Sparkover Voltage Research Articles

The Testing Of High Voltage Silicon Carbide Lightning Arresters

The majority of high voltage gapped silicon carbide lightning arresters on transmission and sub transmission systems have been in service for over 10 years. A testing program is required that can accurately and efficiently determine the condition of these high voltage arresters. The essential theory of silicon carbide arresters was investigated, focusing particularly on arrester construction, performance and the unique characteristics of high voltage arresters. The effectiveness of available testing procedures was then evaluated and a set of tests selected, based on their expected performance, their ability to assess all facets of arrester behavior, the ease with which they could be completed in the available laboratory and their possible application to in-field testing. The testing program implemented consisted of a series of procedures including the lightning impulse sparkover voltage test, power frequency sparkover voltage test, power frequency withstand test, AC and DC leakage current measurements, 5 kV insulation resistance test, and finally a non-standard current impulse test. The tests were performed on a set of 6 arresters rated at 33 and 132 kV and a set of 5 arrester sections. The results of the investigation verified the effectiveness of the selected procedure with a consistent and accurate assessment of arrester condition obtained for all arresters under test. All arresters exhibited satisfactory performance in the selected tests, indicating that high voltage gapped silicon carbide arresters are more durable than those used on distribution systems.

Modeling the Transient Behavior of Surge Protective Devices Connected to the DC Side of Electric Vehicle Charging Stations

This work provides an electromagnetic transient model for low-voltage surge protective devices connected to the dc side of electric vehicle charging stations with a maximum operating voltage of 1000 V. An equivalent circuit model is developed based on standard impulse voltage (1.2/50 μs) and impulse current (8/20 μs and 10/350 μs) experiments. The proposed model reproduces quite accurately the response of the combination type surge protective device under study in terms of sparkover voltage, residual voltage, and energy absorption, as illustrated through ATP-EMTP simulations. The developed simulation model can be an effective tool for surge protection and insulation coordination studies for electric vehicle charging stations.

ANALISIA PENEMPATAN LIGHTNING ARRESTER PADA CABLE HEAD 60 SEBAGAI PENGAMAN TRANSFORMATOR GIS BANDARA NGURAH RAI

The transmission line of 150 kV between GIS (Gas Insulated Switchgear) Bandara Ngurah Rai and GI Nusa Dua needs to be concerned further due to the high number of VIP customers supplied by the GIS Bandara Ngurah Rai. The location of transmission line of GIS Bandara Ngurah Rai with GI Nusa Dua is also located in the southern area of Bali in which according to the data of BMKG in 2018, it was recorded that 15.000-30.000 lightning strike occurred in the southern area of Bali. One of the devices used to protect the equipment from lightning surge is lightning arrester. Lightning arrester which is used in the network of GIS Bandara Ngurah Rai to GI Nusa Dua is placed on Cable head 60. The transmission line of GIS Bandara Ngurah Rai with GI Nusa Dua is connected by an overhead line of 8.5 km and an underground cable of 2.02 km, which is connected by terminating on Cable head 60. The distance between the Airport GIS transformer and the lightning arrester is 2.02 km, therefore it needs to be studied further in order to find out whether the protection generated by the lightning arrester has been optimal or not. The result showed that the arrester with an installation distance of 2020 meters from the transformer is still able to cut the lightning surges by producing the sparkover voltage value of 605.12 kv. Accordingly, the result of sparkover voltage exceeds the sparkover voltage of the arrester in the number of 577kv, however the voltage is still within the tolerance range of the sparkover voltage of the arrester.

Optimal Design of a Follow Current Disconnector for DC Arresters in Traction Vehicles

This paper dealt with the optimal design of a follow current disconnector for DC arresters used in electric traction vehicles. The disconnector separates the ground lead from an arrester to prevent a line-to-ground fault of an aged arrester and should not affect the operation and function such as the reference and the clamping voltage of the connected arrester. The designed disconnector is composed of a resistor, a spark gap, and a cartridge. The results showed that the sparkover voltage increased with the gap distance whereas the reference voltage was almost the same as that without the disconnector. The sparkover voltage was 3.95 kV when the gap distance was 0.5 mm. Regardless of the gap distance, the reference and the clamping voltage of the assembled disconnector with an arrester were measured to be the same as those of the arrester alone.

