As an important part of the overall composition of the substation, the main transformer, the YTCDJ series motor withstand voltage test device is divided into integrated and split types, capable of performing AC withstand voltage tests and DC withstand voltage tests on motors. The quality of its installation and operational performance directly affects the safe operation of the substation after construction is completed. Therefore, during installation, it is necessary to strictly follow the safety technical regulations for main transformer installation and carry out high voltage tests properly.
A brief introduction to the key points for the installation of high voltage transformers: ① Insulating oil treatment and testing; ② Vacuuming (improving vacuum degree and extending vacuum holding time) and vacuum oil filling; ③ Partial discharge test or no-load test; ④ Insulating oil withstand voltage must be greater than 70kV/2.5mm; ⑤ For particle size testing, instead of conducting tests, it is necessary to collect information and data in this regard.
During construction, to address the occurrence of cracks in the phase bushings on the high voltage side of the transformer, the cause may be moisture ingress, but if not, a withstand voltage test is required. Due to limitations of test equipment and requirements, the semi-insulated induced high voltage test method is selected. Table 1 provides the AC withstand voltage standards for various parts, and the test requires each component to meet the set values in the table below.
Domestic high voltage transformers are installed and operated with direct grounding or neutral point grounding through an arc suppression coil, which reduces the insulation requirements for the neutral point. Such high voltage transformers are called semi-insulated transformers. In the induced high voltage test, the voltage is distributed along the axial direction and is directly proportional to the total number of turns at the point.
It can be seen that the main insulation of the transformer differs from the longitudinal insulation, and is even quite special. If the external high voltage test method is used, depending on the grounding end of the high voltage coil of the transformer, the test voltage can be achieved, but the line end of the coil cannot; on the other hand, if the line end of the coil reaches the test voltage, the voltage at the grounding end will exceed the test voltage. Therefore, for transformers with semi-insulated neutral points, the single-phase induced high voltage test method should be used instead of the external high voltage method for testing.
