Condition of downconductor when lightning

[keith2015]

Actually the earth should be zero voltage. By when the downconductor subject to the lightning, it will cause the ground potential rise. What is the estimate value of this ground potential rise?

 

[Bung]

Simplistically, lightning current times resistance of connection to earth - eg 10kA stroke to a 1-ohm ground is 10kV. More sophisticated analysis should take into acount shape and duration of impulse and transient impedance of earth stake... seems to be black art more than a science to me!

Bung

 

[jbartos]

Suggestion: Reference:
1. D.G. Fink and H.W. Beaty "Standard Handbook for Electrical Engineers," 14th Ed., McGraw-Hill, 2000
Section 27 Lightning and Overvoltage Protection
Figure 27.8 Illustration of electric field below an electrified thundercloud.
Essentially, the electrical field of the Earth rises below the electrified thundercloud.

 

[busbar]

Possibly useful references in NFPA 780 boilerplate, Lightning Protection Code.

http://www.nfpa.org/Codes/NFPA_Codes_and_Standards/List_of_NFPA_documents/NFPA_780.asp

OTOH, Skimming Google exposes seemingly utter contempt for 780:

http://www.lightningsafety.com/nlsi_lhm/NFP_780.html

and,

http://tis.eh.doe.gov/techstds/meeting/NRCDOELightningStandardsPresentation.pdf

 

[SooryaShrestha]

I think for lightning the ground resistance affects less compared to the grounding system reactance. Thushe difficult value to be obtained that is 1 ohm resistance value will have less impact. The reactance value will be in the range surge impedance value, which can be lowered by making branching of the grounding system in tree like fashion. The potential rise will be simple as indicated by Bung.