Step 2: Add the constant 20 to the result found in step 1. The breakdown voltage of air varies considerably with humidity and other factors, but figure roughly 1 kV per mm. . Since GAPin = GAPcm / 2.54, then Y x (GAPcm / 2.54) = 30 x GAPcm. I have re-read your replies but still think the outcome is incorrect. Enter each value in the appropriate space in step 2. It breaks the calculation process down into individual steps, and a final step converts the units from Joules per mm2 (J/mm2) to the more commonly used units of cal/cm2. R2 and R3 are two resistors in parallel and combined can be countedas a single 5M resistor as shown in the first formula in the diagram. Clearly more resistance was needed. High Voltage Arc Flash Calculator - OSHA, NESC ; DGUV-I 203-077 (formerly BGI/GUV-I 5188E) German Std. That means Ineed to be able to measure high voltages. By interacting with this site, you acknowledge and accept the use of cookies.Click here for more information. The worksheets, as well as the examples that follow, are from my book, Complete Guide to Arc Flash Hazard Calculation Studies, published by Brainfiller Inc. in 2010. Two Official Methods Described, 5 Minimum Arc Flash Label Requirements from NFPA 70E 2018. Your Dielectric Withstand Test uses ___ VDC (or ___ VAC). 30kV/cm * 2.54cm/in = 76.2kV cm / cm in = 76.2kV/in Ask Hackaday: Whats Your Worst Repair Win? Thats something I havent done. It only takes a minute to sign up. Replace all my GAPcm / 2.54 up there with GAPcm x 2.54 so GAPin = GAPcm x 2.54, Y x CAPin = 30 x CAPcm, this Y x GAPcm x 2.54 = 30 x GAPcm, thus Y x GAPcm = (30 / 2.54) x GAPcm, and Y = 11.8. International Electrotechnical Commission (IEC) In the real world there can be transient overvoltages, contaminants, condensation, etc. 3.1.1.3 Arc voltage sensors Arc voltage can usually be measured from the weld torch tip. If you want to transmit a lot of current, you need a thick conductor to avoid resistive losses (or the wires melting). The "Arc Distance in Helium" calculation is based on empirical data for a sharp point arcing to a plane in a helium atmosphere. If the test passes it will confirm that the smallestgap between exposed conductors in the cable is likely greater than ___ inches (___ mm). Positive and zero sequence impedance to IEC 60609. The total energy of the spark is determined by the applied voltage. For R1 I purchased 25 200M high voltage resistors (MX440-200M, 1%,11kV) from Caddockand connected them in series. replacing the solid ZnO with a ZnO granule-filled air gap. 1 Celsius Heat Unit (international table): Exactly 1 BTU IT x 1 K . This calculator also shows how using a Helium atmosphere can help your test be more stringent. Respected sir Please clear my confusion ASAP. Hi all, I have seen in several devices that the designers included spark gaps on the PCB near I/O connectors. Refer to the Arc Flash Tables for Hazard Risk Category, and appropriate Personal Protection Equipment (PPE) based on arc flash incident energy levels. Is this different for traces on a circuit board, or pins in a plug? The largerthe sphere diameter, the higher the voltage they get to beforethey no longer closely follow the 30kV/cm line. If you have no idea how electrical circuits work, or what people mean then they talk about volts and amps, hopefully I can shed a bit light. You are correct. The "Arc Distance in Air (max)" calculation is based on empirical data for a plane arcing to a plane. Math of spark gaps. Shame on me too since Im such a huge fan of dimensional analysis. How to prevent electric arc on a precision contact. My research suggests that the arcing distance is dependant on the medium and the pressure, so let's assume air (~79% nitrogen, ~20% oxygen, ~1% argon and a few other things) at 1 atmosphere or 1.01325 Bar. For more precise measurements I use a Fluke 80K-40 high voltage probe. The Fluke is good for up to 40kV DC but Ive had to measure higherand so I made my own probe. Relative Humidity (in air only) 4. The schematic on the right is a simplified way of looking at the circuitwith R3 pulled out of the meter and combined with R2. Thanks for your informative answer. You can add the calculated value of arc resistance to the original circuit, and you can recalculate the DC short-circuit current as follows: IDC arc = 256V (0.01150 + 0.00194 + Rarc), IDC arc = 256V (0.01150 + 0.00194 + 0.01051). This is where the rough guide of 1 kV/mm for arcing applies. To help mitigate that risk, there . The general ratio is 1.1kV per millimeter (or 11kV per centimeter), but there is no accurate way of determining it. This one is designed for use from 1kV to 40kV DC, with accuracy varyingfrom 1% to 2% depending on the temperature, and not including theaccuracy of the meter. 