750kV UHV Transformer
The structural characteristics of each part of ODFPS-500000/750GY are as follows:
1.The core is a single-phase, four-limb and unequal MO type. The core section is rationally optimized by the program. The core lamination is made of high-quality silicon lamination with high magnetic permeability and full inclined seam, which has good no-load performance, but requires high processing accuracy. The advanced two-piece-laminated process without laminating upper yoke can greatly reduce the excitation current and reduce the no-load loss. The limb and the yoke are bound with epoxy weft-free glass fiber adhesive tape, which is safe and reliable. The core and the clamp are completely insulated and lead out to the ground through the grounding bushing on the tank to avoid the formation of short-circuit turns.
2.The inner screen continuous coil, transposed conductor and lateral/axial oil passages provided on the coil ensure the heat dissipation of the turns and reduce the temperature rise of the coil. The high-voltage winding and the low-voltage winding have a two-limb series structure, and the medium-voltage winding has a two-limb parallel structure, thereby reducing the outer size of the transformer for transportation. The windings are made of high-quality oxygen-free copper with lower resistivity. The high-voltage winding adopts the tangled type + insertion shielding continuous type, which is characterized by better improvement of the potential gradient distribution of the end line segment under the impulse voltage; the medium voltage winding is the insertion shielding continuous type; the low-voltage winding is a single-spiral type. The ampere-turn distribution of the winding is optimized, and the radial support and axial compression force of the winding are increased; the windings with integral assembly and constant pressure drying processes greatly improves the ability of the transformer to resist inrush current.
3.The main insulation of the coil in the transformer insulation is an insulation structure with a small oil gap in a thin paper tube. In this structure, the thickness of the paper tube is less than 4mm, the width of the oil gap is less than 15mm, and the electrostatic ring is placed at the end of the winding, which can improve the impulse voltage distribution of adjacent line segments and make the electric field at the end of the coil uniform. The transformer is compressed by the cylinder pressing nail device, which can not only ensure the continuous pressure on the winding, but also prevent the damage to the transformer caused by the electric power generated by the winding during short circuit. The jacking device between the transformer and the tank and the positioning device of the transformer are specially treated to completely insulate the transformer and the tank and avoid the formation of short-circuit turns.
4.The high voltage is the middle outlet, the two limbs are connected in series by a pressure equalizing pipe. WEIDMANN's molded insulating parts are used as outlet insulation to ensure the outlet quality.
5.The tank is a bell-shaped structure and the lower tank is a box structure. The fuel tank is reinforced with trough-shaped folded plate reinforced iron. Copper shielding and magnetic shielding are arranged on the tank to effectively shield the leakage magnetic flux entering the tank, reduce stray losses and prevent local overheating.