PETERSEN SYSTEM OF GROUNDING 59 



with neutral grounded through zero or a low impedance would he 

 largely reduced by grounding through the Petersen reactor instead. 

 Residuals of other harmonic frequencies should be substantially the 

 same as with isolated neutral, and are controllable by means of power 

 circuit transpositions. The method of grounding the neutral through 

 a resistance of moderate value is favorable to the reduction of residual 

 voltages of the harmonics whose orders are not multiples of three, 

 but is relatively unfavorable to the suppression of residual currents 

 of these frequencies. It is also considerably less effective than the 

 reactor in preventing residuals, either voltages or currents, belong- 

 ing to the triple harmonic series, which are not amenable to treat- 

 ment by transpositions. 



