(1) Check whether the lead connector in the primary terminal of the transformer is in good contact
The primary terminal lead joint of the current transformer must be in good contact, and the contact area should be kept enough to prevent the current transformer from overheating failure. The L2 terminal and the expander cover should be connected with equipotential to prevent potential floating. In addition, there should be anti-rotation measures for the crucibles drawn out of the secondary line to prevent the internal leads from being twisted by external operations.
(B) The abnormal test value should find out the reason
When the measured dielectric loss factor tg value before commissioning and during operation is abnormal, comprehensive analysis of tgδ and temperature changes or test voltage increased from 10kv to Um / root 3, when the increment of tgδ exceeds ± 0.3%, the operation should be withdrawn . When the results of chromatographic analysis are abnormal, it is necessary to follow up the comprehensive analysis and examine the growth trend. If the data grows faster, it should be paid attention to. Eliminate the accident in the bud.
(3) The normal input of the differential protection of the insured bus
In order to avoid expanding the impact scope of the accident at the bottom of the current transformer capacitor core, the installation direction of the primary terminals L1 and L2 and the polar connection of the secondary winding should be correct to ensure the normal input of the bus differential protection run
(4) Checking the short-circuit current
According to the development of the power grid, pay attention to the calculation of the short-circuit current at the location of the current transformer, when it exceeds the dynamic thermal stability current value of the transformer nameplate, it should be replaced in time.
(5) Onboard development of online monitoring and infrared temperature measurement
The current online monitoring projects carried out by current transformers mainly include: measuring the capacitance and dielectric loss factor tgδ of the main insulation and measuring the insulation resistance and dielectric loss factor tgδ of the last screen insulation. Test experience shows that it is effective for detecting insulation defects. For infrared temperature measurement, some units have been launched, the existing test results show that it is effective to detect the loosening of the internal connector of the current transformer. But still need to accumulate experience.