Running Cat5e cable underground

[David Hansen]

On 24 May 2006 01:12:55 -0700 someone who may be "Phil" wrote this:-

And what events are those?

[Osprey]

You missed the point ... the exchange running copper to you is one thing, it's earthed at a single point. If you run copper comms from your house to an out building there is a proscribed risk due to linking of earth paths in the event of the mains losing it's earth ... or in event of lightning strike.

[w_tom]

Well proven even before WWII: even buried wires suffer from direct lightning strikes like overhead cables. Even before WWII, both underground and overhead wires were properly earthed when entering a building - and therefore damage from lightning was routinely averted. Technology is that old and that well proven. An October 1960 paper in Bell System Technical Journal from Bodle and Gresh desribes standard protection. Their question was whether buried and overhead wire protection - generations standard even before 1960 - was sufficient for semiconductors:

Those who never learned basic protection techniqes then recommend expensive solutions such as fiber optics.

Any c> Osprey wrote:

[David Hansen]

On 30 May 2006 02:20:54 -0700 someone who may be "w_tom" wrote this:-

Those who never learned basic wiring practices then recommend potentially dangerous "solutions" such as earthing communications cables. This exposes the communications cable and those in contact with it to all sorts of dangers.

There is a difference between functional earths and protective conductors, which is why the cables concerned are identified by different colours. I mention this in case anyone is foolish enough to believe what you typed and act on it. They should instead understand the difference, contact the owner of the cable and follow BS 7671.

[w_tom]

Everything as posted conforms to both BS7671 and BS6651. If David really had a problem with what was posted, then he would have defined specific problems. He did not. He just posted BS numbers with no reference to what creates dangers.

Accurately noted and specifically defined by BS6651:

Earth> On 30 May 2006 02:20:54 -0700 someone who may be "w_tom"

[unopened]

The problem is that your average d-i-yer, who can put up a set of shelves, is actively discouraged by Part P from gaining any understanding of electrical installations, and as a result, is unlikely even to be aware of the need for earthing of data communications cables, let alone how to do it properly. At least using fiber-optic cables is fail safe (electrically), and not especially expensive. Think of the extra cost as being an insurance premium against ignorance. Personally, I too would favour the use of fibre-optic - always remembering not to look into the laser with the remaining eye.

Sid

[David Hansen]

On 31 May 2006 02:04:03 -0700 someone who may be "w_tom" top posted this:-

Nice jargon, but meaningless without further explanation.

In situations such as PME protection from failures outside the building is particularly important. Avoiding excessive currents on telecommunications cables under PME fault conditions is one of the reasons why one needs to use one's brain.

As I said, there is a difference between functional earths and protective conductors, which is why the cables concerned are identified by different colours.

[w_tom]

Electronics protection is earth ground. Protectors are devices that temporarily connect each wire (inside a cable) to earth. Protectors are, well, an industry professional says it clearly:

Section 6.4

No earth ground means no effective protection. 'Path of least impedance' means an earthing connection should be a less than 3 meter connection. All incoming wires must connect to a 'single point' ground. No earthing means ineffective protection. Every incoming wire even in that 1960 Bell System Technical Journal (a concept that well understood even long before 1960) makes an earthing connection where wire enters a building. Earth ground - not a protector - is protection. Earthing is essential to transient protection (as demonstrated by British Standard 6651) as well as to protect occupants in one building from electrical failures in another building. Defined are transistor safety and human safety functions of earthing.