CHAPTER XI 



FUTILITY OF USING UNUSUALLY LARGE VOLTAGE VARIATION 



THE constant- voltage method enables a transmission 

 line to deliver a load which would produce a voltage regu- 

 lation of 40 or 50 per cent, were it not for the continual 

 adjustments in power-factor made in order to hold the 

 voltage constant. Ordinarily, a load which gives a 

 voltage variation of 20 or 25 per cent is all that can be 

 taken care of either by hand regulation or by automatic 

 regulators, since both the momentary variations and 

 the total variations become troublesome. Some water- 

 power plants, however, deliver all their power over a 

 transmission line to a city, no power being sold close to 

 the power plant, and so the total voltage variation at 

 the generators is of small moment. 



The question, therefore, may well arise, "If an 

 automatic regulator could be developed which would be 

 able to produce satisfactorily steady voltage at the city 

 even when the total variation at the generators is 50 

 per cent, would it give the advantages of the constant- 

 voltage system without the expense of synchronous 

 motors ? " The answer is that when a varying-voltage 

 line delivers so much power as to give 40 or 50 per cent 

 regulation, the large lagging current sent over the line 

 from the generators reduces the generator power-factor 

 and the transmission-line efficiency to a remarkable de- 

 gree, so much so that synchronous motors are worth 

 their price merely for reducing the Kva. load and the 

 Kw. load on the generating station, without considering 



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