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 |
 Figure 3. Substation line traps |
