Study on Fault Frequency of Sensitive Equipment Caused by Voltage Sag

A method calculating the fault frequency of sensitive equipment caused by voltage sag in the monitoring period is proposed. In life and production,destruction of sensitive equipment caused by voltage sag is a serious power quality problem. Voltage sag causes the state change of the sensitive equipment from safe state to fault state,which is a transient process and it is uncertain whether the equipment is faulty in the region of the voltage tolerance curve( VTC). In the paper,we use the probability density function to characterize the fault state caused by voltage sag happened in the region of VTC,and use the cumulative method to calculate fault frequency of the sensitive equipment through the voltage sag characteristic parameters in the period of monitoring time. Desktop computers are used as experiment equipment to verify the proposed method,and result comparison with that calculated using the ITIC curve shows the advantage and accuracy of the method.