Furuno 9ZWWR2120, Руководство по установке

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S2E-17-0209_IM_WR2120_C
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2.2.2. Assessment of annual number of dangerous events
According to the statistic information provided by the National Environment Agency of Singapore,
average thunderstorm days per year ( ) at Changi is 168. The lightning ground flash density
will be leaded as follows:
2.2.2.1. Number of dangerous events for the structure
may be evaluated as the product:
where
is the lightning ground flash density
is the collection area of the structure
is the location factor of the structure, 0.5 for CWRP
1) Determination of the collection area
For isolated structures on flat ground, the collection area is the area defined by the
intersection between the ground surface and a straight line with 1/3 slope which passes from
the upper parts of the structure (touching it there) and rotating around it. Determination of the
value of will be performed graphically or mathematically.
For an isolated rectangular structure with length L, width W, and height H on flat ground, the
collection area is then equal to:
where L, W and H are expressed in meters.
Figure A-2: Collection area of an isolated structure (IEC 62305-2)
2) Relative location of the structure
The relative location of the structure, compensating for surrounding structures or an exposed
location, will be taken into account by a location factor . For the weather radar at CWRP,
(Structure surrounded by objects of the same height or smaller).
2.2.2.2. Assessment of the average annual number of dangerous events due to flashes near a
structure
may be evaluated as the product:
where
is the lightning ground flash density
is the collection area of flashes striking near the structure
1:3
H
V
3H
L
IEC 2637/10