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Conductor clashing is a phenomenon when two or more conductors (objects that allow the transmission of charge), such as electrical cables or power lines, come into contact or close proximity, leading to disturbances in the flow of electrical current. This disturbance can occur as a result of many factors, encompassing a wide range of environmental conditions, natural events, and human-related behaviors that can lead to the unintended contact of power line conductors, triggering complex physical and chemical processes. The process starts with heat being created as a result of the conductor material melting and vaporizing upon contact. The vaporizing metal leads to an increase in pressure, transforming the vaporized metal into sparks (high-temperature molten metal particles). These sparks might be carried away by the wind and land on nearby vegetation. Occasionally, these sparks start fires that grow to produce wildfires that cover acres of surrounding areas. [1][2]These fires lead to great financial losses and leave significant damages, which is why proper safety measures and protocols are essential to prevent clashing and ensure the safe and efficient distribution of electricity.[3] 

Causes

The occurrence of conductor clashing in power systems can be attributed to a variety of factors, including environmental conditions, natural occurrences, and human-related behaviors.

Weather

One significant contributing factor is the impact of environmental conditions, where heavy winds or gusts, often associated with severe storms or hot weather conditions, can lead to the inadvertent contact of two conductors. This situation is particularly pronounced in scenarios where there is excess sag in power lines or other structural conditions that allow conductors to move into close proximity, creating the conditions for conductor clashing.[1]

Nature

The presence of trees near power lines adds another layer of complexity to the issue. During inclement weather or as a result of natural phenomena, tree branches may break and fall onto the wires, bringing the conductors together, and increasing the potential for conductor clashing.[1]

Wildlife

The interaction between wildlife and power lines also plays a role in conductor clashing events. Birds, in particular, can inadvertently cause power lines to sag when they perch, land, or interact with them. Other animals that also walk across conductors, such as squirrels, can also have this affect. [4]

Collisions

Human-related behaviors and accidents represent yet another critical set of factors that can lead to conductor clashing. Vehicular collisions with utility poles can result in pole leaning, which in turn may cause power lines to clash. This type of collision, often the result of accidents, can have a cascading effect on the power system, leading to conductor clashing.[4]

Vandalism

Acts of vandalism targeted at power lines introduce another reason for conductor clashing. Deliberate acts of hurling objects at power lines can induce drooping and the subsequent collision of wires. [1]

Process

When conductors clash, a series of complex physical and chemical processes occur, involving intense heat, vaporization of conductor material, and the expulsion of metal particles.

Heat and Vaporization

When two conductors of a power line clash, an intense heat is generated during this event, which can lead to the melting and vaporization of the conductor material. This results in the formation of a high-pressure gas consisting of metal vapor and other byproducts. The pressure within the conductor can become high enough to eject tiny molten metal particles from the point of contact. These ejected particles, often in the form of sparks, are then carried away by the wind. [5]

Combustion

Several key factors define a conductor clashing event. These include the energy of the electrical arc and the erosion of the conductor material. The energy of the arc is influenced by factors like the voltage between the separating conductors (arc voltage), the short-circuit current, and the duration of the arc. These parameters collectively determine various aspects of the event, such as the amount of material removed from the conductor, the size and number of particles generated, and whether these particles are in a molten or burning state. [4]

Chemical Reaction

When aluminum conductors are involved, the arcing event is characterized by a bright flash, the emission of sparks, and a puff of white smoke. The intense heat of the arc causes the underlying metal to reach its boiling point and vaporize. When these vaporized metal particles come into contact with the air, they ignite and burn rapidly, forming (aluminum oxide) as small aerosol particles. These aerosol particles can reach temperature anywhere from 930 K (Kelvin) to 2730 K and create the characteristic puff of smoke. [4]

Effects and Consequences

Fire ignition resulting from conductor clashing has been a recurring issue worldwide, with numerous instances occurring in various countries. Such incidents can lead to significant environmental damage, such as forest fires, as well as substantial financial losses and, in some cases, pose potential threats to human lives.[1][2]

An example of a conductor clashing catastrophe occurred in Western Australia on December 2nd, 2004. A 19.1 kV (kilovolt) conductor became dislodged from a pole-mounted insulator at the first pole and subsequently clashed with the underslung running earth conductor approximately 200 meters away. This collision led to a flashover(ignition of combustible material in an enclosed area), releasing hot metal particles (sparks) that ignited dry harvested stubble, which initiated the wildfire. During the fire, both the conductors broke, and the first ultimately failed due to structural deterioration and strong northerly winds. The property owner had previously reported a low-hanging power line conductor near the first pole, which, when both conductors fell and contacted the dividing fence, sparked the wildfire. The property owner estimated that approximately 468 hectares of land had been burned.[6]

Experiments and Results

This section outlines an experiment aimed at looking into the generation of particles, in terms of size, number, and behavior. This experiments aim to provide insight about the phenomenon and help find solutions to create protocols to maintain safety when conductor clashing occurs.

Experiment 1

These three scenarios were examined:

  • 100A-rated fuse that met overload criteria
  • 125A-rated fuse at the limit
  • 160A-rated fuse that did not meet overload criteria.

