Transformer transformation ratio refers to the ratio of the line voltage between the primary and secondary windings during no-load operation. The purpose of measuring transformer voltage transformation ratio is:
1. Check the correctness of the turn ratio of the transformer winding.
2. Check the condition of the tapping points.
3. When a transformer malfunctions, it is common to measure the transformer ratio to check for inter turn short circuits in the transformer.
4. Check if the transformer tap is soldered incorrectly.
5. Inspect the transformer for damage or changes during transportation.
6. Determine whether the transformers can operate in parallel.
When transformers are operating in parallel, ideally, there is no circulating current between transformers operating in parallel. However, in practice, due to the error in transformer ratio and the imbalance of load on the parallel operating bus, there is circulating current between transformers operating in parallel, but it does not affect the normal operation of the transformers. If the voltage adjustment is not done properly, it will cause a large circulating current between transformers operating in parallel, Overtemperature of the transformer endangers its insulation and is not conducive to its safe and economical operation.
According to the power industry standard DL/T 596-2021, there is no significant difference between the voltage ratio of each tap and the nameplate value, and it conforms to the law. The allowable deviation of voltage ratio error for transformers below 35kV with a voltage ratio less than 3 is ± 1%. The allowable deviation of the rated tap voltage ratio for all other transformers is ± 0.5%. The voltage ratio for other taps should be within one tenth of the impedance voltage value (%) of the transformer, but the deviation should not exceed ± 1%.
When measuring the transformation ratio of a transformer, first apply a low voltage of 1-25% of the rated voltage on the high or low voltage side of the transformer, and then measure the voltage on the other side using an instrument or transformer. Determine through calculation whether each winding of the transformer has the rated voltage specified in the technical specifications. When AC voltmeter is used for measurement, the accuracy of the instrument shall be 0.5. When using a voltage transformer for measurement, the accuracy of the transformer should be level 0.2, and the measured voltage value should be selected between 80-110% of the rated voltage of the transformer as much as possible. In addition, using a transformer ratio tester for measurement is more convenient, and the transformer ratio can be directly measured.
The ZC-203AW fully automatic transformer ratio group tester is mainly used to supervise the quality of transformer products during delivery and use, to prevent inter turn short circuits, open circuits, connection errors, internal faults or contact faults of voltage regulating switches. The instrument is easy to operate, has complete functions, stable and reliable data, and has fast testing speed. It meets the needs of various large, medium, and small transformer ratio tests and is an ideal testing instrument for the power industry department.
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