standards and guidelines for communication sites - Radio And ...

STANDARDS AND GUIDELINES FOR COMMUNICATION SITES LIGHTNING ACTIVITY AND EXPOSURE
• To stabilize the AC voltage relative to the earth under normal conditions.
• To contribute to reliable equipment operation.
• To provide a common signal reference ground.
4.2 LIGHTNING ACTIVITY AND EXPOSURE
Communications facilities shall be defined as exposed to lightning unless thunderstorm activity in the
area is an average of five thunderstorm-days per year or fewer and soil resistivity at the site is less than
10,000 ohm-centimeters (Ω-cm). The soil resistivity shall be measured as described in ANSI/IEEE STD
81. (ANSI T1.313-2003, section 5.1.1) See Appendix B for soil resistivity measurement methods.
Figure 4-1 and Figure 4-2 are maps representing typical lightning activity throughout the world. These
figures are for general informational and educational purposes only and are not indicative of current or
future lightning activity. The average amount of lightning that occurs in any given area varies
significantly from year to year.
NORTH
AMERICA
0 – 1
2 – 4
5 – 9
10 – 19
20 – 39
40 – 59
60 – 79
80 – 99
100 – 139
140 – 200+
SOUTH
AMERICA
EUROPE
AFRICA
FIGURE 4-1 LIGHTNING ACTIVITY, THUNDERSTORM DAYS PER YEAR
68P81089E50-B 9/1/05 4-3
ASIA
AUSTRALIA