Taking Care of Transformers, Part 9

Dec. 20, 2012
If you have power factor correction capacitors, should you skip insulation power factor testing on your transformers? The answer is "no." Those PF capacitors have no bearing on the question. This is a test of the transformer insulation. When you subject a perfect insulator to an AC voltage stress, it doesn't pass resistive current. But insulators deteriorate over time. As the insulation integrity decreases, the resistive component of the current increases — and so does the power factor.

If you have power factor correction capacitors, should you skip insulation power factor testing on your transformers? The answer is "no." Those PF capacitors have no bearing on the question. This is a test of the transformer insulation.

When you subject a perfect insulator to an AC voltage stress, it doesn't pass resistive current. But insulators deteriorate over time. As the insulation integrity decreases, the resistive component of the current increases — and so does the power factor.

Insulation power factor is the ratio of the resistive current component to the total leakage current under an applied voltage stress. In addition to the resistive component, there's also a capacitive component.

If you don't normally have this test done, ensure it's performed if the transformer has survived a major power event.

Voice your opinion!

To join the conversation, and become an exclusive member of EC&M, create an account today!

Sponsored Recommendations

Electrical Conduit Comparison Chart

CHAMPION FIBERGLASS electrical conduit is a lightweight, durable option that provides lasting savings when compared to other materials. Compare electrical conduit types including...

Fiberglass Electrical Conduit Chemical Resistance Chart

This information is provided solely as a guide since it is impossible to anticipate all individual site conditions. For specific applications which are not covered in this guide...

Considerations for Direct Burial Conduit

Installation type plays a key role in the type of conduit selected for electrical systems in industrial construction projects. Above ground, below ground, direct buried, encased...

How to Calculate Labor Costs

Most important to accurately estimating labor costs is knowing the approximate hours required for project completion. Learn how to calculate electrical labor cost.