The professional production of high-voltage test transformers in UHV power can help many power workers conduct various power tests more conveniently.
When selecting a test transformer, the following aspects should be considered:
1) Test voltage. According to the requirements of the tested product, first select a suitable voltage test transformer, so that the rated voltage Un on the high voltage side of the test transformer is higher than the test voltage Us of the tested product. Secondly, check whether the low voltage side voltage required by the test transformer can match the on-site power supply voltage and voltage regulator.
2) Test the current. The rated output current In of the test transformer should be greater than the current Is required by the tested product, that is, In>Is. The current required for testing a product can be estimated based on its capacitance, Is=UswCx, where Cx includes the capacitance of the test product and additional capacitance.
3) Testing ability. Based on the rated current and rated voltage output of the test transformer, the capacity of the test transformer can be determined, that is, P=UnIn.
According to relevant standards for test transformers, the voltage levels of test transformers in China are: 5, 10, 25, 35, 50, 100, 150, 300kV, etc; The capacity levels include: 3, 5, 10, 25, 50, 100, 150, 200kVA, etc.
The required test transformer can be selected from the calculation results and relevant standards. If there are special requirements, special specifications of test transformers can be ordered from the manufacturer Wuhan UHV Power for testing.
Example of Transformer Selection for Testing
For example, if the voltage level and capacity of the distribution transformer are 10kV and 1000kVA, and the test products are mostly 10kV, then 50kV and 5kVA test transformers can be selected. Test voltage 30kV; At the same time, it can meet the requirements of 10kV insulator and high-voltage switchgear testing (test voltage 42kV) and 10kV cable DC testing (DC voltage 60kV, corresponding to AC voltage 42.83kV).
In terms of testing capacity, a 10kV, 1000kVA tested transformer has a capacitive current of approximately 80-110mA during charging at 30-35kV testing. Since 35kV x 110mA<5kVA, 5kVA can meet the requirements. For example, for 35kV and 2000-4000kVA transformers, when the test voltage is 72-85kV, the capacitive current is about 150-260mA, 6000-8000kVA is about 300-420mA, 10000kVA is about 800-1000mA, etc. The selected test transformer must have a capacity greater than the current corresponding to the test capacitor mentioned above. The routine test requires that the capacity of the test transformer be 5% of the capacity of the tested product (power transformer).
