Modern Lightning Protection for Radio Facilities: AC Power Lines

Lightning strikes through AC power lines are the most common cause of damage to telecommunication equipment. Despite extensive RF and telephone line protection, many facilities overlook AC line defense, often due to limited product availability or misunderstanding of proper protection methods.

Why AC Power Lines Are Vulnerable

Power lines are highly exposed, often spanning miles overhead. A single lightning strike can travel across these lines, seeking the nearest ground point and damaging all connected equipment. Sensitive electronics are particularly at risk.

Effective AC Line Protection

The best defense is to install protection at the service entrance of the AC power line, before the surge reaches internal wiring. Plug-in surge protectors, commonly found in stores, provide little protection since they are too far from earth ground and activate too late to prevent damage.

Service Entrance Protectors – Key Benefits

  1. Whole-Building Protection – Installed at the entry point, these protectors safeguard all connected AC devices.
  2. Early Surge Interception – They stop high-voltage surges before they enter the building's wiring.
  3. Ground Proximity – Service panels are typically near earth ground, allowing for short, heavy-gauge grounding wires for better performance.

Best Protection Methods

  • Hybrid Surge Protectors – Combining Metal Oxide Varistors (MOVs) and Gas Discharge Units (GDUs) offers optimal defense:

    • MOVs – Fast response, dual polarity, high power capacity (especially when paralleled), and affordable.
    • GDUs – Faster attack, higher power handling, but costlier and sensitive to AC line conditions.
  • Combination Approach – Using MOVs for small surges and GDUs for large wavefronts ensures comprehensive protection. This hybrid method prevents GDUs from failing or shorting.

  • Remote Equipment Protection – For equipment more than 100 feet from the service entrance, install MOVs directly in the equipment cabinets to prevent internal surges. Their distributed capacitance also provides RFI protection.

Additional Tip

Always connect the AC neutral ground to the facility’s bulkhead grounding system to distribute lightning energy more effectively, minimizing potential damage.

Proper AC line protection ensures long-term safety for your facility, reducing downtime and safeguarding sensitive equipment.