Robert Thorbus
Reinhold Henke
580 California St., Suite 400
San Francisco, CA, 94104
THE ARC SPECIES ZOO; Arcs Are Self-feeding Plasma Burning Monsters; Sparks Are Not
2021, AST Academic Poster #4 of 16
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Abstract
There are a vast number of different arc “animal names” due to arcs being named as they were observed across different applications and industries during the industrialization of electricity. This is similar, however, to the names of “Puma,” “Mountain Lion,” and “Cougar” being given to the same big cat species depending on where and by whom it was first encountered. Further complicating the understanding of arcs is the frequent association with “sparks,” which do not occur within the power contact cycle!
Related papers
Tracking down the origin of arc plasma science I. early pulsed and oscillating discharges
IEEE Transactions on Plasma Science, 2003
Abstract—The early development of arc plasma physics is closely related to the development of suitable sources of electrical energy. The harnessing of electrostatic charge in Leyden jars (early capacitors) enabled the controlled production of sparks and pulsed arcs. A ...
Arc initiation in cathodic arc plasma sources
A "triggerless" arc initiation method and apparatus is based on simply switching the arc supply voltage to the electrodes (anode and cathode). Neither a mechanical trigger electrode nor a high voltage flashover from a trigger electrode is required. A conducting path between the anode and cathode is provided, which allows a hot spot to form at a location where the path connects to the cathode. While the conductive path is eroded by the cathode spot action, plasma deposition ensures the ongoing repair of the conducting path. Arc initiation is achieved by simply applying the relatively low voltage of the arc power supply, e.g. 500 V-I kV, with the insulator between the anode and cathode coated with a conducting layer and the current at the layer-cathode interface concentrated at one or a few contact points. The local power density at these contact points is sufficient for plasma production and thus arc initiation. A conductive surface layer, such as graphite or the material being deposited, is formed on the surface of the insulator which separates the cathode from the anode. The mechanism of plasma production (and arc initiation) is based on explosive destruction of the layer-cathode interface caused by joule heating. The current flow between the thin insulator coating and cathode occurs at only a few contact points so the current density is high.
Electric arc explosions
Interflam 2010, 2010
When an electric arc is created, a pressure event occurs. There can be two aspects to this: the shock and sound waves propagated from the expanding arc channel, and the bulk pressurization of the en-closure, if arcing is taking place within a closed volume. The present paper is the first systematic re-view of the research on both these pressure phenomena. Quantitative studies on electrical arc explo-sion pressures date back to the 1920s, although arc pressures generated by lightning, which is a type of electric arc discharge, have been studied since the 1700s, but understanding of the phenomena is still not complete or exhaustive. Experimental data are compared to theoretical predictions. It is shown that in an enclosed volume some extremely high pressures can be generated, if the arc current is sufficient. Such pressures can destroy buildings and mechanical equipment and cause injuries or death to nearby individuals. Even without enclosures, the shock waves produced from high energy arcs can cause injuries, although arc flash injury may be of greater concern. Injury potential generally requires that high currents be available, and serious damages or injuries are not associated with low-energy arcing occurrences.
Electric arcs: their electrode processes and engineering applications
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Theory of partial discharge and arc formation
2011
The demand for electrical power has consistently risen over time, whether it be to support the development and expansion of cities or because traditional approaches to societies solutions are being replaced by their electrical equivalent. The automotive industry is beginning to introduce more electric, greener vehicles. The aviation industry is also being challenged with the same issues. Whatever the motivation, this rising demand for power is always facilitated by employing higher and higher voltage levels. It is well understood that if the voltage is too high for a given air gap, electric breakdown will occur. this effect is exacerbated by increases in altitude, resulting in constant challenges in aviation to satisfy the contradictory demands for smaller/lighter compact solutions against the biggest possible air gaps necessary to prevent electric breakdown. An experimental curve by Louis Karl Heinrich Friedrich Paschen was developed, which relates the voltage at which electric bre...
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IEEE Transactions on Plasma Science, 2003
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Arc Plasma Propagation and Arc Current Profiles
IEEE Transactions on Plasma Science, 2019
When electrical arcs occur in space, a plasma expands away from the arc-site, neutralizing adjacent surfaces (a current), and causing a current to be produced at the arc-site (source of neutralization current). The speed of this plasma expansion depends on the plasma species, which in turn depend on the ionizable materials near the initial electrostatic discharge (ESD) site. Based on laboratory experiments undertaken as part of the U.S. round-robin experiments on plasma propagation speed, a scenario for arc plasma propagation and arc current profiles is presented. It is found that the complex arc current profiles invariably seen in laboratory arcs are due to a multicomponent plasma, where each plasma species expands away from the arc-site supersonically and with approximately constant velocity. Apparent slowing of the arc plasma seen in high-speed video cameras is caused by the density depletion of the lightest (most rapid) plasma component first and heavier (slower) plasma components later. Electron currents onto surfaces originate at the arc-site, and the conductive arc plasma is a conduit for these currents. Sudden, simultaneous onset of arc currents at all distances from the arc-site is the result of blowoff currents, making all surfaces more positive, which then attract ambient electrons. Sudden, simultaneous cutoff of arc currents at all distances from the arc-site is the result of collapse of the plasma due to conditions at the arc-site. The ionization at the arc-site during the arc is seen to be rapidly variable, with variations on the nanosecond timescale. This model not only makes the varied plasma velocities reported in the literature understandable, but it also makes predictions about the arc radiofrequency interference (RFI), contamination produced by the arcs, and the total charge in an arc possible. Arc-site materials are suggested which, being hard to ionize and with massive ions, minimize arc currents and maximize arc current rise times.
