Electrothermal Breakdown Research Articles

Polymer insulation breakdown types analysis

The paper investigates the theory of electrical breakdown channel formation in polymeric dielectrics. The process of operating electrical networks is quite complex, since dielectric materials lose their insulating properties under the influence of electric field intensity, which causes the destruction of molecular bonds. This phenomenon is called dielectric breakdown, or a violation of its electrical strength and loss of dielectric properties, followed by the formation of a breakdown channel with high electrical conductivity. Additional factors, such as insulation cooling conditions, external mechanical stress, ultraviolet radiation, ambient temperature, air humidity, proximity to main roads where chemicals are periodically treated, the degree of contamination of the area, the presence of a fungal colony on the surface, accelerate the process of destruction of the insulating properties of the dielectric. The paper considers the classification of polymer insulation breakdown types according to the physical nature of their occurrence, such as electrical breakdown, electromechanical breakdown, and electrochemical breakdown. The study of these processes has a significant impact, because the process of diagnosing some types of breakdown with the naked eye is complicated due to the process occurring in the middle of the insulation and not causing damage to the entire insulation, unlike classical porcelain or glass. An example of such a process is an electrothermal breakdown. It is caused by a disturbance in the thermal equilibrium in the dielectric between the processes of heat generation and heat transfer. An increase in the temperature of the dielectric increases its electrical conductivity, leakage currents, and heat generated in the insulation. An increase in temperature increases the electrical conductivity of the dielectric, which also generates additional heat and creates an avalanche-like process of dielectric heating and subsequent breakdown.

Quantitative Theory for the Electrical Breakdown of High‐Temperature Dielectric Materials under High Temperature and Electric Field

AbstractThe electrothermal breakdown of high‐temperature dielectric materials has received increasing attention. However, the theoretical characterization of quantitative relationship between breakdown strength and temperature has been a challenge. Herein, a theory termed energy storage capacity has been developed to generate and understand the nature of this quantitative relationship. This theory defines a limit value of stored energy associated with the material breakdown, including electric energy and the equivalent heat energy. Then, a parameter‐free theoretical model of temperature‐dependent breakdown strength of materials is developed, which takes into account the effects of dielectric constant and melting point. This non‐fitting model, without the need to carry out any destructive experiments and data fitting, is validated with excellent agreement between the predicted and measured values of both polymers and ceramics, monolithic and multilayered polymer/ceramic composites. It is shown that the failure of large classes of substances, including ceramics and polymers under heat and electrical force or mechanical force can be accurately modeled using the concept of the temperature independent limit value of the stored energy. This should become the new insight and entry point for the development of quantitative characterization of temperature‐dependent physical and mechanical properties of materials.

Imaging of Electrothermal Filament Formation in a Mott Insulator

Resistive switching---the current- and voltage-induced change of electrical resistance---is at the core of memristive devices, which play an essential role in the emerging field of neuromorphic computing. This study is about resistive switching in a Mott insulator, which undergoes a thermally driven metal-to-insulator transition. Two distinct switching mechanisms are reported for such a system: electric-field-driven resistive switching and electrothermal resistive switching. The latter results from an instability caused by Joule heating. Here, we present the visualization of the reversible resistive switching in a planar $\mathrm{V}$${}_{2}$$\mathrm{O}$${}_{3}$ thin-film device using high-resolution wide-field microscopy in combination with electric transport measurements. We investigate the interaction of the electrothermal instability with the strain-induced spontaneous phase separation in the $\mathrm{V}$${}_{2}$$\mathrm{O}$${}_{3}$ thin film at the Mott transition. The photomicrographs show the formation of a narrow metallic filament with a minimum width $\ensuremath{\lesssim}500$ nm. Although the filament formation and the overall shape of the current-voltage characteristics (IVCs) are typical of an electrothermal breakdown, we also observe atypical effects such as oblique filaments, filament splitting, and hysteretic IVCs with sawtoothlike jumps at high currents in the low-resistance regime. We are able to reproduce the experimental results in a numerical model based on a two-dimensional resistor network. This model demonstrates that resistive switching in this case is indeed electrothermal and that the intrinsic heterogeneity is responsible for the atypical effects. This heterogeneity is strongly influenced by strain, thereby establishing a link between switching dynamics and structural properties.

