Voltage transformer burned causes and protective measures - News - Global IC Trade Starts Here Free Products

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A voltage transformer is a type of transformer that includes a core and is mainly composed of a primary coil, a core, and insulation. During the thunderstorm season, faults such as lightning strikes on power lines or flashovers on porcelain insulators can occur, leading to the blowing of high-voltage fuses or even burning out of the voltage transformer. The main causes include:

When a single-phase ground fault occurs on a 10kV outgoing line, the non-fault phase’s voltage relative to ground on the primary side of the voltage transformer equals the normal voltage level. This causes the transformer’s core to saturate quickly, resulting in a sharp increase in excitation current and eventually blowing the fuse.

If there is a short circuit between turns or phases on the secondary side of the voltage transformer, and the low-voltage fuse has not blown, the high-voltage fuse may blow or burn out due to the rapid rise in excitation current.

Due to the capacitive and inductive parameters of the power network, especially ferromagnetic components with iron cores, ferromagnetic resonance can occur when the parameter combinations are unfavorable. If the circuit breaker does not close synchronously, and a no-load busbar with a transformer and a ferromagnetic voltage transformer is energized, the high-voltage winding may short to ground, causing ferromagnetic resonance. When this happens, the overvoltage can exceed 2.5 times the normal value, leading to insulation breakdown and equipment damage.

To protect the voltage transformer, the following measures can be taken:

Strengthen the substation duty system and eliminate the practice of replacing high-voltage fuses with low-voltage ones. Install a zero-sequence grounding automatic switch on the primary side of the voltage transformer to cut off the grounding line. Also, install a small air switch (3~5A) on the secondary side to prevent short circuits in the voltage transformer.