TOA4’s Fluid Quality Index (fqindex)
The S. D. Myers Inc. laboratory reports the ratio of interfacial tension (IFT) and acid number as an indicator of the extent of oxidation of insulating oil. This ratio is the inspiration for TOA4’s Fluid Quality Index, which is calculated with an extra factor of 1000 to ensure that typical values of the index are not tiny decimal fractions. Here is the formula: fqindex = 1000*acidnum/ift Here, acidnum is the acid number (mg KOH/g), and ift is the interfacial tension (mN/m). The fqindex is calculated so that low values are good and high values are bad. Clean new oil has an fqindex below 1.0, and when fqindex reaches 10, the oil is in poor condition. While fqindex is good for trending the approximate oil quality and for detecting sudden changes which may need investigation, the acidity and I ...
TOA4 Online Q&A
What is the difference between kv_ratings and ratedkv in TOA4? The ratedkv field — a “legacy” field inherited from TOA3 — is numeric and designates the rated kV of a piece of equipment, or the highest rated winding kV of a transformer. The kv_ratings field is text and can be used to display multiple winding kV’s, usually separated by slashes; it was introduced in TOA4 as a companion to mva_ratings, which is also text. For analysis purposes, does it matter which of the two fields we use? You can use either, both, or neither, as you like. Other than the fluidtype, equipnum/serialnum, and apprtype, all the equipment information that the analysis needs is implicit in the analysis norms that you assign to the equipment. Over the years we have discovered that the equipment “nameplate” informatio ...
TOA4 In-Service Equipment Filter
Each equipment item has an “In-service” checkbox – visible when editing the item – which should be checked if the equipment is in service and unchecked if the equipment is not in service, i.e., retired or permanently de-activated. In an equipment import or export file, this field is called “in_service” and has a value of 1 (true) or 0 (false). The default value, if no value for in_service is specified when the equipment is imported for the first time, is 1. The “In-service items only” checkbox below the Apparatus Type filter at the top of the equipment list page activates a filter which excludes all equipment items for which in_service is false. This prevents, for example, all the failed equipment from occupying the top of the list when you are sorting by Assessment or Next DGA. The “In-se ...
TOA4 Online Mobile Access
If you are a TOA4 Online user and have a web-enabled cell phone, Blackberry, or PDA, you might like to try out TOA4’s new mobile access feature. Point your phone’s web browser to the TOA4 Online address, but add “/m” at the end of that address. Some cell phone companies aren’t very good with handling “https”, so if your phone complains about the security certificate, try using “http” instead. You still have to log in using the same ID and password that you normally use for TOA4 Online. If you use the mobile access feature, we would appreciate some feedback on how it treats you and what we should do to make it more useful for you. Here are some example pages. The “home” page (not shown) is an abbreviated equipment list, which is always filtered to keep the list short. Items with an abnormal ...
Honey, I deleted all my data!
Early one Monday morning a TOA4 Online user reported, not too cheerfully, having “accidentally” deleted all of the equipment (and therefore all of the test data too) from her company’s TOA4 database. Anything we could do? at all? I could hear her boss’s heavy breathing in the background. Yes, of course, we could fix it, but I had to go find Farmer Neil, our server administrator, who was far out on the land with his dynamite, air compressor, and jackhammer preparing the still-frozen soil for this year’s planting of canola (hey, this is Canada). Pushing the hood of his parka back and mopping his forehead with a large red hankie, Neil just said, “Yep, we’ll get her all fixed up in no time. Have to work my way closer to the farm house, though, because my wireless isn’t too good this far out, e ...
Common TOA4 Import Problems
When you are trying to import test data into your TOA4 Online account, there can be various reasons why either TOA4 refuses to accept the data file or some of the data records don’t get imported. Here are some cases that users have encountered so far: File upload fails 1. Error parsing data file. Usually, this means that you have clicked the wrong thing and tried to upload a spreadsheet (.xls) or word processing (.doc) file. Sometimes it means that the file has been corrupted and contains non-text gibberish. Import operation fails 1. Missing or mis-named required columns. For example, if the apparatus type (apprtype) column is not found, neither equipment nor test data can be imported. Often it turns out that the column is not missing, but its name is spelled wrong. 2. Missing sampledate c ...
Thermodynamic Estimation of Transformer Fault Severity
Authors: F. Jakob and J.J. Dukarm Published in Power Delivery, IEEE Transactions vol.30, no.4, pp.1941-1948, Aug. 2015 doi: 10.1109/TPWRD.2015.2415767 Conventional practice for transformer dissolved gas analysis (DGA) is to use concentrations of several fault gases, with or without total dissolved combustible gas, for evaluating apparent fault severity. We suggest a simpler approach based on the normalized energy intensity (NEI), a quantity related directly to fault energy dissipated within the transformer. DGA fault severity scoring based on NEI is shown to be sensitive to all IEC fault types and to be more responsive to shifts in the relative concentrations of the fault gases than scoring based on fault gas concentrations. Instead of eight or more gas concentration limits, NEI scoring r ...
Remember in TOA4 Online to Analyze New Data
When you import new test data in TOA4, the dialog that appears just after you click “Import test data” contains a checkbox that tells TOA4 to do an analysis immediately upon completing the import. Normally, this checkbox should be left “checked” unless you are importing many thousands of samples at once. Really huge import files should be broken up into smaller ones anyway. If you do import new test data without doing an analysis, an “Analyze new” button should be displayed below the equipment list. Be sure to click that button to calculate analysis results before starting to review UNREVIEWED data. After all new data records have been analyzed, the “Analyze new” button is no longer displayed. Note that if the equipment “owning” the data does not have a correct norm name associated with it ...
Cluster Assessment for Online DGA Monitoring
Author James J. Dukarm 2015 CIGRE Canada Conference This paper describes a cluster assessment (CA) method for automatic detection, assessment, and logging of significant fault gas production events by enalysis of multi-gas online monitor data. When large numbers of transformers are monitored, automatic screening interpretation of the data is necessary. The automated interpretation of dissolved gas data must be quite skilled at discriminating between exceptional and unexceptional patterns to provide high sensitivity and high specificity, i.e., to detect incipient problems reliably while generating very few false alarms. The CA method is applied to a moving time window of the most recent 30 to 90 days of multi-gas monitor data for each transformer. It relies upon three innovative elements: P ...
A Thermodynamic Approach to Evaluation of the Severity of Transformer Faults
Authors: F. Jakob, P. Noble, J.J. Dukarm, J.J Published in Power Delivery, IEEE Transactions on vol.27, no.2, pp.554-559, April 2012 doi: 10.1109/TPWRD.2011.2175950 Abstract: Dissolved gas analysis (DGA) has been used to classify the type and severity of faults in transformers. The method commonly used to identify severity is to measure the total fault gas concentration and its rate of change, without regard to the relative concentrations of individual gases. Thermodynamic analysis indicates that the energy required to form gases increases in the order CH4 <; C2H6 ≤ CO ≤ C2H4 <; H2 ≪ C2H2. Based on these results, an energy-weighted dissolved gas analysis (EWDGA) is proposed, where concentrations of individual gases are multiplied by a weighting factor that is proportional to the ener ...