Transformer Oil Filtration in OLTC Systems: A Complete Field Guide

Why OLTC Oil Degrades Faster

Every time a tap changer switches, it creates a small arc. This arc burns the oil. Over time, the oil gets dirty and loses strength. This is why transformer oil filtration is so important. Without it, the tap changer can fail.

Critical Oil Quality Parameters

Before doing transformer oil filtration, you must test the oil. Here are the key tests:

1. Breakdown Voltage (BDV)

This tests the electrical strength. Good oil should be over 40 kV. If it drops below 30 kV, you need transformer oil filtration right away.

2. Moisture Content

Water in the oil is very bad. It ruins the insulation. Vacuum transformer oil filtration removes this water perfectly.

3. Acid Value

High acid means the oil is ruined. Filtration cannot fix high acid. You must replace the oil completely.

The On-Site Filtration Process

When the oil is dirty but not acidic, we can save it. Here is how our team does transformer oil filtration:

Step 1: Isolate and Heat

We lock the power off. Then we hook up our machine. We heat the oil to 60°C. This helps the transformer oil filtration work better.

Step 2: Vacuum Dehydration

We use a high vacuum. This boils the water out of the oil. This step makes the transformer oil filtration very effective.

Step 3: Fine Filtration and Testing

We push the oil through fine filters to catch carbon dust. Finally, we test the BDV again. It must pass before we turn the power back on.

Common Filtration Mistakes

• Bad Vacuum: Cheap machines do not remove water well.
• No Final Test: Always test the BDV after transformer oil filtration. Never guess.
• Filtering Bad Oil: Never filter acidic oil. It will just ruin the tap changer.

Conclusion

Proper transformer oil filtration saves money. It stops surprise outages. It makes the transformer last much longer. Do you need testing or cleaning? Contact our technical team today for professional transformer oil filtration services.