Coupling capacitors are used to transmit communication signals to
transmission lines. Some are used to measure the voltage in transmission
lines. In signal transmission the coupling capacitor is part of a power line
carrier circuit as shown in the schematic below. A coupling capacitor is
used in this circuit in conjunction with a line trap. Line traps can be
installed at the substation or on a transmission line tower.
 Figure 1. Power line carrier schematic showing use of coupling capacitors
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 Figure 2.
Primary coupling capacitor
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 Figure 3.
Substation line traps
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