How to choose oil-immersed, gas-filled and dry test transformers?

No matter what kind of test transformer, its main function is to test the insulation strength and withstand voltage of electrical equipment, and obtain the insulation performance of electrical equipment and the ability to withstand overvoltage. But its main difference lies in its structure and working principle.

The oil-immersed test transformer is made of high-quality cold-rolled silicon steel sheets. The internal insulation oil is used for insulation and arc extinguishing. The coil is a concentric pagoda-shaped multilayer cylinder, with low-voltage coils inside and high-voltage coils outside. Its working principle is to connect the power frequency 220V (380V above 10kVA) to the control box, which is the supporting equipment for the test transformer. The 0-220V/380V voltage is input into the primary winding of the GDJ test transformer through the automatic voltage regulator. According to the principle of electromagnetic induction, the power frequency high voltage of the secondary (high voltage) winding is obtained according to the ratio of the number of turns of the secondary (high voltage) winding to the primary winding. The oil-immersed test transformer has the characteristics of low cost and low price, and convenient maintenance in the later period, but the disadvantage is that the oil pollution is relatively large and heavy.

The gas-filled test transformer uses SF6 gas to have good insulation and arc extinguishing performance. In order to achieve the purpose of insulation, a large amount of SF6 gas was added to the test transformer. According to the insulation and arc extinguishing properties of SF6 gas itself, gas-filled test transformer has no possibility of reporting discharge even under high voltage conditions, which ensures the accuracy of the test results. However, if the improper use of SF6 gas in the test transformer causes a large amount of volatilization, it will be very troublesome to generate gas in the test transformer, and it generally needs to be sent back to the original manufacturer for processing.

The dry test transformer is a new type of coil epoxy resin vacuum casting and CD core technology. Its basic working principle is: when the input voltage is 200V, when the input voltage is changed as needed by the principle of electromagnetic induction, the output high voltage can be continuously adjusted to the rated value by zero voltage. Because it is integrally formed, it cannot be repaired if the internal damage occurs, and it is relatively heavy and difficult to move.