Spark Lengths Research Articles

Calculation of Influence on Discharge Current Peaks for Human Air Discharges of Spark Lengths and Breakdown Potential Gradients using Simplified Equivalent Circuit based on IEC Standard

Calculation of Influence on Discharge Current Peaks for Human Air Discharges of Spark Lengths and Breakdown Potential Gradients using Simplified Equivalent Circuit based on IEC Standard

A Specific Relationship between Spark Lengths and Discharge Current Peaks via Ambient Temperature and Absolute Humidity for Air Discharges from Electrostatic Discharge Generator

A Specific Relationship between Spark Lengths and Discharge Current Peaks via Ambient Temperature and Absolute Humidity for Air Discharges from Electrostatic Discharge Generator

ESD Spark Behavior and Modeling for Geometries Having Spark Lengths Greater Than the Value Predicted by Paschen's Law

The insulation of plastic enclosures provides protection against direct electrostatic discharge (ESD) discharges to the system inside. However, seams between plastic parts are often unavoidable. To increase the voltage at which an ESD will penetrate the structure of the seam can be modified. Four plastic arrangements are constructed to investigate the spark length and current derivatives and to understand the ESD spark behavior for geometries having spark lengths longer than the values predicted by Paschen's law. A two to threefold increase of spark lengths was found for sparks guided by plastic surfaces compared to spark length expected from the Paschen value at the same voltage level. In spite of the longer path, a faster spark development is observed for sparks along the plastic surface. Plastic arrangements that provide detour and fold-back paths hardly reduced the total spark length. No significant effects of the plastic materials or the polarity were observed. The spark length increased as the (absolute humidity) Absolute humidity (AH) increased, and the current derivative decreased by about 20% as the spark length increased with (relative humidity) Relative humidity (RH) changing from 9% to 65% at 29 °C. The spark resistance is modeled by a modified Rompe and Weizel's law, which distinguishes the spark development in the air and along the plastic surface.

Waveform Comparison and Difference Factors in Discharge Currents for Air Discharges from Different ESD Generators

SUMMARYElectrostatic discharge (ESD) generators must be calibrated for contact discharges with the current waveform specified in International Electro‐technical Commission (IEC)61000‐4‐2; however, there are no requirements in current waveforms due to their bad reproducibility for air discharges in the IEC standard. Nevertheless, the air discharge immunity testing is under obligation in the present standard. This implies that different ESD generators are likely to provide significantly different test results for air discharge testing. In this study, two types of different ESD generators were used to measure discharge currents both for contact and air discharges with respect to charge voltages from 2 kV to 8 kV under the same conditions of experimental environment. As a result, we confirmed that the measured waveforms were almost identical for contact discharges regardless of charge voltages, while we found that they are quite different for air discharges with the same approaching speed when the charge voltages are increased. The latter result is because the generator has different impedance characteristics deriving from its structure, and because the spark lengths from the generators with the same charge voltage are different. A formula for calculating the discharge current from an ESD generator through an ideal switch in lieu of a spark, which was previously derived by us, was also employed to obtain the current waveform peculiar to the generator, in order to reveal that the formula provides the different upper limit of air discharge current peaks according to the generator.

Hybrid full‐wave/circuit modelling of spark gaps and its experimental validation

A hybrid full-wave and circuit model for spark gaps was constructed. The spark channel was modelled as a non-linear time-dependent resistor based on Rompe–Weizel's spark formula in SPICE. The linear full-wave model of an air gap and other structures were simulated by the semi-implicit finite-difference time-domain scheme based on the Newmark-beta method. These two models were coupled and simultaneously solved in time domain. The coupled model was tested for different charged voltages and spark lengths, and also validated in comparison with measurements.

