Surge Protector Analysis
Introduction
Lightning disasters are one of the most serious natural disasters. Every year, countless casualties and property losses are caused by lightning disasters around the world. With the extensive application of electronic and microelectronic integrated equipment, the damage to systems and equipment caused by lightning overvoltage and lightning electromagnetic pulses is increasing. Therefore, it is very important to solve the problem of lightning disaster protection for buildings and electronic information systems as soon as possible.
With the increasingly stringent requirements for lightning protection for related equipment, installing surge protectors (Surge Protection Device, SPD) to suppress surges and transient overvoltages on the line and discharge overcurrents on the line has become one of the important links in modern lightning protection technology.
Characteristics of lightning
Lightning protection includes external lightning protection and internal lightning protection. External lightning protection is mainly based on lightning arresters (lightning rods, lightning nets, lightning strips, lightning conductors), down conductors, and grounding devices. Its main function is to ensure that the building body is protected from direct lightning strikes, and to discharge lightning that may hit the building into the ground through lightning rods (strips, nets, wires), down conductors, etc. Internal lightning protection includes measures to protect against lightning induction, line surges, ground potential counterattack, lightning wave intrusion, and electromagnetic and electrostatic induction. The basic method is to use equipotential bonding, including direct connection and indirect connection through SPD, so that the metal body, equipment line and the earth form a conditional equipotential body, and discharge the lightning current or surge current caused by lightning strikes and other surges to the earth, thereby protecting the safety of people and equipment in the building.
The characteristics of lightning are that the voltage rises very quickly (within 10μs), the peak voltage is high (tens of thousands to millions of volts), the current is large (tens to hundreds of kiloamperes), the duration is short (tens to hundreds of microseconds), the transmission speed is fast (propagates at the speed of light), the energy is very huge, and it is the most destructive type of surge voltage.
