In power systems, transformers are critical equipment for energy transmission, and their design and performance are essential to the stable operation of the entire system. Short-circuit impedance, as an important parameter of transformers, directly affects their voltage regulation capability, short-circuit current, mechanical stress, and other aspects. Therefore, understanding the role of short-circuit impedance and its impact on transformer performance and cost is crucial for selecting and designing transformers.
When the power factor of the load is fixed, the voltage variation of the transformer is closely related to its short-circuit impedance. Simply put, the larger the short-circuit impedance, the greater the voltage variation, which means a decline in voltage regulation capability. Therefore, transformers with smaller short-circuit impedance are generally more suitable as they exhibit smaller voltage variations and better voltage regulation.
However, the smaller the short-circuit impedance, the greater the short-circuit current when the transformer experiences a short-circuit fault. This not only has a larger impact on the power grid but also increases the stress on switches and protective devices, while the transformer windings will endure stronger mechanical forces under short-circuit conditions, leading to a rapid rise in temperature. Therefore, to control short-circuit current, we prefer the transformer’s short-circuit impedance not to be too low.
For core-type transformers, if the short-circuit impedance increases, the number of winding turns must also increase. This not only increases the weight of the conductors but also affects the leakage flux area, which ultimately leads to an increase in the weight of the core. This means that transformers with high impedance will have higher manufacturing costs.
Additionally, as the short-circuit impedance increases, the transformer’s load losses will also increase, which means more energy consumption during normal operation. Therefore, when choosing the appropriate short-circuit impedance, it is necessary to find a balance between controlling short-circuit current and managing manufacturing costs.
For shell-type transformers, due to the flexibility in the design of their windings, impedance can be adjusted over a wider range without significantly increasing manufacturing costs.
In summary, the short-circuit impedance of transformers not only directly impacts their voltage regulation capability and short-circuit current but also has a significant effect on manufacturing costs and operational efficiency. When designing and selecting transformers, it is essential to consider grid stability, equipment protection, and economic factors. By selecting the appropriate short-circuit impedance, specific application requirements can be met. The design flexibility of shell-type transformers offers a wider range of choices, while core-type transformers require more precise balancing between performance and cost.
