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Corona Threshold Voltage

Team Tesla:Chris Rowan

Anthony ThompsonBrandon SciortinoPhilip de la Vergne

Aaron Wascom

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Presentation Purpose

• This Presentation describes the preliminary design for the electrical breakdown experiment by Team Tesla for the LaACES Program. It fulfills part of the LaACES Project requirements for the Preliminary Design Review (PDR) to be held February 5,2013

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Document Scope

• This Pre-PDR Presentation specifies the goal, objectives, background, and requirements for the electrical breakdown experiment and provides a guideline for the development of this payload under the LaACES Project. As such, these topics provide the basic for developing the PDR document and presentation.

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Mission Goal

• To study the effects of humidity and temperature on the electrical breakdown of the atmosphere to prevent sparking and ensure safety.

http://www.scienceclarified.com/Di-El/Electric-Arc.html

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Science Objectives

• To conduct an experiment of the breakdown voltage in air at varying altitudes

• To observe the effects that temperature and humidity have on our expected recreation of Paschen’s curve

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Technical Objectives

• Measure temperature, pressure, humidity, current, and discharge voltage for the duration of the flight

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Science Background: Electric Discharge

• Results from the creation of a conducting path between two points of different electrical potential

• Three Types:1. Corona Discharge2. Spark Discharge3. Brush Discharge

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Science Background:Corona Discharge

• Occurs when the threshold voltage is breached

• Only requires a high field strength

• Current ranges around micro amps

www.ce-mag.com/archive/1999/novdec/mrstatic.html

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Science Background:Spark Discharge

• Occurs when the threshold voltage is breached

• Complete ionization between electrodes

• Maintained through a continuous high voltage source

http://www.ehow.com/how_5884896_avoid-static-shock-open-door.html

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Science Background:Brush Discharge

• In between the corona and spark discharge

• It may appear as irregular luminescent paths

http://www.electrotherapymuseum.com/2009/Protocakes/index3.htm

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Science Background:Corona Threshold Voltage

• The potential at which corona is found to originate

• Ohm’s law regime– Once the threshold is breached, current

increase proportionality with voltage

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Science Background:Avalanche Effect

Ionization of neutral atoms becomes possible when the KE of free electrons increase

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Science Background:Paschen’s Curve

• V=f(pd)• The minimum of

this curve corresponds to the minimum Pxd product for which the ionization effect is maximal

http://www.sciencedirect.com/science/article/pii/S146685640200067X

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Science Background:Humidity

• Partial breakdown threshold reverses from decreasing the threshold to increasing it once the pressure drops below a certain point – 20,000-25,000 ft.

• Humidity can affect the magnitude of the current moving through the ionized air by up to 20% in a pulse corona

• Pulseless corona and negative corona is not affected by changes in humidity

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Science Background:Atmospheric Conditions

http://www.aerospaceweb.org/question/atmosphere/q0090.shtml

• Flight profile of expected payload environmental conditions

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Science Background:Temperature

• Temperature decrease ionization energy increase avalanche effect decrease breakdown voltage increase

http://www.green-planet-solar-energy.com/double-glazing-materials.html

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Technical Background: Electrodes

• Electrode - an electrical conductor that is used to make contact with a nonmetallic part of a circuit

http://www.mikeblaber.org/oldwine/BCH4053l/Lecture05/Lecture05.htm

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Technical Background: Positive vs. Negative Corona

Positive• More stable discharge• Linearly sensitive to

changes in humidity• Produces less ozone

than negative corona

Negative• More self-sustaining

discharge• Humidity has little to

no effect• Can only be

sustained in fluids that contain electronegative molecules

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Technical Background:Electrode Geometry

• Point– Small surface

area– Concentrated

electric field

http://cnx.org/content/m42317/latest/

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Technical Background:Electrode Geometry

• Plane– Evenly distributed

electric field– Larger surface area

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Technical Background:Electrode Configuration

• Point-Plane– Surface area

ratio – Ionization

energy

http://www.imp.gda.pl/fileadmin/old_imp/ehd/coronast.gif

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Technical Background:Electrode Composition

• Surface– Texture– Impurities – Surface Area

• Electrode Material– Dielectric Strength– Conductivity

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Technical Background:Previous Experiments

• Stainless steel electrodes

• Mean discharge current determined by voltage drop over R

• Breakdown voltage is mean value recorded from Oscil.

