Very Low Frequency Tester
Product Introduction
The VLF Hipot Tester is designed for voltage withstand testing of electrical equipment with large equivalent insulation capacitance. Utilizing digital frequency conversion technology and microprocessor control, it connects the controller to the high-voltage generator via a low-voltage link with photoelectric isolation. The system incorporates a closed-loop negative feedback control circuit between high and low voltage stages, ensuring stable output without capacitive rise effect.
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Technical parameter
| Nguồn cấp | AC220V±5%, 50/60Hz. If using a generator, it must be a digital inverter generator with 220V output and power >8kW. Ordinary generators or UPS power supplies are prohibited. |
| Output Voltage | 30kV, 40kV, 50kV, 60kV, 70kV, 80kV, 80kV, 90kV |
| Tần số đầu ra | 0.1Hz, 0.05Hz, 0.02Hz,0.01Hz |
| Load Capacity | 0.1Hz-0.5μF, 0.05Hz-1.0μF,0.02Hz-2.5μF,0.01Hz-5μF |
| Đo lường độ chính xác | 3% |
| Voltage positive,negative peak error | ≤3% |
| Biến dạng dạng sóng điện áp | ≤5% |
| Operating Environment | Temperature: -10℃~+40℃ |
| Độ ẩm | 85%RH |
Very-low frequency series products
| Model number | Điện áp định mức | Carrying capacity | Power supply fuse | Generator power | Product structure, weight |
| 30/1.1 | 30kV(peak) | 0.1Hz, ≤1.1μF | 10A | >3kW | Controller: 4kg, booster: 25kg |
| 0.05Hz,≤2.2μF | |||||
| 0.02Hz,≤5.5μF | |||||
| 0.01Hz,≤11μF | |||||
| VLF-40kV | 40kV(peak) | 0.1Hz,≤0.8μF | 15A | >4kW | Controller: 4kg, booster: 25kg |
| 0.05Hz,≤1.6μF | |||||
| 0.02Hz,≤4μF | |||||
| 0.01Hz,≤8μF | |||||
| VLF-50kV | 50kV(peak) | 0.1Hz，≤0.7μF | 20A | >5kW | Controller: 4kg, booster: 35kg |
| 0.05Hz，≤1.4μF | |||||
| 0.02Hz，≤3.5μF | |||||
| 0.01Hz,≤7μF | |||||
| VLF-60kV | 60kV(peak) | 0.1Hz,≤0.6μF | 20A | >6kW | Controller: 4kg, booster: 45kg |
| 0.05Hz,≤1.2μF | |||||
| 0.02Hz,≤3μF | |||||
| 0.01Hz,≤6μF | |||||
| VLF-80kV | 80kV(peak) | 0.1Hz,≤0.5μF | 30A | >8kW | Controller: 4kg, booster: 50kg |
| 0.05Hz,≤1.0μF | |||||
| 0.02Hz,≤2.5μF | |||||
| 0.01Hz,≤5μF | |||||
| VLF-90kV | 90kV(peak) | 0.1Hz,≤0.4μF | 30A | >9kW | Controller: 4kg, booster: 55kg |
| 0.05Hz,≤.0.8μF | |||||
| 0.02Hz,≤2.0μF | |||||
| 0.01Hz,≤4μF |
Comparison of mechanical and electronic performance of 0.1Hz voltage test equipment
| 0.1Hz Voltage resistant device type | High pressure control system | High voltage waveform | Energy saving | noise | Mechanical life | Electrical life |
| Mechanical type | High voltage mechanical switch toggles polarity | Square wave | No energy saving: the excess energy is consumed with high-power resistance | high | short | short |
| Electronic type | High voltage electronic switches switch polarity | Sinusoidal wave | Energy conservation: Excess power is fed back into the grid | slight | There is no | long |
Performance comparison of various pressure test equipment
| Comparative content | Power frequency withstand voltage | Variable frequency voltage resistance | Withstand voltage 0.1Hz | Dc voltage resistance |
| equivalence | good | good | good | In general |
| Insulation destructiveness | small | small | small | larger |
| Operational safety | lower | lower | high | lower |
| Test connection | complex | complex | simple | simple |
| Equipment volume | maximum | larger | small | small |
Tính năng sản phẩm
1. High degree of intelligence: adopting digital frequency conversion technology, microcomputer control, fully automatic testing processes such as boost, buck, and measurement.
2. Easy to operate: simple wiring, 7-inch LCD touch screen, convenient operation, friendly human-computer interaction.
3. Comprehensive protection: Multiple protections (overvoltage protection, high and low voltage side overcurrent protection), quick action (action time ≤ 10ms), instrument safety and reliability.
4. Safe and reliable: The controller is connected to the low-voltage generator through photoelectric control, ensuring safe and reliable use.
5. Adopting high and low voltage closed-loop negative feedback control circuit, the output has no capacity rise effect.
6. Accurate sampling: High voltage current and voltage data are directly obtained through high-voltage side sampling, so the data is true and accurate.
7. Fully equipped: 7-inch capacitive touch screen, LCD Chinese character display, automatic storage, and automatic printing.
8. Wide testing range: Multiple frequency options of 0.1Hz, 0.05Hz, 0.02Hz, and 0.01Hz, with a wide testing range.
9. Easy to carry: The instrument has a small size and light weight, making it very suitable for outdoor operation.
10. Multi language display: Chinese English switching function, customizable for other languages.
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Main application areas
1. Power cables. Handover and preventive testing of cross-linked polyethylene (XLPE) cables. The mainstream testing method for 35kV and below cables is to effectively detect insulation defects such as water branches.
2. Rotating motor. Factory and maintenance testing of large generators and motors. Replacing power frequency withstand voltage significantly reduces the demand for large power equipment.
3. Other capacitive devices. Bushings for power capacitors, high-voltage composite equipment (GIS), etc. Solve the problem of large capacitance and inability to bring conventional power frequency testing equipment into the field.
Absolute advantage compared to "DC withstand voltage"
Many experienced electricians used to use DC high-voltage cables for testing, but ultra-low frequency high-voltage generators are an ideal substitute for DC withstand voltage:
No residual charge: DC testing injects a large amount of "space charge" into the cable, which must be discharged after the test, and residual charge may cause breakdown during actual operation. Ultra low frequency is characterized by alternating AC polarity, no accumulation of charge, and can be put into operation without discharge.
High defect detection rate: DC withstand voltage cannot detect mechanical damage or water ingress defects in cable intermediate joints, while ultra-low frequency AC electric field distribution is consistent with actual power frequency operating conditions, which can effectively detect these fatal defects.
Frequently Asked Questions and Answers
Q: Why choose very-low frequency testing instead of power frequency or DC testing? A: Ultra low frequency testing can effectively reduce the capacity requirements of testing equipment, especially for high-capacity specimens such as cables, and can more effectively detect aging phenomena such as water tree effect in insulation.
Q: How to ensure the safety performance of very-low frequency high-voltage generators? A: The equipment of Wuhan UHV Power Technology Co., Ltd. integrates multiple safety protection functions, such as overvoltage, overcurrent, zero voltage starting, automatic discharge, etc., to ensure operational safety.
Q: How to choose the appropriate testing voltage and time when conducting very-low frequency testing? A: This usually requires reference to relevant national standards, industry specifications, or recommended values from equipment manufacturers, and adjustments should be made based on the specific situation of the tested equipment.
Q: What factors will affect the output waveform of the very-low frequency generator? A: The characteristics of the output load, nonlinear factors in circuit design, and external electromagnetic interference may all affect the output waveform.
