METHOD FOR CALCULATING NUMBER OF HEALTHY STRINGS OF SODIUM-SULFUR BATTERY AND FAILURE DETECTION METHOD USING SAME

A number (uo) of healthy strings of one block in a sodium-sulfur battery is determined according to expression (1), and a failure of the sodium-sulfur battery is detected on the basis of the determination of the value of the uo. This method makes it possible to properly determine a failure of the sodium-sulfur battery, which can be used to compensate for fluctuations of electric power generated by a renewable energy generating device. uo = (Qo/Qs) x us ... (1) where Qs: used capacity of reference block; Qo: used capacity of target block; and us: number of healthy strings of reference block (us¤u).,