HV Winding Failure in Transformers | Diagnosis and Solutions

 Introduction: 

Transformers play a crucial role in the power grid, facilitating the efficient transmission and distribution of electricity. However, like any other equipment, they are susceptible to faults and failures, which can disrupt power supply and pose safety risks. Among the various types of transformer failures, high-voltage (HV) winding failure stands out due to its potential to cause significant damage and downtime. In this blog post, we delve into the diagnosis of HV winding failure in transformers, exploring the causes, methods of detection, and potential solutions.

Understanding HV Winding Failure: 

HV winding failure refers to the occurrence of faults in the high-voltage winding of a power transformer. These faults can stem from multiple factors, including insulation degradation, over-voltage, transient phenomena, or overloading conditions. The consequences of such faults range from turn-to-turn faults (TTF) to short circuits and winding deformation, jeopardizing the transformer's functionality and reliability.

Diagnosis Methods: 

Detecting HV winding failure requires precise diagnostic methods capable of identifying and locating faults within the winding. Several techniques are employed for this purpose:

Frequency Response Analysis (FRA): 

FRA involves injecting a signal into the HV winding and analyzing its response in the frequency domain. Discrepancies between the measured response and a reference signal indicate abnormalities in the winding structure or parameters, aiding in fault detection and localization.

Impulse Frequency Response Analysis (IFRA): 

IFRA builds upon FRA by utilizing impulse signals instead of continuous signals. By subjecting the HV winding to impulse excitation and analyzing the frequency response, IFRA offers enhanced sensitivity to certain fault types, such as winding deformations.

Lightning Impulse Analysis (LIA): 

LIA focuses on assessing the HV winding's response to lightning impulses, which simulate high-voltage surges. Variations in the response pattern can indicate potential weaknesses or faults in the winding insulation, facilitating preemptive maintenance or repair actions.

Electromagnetic Wave Method: 

This method employs antennas to capture electromagnetic waves reflected from the HV winding. Changes in wave characteristics, such as amplitude and phase, reveal alterations in the winding's impedance or conductivity, signaling the presence of faults.

Utilizing these diagnostic methods, engineers can pinpoint the type and location of HV winding faults, enabling timely interventions to prevent further deterioration and minimize downtime.

Solutions and Mitigation Strategies: 

Once HV winding failure is diagnosed, prompt action is essential to mitigate its consequences and restore transformer reliability. Depending on the severity and nature of the fault, solutions may include:

• Repairs and Rewinding: For localized faults or minor damage, targeted repairs or rewinding of the affected winding sections can rectify the issue without necessitating complete replacement.

• Insulation Enhancement: Enhancing the insulation system through treatments such as reimpregnation or retrofitting with advanced insulating materials can improve the HV winding's resilience to future faults and environmental stresses.

• Monitoring and Maintenance: Implementing robust monitoring systems enables continuous surveillance of transformer health, allowing early detection of potential faults and proactive maintenance measures.

Conclusion:

 HV winding failure in transformers poses a significant challenge to power grid reliability and safety. However, through advanced diagnostic techniques and proactive maintenance strategies, engineers can effectively identify, mitigate, and prevent such failures, ensuring the continued operation of critical electrical infrastructure. By staying vigilant and leveraging technological innovations, the industry can safeguard transformers against the detrimental effects of HV winding faults, bolstering the resilience of the power supply network.