Product Details

The ultra-low frequency insulation withstand voltage test is actually an alternative method to the power frequency withstand voltage test. As we know, when conducting power frequency withstand voltage tests on large generators, cables, and other test objects, due to their insulation layers having relatively large capacitance, test transformers or resonant transformers with large capacity 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 the method of 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 test instead of power frequency withstand voltage test can not only have the same equivalence but also greatly reduce the size and weight of the equipment. Theoretically, the capacity is about one five-hundredth of that at power frequency, and the operation is simple, with more advantages compared to power frequency tests. 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 Cross-linked Polyethylene Insulated Power Cables of 35kV and Below." China is promoting this method, and this instrument is developed according to this need. It can be widely used in AC withstand voltage tests of cables and large high-voltage rotating motors.

Three Product Introduction

This product combines modern digital frequency conversion advanced technology, adopts microcomputer control, and the boosting, bucking, measurement, and protection are fully automated. Due to full electronization, it is small in size and light in weight, with a large screen liquid crystal display, 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. At present, mechanical methods are used both at home and abroad for modulation and demodulation to generate ultra-low frequency signals, so there are problems such as non-standard sine wave 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, resulting in high overall power consumption of the equipment. This product can overcome these shortcomings. In addition, it has the following features that need special explanation:

1. Current, voltage, and waveform data are all sampled directly from the high-voltage side, so the data is accurate.

2. It has overvoltage protection function. When the output exceeds the set voltage limit, the instrument will stop for protection, with an action time of less than 20ms.

3. It has 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.

4. The high-voltage output protection resistor is designed inside the boosting body, so there is no need to connect an external protection resistor.

5. Due to the adoption of a high-low voltage closed-loop negative feedback control circuit, the output has no capacitive rise effect.

Four Technical Parameters

1. Output rated voltage: see Table 1

2. Output frequency: 0.1Hz, 0.05Hz, 0.02Hz

3. Load capacity: 0.1Hz   maximum 1.1µF

0.05Hz  maximum 2.2µF

0.02Hz  maximum 5.5µF

4. Measurement accuracy: 3%

5. Voltage positive and negative peak error: ≤3%

6. Voltage waveform distortion: ≤5%

7. Operating conditions: indoor, outdoor; temperature: -10℃～+40℃; humidity: ≤85%RH

8. Power fuse: see Table 1

9. Mains power: frequency 50Hz, voltage 220V±5%. If using a portable generator for power supply, the generator requirements: frequency 50Hz, voltage 220V±5%, power should be greater than 3KW, and a resistive load (such as an electric furnace) with a power of not less than 800W should be connected in parallel at the generator output to stabilize the generator's running speed. Otherwise, the instrument will not work properly.