Field test of in-situ conversion of coal

ABSTRACT This work studies the in-situ conversion technology of solid fossil fuels to liquid and gaseous products. The investigated approach consists of the pyrolysis of solid fuel within the temperature range of 500–700°C. Heating occurs due to the flow of current through the electrothermal breakdown channel. The electrical contact with the coal is implemented via electrodes located in the wells. These wells also function as extraction channels. The paper describes the process of testing the use of technology in an area of an open coal bed at the Bogatyr coal mine (Ekibastuz, Kazakhstan). The interelectrode distance in the experiment was 1 meter. The results have demonstrated the feasibility of this method and have provided data for extrapolating the parameters of a larger interelectrode distance. The values of energy consumption, dynamics of bed resistance, and the number of products obtained are provided in this paper.

Unified Mechanism for Graphene FET’s Electrothermal Breakdown and Its Implications on Safe Operating Limits

Unique electrothermal properties of graphene and the chemical nature of its degradation present a compelling set of conditions for the exploration of its breakdown at different time scales. In this work, we give a phenomenological description of graphene's electrical breakdown ranging from a nonequilibrium (transient) electrothermal state to far-equilibrium state while spanning a time scale from few nanoseconds to few minutes. The intricate roles of Pauli-blocked states, intraband heating, and mechanism of degradation in defining a safe operating area (SOA) have been explored. The time and field evolution of defects, resulting in defect-by-defect breakdown, have been studied using Raman spectroscopy. The unified mechanism of breakdown discussed here provides a basic understanding of reliability of graphene-based devices under high-current and/or high-field conditions as well as degradation due to its prolonged operation.

Electro-thermal breakdown measurement of 500 kV cross-linked polyethylene submarine cable insulation material and its lifetime model analysis

The first 500 kV AC cross-linked polyethylene (XLPE) cable in the world has been installed in China in 2019. The insulation performance of insulation material under the electro-thermal stress is the basis for its service life. At here, the AC breakdown voltage values and the breakdown time of the 500 kV AC XLPE submarine cable insulation material under the electro-thermal step stress was analyzed. The lifetime prediction accuracy of a new proposed model was compared to the classic FALLOU, SIMONI/RAMU and CRINE lifetime model. Results show that the AC breakdown strength and lifetime of the XLPE samples increase slowly at low temperatures (40–65°C) and decrease rapidly at high temperatures (65–85°C). The lifetime prediction error of the classic FALLOU, SIMONI/RAMU and CRINE models present that their fit goodness cannot meet the accuracy requirement. The new lifetime model using stepwise regression method could optimize the combination of variables, which considers the coupling effect of electrical and thermal stress. The evaluation error of the new proposed model is better than the FALLOU, SIMONI/RAMU and CRINE model, which is suitable for analyzing the lifetime of the AC 500 kV XLPE submarine cable insulation material.

Electrochemically driven degradation of chemical solution deposited ferroelectric thin-films in humid ambient

The ambient humidity significantly accelerates the degradation of lead zirconate titanate (PZT) films in microelectromechanical systems; the cause of such degradation is under debate. Here, it is shown that the degradation of chemical solution derived PZT thin-films in humid conditions is driven by the system's electrochemical activity toward water electrolysis. The layer stacks with Pt-based electrodes exhibited a faster degradation rate owing to their higher electrocatalytic activity compared to Au. A degradation model is proposed based on the electrolysis of liquid or gaseous H2O, involving the evolution of oxygen and hydrogen gas at the top and bottom electrodes. Degradation proceeds above the threshold voltage for a given electrode system and is driven by the evolution and pressure build-up of gaseous species at the PZT/electrode interfaces. The pressure build-up causes film cracking, delamination of the film and electrodes, electrothermal breakdown events, and eventually time-dependent dielectric breakdown. Significantly larger post-breakdown crater sizes in humid than in dry conditions suggests that larger cracks through which dielectric breakdown through humidified air can occur. Overall, these effects are shown to cause sample failure up to six orders of magnitude of time earlier than for operation in dry conditions. Thus, in order to improve the resilience of thin-film systems in humid conditions, it is imperative to protect the electrochemically active electrode components of the device.

