SD Myers, Inc. - Tech Corner

Hot Oil Cleaning and Life Extension

Fri, 19 Feb 2010 16:03:36 -0500

In last week’s article, we introduced hot oil cleaning. In this week’s article, we will carry this discussion further by relating how this maintenance activity extends the life of a transformer that has been hot oil cleaned.

Hot Oil Cleaning

Fri, 22 Jan 2010 12:00:42 -0500

When oil maintenance is needed to arrest oxidation of the oil and aging of the solid insulation, the service recommendation is most often for hot oil cleaning. Hot oil cleaning involves the use of a mobile oil reclaiming rig to process the oil in electrical equipment…

Routine and Non-routine Sampling Intervals

Fri, 01 Jan 2010 12:00:06 -0500

We are going to dip into the mailbag for this week’s Tech Corner article. A correspondent asked a question that we have also fielded recently at a number of seminars. “When is it necessary to sample and test the oil in my transformers more often than once a year?” ...

Dielectric Breakdown Voltage Testing – IEC 60156 for New and In-service Mineral Insulating Oil

Wed, 30 Dec 2009 12:00:03 -0500

Over the past several weeks, we have been discussing testing insulating oils for dielectric breakdown voltage. Aside from a brief description of the IEC method, we have so far provided information on just the two ASTM standard methods, D877 and D1816. In the final installment regarding this topic, we are going to discuss the IEC method from Standard 60156, including values used in IEC standards for unused and in-service mineral oil...

Dielectric Breakdown Voltage Testing – ASTM D1816 for New Insulating Liquids

Fri, 18 Dec 2009 12:00:30 -0500

In previous weeks, we had been discussing testing insulating oils for dielectric breakdown voltage using ASTM standard methods D877 and D1816. In the last edition of Tech Corner, we discussed what we do when we have bad D1816 data for in-service transformer oil. This week, we are going to discuss using the same test, D1816 dielectric breakdown voltage using VDE electrodes, to evaluate new oil…

Dielectric Breakdown Voltage Testing – ASTM D1816 for In-service Insulating Liquids - What We Do With a Failed Test

Fri, 06 Nov 2009 12:00:21 -0500

When we evaluate D1816 results that are outside the acceptable range, the first consideration is to cross reference the results to moisture, liquid power factor, and liquid screen tests to identify possible causes for the depressed D1816 values…

Dielectric Breakdown Voltage Testing – ASTM D1816 for In-service Insulating Liquids – The Fundamentals

Fri, 30 Oct 2009 12:00:30 -0400

For in-service insulating liquids, D1816 values are expected to fall within acceptable ranges listed below. These AC ranges are the same as though contained in the IEEE standard. These values are indicated for both gaps settings and for the three voltage classes indicated by the standard…

Dielectric Breakdown Voltage Testing – ASTM D1816 for In-service Insulating Liquids - The History

Fri, 23 Oct 2009 12:00:54 -0400

This week, we are going to start looking at the three standard methods for dielectric breakdown voltage. We will be examining the applications for each method, conditions that cause results of each method to change, and the limitations of each method...

Dielectric Breakdown Voltage Testing – ASTM D877

Fri, 16 Oct 2009 12:00:51 -0400

Dielectric Breakdown Voltage Testing – Standard Methods

Fri, 09 Oct 2009 12:00:27 -0400

As we were sitting down to write this week’s Tech Corner article, we received an email from a reader asking that we write a column on what causes bad D1816 dielectric breakdown voltage values. We shifted gears and are starting a series that will include the column that our reader requested. Keep those ideas coming! This week’s article, the first in this series, will discuss the three standard methods that we are equipped to perform and why we perform them for our customers...

Testing Insulating Liquids Using Particles Analysis – The Last Chapter (For Now, Anyway)

Fri, 25 Sep 2009 12:00:50 -0400

For the past few weeks, we have discussed particles and filming compounds analysis. This week, we will talk about some standards activities concerning these analyses and a couple of real life cases that were unusual applications for particles and filming compounds analysis...

Testing Insulating Liquids Using Particles Analysis – Other Equipment Types

Fri, 18 Sep 2009 12:00:45 -0400

For the past few weeks, we have discussed particles and filming compounds analysis, incorporating both particle count distribution analysis and analytical ferrography, applying the discussion mainly to insulating liquids from load tap changers. This week, we are going to discuss applying these analyses to other equipment types and insulating oil applications. We will start by discussing particle count distribution analysis for in-service oil-filled circuit breakers, switches, and transformers...

