Tech Forum

Their is also a whole house surge-protector from Square D and other electrical panel suppliers for less than $150. They hook up to both sides of the 220 volt buss bars. Check you panels maker site. I purchased one a number of years ago and it stopped electrical line spikes. With a cable and phone line surge-bar I have been lucky and keeping my replacement money in the bank.

The simplest solution to lightning-induced surge protection is to use a commercially available surge-protected outlet strip. There are numerous sources for these items, and you may even find a suitable device at your local hardware store.

The important thing to understand is that a lightning strike conducts huge oscillatory currents. A varying electrical current will generate a changing magnetic field, which in turn will induce superimposed voltages in nearby conductors -- including service drops from the utility pole to your house (e.g., electrical power, TV/internet cable, and telephone). Such surges can be induced both line-to-line and line-to-ground in the electrical power service drop (and for balanced-line applications such as telephone). Properly-designed surge suppressors provide both line-to-ground and line-to-line protection for such circuits.

Surge voltages induced line-to-ground arise because such devices often are connected to more than one source of surge voltage: For example, your television set is connected to utility power and also connected to the TV signal cable. Likewise, your computer may be connected to utility power, to a cable from your internet service provider, and to a telephone cable (for fax service).  Unless these cables/wires are all run together throughout the house (and this practice is discouraged due to the possibility of capacitive cross-coupling), one or more loops exist, and within each loop, the surge voltage induced by the lightning strike is a direct function of the areas enclosed by the loop.

It follows that effective surge suppression can only be accomplished by feeding all of the incoming electrical services through what is called a "surge-protective window". In such a structure, surge suppression elements such as metal oxide varistors (MOVs), avalanche diodes, or gas tubes can clamp impulse voltages to a common reference point plane which in turn is connected to earth ground. This can be effected by using a surge-protected outlet strip that also incorporates protection for telephone and cable lines. Typical examples of this all-inclusive surge protection are devices available from Belkin (e.g., www.belkin.com/us/BV112234-08-Belkin/p/P-BV112234-08/) and Tripp-Lite (e.g., www.tripplite.com/av-home-theater-surge-protector-isobar-10-outlets-8-ft-cord-3240-joule-3-line-coax-ethernet-tel-network~AVBAR10/).

All cables exiting the surge suppressor block should be run together wherever possible, secured periodically by twist-ties or other means.  This method ensures that negligible induction areas exist into which surge voltages can be introduced. Capacitive-coupled interactions are no longer a problem because any prior surge voltages have already been stripped from the cables by the surge suppressor block.

Please note that the protectors identified above are "Cadillacs" because they provide surge suppression for all common power and media transport wiring. Sometimes just a simple one-outlet surge suppressor will do the job — or, for example, a single-outlet suppressor with built-in telephone line surge suppression, both at significantly lower cost. I even use single-outlet surge suppressors to protect my coffee maker and washing machine because each of these devices contains electronic modules that are expensive to repair.

The important consideration is to maintain the "surge protective window" approach to the problem as outlined above.

Lightning protection is a complex issue, including home entrance cable protection, bonding of large metallic structures, and even grounding of rain gutters and downspouts. A good place to start is a free PDF from www.lightningsafety.com/nlsi_lhm/IEEE_Guide.pdf. Because a lightning bolt can pack a 500 MJ wallop, far beyond any MOV rating, surge protectors are not protection against a direct strike, but they do help limit inductive surges (e.g. lightning hitting a tree nearby, inducing a current in house wiring). In brief, running a hefty ground wire from gutters, external antennas etc. to an effective ground in conductive soil is the first line of defense.

MOV surge suppressors have saved my PC and appliances from one damaging surge, though, as shown by blown internal fuses and smoking MOV's!