30kV/cm x 1cm = 30kV Meters with other impedances can be used with thehelp of an external shunt or a correction factor, all of which isdescribed in the probes documentation. The same physics apply. 5. IDC bolted = VDC (Rbattery + Rconductor), IDC bolted = 256V (0.01150 + 0.00194) = 19,048A. It can then be easily seen that A (the multiplier for cm) must be smaller than B the multiplier for inches. Why? As far as I know, you can think of it like a significantly less sophisticated MOV. An inch is longer than a cm ==> kV/inch must be greater than kV/cm. I expect that you'd need something really unusually sharp to strongly affect the minimum voltage. Not sure if this will be visible to all, and is a little off track. Therefore it would require ~10 kV to break down 20 mils of FR4. I had thought about manual switches but I am not sure if the arcing will cause an issue with the specific waveform I am trying to generate. Get a feel of the arc and the weld puddle. Would 240V arc significantly farther than 230V? On a circuit board, you also have to consider conduction along the surface. @raelik Let us know in the comments below. However, correcting the formula in the article would help make it useful for a wider range of people. You shouldn't rely on the above for safety purposes. The user must define the gap distance. The bottom line in dark blue isthe line according to the formula (essentially 30kV/cm): That formula defines a linear relationship between spark length andvoltage. The high value resistor is the greatest contribution to error so I start out with Caddock USF300 series resistors with 0.01% tolerance and 5ppm/C drift. Abbreviations used in Table 2 and Table 3: The Arc Flash Boundary is calculated according to IEEE 1584 2018 as follows: The Arc Flash Incident Energy is calculated according to IEEE 1584 2018 as follows: What is an Arc Flash Study? Since you study spark gap. And thats how I measure high voltage. If we apply theformula for a 5mm spark gap, we get 3 x 5mm = 15kV. The resistors were all soldered together with big, round solderbulbs to avoid sharp points which can cause losses due to ionization. Good lord. Meters Feet. Im measuring the voltage across a lifter thats being provided bya PC monitor power supply. Drag slider bars to change values. For this calculation, the DC arc models paper refers to another technical paper, Simple Improved Equations for Arc Flash Hazard Analysis, IEEE Electrical Safety Forum, Aug. 30, 2004, by R. Wilkins. drozafila liked Valor Tactical Stealth sUAS. Uninsulated conductors are not safe for use in products so those distances are not provided. Multiply k and Earc from step 1. The larger and rounder they are, the higher the voltage before a spark occurs. My point was to prove that Mr Dufresne was correct, and my flailing about wasnt really helping much. If the test fails you may have a gap less than ___ inches (___ mm). This second paper is the basis for DC arc flash calculations that many industry professionals and software packages currently use. New Breakdown Electric Field Calculation for SF6 High Voltage Circuit Breaker Applications . I need to wake the hell up before I try to math. Carefully read and follow the safety procedures, labels and signage for your equipment. And so the formula is usually simplified to just: Thats just another way of saying that theres 30kV/cm. This is the second episode of my Spark Gap Tesla Coil series. I was able to confirm that the probe didnt load the circuit too much by observing the intensity of the plasma in the speaker and seeing that it didnt chance noticeably. You can see that reflected in the chart in the article above. >>1 in = 2.54 cm, not the other way around. DC arc resistance and DC arcing current calculationsiterative solution. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. It looks like theres a bend upward at 50kV but thats because the voltage scale below 50kV increments by 5 and above 50kV it increments by 10. voltage Uc of a 2 mm gap) of pure SF6 and its relaxation properties at p=100 kPa were measured for T . FAQ What is Relation in voltage and arc length? ARC CURRENT, VOLTAGE, AND RESISTANCE IN A HIGH ENERGY, GAS-FILLED SPARK GAP by BRIAN LANE MAAS, B.S.E.E A THESIS IN ELECTRICAL ENGINEERING Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE IN ELECTRICAL ENGINEERING Approved /f^ccepie May, 1985 How to tell if my LLC's registered agent has resigned? The circuit voltage is 14v dc with very low current Assume the nominal air condition is low humidity and high temperature (>130 degrees C). 