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0.1HZ ultra-low frequency high voltage generator
NegotiableUpdate on 05/20
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Overview
When testing the 10KV cable of a 0.1HZ ultra-low frequency high-voltage generator, a single-phase test should be conducted with a voltage set at 18KV and frequencies set at 0.1Hz (recommended), 0.05Hz (recommended), 0.02Hz (slow boosting process), and 0.01Hz (slow boosting process, 10-40 minutes, suitable for cables over 10 kilometers)
Product Details
In the power system, the health status of cables is directly related to the stable operation and power supply reliability of the grid. For long-distance and large cross-section high-voltage cables, traditional power frequency withstand voltage tests are gradually being replaced by ultra-low frequency (VLF) high-voltage generators due to the large size of the testing equipment, high cost, and difficulty in implementing them on site. Especially the ultra-low frequency high-voltage generator has received widespread attention and application due to its advantages.
Product Introduction
0.1Hz ultra-low frequency high-voltage generatorCombining modern digital frequency conversion technology, adopting microcomputer control, automatic boosting, lowering, measurement, and protection, and capable of manual intervention during the automatic boosting process. Due to full electronicization, it has a small size, light weight, large screen LCD display, clear and intuitive, and printer output test reports. The design indicators comply with the power industry standard of "General Technical Conditions for Special Test Instruments for Power Equipment, Part 4: General Technical Conditions for Ultra Low Frequency High Voltage Generators", and are very convenient to use. Nowadays, both domestically and internationally, mechanical methods are used for modulation and demodulation to generate ultra-low frequency signals, resulting in non-standard sine wave waveforms, large measurement errors, spark discharge in the high-voltage part, bulky equipment, and high-power high-voltage resistors for discharge shaping in the second and fourth quadrants of the sine wave. Therefore, the overall power consumption of the equipment is relatively high. This product can overcome some of these shortcomings, and in addition, there are the following features that need to be specifically explained:
The current and voltage data are directly obtained through high-voltage side sampling, 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 20ms.
★ Overcurrent protection: Designed as a dual protection system for high and low voltage, the high voltage side can provide precise shutdown protection according to the set value; When the current on the low-voltage side exceeds the rated current, a shutdown protection will be implemented, with an action time of less than 20ms.
The high-voltage output protection resistor is designed inside the boost body, so there is no need to connect another protection resistor externally.
Due to the use of high and low voltage closed-loop negative feedback control circuits, there is no capacitance rise effect in the output.
Principle of ultra-low frequency insulation withstand voltage test
The ultra-low frequency insulation withstand voltage test is actually an alternative method to the power frequency withstand voltage test. We know that when conducting power frequency withstand voltage tests on large generators, cables, and other test samples, large capacity test transformers or resonant transformers are required due to the large capacitance of their insulation layers. These huge devices are not only bulky and expensive, but also very inconvenient to use. In order to solve this contradiction, the power department has adopted reducing the testing frequency, thereby reducing the capacity of the testing power supply. From years of theoretical and practical experience both domestically and internationally, it has been proven that replacing the power frequency withstand voltage test with a 0.1Hz ultra-low frequency withstand voltage test not only achieves the same equivalence, but also greatly reduces the size and weight of the equipment, with a theoretical capacity of about one fifth of the power frequency. The experimental procedure is greatly simplified and has more advantages compared to power frequency testing. That's why developed countries generally adopt this method. The Ministry of Electric Power of our country has commissioned 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 our country, and this instrument has been developed according to the needs of our country. It can be widely used in AC withstand voltage tests for cables, large high-voltage rotating motors, and power capacitors.
10.1Hz ultra-low frequency high-voltage generatorBasic concepts
It is a device used for partial discharge detection and voltage withstand testing of high-voltage cables. Compared with traditional 50Hz or 60Hz power frequency withstand voltage testing, ultra-low frequency testing has the following significant advantages:
Small size and light weight: Due to the use of ultra-low frequency technology, the required energy is reduced, making the equipment more compact, easy to carry and use on site.
Strong applicability: Especially suitable for long-distance and large cross-section high-voltage cables, it can effectively detect defects in the cable insulation layer.
High safety: The lower frequency reduces potential harm to the human body and also lowers the energy consumption of the device itself.
Good detection effect: Ultra low frequency signals are more likely to penetrate the insulation layer of cables, improving the sensitivity of defect detection.
2、 Working principle
Ultra low frequency withstand voltage testerConvert the input AC power into a sine waveform output with a frequency of 0.1Hz through an inverter. The specific process is as follows:
Rectification and filtering: Firstly, the AC power supply is converted into DC power through a rectifier bridge, and then smoothed and filtered through a large capacity capacitor.
Inverter boost: Then use an inverter circuit to convert DC power into 0.1Hz low-voltage AC power, and then boost it to the required high voltage level through a boost transformer.
Output control: Control the magnitude and duration of the output voltage through a microprocessor to ensure the safety and accuracy of the testing process.
3、 Main features and advantages
High precision output: Adopting excellent digital control technology to ensure the stability and smoothness of the output voltage.
Multi functional integration: In addition to basic withstand voltage testing, it also has functions such as partial discharge detection and leakage current measurement.
Intelligent protection: Built in multiple protection mechanisms such as overvoltage, overcurrent, and short circuit, effectively preventing the occurrence of accidents.
Human computer interaction: equipped with a touch screen operation interface, simple and intuitive, supporting data recording and remote monitoring.
Strong adaptability: can be applied to various types of cables, including cross-linked polyethylene (XLPE), oil paper insulation, etc.
4、 Application scenarios
Ultra low frequency withstand voltage testerWidely used in multiple fields of the power system:
Cable manufacturer: used for quality inspection before leaving the factory to ensure that each cable meets the standard requirements.
Power company: Conduct voltage withstand tests before and after cable laying to verify the electrical performance of the cables.
Maintenance and repair: Regularly inspect cables in operation, promptly identify and address potential faults.
Research institutions: provide reliable experimental platforms for cable material research and new technology development.
5、 Precautions for use
althoughUltra low frequency withstand voltage testerIt has brought a lot of convenience, but the following aspects still need to be noted during use:
Equipment inspection: Before each use, a comprehensive inspection of the equipment should be conducted to ensure that all components are intact and undamaged.
Environmental factors: Avoid conducting experiments in thunderstorm weather or temperature conditions to prevent any impact on test results.
Cable preparation: Before the test, the cable end should be cleaned to remove impurities such as grease and dust, ensuring good contact.
Data recording: Detailed recording of data from each experiment to provide a basis for subsequent analysis and decision-making.