INVESTIGATION OF EXPLOSION SAFETY OF DC POLYMER SURGE ARRESTERS 3.3 KV FOR TRACTION NETWORK OF RAILWAY TRANSPORT

In the testing laboratories of Ukraine, there is no high-voltage equipment of the necessary energy for testing surge arresters for explosion safety, which does not allow to estimate this indicator at the stage of development of prototypes. In view of this test, the polymer prototypes of the DC surge arresters in polymer case (SAp) 3.3 kV were tested under the operating conditions of the equipment of the operating substation with short-circuit currents of 8.3 kA and a current time of 0.02 seconds, close to the recommended by Standard of IEC 60099-4:2014 values. 8 samples of surge arresters were tested. A sample of the surge arrester was mounted on one of the metal supports at a height of 5.5 m located in the substation and connected to the 3.3 kV traction substation buses through disconnectors and a high-speed switch. After the short-circuit breaker was closed through a column with a pre-punched or shunted copper wire varistor, a short-circuit current flowed to form an electric arc inside the arrester samples. During the tests video samples were recorded using a video recorder installed in close proximity to the test sample. The frame of the SAp samples in which the varistors were enclosed was performed either by winding the fiberglass tape on a varistor column, or from rods arranged in the form of a squirrel cage, or in the form of a fiberglass tube with a hole for gas ejection during a short circuit inside the SAp. The destruction of the hull occurred without scattering of the fragments in seven cases from the eight samples tested. In seven samples, a local rupture of the silicone shell occurred in the varistor zone, a gas ejection and an arc discharge occurred through this gap. The exception was sample No. 2, made by a continuous winding of a glass-banding tape on a varistor column, in which, during the explosion, the upper electrode exploded with the simultaneous expansion of fragments of the varistor in a radius of 3-5 m. Due to the white smoke accompanying the explosion, it was not possible to fix on the frame whether the arc output from the case to the outside, despite the fact that on the next frame (in 33 ms.) the arc was no longer fixed. In the tests of eight of the presented designs, none of them ignited the hull. If the tests were carried out on the surge arresters assembled with pre-punched varistors (electrothermal breakdown), the varistors during the tests split, remaining inside the frame. From the action of the arc in the contact zone of the aluminum electrodes with varistors, a deep burn-out of the electrodes was observed, in some cases, the burnup was up to 7 mm deep and up to 8 mm wide. If the varistors were shunted by a copper wire, they remained intact. If the varistors were shunted by a copper wire, they remained intact und melting and burning out a part of the aluminum electrodes in the area of connection with the copper wire were smaller sizes. The samples showed a completely satisfactory ability to withstand large pulse currents without dispersing dangerous fragments for personnel and surrounding equipment. However, polymer designs, the frame of which is made by continuous winding, require reinforcement of the connection zone of the carcass with electrodes to exclude the break-out of electrodes during the accumulation of gases during a short circuit inside the shell of the SAp. For such designs, an additional test for mechanical strength in the longitudinal direction with a predetermined norm is required in the acceptance test program.

Avalanche Breakdown Stability of High Voltage (1430 V) 4H-SiC p+–n0–n+ Diodes

The electrothermal breakdown in high-voltage (1430 V) 4H-SiC p+–n0–n+ diodes with an n0-base thickness of 7.5 μm, a donor concentration of 8.0 × 1015 cm–3, and 4.9 × 10–4 cm2 in area are studied. The stability of the diodes to avalanche breakdown is characterized by the maximum energy of a single avalanche current pulse that can be scattered by a diode until its catastrophic destruction. At a pulse duration of ~1 μs, the energy maximum is 1.4 mJ (2.9 J/cm2). It is shown that diode destruction is caused by local overheating of the diode structure to a temperature of ~1600 K at which the intrinsic carrier concentration becomes higher than the doping donor concentrations in the blocking n0-type base.

Phase‐Field Model of Electrothermal Breakdown in Flexible High‐Temperature Nanocomposites under Extreme Conditions

AbstractPolymer‐based dielectrics are attracting increasing attention due to their high‐density energy storage. However, mitigating the heat generation in real capacitors has been a challenge. Here an electrothermal breakdown phase‐field model is developed to fundamentally understand the thermal effects on the dielectric breakdown of polymer‐based dielectrics in real capacitor configurations including the increase in the dielectric loss and the decrease in the breakdown strength. While both enhancing the thermal conductivity and reducing the electrical conductivity of the polymer nanocomposites can reduce the thermal effects, it is found that reducing the electrical conductivity is more effective. This work is expected to not only stimulate attention to the thermal effects in polymer‐based dielectrics but also provide a fundamental guidance to mitigate the heat‐induced deterioration of breakdown strength.

