The power transformer is a critical component in the transmission and distribution of electrical energy, serving as the central node in the power grid. Its stable and reliable operation directly affects the quality of power supplied to users and the overall security of the system. The reliability of a transformer is not only influenced by its design, manufacturing quality, and materials but also significantly impacted by maintenance practices. This document explores the challenges and solutions related to improving the short-circuit resistance of transformers in power systems.
**I. Overview of Power Transformers**
Electronic power transformers utilize power electronics to convert low-frequency signals into high-frequency signals on the primary side. These signals are then coupled through an intermediate high-frequency isolation transformer to the secondary side, where they are converted back to the desired frequency, voltage, and waveform. This process allows for efficient energy transfer and improved performance. The size of the isolation transformer depends on factors like core material saturation and temperature limits. By increasing the operating frequency, the core's utilization improves, reducing the transformer’s size and enhancing efficiency.
**II. Measures to Improve the Short-Circuit Resistance of Power Transformers**
Ensuring the safe, efficient, and reliable operation of a transformer requires attention to both its manufacturing quality and operational environment, as well as proper maintenance. This section outlines strategies to prevent sudden faults during operation and maintenance.
Short-circuit incidents in the power grid often result from lightning strikes, relay protection failures, or other external causes. These events can cause severe damage to transformers. While 80% of short-circuit failures are attributed to manufacturing defects, only 10% are due to operational errors. This chapter focuses on maintenance and operational measures that can help reduce such risks.
(1) **Standardized Design and Manufacturing**: Transformer manufacturers must prioritize mechanical strength and short-circuit resistance during the design phase. During production, precise control over coil compression is essential. Insulating press plates and shared pressure plates require careful handling to ensure uniform compression and alignment. Proper drying and pressure application during assembly help maintain structural integrity.
(2) **Short-Circuit Testing**: Regular testing helps identify potential weaknesses in the transformer’s structure. By simulating short-circuit conditions, engineers can assess the transformer’s ability to withstand stress and improve its design accordingly.
(3) **Reliable Protection Systems**: A robust relay protection and automatic reclosing system is crucial for minimizing damage during short-circuit events. However, repeated reclosing after a fault may worsen the situation. Therefore, it is important to test the transformer after a trip and avoid unnecessary reclosures in certain cases.
(4) **Winding Deformation Diagnosis**: After a short-circuit, transformer windings may deform, even if no immediate damage is visible. This deformation can lead to insulation issues and partial discharges, which may eventually cause major failures. Frequency response analysis and capacitance measurements are useful tools for detecting early signs of winding damage.
(5) **Enhanced On-Site Inspection and Maintenance**: Strict adherence to installation guidelines and regular inspections are vital for preventing short-circuit incidents. Ensuring that the protection system is reliable and conducting post-trip tests can significantly reduce the risk of further damage.
In conclusion, the ability of a transformer to withstand short-circuit currents depends largely on its design, manufacturing quality, and maintenance practices. Effective control measures across all stages—from design to operation—are essential to ensure the safe and stable functioning of the power grid.
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