4. Visit the Terms of Use and Privacy Policy for this site. NO! I think it's used as sort of a ghetto ESD or over voltage protection. If the DC arc flash occurs in an equipment enclosure, the energy will be directed out of the boxs open end. When trying to get long spark you typically point the smaller ball on the positive side up towards the large ball on the negative side, then you will get 1 per 30kv which is slightly more than double the expected spark length for that voltage. Except for two technical papers referenced in the annex of NFPA 70E, DC arc flash equations and calculation methods are not yet part of any standard. The circuit designer's guide and calculator of the spacing between PCB traces for various voltage levels based on UL60950-1 and IPC standards. Press the multiply key. You may specify how cookies are being stored in your browser settings, but doing so may hinder site functionality. 46, No. 30kV/cm is not logically the same as kV = 30 * cm According to this paper, the following is the equation for determining the incident energy from a DC arc flash being focused out of an enclosure: Ei box = incident energy from an arc flash in a box at distance (d) in J/mm2. For bonus points, could answers be given for 120VAC too? Browse other questions tagged, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site, Learn more about Stack Overflow the company. Semantic Scholar's Logo. Step 2: Use the calculated arcing current I arc to determine the actual fault clearing time for your protection system, Step 3: Click on Calculate again, to calculate the Incident Energy and Arc Flash Boundary. When your spark gap is at the maximum distance at which you get a spark then just before the spark happens is when you have your maximum voltage. Im not sure about exhaled smoke, but I have seen high voltage lines arc to ground with a bushfire burning under them! Because of the complexities involving humidity, pressure and other factors, the result is a rough guide rather than an exact figure. System Grounding - Select system grounding method (either grounded or ungrounded/high-resistance grounded). Working Distance - Enter the working distance from energized equipment in mm. Best to not have to explain why a curve doesnt look quite right. The official IPC table also provides the numbers for external conductors at elevations >3050m as well as requirements for assemblies, which I omitted here. Uninsulated conductors in PCB's or connectors are covered in the clearance section of the table. Cool. Square each value, and add the two terms together. In order to get energy from the power plant to the users, the infrastructure is set up to jack up the voltage into the 100 kilovolt range. This is why you often see talk of clearance and creapage in the same discussion. kV = 30 * d(cm) Step 3: Enter the arcing short-circuit current (IDC arc) and raise it to the power of 0.88. LV and MV cables up to 33 kV with current capacity in accordance with BS 7671, ERA 69-30 and IEC 60502. There are a variety of factors including air, pressure\elevation, humidity, and dirt from the environment all affect the distance that an arc can form between two conductors. Note that the time does not affect the magnitude of the acing current. Corona power at onset, 1.01-inch stranded two-wire cage, dry, 27 kHz. Great tips. You can calculate the voltage needed for electricity to jump across a spark gap with a simple formula: voltage equals the air gap length in centimeters times 30,000. Just a note: the 3KV per mm does not work well with AC high voltage, especially at radio frequencies. The plasma column does not cross directly but angles back towards the oncoming diamond bits. Both calculations are for standard pressure (760 mmHg) and room temperature (72 F, 22.2 C). In order to determine both the flash protection boundary and incident energy, first the arcing current needs to be calculated. High Power 10 kv Generator Circuit. Source Voltage - Enter the source voltage. Gap Between Conductors - Typical range for gap between current-carrying conductors is 13 - 152 mm. This is the arcing time for the calculated reduced arcing current. I get a sustained bright blue atmospheric plasma across a gap of 3mm. zones for arc flash faults when working on or near energized equipment. This arc voltage calculator can help you understand how a Dielectric Withstand Test helps your quality process. D.R. Ignition coil arc initiation with protected low voltage continuation? In the Pern series, what are the "zebeedees"? Until then, since no standard exists for DC arc flash calculations, why would anyone perform them? You dont have to look too far back in the history of arc flash to find the answer. The pattern was a pair of arrows facing each other, with the solder resist cleared around the tips. R1 was also selected such that therewouldnt be a problem with leakage over its surface. Centimeters are longer than Millimeters, so the needed multiplier is larger and it is. If you are following the IPC-2221A rule set, then it can be assumed that adequate isolation