In recent years

the premise of voltage sag mitigation for sensitive industrial processes is to reasonably assess the economic losses due to voltage sag

while

voltage sag immunity time of the insensitive process is the key information of the assessment system. For improving the practicality of the immunity time assessment method of process sag

the concept of response information flow is proposed in this paper and

on this basis

a kind of process immunity time assessment method based on equipment immunity is proposed. This method takes the sag sensitive industrial processes as a combined system. According to the function of each part of the system and the response characteristics of voltage sag

it can be divided into such three modular combinations as delayed structure

competitive structure and conductive structure and the response propagation delay of each module is characterized. According to the delay time and module combination characteristics of module response to the voltage sag

the propagation path of response information flow due to sag can be determined and the process immunity time can be evaluated. Finally

it is stated by the actually measured case analysis that the proposed method can be applied to the sensitive process immune time assessment.