Solar Lightning Arrestors

Lightning is a common cause of failure in off-grid solar systems. Most often damage does not occur as a result of a direct hit, but from nearby hits. A nearby hit can induce thousands of volts into a solar system if not protected. A ground hit can also spread out and travel into buried conductors, such as buried cables and pipes. Grounding is the most fundamental technique for protection against lightening damage. A lightning surge cannot be stopped, but a direct path to ground that bypasses equipment can be accomplished. In addition to grounding, specialized surge protection devices are recommended for sites that are on high ground in severe lightning areas, that are on dry, poorly conductive soil or that have wire runs longer than 100 feet.
Lightning arrestors are designed to absorb voltage spikes caused by lightning, allowing the surge to bypass wiring and equipment. They are connected to wires just before they enter any part of the solar system. Most wires running more than 100 feet will experience lightning-induced transients at some time. Because the transient is usually initiated at some point between the two ends of the wire, most applications will install a lightning arrestor just before the wire enters the equipment to be protected. The lightning arrestor is also connected to ground and routes the energy from the over-voltage transient to ground. Lightning arrestors are made of various voltages for both AC and DC.
4 things to consider when selecting lightning protection for coax connected devices:
- Frequency range. All lightning protectors offer a specific frequency range that they protect against. For example, a protector may offer 698 megahertz all the way up to 2.7 gigahertz of protection.
- Connection type. The most common connector is N female, however, there are also N male, TNC or many other different types of connections. In some cases the protector offers bidirectional protection so the input and output can be reversed.
- DC pass vs DC block type protectors. DC pass type protectors are used if power is needed at the antenna tower to power a particular device. It allows low voltage current to pass through the center pin of the coax cable to power the device. If no power is needed at the antenna tower, a DC block type protector is used, which would not allow any current to pass through the center pin of a coax connector.
- Technology type. The most common and cost effective type of technology is gas tube protection. In most cases, it will last about five years. One thing to consider with gas tube protectors is that they can build up static electricity over time, and if that static electricity discharges, it can damage equipment. The second type of technology is coil inductors. Coil inductors offer very reliable protection against lightning strikes and heavy surges, as well as not degrading over time. They only need replacement with significant lightning strikes. There is no threat of static buildup with a coil inductor protector. The only real disadvantage of using coil inductor technology is the cost. Typically, they are about 30 to 40% more expensive than gas tube technology.