It is an electronic fast transfer switch that realizes the transfer from the inverter output to the bypass or the bypass to the inverter output in the UPS.The transfer time is generally not more than 5ms（1/4 cycle）.

It is a device that prevents current flow from the UPS rectifier to the battery but allows current flow from the battery to the UPSinverter.It will be used if the UPSshares the battery with other systems.

If the UPSoutput current is a periodic non-sinusoidal current，it is the ratio of the peak value of the non-sinusoidal current to its RMS value.The value of the current peak factor reflects the UPS's ability to supply power to non-linear loads.

The time required to switch from inverter supply to bypass supply or from bypass supply to inverter supply.

The ratio of the actual load capacity of the UPS to the rated capacity when the load power factor deviates from the rated power factor of the UPS.

Ice thickness converted into density of 0.9g/cm³ with a return period specified in the design.

Severe wind or ice events，which did occur according to historical records and significantly exceeded the frequency curves recorded over the years.

Load which is likely to be present throughout the service period of overhead transmission line，and for which the variation in magnitude with time is negligible in relation to the mean value，or for which the variation is always in the same direction（monotonic）until the action attains a certain limit value.

Representative value ofvariable load，for which the exceeding probability for the combined load effect in design reference period tends to be consistent with the corresponding probability while the variable load appears alone，or for which the structure designed according to the load combination has a uniformly specified reliability index.

Seismic intensity approved by state authority，taken as the basis for seismic fortification in a certain region，and specified with an exceeding probability of 10％ within 50 years under normal circumstance.