Oil Distribution Transformer Oil Level Abnormal Processing Method

1. Oil Level Monitoring Methods

(1) Glass Tube Oil Level Gauge

• The oil pillow is marked with three oil level monitoring lines, corresponding to normal oil levels at ambient temperatures of -20°C, +20°C, and +40°C.
• Oil level changes with temperature during operation (tied to transformer load, ambient temperature, and cooling system performance)—this is a normal phenomenon.

(2) Magnetic Needle Oil Level Gauge

• The pointer’s standard position at different ambient temperatures is determined by the manufacturer-provided calibration curve.
• Operators must refer to the curve to judge whether the oil level is within the normal range.

2. Abnormal Oil Level: Manifestations, Causes & Handling Measures

2.1 Oil Level Too High

(1) Key Manifestations

• Oil level exceeds the maximum oil level line (corresponding to the current temperature).
• In severe cases, oil fills the oil pillow to the top, and the oil level is no longer visible in the gauge.

(2) Core Causes

• Abnormal operation of the transformer cooler: Poor heat dissipation leads to increased oil temperature, causing oil expansion and rising oil level.
• Over-fueling during maintenance: The initial oil level is excessively high; when ambient temperature rises significantly, the oil expands further, resulting in abnormal high levels.

(3) CHH Power Recommended Handling Steps

• If caused by cooler abnormality:
  1. Inspect the cooler surface for dust accumulation (clean if needed).
  2. Verify that the upper and lower valves of the oil pipe are fully open and the pipeline is unobstructed.
  3. Check if fans and submersible pumps are operating normally, and confirm the cooling medium’s temperature and flow rate meet requirements.
• If caused by over-fueling:
  1. Confirm the oil level is indeed above the maximum line (especially when invisible).
  2. Drain excess oil to the normal level corresponding to the current ambient temperature.

3. Oil Level Too Low

(1) Key Manifestations

• Oil level is significantly lower than the standard line matching the current oil temperature.
• Oil level falls below the minimum line or is invisible in the gauge.

(2) Core Causes

• Transformer oil leakage (severe or slight continuous leakage).
• Initial oil level was too low: Sudden load drop or sharp ambient temperature decrease causes oil contraction, leading to low oil level.
• Extended oil circulation path in forced oil-water cooled transformers: More oil remains in the cooler, reducing the oil level in the oil pillow.

(3) Hazards of Low Oil Level

• Triggers light gas protection action; float relays may cause heavy gas protection to trip.
• Severe oil shortage exposes the core and windings to air, leading to moisture absorption, reduced insulation capacity, and potential insulation breakdown.

(4) CHH Power Recommended Handling Steps

• Minor low oil level (above gas relay): Replenish qualified transformer oil to the normal level immediately.
• Low oil level due to serious leakage:
  1. Do not switch gas protection from “trip” to “signal”—first locate and eliminate the leakage point.
  2. Replenish oil to the normal level after leakage is fixed.
• Severe oil shortage:
  1. Stop the transformer immediately if oil level drops below the gas relay or continues to fall.
  2. Conduct a comprehensive inspection (insulation, seals) before restarting, and replenish oil to the standard level.

4. Critical Safety Notes

• Regularly inspect the oil level gauge for clarity (clean or replace if blurred) to ensure accurate monitoring.
• Record oil level and temperature during routine maintenance to track changes and identify potential issues early.
• Use only CHH Power-approved transformer oil for replenishment—mixed oil types may cause insulation degradation.
• For leakage points that cannot be quickly repaired, arrange for emergency shutdown to avoid catastrophic failures.