# Looks like we should wire with "pipe" !

• 06-17-2012, 03:59 PM
ballvalve
Looks like we should wire with "pipe" !
The skin effect is quite interesting, And perhaps it means we get better voltage transfer with stranded wire.

Quote:

Skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor, and decreases with greater depths in the conductor. The electric current flows mainly at the "skin" of the conductor, between the outer surface and a level called the skin depth. The skin effect causes the effective resistance of the conductor to increase at higher frequencies where the skin depth is smaller, thus reducing the effective cross-section of the conductor. The skin effect is due to opposing eddy currents induced by the changing magnetic field resulting from the alternating current. At 60 Hz in copper, the skin depth is about 8.5 mm. At high frequencies the skin depth becomes much smaller. Increased AC resistance due to the skin effect can be mitigated by using specially woven litz wire. Because the interior of a large conductor carries so little of the current, tubular conductors such as pipe can be used to save weight and cost.

http://en.wikipedia.org/wiki/Skin_effect ........ Quite an interesting article about electricity.
• 06-18-2012, 07:34 AM
BobL43
Quote:

Originally Posted by ballvalve
The skin effect is quite interesting, And perhaps it means we get better voltage transfer with stranded wire.

http://en.wikipedia.org/wiki/Skin_effect ........ Quite an interesting article about electricity.

I don't deal much with high voltages, at least anything above 460VAC, but I always was under the impression that the skin effect is mostly at very high Kilovolts on power transmission lines. Silly me. And at my age, all those formulas just give me a headache.
• 06-18-2012, 07:46 AM
hj
That is why high voltage conductors ARE basically 'pipe'. You would not like to try to wire a house with copper tubing, and the benefit would be so minimal, that you might not even be able to measure it.
• 06-18-2012, 08:16 AM
jwelectric
The use of metal pipes and “skin effects” can cause the metal raceway to become energized.

The biggest problem with skin effects comes from frequencies not the amount of voltages. The higher the frequency the farther out the conductor the current flows. This is the reason we are required to bond both ends of a metal raceway that contains the grounding electrode conductor. Although lightning is a DC event it comes at very high frequencies.
• 06-18-2012, 09:40 AM
BobL43
Quote:

Originally Posted by jwelectric
The use of metal pipes and “skin effects” can cause the metal raceway to become energized.

The biggest problem with skin effects comes from frequencies not the amount of voltages. The higher the frequency the farther out the conductor the current flows. This is the reason we are required to bond both ends of a metal raceway that contains the grounding electrode conductor. Although lightning is a DC event it comes at very high frequencies.

Ahem; is that last sentence what we would call an oxymoron? Like a Little Giant?;) does that happen frequently? You mean it is ziggy DC?
• 06-18-2012, 10:18 AM
jwelectric
Quote:

Originally Posted by BobL43
Ahem; is that last sentence what we would call an oxymoron? Like a Little Giant?;) does that happen frequently? You mean it is ziggy DC?

The easy way to think about it is the level of voltage from beginning to end of the event varies from low to very high repeatedly and at a very high rate of speed between peak to peak thus a high frequency.
• 06-18-2012, 04:47 PM