The capacitive voltage transformer( CVT) is significant for the normal operation of secondary electrical equipment and reliable power systems，so it is necessary to identify the cause and maintenance timely if the running CVTs have unusual situations，which depends on effective techniques of fault detection，fault diagnosis and fault maintenance． Based on the familial fault of a 110 kV CVT which has been detected recently，the fault phenomenon，diagnosis process and final handling measures are provided，the formation reasons of the familial fault are theoretically analyzed，and then the specific heat spot is locked out． It is determined that the cause is failure of factory installation process，thus the investigating and handling methods of the similar fault are sorted out． Finally，combined with routine inspections，infrared temperature measurement，electrical test and work experiences，the references and suggestions for fault diagnosis，operation and maintenance of CVT are proposed．