Instrument Principle:
Such huge equipment is not only bulky and expensive, but also very inconvenient to use. To solve this contradiction, the test frequency is reduced, thereby reducing the capacity of the test power supply. Years of theory and practice at home and abroad have proven that using 0.1Hz ultra-low frequency withstand voltage tests instead of power frequency withstand voltage tests not only provides equivalent effectiveness, but also greatly reduces the size and weight of the equipment. The capacity is about one five-hundredth of that at power frequency, and the test procedure is greatly simplified, offering more advantages compared to power frequency tests. This is why developed countries commonly adopt this method. China's Ministry of Electric Power has commissioned the Wuhan High Voltage Research Institute to draft the industry standard "Test Method for Ultra-Low Frequency (0.1Hz) Withstand Voltage of 35KV and Below Cross-linked Polyethylene Insulated Power Cables," and this method is being promoted in China. This instrument is developed based on this national need and can be widely used in AC withstand voltage tests for cables, large high-voltage rotating motors, and power capacitors.
The 0.1Hz ultra-low frequency high voltage generator is a new type of ultra-low frequency AC test device that mainly uses a cosine square wave as the output source. It is mainly used for non-destructive insulation withstand voltage tests on plastic power cables such as PE (polyethylene) and XLPE (cross-linked polyethylene) in the power sector. It combines modern digital frequency conversion technology, uses microcomputer control, and fully automates voltage boosting, voltage reduction, measurement, and protection, while allowing manual intervention during the automatic voltage boosting process.
When conducting power frequency AC withstand voltage tests on cables and other test objects, due to their insulation layers having relatively large capacitance, large test transformers or resonant transformers are required. Such huge equipment is not only bulky and expensive, but also very inconvenient to use. To solve this contradiction, the power sector has adopted a method of reducing the test frequency, thereby reducing the current and the capacity of the test power supply. Current, voltage, and waveform data are all directly sampled from the high-voltage side, so the data is authentic and accurate.
Features of the 0.1Hz ultra-low frequency high voltage generator:
1. For rated voltages less than or equal to 50kV, a single-stage structure (one voltage booster) is used; for voltages greater than 50kV, a series structure (two voltage boosters in series) is used, greatly reducing the overall weight and enhancing load capacity. Moreover, the two boosters can be used separately for ultra-low frequency tests at lower voltage levels.
2. Digital frequency conversion technology and microcomputer control are adopted, making the test process fully automated.
3. Current, voltage, and waveform data are all directly sampled from the high-voltage side, ensuring accurate data.
4. Small size, light weight, simple wiring, and easy operation.
5. LCD with Chinese character display, automatic storage, and automatic printing.
6. Overvoltage protection: when the output exceeds the set voltage limit, the instrument will shut down for protection, with an action time of less than 20ms.
7. Overcurrent protection: designed with dual protection for high and low voltage sides. The high-voltage side can perform precise shutdown protection according to the set value; the low-voltage side will shut down for protection when the current exceeds the rated current. The action time is less than 20ms in both cases.
8. The high-voltage output protection resistor is designed inside the voltage booster, so no external protection resistor is needed.
9. Due to the adoption of a high-low voltage closed-loop negative feedback control circuit, there is no capacitive rise effect in the output.
10. Four-fold protection with rapid action (action time ≤20ms) for reliable safety.
11. Multiple frequency selection of 0.1Hz, 0.05Hz, and 0.02Hz, providing a wide testing range.
Functions of the 0.1Hz ultra-low frequency high voltage generator:
★ Current, voltage, and waveform data are all directly sampled from the high-voltage side, so the data is authentic and accurate.
★ Overvoltage protection: when the output exceeds the set voltage limit, the instrument will shut down for protection, with an action time of less than 20 milliseconds.
★ Overcurrent protection: designed with dual protection for high and low voltage sides. The high-voltage side can perform precise shutdown protection according to the set value; the low-voltage side will shut down for protection when the current exceeds the rated current. The action time is less than 20 milliseconds in both cases.
★ The high-voltage output protection resistor is designed inside the voltage booster, so no external protection resistor is needed.
★ Due to the adoption of a high-low voltage closed-loop negative feedback control circuit, there is no capacitive rise effect in the output.
