When FRA(Nondestructive testing) is so import in testing Transformers

With the increase in grid capacity and short-circuit current levels, the risk of winding impacts rises.

Especially in scenarios involving new energy grid integration and frequent start-stop operations, transformers are subjected to more electromagnetic shocks.

• A mandatory testing item for power grid companies
• A required test item for high-voltage transformer acceptance
• An important technical means for condition-based maintenance

Winding deformation testers (also known as transformer winding frequency response analyzers, FRA) are mainly used to detect whether mechanical deformation or structural displacement has occurred in the windings of power transformers. It is a preventative testing device widely used in power system equipment condition assessment.

When an external short circuit or inrush current occurs in the system, the huge electrodynamic force may cause the windings to exhibit:

• Axial compression or tension
• Radial bulging
• Inter-turn displacement
• Winding loosening

Even if the transformer can still operate, it may pose a risk of insulation breakdown. In this case, winding deformation testing is necessary.

Large power transformers may be subjected to:

• Vibration
• Tilting
• Impact

Especially for equipment with voltage levels of 500kV and above, winding deformation testing is a standard procedure before commissioning.

When performing:

• Core removal inspection
• Bushing replacement
• Internal repair

After completion, it is necessary to confirm that the winding structure has not changed.

For transformers that have been in operation for more than 10 years, especially those subjected to:

• Heavy load operation
• Multiple fault impacts
• Main transformers in important substations

It is recommended to conduct condition assessment tests and establish historical comparative data.

• Power Plant Main Transformers
• Substation Main Transformers
• GIS Transformers
• Ultra-High Voltage Projects

• Steel Mills, Electrolytic Aluminum Plants, and other enterprises subject to impact loads
• Petrochemical Enterprises
• Large Manufacturing Plants

• Power Testing and Research Institutes
• Equipment Testing Companies
• Operation and Maintenance Service Companies

In short, when a transformer encounters events that could potentially damage its internal components, or at critical junctures in its lifecycle, it needs to undergo a "CT scan" to ensure the health of its core components.