Then reduce voltage to 0.75U1mA, read leakage current. If leakage current >50μA, it is usually judged as unqualified. DC withstand voltage for cables (gradually reduced but still in demand): Note: For cross-linked polyethylene (XLPE), industry standards (such as GB 50150) no longer recommend DC withstand voltage (it is easy to cause space charge accumulation leading to breakdown after commissioning), and it is recommended to use series resonance AC withstand voltage instead. However, for oil-paper insulated cables, DC withstand voltage is still an effective method. Generator/transformer leakage current test: Measure leakage current at different voltage levels (such as 0.25Un, 0.5Un, 0.75Un, 1.0Un), draw V-I curve, and judge whether the insulation has linear or nonlinear defects. 5. Safety and operation precautions (crucial) Full discharge: After DC high voltage test, a large amount of charge will remain on the test object. It must be discharged through a resistor using a special discharge rod, and then directly grounded. Direct short-circuit discharge is strictly prohibited to prevent damage to the test object or injury to personnel. Reliable grounding: The grounding terminal of the instrument, the grounding terminal of the voltage doubling cylinder, and the grounding terminal of the test object must share a common ground and have good contact; otherwise, high-voltage back-strike or data drift may occur. Microammeter protection: When measuring small leakage current (μA level), the microammeter is easily disturbed or burned out. Be sure to use shielded wires and confirm the range before raising voltage. Environmental humidity: When air humidity is too high (>80%), surface flashover is prone to occur at the high-voltage end. A grading ring should be installed or the test should be conducted in dry weather. Summary and recommendations Conventional configuration: For most power supply bureaus and industrial/mining enterprises, configuring a 200kV/5mA DC high voltage generator (such as Wuhan Ultra-high Voltage ZGF-200kV) can cover the arrester and equipment testing needs of 110kV and below systems. Trend: Prefer models with touch screen control, wireless remote control, and automatic protection functions, and avoid purchasing old analog instruments with potentiometer adjustment. Warning: If you mainly perform withstand voltage tests on 10kV/35kV cross-linked cables, please carefully consider the DC high voltage generator. It is recommended to consult series resonance withstand voltage devices to comply with the latest national standards. Do you need a selection scheme for a specific voltage level (such as "220kV substation"), or do you want to understand the specific arrester test wiring diagram? DC High Voltage Generator, commonly known as "direct high voltage generator" or "DC withstand voltage tester", is the core equipment in the power system for DC withstand voltage tests and leakage current measurement of high-voltage electrical equipment (such as arresters, cables, transformers, generators, etc.). It is one of the most effective means to judge the insulation strength of equipment and discover concentrated internal defects (such as cracks, bubbles) in insulation. Especially for the DC reference voltage (U1mA) and leakage current test at 0.75U1mA of zinc oxide arresters (MOA), it is the only designated standard instrument. Combined with the latest technical standards and market trends from 2025 to 2026, the following is an in-depth analysis: 1. Core functions and testing principles Main uses: Zinc oxide arrester test: Measure DC reference voltage (U1mA) and leakage current to judge whether the arrester is damp or aged (this is the most frequent application scenario of the direct high voltage generator). DC withstand voltage for power cables: Although AC withstand voltage (series resonance) is now more recommended for cross-linked polyethylene (XLPE) cables, DC withstand voltage is still used in some old standards or specific diagnostics to check insulation defects. Other equipment: DC leakage current test for transformers, generators, and circuit breakers to evaluate overall insulation condition. Working principle: It adopts a high-frequency voltage doubling rectifier circuit. The industrial frequency AC (220V/380V) is inverted to high frequency and boosted, and then a stable DC high voltage is output through the voltage doubling rectifier circuit. Advantages: Compared with traditional industrial frequency test transformers, high-frequency technology reduces the equipment volume by 60%-80%, significantly reduces weight, and has a smaller ripple coefficient. 2. New technical trends from 2025 to 2026 With the advancement of materials science and power electronics technology, the new generation of DC high voltage generators has the following characteristics: Maturity of medium/high frequency inverter technology: It has fully replaced the old industrial frequency silicon stack rectification. The switching frequency is increased to 20kHz-100kHz, making the transformer and filter capacitor extremely small in size. The whole machine can be carried by one person (the weight of a 60kV/2mA model can be controlled within 5kg). Intelligent control and protection: Automatic voltage boosting: Preset voltage and current upper limits, one-click automatic voltage boosting, timing, and voltage reduction, without manual adjustment of potentiometers. AI overvoltage/overcurrent protection: Millisecond response. Once the test object breaks down or the leakage current exceeds the limit, the high voltage is immediately cut off and locked to prevent equipment damage. Zero-position start: It is mandatory that the voltage regulator can only start at zero position to prevent misoperation. High-precision measurement and display: It adopts a 32-bit ARM processor and 24-bit AD chip, with voltage/current measurement accuracy reaching 0.5 level or even 0.2 level. It is equipped with a 7-inch high-definition touch screen, real-time display of V-I curve and waveform, supporting data storage and USB export. Multiple protection designs: Waterproof and dustproof: The protection level of mainstream models reaches IP65, suitable for harsh outdoor environments such as rain, snow, humidity, and dust. Reverse connection protection: The instrument refuses to start when the grounding wire is not properly connected or the polarity is reversed. 3. Mainstream brands and selection guide in the market China's DC high voltage generator industry is highly concentrated. Wuhan, Hubei is the absolute core production area (accounting for more than 70% of the national share), followed by Baoding, Hebei and Yangzhou, Jiangsu. First tier (industry benchmark, many entries in State Grid/China Southern Power Grid) Wuhan Ultra-high Voltage Electric (TECHHIGH): Status: Industry leader, extremely high product stability. Features: Its ZGF series (such as ZGF-200kV/5mA) adopts imported power devices, with ripple coefficient <1%, and data remains stable in strong electromagnetic interference environments. Widely used in 500kV and above substations. Advantages: After-sales network covers the whole country, with sufficient spare parts. Wuhan Moen Intelligent Electric (MOEORW): Features: High degree of intelligence, friendly human-machine interaction interface. Its MEZGF series supports Bluetooth connection to mobile APP, allowing remote monitoring of the test process, suitable for digital team building.
