What Is Over Fluxing Protection In Transformer

Overfluxing protection in transformers is a safeguard mechanism designed to prevent damage caused by excessive magnetic flux within the transformer core. When a transformer is subjected to overfluxing, the magnetic flux density in the core exceeds its rated limit, leading to saturation and potential overheating of the core and windings. Overfluxing can occur due to various factors, including system overvoltages, load fluctuations, transformer energization, or improper operation of voltage control devices.

The primary purpose of overfluxing protection is to detect and mitigate conditions that could lead to core saturation and overheating, ultimately safeguarding the transformer from damage and ensuring its safe and reliable operation. Overfluxing protection typically relies on one or more of the following techniques:

1. Buchholz Relay: The Buchholz relay is a common device used for detecting internal faults, including overfluxing, in oil-immersed transformers. The relay is installed in the transformer's oil-filled conservator tank and is sensitive to gas and oil flow. When excessive gases or oil flow are detected, indicating internal faults or overfluxing, the Buchholz relay activates an alarm or trips the transformer to prevent further damage.

2. Differential Protection: Differential protection compares the currents entering and leaving the transformer windings to detect internal faults or abnormalities. By monitoring the asymmetry in current flow, differential protection can detect overfluxing conditions caused by short-circuits, turns-to-turn faults, or other internal faults. Differential protection schemes may incorporate specific algorithms or settings to detect and respond to overfluxing events.

3. Voltage Control Devices: Automatic voltage control devices, such as on-load tap changers (OLTCs) or under-load tap changers (ULTCs), are used to regulate the voltage levels applied to the transformer windings. By adjusting the tap positions based on load and system conditions, voltage control devices help prevent overfluxing by maintaining the magnetic flux within safe operating limits. OLTCs and ULTCs may be equipped with protective features to detect overfluxing conditions and initiate corrective actions, such as tap change blocking or automatic tap adjustment.

4. Alarm and Monitoring Systems: Transformer protection and monitoring systems may include alarms, sensors, and monitoring devices to detect abnormal operating conditions, including overfluxing. These systems may measure parameters such as core temperature, winding temperature, oil temperature, and oil flow rate to identify signs of overfluxing and trigger appropriate responses, such as alarm notifications, load shedding, or tripping of the transformer.

5. Thermal Modeling and Analysis: Advanced protection systems may utilize thermal modeling and analysis techniques to predict and assess the thermal performance of transformers under different operating conditions. By simulating the temperature distribution within the transformer components, these systems can identify potential overfluxing conditions and implement preventive measures to mitigate risks and ensure safe operation.

Overall, overfluxing protection is critical for preserving the integrity and reliability of transformers, particularly in high-voltage and high-power applications. By detecting and mitigating overfluxing conditions, protective devices and systems help extend the service life of transformers, minimize downtime, and prevent costly damage and failures.