Instrument Principle:
Such huge equipment is not only bulky and expensive, but also very inconvenient to use. To solve this problem, 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 the 0.1Hz ultra-low frequency withstand voltage test can replace the power frequency withstand voltage test, not only with the same equivalence, but also with greatly reduced equipment size and weight, with a capacity about one five-hundredth of the power frequency, and the test procedure is greatly simplified. Compared with the power frequency test, it has more advantages, which is why developed countries generally adopt this method. China's Ministry of Electric Power has commissioned the Wuhan High Voltage Research Institute to draft the industry standard "Ultra-Low Frequency (0.1Hz) Withstand Voltage Test Method for 35kV and Below Cross-linked Polyethylene Insulated Power Cables". This method is being promoted in China, and this instrument is developed according to this need. It 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 mainly a new type of ultra-low frequency AC test device that uses a cosine square wave as the output source. It is mainly used for non-destructive insulation withstand voltage tests of PE (polyethylene)/XLPE (cross-linked polyethylene) plastic power cables in the power sector. It combines modern digital frequency conversion technology, adopts microcomputer control, and the voltage boosting, voltage reduction, measurement, and protection are fully automated, and manual intervention can be carried out during the automatic voltage boosting process.
When performing power frequency AC withstand voltage tests on cables and other test objects, due to their large insulation capacitance, a large test transformer or resonant transformer is required. Such huge equipment is not only bulky and expensive, but also very inconvenient to use. To solve this problem, the power sector has adopted a reduced test frequency, thereby reducing the current and the capacity of the test power supply. The current, voltage, and waveform data are all directly sampled from the high-voltage side, so the data is true and accurate.
Features of the 0.1Hz ultra-low frequency high voltage generator:
1. For rated voltage less than or equal to 50kV, the ultra-low frequency adopts a single-stage structure (one voltage booster); for greater than 50kV, it adopts a series structure (two voltage boosters in series), which greatly reduces the overall weight and enhances the load capacity. Moreover, the two voltage boosters can be used separately as ultra-low frequency for lower voltage levels.
2. Digital frequency conversion technology is adopted, with microcomputer control, and the test process is fully automated.
3. The current, voltage, and waveform data are all directly sampled from the high-voltage side, so the data is accurate.
4. Small size, light weight, simple wiring, and convenient operation.
5. LCD Chinese character display, automatic storage, and automatic printing.
6. Overvoltage protection function: 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 function: designed as dual protection for high and low voltage. The high-voltage side can perform precise shutdown protection according to the set value; when the current on the low-voltage side exceeds the rated current, shutdown protection will be performed, with action times all less than 20ms.
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), ensuring reliable protection.
11. Multiple frequency selection of 0.1Hz, 0.05Hz, and 0.02Hz, with a wide test 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 true 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 as dual protection for high and low voltage. The high-voltage side can perform precise shutdown protection according to the set value; when the current on the low-voltage side exceeds the rated current, shutdown protection will be performed, with action times all less than 20 milliseconds.
★ 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.
