The requirements for product selection, pre-commissioning inspection, seal modification and oil injection are similar to those of voltage transformers. Here, only the preventive measures applicable to current transformers are introduced.
The lead joint of the primary terminal of current transformer should be in good contact and the contact area should be sufficient to prevent overheating fault of current transformer. The L2 terminal and the expander cover should be connected with equal potential to prevent potential floating. In addition, there should be anti-rotation measures for the lead-out crucible of the secondary line to prevent the internal lead from being twisted off due to external operation.
When the tg value of dielectric loss factor measured before and during operation is abnormal, the obvious change of tgδ and temperature should be comprehensively analyzed, or when the test voltage rises from 10kv to Um/ root 3 and the increment of tgδ exceeds 0.3%, the operation should be stopped. When the chromatographic analysis results are abnormal, we should follow the comprehensive analysis to investigate its growth trend. If the data grows rapidly, we should pay attention to it. Nip the accident in the bud.
In order to avoid the breakdown accident at the bottom of capacitor core of current transformer, it is necessary to pay attention to the correct installation direction of primary terminals L1 and L2 and the polarity connection mode of secondary winding to ensure the normal operation of bus differential protection.
According to the development of power grid, pay attention to checking the short-circuit current at the location of current transformer, and arrange replacement in time when it exceeds the dynamic and thermal stable current value of transformer nameplate. At present, the on-line monitoring projects of current transformer mainly include: measuring the capacitance and dielectric loss factor tgδ of main insulation, measuring the insulation resistance and dielectric loss factor tgδ of final screen insulation. The test experience shows that it is effective for detecting insulation defects. Infrared temperature measurement has been carried out in some units, and the existing test results show that it is effective for detecting the looseness of internal joints of current transformers, but it still needs to accumulate experience.