The so-called refusal refers to the situation in which the failure of the line happens but the fault is not reported ; the so-called malfunction refers to the situation in which current mutation in some cases suddenly occurred to the line , the fault indicator mistaken it for the line power fault and reported a failure. Under the satisfaction of our premise of fault criteria, our fault indicator will not maloperate, but may refuse to act. For example, when the circuit fails, the circuit breaker trips, but the mutation of line load current turns out to be 40%, which does not meet the 50% of the standard mutation, and the fault indicator will not report failure as a result. In practical applications, people could adjust the current coefficient of variation and time parameters   according to the line conditions to reduce the possibility of refusal.

    The reason for the occurrence of refusal is that the action value of fault indicator is greater than the substation outlet protection over-current value, as well as quality problems of the fault indicator itself . Omission phenomenon can not be eliminated 100%, but the parameters could be set more reasonable based on your needs, and users could modify the criteria in order to minimize the omission. There are many reasons for the occurrence of maloperation, such as magnetizing inrush current, large load switching, when artificially powered off after big load , large motor inverse feeding. But it could avoid these maloperation through setting up areasonable fault criterias, i that case our fault indicator basically will not maloperate.