Page 213 - Fluid Power Engineering

W i nd T urbine Generator (WTG) Components 185

flange at the bottom of the tower. Threaded steel rods encased
in PVC sleeves are then bolted to the embedment ring and the
template.
The bolt cage is lifted to attach a rebar hoop, one around the

outside bolts and another around the inside bolts. The bolt
cage is then lowered into the CMP while ensuring that the
cage is leveled and the cage is concentric with the outer CMP.
An inner CMP is placed concentric to the outer CMP. A plug

of concrete is cast at the bottom of the inner CMP. Electrical
conduits are installed. The inner CMP is then backfilled with
soil.
In the concentric area between the outer and inner CMP, foun-

dation concrete is poured.
Concrete floor slab and top collar are cast with the threaded

rods extending above the concrete.
After curing of concrete, the grout trough is grouted. Then,

the tower base is placed on grout and leveled.
The anchor bolts are then post-tensioned to keep the concrete

in compression for all conditions of loading.
Design Loads of Wind Turbines
7
IEC 61400-1, Wind Turbines-Part 1: Design requirements, provides
the minimal design requirements for wind turbines. In this section,
readers are exposed to some parts of the design requirements; how-
7
ever,readersarereferredtotheIEC61400-1 fordetails.TheIECdesign
requirements are specified using a case-based methodology. Overall,
12 cases are identified by IEC; each case is a combination of the fol-
lowing four conditions: 7

1. Design situations that represent the combinations of modes of op-
eration of a turbine. There are eight design situations speci-
fied: Power production; power production plus occurrence
of fault; start up; normal shutdown; emergency shutdown;
parked (standing still or idling); park and fault conditions;
transport, assembly, maintenance, and repair. This is the min-
imal set, additional modes of operation may be added that
have a reasonable probability of occurrence and significant
impact.
2. Wind conditions for analyzing the design situations. Several types
of wind conditions are used for the purposes of design: Nor-
mal wind profile model (NWP), normal turbulence model
(NTM), extreme wind speed model (EWM), extreme turbu-
lence model (ETM), extreme wind direction change (EDC),