Overview

Problem : Solution : Results

Problem

In spite of the best surge protection and grounding systems, rural electronic sites regularly experience service and equipment failures during lightning storms.  In the absence of a technology solution, replace and repair of card packs and rectifier modules has become accepted practice for many companies.  Management systems are typically not designed to track all the equipment failures or the cumulative expense.  However, the chronic sites that present significant service failures and repair expense do get management's attention.  Solutions may include retrofitting the site with enhanced grounding or relocating the site away from a suspicious substation or overhead transmission line at considerable expense.  These measures may or may not be effective, suggesting the underlying problem is not being addressed.

Studies by the Lightning Research Institute at the University of Florida have recently uncovered a fundamental problem with traditional protection practices.  Grounding systems have successfully evolved from 60Hz AC fault models; however, the solution for 60Hz is not an efficient conductor of lightning energy that ranges from KHz to MHz.  This is the underlying issue for many problem sites.

GPR_Fault_PahtLightning energy is not instantly dissipated in the strike area.  High voltage gradients (Ground Potential Rise) and the resulting fault currents are propagated across the earth's suface by a ground strike.  During lightning GPR fault conditions the grounding system is momentarily elevated thousands of volts. Grounding and surge protection conduct in both directions, allowing the elevated voltage on the grounding system to seek alternative paths to a lower potential references - the utility ground.  This "back door" fault path traces through the power circuits and electronics, producing damaging voltage gradients across electronic modules and components.

 
Rural sites experience most of the lightning related damage because there is far less infrastructure to dissipate the GPR, as compared to the underground plumbing and wiring in suburban areas.  As a consequence, GPR will radiate across a much large rural area, particularly in regions with low soil conductivity (sand, limestone, granite).  Contrary to design intentions, grounded sites in a rural area may become the best attractors of GPR as lighnting seeks the easiest path to the best grounding.

 

Solution

LS_SolutionLightning Shield is the technology that has been developed based on this new understanding of lightning GPR.

Lightning Shield detects the impending lightning threat and opens the utility circuit to eliminate the fault path through the electronics. The technology mimics "pulling the plug" on your home electronics as the storm approaches.  Fault current can not flow across the open circuit; the lightning energy is forced to dissipate in the site grounding system.

During this protected isolation the site electronics continue to safely operate powered by the battery plant or stand-by generator. Lightning Shield automatically restores the utility power after the trheat has passed.

LS200ProductShotThe Lighnting Shield systems provide a few technology improvements on "pulling the plug":

  • Lightning storms are detected approaching from a distance, or from the formation of the first lightning channel in the immediate vicinity, in adequate time to isolate the electronics from GPR.
  • The detection sensitivity is adjustable to accommodate different soil conditions and seasonal variations.
  • Protective isolation is maintained until the threat has passed for a specified time period (adjustable) to minimize latent exposure.  Lighnting has a lateral reach of over 5 miles.
  • The utility power voltage is also monitored by a window comparator with selectable high and low thresholds.  A sure or sag activates isolation until the threat has passed for a specified time period (adjustable).  Power is not restored to the electronics until it normalizes within the window thresholds, assuring the electronics are not exposed to power recovery transients.
  • Visual display and relay alarms provide notification of threat events and system status.
  • No maintenance is required.  You can install it and forget it, OR ...
RM_General_Screen_-_WebRemote Manager complements Lighnting Shield with control and test capabilities that significantly enhance site management productivity:
  • Lightning Shield status is monitored and GPR protection may be remotely tested.
  • Protection parameters (detector sensitivity and AC thresholds) may be remotely adjusted.
  • Threat events and response may be remotely monitored and logged for download.
  • The battery plant is monitored and may be remotely tested for capacity under actual load.
  • The standby generator may be remotely activated.



Remote Manager communicates using a browser interface via telephone dial-up, Ethernet data port and wireless router.  The telephone modem provides IP connectivity with any browser enabled device.  The data port and router provide IP and SNMP connectivity.

 

Results

Results_6_PtMultiple installations with small and large companies alike have confirmed the benefits of Lightning Shield.  The important results recognized by all customers have included:

  • Improved site reliability and revenues
  • Reduced service interruption expense, repair cost and inventory investment
  • Payback on the Lightning Shield investment within a few months