Line traps in substations are used to filter and prevent incoming communication signals from passing through the substation. True or False?

• A. True
• B. False
• C. They amplify signals
• D. They convert signals to DC

Answer: (A)

Line traps are tuned devices used with power-line carrier communications. They are installed at the boundary of a substation on lines that carry PLC signals and are designed to present a high impedance to the high-frequency carrier, while allowing the 50/60 Hz power to pass. This arrangement keeps the communication signal on the line and prevents it from entering the substation’s relays and control equipment, protecting the substation from RF interference and unintended actions. They do not amplify signals or convert them to DC; their purpose is selective isolation at the carrier frequency. So the statement is true.