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Conduit
Bridge the joints of the conduits with a ground conductor bonded to the conduit on each
side of the joint. Bond the conduits also to the converter enclosure. Use separate conduits
for grid, generator, DC resistors, and control wiring. A dedicated ground cable is always
required.
Note: Do not run generator wiring from more than one converter in the same conduit.
Armored cable / shielded power cable
6-conductor (3 phases and 3 ground) type MC continuous corrugated aluminum armor cable
with symmetrical grounds is available from the following suppliers (trade names in
parentheses):
•
Anixter Wire & Cable (Philsheath)
•
BICC General Corp (Philsheath)
•
Rockbestos Co. (Gardex)
•
Oaknite (CLX).
Shielded power cables are available from Belden, Lapp Kabel (ÖLFLEX) and Pirelli, among
others.
Selecting the control cables
General rules
￭
All control cables must be shielded.
As a general rule, the control signal cable shield should be grounded directly in the wind
turbine converter. The other end of the shield should be left unconnected or grounded
indirectly via a high frequency, high voltage capacitor of a few nanofarads. The screen can
also be grounded directly at both ends if they are in the same earth line with no significant
voltage drop between the end points.
Use a double shielded twisted pair cable (see figure a) for analog signals. This type of cable
is recommended for the pulse encoder signals as well. Employ one individually shielded
pair for each signal. Do not use common return for different analog signals.
A double shielded cable is the best alternative for low voltage digital signals but single
shielded twisted multipair cable (figure b) is also acceptable.
Run analog and digital signals in separate, shielded cables.
Relay-controlled signals, providing their voltage does not exceed 48 V, can be run in the
same cables as digital input signals. It is recommended to run the relay-controlled signals
as twisted pairs.
Never mix 24 V DC and 115 / 230 V AC signals in the same cable.
a
Planning the electrical installation 55
b
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