| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a digital protective relay accurately deciding an unbalanced condition even in the case of changing in a quantity of input electricity to reduce an influence due to an error in the quantity of electricity and an input converter. <P>SOLUTION: First/second initial quantities of input electricity V<SB>10</SB>, V<SB>20</SB>are stored as reference values in reference value memory parts 7, 8, change ratios V<SB>1</SB>/V<SB>10</SB>, V<SB>2</SB>/V<SB>20</SB>relating to the reference values of the first/second quantities of input electricity are calculated in a ratio calculating parts 9, 10. An arithmetic part and a decision part compare each change ratio by first/second differential arithmetic operations to detect an unbalanced condition. <P>COPYRIGHT: (C)2003,JPO |