A Study of the Dielectric Characteristics of Gaseous Nitrogen With Respect to the Electrode Material for Developing a High Voltage Superconducting Fault Current Limiter

The current lead for a high-voltage superconducting fault-current limiter is made of copper or brass, and the cryostat chamber is often composed of a nonmagnetic material, such as stainless steel. Therefore, sparkover breakdown may occur at the current lead or the superconducting coil of such a superconducting coil system. The measurement of sparkover and partial discharge inception voltages is considered an important technique for diagnosing the dielectric conditions of a high-voltage superconducting instrument. In this paper, the sparkover voltage and the partial discharge inception voltage with respect to the electrode material were examined under an alternating-current voltage. Sphere-to-plane electrode systems made of stainless steel, copper, brass, and iron were tested in dielectric experiments to verify the sparkover and partial discharge inception voltages. It is observed that the sparkover and partial discharge inception voltages in gaseous nitrogen (GN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) were strongly dependent on the electrode material. In addition, it is found that the sparkover and partial discharge inception characteristics of GN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> conform to the work function of the electrode material.

Dielectric Characteristics of Solid Insulation Materials With Respect to Surface Roughness

Three kinds of solid insulation materials, such as glass-fiber-reinforced plastic (GFRP), Bakelite, and MC Nylon, are often used in high-voltage superconducting apparatuses as formers and insulation barriers to improve dielectric characteristics. GFRP, Bakelite, and MC Nylon are considered promising candidates as cryogenic solid insulation materials for developing a high-voltage superconducting apparatus due to their excellent dielectric characteristics and robust mechanical strength under cryogenic conditions. The surface roughness of solid insulation materials could differently vary depending on the machining processes. These effects may result in reduced dielectric characteristics. Currently, the details of any relationship between surface roughness and dielectric characteristics under cryogenic conditions have not been analyzed, and there are only a few reports. Thus, a study of the dielectric characteristics of solid insulation materials with respect to surface roughness in cryogenic conditions should be conducted when designing high-voltage superconducting apparatuses with high reliability. In this paper, we present a study on the dielectric characteristics of several materials, such as GFRP, Bakelite, and MC Nylon, used as formers and insulation barriers as a function of surface roughness to assess the effects of changes in surface roughness. Experiments with respect to surface roughness were performed with alternating-current voltages in gaseous nitrogen (GN 2 ) and liquid nitrogen (LN 2 ). A barrier-type solid insulation material was installed between a rod-to-plane electrode system. Penetrating electrical breakdown, creep discharge, and sparkover voltage with a barrier system were observed in the experiments. It was found that the penetrating electrical breakdown, the creep discharge, and the sparkover voltage with a barrier were influenced by the surface roughness of the solid insulation barriers.

Spark Breakdown in Gas-Discharge-Tube Surge Arrester at Voltage Pulse

The sparkover voltage of gas discharge tubes for surge voltage protection has been found to be dependent on the rate of voltage rise. At slow voltage increase, it is close to stationary voltage conditions and is assumed to be the breakdown voltage at a given $pd$ regarding Paschen law. The deviation of stationary sparkover voltage measured on test samples is assigned to the variation of electrode conditions and illustrated as the effect of the Townsend coefficient $\gamma$ . The increase of impulse sparkover voltage at fast voltage rise depends on the time lag of the spark breakdown where the effect of statistical and formative time lag is assessed. As an origin of ion avalanche and streamer formation, the cold-field electron emission process is considered where the Poisson probability function for rare stochastic events is concerned for the evaluation of emitted electron current. Due to the absence of applicable values for relevant system parameters, the relationship between the impulse sparkover voltage and the rate of voltage rise obtained by simulation have more or less qualitative character. Values taken for the coefficients of simulation are chosen by fitting the simulated results to the measured ones. Their relevance is verified by comparing it with the typical values of discharge quantities found in the literature.

