RadioBanter - View Single Post

July 21st 05, 04:24 AM

On Wed, 20 Jul 2005 21:13:42 -0500, (Richard
Harrison) wrote:

Richard Clark wrote:
"The very first formula from the Standard Handbook for Electrical
Engineers, Section 11. Power Transmission, Electrical Calculsations:
I = P/E (1) "

Unless a d-c transmission is specified, that`s wrong.

Hi Richard,

You may disagree with the contents from this tome, but the citation is
accurate.

P=EI cos theta, where theta is the angle between E & I. For 0-deg. coa
theta=1.

The section preceding distribution is Section 10, Power Plants, which
devotes Para. 722 Inherent regulation; Para. 724 The Load Factor;
Para. 725 Load Fluctuation; Para. 726 The Power-Factor.
Sections10-795 through 836 is given over to AC switching.

And of course casting back towards the beginning of the Handbook we
find ourselves at Section 7, Alternating Current Generators which
covers Power-Factor, Slip, Stalling torque.... The treatment later in
the section covers representative efficiencies in Polyphase equipment
up to 1000HP well into the 90's of percent. All may note that this is
an accuracy that is still 10 times better than the "Can you solve
this" math offered here.

Returning to Section 11, Power Transmission; coverage there includes
Power-Factor Correction. Para. 95, in part:
The per cent, quadrature current required for unity power-factor
[which renders the formula responded to as accurate] at the
receiver may be determined from Fig. 14, or may be calculated
for a three-phase system as follows.... [which I won't go into
but covers power-factors from 60% to 95%].

There is still no requirement to fill the need for a vector of
direction.

This relates, in part, to my service in the Power Industry designing
power grid control systems and testers (SCADA).

73's
Richard Clark, KB7QHC