Testing Insulating Liquids in Load Tap Changers – Analytical Ferrography

Fri, 11 Sep 2009 12:00:53 -0400

Last week, we discussed particle count analysis, one of the two tests that collectively are designated as particles and filming compounds analysis. This week, we are going to discuss the other analysis, which is analytical ferrography. The purpose of analytical ferrography is to determine not only how many particles in the various size ranges are present, but also what those particles are made of and what conditions may have caused them to be formed. Analytical ferrography has been used for years to test evaluate lubricating oils while looking for wear particles. The same techniques also provide valuable information when applied to insulating liquids, and especially to insulating oil from load tap changers...

Testing Insulating Liquids in Load Tap Changers – Particle Count Distribution

Fri, 28 Aug 2009 12:00:09 -0400

Last week, we discussed some of the tests that are routinely performed on insulating liquid from load tap changers – liquid screen, moisture content, and dissolved gas analysis. Routine testing for the particles found in the oil also provides critically important information. Particles and filming compounds analysis includes two separate analyses – particle count distribution and analytical ferrography. This week, we are going to talk specifically about particle count distribution for load tap changer insulating liquid samples...

Testing Insulating Liquids in Load Tap Changers – Liquid screen tests, moisture content, and dissolved gas analysis

Fri, 21 Aug 2009 12:00:20 -0400

Last week, we talked about how conditions inside a load tap changer may cause accelerated filming as the oil ages. Previously, we discussed the negative effects that filming has on the efficient operation of the device, and how filming may create a need for a shorter maintenance interval. This week, we are going to talk about some of the tests that we use to monitor that process. Specifically, we are going to look at the liquid screen, moisture content analysis, and dissolved gas analysis...

Testing Insulating Liquids in Load Tap Changers – What causes accelerated filming in an LTC?

Fri, 14 Aug 2009 12:00:20 -0400

Last week, we talked about how mineral insulating oil ages in the LTC. As oil ages in a load tap changer, it polymerizes and forms a resinous, varnish-like film over the contacts and mechanism. This week, we are going to talk about conditions that cause that filming to proceed faster. It is very important to understand these conditions since accelerated filming may lead to potentially destructive conditions prior to the end of the normal preventative maintenance interval. If filming is well advanced, arcing may be sustained too long on the contact causing overheating and premature wear. In extreme cases, this may lead to failure. Similarly, filming of the mechanism will cause the device to work harder during normal changing of the taps under load. These conditions can cause an increase in operating temperature of the device. More importantly, in extreme cases, filming can become so advanced that it may lead to binding and subsequent mechanical failure of the LTC...

Testing Insulating Liquids in Load Tap Changers – How does oil age in an LTC?

Fri, 07 Aug 2009 12:00:22 -0400

Testing the oil in load tap changers provides valuable information concerning the operation of the unit. Monitoring conditions between preventative maintenance inspections is a critical step in preventing expensive maintenance problems and even unplanned outages. In this first article, we are going to talk about how mineral insulating oil ages in the LTC. This aging mechanism is considerably different from that of oil in other types of electrical equipment. Understanding the aging process indicates some of the challenges of maintaining LTCs, but it also presents some opportunities for improving the effectiveness of the overall maintenance program...

Will Changing Oil Solve an Acid Problem?

Fri, 24 Jul 2009 12:00:29 -0400

This week, we are going to answer another question that we received for this Tech Corner feature. It is a question we have been asked many times, phrased different ways. A customer asked one of our MaxLife Consultants about his test results. “I have a high acid number for one of my units, and your recap lists a recommendation that I have the transformer hot oil cleaned. Can I just change the oil to lower the acid number to an acceptable level?”...

Testing for Liquid Power Factor in Mineral Insulating Oil – Applications

Fri, 17 Jul 2009 12:00:42 -0400

For the past two weeks, we have introduced liquid power factor testing and discussed acceptable, questionable, and unacceptable values for in-service transformer oil. This week, we want to look at when we recommend running the test. We will also discuss acceptable values for new oil from a supplier and for newly installed oil in transformers...

Testing for Liquid Power Factor in Mineral Insulating Oil – Acceptable, Questionable, and Unacceptable Values

Fri, 10 Jul 2009 12:00:09 -0400

In last week’s article, we introduced testing of the liquid power factor of insulating liquids as a tool for evaluating oil-filled transformers. This week, we are going to discuss the values we obtain from liquid power factor tests and what these values indicate. We are going to introduce typical and specification values for new, unused oil and newly installed oil in transformers, as well as acceptable, questionable, and unacceptable values for In-service oil...

Testing for Liquid Power Factor in Mineral Insulating Oil – Introduction

Fri, 03 Jul 2009 12:00:01 -0400

Liquid power factor is an outstanding tool for evaluating in-service transformer oil. The test is valuable for acceptance testing of new oil from a supplier, and for evaluating conditions in newly installed equipment. For in-service oil, there are several adverse conditions that show up as changes in the liquid power factor results...

