When a cow drops dead in a pasture during a thunder storm, it may not be because they have been struck by lightning. A lightning strike in the vicinity (up to several miles away) can cause too much potential difference (read: voltage) as it passes between their front and back legs.
Without proper protection, an indirect lightning strike can have a similar effect on the expensive electronic devices in your home. The solution lies in installing proper overvoltage protection. It will help you prevent the early breakdown of sensitive electronic equipment or the shortening of its useful lifetime.
The difference between lightning and overvoltage protection
European homes are seldom protected against direct lightning strikes. Homes that are located on high-risk locations (e.g. the top of a mountain or hill) are generally equipped with external lightning protection (copper conductors and wires to the earth). In these cases, internal lightning protection is required from the very beginning of the electrical installation process.
Overvoltage protection prevents damage to electrical installations from indirect lightning strikes as well as surges from other sources, such as motors. Peak voltages are weakened to an acceptable level for most electrical appliances. When internal lightning protection is installed, it needs to be followed up with appropriate overvoltage protection to decrease the lightning protection’s remaining peak voltage.
Indirect lightning strikes and their consequences
Certain sensitive electronic devices can break down due to indirect lightning strikes in the vicinity (even over a mile from the home). You will no doubt notice that the device is broken, but without knowing the cause. However, more commonly the device will not break down immediately. The sudden voltage peak will have hit the electronics just hard enough to decrease the remaining lifetime of these components. Hence, your devices will not last as long as expected.
What about Insurance?
Direct lightning strikes generally cause severe damage to your home. In most cases, this item is part of your home insurance, and the damage will be reimbursed. It is easy to prove that the damage was caused by a direct lightning strike.
However, damage is much more difficult—and in most cases even impossible—to link with indirect lightning strikes. You should consider investing in overvoltage protection as a one-time insurance policy. In many cases, investing in overvoltage protection can lead to a lower home insurance premium.
What needs protection and how?
All cables entering the home need protection. In concrete terms, that means the cable for the 230V grid tension, the coax cable and/or telephone cable for television, satellite and the internet. Manufacturers have developed specific products for each of these subsystems. Overvoltage protection is installed at the beginning of the equipment circuitry, usually in the switchboard. This is known as medium protection and consists mostly of modules that can be plugged into a DIN rail. A green or red window signals whether the protection is operational or needs replacement.
Most devices are connected to both the mains supply and the coax or telephone system. Hence, it makes no sense protecting only one of the subsystems. Protecting the 230V cables will save the television, but there will be overvoltage in the coax part if this is not protected as well.
In the case of medium protection, the remaining peak voltage can still amount to 275V. For certain devices with sensitive electronic components (e.g. TVs, audio equipment, computers) this is still too much. In these cases, you can install additional individual 'fine' protection, mostly in the form of a multiple socket to be plugged into the wall socket. The multiple socket will feed the device that needs protection. For appliances needing multiple connections (e.g. 230V, telephone, coax, LAN network), there are fine protection devices into which various cables can be plugged.