There are many reasons for transformer short circuit, which are mainly divided into the following two categories: one is structural short circuit factors; the other is operational short circuit factors. They are explained below:

Structural short circuit

(1) Temperature and winding method are important factors causing short circuit of transformer. Temperature has a great influence on the curvature and strength of the conductor. As the temperature of the conductor increases, its curvature and strength decrease to varying degrees. At the same time, the elongation of the conductor will also decrease. The design of the wires in the transformer is usually carried out at normal temperature without taking into account the actual operating conditions. The winding temperature of the actual rated operating transformer is much higher than normal temperature and can reach more than 100°C. As the winding temperature increases, its bending strength and tensile strength will decrease significantly. Loose winding and poor solidification measures between wires and turns make the wires prone to deformation during operation, causing short circuits in the transformer.

(2) Different wire types have different effects on the short circuit of the transformer. Due to its poor mechanical strength, ordinary transposition wires often deform and expose copper under the action of external forces. Under the rated current, the two parts with larger torque include the climbing area of the transposed wire and the wire cakes at both ends of the winding. The direct result of the large torque is that the wire is twisted or even deformed, which greatly increases the risk of short circuit inside the transformer. Flexible conductors are the main cause of early transformer short circuits. Due to lack of understanding and cost issues, manufacturers use soft wires instead of hard wires during production, making transformer short circuits caused by wire types a major cause.