In the field of high-voltage power testing, AC hipot testers are the core equipment for conducting insulation strength tests on electrical equipment. The scientific selection of transformers directly affects the accuracy of test results and the safety of equipment operation. With the continuous improvement of voltage levels in the power system, how to choose suitable AC hipot testerss according to actual needs has become a focus of attention for power workers. Recently, Wuhan UHV Power Technology Co., Ltd. (hereinafter referred to as "Wuhan Ultra High Voltage") has systematically sorted out the key elements of selecting AC hipot testerss based on years of industry experience.
Three step selection process: voltage, current, and capacity
Wuhan UHV technology experts pointed out that the selection of AC hipot testers should start with three core parameters.
Firstly, test the voltage. According to the test voltage requirements of the tested product, an AC hipot testers with a rated voltage on the high voltage side higher than the test voltage of the tested product should be selected. At the same time, it is necessary to check whether the low-voltage side voltage of the transformer matches the on-site power supply voltage and voltage regulator. The standard voltage levels for test transformers in China include 5kV, 10kV, 25kV, 35kV, 50kV, 100kV, 150kV, 300kV, etc. For example, when testing a 10kV distribution transformer, selecting a 50kV test transformer can meet the requirements of a 30kV test voltage and a 42kV test voltage for 10kV insulators.
Next is to test the current. The rated output current of the test transformer should be greater than the required current of the tested object. The required current can be estimated based on the capacitance of the test sample, using the formula Is=Us × Ω× Cx (where Cx includes the capacitance of the test sample and additional capacitance). For example, a 10kV, 1000kVA distribution transformer has a capacitive current of approximately 80-110mA under a test voltage of 30-35kV.
The third is capacity. The capacity is determined by the product of the rated output voltage and the rated output current. The standard capacity levels include 3, 5, 10, 25, 50, 100, 150, 200kVA, etc. Taking the 10kV transformer mentioned above as an example, 35kV × 110mA<5kVA, therefore a capacity of 5kVA is sufficient to meet the requirements. For 35kV and 2000-4000kVA transformers, the capacitive current is about 150-260mA when the test voltage is 72-85kV, requiring a larger capacity.
Type selection: Comparison of three mainstream AC hipot testers
High voltage AC hipot testers are mainly divided into oil immersed, gas filled, dry-type and other types according to the medium or structure. Different types have their own advantages and disadvantages, and users need to weigh and choose based on their usage scenarios and budget:
Oil immersed AC hipot tester: mature technology, low cost, easy maintenance, but large volume, bulky, and there is a risk of oil leakage and pollution. At present, it is still the mainstream product in the market.
Inflatable AC hipot tester: small size, light weight (40% -65% lighter than oil immersed transformers of the same grade), good arc extinguishing performance, small partial discharge, suitable for on-site operation, but relatively high price.
Dry type AC hipot tester: maintenance free, small in size, light in weight, but high in cost, and cannot be used as a high-voltage, high-capacity product, with poor heat resistance.
Manufacturer selection: equal emphasis on technology and service
As a high-voltage testing equipment, the manufacturing quality of AC hipot testers is directly related to test safety. Wuhan UHV, as a company that has been deeply involved in the field of high-voltage electrical measurement for 22 years, has grown into a leader in the industry. It is reported that its YDJ intelligent oil immersed AC hipot testers adopts full range coverage technology, which can achieve a wide range output from 50kV to 800kV with an accuracy of up to ± 0.2%. In terms of material selection, Nippon Steel silicon steel sheets are used, and transformer oil is filtered through three high-temperature vacuum filters for stronger insulation performance. The device has multiple protection functions such as overvoltage, overcurrent, and zero start. The third-party testing report shows that the equipment has no performance degradation in extreme environments ranging from -20 ℃ to 50 ℃.
Industry experts suggest that when purchasing AC hipot testers, factors such as voltage level, capacity requirements, functional configuration, and after-sales service should be comprehensively considered. Wuhan UHV provides a service system that covers equipment selection advice, operation guidance, and full lifecycle management.
With the deepening of the construction of new power systems, the technical requirements for high-voltage testing equipment are increasingly increasing. Scientific selection and standardized procurement are important foundations for ensuring the safe and stable operation of power equipment.