UNINTERRUPTIBLE POWER SUPPLY AND OPERATION METHOD THEREOF

An uninterruptible power supply includes: a battery; an insertion node configured to, when the uninterruptible power supply is coupled to a connection apparatus connected to a first main power line and a second main power line, be electrically connected to the first main power line in the connection apparatus; a power switch configured to connect the connection apparatus and the battery; and a battery management system configured to measure a first voltage of the first main power line through the connection apparatus, turn ON the power switch when the measured first voltage is lower than a predetermined threshold value, measure a second voltage of the insertion node in the ON state of the power switch, and turn OFF the power switch when the measured second voltage is lower than a reference voltage.