has been provided. If powered with a 30 V power input, the circuit detailed below can provide a high voltage which range from 0 to 3 kV (type 2 an even provide from 0----10 kV. Most hackers work at atmospheric pressure which is 1 atm,so that can be left out of the formula. Voltage drop in accordance with CENELEC CLC/TR 50480. I've tried asking search engines sensible questions like "how far can 240V arc at 1 atmosphere" and "how far can electricity jump" but I haven't found any easy answer. Step 1: Enter IDC arc, Rarc and tarc obtained from the previous iterative calculations. Note that Category 0 is not listed in NFPA 70E. The arc flash duration will either be dependent on the clearing time of an upstream protective device operating or the reaction time of a person jumping away from the hazard. Currently, there are no standards for calculating the arc flash hazard for DC power systems. How is it forming plasma? Depending on the setting of the voltage, the IEG is set by the servo control. Once the voltage reaches the air-breakdown threshold, an . The air in the gap would still be fairly ionized before the next spark occurs, lowering the voltage needed for that next spark. The information on creepage is very interesting, and I can see how it deserves consideration when putting traces on a circuit board. stephenmanderson94 liked Multipurpose BLE touchpad HID. There are scales in KVs on the tool but not sure of the accuracy of the scale. When a high voltage transient is applied across the terminals of the spark gap, the gap breaks down electrically thereby diverting the energy to ground and protecting the equipment it is connected to. He also found that decreasing the gap with normal pressure caused the same behavior in the voltage needed to cause an arc. Learn more, Measuring voltage for a smoke precipitator, Measuring High Voltage In Millimeters (and Other HV Probe Tricks), http://www.extremeelectronics.co.uk/spark-growth-teslacoils/, http://hackaday.com/2016/06/15/wrangling-high-voltage/#jp-carousel-209541, http://hackaday.com/2016/07/13/expanding-horizons-with-the-ion-propelled-lifter/, Supercon 2022: All Aboard The SS MAPR With Sherry Chen, AI-Controlled Twitch V-Tuber Has More Followers Than You. You have to multiply in order to cancel out cm. Inches are longer than Centimeters so the needed multiplier is larger and it needs fixing. Therefore, Y x GAPcm = (30 / 2.54) x GAPcm, and through elimination Y = 11.8. man I cant write what Im thinking properly today. NAND gates N1----N3 are wired like an astable multivibrator (AMV), which powers the darlington transistors T1/T2 with a 20kHz souarewave frequency. IEEE 1584 currently suggests that a maximum time of 2 seconds may be used based on the reaction time and assuming there are reasonable conditions for a person to escape. If you found this information helpful, sign up for our monthly newsletter to learn the latest trends in cable and harness testing. It looks like theres a bend upward at 50kV but thats becausethe voltage scale below 50kV increments by 5 and above 50kV it incrementsby 10. Search. The official IPC table also provides the numbers for external conductors at . High Voltage Arc Gap Calculator. It lists recommended minimum spacing between internal and external conductors as a function of peak working voltage level for intended use at altitude below 3050 meter (10.007 feet). We used to use this a lot and you REALLY know when youve hit the right spot. High-Voltage Laboratory, Guangxi University, Nanning 530004, China . Include the protection relay and circuit breaker clearing time. International standards boards (namely IPC, and IEC) have come up with minimum distances between insulated conductors. On a practical level, even a sewing needle has a tip that's 10s of m across, so the field between two needles separated by 7.5m will still be fairly uniform. They are expensive though. ckerr4 liked Valor Tactical Stealth sUAS. This requires taking the DC voltage (V DC) and dividing by the known impedances of the conductor and battery string. When making the measurement, take the reading on the meter oroscilloscope and multiply it by 1000. To convert J/cm2 to cal/cm2 multiply by 0.239. Maybe note that coating and potting can reduce the required distances by quite a bit. Electrical Contractor Magazine, Dont Ignore the Parameters: Arc flash PPE category tables, Wearable Safety Devices: Smart technology use rises on construction sites, NSC Evaluating Standards for Head Protection. It also provides a series of calculation methods for determining the incident energy from a DC arc flash in open air as well as in a box. R1 has a very high resistance comparedto the meters impedance of 10M (R3) and the resistor that the meteris measuring across, also 10M (R2). dont smoke under