1. Distributiontransformers have no fuses on both high and low voltage sides. Some have drop-out fuses and horn-gap fuses installed, but the fuse wires are often replaced with aluminum or copper wires, so that when a low-voltage short circuit or overload occurs, the fuse cannot blow properly and the transformer burns out. The high and low voltage fuse configurations of distribution transformers are inappropriate. The fuses on transformers are generally oversized, which causes the distribution transformer to burn out when severely overloaded.
2. Due to the large number of rural lighting lines, most of which use single-phase power supply, coupled with the arbitrariness of jumper wires during construction and inadequate management, the distribution transformer load is unbalanced. Over time, the insulation of one phase winding ages and the transformer burns out.
3. Tap changer.
1) Adjusting the tap changer without authorization. Due to the large difference in electricity load between winter and summer, the voltage fluctuates greatly. Therefore, some rural and enterprise electricians adjust the tap changer without testing and adjustment by the power maintenance department, resulting in the tap changer not being in place, poor contact, and burning out.
2) The tap changer has poor quality, unreasonable structure, insufficient pressure, unreliable contact, and the external dial position does not exactly match the internal actual position, causing incomplete contact of the star-shaped moving contact. The misaligned moving and static contacts reduce the insulation distance between the two taps, and under the potential difference between the two taps, a short circuit or discharge to ground occurs. The short-circuit current quickly burns out the tap winding, and may even damage the entire winding.
4. Oil leakage is the most common external abnormality of transformers. Since the transformer body is filled with oil, rubber beads and pads are used at all connection parts to prevent oil leakage. After long-term operation, some rubber beads and pads age and crack, causing oil leakage, which leads to insulation performance degradation after moisture absorption, discharge short circuit, and burning out of the transformer.
5. The high and low voltage lines of distribution transformers are mostly introduced by overhead lines. Due to untimely commissioning of arresters or failure to install 10kV arresters, the transformer burns out when struck by lightning.
6. Some distribution transformers are not equipped with primary protection, or if equipped, the protection's operability and reliability are extremely low, and some even cannot operate at all. This article is from Wuhu HongyeDry-type Transformer
