olbigtenor:
...
> For the LED light controls there is a three wire cable that comes off
> the fixture.
> I have been using 18-3 wire (sorry don't know what that is in the DIN
> system) (called signal wire in the electrical trade) and that matches
> the wiring on the fixture.
...

Guess that is similar to tree wires of 0.75mm2 in a cable.

///

The inportant things to consider:

Power lines:
voltage drop due current flow, you want sufficient voltage
at the end of the cable.

Signal lines:
let tr = the fastest rise time from 10% to 90% of the signals top voltage

(then fn = the knee frequency = 0.5/tr
the knee frequency is a crude estimate of the highest frequency
content in your signal)

v = signal velocity in the cable is about 0.6 * c
where c = speed of light in vacuum

l = lenght of the rising edge in the cable = Tr * v

if cable length < l/6
then the cable can be treated as a lumped circuit
else it has to be treated as a transmission line

if transmission line the cable has to be treated with care,
no sharp bends, no bad connections, no deformed parts

///

Always use a suitable terminator matching the cable impedance.
Beware of
incident elecromagnetic interference, electromagnetic emmisions,
UV-light, heigh/low temperature, vibrations, mechanical forces.
excessive moisture, fungus, rats chewing on cables,
earth voltage differences ...

///

UTP is useful up to 250Mbps per pair
150Ohm STP-A upto 1Gpbs
Coax beyond 1Gbps

For long streaches, there is coax cables with low attenuation.

///

For you I guess outdoor utp cable will suit you well.
They are usually black and heavier than indoor cable, use
stranded version where there are vibrations.

Where there is vibration, use rubber cable with fine stranded
conductors, so use outdoor installation cable upto near you
fans ending in a connection box, and from there a flexible
rubber cable the last meter (for the power), and just as well
a safety switch instead of the connection box.

Regards,
/Karl Hammar