What defines a wiring system?

[willcambridge]

Hi,
Bit of a vague question, I appreciate any help - my company is writing a proposal on a method of embedding an electrical wiring system within a structural element, for aerospace applications. I am writing the part of the work plan describing how we will characterize the requirements on the wiring system and how they drive hardware design specs: size of wire, insulation, etc. I am wondering about an appropriate way of characterizing a wiring system. Obviously the first thing is, whether it is intended to carry data or power. But beyond that, does one characterize the system by the power rating (peak or steady)...the current...the data transfer rate, or error rate? I know there are standards that may address some of that (RS-232, etc); if I know the standard that is being used, does that define all aspects of the wiring system hardware, some aspects, or none?
I am a mechanical engineer by background, so this is a little out of my knowledge base. Any comments are appreciated.

 

[MikeHalloran]

Power wiring is normally characterized by the current capacity and the insulation voltage rating. Both are affected by ambient temperature. In industrial settings, the temperature and/or ventilation conditions are controlled by standards of construction that will not be guaranteed in your application. Study the National Electrical Code to get an idea of how that works.

You also face potential interesting problems from regular washdowns; see "Kapton" and "F-16".

You will eventually address the problem of how you add/replace conductors in situ, e.g. after lightning strikes and when adding additional equipment.





Mike Halloran
Pembroke Pines, FL, USA

 

[willcambridge]

Thanks for the tip-off on the problems with kapton - I'd never heard of that one before!

 

[Warpspeed]

Sure, power wiring is all about raw current carrying capacity and voltage breakdown.

But control and signal wiring has a whole lot of other requirements that have to do with electrical interference and cross coupling of signals between circuits through mutual capacitive or inductive coupling.

High frequency data and communications wiring is even more critical where bandwidth and impedance become important parameters. Electrical screening to prevent radio frequency interference is likely to be a major issue too.

Generally it is always wise to segregate and isolate these three classes of wiring, otherwise the problems can become overwhelming.

 

[coconutalley]

The NEC gives you code for electrical wiring and EIA-TIA 567(?) gives you code for network wiring.

 

[debodine]

willcambridge:

Since you specify aerospace but no more detail beyond that, I am not sure if the following info will be helpful. But if your company plans on installing these wiring systems on aircraft under the auspices of the FAA (I live and work in America on FAA registered aircraft), you will also want to get familiar FAR xx.581, xx.954, xx.1316 and also with Advisory Circular 20-136. For the FARs above, substitute the FAR part to which your aircraft is subject. For example, my area is part 25, Transport Category Aircraft so I would refer to FAR 25.581, 25.954, and 25.1316. These FARs and the AC provide information about characterization and protection of electrical and electronic systems against the effects of lightning strikes.

debodine