Power supply lightning protection device use and selection - Database & Sql Blog Articles

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The dangers of lightning for various buildings and equipment are self-evident. Some foreign manufacturers, such as the UK FURSE company, have been committed to research and development to prevent lightning damage, and have been in the history of hundreds of years. In China, many effective protective measures have been taken for the occurrence of direct lightning strikes, but the destructiveness of inductive lightning has only recently begun to attract attention. In fact, the destruction of inductive lightning also causes a lot of damage to each system every year. At present, the information of the meteorological system is mostly transmitted through the computer network. Once the induced lightning damage occurs, the consequences are very serious.

The concept of foreign travel divides lightning strikes into two types: direct lightning and inductive lightning. Inductive lightning refers to the instantaneous overvoltage generated by lightning induced lightning induced current on the power line of the device, that is, the peak surge voltage generated within microseconds to milliseconds (different from the general power supply overvoltage, so the overvoltage may last for several seconds or the above).

According to various world-recognized research standards, the induced current on a typical power line is around 3000 amps, never exceeds 10,000 amps, and the voltage does not exceed 6000 volts. On data/signal lines and telephone lines, the induced voltage is typically around 5,000 volts and the induced current is about a few hundred amps (according to CCITT testing).

General building lightning protection nets can only protect themselves from direct lightning damage, but lightning will destroy electronic equipment through the following forms and ways: First, lightning strikes directly into the power input line, and then enters and damages the equipment. Although various protection gaps and power surge arresters such as isolation transformers are installed on the power transmission line, this can only limit the voltage of the line-to-ground to less than 6000 volts (IEEEC62.41) when the lightning shock wave invades through the transmission line. The line is uncontrollable. The second is inductive, such as: resistive inductive or capacitive coupling to the power supply, signal and telephone line, and ultimately harm the equipment. The electrical switching action is known to generate a magnetic field when the current flows on the conductor, storing the energy. The greater the current and the longer the wire, the more energy is stored. Therefore, when a large load (especially an inductive load such as a transformer) is switched, an instantaneous overvoltage is generated.

The destructive consequences of transient overvoltage are reflected in the following four points:

(1) Signals or data transmitted or stored, whether digital or analog, are subject to interference or loss, and may even cause electronic devices to malfunction or temporarily paralyze.

(2) Since the repetition is affected by a small amount of transient overvoltage, the components are not burned immediately, but the performance and life have been seriously reduced.

(3) If the situation is serious, the circuit boards and components of the electronic equipment will be burned.

(4) The whole system stall caused a lot of indirect losses, such as bank computer service suspension, mobile phone communication suspension, etc., far exceeding the direct monetary loss of the device itself.

The rapid development of highly integrated semiconductor components has made electronic devices smaller in size, but on the other hand they have been more susceptible to transient overvoltages. Although there is currently no universal standard to indicate how much transient overvoltage an electronic device can withstand, according to IEEE, general components can withstand twice their rated voltage. Therefore, a single-phase device can withstand a peak overvoltage of 2×(230V×2×1.1)=700V at 230V ± 10%.

To use the most effective and complete lightning protection function to protect electronic equipment from transient overvoltage caused by inductive lightning or switching action, various transmission lines must be considered, including: power input and output, data, signals and telephone lines. In addition, if there is a program-controlled switch, it is also necessary to install an appropriate lightning protection device. To play a good lightning protection function, a lightning protection device must have the following points:

(I) Compatibility An ideal lightning arrester should not cause any interference or interruption to the equipment or lines it protects.

(B) can withstand high current Although the lightning current can be as high as 200,000 amps, but the general secondary induction current will not exceed 10,000 amps, so the lightning arrester must be able to withstand a minimum of 10,000 amps of instantaneous current.

(3) Low "pass" voltage surge protectors must be able to reduce the instantaneous spike voltage to a range that can be tolerated by general electronic equipment, that is, less than twice the peak voltage of the equipment (about 700V).

(4) Comprehensive protection of the power supply lightning arrester must provide the following protection: relative ground, medium to ground and relative.

(5) The operation status display should be clearly displayed on the panel whether it is in the normal working state, the function is degraded or the fault occurs.

(6) Telemetry function When the lightning arrester fails, the remote monitoring center can be notified of the fault status through the telemetry dry contact.

(7) Repeated use and long life can be used repeatedly after being subjected to multiple lightning strikes under normal use, and its working life must be more than 20 years.