[GTALUG] mysterious restarts

[James Knott]

On 06/15/2016 11:45 PM, Alvin Starr via talk wrote:
>> I'm no EE, but here's my guess.
>>
>> Energy losses are proportional to the square of the current and thus
>> the square of the inverse of the voltage.
>> 	(750/600)^2 = 1.5625
>> So they would save more than a third of the transmission losses.
>>
>> I have no idea how much their transmission losses are as a proportion
>> of the electrical power used.
> It has been way too long since I have done any power calculations and
> I believe your right.
> Looks like its time to brush up on my math skills.

Power is indeed I^2*R, so losses increase with the square of current. 
However, what's that in relation to the load?  One other point that Andy
Byford mentioned, when there was that power failure due to fire a while
ago, is that most segments are fed from both ends, so you have in effect
parallel feeds, with the resistance of each varying with the location of
the streetcar along the track.  So, the streetcar moves from a point
directly below a point where the power is connected to the line, then
moves to a point equidistant from 2 points and then to directly below
another point.  This adds "fun" to the calculations.  ;-)
Of course, you often have more than one streetcar on a segment.