Qualitative gas temperature distribution in positive DC glow corona using spectral image processing in atmospheric air

An experimental method of determining a qualitative two-dimensional image of the gas temperature in stationary atmospheric nonthermal plasma by spectral image processing was presented. In the experiment, a steady-state glow corona discharge was generated by applying a positive DC voltage to a rod-plane electrode in synthetic air. The changes in the gas temperature distribution due to the amplitude of applied voltage and the ambient gas pressure were investigated. Spectral images of a positive DC glow corona were taken using a gated ICCD camera with ultranarrow band-pass filters, corresponding to the head and tail of a N2 second positive system band (0–2). The qualitative gas temperature was obtained from the emission intensity ratio between the head and tail of the N2 second positive system band (0–2). From the results, we confirmed that the gas temperature and its distribution of a positive DC glow corona increased with increasing applied voltage. In particular, just before the sparkover voltage, a distinctly high temperature region was formed in the positive DC glow at the tip of the rod electrode. In addition, the gas temperature decreased and its distribution spread diffusely with decreasing ambient gas pressure.

Influence of electrode configuration on the heat transfer performance of a LED heat source

In this study, the effects of electrode configuration on the cooling of LED are presented. A total of six needle type electrodes, including sharp, 0.08, 0.12, 0.37, 0.49R and flat tip, are used to generate ionic wind for cooling of the LED. The effects of electrode configuration, vertical separation height, and tilt angle on the cooling performance of a LED are reported in this study. It is found that the thermal resistance is reduced with the supplied voltage and a maximum 50% reduction is achieved before the spark-over voltage. For the same supplied voltage, the thermal resistance with a larger vertical separation is also higher. However, the operational range is also longer. The effect of tilt angle on the cooling performance of LED depends on the supplied voltage. With a supplied voltage being less than 6.5kV, it is found that the thermal resistance is increased when the tilt angle is reduced with a tip radius of 0.12R. However, the trend is reversed when the supplied voltage is higher than 6.5kV where the thermal resistance of a smaller tilt angle is lower than that of a larger tilt angle. For the same mesh ground, the effect of electrode configurations cast little influence on the final thermal resistance. All the electrodes show an approximately 50% reduction of thermal resistance in association with its original thermal resistance. However, the corresponding threshold voltage and operational voltage differs significantly. The threshold voltage is lowest for the sharp needle and is increased with the rise of tip radius. On the other hand, the corresponding operational range becomes narrower when the tip radius is increased. Yet the spark-over voltage is also insensitive to change of electrode configuration.

Discharge Characteristics and Suitability as Pragmatic Insulation Medium of CF&lt;sub&gt;3&lt;/sub&gt;I and its Mixture

CF3I gas is one of the alternatives for SF6 which has been applied for electric power equipment. CF3I has some merit against SF6. For example, its insulation performance is equivalent or superior to SF6 in uniform field and its Global Warming Potential (GWP) is quite low as same as CO2. On the other hand, it has low sparkover voltage in non-uniform field. This paper reviews the discharge characteristics of CF3I and CF3I/N2, CF3I/CO2 and CF3I/SF6 mixtures and tries to find the pragmatic gas as an insulation medium with a simple ranking method where saturated gas pressure and GWP are taken into account.

Choosing the appropriate Gas Discharge Tubes (GDT) for avionics lightning protection

GDTs are a very effective component to suppress high powered pulsed transients such as lightning. When designing per the datasheet, one would expect a component to operate within the specified ratings. This is not always the case. Some GDTs typically violate the impulse spark-over voltage rating. The authors have noticed a belief in the industry that this is normal for a GDT. GDTs can be found that do perform according to their ratings. The purpose of this article is to dispel any belief by the reader that unpredictability of a GDT's impulse spark-over voltage is just "part of designing with GDTs". However, you do have to test.

