Harmonics in a power system can have several effects on transformer stray losses. Stray losses, also known as eddy current losses and hysteresis losses, are caused by the alternating magnetic fields present in transformers during operation. These losses are undesirable as they result in energy dissipation and reduced transformer efficiency. Harmonics can exacerbate these losses in the following ways:
Increased Eddy Current Losses: Harmonic currents flowing through the transformer windings induce additional eddy currents in the conductive materials (such as the core and windings) of the transformer. Eddy currents circulate within the conductive materials and cause resistive losses, leading to increased heating and energy loss.
Increased Hysteresis Losses: Harmonic voltages cause the magnetization curve of the transformer core to deviate from its ideal behavior, resulting in increased hysteresis losses. Hysteresis losses occur due to the repeated reversal of magnetic domains in the core material, and the deviation from the ideal magnetization curve leads to higher energy dissipation.
Overloading of Transformer: Harmonics can cause transformer overloading, even when the fundamental frequency load is within acceptable limits. This is because the stray losses caused by harmonics add to the losses from the fundamental frequency, leading to an overall higher loss.
Resonance: Harmonics can create resonance conditions in the transformer winding and core. Resonance amplifies the effects of harmonics, leading to significantly higher stray losses and potential mechanical stress on the transformer structure.
Reduced Transformer Lifespan: The increased heating due to harmonic losses can accelerate aging and insulation degradation within the transformer. This can result in a shorter lifespan and increased maintenance requirements for the transformer.
Voltage Distortion: Harmonics can cause voltage distortion, which may lead to increased load current harmonics. The distorted load current further contributes to higher transformer stray losses.
To mitigate the effects of harmonics on transformer stray losses, various measures can be taken, such as:
Installing harmonic filters: These devices are designed to reduce harmonic currents and voltages in the power system, thereby reducing the impact on the transformer.
Using low-harmonic or harmonic-resistant transformer designs: Manufacturers can design transformers with materials and construction methods that minimize the impact of harmonics on stray losses.
Implementing harmonic mitigation strategies: Power system engineers can employ harmonic analysis and management techniques to identify harmonic sources and take appropriate corrective actions.
It's essential to consider harmonics and their effects during the design, installation, and operation of transformers, especially in systems with a significant presence of non-linear loads that generate harmonics, such as power electronics-based equipment (e.g., computers, variable speed drives, etc.).