By hvhipot 
The VLF Hipot Tester is a high-voltage power supply equipment designed specifically for insulation and voltage withstand testing of power equipment. By outputting ultra-low frequency (0.01Hz-0.1Hz) high-voltage signals, it achieves non-destructive testing of capacitive equipment such as large generators and cables. Its core advantage lies in replacing the large test transformers required for traditional power frequency (50Hz) withstand voltage tests with smaller equipment volume and weight. In theory, the capacity is only 1/500 of that of power frequency equipment, while maintaining equivalent testing results.
The main characteristics of the VLF Hipot Tester are as follows:
1、 Output signal characteristics: the core advantage of adapting to capacitive loads
Ultra low frequency high voltage output
The output frequency is much lower than the power frequency (50Hz/60Hz), with common frequencies of 0.1Hz, 0.05Hz, and 0.02Hz (adjustable according to testing standards).
For high-capacity capacitive loads such as cross-linked polyethylene cables and power capacitors, ultra-low frequency signals can significantly reduce the capacitance current during testing (the lower the frequency, the greater the capacitance impedance, and the smaller the current), avoiding the problem of insufficient equipment capacity caused by high current in traditional power frequency tests.
Wide high-voltage output range and stable waveform
The output voltage can usually reach tens of kilovolts to hundreds of kilovolts (such as 30kV, 50kV, 100kV, etc.), meeting the testing needs of equipment at different voltage levels (such as 10kV cables, 110kV transformer insulation testing).
The output waveform is mostly sine wave or cosine square wave, with low waveform distortion rate (usually ≤ 5%), ensuring the authenticity of the test voltage and reducing the interference of waveform distortion on insulation evaluation.
2、 Equipment performance: efficient, safe, and portable
Small size and light weight, convenient for on-site testing
Compared with traditional power frequency high voltage testing equipment (such as test transformers+voltage regulators), ultra-low frequency high voltage generators do not require large capacity iron core transformers. They use electronic inverter technology, which can reduce their volume and weight by more than 60% (for example, the weight of 100kV equipment can be controlled within 50kg), making them suitable for outdoor cable trenches, substations, and other on-site environments for handling and operation.
Low power design, high energy efficiency ratio
Due to the low charging current of capacitive loads caused by ultra-low frequency signals and the low power consumption of the equipment itself (usually ≤ several hundred watts), it can be powered by AC 220V mains power without the need for a dedicated high-power power supply, reducing on-site power supply requirements.
Multiple security protections, reliable operation
Equipped with overvoltage protection, overcurrent protection, short circuit protection, zero position protection and other functions: when the output voltage/current exceeds the set value, the load is short circuited, or the output terminal does not return to zero position when turned on, the equipment will immediately cut off the output and give an alarm to prevent equipment damage and personnel electric shock.
Some high-end models are equipped with remote control functions (such as wireless remote control and computer software operation), allowing operators to complete tests at a safe distance, further enhancing safety.
3、 Test Applicability: Targeted Solutions for Insulation Testing Pain Points of Capacitive Equipment
High equivalence, in line with international testing standards
Research has shown that the breakdown characteristics of insulation media under ultra-low frequency high voltage are equivalent to those of power frequency high voltage (especially for oil paper insulation and polymer insulation materials), and the test results can effectively reflect the insulation defects of equipment (such as partial discharge, aging cracks).
Compliant with multiple international/domestic standards, such as IEC 60840 (high voltage cables), GB/T 12706 (cross-linked polyethylene insulated cables), etc., it is widely recognized as an alternative to voltage withstand testing for capacitive equipment.
Minor damage to equipment, suitable for preventive testing
The ultra-low frequency high voltage has a short duration of action (usually 1 minute, 5 minutes, or 15 minutes per test, much shorter than the duration of the power frequency test), and the voltage application process is gentle, which can reduce the “cumulative damage” to the insulation material. It is suitable for regular preventive testing of operating equipment and extend its service life.
4、 Operation and data processing: high degree of intelligence
Automated testing process
Supporting preset testing programs (such as setting voltage values, frequencies, and durations), the equipment can automatically complete processes such as boosting, stabilizing, timing, and lowering, reducing human operational errors.
Data recording and analysis function
Built in data acquisition module, which can record output voltage, current, test time and other parameters in real time, and generate test curves (such as voltage time curve, current time curve) through the display screen or supporting software, making it easy to analyze the trend of insulation resistance changes and judge the insulation status.