Corona Charge Injection Prior to Sparkover in an Inversed Rod-Plane Gap Under Composite Voltages

Research on the sparkover characteristics of long air gaps under composite voltages has important significance on the design and operation of transmission lines and equipment. In this paper, corona charge injection prior to sparkover in an inversed rod-plane gap under composite voltages was studied. The variation of charge injection to the initiation of leader and breakdown was measured by a capacitor divider. Two photomultipliers were positioned to study corona development at two positions between the tip of the rod and the plane, from which the light output could be compared with the charge injected into the gap. When a positive prestress voltage is employed at the plane, charge injection is enhanced and leader inception and breakdown occur at lower voltages than with prestress voltage of opposite polarity. The <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">U</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50%</sub> sparkover voltages are in inverse proportion to the charge and power inputs up to the time of the leader initiation. The results of corona charge injection to sparkover are helpful for understanding the physical process of the gap breakdown in depth.

Conceptual Design of Current Leads for 154 kV SFCLs

Study of the dielectric characteristics on gaseous insulation media is important for designing and developing current leads of superconducting machines with a sub-cooled cooling method. In the case of using a sub-cooled N2 cooling method, a gaseous insulation medium, such as He, Ne, SF6, CF4, or N2, should be injected to control the pressure and enhance the dielectric performance of current leads simultaneously. In this study, dielectric experiments on various gaseous insulation media are conducted and experimental results are analysed by considering field utilization factors. In addition, the functional equations are derived from experimental results and computational analyses. It is found that the dielectric characteristics of gaseous insulation media are determined by the maximum electric field intensity at sparkover voltage. This denotes that the electrical breakdown voltage of insulation gas could be estimated using deduced functional equations. Finally, the conceptual electrical insulation designs of current leads for a superconducting apparatus according to various insulation media are presented and the results are compared. The results may be applied to develop and commercialize a high voltage superconducting apparatus using a sub-cooled N2 cooling method.

Pressure Dependence of Breakdown Voltage Under Inhomogeneous Field in CF&lt;sub&gt;3&lt;/sub&gt;I Gas

CF3I gas is one of promising SF6 substitute. The insulation performances of CF3I, CF3I/N2, and CF3I/CO2 mixtures are examined through measuring sparkover voltage in inhomogeneous field under 0.1 to 0.5 MPa(abs)-gas pressure.

CF&lt;sub&gt;3&lt;/sub&gt;Iガスの放電による副生成物の発生と絶縁特性への影響

CF3I gas, which is one of promising SF6 substitutions, is investigated from the view point of by-product generated in gas discharge, since its global warming potential (GWP) is quite low and its insulation performance is equivalent or superior to SF6 gas. The insulation performance of CF3I gas is examined through measuring sparkover voltage in various electric fields and flashover voltage on the surface of insulating material together with analyzing by-products of CF3I gas. Gas chromatography analysis shows that C2F6, C2F4, CHF3, C3F8, C3F6, and C2F5I are generated by the sparkover and the flashover. The sparkover voltage after 1300 times sparkover in uniform electric field is decreased by 11%. The flashover voltage for a virgin insulator in CF3I gas is almost equal to that in SF6 gas. The flashover voltage in CF3I gas is, however, 0.6 times lower than that in SF6 gas, when the number of surface flashover is increased.

The Optimization of Entering Route for Live Working on 750 kV Transmission Towers by Space Electric-Field Analysis

Live working is important for the continuity of electricity supply in power system. Experiment results of 50% switching impulse sparkover voltages (U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50</sub> ) for different live working entering routes on a real tower are presented. The potential and electric-field distribution around the 750 kV straight tower window with a line worker inside, was analyzed via an approach combing charge simulation method and indirect boundary element method. The comparison demonstrates the close relationship between electric-field distribution and U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50</sub> . The sparkover voltage and the maximum electric-field strength change synchronously for a specific structure. Generally speaking, the higher the electric filed strength is, the lower the sparkover voltage will be. Thus, the experiment procedure for deciding the best entering route can be simplified according to the electric-field distribution calculation.

