Allied Telesis IE048-480, Руководство по установке

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Chapter 2: Beginning the Installation
38
Lightning
Protection
Requirements
Lightning strikes the ground and follows the paths of least impedance to
cause damage. To provide an effective lighting protection system, you
must put the following fundamental measures in place:

Install surge protectors. Every service entrance should have surge
protection to stop the intrusion of lightning from outside.

Implement bonding. Eliminate the opportunity for lightning to side-
flash internally. The bonding resistance between any termination
point and the related earthing rod should not exceed 0.01 ohms.

Install grounding electrode system. The system should efficiently
move the lightning to its final destination away from the structure
and its contents.The resistance of the common grounding
electrode must not exceed 5 ohms.

Install cable conductors. Cable conductors route lightning current
over and through the construction, without damage, toward the
grounding electrode system.

Use appropriate grounding. Systems without appropriate
grounding can experience either complete system failures or
intermittent problems that are hard to diagnose. Improper
installation of electrical grounding components can make the
components work ineffectively. Installing a system with the proper
grounding equipment and following proper installation guidelines
can reduce potential down time as well as costly repairs to system
electronics.
Note
The users of the plant or those responsible for the installation should
apply the necessary measures (e.g., shielding, bonding, and
grounding protection) to ensure that the interference voltages
caused by lighting strikes do not exceed the available immunity
level.
Table 7. Ground Resistivity Recommendations
Level Recommendation
Best Practice <5 ohms
Acceptable 5 to 15 ohms
Marginal 15 to 25 ohms
Non-compliant >25 ohms