Current, voltage and combined transformers, oil-paper or gas insulated up to 800 kV.
Line Traps are used in power line communications to prevent undue loss of carrier signal power and to minimize interference from carrier signaling systems on adjacent transmission lines.
They present high impedance at the carrier frequency band (40 to 500 kHz) thus preventing signal power loss. In addition, the impedance at the power frequency (50 or 60 Hz) is negligible, in order to avoid interfering with the power transmission.