Specific Considerations on IEC Standardization of Externally Gapped Line Surge Arresters (EGLAs)

The application of externally gapped line surge arresters (EGLAs), which have been developed and established in Japan, is now expanding into many countries. Therefore, the maintenance team 4 (MT4) in the international electrotechnical commission (IEC) technical committee 37 (TC37) for surge arresters advances the standardization works to specify the minimum criteria for requirements and testing methods of EGLAs. EGLAs are effective lightning protection of overhead transmission lines, and have unique required performances originated from the external series gap. The unique required performances of EGLA are insulation coordination performance of EGLA sparkover voltage for lightning overvoltage with the insulator assembly to be protected, withstand voltage performance for switching surge overvoltage and TOV, and follow current interruption performance.This paper discusses the specific issues to be considered for the standardization, such as classification of lightning discharge current rating and a test procedure for follow current interruption performance, based on the Japanese technology through more than twenty years of experience with a large numbers of EGLAs in 22kV to 500kV systems.

Sparkover Characteristics in CF3I Gas and CF3I/N2 Gas Mixture under Non-uniform Field Gaps

A steep-front square pulse voltage generator, which has a rise time of 16ns, a dumping factor less than 2.5% after 10μs duration and a peak value of 200kV, is successfully used to survey the V-t characteristics in nanosecond range. The V-t characteristics of CF3I, SF6, CF3I/N2 and SF6/N2 gas mixtures under non-uniform field gaps by using the steep-front square pulse voltage. When the field utilization factor are measured less than 0.38, the sparkover voltage of CF3I is lower than that of SF6. On the contrary, when the field utilization factor is more than 0.38, the sparkover voltage of CF3I is higher than that of SF6. The corona inception voltage calculated by using Schumann's criteria and compared with measured one. The V-t characteristics for a uniform field gap in CF3I/N2 gas mixture containing N2 gas of 40% are equivalent to those in pure SF6 gas. The synergism for appears when CF3I gas is mixed with N2 gas.

Effects of a Charged Metallic Particle of Milli-size on DC Sparkover Voltages

Effects of a charged metallic particle of milli-size on sparkover characteristics under dc quasi-uniform gap of 2 cm long in atmospheric air. The results show that the sparkover voltage depends on the position and charging of the sphere particle of 0.1 or 0.2 cm in diameter along the gap axis. Ions generated by natural radiation in the gap lead to charge the metallic particle and contribute significantly to the sparkover voltage depending on the humidity in air. With the high humidity, the particle is quickly charged and the sparkover voltage falls in lower than half of the voltage without the metallic particle.

Reliability Improvement of Ground Fault Protection System Using an S-Type Horn Attachment Gap in AC Feeding System

Contact wires used in feeding system for electric railroad are insulated by insulators. However, insulation of an insulator sometimes breaks down by surface dirt of an insulator and contact with a bird. The insulator breakdown derives a ground fault in feeding system. Ground fault will cause a human electric shock and a destruction of low voltage electric equipment. In order to prevent the damage by ground fault, an S-type horn has been applicable as equipped on insulators of negative feeder and protective wire until present. However, a concrete pole breaks down at the time of the ground fault because a spark-over voltage of the S-type horn is higher than a breakdown voltage of a concrete pole. Farther, the S-type horn installed in the steel tube pole does not discharge a case, because the earth resistance of a steel tube pole is very small. We assumed that we could solve these troubles by changing the power frequency spark-over voltage of the S-type horn from 12kV to 3kV. Accordingly, we developed an attachment gap that should be used to change the power frequency spark-over voltage of the S-type horn from 12kV to 3kV. The attachment gap consists of a gas gap arrester and a zinc oxide element. By the dynamic current test and the artificial ground fault test, we confirmed that the attachment gap in the S-type horn could prevent a trouble at the time of the ground fault.