How to Protect Your Solar Power System from Lightning

Lightning and its related static discharge is the number one reason for sudden and unexpected failures in photovoltaic solar electric power and water heating systems. It is not necessary that the panel sustain a direct strike to cause damage to the sensitive electronic components attached to the system, such as the inverters, the controls, or even the appliances plugged into the system. The storm can be miles away and still induce high voltage surges in the wiring. The best way to protect your photovoltaic solar electric system from static discharge is by installing a proper grounding system. This part of installation is often overlooked by many solar electric power owners and installers.

Grounding means connecting part of your solar electrically system structure and wiring directly to the earth or ground. Grounding your system offers 4 benefits; it drains off accumulated charges, making your system less attractive to lightning, if lightning should strike your unit your ground provides a safe path for the discharge to follow into the ground instead of your systems wiring, it reduces your system's shock hazards, and reduces electrical radio hum generated by the high frequency devices attached to the system.

The type of soil you will ground your photovoltaic solar electric power system to will help determine the type of ground rod you should use. The metal cold water pipes (never use hot water pipes) that are buried in the ground are a good ground source. If there is a ground well installed near you system, on the property, be aware the iron well casing make super ground rods. In moist conditions, an 8 foot copper plated ground rod driven into the ground provides minimum protection. If the ground is dry and sandy, several rods should be installed at least 10 feet apart. If your site is rocky and you are unable to drive your ground rod deeply, bury 150 feet or more of bare copper wire in an area that tends to be moist. The intent is to create as large an electrical contact as you possibly can with the earth to serve as your ground.

Once your grounding source has been installed these are the components of your photovoltaic system you should connect to the ground system; connect the metallic framework that supports your photovoltaic array and its wiring to the ground rod. Ground the negative side of your power system and check for leakage. Correct any that you find. Ground the alternating current generator and inverter frames. Surge protection devices are recommended to include additional protection for appliances connected to the system, just as a safeguard. You should be able to properly ground you photovoltaic solar electric power system yourself, however, if you are uncertain of your abilities, hire an electrician. Remember, your ground system is only as good as its weakest electrical connection, so be sure your ground system and all connections are secure and installed correctly.

Resource: Grounding And Lightning Protection For Solar Electric Power Systems - Backwoods Home Magazine - October, 1992