In fact, the ultra-low frequency insulation withstand voltage test is an alternative to the power frequency withstand voltage test. In the power frequency withstand voltage test of large and medium-sized generators, motors, power cables and other test objects, due to their large capacitance in the insulation layer, a large capacity test transformer or resonance transformer is required. Some of these huge equipment is not only heavy and expensive, but also inconvenient to use. In order to solve this contradiction, the method of reducing the test frequency and the capacity of the test power supply is widely used in the world. It has been proved from many years of theory and practice at home and abroad that replacing power frequency withstand voltage test with 0.1Hz ultra-low frequency withstand voltage test can not only have the same equivalence, but also greatly reduce the volume and weight of the equipment, theoretically, the capacity is about one fifth of the power frequency, and the operation is simple. This is the main reason why this method is widely used in developed countries.

According to the actual situation of China's power system, the national development and Reform Commission has formulated the industry standard of ultra-low frequency (0.1Hz) withstand voltage test method for 35kV and below XLPE insulated power cables. In 2004, the industry standard DL / T 849.4-2004, general technical conditions for ultra-low frequency and high voltage generators, which is being promoted in China. Although the DC voltage withstand test equipment has the advantages of small size, light weight and low cost, the DC voltage withstand test is also the most destructive to the insulation of the tested object. (see Table 2) therefore, the latest national regulations on preventive test of electrical equipment have expressly stipulated that DC high voltage is no longer used for voltage withstand test of electrical equipment, and AC voltage withstand test is recommended.

The new generation of 0.1Hz ultra-low frequency high voltage generator developed by our company adopts the latest power electronic components and the latest ARM7 single-chip technology, further reducing the volume and weight of the equipment, fool operation, more stable performance, overcoming the shortcomings of the first generation of mechanical booster, such as short service life, high failure rate and large volume. Through years of practice, a large number of user feedback shows that: - 80kV ultra-low frequency high voltage technology is leading in the country, with the highest cost performance!

                                                     Table 2 performance comparison of various withstand voltage test equipment: