（1） Check whether the lead connector in the primary terminal of the transformer is in good contact
The primary terminal lead joint of current transformer shall be in good contact and the contact area shall be sufficient to prevent overheating fault of current transformer. Equipotential connection shall be made between L2 terminal and expander cover to prevent potential suspension. In addition, anti rotation measures shall be taken for the secondary lead out crucible to prevent the internal lead from twisting due to external operation.
（2） Find out the cause of abnormal test value
When the TG value of dielectric loss factor measured before and during operation is abnormal, comprehensive analysis shall be made on the obvious change of TG δ and temperature or the rise of test voltage from 10kV to UM / root 3. When the increment of TG δ exceeds ± 0.3%, the operation shall be stopped. When the results of chromatographic analysis are abnormal, comprehensive analysis should be carried out to investigate the growth trend. If the data increase rapidly, attention should be paid to it. Nip the accident in the bud.
（3） Guarantee normal operation of busbar differential protection
In order to avoid the breakdown accident at the bottom of the capacitor core of the current transformer and expand the scope of the accident, it should be noted that the installation direction of the primary terminal L1 and L2 and the polarity connection mode of the secondary winding should be correct, so as to ensure the normal operation of the bus differential protection
（4） Checking short circuit current
According to the development of power grid, pay attention to check the short-circuit current at the location of current transformer, and arrange the replacement in time when it exceeds the dynamic and thermal stable current value of transformer nameplate.
（5） On line monitoring and infrared temperature measurement.https://www.ctsensorducer.com/