IEC 60353: Line Traps — High-Frequency Signal Isolators for Power Line Carrier Communication

How PLC Signals Are “Trapped” on One Line — The Line Trap Working Principle

IEC 60353:1989 specifies line trap requirements. A line trap is a parallel resonant circuit (main coil L + tuning capacitor C) inserted at the HV line exit. At carrier frequency (30–500 kHz), it presents high impedance (≥500 Ω) — blocking the carrier from being shorted to ground by busbar capacitance. At power frequency (50 Hz), it presents low impedance (<0.1 Ω) — transparent to power transmission.

TNLab — The line trap is an elegant frequency-selective device: transparent at 50 Hz, high-impedance at carrier frequencies.