4 CONSTANT-VOLTAGE TRANSMISSION 



examples in later chapters. Although it is possible for 

 sychrononous machines to drop out of step, this danger 

 is much less with the latest types of machines, especially 

 if they have no mechanical load, and very large propor- 

 tions of synchronous machines are now successfully being 

 used in the receiving stations of large transmission lines. 

 Taking into account both of the above considerations, it 

 may be stated that the constant- voltage method does not 

 reduce the reliability of operation. 



Perhaps the most important recent development in 

 power transmission is the growth of extensive high ten- 

 sion net-works, which, having already stretched between 

 cities nearly 800 miles apart, would seem to have no limit 

 whatever to their growth. The economies and advan- 

 tages of the constant-voltage method will assist the 

 growth of such net-works. 



Constant- voltage transmission is not merely a theory. 

 It has already been utilized successfully in several power 

 systems, both of large and small size. A brief outline of 

 some of these, as taken from descriptions in the technical 

 magazines, is given in Chapter VII. 



It may be stated that without doubt not nearly 

 enough synchronous machines are made use of at present 

 for the best economy and the best operation. As there 

 are attractive possibilities in constant-voltage transmis- 

 sion, both for long-distance projects and for city systems, 

 and as there are also cases where the constant- voltage 

 method is scarcely applicable, it is worth while obtaining 

 a clear understanding of the principles of this method, 

 since they differ quite widely, both in theory and prac- 

 tice, from the more usual methods. 



