INSTALLATION OF MONITORING STATIONS - Wind Resource Assessment: A Practical Guide to Developing a Wind Project - page 78

copper wire referred to as the down conductor tied to the earth ground (a grounding rod
or buried loop). The lightning rod generally is considered in most countries to be part
of the tower's height, and therefore, the top of the rod cannot exceed height restrictions.

Additional Transient Protection Measures. To provide extra protection
against electrical transients, a number of additional steps can be taken:

• The sensor wires can be connected to an additional bank of spark gaps (or surge
arrestors) before they are connected to the data logger input terminals.
• A longer air terminal rod with multipoint brush head may provide protection for
side-mounted sensors near the tower top by placing them within the theoretical
45 ◦ “cone of protection.” The purpose of the air terminal is to provide a low
impedance path for streaming away charged particles; the cone of protection is
the region below the air terminal where lightning flashes are less likely to occur.
• Longer grounding rods may be used. They provide two benefits: first, the soil's
conducting properties generally improve with increasing depth, and second, addi-
tional contact surface area is gained. Rods that fit together to reach greater soil
depths are available for purchase.
• High compression, welded or copper-clad fittings can be employed for all
conductor-rod connections.
• The current-carrying capacity of the down conductor can be increased by increas-
ing the cross-sectional area of the wire (i.e., by reducing the wire's gauge).
• The down conductor can be secured to the tower's metal surface with band
clamps (one per tower section). Deoxidizing gel helps ensure a good connection.
• A buried copper ground plate or ground ring can be employed at recommended
depths to increase soil contact area. It should be connected with other grounding
rods.
• Horizontally mounted air terminals can be installed at various levels and direc-
tions on the tower to provide additional points for charge dissipation. Each rod
should be tied to the down conductor to avoid affecting sensor readings.

If the tower is secured with concrete or coated (corrosion-resistant) guy anchors,
which do not provide a low resistance path to ground, it is recommended that
the guy cables be grounded.

•

5.8 SITE COMMISSIONING

All equipment should be tested to be sure it is operating before a tilt-up tower is
raised or while tower climbing personnel are still aloft. These functional tests should
be repeated once the installation is complete. Having spare equipment on hand makes
repairs easier if problems are found during these tests. Recommended tests include
the following:

• Ensure that all sensors are reporting reasonable values.