• Copper anode and SS cathode

• Voltage increased by increments and allowed to settle

• Current spikes from 1 nA to hundreds of mirco-amps

• Voltage quickly reduced to zero

A mathematical model of the modified Paschen’s curve for breakdown in microscale gaps

Influence of Axial Magnetic Field on the Electrical Breakdown and Secondary Electron Emission in Plane-Parallel Plasma Discharge

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Technical Background:Measurements

• Measurements during flight:– Temperature– Pressure– Humidity– Voltage– Current

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Technical Background:Environmental Sensors

• Temperature Sensor– Small signal p-n junction diode

• Pressure Sensor– Piezoelectric sensor

• Humidity Sensor– Capacitive sensing element with on-chip

integration

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Technical Background:DC to HVDC Converter

• An electronic circuit which converts a source of direct current from one voltage to another

• Due to the payload size and weight restrictions, the required voltage for discharge is improbable with on-board batteries alone

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Technical Background:Current Sensor

• Pico ammeter– Voltage drop across resistor

• Radio Frequency Interference– Band of frequencies produces upon

discharge

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Science Requirements:Spark Gap

• The gap distance shall be 1mm• The electrodes shall be composed of

copper• The electrodes shall be rough and clear of

impurities• The electrode configuration shall create a

positive corona discharge

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Science Requirements:Power and Sensor

• The spark gap shall be provided with a maximum of 4.5kV

• The payload shall record temperature, pressure, humidity, voltage, and current across the spark gap

• The payload shall be fully operational throughout the entire flight profile

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Technical Requirements

• The ammeter shall have a minimum accuracy to the microamp range

• The HVDC shall operate in all environmental conditions

• The output voltage of the DC to DC converter shall be controlled through an on-board interface

• All data shall be time-stamped and real-time clock must be synced to the payload GPS

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Technical Requirements:LaACES

• The payload shall not weigh more than 500 grams

• The payload shall not exceed 3 oz / in2 on the smallest face

• The payload equipment shall cost less than $500

• The payload shall have two holes 17 cm apart running the length of the payload to comply with LaACES management requirements

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Project Management:Team Contract

• Team Meeting• Disciplinary Action• Communication• Version Control• Decision Making• Team Roles

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Project Management: Organization

Task MemberProject Management Anthony ThompsonScience Requirements Chris RowanElectronics Aaron WascomFlight Software Aaron WascomMechanical Integration Philip de la VergneSystem Testing Brandon SciortinoCalibrations Philip de la VergneData Processing and Analysis Anthony ThompsonDocumentation Chris Rowan

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Change Control & Update Procedures

• Changes to this Pre-PDR document shall follow all regulations set by Team Tesla’s contract and only be made after approval by designated representatives from Team Tesla and the LaACES Institution Representative. Document change requests should be sent to Team members and the LaACES Institution Representative and the LaACES Project.

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Project Management: Master Schedule

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Reference Documents• http://www.phys.tue.nl/FLTPD/invited/veldhuizen.pdf• http://arc.uta.edu/publications/td_files/paniker.pdf• http://www.isesp.org/icesp%20viii%20papers/VIII-ICESP%20PA1-1.pdf• http://fog.ccsf.cc.ca.us/~wkaufmyn/ENGN45/Course%20Handouts/15_ElectricalProps/07_Impurit

iesConductivityConductors.html

• http://prb.aps.org/pdf/PRB/v61/i16/p11109_1 • http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4075398 • http://www.jstor.org/stable/10.2307/96578 • http://rspa.royalsocietypublishing.org/content/167/931/580.full.pdf • http://arc.uta.edu/publications/td_files/paniker.pdf• http://www.lorentzcenter.nl/lc/web/2010/424/PROBLEMS/NXP/OverviewWallashspie.pdf• http://www.ce-mag.com/archive/1999/novdec/mrstatic.html• http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD0720090• http://neon.dpp.fmph.uniba.sk/workgroup/media/documents/microdischarge_1.pdf• http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=AD0430336• http://prl.aps.org/pdf/PRL/v90/i22/e224801• http://www.highvoltageconnection.com/articles/corona.pdf• http://www.dtic.mil/dtic/tr/fulltext/u2/a239940.pdf• http://ethesis.nitrkl.ac.in/2875/1/Full_Thesis_Print_04.07.2011.pdf• http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD0720090• http://

www.irispower.com/pdf/newtechpapers/Investigation%20of%20the%20effect%20of%20humidity%20on%20partial%20discharge%20activity%20in%20stator%20windings.pdf

• 143.53.36.235:8080/Medical/research/CoronaDischarge.doc• www.haefely.com/pdf/scientific/e1-19.pdf - Switzerland