UPS protection classes definethe most common types of faults and group them into several protection classes.
The ten most common types of disturbances for UPS systems are mains failures (1), voltage fluctuations (2), voltage spikes (3), undervoltages (4), overvoltages (5), lightning (6), voltage surges (7), frequency fluctuations (8), voltage distortions (9) and voltage harmonics (10).
The UPS protection classes are specified in the standards DIN- EN 5009-6, IEC 62040-3, IEC 61002-2 and VDE 0558. The standards distinguish between three UPS protection classes. The highest protection class is protection class 1, which is resistant to all forms of mains disturbances. Systems with this protection class are independent of the voltage and frequency of the power grid, Voltage and Frequency Independent( VFI). The VFI classification states that the UPS output behaves independently of changes in the mains voltage and frequency.
Protection Class 2 protects against faults 1 to 5 and is independent of the input voltage, Voltage Independent( VI). And protection class 3 protects only against disturbances 1 to 3 and is dependent on the mains voltage and frequency, Voltage and Frequency Dependent( VFD).