Field failure analysis on transmission data equipment due to lightning discharges

The telecommunication equipments suffer more damages, dues to lightning and power lines induction, than other type of appliances. The cause is that they have direct connections with wires or cables that are exposed to transients, and usually the affected components have direct connections with external lines, but sometimes the mechanism is more subtle and can affect circuits without contact with exposed connections.This paper treats about failures on data interfaces circuits induced by voltage transients on the earth protection wire. It is based on a study of modems failures connected to remotes data terminals through RS-232 interfaces. Other data interface could also be damaged by this mechanism of failure (RS-422, Ethernet, Token Ring, etc.).On this type of failure the failed circuits (drivers and receivers RS-232) are not located nearly the transient entry gate (telephone line and VAC inputs). They are in an interface between two equipments, and usually the only failed components are the drivers and receivers.