Generating extra long arcs using exploding wires
Journal of Applied Physics, 2011
Analysis on the spectra and synchronous radiated electric field observation of cloud-to-ground lightning discharge plasma Phys. Plasmas 18, 113506 Self-neutralized ion beam J. Appl. Phys. 110, 083308 Spectrographic temperature measurement of a high power breakdown arc in a high pressure gas switch Rev. Sci. Instrum. 82, 093112 (2011) Effect of a floating electrode on an atmospheric-pressure non-thermal arc discharge J. Appl. Phys. 110, 033308 Mitigation of nonthermal plasma production to measure the pulsed magnetic field threshold for the thermal formation of plasma from thick aluminum surfaces Phys. Plasmas 18, 056304 Additional information on J. Appl. Phys.
Discussion of "Electric arcing burn hazards
IEEE Transactions on Industry Applications, 2006
I welcome the growing interest in arc-flash studies and thank Stokes and Sweeting for their interesting paper [1]. R. Lee certainly made many simplifying assumptions. The great value of his paper is that it succeeded in relating theoretical electrical power system arcing fault energy to the possible incident energy on employees in a quantitative way. Granted that it was crude, but it was the starting point for all arc-flash incident energy studies and programs. The Stokes and Sweeting paper is very critical of Lee's analysis and model. One test of the value of a model is looking at how well it compares to other models. Many people have found that Lee's method gives results that are remarkably close to the results obtained by applying IEEE 1584 to 480-V cases. In the 1584 guide, the Lee method is recommended only for cases over 15 kV or with bus spacing greater than 150 mm, and results are recognized to be very conservative for those cases. It should be noted that almost all industrial, commercial, and utility generation plant cases encountered in actual arc-flash studies involve possible arcs in enclosed equipment with tight bus spacing and a system voltage under 15 kV. IEEE 1584 offers an empirically derived model for those cases. Under arc modeling, [1] speaks of arcs self extinguishing in < 10 or < 40 ms. In the testing sponsored by the P1584 Working Group, we also experienced this problem. Depending on voltage, electrode spacing, box size, and perhaps other factors, the arc may or may not be sustained-the arc may last only until the trigger wire is burned away. However, test setups can be changed so that the arc will be sustained until switched off. Only test results obtained while using these setups were included in the P1584 Working Group test database. This enabled the development of a model that simulates the realworld case where protection may be set for a relatively long time. Reference [1] describes tests involving long horizontal electrodes pointed to the location where an employee might stand when operating the equipment. In these tests, the arc extended a considerable distance from the electrode tips toward the likely employee's location. While the authors of [1] told me that this type of equipment is used in Australia, I have never seen it. Later testing by others has been conducted to compare the results of testing with horizontal electrodes of long lengths and very short lengths, of the type that is common in standard North American and European equipment. These tests showed that the possible arc projection distance is much shorter for equipment with short horizontal buses. The IEEE Standards Association has approved the development of a second edition of the 1584 guide to extend the range of applications and to improve the preciseness of the calculations relative to realworld equipment. This next edition is expected to address different bus configurations and additional arc-flash hazards. A test program is being planned by a joint IEEE/NFPA Collaboration.
Related topics
THE ARC SPECIES ZOO
7900 INTERNATIONAL DR STE 300, BLOOMINGTON, MN 55425
Arcs Are Self-feeding Plasma Burning Monsters; Sparks Are Not
www.A rcSuppressi onTechno l o g i e s .c o m
By Reinhold Henke and Bob Thorbus
The Arc Lifecycle
An “arc” is a man-made “arc-discharge phenomena" in which burning plasma is maintained by a permanent AC or DC power source. Arcs are “contact arcs” when connecting
or disconnecting power (intentionally or unintentionally). Every arc follows the same lifecycle of: 1. Initiation, 2. Plasma, and 3. Dissipation; and occasionally 4. Re-Initiation
(Table I, ref. 1). (Note that “sparks” and “arcs” are NOT the same … sparks, whether a
small electrostatic shock or a bolt of lightning, are initiated by field emissions and are
supported by a transient power supply.)
