How to handle abnormal temperatures during the operation of power transformer equipment?

When a power transformer operates with abnormal temperature, the principle of "first determine the cause, then handle it by grade, and finally shut down for inspection" should be followed. The priority is to ensure the safety of the equipment and prevent the fault from expanding.

Step 1: Quickly determine the type and cause of the anomaly

• Parameter comparison: Check if the three-phase load current is balanced. If the current in one phase is significantly higher, it may be due to overload or inter-turn short circuit in the winding.

• Environmental inspection: Confirm whether the cooling fan/oil pump is operating normally and whether the radiator is blocked by debris. If the cooling system fails, it is a cooling fault.

• Visual inspection: Check if there is oil leakage from the transformer body or discharge marks on the bushings. If accompanied by an odd smell or smoke, it may be due to internal insulation damage (such as multiple groundings of the core or winding short circuit).

Step 2: Emergency Cooling Measures for Slight Over-temperature

Reduce the load gradually to lower the operating current and heat loss.

Fully put into operation all cooling equipment manually.

Remove sundries on radiators and strengthen ventilation and sunshade.

Increase inspection frequency and continuously monitor temperature changes.

Step 3: Classified Shutdown Control

Reduce load and operate within a limited time

Top oil temperature exceeds 85°C or winding temperature exceeds 95°C.

Partial failure of the cooling system and insufficient heat dissipation.

Continuous and rapid temperature rise.

Immediate power outage and emergency shutdown

Shut down the transformer immediately and report to the dispatching department if any of the following occurs:

• Sudden sharp temperature rise with normal load and cooling system.
• Abnormal internal noise, burning smell, smoke or oil leakage.
• Overheating and discharge of bushings, cracked porcelain parts and severe oil leakage.
• Frequent action of high-temperature alarm and tripping protection.

Step 4: Inspection and Restoration after Shutdown

After the equipment is shut down, it is necessary to conduct a comprehensive inspection in collaboration with professional personnel:

• Oil sample testing: Analyze the dissolved gases in the oil to determine if there is any winding overheating or discharge fault.
• Electrical tests: Measure the winding insulation resistance and DC resistance, check the core grounding current, and locate the internal fault point.
• Repair verification: After replacing the damaged parts (such as cooling fans and insulating components), perform a no-load trial run for 1-2 hours. Only when the temperature stabilizes within the normal range can the equipment be reloaded and put back into operation.