異なるESD試験器の気中放電に対する放電電流の波形比較と相違要因

Electrostatic discharge (ESD) generators must be calibrated for contact discharges with the current waveform specified in IEC61000-4-2; however, there are no requirements in current waveforms due to their bad reproducibility for air discharges in the IEC standard. Nevertheless, the air-discharge immunity testing is under obligation in the present standard. This implies that different ESD generators are likely to provide significantly different test results for air discharge testing. In this study, two types of different ESD generators were used to measure discharge currents both for contact and air discharges with respect to charge voltages from 2 kV to 8 kV under the same conditions of experimental environment. As a result, we confirmed that the measured waveforms were almost identical for contact discharges regardless of charge voltages, while we found that they are quite different for air discharges with the same approaching speed when the charge voltages are increased. The latter result is because the generator has different impedance characteristics deriving from its structure, and because the spark lengths from the generators with the same charge voltage are different. A formula for calculating the discharge current from an ESD generator through an ideal switch in lieu of a spark, which was previously derived by us, was also employed to obtain the current waveform peculiar to the generator, in order to reveal that the formula provides the different upper limit of air discharge current peaks according to the generator.

Effect of Charged Sphere Size on Electrostatic Discharge Generated While Approaching a Stationary Object

SUMMARYThis study experimentally clarified that changing the size of a charged object affects the characteristics of the electrostatic discharge (ESD) that occurs when a charged object moves toward a stationary, grounded object. The spark lengths and discharge currents were measured as charged, metallic, spherical electrodes of different diameters approached a stationary grounded object at different speeds. The charge voltages of the dc high‐voltage power supply were +4.0 kV and +6.5 kV. According to the results, the average spark length tended to shorten with the speed of the spherical electrodes. The change in the average spark length with the speed of the 5.0‐mm‐diameter spherical electrode was faster than that for the 15.9‐mm‐diameter spherical electrode. The average peak value of the first peak of the discharge current for the 5.0‐mm‐diameter spherical electrode was greater than the average value for the 15.9‐mm‐diameter spherical electrode when the approach speed was greater than 5 mm/s for both spherical electrodes. The peak value, rise time, and rising speed of the first peak of the discharge current also correlate with the spark length, and the correlation can be explained qualitatively an the empirical equation deduced from the resistance formula proposed by Rompe and Weizel.

Effect of Moving Speed of Charged Metallic Spherical Electrode on Electrostatic Discharge

SUMMARYIn this investigation, the nature of the electrostatic discharge (ESD) that occurs when a charged object moves toward a stationary grounded object is experimentally clarified. The spark lengths, discharge currents, and induced voltages in a magnetic probe were measured when a charged metallic spherical electrode connected to a 422 pF capacitor approached a stationary grounded object, which was the current target, for different moving speeds of the charged metallic spherical electrode in a range of 1 mm/s to 100 mm/s. The charge voltages of the capacitor were +6.5 kV and +10 kV. Based on the results, the average gap length shortened with the speed of the spherical electrode. The average peak values of the discharge current and the induced voltage were likely to increase with the speed of the spherical electrode. The average rise times of the discharge current and the induced voltage were likely to drop with the speed of the spherical electrode. The relation between the spark length and the discharge current due to the ESD can be explained qualitatively by using an equation derived from the spark resistance formula proposed by Rompe and Weizel.

Effect of Charged Sphere Size on Electrostatic Discharge Generated while Approaching a Stationary Object

SUMMARY This study experimentally clarified that changing the size of a charged object affects the characteristics of the electrostatic discharge (ESD) that occurs when a charged object moves toward a stationary, grounded object. The spark lengths and discharge currents were measured as charged, metallic, spherical electrodes of different diameters approached a stationary grounded object at different speeds. The charge voltages of the dc high-voltage power supply were +4.0 kV and +6.5 kV. According to the results, the average spark length tended to shorten with the speed of the spherical electrodes. The change in the average spark length with the speed of the 5.0-mm-diameter spherical electrode was faster than that for the 15.9-mm-diameter spherical electrode. The average peak value of the first peak of the discharge current for the 5.0-mm-diameter spherical electrode was greater than the average value for the 15.9-mm-diameter spherical electrode when the approach speed was greater than 5 mm/s for both spherical electrodes. The peak value, rise time, and rising speed of the first peak of the discharge current also correlate with the spark length, and the correlation can be explained qualitatively an the empirical equation deduced from the resistance formula proposed by Rompe and Weizel.

