In the field of insulation performance testing of high-voltage power equipment, DC hipot testers are the core equipment for conducting DC withstand voltage tests and leakage current measurements. With the continuous improvement of voltage levels in the power system, how to choose suitable DC hipot testers according to actual needs has become a focus of attention for power workers. Wuhan UHV Power Technology Co., Ltd. (hereinafter referred to as "Wuhan UHV") has systematically sorted out the key elements for selecting DC hipot testers based on years of industry experience and the latest industry standards.
Selection core: dual parameters of voltage and current
Wuhan UHV technology experts pointed out that choosing a DC hipot tester requires starting from two core technical parameters.
Firstly, the rated output voltage. This parameter determines the maximum DC voltage that the equipment can apply, and its determination principle is that it must be greater than the maximum DC test voltage required by the tested equipment, with a certain margin. For example, the DC test voltage for 10kV level cables is about 35kV, and it is recommended to use a 60kV level generator; The test voltage for 35kV level cables is approximately 105kV, and a 120kV level generator should be selected. Wuhan UHVDC high-voltage generator has multiple specifications and models, with rated voltages ranging from 60kV to 600kV, which can meet the testing requirements of various high-voltage equipment.
Next is the rated output current. The rated output current determines the ability of the equipment to drive the load. The demand for current varies greatly among different tested devices: it is recommended to have a current of no less than 3mA for power cable testing, and 5mA or more for long cables; Large capacity equipment such as transformers and generators typically require 10mA or more. The rated current of Wuhan UHVDC high-voltage generator ranges from 2mA to 10mA, and users can flexibly choose according to the actual test object. The rated power is determined by the product of the rated output voltage and the rated output current. Common specifications include 60kV/2mA (120W), 200kV/5mA (1000W), 300kV/5mA (1500W), etc.
According to the selection of the tested equipment: comparison of common application scenarios
The selection requirements for DC hipot testers vary for power equipment of different voltage levels and types. Wuhan UHV has summarized the following common selection comparisons based on industry standards and actual testing experience:
10kV power cable: The DC test voltage is about 30-40kV, and it is recommended to use a 60kV generator with an output current of 3mA or more. Long cables require 5mA or more.
35kV power cable: The DC test voltage is about 105kV, and a 120kV generator should be selected.
10kV distribution transformer: The test voltage is about 30-35kV, and it is recommended to use a 60kV generator with relatively low current requirements.
35kV transformer: The test voltage is about 72-85kV, and it is recommended to use a 120kV generator.
Zinc oxide lightning arrester: U1mA DC reference voltage test and 0.75U1mA leakage current test are required, with high voltage accuracy requirements. It is recommended to choose a model with high-precision 0.75U function button.
110kV and above substations: The range of the generator should be selected according to the highest voltage level of the equipment under its jurisdiction. The specifications required for 110kV substations and 10kV distribution networks are completely different.
Technical indicators: accuracy, ripple, and protection function
In addition to core parameters such as voltage and current, the following key technical indicators should also be considered when selecting:
Voltage and current accuracy: The voltage and current accuracy of Wuhan UHV DC hipot tester is ± (1.0% reading+2 words), ensuring accurate and reliable test data.
Ripple factor: Ripple factor is an important indicator for measuring the stability of DC output voltage. The ripple coefficient of Wuhan ultra-high voltage products is ≤ 0.5%, which is better than the national standard requirement (≤ 3%).
Voltage stability: When the power supply voltage changes by ± 10%, the voltage stability can still be maintained within 1%, ensuring that the test results are not affected by power supply fluctuations.
Protection function: It should have multiple protection functions such as zero protection, overvoltage protection, overcurrent protection, breakdown protection, etc., with fast and reliable action, effectively ensuring personal and equipment safety. The overvoltage setting of Wuhan ultra-high voltage products adopts digital dip switches, which are easy to operate and have high setting accuracy.
0.75 times voltage function: This function is a specialized feature for testing zinc oxide lightning arresters. The high-precision 0.75U single touch button (accuracy ≤ 1.0%) can greatly improve testing efficiency.
Manufacturer selection: equal emphasis on technology and service
As a high-voltage testing equipment, the manufacturing quality of a DC hipot tester directly affects the safety of the test. Wuhan UHV, as a company that has been deeply involved in the field of high-voltage electrical measurement for 22 years, has become a leader in the high-voltage electrical measurement industry. It is understood that its ZGF series DC hipot tester adopts high-frequency voltage doubling circuit and PWM high-frequency pulse width modulation technology, combined with voltage feedback, to greatly improve voltage stability. The equipment utilizes high-performance high-power IGBT devices and driving technology, and adopts special shielding, isolation, and grounding measures based on electromagnetic compatibility theory to achieve high-quality and portable design. The double pressure cylinder adopts electrical insulation and air insulation structure, without any leakage concerns.
Industry experts suggest that when purchasing DC hipot testers, factors such as voltage level, current requirements, technical specifications, safety protection functions, 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 DC 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.
