| 摘要 |
A fault current detection device which, in order to take into consideration a record in the past of a load current up to a time instance when a short-circuit is caused, operates, every sampling period DELTA t, a variable DELTA In=f(In, Jn-1) representatve of the record obtainable as a function of an instantaneous current value In at nth sampling time and a parameter Jn-1 obtained by weighting the load current within a preceding specified time period is featured by that the parameter Jn-1 is substituted by the present current value In when a variation of current is in a decreasing direction and that a variable DELTA In=f(Dn, DELTA In-1) obtainable as a function of a current varying rate Dn at nth sampling time and a variable DELTA In-1 representative of a current varying rate at (n-1)th sampling time is calculated every sampling period DELTA t with variable DELTA In being zero when Dn is negative.
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