Grounding / Surge
Lightning protectors (also sometimes called surge protectors or surge arrestors) are devices that are attached to any cable line (both power lines and signal lines) to stop transient power surges, often caused by lightning, while allowing any normal voltages to go through with minimal signal loss. They can range in prices, but are always significantly cheaper than the costs of replacing damaged or destroyed equipment, network downtime, and the potential catastrophes that can occur when control equipment is suddenly unable to function. Lightning protectors are an often overlooked-but absolutely necessary-part of any long term cabling installation. This includes coaxial lines, telephone/DSL/T1 lines, UTP and STP Ethernet LAN cabling, audio/video cabling, 4-20 mA current loop lines, AC/DC control lines, RS422-485 style data lines and even installed USB lines. Virtually any cable with conductive material requires lightning protection as part of the overall system setup. Protectors use a variety of methods to achieve their high quality:
Bidirectional transient voltage suppressor diode arrays: these diode arrays use low line-to-line and line-to-ground capacitance to prevent distortion of high-speed signals but at the same time provide a high clamping voltage which ensures high-power protection.
Gas discharge tubes: these use spark gaps, which are a small number of conducting electrodes separated by a gap filled with a gas. The gap allows the passage of a spark that is created when the voltage difference between conductors exceeds the gap’s breakdown voltage. That voltage creates a low-impedance path and diverts the surge current.
Current limiting series resistors: these simple resistors maintain an even current over time and often act as a “back-up” resistance to limit power dissipation caused by fast diode arrays.