Static Shield - Overhead Ground Wire Lightning Protection

Explaining the value of overhead ground wire and how it works is vital for understanding the importance of Bekaert's manufacturing process for power line and telecom operations.

A static shield is part of a grounding cable strung above the power and data lines. When lightning strikes, the overhead ground wires redirect that energy along their cores, then send the strike into the ground. This grounding method keeps the electricity from causing damage to the rest of the electrical equipment.

Overhead ground wires for protection of overhead power lines span the distance between support towers. They run above power and data transmission lines, and they are grounded at regular intervals. Current travels differently on static wire than it does through data and power lines. 

However, the primary purpose of OGHW is intercepting lightning strikes before that electricity reaches the transmission lines below. Ground wire manufacturers use steel alloys to produce these elements, as static wires only carry current when struck by lightning. 

That interference protects the power and data lines. This protection is so crucial that most modern systems have two overhead ground wires instead of a single static wire. 

Once the current travels along the static wire, it looks for the nearest place it can discharge energy. The overhead ground wire carries the current to the next tower, where the grounding guides the lightning discharge energy into the earth. The discharge minimizes or eliminates damage to the power lines and equipment while helping to prevent power outages.

Several factors can affect the way an overhead ground wire works. One of the most common complications is soil resistance. When the footing resistance (between the tower foot and the earth) is high, the current cannot enter the ground. To discharge the building energy, the current completes a back flashover. Preventing back flashovers involves lowering tower foot resistance with counterpoises and driven rods.

Note that overhead shielding wire has no impact on switching surges. 

Some of the most critical challenges for ensuring adequate protection of transmission lines with static shielding include: 

• Strength: Static shield wires must have the required mechanical strength to shield the conductors from direct lightning strikes. 
• Placement: Shield wires must always be above and parallel to the line conductors, meaning the length of the ground wire should be the same as the transmission line.
• Clearance: There must be adequate clearance between the transmission lines and ground wires to prevent flashovers. To reduce the chance of an insulator flashover, decreasing the voltage at the top of the tower is critical, as the ground wire alone cannot provide adequate protection.
• Resistance: Tower footings must have low resistance levels to allow the lightning discharge currents to travel to the ground safely and quickly.

One of the core responsibilities for ensuring shield wire performance is performing annual inspections along the entire length of the overhead lines. Examples of the system components that require assessments include the foundations, earthing conductors, control joints, the locations of the phase wires and the tower structures. Technicians should also ensure the towers are free from debris and animal nests while checking that all wires are at a safe distance from trees, vegetation and physical structures. 

In this industry, the safety and quality of our products are standard. Bekaert stands apart from the competition because our U.S.-based manufacturing capabilities and dedicated support services always exceed client expectations. The advantages of choosing Bekaert as your overhead static shield wire supplier include the following:

• Solid partnership: When you order steel wires from us, you join a partnership. Our clients enjoy our flexibility and capabilities as a manufacturer. Regardless of what shape or characteristic you request, our teams can meet your needs. 
• Experience: We've been a manufacturer for over 130 years, serving clients across North America and worldwide. We understand the utility industry and work to make your operations safe, cost-effective and sustainable.
• Expert advice and support: Our knowledgeable staff and comprehensive technical support services provide industry-leading customer service. We have the teams and solutions to help you get the most value out of your equipment.