Methods of Protection
The cornerstone of Pepro’s enclosure technology is the principal of the Faraday Cage. According to this principal, the charge on an object is driven to its outermost surface. Pepro has designed its products to do just that and to dissipate any charge while it is resident on that outermost surface. In this manner, all sorts of currents, charges, and interference (e.g. lightning, RFI, EMI, etc.) are confined to areas that will not affect the sensitive, digital equipment inside.
Pepro accomplishes this feat with its design that uses 3/16” thick aluminum alloy plating, which is both an excellent electrical conductor and high strength structural material, as well as being relatively maintenance free. As an excellent conductor, aluminum also performs very well as a RFI shield. This design adheres to the Faraday Cage principles and works by building up the charge on the outside surface, whenever an event like a lightning strike occurs, which establishes an eddy current field around the enclosure. This field repels the magnetic field that is created by the rise in potential difference between the enclosure and the earth (ground). This potential is created by the build-up of charge on the enclosure as a result of the event. Thus, the presence of one (e.g. the charge from the lightning strike) creates a repulsive field that is proportionally as strong, and the two quickly cancel each other’s effects, leaving only a manageable, residual charge.
Any enclosure can still be susceptible to threats such as lightning and RFI, even if the shell is made to be an effective shield. Any port, entry, or through-hole in the enclosure offers these threats an avenue to affect equipment inside. Practically, that means that power supply lines, grounding cables, antenna cables, vents, doors, and air conditioning fittings, to name a few, pose a dangerous threat, even to shielded enclosures. The solution is to make the material passing through the opening—the fittings, cable, etc.—an effective part of the shell of the enclosure. In that way, any charges or EMI threats traveling along the connections are diverted to the shell, rather than allowed to enter the enclosure.
Pepro has addressed this problem with their Cable Entry Gland System. This product makes the outer surface of any cable or media entering the enclosure (where RFI, EMI, etc. currents will travel) an effective part of the enclosure. This is done with a unique, patent-pending system that diverts any unwanted current. Laboratory tests have proven this system alone to be 300% more effective than the current cable entry gland technology in use. This product can be used in conjunction with any shelter or enclosure, including ones already deployed. Thus, existing equipment can be upgraded or “hardened” through a retrofit. Hence, protection at many shelters or enclosures currently in service could be substantially increased for a moderate cost, but with a large potential savings in equipment replacement cost and maintenance.
On the other hand, the Cable Entry Gland is also an integral part of all of Pepro’s engineered enclosures. These enclosures are designed to maximize the Faraday Cage principles mentioned above. Pepro markets them under the following names: Fly-In, Walk-In, Commander, Brave and Scout.