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DLRO2: long test lead test mode
When measuring very low resistance the four-wire test method has for many years been the standard method. The main advantage being that it simply and easily removes the resistance of the test leads from the measurement. However, what happens when those test leads need to be verylong?
Published: 27 July 2020
DLRO2: new difference meter
Introducing the first low resistance ohmmeter to feature a difference meter, a device that turns changes in resistance into a moving pointer and percentage change. When testing multiple similar connections, it makes it easy to spot those small increases in resistance that eventually turn into major faults.
Published: 27 July 2020
Transformer winding resistance measurement: field challenges
Megger’s article “Transformer Winding Resistance Measurement: Field Challenges” was presented at the 2020 NETA PowerTest Conference in Chicago, Il. This article takes an in-depth look at the lesser known facts associated with the DC winding resistance (WR) measurements, diving deeper into topics such as selection of the correct test current, and the importance of compliance voltage during the test. Phenomena as core saturation, current stabilization, the influence of winding inductance on readings, and the effect of temperature, are also explained.
Published: 12 June 2020
Introduction to thermal imaging
While spot infrared thermometers present only a single temperature at a single spot, Thermal Imaging Cameras give you the whole picture. Thermal imaging is the most effective method for finding problems or potential problems in a variety of applications across many fields.Thermal imagers allow users to measure temperature in applications where conventional sensors cannot be employed. Specifically, in cases dealing with moving objects (i.e., rollers, moving machinery, or a conveyor belt), or where non-contact measurements are required because of contamination or hazardous reasons (such as high voltage), where distances are too great, or where the temperatures to be measured are too high for thermocouples or other contact sensors. The thermal imagers provide an image, which shows the temperature difference of the object being measured. Hot spots can be seen immediately versus traditional infrared guns, which average the area being measured.
Published: 10 June 2020
Software download files for SVERKER900
Published: 4 June 2020
Transformer turns ratio test: some unknown facts
Transformer Turns Ratio (TTR) is one of the most common test used to assess the condition of the transformer’s windings and core. It is performed as a part of acceptance and maintenance test procedure to determine any problems due to poor design, assembly, handling, overloading, fault conditions or poor maintenance. TTR results are compared against the nameplate ratings to determine any possible insulation deterioration, shorted turns, core heating or any other winding or core abnormalities.TTR is a simple and easy test to perform that is often taken for granted without fully understanding the principle and basis of the test. In cases when measurements are not within expected limits, it becomes a challenging task to determine the root cause and resolve the problem. This paper will focus on some of the unknown facts associated with the TTR test. The paper covers in detail the effect of applied test voltage, comparative analysis of step up vs step down excitation, different vector configurations, differences between nameplate ratio, voltage ratio and turns ratio, sources of ratio and phase angle errors, comparison of per phase testing vs true three phase testing, extreme tap ratios being out of tolerance for On Load Tap Changers (OLTC), and TTR test correlation with other electrical tests. The paper also provides field test results and case examples to explain the above-mentioned unknown facts.
Published: 28 April 2020
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