Specifications

Appendix-d Lightning Protection Recommendation
November 11, 2013
d‐2
Copyright©2013,HarrisBroadcast
WARNING:Disconnectprimarypowerpriortoservicing. 888‐2628‐300
Figure d-2 Lightning Incidents to Tall Structures
d.2 Environmental Hazards
Therearedevicesandproceduresthatdoofferprotectionfromlessorenvironmentalhazardsthanlightning.Some
oftheseanomaliesarelistedanddefined:
1. Overvoltage/undervoltage(brownout).Wherethelinesvoltagediffersfromthenominal
RMSforlongerthanonecycle.

Remedy‐Automaticvoltageregulators,preferablyindividualregulatorsoneachphase.This
canonlybeaccomplishedwhenthepowerfeedlineisdeltaor4/wirewyeconnected,See
Figured‐3.
2. Singlephasing.Thisiswhereonelegofthethreephaseserviceisopen.
Remedy‐Protectionaffordedbyalossofphasedetector.Withoutprotectionpowertrans‐
formersand3phasemotorsoverheat.
3. Radiofrequencyinterference(RFI).Thisissomethingwemustdesignintoalltransmitters,
however,equipmentmaybepurchasedthatissusceptible,isnotprotected,andmaydevel
‐
opproblems.
Remedy‐RFIfiltersontheaclinesandcontrollinesaresometimeseffective.Sometimesthe
entiredevicemustbeenclosedinanRFfreespace.
4. Electromagneticpulse(EMP).Thisisainterferingsignalpulsethatentersthesystembymag‐
neticcoupling(transformer).Generallycausedbylightning.
Lightningfromcloudtocloudproduceshorizontallypolarizedwaveswhilelightningfrom
cloudtoearthproduceverticallypolarizedwaves.Thewavescoupleintothepowerlinesand
transmissionlinescausinglargeinducedvoltagethatdestroyhighvoltagerectifierstacksand
outputcircuitfaults.Highfrequencyenergyiscoupledbackintothe
transmittercausing
VSWRoverloads,See
Figuresd‐4andd‐5.
Remedy‐Ballorhorngapsatthebaseoftheantennapreventthevoltagefromexceeding
somehighpotential.Transientsuppressordevicesontheinputpowerlinesremoveexcessive
voltagespikes.Buriedpowerandtransmissionlineswillreducetheamountofcoupledener
‐
Number Per Year
Structure Height In Feet
All
Triggered Events
500
1000
1500
2000
Collected
Events
40
30
20
10