Turn-to-turn insulation defects in dry-type air-core reactors are the main cause of equipment failure.Consequently

we proposed the diagnostic criteria based on oscillation frequency

attenuation coefficient

and standard deviation. For oscillation frequency

if the frequency deviation of the rated voltage and the test voltage is more than 2%

the reactor has a turn-to-turn insulation defect and is in a serious state. If the deviation is between 2% and 1%

the reactor may have turn-to-turn insulation defects and is in an attendant state. If the deviation does not exceed 1%

the reactor is in a normal state. For attenuation coefficient

two criteria such as 5% and 10% are established. For standard deviation

two criteria such as 10% and 30% are established. A standardized judgment flow can be used to assess the turn-to-turn insulation of dry-type air-core reactor

which provides a reference for the operation and maintenance of the reactor equipment.