Epoxy Coating as a Novel Method to Prevent Avian Electrocutions and Electrical Faults on Distribution Pylons with Grounded Steel Crossarms

Simple Summary

Electrocutions on power lines are killing birds world-wide and causing population-level effects in some species. Distribution pylons constructed of grounded materials like steel are particularly dangerous because separations between the energized and grounded components are minimal, so even small birds can be electrocuted. To explore a potential mitigation measure for steel crossarms, we coated them in glass flake epoxy (GFE), a relatively non-conductive material. We then installed coated crossarms on a line known to have frequent faults (leaking electrical power), where many of the faults had previously been implicated in avian electrocutions. Thus, we used faults as a proxy for electrocutions. We found that replacement of 24% of untreated crossarms (crossarms without epoxy coating) with GFE-coated crossarms correlated temporally with a 28% decrease in faults in a 20 kV distribution line. The decreased fault rate was particularly stark during the avian breeding season when birds can be particularly vulnerable to electrocution, supporting our use of faults as a proxy for electrocution risk. Future research should evaluate electrocution risk directly without using faults as proxies. Nevertheless, GFE coatings have potential conservation benefits on grounded pylons but require additional research to avoid the use of faults as proxies, and to confirm long-term durability and effectiveness.

Abstract

Electrical faults caused by power escaping electric systems can lead to power outages, equipment damage, and fires. Faults sometimes occur when birds perched on power structures are electrocuted. Distribution power lines supported by concrete and steel pylons are particularly fault-prone because small separations between conductors and grounded components allow even small birds to inadvertently create faults while being electrocuted. Most conservation solutions focus on covering energized wires and components to prevent contact by birds and, although usually effective when installed correctly, covers can sometimes be dislodged thus becoming ineffective. Glass Flake Epoxy (GFE) is a non-conductive thermoset plastic that can adhere to steel crossarms and not be dislodged. We hypothesized that GFE-coated crossarms might reduce faults (proxies for avian electrocutions), and we conducted laboratory and field trials to evaluate that hypothesis. In the laboratory, we found a 2000 micrometer (μm)-thick layer of GFE coating that created a dielectric strength of 12.30 ± 0.21 kV, which was sufficient to prevent the formation of a phase-to-ground fault on up to 20 kV distribution lines. This should allow birds to perch on metal crossarms without being electrocuted. In field trials, we substituted 24% of a 20 kV distribution pylon’s crossarms with GFE-treated crossarms and found that doing so correlated with a 28% decrease in faults. Although we did not measure avian electrocutions directly, our findings suggest GFE coatings may offer a novel method of reducing avian electrocutions on power lines.

1. Introduction

An electrical fault (hereafter, “fault”) is any abnormal unplanned flow of electric current. Wildlife perching or climbing on overhead power systems and trees growing into power lines are frequent causes of faults [1,2,3,4]. Specifically, wildlife-induced faults can occur when birds or other wildlife, their nests, or their excrement simultaneously contact energized components and grounded components, creating a path for the flow of electric current [5,6,7]. Faults commonly occur during severe weather when precipitation, lighting, or wind-driven materials contact overhead power lines [8], or when wet birds or wet nesting materials create unintended alternative paths for electric current to flow. Faults can also occur when airborne materials such as dust or particulate pollution settle on insulators [9,10].

When faults involve wildlife perching or climbing on power structures, the animal is often electrocuted (Figure 1). Avian electrocutions can ignite wildland fires [11,12,13], cause outages [3,14,15], as well as create conservation concerns because they result in the deaths of a wide variety of bird species on every continent except Antarctica [16,17,18,19,20,21,22].

Faults are important due to the direct mortality they cause to wildlife, but that mortality may not be sufficient motivation for electric utilities to invest in preventing electrocutions. Faults can also result in power outages and equipment damage that undermine the efficiency and reliability of overhead electrical systems [1,2,6], which can be very motivating.

Pylons supporting distribution lines, which carry electrical power from substations to consumers, are most frequently associated with faults and with avian electrocutions [23,24]. The wires used in distribution systems are typically not insulated, relying instead on the elevation above ground to separate wildlife and human residents from electric power. Elevating power lines reduces risks for terrestrial species but can create dangerous situations where birds and climbing animals can be electrocuted. Electrocution risk is particularly high when distribution power systems are constructed of grounded components, such as concrete pylons and steel crossarms, because the separation between energized conductors and paths to ground can be as little as 14–18 cm [25,26]. Such small separations are easily bridged by even small birds [3,5,27,28]. Grounded configurations are commonly used in distribution systems in Europe and Asia. For example, in Western Europe, over 90% of distribution structures are grounded metal pylons supporting grounded metal crossarms [16,18,28].

