Fig. 2,193.—Line of the Schenectady Power Company crossing the tracks of the Boston and Maine Railroad near Schaghticoke.
| Length of line in miles | Voltage |
|---|---|
| 1 | 500 to 1,000 |
| 1 to 2 | 1,000 to 2,300 |
| 2 to 3 | 2,300 to 6,600 |
| 3 to 10 | 6,600 to 13,200 |
| 10 to 15 | 13,200 to 22,000 |
| 15 to 20 | 22,000 to 44,000 |
| 20 to 40 | 44,000 to 66,000 |
| 40 to 60 | 66,000 to 88,000 |
| 60 to 100 | 88,000 to 110,000 |
Ques. What are the standard voltages for alternating current transmission circuits?
Ans. 6,600, 11,000, 22,000, 33,000, 44,000, 66,000, 88,000.
The amount of power to be transmitted determines, in a measure, the limit of line voltage. If the most economical voltage considered from the point of view of the line alone, be somewhere in excess of 13,200, step up transformers must be employed, since the highest voltage for which standard alternators are manufactured is 13,200. In a given case, the saving in conductor by using the higher voltage may be more than offset by the increased cost of transformers, and the question must be determined for each case.
Fig. 2,194.—View of a three phase, 2,300 volt, 60 cycle line at Chazy, N. Y. The current is transmitted at the alternator voltage 2¾ miles over the single circuit pole line. The poles are of cedar with fir cross arms, and are fitted with pin insulators. They are from 35 to 40 feet high and are spaced at an average of about 120 feet. The conductors are bare copper wire No. 00 B. & S. The alternators consist of one 50 kw., and one 100 kw. General Electric machines.
Ques. What are the standard transformer ratios?
Ans. Multiples of 5 or 10.