User:This is for writ2e/sandbox/Conductor Clashing

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 with one another, leading to disturbances in the flow of electrical current. The contact between the conductors generates heat, resulting in the melting and vaporization of the conductor material. The buildup of pressure from the vaporized metal can transform into small, high-temperature molten metal particles, referred to as “sparks”. The sparks may then be carried away by the wind, potentially landing on nearby vegetation. Frequently, the sparks that land on vegetation start fires that occasionally grow and spread to produce wildfires that cover acres of surrounding areas.

Proper isolation or spacing of conductors is essential to prevent clashing and ensure the safe and efficient distribution of electricity. Understanding the process of the reactions and under what circumstances this event occurs can help prevent future incidents involving conductor collisions.

Mechanism

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, highlighting the mechanisms of conductor clashing.

Heat and Vaporization

When two conductors of a power line clash, a 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.

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.

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 ${\ce {Al2O3}}$ (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.

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.

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.

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.

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.

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.

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.

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, 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.

Experiments and Results

The following section outlines experiments aimed at looking into the generation of particles, in terms of size, number, and behavior. Looking at other conductor materials such as aluminum and copper and how short circuit current, wind speed, arc duration, and fuse rating affect the results. These experiments aim to provide insight about the phenomenon and help find solutions to create protocols to maintain safety when conductor clashing occurs.

Experiment 1

The first experiment focuses on Al/Fe conductors with a 25/4 mm² cross-sectional area and a 125A rated current. 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 current equation :

${\rm {I}}_{{\rm {K}}2}^{\prime \prime }={{{\rm {c}}\cdot {\rm {U}}_{\rm {n}}} \over {{\rm {Z}}_{(1)}+{\rm {Z}}_{(2)}}}={{{\rm {c}}\cdot {\rm {U}}_{\rm {n}}} \over {2{\rm {Z}}_{(1)}}}$

Where

${\rm {Z}}_{(1)},{\rm {Z}}_{(2)}$is a positive and negative sequence of short circuit impedance(measure of opposition that a circuit

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

c is voltage factor

${\rm {U}}_{\rm {n}}$ is nominal system voltage

Using this equation, the line-to-line current was calculated to be 1700A.

The following tables show the number of particles, means of diameter of particles in mm, standard deviations, and coefficients of skewness obtained in experiments in the live network and in the laboratory.

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	200	300
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 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 (the current-carrying capacity of the fuses) in the live network, while skewness (a measure of the distribution's shape) coefficients decreased. On the other hand, there was an inverse relationship between the lab fuse and the skewness coefficient, whereby higher fuses 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.

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.