The reason why UPS power supply cannot block lightning current
1. The UPS power supply is installed at the front end of important equipment, so when lightning strikes the low-voltage power line or induces lightning on the cable, the overcurrent and overvoltage on the power wire pass through the distribution system and first impact the UPS. The voltage regulation range of UPS is generally between 160-260V for single-phase and 320V-460V for three-phase. It is impossible to prevent the overvoltage amplitude of lightning impulse waves of 10~20kV in an instant, so when lightning strikes, it is the first to be impacted by lightning current.
2. UPS power supplies with lightning protection devices installed internally are divided into two types:
1) UPS equipped with non-standard lightning protection devices. These are products made by manufacturers to save costs by symbolically installing a set of low-power metal oxide zinc varistors MOV, which can only provide some protection against small induced lightning.
2) Some imported UPS and UPS produced by well-known domestic UPS factories are installed with standard lightning protection devices according to the international IEC801-5 standard (to suppress strong surges of lightning voltage and current at the input end of the absorption power supply line, with a surge current of 20kA, a surge voltage of 6kV, and a waveform of 8/20 μ s).
And whether this type of UPS can protect the UPS itself well and achieve the purpose of protecting other subsequent power sources and equipment from lightning damage, long-term monitoring statistics show that direct lightning strikes can generate overvoltage amplitudes of up to 100kV in general low-voltage overhead lines, 40-60kV in telecommunications lines, and up to 20kV in unshielded overhead lines and 10kV in unshielded underground cables. Therefore, it can be seen that even UPS equipped with standard lightning protection devices, without effective high-energy lightning protection devices installed at the front end of its power lines (distribution rooms, rooms, cabinets, and boxes), this type of UPS will still be damaged by lightning strikes.
3. In intelligent UPS power supplies, some signal interfaces or communication line interfaces for remote control do not have surge circuits, while others only have low-power surge suppression circuits, which cannot prevent induced lightning strikes. Therefore, their signal or communication line interfaces have become the main channels for lightning wave intrusion.
Based on the above analysis, UPS power supplies without installed lightning protection devices can be said to have no lightning protection function, and can only purify and protect the power supply against overvoltage or small stray currents in the municipal power grid. When lightning strikes, it is the first to be damaged; UPS equipped with lightning protection devices cannot fully protect itself and protect the power supply of other equipment from lightning damage; The direct lightning overvoltage and induced lightning overvoltage invading from overhead power lines and signal lines are the main causes of damage to intelligent UPS. Therefore, it is necessary to strengthen lightning protection measures for UPS power supplies, and it also has important practical significance.
