Click Here for Official ABB Response on This Matter

Click here for official ABB response on this matter

ABB Stained Bushings Frequently Asked Questions

· What are the dates of manufacture that we should be concerned with?

· Do all the bushings in this time frame display this problem?

· What is the voltage range we should be concerned with?

· Do all bushings in this time frame display this problem?

· What is the voltage range we should be concerned with?

· What is the stain composed of?

· Will the composition of the stain harm the oil in the oil insulated equipment?

· How long after these bushings are installed will they begin to stain?

· When the stain is wiped, will it come back?

· After the bushing is wiped, how long before I have to wipe it again?

· Is there a concern with your current production gaskets

· How much stain does it take before I should be concerned?

· You mention above to look for an "abnormally low" power factor and then perform "further inspection". Please elaborate.

· What is the mode of failure?

· Have there been any bushing failures associated with this type of phenomenon?

· We have bushings in our storeroom that are exhibiting some type of staining at the gasket area. Are these of concern?

· If we find any bushings in service which have a substantial amount of staining on the lower porcelain, what information would ABB Alamo like to have?

· If I have additional questions who can I contact?

What are the dates of manufacture that we should be concerned with?

Confirmed occurrences to date confine this to the 1990 to 1994 time frame.

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Do all bushings in this time frame display this problem ?

No, based on the reports received to date, we do not believe this is a widespread phenomenon.

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What is the voltage range we should be concerned with?

Field reports indicate it is confined to the bushings rated up to and including 115 kV.

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What is the stain composed of?

The stain is composed of chemical additives used in nitrile rubber gaskets to make them more pliable. These chemical additives are non-conductive.

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Will the composition of the stain harm the oil in the oil insulated equipment ?

The additive described above will not cause any degradation of the oil insulated equipment's oil.

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How long after these bushings are installed will they begin to stain?

Staining is a function of time, heat, and compression of the gasket material. At this point in our investigation, we have been unable to determine when the staining will begin.

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When the stain is wiped, will it come back?

In all probability, with the conditions outlined above, the staining may redevelop. However, at some point in time, the leeching of the chemical additives' resins will cease.

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After the bushing is wiped, how long before I have to wipe it again?

Under conditions outlined in above question, it may take several years for the staining to appear again.

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Is there a concern with your current production gaskets?

All testing to date indicates that ABB does not have an issue with our current production gaskets.

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How much stain does it take before I should be concerned?

We recommend that you power factor test the bushings in service, looking for abnormally low or negative power factor readings. If observed, this should indicate the need for further inspection. Remember, per our advisory, the upper porcelain must be thoroughly cleaned before taking a power factor reading.

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You mention above to look for an "abnormally low" power factor and then perform "further inspection". Please elaborate.

Decrease in power factor, as compared to nameplate values, which are 0.05 or greater should be investigated:

* Clean the upper porcelain and capacitance tap thoroughly and repeat the test. If the change measured is less than 0.05, continue to monitor the bushing during the annual maintenance procedures.

* If the change is still greater than or equal to 0.05, compare to initial PF measurements made after the bushings was installed.

* If the change in PF from the initial installed value to the present measurement is less than0.05, continue to monitor the bushing during the annual maintenance procedures.

* If the change in PF from the initial installed value to the current measurement is equal or greater than 0.05, the bushing should be removed from the tank and inspected.

* If contamination is observed on the lower porcelain, record the condition of the porcelain by photographs or other media and forward to Mike Junkin (address below).

* The lower porcelain should be cleaned thoroughly with isopropyl alcohol to remove all visible contamination, and then retest the bushing.

* If the change in power factor from the nameplate is less than 0.05 then the bushing can be re-installed.

* Perform follow-up PF and Capacitance tests after re-installation of the bushing.

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What is the mode of failure?

The gasket additives in themselves will not cause a flash over, however if sufficient metallic or conductive particles are present in the oil, the particles will adhere to the stain and may eventually cause a flash over.

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Have there been any bushing failures associated with this type of phenomenon?

We have field reports of two bushing flash overs that had stains on the lower porcelain.

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We have bushings in our store room that are exhibiting some type of staining at the gasket area. Are these of concern?

The staining you are witnessing is a different composition than what is being described here. We do, however, suggest that for cosmetic reasons the stain be cleaned off.

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If we find any bushings in service which have a substantial amount of staining on the lower porcelain, what information would ABB Alamo like to have?

In order to gather "data points' to assist us in our on-going investigation, we would appreciate you sending us the following information:

Digital pictures of the staining

Bushing style and serial numbers

Copy of transformer nameplate

If possible, two quarts of oil from each transformer

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If I have additional questions who can I contact?

Contact our Customer Service Department in Alamo, TN at 1-(800)-955-8399 or email us with any questions or comments.