Chapter 3 ________________________________________________________________ Installation
VAISALA ________________________________________________________________________ 23
Equipment Grounding and Lightning Protection
The power supply cable with its protective earth conductor (PE) provides
a standard protective ground for the AC (mains) power supply inside the
interface unit. A 3-conductor AC cable with a proper earth conductor
grounding must be used.
Equipment grounding protects the electrical modules of FS11 against, for
example, lightning and prevents radio frequency interference. Equipment
grounding for the FS11 sensor is done with a jacketed grounding cable
and conductive grounding rod(s).
The enclosure of the FSI102 interface unit should be grounded using the
grounding clamp located under the cable flange (see Figure 3 on page
24). A 16 mm
2
jacketed grounding cable should be connected to the
clamp.
In case of a frangible mast, the FSM102 Measurement Unit is also
grounded with a 16 mm
2
jacketed grounding cable that is located inside
the mast.
Depending on the need, one to four copper-sheathed steel rods are driven
into the ground. In case several rods are needed, the alignment from the
foot of the base plate must be radial.
The grounding principles are the following:
- Install the grounding rod as close to the pole mast as possible, to
minimize the length of the grounding cable. The grounding cable can
also be cast inside the concrete base.
- The length of the grounding rod depends on the local groundwater
level. The lower end of the grounding rod should continuously touch
moist soil.
The quality of the grounding can be checked with a georesistance meter.
The resistance should be less than 10
Ω
.
NOTE
Make the grounding cable long enough to allow the mast to tilt properly.
