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Time：2025-10-16 13:36:47 Reading volume：
Even new transformer oil can contain moisture and impurities. Discover why filtration before injection is crucial for enhancing insulation strength, preventing aging, and ensuring reliable transformer operation.
New transformer oil may meet factory standards, but it’s not completely pure. During transportation and storage, oil can absorb moisture, dust, and metal particles. These impurities compromise insulation performance, accelerate aging, and increase the risk of failure.
That’s why filtration before oil injection is essential. It removes contaminants, restores insulation properties, and ensures safe commissioning and long-term transformer reliability.
This is the primary goal of pre-injection filtration.
During production and transport, oil often picks up metal particles, fibers, and dust. These can:
Lower insulation strength: Particles form conductive bridges, leading to partial discharge and reduced dielectric performance.
Block heat dissipation: Deposits on windings and cores hinder oil flow, leading to local overheating and accelerated insulation aging.
In addition, transformer oil is hygroscopic, meaning it absorbs moisture from the air. Water contamination:
Reduces breakdown voltage — even small amounts can severely weaken dielectric strength.
Accelerates oxidation — moisture promotes acid and sludge formation.
Degrades insulation paper — moisture-absorbed cellulose permanently loses dielectric capability.
A vacuum oil purifier effectively removes both solid particles and free/bound moisture, ensuring the oil meets commissioning standards.
Even new oil contains dissolved air, primarily oxygen and nitrogen.
Oxygen is the main cause of oil oxidation. It reacts with hydrocarbons to produce acids and sludge, corroding metal parts and reducing heat transfer.
Vacuum filtration removes dissolved gases, especially oxygen, thereby slowing oil aging and extending service life.
This step is critical before injecting oil into large-capacity or high-voltage transformers.
Factory acceptance standards are only a minimum threshold. For safe transformer operation, the oil must meet higher commissioning requirements, especially in high-voltage applications.
| Parameter | Factory Standard | Commissioning Requirement (500kV) | Effect of Filtration |
|---|---|---|---|
| Breakdown Voltage | ≥35 kV | ≥60 kV | Easily improved with vacuum purification |
| Water Content | ≤30–40 mg/L | ≤10 mg/L (≤8 mg/L typical) | Reduced through dehydration |
| Dielectric Loss Factor | ≤0.005 | ≤0.003 | Lowered via degassing and fine filtration |
By filtering new oil, you elevate its quality from “factory clean” to operational-grade purity suitable for field use.
New oil may also contain trace sulfur or chlorine compounds, which corrode copper and silver components and produce conductive residues that risk short-circuiting.
Using adsorptive purification—such as bleaching clay or activated alumina filters—can effectively remove these contaminants, enhancing chemical stability and protecting internal components.
Think of transformer oil as the blood of your transformer. Even “new” oil can carry hidden impurities—just like purified water may not be clean enough for a precision instrument.
Filtration before filling ensures the oil entering your transformer is absolutely pure, protecting critical insulation, reducing aging, and maintaining efficient cooling.
This “final safeguard” establishes the foundation for 30+ years of stable and reliable transformer operation.
For power utilities, transformer manufacturers, and maintenance contractors, the ideal solution is a vacuum oil purifier with:
High-vacuum dehydration and degassing
Multi-stage filtration (1–5 µm accuracy)
Precise temperature control and online operation
Automatic monitoring of temperature, pressure, and moisture
Such systems not only remove water and particles but also restore dielectric strength to above commissioning standards.
Filtering new transformer oil is not an optional step—it’s a necessary guarantee of safety, reliability, and performance.
By using a professional vacuum oil purifier, you can ensure that your transformer’s insulation oil is free from particles, moisture, gases, and chemical contaminants. This simple but essential process extends equipment life, reduces maintenance costs, and ensures uninterrupted power supply for decades.
NSH-VF Vacuum Transformer Oil Purifier
Dual-stage vacuum system
1–5 µm filtration accuracy
Online dehydration and degassing
Automatic PLC control for continuous operation
Ensure your transformer oil meets the highest purity standards—before it enters your equipment.
