I. Classification by Insulation Medium
1. Oil-Immersed
Internal high-performance insulating oil is filled to achieve both insulation and heat dissipation. Through structural optimization, the weight is 10%–20% lighter than that of traditional equipment of the same specification.
Advantages: Stable electrical performance, good heat dissipation, large capacity achievable, mature technology, and high cost performance.
Disadvantages: Risk of oil leakage, more complex maintenance compared to dry type.
2. Dry-Type
The coils are vacuum-poured and sealed with solid insulating materials such as epoxy resin, eliminating the risk of oil leakage. Under the same capacity, the weight is 30%–50% lighter than oil-immersed types, with outstanding portability.
Advantages: Maintenance-free, flame-retardant and explosion-proof, environmentally friendly and safe, high mechanical strength, and resistant to bumps.
Disadvantages: Slightly inferior heat dissipation performance compared to oil-immersed types, and higher cost for large-capacity products.
3. Gas-Filled
High-insulation-strength gases such as sulfur hexafluoride are filled inside, achieving the best lightweight effect, 40%–65% lighter than oil-immersed types of the same grade.
Advantages: Excellent insulation performance, minimal corona, the sealed structure is not affected by harsh environments, and can be used directly on-site without the need for standing time.
Disadvantages: Higher cost, sulfur hexafluoride is a controlled greenhouse gas, and professional equipment and processes are required for recovery and treatment.
II. Classification by Technical Principle
1. Improved Power Frequency Type
Based on the traditional 50-Hz power frequency boost, weight reduction is achieved through optimized magnetic materials, coil structures, and shell materials.
Characteristics: Mature and simple technology, low cost, but limited in weight reduction, and large-capacity equipment is still relatively heavy.
2. Series Resonance Type
A complete set of equipment that uses adjustable inductors and the capacitance of the test equipment to form resonance. The power supply only supplements the loss energy, and the high-voltage energy is exchanged between the inductor and the test sample, significantly reducing the volume of the power supply and the boost transformer.
Characteristics: Widely used on-site, low single-piece weight, suitable for testing large-capacity equipment such as cables and gas-insulated switchgear (GIS).
3. High-Frequency High-Voltage Type
First, the power frequency is rectified to DC, then inverted to several thousand Hertz high-frequency electricity, and boosted through a high-frequency transformer. The higher the working frequency, the smaller the core volume, achieving extreme lightweight.
Characteristics: Compact and lightweight equipment, but complex technology, high cost, and limited capacity, mostly used in special scenarios such as laboratories.
III. Main Application Scenarios
Insulation strength testing of power equipment: Used for AC/DC withstand voltage handover tests of newly installed transformers, switch cabinets, and transformers.
Power cable testing: Suitable for AC withstand voltage tests of medium and low-voltage short cables, and can be used in conjunction with other equipment for DC tests and fault location.
Testing of safety tools: Provides portable high-voltage power sources for the testing of safety tools such as insulating boots and insulating gloves.
Research and teaching: Used as a high-voltage power source in research institutes and university laboratories for basic research and teaching experiments.
IV. Equipment Selection Method
Step 1: Clarify Test Requirements
Determine the higher test voltage based on the voltage level and test standards of the test sample; estimate the required capacity (kVA) based on the capacitance of the test sample, test frequency, and other parameters.
Step 2: Select Technical Route
Long-distance cables, large-capacity generators, gas-insulated switchgear (GIS), and other large-capacity equipment: Prioritize series resonance test devices, which have low requirements for power supply capacity, are lightweight, and have good voltage waveforms, with minimal damage to the test sample when breakdown occurs.
Switches, insulators, short cables, transformers, and other conventional small-capacity equipment: Ordinary power frequency test transformers can be selected.
Indoor, high environmental requirements, and pursuit of maintenance-free and no leakage: Prioritize dry types.
Limited budget, emphasis on stability, and no high requirements for weight: Prioritize oil-immersed types.
Outdoor, humid, dusty, and other harsh environments and frequent handling: Gas-filled or dry types can be selected. Gas-filled is the lightest and has the strongest environmental adaptability but is more expensive; dry types are maintenance-free and have no leakage risk. For outputting DC high voltage (such as cable DC withstand voltage): Choose the oil-immersed AC/DC dual-purpose type with built-in high-voltage silicon stack, which is less prone to damage.
For high voltage levels of 300 kV and above: Use multiple small-capacity test transformers in series excitation combination, with light single-piece weight, facilitating transportation and on-site assembly.
Step 3: Verify parameters and supporting equipment
Confirm that the capacity, voltage, current and other parameters of the selected model meet the test requirements, and provide supporting equipment such as a voltage regulation control cabinet.
Post time: Mar-11-2026