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The composition of oil-immersed transformer

Classification:

Industry News

Release time:

2025-03-20

As the core equipment of the power system, the oil-immersed transformer works in coordination with the components to achieve efficient transmission and distribution of electricity. The following is based on key components and analyzes their technical characteristics and functional implementations.

Core structure evolution

In the early days, the overall core was gradually replaced by the stacked silicon steel core due to the large hysteresis and eddy current losses. A high magnetic permeable silicon steel sheet with a thickness of 0.23-0.3mm was used to form it in a 45° oblique seam stacking process, reducing the no-load loss of the iron core by about 35%. After annealing, the magnetic flux density can be increased to 1.7-1.8T, effectively reducing magnetic leakage. Modern iron core grounding design adopts a single-point suspended grounding method, which can suppress circulation problems caused by multi-point grounding.

Coil electromagnetic conversion

The high and low voltage coils adopt a multi-layer cylindrical or continuous winding structure, and 0.3mm thick insulating paper is used for layer isolation. Taking the 110kV transformer as an example, the low-voltage winding uses 8mm×10mm flat copper wire, and the high-voltage winding uses 2.5mm diameter enameled wire, which achieves a voltage adjustment range of ±10% by adjusting the turn ratio. The winding is fixed with epoxy glass cloth plate braces in the axial direction, and an insulating pad with a compression amount of 4% is set radially to ensure structural stability under short circuit current.

Lead connection technology

The transformer with 500kV and above uses copper pipe leads with a diameter of 50mm, a wall thickness of 3mm, and is filled with transformer oil to enhance heat dissipation. The lead joint adopts TIG welding process, and the DC resistance value at the welding is controlled within 1.05 times the resistance of the wire in the same section. The casing lead adopts a capacitive voltage equalization structure, and an 8-layer aluminum foil capacitor screen is installed in the 220kV casing to increase the uniformity of the axial field strength distribution to more than 90%.

Fuel tank cooling system

The wall thickness of the corrugated oil tank is 1.5mm, the wave height is 25mm, and the heat dissipation area is 40% higher than that of the flat plate type. The forced oil circulation cooling system is equipped with 3 submersible oil pumps with a flow rate of 12m³/h, and heat exchange is achieved with 4 sets of radiators. The top oil temperature rise limit is 55K. Through online oil chromatography analysis, characteristic gases such as CO, C₂H₂ can be monitored, and local overheating faults can be warned in advance.