Effect of Moving Speed of Charged Metallic Spherical Electrode on Electrostatic Discharge

In this study, I experimentally clarified the nature of the characteristics of the electrostatic discharge (ESD) that occurs when a charged object moves toward a stationary grounded object. The spark lengths, discharge currents, and induced voltages in a magnetic probe were measured when a charged metallic spherical electrode connected to a 422 pF capacitor approached a stationary grounded object, which was the current target, for different moving speeds of the charged metallic spherical electrode in the range of 1-100 mm/s. The charge voltages of the capacitor were +6.5 kV and +10 kV. According to the result, the average gap length shortened with the moving speed of the spherical electrode. The average peak values of the discharge current and the induced voltage were likely to increase with the moving speed of the spherical electrode. The average rise times of the discharge current and the induced voltage were likely to reduce with the moving speed of the spherical electrode. The relation between the spark length and the discharge current due to ESD can be explained qualitatively by using an equation derived from the spark resistance formula proposed by Rompe and Weizel.

Statistical analysis of electrostatic spark ignition of lean H2/O2/Ar mixtures

The concept of minimum ignition energy (MIE) has traditionally formed the basis for studying ignition hazards of fuels. However, the viewpoint of ignition as a statistical phenomenon appears to be more consistent with the inherent variability in engineering test data. We have developed a very low-energy capacitive spark ignition system to produce short sparks with fixed lengths of 1–2 mm, and the ignition system is used to perform spark ignition tests using a range of spark energies in lean hydrogen–oxygen–argon test mixtures used in aviation safety testing. The test results are analyzed using statistical tools to obtain probability distributions for ignition versus spark energy. A second low-energy spark ignition system was also developed to generate longer sparks with varying lengths up to 10 mm. A second set of ignition tests is performed in one of the test mixtures using a range of spark energies and spark lengths. The results are analyzed to obtain a probability distribution for ignition versus the spark energy per unit spark length. Preliminary results show that a single threshold MIE value does not exist, but rather that ignition is statistical in nature and highly dependent on mixture composition and spark length.

Correlation investigation between contact approach speed of handheld metal rod and discharge parameters from charged human body

Characteristic measurement of contact discharge currents are made through a hand-held metal rod from charged human body. Correlation coefficients are obtained, through Statistic Package for Social Science (SPSS), for various charge voltages, which is based on the effect test of electrode contact approach speeds on discharge current parameters of current peaks, maximum rising slope and spark lengths. Discharge parameters at charge voltage 300V are independent on approach speed. For charge voltages equal to and higher than 500V, the contact approach speed has strong positive correlation with discharge parameters of the peak current and the maximum rising slope, whereas has strong negative correlation with the spark length.

Small scale laser-triggered electrical discharges and their application to characterization of plasma channel induced by light filaments

