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The harm of lightning to microelectronic equipment has long been familiar to engineers and technicians. For microelectronic equipment, the most harmful is lightning electromagnetic pulse, which is pervasive and implies killing. According to our statistics on relevant accidents, more than 70% of lightning accidents are invaded from the power line, and UPS power supply can not prevent the invasion of lightning current. There are three reasons.
(1) It can be seen from the discussion in 2 that the mains input port of UPS power supply is a filter unit, which generally includes Mei filter and RFI filter. According to the spectrum characteristics of lightning current, more than 90% of its energy is concentrated below 1MHz, and the DC component accounts for more than 60%. When lightning strikes, UPS is located at the front end of the power line and is attacked first.
(2) At present, many ups have added lightning protection function. Its principle is to add a mov lightning protection module at the input end of ups. Some imported famous brand ups and several domestic famous UPS manufacturers have installed lightning protection modules in their ups according to the international iec801-5 standard to suppress the strong surge of lightning voltage and current at the input end of power supply line. The impulse current is 20KA, the impulse voltage is 6kV and the waveform is 8 / 20. However, statistics show that the overvoltage amplitude generated by direct lightning on general low-voltage overhead lines is as high as 100kV, and that of telecommunication lines is as high as 40 ~ 60kV. The maximum amplitude of induced lightning overvoltage is 20kV on unshielded overhead lines and 10kV on unshielded underground cables. If there is no complete lightning protection system designed in accordance with the specifications, even such UPS can not protect electrical equipment from lightning.
(3) UPS power supply, especially intelligent UPS power supply, itself contains a large number of integrated circuits. Moreover, more and more ups are equipped with intelligent management system, and the signal line has also become the channel of lightning electromagnetic pulse intrusion. Because of this, it is common for UPS power supply to suffer from lightning damage, especially in the lightning strike area with more thunderstorm days.
For example, a UPS power supply installed in a unit in Hainan has been running normally for half a year since installation, but after a lightning strike, UPS frequently appears. After starting up and running for a period of time, it inexplicably fails to automatically switch from inverter power supply to AC bypass power supply.
From the types of lightning disaster losses, more than 90% involve computer networks and communication systems, and basically have ups power supply. Therefore, we must pay enough attention to the lightning protection of UPS power supply and its monitoring system.
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