Overview

As noted in Section 1.4 and Section 3.2, it is common to consider separately (1) the lightning protection of a structure and (2) the lightning protection of the electrical power, electronic equipment (e.g., television, DVD, burglar alarm system, computer), and communication systems (e.g., telephone, cable television) located within that structure, although, as we have discussed in Section 3.1, it is preferable to consider the two aspects of protection in a unified way as part of an overall topologically shielded and surge-protected system. The electrical power, electronic equipment, and communication systems within a structure are generally connected to the outside world by conducting wires, primarily 50 Hz or 60 Hz utility power wiring and telephone cables. Outside metallic wires are exposed to direct lightning strikes and suffer significant induced voltages and currents due to lightning occurring with a few hundred meters of those wires. In this chapter we consider primarily the protection of low-voltage systems. By “low voltage” we mean any voltage equal to or below the normal household power level, 480 volts generally being the highest “low voltage” satisfying this definition. In Section 12.2 we will examine the use of surge arresters on distribution and transmission power lines where the voltages may vary from some thousands of volts on distribution lines to about a million volts on transmission lines.

Surge protective devices (SPDs) are known by a number of different names including “arresters,” “surge arresters,” and “lightning arresters.”