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Grounding versus Bonding

PART III. GROUNDING ELECTRODE SYSTEM AND GROUNDING ELECTRODE CONDUCTOR

Sections

250.60 Lightning Protection System Grounding (Earthing) Electrode.

The grounding electrode for a lightning protection system cannot be used for the building or structure grounding electrode system as required by 250.50. Figure 250–110

Author’s Comments:
• Where a lightning protection system is installed, it must be bonded to the building or structure grounding electrode (earthing) system [250.106].
• A lightning protection system installed in accordance with NFPA 780, Standard for the Installation of Lightning Protection Systems, is intended to protect the building structure from lightning damage. It isn’t intended to protect the electrical wiring or equipment within the structure from lightning damage. To protect from high-voltage transients, proper transient voltage surge-protection devices must be installed in accordance with Articles 280 and 285.

• GROUNDING ELECTRODE CONDUCTOR. Grounding metal parts of the electrical installation to earth is intended to reduce voltage on the metal parts from lightning so as to prevent fires from surface arcing (side-flashes) within the building or structure [250.4(A)(2)]. In addition, high-voltage distribution systems (typically electric utility wiring) are grounded to the earth to help limit high voltage on system windings from lightning, unintentional contact with higher-voltage lines, or line surges [250.4(A)(1)].


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