The principle and selection of the discharge tube make
1, product description The ceramic gas discharge tube (Surge Arrester) is the most widely used switching device in lightning protection equipment, whether it is lightning protection for AC and DC power supplies or various signal circuits For lightning protection, it can be used to discharge lightning current into the ground. Its main features are: large discharge current, small inter-electrode capacitance (≤3pF), high insulation resistance (≥109Ω), large breakdown voltage dispersion (±20%), slow response speed (the fastest is 0.1～0.2 μs). According to the number of electrodes, there are two types: two-pole discharge tube and three-pole discharge tube (equivalent to two two-pole discharge tubes in series). Its shape is cylindrical, with lead and without lead (some also have a protection card for short-circuit when overheating).
2. Working principle The gas discharge tube is composed of two electrodes separated by a certain distance in a ceramic tube filled with inert gas. The electrical performance basically depends on the gas type, gas pressure and electrode distance. The gas filled in the middle is mainly neon or argon, and keep a certain pressure. The electrode surface is coated with an emitter to reduce the electron emission energy. These measures make the operating voltage can be adjusted (generally 70 volts to several thousand volts), and can be maintained within a certain error range. When the voltage at both ends is lower than the discharge voltage, the gas discharge tube is an insulator (resistance Rohm>100MΩ). When the voltage at both ends rises to greater than the discharge voltage, arc discharge occurs. After the gas is ionized and discharged, it changes from high impedance to low impedance, so that the voltage at both ends drops rapidly, about tens of volts. When the gas discharge tube is subjected to a transient high-energy impact, it can change the high impedance between its two poles into a low impedance at a speed of 10-6 seconds, and pass a surge current of up to tens of kiloamps.
Post time: Aug-19-2020