Research on Overvoltage Prevention Measures for Power Transformer Operation

Research on Overvoltage Prevention Measures for Power Transformer Operation

In the power system, transformers are crucial equipment, and their safe and stable operation has a significant impact on the reliability of the entire power grid. However, transformers may be threatened by overvoltage during operation, which can damage the insulation of the transformer and even cause faults. Therefore, it is particularly important to study the preventive measures for overvoltage during the operation of power transformers.

1、 Reasons for overvoltage during operation

Overvoltage operation is mainly caused by switch operations in the power grid, such as the closing and opening of circuit breakers, which result in sudden changes in system parameters and subsequently trigger electromagnetic energy oscillations. The amplitude of this overvoltage is often high, possibly several times the rated voltage, posing a serious threat to the insulation of the transformer.

2、 Preventive measures

The following preventive measures can be taken against overvoltage during operation:

1. Improving the iron core structure: By improving the iron core structure or selecting high-quality iron core materials, the no-load current can be reduced, thereby reducing the probability of operating overvoltage. For example, cold-rolled grains can be used instead of silicon steel sheets to improve magnetic conductivity and reduce losses.

2. Increase winding capacitance: In transformer design, increasing the winding capacitance appropriately can improve its ability to withstand overvoltage. For example, using a tangled winding can increase the longitudinal capacitance of the winding, allowing the voltage to be evenly distributed between each turn.

3. Use a switch with parallel resistors: By paralleling resistors on the circuit breaker, the magnetic field energy in the inductor can be converted into electrical energy and consumed at the moment of current interruption, thereby reducing the amplitude of overvoltage. This measure has shown significant effectiveness in practical applications.

4. Install zinc oxide lightning arrester: Zinc oxide lightning arrester has excellent nonlinear volt ampere characteristics, which can limit the amplitude of overvoltage. However, it should be noted that the continuous operating voltage value of the lightning arrester should be appropriately selected to avoid overheating damage in the event of a single-phase grounding fault.

5. Adopting R-C resistance capacitance absorption device: This device is composed of capacitors and resistors in parallel. When the vacuum circuit breaker is turned on or off the load, an R-L-C oscillation circuit is formed, which attenuates and oscillates the energy stored in the load inductance at a lower frequency, thereby safely limiting the operating overvoltage to a lower level.

3、 Conclusion

There are various measures to prevent overvoltage during the operation of power transformers, and the appropriate method should be selected according to the specific situation. In practical applications, measures such as improving the iron core structure, increasing winding capacitance, using switches with parallel resistors, installing zinc oxide lightning arresters, and adopting R-C resistance capacitance absorption devices can be comprehensively considered to ensure the safe and stable operation of transformers. Meanwhile, with the continuous advancement of technology, new preventive measures should be actively explored to cope with the increasingly complex power grid environment.