If The Transformer Current Exceeds 90%, What Happens To Long-term Operation?

The operating current on the high-voltage side of the transformer accounts for more than 90% of the rated current, which should be better understood. In this case, we also have to consider the operation system of the transformer, if the enterprise only produces during the day and rests at night. If it is a 24-hour working system, then you must be careful and pay attention to the safety of electricity.
It is also important to exceed 90%, because the load rate of normal transformers should not exceed 85%. At more than 90% of the time, it means that the transformer is running at close to full load. Also, the load of electrical equipment will fluctuate at any time, downward fluctuation is good, but there is a very large possibility that it often fluctuates to the rated value or even exceeds the rated value, because the normal operation of the load has been more than 90%, there is no remaining margin to deal with the impact current of some impact equipment, such as large welding machines, driving, punches, high-power motor starting and other dynamic loads.
There may often be short-term overload phenomenon, although the transformer operation is overloaded for a short time, but the more frequent overload will still have an impact on the life of the transformer. Various operating data close to the rated limit of the transformer, coupled with long-term operation, the transformer is bound to have the following problems:
1. The temperature of windings, clamps, leads, insulation and transformer oil will increase and may reach an unacceptable level;
2. The leakage flux density outside the core will increase, so that the secondary leakage flux coupled metal parts will heat up due to the eddy current effect;
3. With the change of temperature, the moisture and gas content in the insulation and oil will change;
4. Bushings, tap-changers, cable termination wiring devices and current transformers will also be subjected to high thermal stress, which will affect their structure and safety margin.
5. The combination of the main magnetic flux and the increased leakage flux will limit the overexcitation ability of the core.
Therefore, as the current and temperature rise, the risk of premature transformer failure increases.