CHAPTER IX 



ELECTRICAL EQUIPMENT 



1. GENERAL CONSIDERATIONS 



BEFORE entering into a detailed study of the apparatus com- 

 prising the electrical equipment, there are two broad problems 

 which require a more careful consideration and must first be 

 decided on, inasmuch as they have an important bearing on the 

 entire equipment. These problems deal with the voltage and the 

 frequency. 



Voltage. There are three voltages between which a distinc- 

 tion must be made in a hydro-electric power system; viz., the 

 generator voltage, the transmission voltage and the distribution 

 voltage. 



Generator Voltage. When additions to an existing plant or 

 system are made, the voltage of the new generators is generally 

 determined by that of the old machines, or by some other con- 

 dition of the installation. In new installations, however, the gen- 

 erator voltage can be determined only after considering a number 

 of factors. For example, a compromise must, as a rule, be found 

 between the increased cost of a high-voltage machine and its 

 control equipment as compared with the reduced cost of the bus- 

 bars and connections caused by the smaller amount of copper 

 required. Whether generators are to be wound for a high voltage 

 for direct transmission, or for low voltage and step-up transformers, 

 is to a certain extent also decided by the relative cost of the two 

 methods. If economically feasible the latter method with step-up 

 transformers is, however, the most reliable and to be recommended. 

 In other instances the nature of a local load may be such that, 

 by installing high-voltage generators, power for this load may be 

 directly transmitted at the generator voltage; while at the same 

 time step-up transformers may be provided for raising the pres- 

 sure of the current which is to be transmitted for greater dis- 

 tances. The standard generator voltages are given under " Syn- 

 chronous Generators." 



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