Avoiding faults caused by birds and other wildlife typically relies on the installation of covers designed to prevent animals from contacting energized wires or components and is widely used globally, e.g., [27,29,30,31,32]. This is the case because reconfiguring pylons to preclude avian electrocution risk is prohibitively expensive when it is possible, and it is practically impossible when the pylons are constructed of grounded materials or support grounded equipment. The use of covers may involve accepting some unintended negative consequences. For example, because insulation physically blocks physical and visual access to the insulated component, insulation may interfere with inspection programs commonly used by electric utilities to ensure the reliability of electric systems [Kolnegari pers. obs.]. Avoiding dust- or pollution-induced faults typically relies on natural precipitation washing particles from insulators. This approach may not be as effective if covers are present. Insulation may also fail through product design errors and application errors, both of which can lead to the insulation falling off [12,23,33]. Silicon-based materials comprise the vast majority of covers in some countries [Kolnegari, pers. obs.] [28]. These can be susceptible to deterioration caused by solar exposure, windblown sand, and even birds foraging for insects beneath the insulation [34,35].

For these reasons, electric utilities in some areas may benefit from an alternative to covers if a reliable and effective alternative were available. We hypothesized that creating a novel mechanism of insulation might enable us to avoid the potential negative consequences associated with covers. The novel mechanism we developed was applying a non-conductive Glass Flake Epoxy (GFE) coating on steel crossarms (hereafter, treated crossarms) intended to prevent the flow of electric current from energized wires to grounded crossarms. We evaluated our hypothesis via a laboratory assessment of the dielectric strength of the GFE coating on treated crossarms and via quantifying the number of faults that occurred on a power line where crossarms on the line were treated with a GFE coating.

2. Materials and Methods

We conducted this study at two locations; the Niroo Research Institute of Iran’s Ministry of Energy in Tehran, Iran, and a field site crossing cereal farms and orchards near the city of Arak in the Markazi Province of Western Iran, where wildlife and dust are present. In the laboratory, we applied GFE to 2.44 m long steel crossarms used on the 20 kV distribution system at the field site. GFE is a thermoset plastic, made from liquid materials reacting to form an inert and highly crosslinked solid polymer structure [36,37]. GFE is characterized by its resistance to abrasion, chemicals, high or low temperatures, and the flow of electric current. The adhesive characteristics of GFE enable it to be applied to a wide variety of materials including metals, concrete, glass, ceramics, stone, wood, and leather. In this study, we focused specifically on a GFE produced by the Ronass Chemical Producing Company (Tehran, Iran), and we used GFE colored green so that we could easily distinguish treated (green) crossarms from untreated (metallic grey) crossarms installed at the field site.

We began by applying two 1000 μm thick coatings of GFE to crossarms 12 h apart to create a total GFE thickness of 2000 μm. We then quantified dielectric strength and adhesive strength according to protocols IEC 60060-1 and ASTM D4541, respectively [38,39]. Specifically, to conduct the dielectric test, we removed the GFE coating from a corner at one end of a treated crossarm and then attached a source electrode from a 100 kV/5 kVA transformer to that corner (Figure 2). We then attached a ground path electrode to the intact GFE near the other end of each crossarm to create a circuit that included 2000 μm of GFE coating between the energized crossarm and the ground path (Figure 2). Finally, we applied increasing voltages of alternating electric current to the circuit until the breakdown voltage occurred in the GFE. The breakdown voltage was defined as the voltage at which electricity tracked through the GFE, reducing the voltage between the electrodes to practically zero [40]. This procedure was repeated on each of 10 treated crossarms. To conduct the adhesive test, we glued a 20 mm test dolly to the coated metal surface of the 10 crossarms. After the glue had cured, we exerted a perpendicular force to the surface to remove both the dolly and the coating from the crossarms and measured the force in MPa [39].

At the field site, we replaced 430 existing crossarms with GFE-coated crossarms on a 20 kV distribution line composed of approximately 1800 pylons, south of Arak in the Markazi Province of Western Iran (Figure 2). This equates to approximately 24% of crossarms in the study area being replaced. We then recorded the numbers of faults occurring on the line each month and compared the counts of pre-installation faults to the counts of post-installation faults. Specifically, we installed treated crossarms in September and October of 2020 and then compared the pre-installation faults recorded from March 2018 to August 2020 to the post-installation faults recorded from November 2020 to December 2022. We focused on a 20 kV line because avian electrocutions are particularly common on voltages ≤ 20 kV in Iran [3,31,41], including those in our study area (Kolnegari unpub. data), as they are in many parts of Europe and Asia [3,33,42].

For analyses, we distinguished faults by month and conducted a t-test wherein we compared the numbers of faults occurring before the installation of GFE-treated crossarms to the numbers of faults occurring afterward. We limited our wildlife-related inferences to birds because there were no climbing primates or squirrels in the study area. We considered results significant at α = 0.05.

