Surge protection of communication equipments for power line communication: Effects on communication signal

The effect on the communication signal by Zener Diodes (ZDs) when connected as surge protection devices in coupling circuits for power line communication (PLC) against common mode and differential mode electrical surges on the power line channel is investigated. Unlike the conventional mode of providing differential mode surge protection only, common mode surge protection was introduced as well. This was done by introducing the grid grounding system to the conventional mode of protection. The results show that with common mode surge protection included, the received signal is attenuated and there is signal drop at certain critical frequency. The ZDs have no significant effect on the received signal when used in the differential mode.