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Hot Oil Cleaning

Whenever there is excessive oxidation of the oil and aging of the paper insulation, the service recommended most often is hot oil cleaning. This valuable process involves the use of a mobile oil processing unit (a.k.a. vacuum oil processor or “VOP”) or oil reclamation “rig,” with the use of filtering clay such as Fuller’s Earth. The oil is reclaimed in the VOP through heating and vacuuming and sub-micronic filtration, and then returned to the equipment that is being cleaned.

Oxidation Inhibitor and Reinhibiting Oil-Filled Transformers

Most mineral oil dielectric fluids contain an added oxidation inhibitor which is a chemical additive that acts as a preservative. The purpose of the inhibitor is to prevent oxygen from reacting with the oil, thus slowing the aging rate of the oil (and also of the solid insulation). The two most common oxidation inhibitors used in transformer oils are 2,6-ditertiarybutyl para-cresol (DBPC) and 2,6-ditertiary-butyl phenol (DBP).

What is the AGE Test and when should it be performed? - Part 1

As perchloroethylene fluid ages in service, it breaks down and forms hydrochloric acid. The AGE additive acts to neutralize this acid, so that the acid does not react with the metals in the transformers.

AGE Testing - Part 2

After the AGE test, the amount of acid remaining is measured, giving an indication of concentration of AGE in the sample. The result is compared to three calibration standards that are also run with the same procedure: a clank, a 1000 ppm AGE standard, and a 2000 ppm AGE standard. The response of the sample is compared with the response of the three standards to determine the concentration of AGE in the sample.

Dielectric Breakdown Voltage Testing - Part 1, Standard Methods

What causes bad D1816 dielectric breakdown voltage values? The first article in this series will discuss the three standard methods that SDMyers is equipped to perform, and why we perform them for our customers. There are two standard methods from ASTM International: D877, Standard Test Method for Dielectric Breakdown Voltage of Insulating Liquids Using Disk Electrodes, and D1816, Standard Test Method for Dielectric Breakdown Voltage of Insulating Oils of Petroleum Origin Using VDE Electrodes. 

Understanding Your Test Results

One of the most important functions of oil in a transformer is to protect the paper (solid insulation).  As oil ages, it loses its ability to protect the paper from degradation.  Aging also weakens the oil’s ability to act as a cooling medium and provide dielectric strength – ultimately protecting the transformer from failure.  Through the aging process, chemical by-products build up in the oil and the paper, creating acid by-products and sludge. These decay products begin to affect the oil’s protective qualities almost immediately after they form, they begin to break down the molecular structure of the solid insulation.

Sampling - Part 1

Oil testing can diagnose unseen problems inside a transformer. Mineral oil comes in contact with the internal workings of the transformer and contains valuable information regarding the condition of the transformer. Information about the equipment and a properly drawn sample are critical for making a correct diagnosis of the transformer's health.

7 Challenges to Overcome in Developing Electrical System Reliability

There are very few organizations that are not concerned with following reliability best practices. It is more efficient and less expensive to prevent a breakdown than it is to fix something that breaks. Monitoring and data management are becoming ubiquitous in the industrial world, the utility world, and across most industries and sectors as we work towards a more reliable and interconnected future. Electric power systems have not been included in this shift away from break/fix and towards data-centric reliability, and what the future holds for organizations seeking best practices.

Moisture in Transformers - Part 2

Moisture may exist in a transformer in several forms. 1. Water vapor in the gas space of the transformer. 2. Water dissolved in the oil. 3. Free water suspended as droplets in the oil. 4. Emulsified water contained in the decay products of oil oxidation. 5. Water absorbed into and adsorbed onto the solid insulation. 6. Free water that has settled to the bottom of the transformer. Paper has more affinity for moisture than oil does. Once wet, moisture removal is the corrective action that should follow. However, before moisture removal, it is important to first evaluate how the transformer became wet. 

Liquid Power Factor - Part 2

The values we obtain from liquid power tests indicate certain conditions in a transformer, allowing us to determine which condition, moisture, oil oxidation, or contamination, is causing the result. The values we use to classify liquid power factor results for in-service oil are the same for all primary voltage classes of equipment.
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