Harrison School District 2- Lightning Strikes Connecting Trees to Light Poles
Our client challenged us with an insurance claim from a lightning strike that occurred in the parking lot of one of their schools. The strike hit a tree and transferred to one of their light poles. This caused a chain of events, blowing out the underground power from that pole to the next one in line. In addition, the strike blew out about 8 lamps within other nearby poles.
We were able to trench and replace the burnt line, as well as replace the burnt out lamps.
Functional light poles and lamps. Lightning Strikes: The Potential Path from Trees to Light Poles
Lightning strikes are powerful natural phenomena that can cause significant damage and pose a threat to people and infrastructure. While lightning often seeks the path of least resistance, it can strike objects that are not necessarily the tallest or highest in the vicinity. One such scenario is when lightning travels from trees to nearby light poles, potentially causing damage to both natural and artificial structures. In this article, we will explore the physics behind lightning strikes, examine why trees can become susceptible to lightning, discuss the risk lightning poses to light poles, and highlight potential mitigation strategies.
Understanding Lightning Strikes
Lightning is a discharge of electrical energy that occurs between a positively charged area and a negatively charged area within a thunderstorm cloud or between the cloud and the ground. When the electrical potential difference becomes large enough, a lightning bolt is triggered to equalize the charge. Typically, lightning seeks the path of least resistance, which is often determined by the presence of conductive materials, such as metal structures or tall objects.
Trees and Lightning
While tall buildings and structures are commonly associated with lightning strikes, trees can also attract lightning due to their height, moisture content, and branching structure. Tall trees in open areas can serve as natural lightning rods, attracting the electric charge passing through the atmosphere. The moisture within the tree helps to conduct the electrical energy, providing a path for the lightning to travel. Additionally, the sharp tips of branches and leaves can facilitate the ionization process, further increasing the likelihood of a strike.
Risk to Light Poles
When lightning travels from trees to nearby light poles, it can pose a risk to both the natural and artificial structures involved. The electrical current from the lightning strike can cause significant damage to the tree, including splitting the trunk, stripping bark, and even igniting fires. As the lightning seeks a path to the ground, it may encounter nearby light poles, which can act as conduits for the electrical discharge. The metal structure of the pole provides a low-resistance pathway for the lightning, potentially resulting in structural damage, electrical system disruption, and even fire hazards.
To reduce the risk of lightning strikes from trees to light poles, various mitigation strategies can be employed:
1. Lightning Protection Systems: Installing lightning rods or air terminals on tall trees can help divert the lightning strike away from the tree and towards a grounding system. Similarly, installing lightning rods on light poles can provide a designated path for the electrical current to dissipate safely.
2. Grounding and Bonding: Ensuring proper grounding and bonding of both trees and light poles can help minimize the damage caused by lightning strikes. Grounding systems disperse electrical energy into the ground, while bonding connects conductive materials together, reducing potential differences and equalizing charges.
3. Surge Protection Devices: Installing surge protection devices (SPDs) can safeguard against power surges caused by lightning strikes. SPDs provide a barrier between the external electrical event and the electrical system, diverting excess energy and protecting sensitive equipment.
4. Tree Trimming and Pruning: Regular tree maintenance, including trimming branches away from utility lines and light poles, can help reduce the risk of lightning strikes. Pruning practices that remove dead or weakened branches can also decrease the likelihood of lightning attraction.
While lightning strikes from trees to light poles are a potential hazard, implementing appropriate mitigation strategies can help reduce the associated risks. By understanding the physics of lightning, addressing tree vulnerabilities, and employing protective measures, we can enhance safety and protect both natural and artificial structures from the destructive power of lightning.