half-million volt power lines during dry / crackley-whistley-buzzy weather!!! spark length = 10mm = 1cm = 0.3937in, 3kV/mm x 10mm = 30kV Also use quick logical estimates. If the gap is too small they can't get enough of a run up to knock off another electron before hitting the positive electrode. The predicted arc fault current for system voltages under 1kV depends on the bolted fault current, system voltage, arc gap, and whether the arc would most likely occur in the open air . Follow a three-step process to specify the arching time:. Once you have calculated the new value of IDC arc, you can substitute it back into the DC arc resistance worksheet and calculate a new value of Rarc. R1 and R2||R3 form a voltage divider. Assume the enclosure to be a panelboard and use the same working distance and arc duration from the earlier example. This calculator states that it only takes voltages between 400 and 3000VDC. The other is with the analog meter again but Im holding the probe in myhand. The highest Ive used it for is 75kV DC,though its designed for a maximum of 150V at the meter,which equates to an input voltage of 150kV. ]. A voltage of 3 kV will not break down 20 mils of FR4 between the planes. Because of all this its a pain to accurately guess voltage with spark gaps, unless you understand all these factors. Answer (1 of 11): In a metal object the charges that generates its voltage potential accumulate on those parts which are mostly rounded and so the shape of the metal object does count. Manufacturers dont like talking about this (and some dont even characterise it) but its often there and its measurable if you have a variable HT supply and a decent current meter. Depending where in the world you work, you are likely following one of two standards Internal Heating Element Makes These PCBs Self-Soldering, Turns Out, Lightning Can Strike Twice, With A Little Help, Grass Gauge Tells You When The Lawnmowers Catcher Is Full. Right sir? For example, to measure a spark plug, turn off the engine and remove the plug. At large gaps it depends roughly linearly on distance, and also depends on the composition, temperature and pressure of the gas. Because of the complexities involving humidity, pressure and other factors, the result is a rough guide rather than an exact figure. Select the method of measurement. It provides a step-by-step method for calculating the DC arc resistance based on the Stokes/Oppenlander equation. Maximum Available Fault Current - Enter the maximum bolted-fault current that the source can supply the circuit. The value of R1 was selected so that it wouldnt load down the circuitbeing measured. Therefore, I have included the mapping to Arc Flash Categories in the calculator. V= (3000x0Atmx1mm) + 1350. All your cables, for all your projects. Doans Arc Flash Calculations for Exposures to DC Systems helped elevate the discussion of DC arc flash calculations. on: June 05, 2018, 01:57:14 pm . After you've figured out your clearance requirements with an IPC-2221 calculator, you can program your clearances into your design rules to ensure your board remains safe and functional at high voltage. 2003-2021. Creapage is the shortest distance between to conductors along a surface. Learn how your comment data is processed. And yes 2.54 cm = 1 in but you cant substitute 2.54 cm to get inches. High Voltage Arc Gap Calculator This arc voltage calculator can help you understand how a Dielectric Withstand Test helps your quality process. Step 4: To obtain the DC arc resistance in ohms, divide step 2 by step 3. The result will be the incident energy in terms of J/mm2 at working distance (d). Hi Steven Chicago native John Papiewski has a physics degree and has been writing since 1991. As research on DC arc flash and DC source modeling continues, DC arc flash calculation methods will likely become part of a standard someday. Calculation of arc flash incident energy and protection boundary in accordance with IEE Std. Thanks all. Ball plane gaps have this effect too if the plane is negative and the ball positive. Together theyre usually labelled as R2||R3. For example, for uncoated tracks it is 2.5+ (V-500)0.005 (mm). This means that there's a minimum sparking voltage of 327V at 7.5m in normal air. Figure 2 illustrates the circuit that is used as an example for calculating the DC arc resistance and the DC arcing current. The breakdown gradient for creapage is lower than for clearance since dirt can accumulate on surfaces. Even though IEEE 1584 was first published in 2002, some people were performing arc flash studies and calculations for AC systems long before then. In hindsight, I should have gone with higher resistance but longerresistors which would have made for a shorter probe. Test it out on a spark gap which is just about