductive and polarisation processes. From the results of the measurement activation energies have been calculated to conductivity and polarisation conductivity of the material, the results are in 105.4 kJ/mol…133.8 kJ/mol and 32.1 kJ/mol…51.8 kJ/mol ranges, respectively. These results suggest that different charge carrier distribution mechanisms act main role in dc conductivity and slow polarisation processes in PVC cable insulating material.

Characterization of novel sprayed Zn 1− xMg xO films for photovoltaic application

Thin films of Zn 1− x Mg x O have been deposited using the chemical spray pyrolysis method. The variations in the chemical and physical properties of Zn 1− x Mg x O layers deposited with Mg-compositions in the range, 0≤ x≤0.3, were investigated with respect to the deposition conditions. The Zn 0.76Mg 0.24O layers were used as buffer layers in thin film solar cells with the configuration, glass/Mo/CuIn 0.8Ga 0.2Se 2/Zn 0.76Mg 0.24O/ZnO:Ga/Cu–Au using sprayed p-CuIn 0.8Ga 0.2Se 2 (CIGS) as an absorber layer and sprayed n-ZnO:Ga as a window layer. The devices were characterized using current–voltage, capacitance–voltage and spectral response measurements. The best devices had a solar conversion efficiency of 3.9% with quantum efficiencies >70%. This is the first time such a device has been made in which all the layers were produced using spray pyrolysis.

Comparative study of Cu(In,Ga)Se 2/(PVD)In 2S 3 and Cu(In,Ga)Se 2/(CBD)CdS heterojunction based solar cells by admittance spectroscopy, current–voltage and spectral response measurements

Co-evaporated Cu(In,Ga)Se 2 (CIGSe) based solar cells with Physical Vapour Deposited (PVD) Indium Sulphide (In 2S 3) as buffer layer have been studied by admittance spectroscopy and current-voltage characteristics measurements. The results have been compared to those obtained with a reference CBD-CdS/CIGSe device. In darkness, the PVD-In 2S 3 buffer layer devices exhibit higher densities of trapping defects and low values of shunt resistance. However, under illumination we have observed an important improvement of the In 2S 3/CIGSe electronic transport properties. This behavior seems to be linked to the presence of a metastable defect with activation energy of 0.3 eV.