What are the transformer oil filtration procedures?

The transformer oil filtration procedure is a key step to ensure oil performance and extend equipment life. It is mainly divided into three stages: pretreatment, deep purification, and inspection and acceptance. The following is a detailed process and precautions:

Preparation before transformer oil filtration

1. Oil sample detection

- Take samples to test the moisture content, acid value, dielectric strength, and particle contamination of the oil (reference standards: GB/T 7595, IEC 60422).

- Determine the type of contamination (such as moisture, particles, oxidation products).

2. Equipment inspection

- Ensure that the oil filter (usually a vacuum oil filter) is clean, and the filter element and seals are intact.

- Check whether the pipes and valves are leaking, and the vacuum pump oil level is normal.

3. Environmental requirements

- The operating environment humidity is ≤70%, and the temperature is ≥10℃ (to prevent secondary moisture absorption).

- Fire and explosion prevention measures (especially when vacuum filtering oil).

Transformer oil filtration procedure

1. Pretreatment stage (coarse filtration)

- Purpose: Remove large particles and free water.

- Method:

- Filter through a plate oil filter or a centrifugal oil filter, with an accuracy of ≤20μm.

- If the oil contains a lot of water, it can be heated to 50-60℃ (not exceeding 65℃) to reduce viscosity.

2. Deep purification stage (vacuum dehydration and precision filtration)

- Core equipment: vacuum oil filter (must meet GB/T 14541 standard).

- Steps:

1. Heating: Oil temperature is controlled at 50-65℃ (too high will accelerate oxidation).

2. Vacuum dehydration:

- Vacuum degree ≤-0.095MPa, break the water and gas in the oil.

- Increase the surface area of the oil film through the atomization device to improve the dehydration efficiency.

3. Precision filtration:

- Use high-precision filter elements with β≥200 (such as 1-5μm) to remove tiny particles.

- The filter element needs to be replaced regularly (blockage is indicated when the pressure difference is ≥0.3MPa).

3. Circulation filtration

- Circulate the transformer oil between the equipment and the oil storage tank 3-5 times until the index meets the standard.

- Key indicators:

- Moisture content ≤10ppm (ultra-high voltage transformer requires ≤5ppm).

- Breakdown voltage ≥60kV (new oil standard ≥70kV).

- Particle size ≤NAS 1638 level 6.

Online filtration (optional)

- Continuously filter the transformer oil in operation through the bypass system to keep the oil quality stable.

Post-filtration inspection and acceptance

1. Sampling inspection

- Take samples after standing for 12 hours to test the dielectric strength, moisture, acid value, and dielectric loss factor (tanδ).

2. Acceptance criteria

- Comply with GB/T 7595-2017 "Transformer Oil Quality in Operation" or user-specified standards.

3. Record archiving

- Save the test reports and operation logs before and after filtration.

Precautions

1. Safety risks

- Air infiltration is strictly prohibited during vacuum oil filtration to prevent oil oxidation.

- Avoid local overheating during heating (oil temperature ≤ 65℃).

2. Environmental protection requirements

- Waste oil and waste filter elements are treated as hazardous waste (refer to the "National Hazardous Waste List").

3. Equipment maintenance

- Clean the oil filter after each use and ｒｅｐｌａｃｅ the worn filter element.

Common problem handling

- Oil emulsification: Use a demulsifying oil filter or add a demulsifier.

- Low filtration efficiency: Check the performance of the vacuum pump, the blockage of the filter element, or whether the oil temperature is too low.

- Dielectric strength does not meet the standard: Repeat vacuum dehydration or ｒｅｐｌａｃｅ the adsorbent (such as silica gel, molecular sieve).

If more specific operating parameters are required (such as oil standards for transformers of different voltage levels), further explanations can be provided!