Since the first demonstration of laser-induced electrical discharge [1] control of laser-triggered lightning discharges for lightning protection has became a long pursued task holding a great potential for practical applications [2–4]. Instead of high-energy continuouswave lasers such as CO2, emitting in the far infrared, the ultrashort pulse lasers with much shorter wavelengths (from near-infrared to ultraviolet) have been proven to be more advantageous offering a possibility to obtain continuous long ionized channels from the light filaments [5, 6]. It is well known that when a femtosecond laser pulse with power above the critical power for self-focusing propagates in the atmosphere, it forms a long white-light filament, which ionizes the molecules of air [7]. This ionized trail (narrow plasma channel) has been considered to be useful for triggering and guiding the electrical discharges [8]. A number of laboratory experiments had proven the validity of this approach [9–13], and guided megavolt discharges with spark lengths up to 3.8 m [14] were reported to date. Physical processes underlying a laser-triggered discharge are basically understood [12, 15]. A simple explanation is that the light filament by means of multiphoton ionization produces a short-lived (in the range of nanoseconds [16]) conducting plasma channel [17, 18] that serves as a precursor for discharge. In long gaps free electrons are then accelerated by the external electric field and start a local avalanche process – the ionization wave, called streamer. The avalanche zone expands towards the direction of the opposite electrode developing a self-sustained conducting path (leader). Once a contact between the electrodes is established, an electrical discharge occurs. However, plasma filament cannot trigger an electrical discharge by itself because of its short lifetime, and the electrical discharge (or breakdown) appears after a certain delay (ranging from nanosecond to microsecond time scale) with respect to the optical pulse. As follows from the model, the buildup time for electrical discharge is governed by transient processes (electron drift velocity and avalanche ionization [6]) to provide the critical electron density for a conducting channel. Somewhat different scenario is proposed for discharges in small gaps, assuming a constant electron density produced by the laser pulse. The current circulating in the laser-induced plasma channel produces significant heating of a thin air column by the Joule effect, which in turn is followed by radial expansion of the heated volume, and air depression meets the conditions providing a path for a guided discharge [13]. The number of free electrons in air under atmospheric pressure in normal conditions is usually very low (estimated to be less than 10 cm [19]) as compared with the atmospheric molecular density of 3·10 cm, therefore, if external electric field is applied, build-up time for a spontaneous discharge is long and typically requires a strength of external electric

The Effect of Geologic Inequalities on the Path of Lightning, as Indicated by Model Experiments

To investigate the influence of lightning strokes on surfaces with geologically non-homogenous structures, experiments were carried out in a model test tank filled with dried sand; and in this a vein of iron ore or other materials. Artificial lightning discharges against the surface of the test tank were undertaken by the aid of an impulse generator at voltages of one million volts and spark lengths of 75 and 170 cm respectively. It was found-that a discharge from a positive electrode was pronouncedly influenced by a geological discontinuity as an iron ore vein. On the other hand, negative strokes hit the sand surface at random more independent of geological discontinuities. The difference in effects from the two polarities is related to the mechanism of the discharges and the development of leaders initiating the main discharges in the form of lightning ones. DOI: 10.1111/j.2153-3490.1949.tb01268.x

The Mechanism of the Electric Spark

Meek's criterion for the formation of a spark discharge in a gas is criticized. An error in the derivation of his formula for the radial field about an electron avalanche channel is noted, and the value adopted for this field is shown to be too small to draw the postulated number of electrons into the channel from the space outside. The importance attached to the radial field is found to be misplaced because of the above and because a criterion based solely on the total number of ions produced in an avalanche gives results for sparking potentials for different spark lengths and for a gas at different pressures in agreement with those obtained by Meek's method. Both methods give results which, using the values assigned to the constants, fall more and more below the experimental values of the sparking potentials as the length of the spark gap, δ, is increased until at 20 cm the deviation is over 7 percent. To bring the computed value for δ=20 cm into agreement with the experimental value the constants in the equations would have to be increased by a factor 2×1016 over the values which give agreement between formulas and experiment for δ=1 cm. The dominant exponential term in each formula is based on the incorrect assumption that the field is not affected by the space charges in the avalanche. That a large amount of ionization, postulated by Loeb and Meek, is produced by a high potential wave which travels through the channel as soon as the positive streamer reaches the cathode is questioned because the fields found in such waves are too small to produce ionization by electron collision in air at atmospheric pressure.

On the laws governing electric discharges in gases at low pressures

The experiments described in this paper were undertaken with the object of determining the potential difference required to produce discharge in a number of gases over a wide range of pressures, and especially of ascertaining if the law enunciated by Paschen was generally applicable, provided the electric field in which the discharge took place was uniform. The paper is divided into the following sections :— (1.) Introduction. (2.) Description of apparatus. (3.) Experiments in air. (4.) Experiments in hydrogen. (5.) Experiments in carbon dioxide. (6.) Spark potentials with different electrodes. (7.) Minimum spark potentials. (8.) Connection between spark lengths and spark potentials. (9.) Minimum spark potentials in different gases. (10.) Summary of results.