OVER-VOLTAGE PROTECTION 



601 



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the wave in passing the transition point continues its travel in the 

 form of a wave; that is, in case we have distributed inductance 

 and capacity on both sides of the transition point. If, on the 

 other hand, resistance, inductance and capacity are concentrated 

 at the transition point, the conditions become entirely different, 

 and it has been suggested that such a scheme should be used for 

 protecting transformers and machinery against the traveling 

 waves entering from the line. The use of inductance and capacity 

 has been advocated for some time, and both have the properties 

 of changing the wave front of the transmitted wave so that it 

 begins with zero and rises gradually to its full value. The reflected 

 wave, however, will have a rectangular or steep wave front, sim- 

 ilar to the incoming wave. 



The energy of the incoming wave is naturally also split up in 

 two parts, corresponding to the transmitted and reflected waves, 

 but there is no reduction in the R 



total energy. This has led to the 

 suggestion by Gino Campos to 

 use a resistance shunted across 

 an inductance (see Fig. 384). In 

 addition to considerably smooth- 

 ing out the wave front of the 

 transmitted wave, it causes some 

 of the electro-magnetic energy to 

 be dissipated. The inductance 

 forces a wave with steep front 

 to pass through the resistance. This, in turn, results in a drop 

 in voltage and gives the transmitted wave a lower value than the 

 incoming, while on the other hand part of the energy of the wave 



is dissipated into heat. The 

 working current, however, passes 

 through the inductance with a 

 negligible drop. This combina- 

 tion is connected in series with 

 the line, as shown. 



Another combination consist- 

 ing of a resistance in series with a 

 condenser or capacitance, but connected between the line wires 

 or between the line wires and ground is shown in Fig. 385. Both 

 of these devices or combinations are particularly effective as 



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FIG. 384. Protective Device, Con- 

 sisting of an Inductance Shunted 

 by a Resistance. This combina- 

 tion is for Series Connection in a 

 Circuit. 



FIG. 385. Protective Device, Con- 

 sisting of a Capacitance in Series 

 with a Resistance. This combi- 

 nation is used in shunt with a 

 circuit. 