Line-to-line short-circuit current equation:

Where

are positive and negative sequences of short circuit impedance (measure of opposition that a circuit

offers to the flow of alternating current) in subtransient period.

is nominal system voltage(standard voltage level for system)

c is voltage factor (difference between nomial voltage and actaul voltage)


Using this equation, the line-to-line current was calculated to be 1700 amperes. This is the measure of the electric current that flows through the conductors when they come into contact. This current is significant because it determines the behavior of the conductor clashing event, including the generation of sparks and the effectiveness of fuses in protecting the system. In this case, the line-to-line short circuit current of 1700 A was used for testing different fuse rated currents and assessing the protection tripping times in response to conductor clashing. The simulation and analysis helped determine the adequacy of the fuses in different scenarios, with variations in fuse rated current. [1]


The following tables show the number of particles, means of diameter of particles in mm, standard deviations, and coefficients of skewness (a measure of the distribution's shape) obtained in experiments in the live network and in the laboratory under the different fuse rated currents.

Live Network
Fuse rated current [A] 100 125 160
Number of Particles 184 544 1100
mean (mm) 0.582 0.698 0.852
standard deviation 0.225 0.256 0.334
skewness 1.519 1.036 0.378
Laboratory
Fuse rated current [A] 100 125 160
Number of Particles 57 156 256
mean (mm) 0.675 0.678 0.732
standard deviation 0.274 0.239 0.320
skewness 0.919 0.957 1.117

This study first calculates the line-to-line short-circuit current, finding it to be 1700A. It then examines the relationship between fuse ratings(the current-carrying capacity of the fuses) and protection tripping times, noting a correlation between manufacturer catalog data and the cessation of spark generation during experiments. The analysis further investigates particles generated during conductor clashing experiments, conducted in both real networks and a lab setting. The descriptive statistics, like mean diameter and skewness, revealed that mean particle size increased with higher fuse ratings in the live network, while skewness coefficients decreased. On the other hand, there was an inverse relationship between the lab fuse ratings and the skewness coefficient, where higher fuse ratings led to higher skewness coefficients. The average mean rises from 0.582 to 0.852 in live network and only from 0.675 to 0.732 in laboratory. [1][7][8]

The descriptive statistics like mean particle diameters and skewness coefficients vary with different fuse ratings, which is evidenced by delving into the particles generated during conductor clashing experiments carried out in both real networks and a laboratory setup. This study offers insights into conductor clashing events and their parameters, which can contribute to improved electrical system protection and reliability.

Prevention and Safety

Proper safety measures and protocols are essential to prevent future conductor clashing incidents and ensure the safe and efficient distribution of electricity.

Copper Conductors

Upgrading existing aluminum lines with copper conductors offers enhanced performance. Copper conductors provide a superior solution, although they come at a slightly higher cost. Additionally, the sturdier support structures required for copper conductors ensure increased safety and durability.

Conductor Spacing

Increasing conductor spacing reduces the risk of the conductors clashing with each other since the distance between them is greater. Isolating the conductors not only improves safety but also promotes a more organized and efficient distribution system.

Alloyed Aluminum Conductor

Developing an alloyed aluminum conductor with reduced ignition potential represents an innovative and cost-effective solution. This alloyed conductor has the potential to eject safe, low-temperature droplets, ensuring safer operation without compromising on expenses.

Aerial Bundled Conductor (ABC)

Upgrading existing aluminum lines with aerial bundled conductor (overhead power lines using several insulated phase conductors) offers a comprehensive solution to the conductor clashing issue. This approach eliminates the potential for conductor clashing due to each conductor having its own insulating sheath (protective covering). [7][9][10]

References

  1. ^ a b c d e f g Ramljak, Ivan; Majstrovic, Matislav; Sutlovic, Elis (2014-05-05). "Statistical analysis of particles of conductor clashing". IEEE: 638–643. doi:10.1109/ENERGYCON.2014.6850494. ISBN 978-1-4799-2449-3. {{cite journal}}: Cite journal requires |journal= (help)
  2. ^ a b Sutlovic, E.; Ramljak, I.; Majstrovic, M. (2019-06-01). "Analysis of conductor clashing experiments". Electrical Engineering. 101 (2): 467–476. doi:10.1007/s00202-019-00790-0. ISSN 0948-7921.
  3. ^ "Asset Health Management". Neara. Retrieved 2023-10-19.
  4. ^ a b c d Sutlovic, E.; Ramljak, I.; Majstrovic, M. (2019-06-12). "Analysis of conductor clashing experiments". Electrical Engineering. 101 (2): 467–476. doi:10.1007/s00202-019-00790-0. ISSN 0948-7921.
  5. ^ Russell, B. Don; Benner, Carl L.; Wischkaemper, Jeffrey A. (2012-04-14). "Distribution feeder caused wildfires: Mechanisms and prevention". 2012 65th Annual Conference for Protective Relay Engineers. IEEE. doi:10.1109/cpre.2012.6201220.
  6. ^ Department of Consumer and Employment Protection Government of Western Australia (2005-05-20). "ELECTRICAL INCIDENT REPORT" (PDF).
  7. ^ a b Blackburn, T.R. (1985). "Conductor Clashing Characteristics of Overhead Lines" (PDF).
  8. ^ Russell, B. Don; Benner, Carl L.; Wischkaemper, Jeffrey A. (2012-04-10). "Distribution feeder caused wildfires: Mechanisms and prevention". 2012 65th Annual Conference for Protective Relay Engineers. IEEE. doi:10.1109/cpre.2012.6201220.
  9. ^ Rowntree, Gregory W.G. (December 1991). "Aluminum Conductor Clashing" (PDF).
  10. ^ Elkateb, M. S. (1983). "The Behaviour of Overhead Conductors Under Short-Circuit Conditions".