1. Initiation “Birth”
There are two arc initiation mechanisms:
•
Thermionic-emission-initiated-arc — “T-Arc”
•
Field-emission-initiated-arc — “F-Arc”
2. Plasma “Life”
There are two types of power that maintain an arc:
What Is The “Arc Species Zoo”?
•
Alternating Current (AC)
•
Direct Current (DC)
3. Dissipation “Death”
There are a vast number of different arc “animal names” due to arcs being named as they
were observed across different applications and industries during the industrialization of
electricity. This is similar, however, to the names of “Puma,” “Mountain Lion,” and
“Cougar” being given to the same big cat species depending on where and by whom it
was first encountered. Further complicating the understanding of arcs is the frequent
association with “sparks,” which do not occur within the power contact cycle!
Dispersion of residual ionization, heat and debris
4. Possible Re-Initiation “Afterlife”
Residual ionization, heat and debris may yield:
After 10 years of industrial research, sifting through the “clutter and confusion” of the
“zoo” of innumerable arc “names,” we now understand that there are only three basic
“species”. We differentiate these “arc species” by their respective arc initiation (Table II).
“Arc Species”
Arc Initiation
Mechanism
Examples of
“Arc Names”
(In alphabetical order; by
no means a complete list)
T-Arc Species
•
Favorable conditions within gap for re-initiation
•
Plasma reigniting and burning again (F-Arc only)
Table I (above): The Arc Life-Cycle
F-Arc Species
T-Arc/F-Arc Hybrid
Current flowing
+ opening or closed contact
+ Joule heating
+ thermionic emission
+ plasma
Voltage present
+ closing or open contact
+ dielectric breakdown
+ field emission
+ plasma
T-Arc followed a series of re-initiated F-Arcs
— or —
F-Arc followed a series of re-initiated F-Arcs
= T-Arc
= F-Arc
Bounce arc, Break arc, Break bounce arc, Breaking
arc, Cleaning arc, Clearing arc, Drawn arc, Fault arc,
Floating arc, Make bounce arc, Metallic arc, Opening
arc, Short arc, etc.
Chopping arc, Closing arc, Fault arc,
Flashover arc, Gaseous arc, Make arc,
Making arc, Reinitiated arc, Secondary
arc, Vacuum arc, etc.
Circular arc, Contact arc, Continuing arc, Commutator
arc, Hissing arc, Inductive arc, Internal arc, Interrupted
arc, Long arc, Low pressure arc, Ongoing arc,
Showering arc, Standing arc, Switching arc, Transient
arc, Welding arc, etc.
Table II (above): “Arc Species” Definitions by Arc Initiation Mechanism(s)
Arcs in the Contact Cycle
Arcs are either T-Arcs or F-Arcs between two electrodes
and are supported by a continuous supply of power
(Table III, ref. 2).
Why is this important? Because the large number of
“animal names” in the Arc Species Zoo (often
combined with a conflation of arcs and sparks; which
are NOT the same) have resulted in confusion.
This confusion has led engineers, designers, and technicians to employ inadequate or inappropriate arc
suppression counter-mechanisms in an attempt to suppress contact arcing. For example, “snubbers” do not
suppress the various arcs that occur during normal relay
or contactor operation (“snubbers” are for “sparks”).
We hope that our findings, which are based on 10 years
of industrial research, can help industry better understand the problems associated with arcing … and how
to implement better solutions to suppress arcing.
Contact
Cycle
State
Equivalent
Lumped Element
Circuit Diagram
Lumped Elements
I.
OPEN
AC/DC
Power
Contact.
Notes
Arc Initiation
Mechanism
Arc Name
Example(s)
F-Arc
Flashover arc
Fault arc
F-Arc
Make arc
T-Arc
Bounce arc
Hybrid
Inductive arc
T-Arc
Floating arc
Fault arc
T-Arc
Drawn arc
F-Arc
Re-initiated arc
Hybrid
Continuing Arc
A fault can occur if the
voltage across the
opened contact exceeds
the contact’s dielectric
isolation voltage rating.
Lumped Elements
II.
MAKE
The closing contact will
experience a normal
dielectric breakdown
before making contact.
AC/DC
Power
Contact.
Lumped Elements
III.
CLOSED
AC/DC
Power
Contact.
A fault can occur if the
current through the
closed contact exceeds
the contact’s short circuit
current rating.
Lumped Elements
IV.
BREAK
The opening contact will
experience a normal
Joule heating (I2 R effect)
before breaking contact.
AC/DC
Power
Contact.
References:
1. M. Atalla, Mechanisms of the initiation of the short Arc, 1954
2. R. Holm, Electric Contacts Handbook, Springer Verlag, 1958
Table III (above): Arc initiation mechanisms within the contact cycle.
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Academic Poster #4 - May 2021