[LINK] Proposed power supply standard

[jim birch]

On 22/02/07, Howard Lowndes <lannet at lannet.com.au> wrote:
>
> The lower the distribution voltage, the more power gets lost to heat.
> Why do you think the national grid runs at such high voltages, it's
> because it can minimise the heat loss in transmission.  I won't bother
> you with the details of the formulae.


Yes, Power loss is related to current (**2) so high voltages are more
efficient.  National grids carry very high power loads over very long
distances. But:

Most power packs deliver milliwatts to things like phones and trickle
chargers.  Telstra uses a low voltage system to power (ye olde) house
phones.    Short low power runs around a house wouldn't be carrying high
currents and with a designed system the resistive losses could be less than
saving of eliminating on individual inefficient always-on transformers.  I
suspect the reason it isn't done is the lack of a standard, not the power
dissipation.  But I haven't seen a calculation.


As a side note, I have a pilot friend who specialises in close proximity
> flying, either very low level geosurvey, or power line survey.  In power
> line survey they can use two cameras - one visual to identify the tower
> and the other infra-red, sensitive to parts of a degree, to look for hot
> insulators and stand-offs.


Reminds me of a balloonist friend who hit a local distribution line.  It
melted one - luckily, only one - of the cables that hold the basket to the
envelope.   At that moment, hanging on three wires and wondering what was
coming next, he would have well preferred a low voltage distribution system.
:-)

(FYI He scraped over the wires, semi intact.)

Jim