Устойчивость высоковольтных (1430 В) 4H-SiC p-=SUP=-+-=/SUP=--n-=SUB=-0-=/SUB=--n-=SUP=-+-=/SUP=--диодов к лавинному пробою

AbstractThe electrothermal breakdown in high-voltage (1430 V) 4 H -SiC p ^+– n _0– n ^+ diodes with an n _0-base thickness of 7.5 μm, a donor concentration of 8.0 × 10^15 cm^–3, and 4.9 × 10^–4 cm^2 in area are studied. The stability of the diodes to avalanche breakdown is characterized by the maximum energy of a single avalanche current pulse that can be scattered by a diode until its catastrophic destruction. At a pulse duration of ~1 μs, the energy maximum is 1.4 mJ (2.9 J/cm^2). It is shown that diode destruction is caused by local overheating of the diode structure to a temperature of ~1600 K at which the intrinsic carrier concentration becomes higher than the doping donor concentrations in the blocking n _0-type base.

A Combined Electro-Thermal Breakdown Model for Oil-Impregnated Paper

The breakdown property of oil-impregnated paper is a key factor for converter transformer design and operation, but it is not well understood. In this paper, breakdown voltages of oil-impregnated paper were measured at different temperatures. The results showed that with the increase of temperature, electrical, electro-thermal and thermal breakdown occurred successively. An electro-thermal breakdown model was proposed based on the heat equilibrium and space charge transport, and negative differential mobility was introduced to the model. It was shown that carrier mobility determined whether it was electrical or thermal breakdown, and the model can effectively explain the temperature-dependent breakdown.

Simulation of electro-thermal ageing and breakdown in polymeric insulation under high frequency trapezoidal-wave pulses

A quantitative ageing model expressed in terms of two generic parameters, one describing the ability of local regions to resist degradation and the other describing their capacity to concentrate energy from the electric field, has been used to simulate the electro-thermal ageing of Polyethylene Terephthalate (PET) in pulsed trapezoidal-wave electric fields. Allowance has been made for the dielectric heating produced by the alternate-polarity voltage pulses. It was found that for 90% of the lifetime the degradation was that of isolated regions. Only when the regions started to group to produce a local field in excess of a critical value did the degradation accelerate to failure in the form of a single track. The critical field is associated with the effective onset of irreversibility in the production of degradation, such that a local equilibrium state in the presence of the field was no longer possible regardless of the nature of the surrounding material. The temperature increases were found to be small and had very little influence upon degradation formation, though they had a minor influence on the initiation of runaway failure.

Feasibility of a Gelatin Temperature Sensor Based on Electrical Capacitance.

The innovative use of gelatin as a temperature sensor based on capacitance was studied at a temperature range normally used for meat cooking (20–80 °C). Interdigital electrodes coated by gelatin solution and two sensors of different thicknesses (38 and 125 µm) were studied between 300 MHz and 900 MHz. At 38 µm, the capacitance was adequately measured, but for 125 µm the slope capacitance versus temperature curve decreased before 900 MHz due to the electrothermal breakdown between 60 °C and 80 °C. Thus, for 125 µm, the capacitance was studied applying 600 MHz. Sensitivity at 38 µm at 868 MHz (0.045 pF/°C) was lower than 125 µm at 600 MHz (0.14 pF/°C), influencing the results in the simulation (temperature range versus time) of meat cooking; at 125 µm, the sensitivity was greater, mainly during chilling steps. The potential of gelatin as a temperature sensor was demonstrated, and a balance between thickness and frequency should be considered to increase the sensitivity.

Stronger multilayer acrylic dielectric elastomer actuators with silicone gel coatings

Multilayer dielectric elastomer actuators (DEA) perform worst off than single-layer DEAs due to higher susceptibility to electro-thermal breakdown. This paper presents a hot-spot model to predict the electro-thermal breakdown field of DEAs and its dependence on thermal insulation. To inhibit the electrothermal breakdown, silicone gel coating was applied as barrier coating to multilayer acrylic DEA. The gel coating helps suppress the electro-thermally induced puncturing of DEA membrane at the hot spot. As a result, the gel-coated DEAs, in either a single layer or a multilayer stack, can produce 30% more isometric stress change as compared to those none-coated. These gel-coated acrylic DEAs show great potential to make stronger artificial muscles.

