How to ensure the safe operation of miniature current transformer

- Aug 26, 2020-

The requirements of miniature current transformers in product selection, testing before commissioning, sealing reform, oil injection, etc. are similar to voltage transformers. In addition, we also need to master some explosion prevention measures for miniature current transformers. First check whether the lead joints in the primary terminals of the transformer are in good contact.

The primary terminal lead joint of the miniature current transformer must ensure good contact, and the contact area should be sufficient to prevent the miniature current transformer from overheating failure. The L2 terminal and the expander cover should be connected with equipotential to prevent potential suspension . In addition, there should be anti-rotation measures for the crucibles leading out of the secondary line to prevent the internal leads from being twisted by external operations.

When the measured dielectric loss of the micro current transformer before commissioning and during operation is abnormal due to the value, it should be comprehensively analyzed and its obvious change with temperature or the test voltage rises from 10kv to Um/root 3, and the increment exceeds ±0.3%. Quit running. When the results of chromatographic analysis are abnormal, it is necessary to follow up the comprehensive analysis and examine its growth trend.

In order to avoid expanding the impact scope of the accident at the bottom of the capacitor core of the miniature current transformer, 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 protection of the bus differential put into service. According to the development of the power grid, pay attention to the calculation of the short-circuit current at the location of the miniature current transformer, and when it exceeds the dynamic thermal stability current value of the transformer nameplate, it should be replaced in time.

The on-line monitoring project of the miniature current transformer mainly includes 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. They are effective for detecting insulation defects.