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DOUBLE-ENERGY TRANSIENTS. 63

oscillating voltages, that is, acts as a short circuit for the trans-
former oscillation, and therefore protects the latter. Inversely,
if the large oscillating current of a cable enters a reactive device,
as a current transformer, it produces enormous voltages therein.
Thus, cable oscillations are more liable to be destructive to the
reactive apparatus, transformers, etc,, connected with the cable,
than to the cable itself.

A transmission line is intermediate in the values of ZQ and j/o
between the cable and the reactive apparatus, thus acting like a
reactive apparatus to the former, like a cable toward the latter.
Thus, the transformer is protected by the transmission line in
oscillations originating in the transformer, but endangered by the
transmission line in oscillations originating in the transmission
line. _

The simple consideration of the relative values of ZQ ** y ^ in

the different parts of an electric system thus gives considerable
information on the relative danger and protective action of the
parts on each other, and shown the reason why some elements, as
current transformers, arc far more liable to destruction than others;
but also shows that disruptive effects of transient voltages,
observed in one apparatus, may not and very frequently do not
originate in the damaged apparatus, but originate in another
part of the system, in which they were relatively harmless, and
become dangerous only when entering the former apparatus.

26. If there is a periodic transfer between magnetic and dielec-
tric energy, the transient current i. and the transient voltage 6
successively increase, decrease, and become ssero.

The current thus may bo represented by

i » i₀ cos ($ - 7), (12)

where to is the maximum value of current, discussed above, and

4>~2irjl₉ (13)

where / » the frequency of this transfer (which is still undeter-
mined), and 7 the phase angle at the starting moment of the
transient; that is,

ii «= ig cos 7 » initial transient current. (14)

As the current i is a maximum at the moment when the magnetic
energy is a maximum, and the dielectric energy aero, the voltage e



	*DOUBLE-ENERGY TRANSIENTS.* 63 oscillating voltages, that is, acts as a short circuit for the trans- former oscillation, and therefore protects the latter. Inversely, if the large oscillating current of a cable enters a reactive device, as a current transformer, it produces enormous voltages therein. Thus, cable oscillations are more liable to be destructive to the reactive apparatus, transformers, etc,, connected with the cable, than to the cable itself. A transmission line is intermediate in the values of ZQ and j/o between the cable and the reactive apparatus, thus acting like a reactive apparatus to the former, like a cable toward the latter. Thus, the transformer is protected by the transmission line in oscillations originating in the transformer, but endangered by the transmission line in oscillations originating in the transmission line. _ The simple consideration of the relative values of ZQ y ^ in the different parts of an electric system thus gives considerable information on the relative danger and protective action of the parts on each other, and shown the reason why some elements, as current transformers, arc far more liable to destruction than others; but also shows that disruptive effects of transient voltages, observed in one apparatus, may not and very frequently do not originate in the damaged apparatus, but originate in another part of the system, in which they were relatively harmless, and become dangerous only when entering the former apparatus. 26.** If there is a periodic transfer between magnetic and dielec- tric energy, the transient current i. and the transient voltage 6 successively increase, decrease, and become ssero. The current thus may bo represented by i » i₀ cos ($ - 7), (12) where to is the maximum value of current, discussed above, and 4>~2irjl₉ (13) where / » the frequency of this transfer (which is still undeter- mined), and 7 the phase angle at the starting moment of the transient; that is, ii «= ig cos 7 » initial transient current. (14) As the current i is a maximum at the moment when the magnetic energy is a maximum, and the dielectric energy aero, the voltage e