Inhibiting electro-thermal breakdown of acrylic dielectric elastomer actuators by dielectric gel coating

Electrical breakdown of dielectric elastomer actuators (DEA) is very localized; a spark and a pinhole (puncture) in dielectric ends up with short-circuit. This letter shows that prevention of electrothermal breakdown helps defer failure of DEAs even with conductive-grease electrodes. Dielectric gel encapsulation or coating (Dow Corning 3-4170) helps protect acrylic elastomer (VHB 4905), making it thermally more stable and delaying its thermal oxidation (burn) from 218 °C to 300 °C. Dielectric-gel-coated acrylic DEAs can withstand higher local leak-induced heating and thus achieve higher dielectric strengths than non-coated DEAs do.

Study on ESD Effects of GaAs HBT Power Amplifiers for DCS/GSM Dual Band Handsets

Study on electrostatic discharge (ESD) impact on the GaAs HBT power amplifier (PA) in DCS/GSM dual band handsets is performed in this paper, which has been regarded as its main reliability issue accounting for most failures of radio frequency integrated circuits. In order to suppress the positive ESD impact on the PA in an effective but very economic way, a set of forward ESD diodes at its input port is replaced by the PN junction of GaAs HBT transistor in its first-stage. Alternatively, to introduce a set of thin film resistors (TFRs) at the front of a HBT transistor is necessary for improving the S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> -parameter and stability of PA; however, their electrothermal breakdown possibilities do exist. Therefore, both performance degradation and breakdown events of several PA dies are measured for different ESD voltages described by the human body model, with different TFRs chosen for both DCS and GSM bands, respectively. Their transient temperature responses are also captured and compared for different ESD waveforms, which are predicted using the in-house developed algorithm based on the hybrid time-domain finite-element method.

Partial Discharges Characteristics in Oil Shale of Various Deposits

Attention to oil shale processing as unconventional energy source grows significantly. Electrical discharge phenomena application allows creating new efficient technology. Dynamics of PD basic characteristics of voltage in oil shale is described in this paper. Thermodestruction with abnormally high rate is occurred and caused by PD activity. Critical PD incept under low electrical intensity due to oil shale porosity, anisotropy and heterogeneity. PD induce treeing with following electrothermal breakdown. Organic content has influence on electrical discharges phenomena in oil shale. Therefore, the detailed study of PD, treeing and breakdown in oil shale allows developing an efficient method of inferior solid fossil fuels processing.

Experimental Investigation and Analysis of the LDMOS FET Breakdown Under HPM Pulses

In this paper, thermal breakdown effects in a laterally diffused MOS (LDMOS) FET under the impact of high-power microwave (HPM) pulses are investigated by theoretically analyzing, modeling, and measuring. Experimental investigations of the LDMOS FET-based power amplifier (PA) are performed under different pulse durations. The measurement system consists of an adjustable HPM source, one controller, couplers, limiters, attenuators, one four-channel oscilloscope, and a DUT. By increasing the input pulse power level, electrothermal breakdown is observed. The breakdown temperature is calculated by using a 2-D analytic model based on the measured power to failure data. Then, our developed time-domain finite-element numerical algorithm is used to characterize temperature distribution and transient performance of the LDMOS FET. The energy capability, which defines the maximum energy that the device can handle, is 15.5 mJ under the pulse duration of 1 ms with a breakdown temperature of 605 K.

Dielectric properties of polyamide-imide

The dielectric properties of poly(amide imide) (PAI) films are investigated in a large temperature range. A moisture-dependent relaxation (γ-relaxation between −100 °C and 20 °C) and a non-cooperative local dipole relaxation (β-relaxation between 40 °C and 200 °C) display an Arrhenius-type behaviour with an activation energy of 0.50 eV and 1.22 eV, respectively. In the near glass transition (Tg) region at 277 °C, a relaxation process (α-relaxation) occurs due to cooperative segmental motions of the chains and follows a non-linear Vogel–Fulcher–Tamman (VFT) temperature dependence with a strong fragility. Simultaneously in the same temperature range, both a conduction process (σ-conduction) and an electrode polarization phenomenon (ρ-relaxation) are also present. The σ-conduction also follows a VFT behaviour but it possesses a lower fragility in the above-Tg region. This discrepancy is assigned to a partial decoupling between ionic transport and segmental chain motions. The dielectric strength of PAI films exhibits a negative temperature dependence. The near-Tg region corresponds to a change from a thermal breakdown mechanism to an electromechanical breakdown due to the glass–liquid phase transition. Above Tg, the formation of a space-charge probably also involves an electro-thermal breakdown mechanism.