GROUND PLATE INSTEAD GROUND ROD

[pristava]

Communication Antenna is provided to be grounded with three
ground rods ( 3.0 m long) connected by 2/0 wires. Also connection with existing grounding is provided to be made.
Contractor is preparing to intall three ground plates instead ground rods.
Question:
How to calculate grounding in that case ? Is it possible to replace ground rod by ground plate making the same grounding resistance.
Thanks!

 

[davidbeach]

I don't have access to it here to check, but the IEEE Green Book has ground impedance calculations for many different configurations of ground equipment.

 

[advidana]

Specify the resistance you need to the contractor then let him do the math.

 

[alehman]

Resistance to earth can be calculated roughly if soil resistivity is known. Sometimes it is necessary to use trial and error approach (e.g. start with 2 or 3 and add more as needed to get desired result).

 

[jbartos]

Suggestion: The lightning protection should be grounded according to up to date 2000 edition of:
NFPA-780 Standard for the Installation of Lightning Protection Systems (1997)

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

The antenna system grounding is specified under the transmitter/receiver spec.
See NFPA 70-2002 National Electrical Code for Article 810 Radio and Television Equipment. (There is no specific Ohms value stated for the antenna grounding.)