3. Results

In laboratory testing, the GFE resisted the flow of electric current up to an average of 12.30 kV (±0.21 kV;

Table 1. Laboratory test conditions for GFE-coated crossarms to evaluate potential to reduce avian electrocution risk by preventing birds in contact with energized conductors from becoming part of a phase-to-ground electric circuit.

Test	Standard	Temperature (C°)	Humidity	Replicates	Results (Mean ± SD)
Dielectric	IEC 60060-1	7.7	47.3	10	12.30 ± 0.21 kV
Adhesion	ASTM D4541	23 ± 2	35 ± 5	10	10.49 ± 0.4 MPa

) and was retained on treated crossarms up to an average of 10.49 MPa (±0.4 MPa). At the field site, there was an average of 25,882 faults per month in the 30 months before the installation of treated crossarms (March 2018 through August 2020) and only an average of 18,757 in the 26 months afterward (Figure 3; November 2021–December 2022). Data collected in September and October of 2020 were omitted from the analyses because treated crossarms were installed during those months. Thus, a 24% decrease in the number of untreated crossarms on the line correlated with a 27.5% decrease in the number of faults (t = 2.676, df = 50, p = 0.010). The decreased fault rate was particularly stark during the avian breeding season (April–October) when average monthly faults declined from 26,904 to 18,841 (30.0% decrease).

4. Discussion

We found in laboratory testing that the dielectric strength of GFE was sufficient to resist the flow of electric current in ideal conditions and that GFE adhered to steel crossarms. These findings were consistent with our expectations, given that GFE coatings are generally good insulators with strong adhesive characteristics even in harsh environments or extreme environments [37,43,44,45]. Specific to our application, we found that GFE resisted > 12.0 kV. In our study area, the distribution lines operated at a nominal 20 kV. This is the difference in voltage between the conductors. The difference in voltage from phase to ground is calculated as nominal voltage (20 kV) divided by the square root of 3, which equals 11.5 kV. Thus, theoretically, the 2000 μm thick GFE coating we applied should have been sufficient to prevent phase-to-ground faults from occurring on treated crossarms.

Our field study supported our theoretical conclusions, with a significant reduction in the number of faults recorded on the line from over 310,500 annually to about 225,100. We did not investigate the causes of these faults, but we hypothesize that at least some were likely caused by birds being electrocuted because the timing of the greatest reduction in faults correlated with avian breeding seasons (March–September) in our study area when avian activity was greatest. The timing also correlated with the dry season (April–September) in our study area when natural washing by precipitation would occur infrequently, and thus many of the faults that occurred were likely induced by contamination. Consequently, we can only conclude that the GFE coating likely reduced the occurrence of both causes of faults. Future research should incorporate investigations of the causes of faults to try to identify which causes are most effectively reduced via GFE-coated crossarms.

Although our findings were positive, they should be viewed with caution until additional research focused specifically on avian electrocutions as evidenced via carcasses can be conducted rather than using faults as proxies for electrocutions. Future research should also explore whether, during the wet season, some additional treatment is necessary to limit avian electrocutions, or whether other variables not addressed in the study, such as climatic conditions or exposure time, may have affected fault rates. Also, a challenge inherent in the strategy is that it requires treating crossarms ex situ before installation, preventing GFE-coated from being used as a retrofitting method for crossarms already in place. The approach also adds cost and complexity to new power line construction when steel crossarms are used, although these negatives are likely to be more than offset by reductions in the faults and their associated negative consequences. Another challenge is that we have collected only short-term information on effectiveness to date (26 months), but power lines are frequently used for >50 years. We do not know if the GFE coating of treated crossarms would remain durable and effective over the intended life of the line. If GFE-coating is found to have long-term durability and effectiveness, it may also be useful on other grounded components such as insulator pins and transformer’s arcing horns where avian electrocutions are also known to occur in our study area [31]. GFE-coated crossarms colored to match the surrounding landscapes or to indicate bird-friendly practices, such as using green crossarms, may also contribute to aesthetic or publication relations goals. An important aspect of this study is that it explores a novel solution to an increasingly common problem. Specifically, power lines are increasingly being constructed of concrete pylons supporting steel crossarms. These configurations provide improved durability and resiliency compared to wood configurations and are readily available in arid countries where wood poles can be unavailable, but their fault rates are higher than wood constructions because phase-to-ground separations can be reduced to as little as a few centimeters at each insulator. Fiberglass and other non-conductive composite pylons and crossarms offer another solution, but expense and engineering concerns limit their use in some situations [46]. For those reasons, concrete and steel pylons with steel crossarms are likely to continue to be used by many electric utilities worldwide.

In conclusion, we believe the epoxy coating we applied as a novel method to prevent avian electrocutions and electrical faults on distribution pylons with grounded steel crossarms likely was effective; however, future research is needed to transition the correlative findings reported here to causative findings supported via carcass searches.