ticking over and youll see what I mean. Finally move on to adding filler wire as in the video below. could form between them? A case study of an arc flash analysis for a large university . Thanks for contributing an answer to Electrical Engineering Stack Exchange! Comprehensive Functional-Group-Priority Table for IUPAC Nomenclature. Thomas Edison was well-known for his Pearl Street generating station in New York City, which was based on DC. Unfortunately pressure in the cylinder, fuel mixture all contribute to that same ability to fire the mixture within the cylinder, so not sure how 1 inch gap in the atmosphere translates into the same ability within the cylinder, I am get a 7mm spark from a Van de Graaff generator globe, however when I measure the voltage with a high voltage probe I get around 4 kilovolts. Assuming this, you can calculate DC arc resistance and use it to recalculate the DC arcing current. The calculator also supports the Ralph Lee Method, This method is good for a rough estimate. LV and MV cables up to 33 kV with current capacity in accordance with BS 7671, ERA 69-30 and IEC 60502. This will help you get a feel for how the puddle moves, and practice in maintaining a tight arc length. Only the values are used. In desperation, I tried measuring the maximum spark gap length using my homemade probe. High voltage circuits often dont have much sparecurrent for measuring purposes. Our goal is to make science relevant and fun for everyone. I hadnt thought of using brass dome nuts. For air at standard temperature and pressure it's about 3.3MV/m. As the gap gets very small the voltage to create a spark actually increases again. MathJax reference. I need to determine the minimum air gap between two voltage carrying terminals, in order to prevent arcing. The next step in this process requires a series of iterations. Notes: The "Arc Distance in Air (min)" calculation is based on empirical data for a sharp point arcing to a plane. Reference the 2015 NFPA 70E: Standard for Electrical Safety in the Workplace for a more complete reference for Arc Flash Hazard calculations and safety. (Or I am wrong, which would make twice this year, which is highly unlikely! Sen, provides a comparison study of the existing body of research into DC arcs and arc flash modeling that has been conducted over the years. Except it had insulating plates going down its length. He has contributed to "Foresight Update," a nanotechnology newsletter from the Foresight Institute. By billvanderhoof Date 04-30-2004 03:06. If so, that will be super useful since source of the the ticks can be hard to find sometimes, specially when its dangerous to get too close. (1) Where: Eave . Assuming that higher temperatures and higher humidities both increase the possible arcing distance, let's choose something harsh like 40 degrees Celsius and 95% humidity. To make the end product the same (the breakdown voltage) your multiplier must be larger. According to NFPA 70E, PPE Categories should not be used when the Incident Energy Method is used. I just happen to have a couple of those lying around, I love Tesla coils (: The fault clearing time for the calculated normal arching current. The contacts get as close as 0.25 of an inch and then an arc is attained. The oscilloscope photo below shows this changing voltage. Determine the arc fault currents. Youre right in saying that inches are longer than cm totally agree. The minimum voltage required to initiate an electrical arc in gas is described by Paschen's Law. Power frequency spark over voltage = 1.5 Voltage rating of LA. How many grandchildren does Joe Biden have? I've repeatedly read DRY AIR arcs between smooth flat plates at 3,000 volts per millimeter. In the first table, the distance essentially doubles for off PCB conductors. Enter system voltage (kilovolts rms, maximum): Enter maximum transient overvoltage (per unit)( 1): Altitude (in meters): Phase-to-ground exposure. I talk about various high voltage transformers and power supplies, current limitation, series a. Switch 2020, 58, 19 . Similar to the IEEE 1584 calculation methods, consideration must be given to whether the DC arc flash occurs in open air or in an enclosure/box. To protect a unit (e. g., a series capacitor in a transmission line) against overvoltage, an arc-inducing device, so called spark gap, is connected in parallel to the unit. That is unless youre working withVan de Graaff generators, but even then usually only the dome isspherical and the other electrode isnt. When your. Always consult with an engineer Network Sites: Latest; . Gap voltage is the voltage in the gap between two electrodes. - "VLF/LF High-Voltage Design and Testing" Skip to search form Skip to main content Skip to account menu.
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