Ultra-Low Frequency Insulation Withstand Voltage Test Device integrates modern digital frequency conversion advanced technology, adopts microcomputer control, and fully automates voltage boosting, voltage reduction, measurement, and protection.Due to full electronic design, it is small in size and light in weight, with a large-screen LCD display that is clear and intuitive, and can display output waveforms and print test reports. The design indicators fully comply with the power industry standard "General Technical Conditions for Special Test Instruments for Power Equipment, Part 4: General Technical Conditions for Ultra-Low Frequency High-Voltage Generators", and it is very convenient to use. Currently, both domestic and international methods use mechanical modulation and demodulation to generate ultra-low frequency signals, resulting in non-standard sine waveforms, large measurement errors, spark discharge in the high-voltage part, bulky equipment, and the second and fourth quadrants of the sine wave require high-power high-voltage resistors for discharge shaping, so the overall power consumption of the equipment is relatively high.
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), greatly reducing overall weight and enhancing load capacity. Moreover, the two voltage boosters can be used separately as ultra-low frequency for lower voltage levels.
2. Current, voltage, and waveform data are directly sampled from the high-voltage side, ensuring accurate data.
3. It has 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.
4. It has overcurrent protection: designed with dual protection for high and low voltage. 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, with action times both less than 20ms.
5. The high-voltage output protection resistor is designed inside the voltage booster, so no external protection resistor is needed.
6. Due to the adoption of a high-low voltage closed-loop negative feedback control circuit, the output has no capacitive rise effect.
Ultra-Low Frequency Insulation Withstand Voltage Test Device is actually an alternative method to power frequency withstand voltage testing. We know that when conducting power frequency withstand voltage tests on large generators, cables, and other test objects, due to their insulation layers exhibiting large capacitance, a large-capacity 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 contradiction, the power sector has adopted reducing the test frequency, 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 testing instead of power frequency withstand voltage testing not only has the same equivalence but also greatly reduces the equipment size and weight. Theoretically, the capacity is about one five-hundredth of that at power frequency, and it is simple to operate, with more advantages compared to power frequency testing. This is why developed countries generally adopt this method. The National Development and Reform Commission has formulated the industry standard "Test Method for Ultra-Low Frequency (0.1Hz) Withstand Voltage of 35kV and Below Cross-linked Polyethylene Insulated Power Cables". Our country is promoting this method, and this instrument is developed based on this national need. It can be widely used in AC withstand voltage testing of cables and large high-voltage rotating motors.
