A small puddle of oil under a transformer is not just a cleanliness issue; it's the start of a chain reaction: oil level drops, cooling weakens, moisture creeps in, and insulation deteriorates. Treating even the smallest leak seriously is a hallmark of professional transformer maintenance.
Common Leak Locations
| Location | Most Likely Cause |
|---|---|
| Gaskets and seals | Aging and hardening of rubber due to heat and time — the leading cause |
| Radiator connections and valves | Vibration, uneven tightening, corrosion |
| Base of external bushings | Damaged mounting gasket or cracks in the insulator |
| Sampling and drain valve | Poor sealing or damaged seat |
| Tank body and welds | Rust and corrosion, or mechanical damage from transport |
| Tap-changer cover gasket | Frequent opening for maintenance with imprecise reassembly |
Why Is a Leak Actually Dangerous?
- Loss of cooling: A drop in oil level exposes parts of the cooling paths and raises the temperature.
- Moisture ingress: Wherever oil leaks out, humid air can leak in, especially with expansion and contraction cycles.
- Exposure of live parts: In severe cases, the oil level may drop below the point that covers the windings — a direct insulation hazard.
- Environment and safety: Oil is an environmental pollutant and flammable, and its spills are a slip and fire hazard.
The Correct Remedy
- Pinpoint the source accurately (clean the area and observe) — don't just wipe up the accumulated oil.
- Address the cause: replace a gasket, tighten a connection, repair a weld — following the manufacturer's procedures and de-energizing the transformer when necessary.
- Restore the level with oil matching the specification and verify its quality, then monitor the location after the repair.
- Check the level indicator and the Buchholz relay — a severe leak may trigger them.
Sample answer: Three escalating consequences: a drop in oil level weakens cooling, raising the temperature and accelerating insulation aging; moisture and air entering through the leak point reduce the oil's dielectric properties and breakdown voltage; and in severe cases, part of the windings becomes exposed, or the oil level in the Buchholz relay drops enough to trip the transformer — and this may be preceded by a major internal discharge. Add to this the risk of fire and environmental contamination.
Simply refilling the oil without repairing the source of the leak. Repeated refilling treats the symptom while leaving moisture to enter from the same spot, ultimately resulting in oil that fails the BDV test and deteriorated insulation.
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