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 need to consider the operating system of the transformer. If the company only produces during the day and rests at night, it will be fine. If it is a 24-hour working system, you must be careful about electrical safety.
The specific amount of exceeding 90% is also very important, because the load factor of a normal transformer should not exceed 85%. When it reaches more than 90%, it means that the transformer is running close to full load. Also, the load of electrical equipment will fluctuate at any time. Downward fluctuations are okay, but there is a very high possibility that they will often fluctuate to the rated value or even exceed the rated value, because the normal operating load is already more than 90%, and there is no remaining. The margin is used to cope with the impact current of some impact equipment, such as large electric welding machines, cranes, punch machines, starting of high-power motors and other dynamic loads.
Short-term overloads may often occur. Although the transformer operates overloaded for a short period of time, more frequent overloads will still have an impact on the life of the transformer. Various operating data are close to the rated limits 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 unacceptable levels;
2. The leakage flux density outside the iron core will increase, causing the secondary leakage flux coupling metal parts to heat due to the eddy current effect;
3. As the temperature changes, the moisture and gas content in the insulation and oil will change;
4. Bushings, tap changers, cable terminal wiring devices and current transformers will also be subject to high thermal stress, thus affecting their structure and safety margin.
5. The combination of the main magnetic flux and the increased leakage magnetic flux will limit the over-excitation ability of the core.
Therefore, as current and temperature increase, the risk of premature damage to the transformer increases.
In response to the above situation, we can take the following measures:
1. It is necessary to rationally allocate loads, optimize production processes, allow electrical equipment to be used in an orderly manner, and reduce simultaneous usage.
2. Appropriately increase the low-voltage side output voltage by one level (+2.5%). Since the transformer is close to full load, the voltage at the output end of the transformer will inevitably decrease, which will lead to a lower voltage of the electrical equipment at the end. This will lead to excessive active current and increase power loss. Increasing the voltage can reduce the current.
3. Improve power factor. High load rates will also lead to insufficient reactive power compensation capabilities. Power capacitors that have attenuated capacity should be replaced regularly, and reactive power compensation devices should be installed on-site for large inductive loads to improve the power factor and thereby enhance the active output capability of the transformer. To reduce the operating current and power loss, it can effectively reduce the load current and power loss, thereby reducing the load factor of the transformer.
4. Do a good job in cooling down the transformer. The temperature of the transformer will increase when the transformer is working at a high load rate. Air conditioners can be installed or forced exhaust measures can be added to cool the transformer, thereby reducing losses, improving efficiency and protecting the transformer.
5. Arrange personnel on duty to regularly inspect the operating status of the transformer, record the operating current of the transformer, and measure the temperature of the transformer, so that hidden dangers can be discovered and dealt with early!