Protecting wildlife from electrical assets — and vice versa

At a time when ESG (environmental, social and governance) principles are of increasing relevance to modern businesses, biodiversity risk is a key consideration for industry.

Electricity distribution is no exception. While overhead lines are cost-effective and less carbon-intense than underground cable, the exposure of high voltage to the environment introduces a risk of electrocution to wildlife. Managing that risk is the prerogative of electricity distribution businesses, preserving their social license to operate and allowing them to deliver an essential service in a safe and reliable manner.

Fortunately, outages caused by wildlife interaction with assets are largely preventable and are accounted for by modern switchgear manufacturers. Organisations such as NOJA Power provide mitigation techniques to both reduce biodiversity risk and improve asset reliability.

This article explores four key techniques for mitigating biodiversity risk through technical specification of switchgear.

The impact

Fundamentally, mitigating biodiversity risk is accomplished by introducing barriers between exposed high-voltage conductors and wildlife contact. Wildlife that bridges the gap between an earth plane and a high-voltage terminal introduces a short circuit, causing power to flow through the short circuit.

Faults that occur on switchgear due to wildlife incursion can destroy the asset. Barrier techniques reduce the likelihood of a short circuit occurring, resulting in less biodiversity risk, less outage risk and improved asset reliability.

Since most mitigation techniques are highly cost-effective, NOJA Power Switchgear’s installation philosophy is that animal guards should be the de facto standard for installations.

Bird guards

Bird guards are electrical insulating covers for the exposed terminals of a high-voltage asset. These are installed after the overhead lines are terminated onto the equipment, providing a mechanical barrier between the high-voltage terminal and the outer environment.

While they are not considered a safe isolation for lines operators, they reduce the likelihood of animals bridging the gap between the earthed asset, getting over the bushing sheds and contacting the high-voltage lines or terminals.

Bird guards are available for all terminal types, including surge arrestor terminals and voltage transformer terminals. A comprehensive mitigation strategy includes coverage of all terminals. As an example, NOJA Power switchgear has bird guard types for all exposed terminations on a typical high-voltage installation, for load break switches, reclosers, surge arrestors and voltage transformers.

Covered conductor cable tails

It is industry practice for the connections between the overhead lines and a pole-mounted asset to be made using a conductor that is covered with an insulating medium, such as XLPE.

Like bird guards, this covered conductor approach does not provide operator-safe insulation, because it lacks an earth screen — but it does provide major risk mitigation for animals bridging the gap between conductors or a conductor and the earthed asset.

This is a common source of confusion for newcomers to switchgear specification, as the cable tail insulation level does not need to match the insulation requirement of the asset. For example, a 38 kV installation may only need cables insulated to 11 kV. The cables are not being used as a working isolation for operators; instead they only provide a mechanical barrier against animal contact.

Installing cables insulated to full network voltage is not practical in an overhead connection scenario, but the 11 kV covered conductor is generally sufficient for most applications and provides appreciable mitigation for biodiversity risk.

Image credit: iStock.com/ Peter_Virag

Animal climbing guards

Animal climbing guards are a metal sheath installed near the base of the power pole installation. This sheath reduces the likelihood of animals successfully climbing the pole and contacting high-voltage terminals.

These are a simple intervention asset that can be installed in both new and legacy installations.

Cattle guards

In some regions, local OH&S regulations encourage installation of switchgear controllers low enough on a power pole to remove the need for a ladder. This approach reduces fall risk for operators, but introduces a risk of larger animals contacting the equipment.

Bringing the controller down to pedestrian height in rural areas can make the controller become a bovine scratching post — leading to damage of the control cables or communications accessories. To combat this, a cattle guard is mounted on the base of the control cubicle, providing mechanical protection for the cable entry points to the controller.

Conclusion

Biodiversity risk is a key consideration for any organisation reliant on managing electricity distribution assets. The risk considers both asset reliability outage risk and the impact on wildlife. Both these aspects impact the bottom line, whether through direct loss of productivity or through social licence to operate.

Luckily, mitigations of this exposure are cost-effective, reliable and easy to implement, and modern switchgear manufacturers can supply equipment to address the risk.

Given the minor relative cost to an equipment installation, NOJA Power recommends that animal guards are the default configuration for any installation. For more information, visit www.nojapower.com.au.

Top image credit: iStock.com/daleclarkphotography