INSTALLATION OF MONITORING STATIONS - Wind Resource Assessment: A Practical Guide to Developing a Wind Project - page 75

5.7.5 Sensor Connections and Cabling
The manufacturer's instructions for sensor and data logger wiring configurations
should be followed. General guidelines include the following.
• Exposed sensor terminal connections should be sealed with silicone caulking and
protected from direct exposure with rubber or plastic boots.
• Sensor wires along the length of the tower should be wrapped and secured
with UV- and exposure-resistant wire ties or electrical tape. All slack should
be removed as the sensor wires are wrapped around the tower or tower leg.
Excessive slack can allow the sensor wires to move in the wind, eventually
causing them to break.
• If not installed by the manufacturer, consider installing metal oxide varistors
(MOVs) across each anemometer's and wind vane's terminals for added electrical
transient protection.
• Where chafing can occur between the sensor wires and supports (such as tilt-up
tower anchor collars), the wires should be protected and secured appropriately.
5.7.6 Grounding and Lightning Protection
Grounding equipment is especially important for modern electronic data loggers and
sensors, which can easily be damaged by electrical surges caused by electrostatic
discharge, lightning, or a difference in ground potential. 2 Most tower and data logger
manufacturers provide grounding kits. However, different monitoring areas may have
different requirements. Sites prone to lightning activity require an especially high level
of protection. Additional protective equipment can often be purchased from the data
logger manufacturer or made from common materials found at a hardware store. As
part of the planning process, the frequency of lightning activity at the site should be
investigated. References such as the lightening frequency map shown in Figure 5-8,
as well as meteorological agencies, can provide useful guidance. Even with complete
protection, it cannot be guaranteed that equipment will survive a direct lightning strike.
Basic Guidelines. The single-point grounding system, presented in Figure 5-9,
is the recommended configuration. This setup minimizes the potential for developing
an offset voltage by a grounding loop. In this system, the down conductor wire (10
gauge or less) is directly connected to earth ground via a grounding rod, buried ring,
or plate (or a combination of these). It should not be routed through the data logger's
grounding stud. The sensor drain or shield wires are electrically tied to the same earth
ground via the data logger's common grounding bus (terminal strip). Earth ground is
2 For further information regarding grounding, refer to the appropriate electric code for the country or region
in question (e.g., in the United States, National Electrical Code: Article 250-Grounding and Bonding; in
Europe, IEC 60 364; in Canada, Canadian Electrical Code; in the United Kingdom, BS 7671; and in France,
NF C 15-100).