Overview

Problem: 

In spite of the best surge protection and grounding practices, rural electronic sites recurrently experience lightning related damage.  Often the surge protectors are not damaged and the grounding resistance is 5 ohms or less. 

The International Lightning Research Center at the University of Florida conducted studies between 2002 and 2005 to find an answer.  Their experimental facilities direct lightning ground strikes on test sites so instrumentation can record the results.  The studies found two surprising conclusions:

1.  Grounding sytems are very effecient at very low and high lightning frequencies, but resist conduction of low frequency lightning energy.

 

2.  The low frequency lightning energy is forced on to the power circuit that is bonded (via surge protection) to the grounding system.  (All surge protectors are bi-directional devices and shunt energy in either direction to the lower potential.)  A parallel path to lower potential ground is created that impresses high voltage on the electronic circuits.

 

Solutions ?

1.  More grounding can not reduce the inductive reaction to low frequency lightning energy

2.  Surge protection cannot be redesigned to conduct in only one direction, and

3.  Opening the AC power circuit eliminates the parallel fault path: current cannot flow over an open circuit.  Operations are not interrupted, communications safely continue on the resident battery or generator power until the threat passes.  AC power is automatically re-connected.

 

Lightning Shield detects threatening lightning before the ground strike occurs, pre-empts the threat by opening the AC circuit, and automatically reconnects AC after the threat subsides.  Opening the AC circuit before a lightning strike also provides complete protection against flash-overs on the AC service. 

In the event of a power outage Lightning Shield open circuits the AC service and does not re-connect until the power normalizes within user prescribed thresholds.  Power recovery transients and in-rush currents are prevented.

Lightning Shield is a simple solution that assures high network reliability.