Testing for Furanic Compounds in Insulating Liquids – One final topic, for now, anyway

Fri, 26 Jun 2009 12:00:40 -0400

Over the past few weeks, we have discussed testing for furanic compounds. Key points we covered were why furan analysis gives us information on the condition of the solid insulation, when we recommend running the test, the significant values, and how we use the results to estimate the condition of the insulation. Along the way, we received an interesting question that we would like to answer. We have heard variations of this question a number of times at our seminars and in phone conversations, and we even have answered it on-line previously...

Testing for Furanic Compounds in Insulating Liquids – Estimating Degree of Polymerization

Fri, 19 Jun 2009 12:00:05 -0400

Last week, we talked about the significant values for furan results. In addition to defining AC, QU, and UN levels, we talked about very high levels that may indicate substantial damage to the insulating system. This week, we are going to talk about calculations that we perform to estimate the condition of the solid insulation using the furans analysis results. We use a two-step approach to estimate a DP and calculate insulation life remaining...

Testing for Furanic Compounds in Insulating Liquids – Significant values

Fri, 12 Jun 2009 12:00:44 -0400

Previously, we have discussed how furan analysis may be used to determine whether the solid insulation in a transformer has broken down and whether the condition that caused that degradation continues to be active. This week we will talk about what levels of furans we consider to be significant. As you may expect, the significance of the results will depend at least in part on the reason for testing the unit in the first place. Let’s talk first about the most obvious time when testing for furanic compounds may be recommended. As we described in our article a couple weeks ago, that is when you suspect that there may be a problem where furan testing can help you confirm that the solid insulation is breaking down...

Testing for Furanic Compounds in Insulating Liquids – When do we test for furans? (Part 2)

Fri, 05 Jun 2009 12:00:31 -0400

Last week, we talked about three times where it makes good sense to test insulating liquids for furanic compounds. These were the “non-routine” occasions where testing for furans is a good idea. There are also a couple of situations where performing the analysis on insulating liquid during every routine sampling and testing interval is appropriate. We are going to describe those situations next...

Testing for Furanic Compounds in Insulating Liquids – When do we test for furans? (Part 1)

Fri, 29 May 2009 12:00:26 -0400

For the last two weeks, we talked about some of the basics concerning testing for furanic compounds and interpreting the results. Next we are going to look when we recommended this testing. While knowing the state of the solid insulation is critical information for any transformer, it may not be the best use of resources to always run furans as a routine test. So let’s talk about when it is most important to analyze the insulating liquid for furanic compounds...

Testing for Furanic Compounds in Insulating Liquids – How do you know if the paper is breaking down?

Fri, 22 May 2009 12:00:11 -0400

Last week, we talked about the basic mechanism of how furanic compounds form in transformers as the solid insulation breaks down. Next we are going to look at the furanic compounds we test for. Interpreting the results can tell us whether the paper has broken down and, maybe even more importantly, whether it still is. We test for five different furanic compounds. Increases in the concentrations of these compounds indicate that the paper is breaking down. Further, the particular furanic compound(s) present provide some useful information on what conditions caused the paper to break down, and may even indicate whether those conditions are still present...

Testing for Furanic Compounds in Insulating Liquids

Fri, 15 May 2009 12:00:02 -0400

How can you evaluate whether the solid insulation in your transformer is breaking down? Well, you could take the unit offline and go through the long involved process of obtaining a sample of the paper for testing. On the other hand, you can analyze an insulating liquid sample for furanic compounds. You can do that without even de-energizing the transformer, and the information you can obtain from furan data is extremely important...

Dissolved Gas Analysis (DGA) for Transformer Warranty – Ten-Month Full-Oil Test

Fri, 08 May 2009 12:00:21 -0400

Last week, we talked about the importance of properly testing a newly installed transformer. Particularly, we discussed the need to take and analyze DGA samples according to a recommended schedule during at least the first month of service. It is equally important to perform the first routine, in-service monitoring and diagnostic tests according to a recommended interval. We refer to that as the “Ten-Month Full-Oil Test”. The timing is important, as some defects may provide initial symptoms during this period without causing revealing more obvious indication until after the warranty period has expired. The timing of the first interval at ten months, and running the complete recommended package of tests, will serve to establish a diagnostic baseline. In addition, the results, particularly abnormal DGA results, may be used to start a dialog with the manufacturer if problems or defects are suspected...

Dissolved Gas Analysis (DGA) – The importance of DGA for new installations

Fri, 01 May 2009 12:00:41 -0400

If a newly installed and energized transformer survives the first ten cycles, then the first ten seconds, then the first ten minutes, chances are pretty good that it will also survive the first ten years. However, manufacturers offer a warranty period for a reason. New transformers may have defects that can lead to failure. Frequently, such defects will leave their signature of dissolved gases in the oil. A timely DGA may catch the fault as it begins, before it advances far enough to do permanent damage...