The hazards of ferromagnetic series resonance in rectifier transformers

Due to differences in length, distance to ground, and wire specifications, 10 kV overhead lines have the condition to form overvoltage, which causes significant changes in the main parameters of some electrical equipment in the 10 kV distribution equipment system, leading to series resonance in the system. After each series resonance, the current of the rectifier transformer increases sharply. At this time, in addition to causing the primary side circuit breaker of the transformer to melt, it will also damage the winding of the transformer, and even cause the waterproof bushing of the transformer to flashover or explode.

Most of the high-voltage and low-voltage lines of rectifier transformers are introduced from transmission lines. When the line is struck by lightning, the winding of the transformer will generate a surge working voltage several times higher than the rated current. If the zinc oxide lightning arrester installed at the waterproof sleeve of the high-voltage and low-voltage group of the distribution transformer cannot provide effective protection or has some hidden dangers, it is inevitable that the rectifier transformer will be damaged by lightning strikes.