Technical library

For approximately 25 years, dielectric frequency response (DFR) has been investigated and proven to provide an accurate method of determining both the moisture condition of paper + oil power transformers and bushings. Together with general insulation testing, DFR provides enhanced insulation condition of the transformer under test.DFR testing method is now accepted internationally – as evidenced by its inclusion in the CIGRE TB445 as an accepted method for moisture determination. IEEE is presently in the process of completing a new guide for use of DFR in transformer moisture assessment for both factory and field testing, which should be completed and available by 2019. Instruments like the Megger IDAX300, which was the first commercially available unit to perform this test, is a valuable tool in this determination of moisture content.IDAX300 has included the ability to perform PF tests at frequencies from 1 to 500Hz which can be defined as a narrow frequency band dielectric frequency response test. We are now able to provide a shorter duration DFR test which gives us additional information into the overall insulation condition of the transformer or bushing.This paper illustrated a narrow band DFR test performed on a transformer located in Thailand – EGAT (power utility) and the result was recorded. It is proved that narrow band DFR test can provide a base line for any future testing comparison. We can use both a curve shape and/or a trend change for looking for issues. We no longer need to only rely on the line frequency PF(DF) to detect future issues.

Software update for 'A' models

PD Detector Software for MV DAC30, TDS NT, TDM 45, PDS 62

Total Harmonic Distortion (THD) is a common method used to measure the level of waveform distortion.Total Harmonic Distortion (THD) measurements are an effective method of evaluating voltage distortion. However THD can be misleading when evaluating current distortion. THD is the summation of the harmonics presented as a percentage of the fundamental. For voltage THD this will be the summation of the voltage harmonics compared to the fundamental voltage. In a non-faulted condition voltage will always be present so a proper reference always exists.

Adding, removing or changing a piece of equipment in a facility can have significant impacts on the power quality and energy requirements. Introduced power quality phenomenon can cause equipment to trip off line. This can represent significant losses in revenue. Added equipment can create high peak loads or increased reactive currents that can lead to penalties. In order to determine the impact of these changes a power quality and demand study should be performed prior to the change and after the change.

When creating a setup file a particular power wiring connection needs to be selected. This instructs the instrument on how to calculate the power and energy. When the power wiring connection is create the required input channels are automatically enabled.In some cases the operator may wish to enable additional channels for other measurements. This will not affect the power or energy measurements.

Technological advances in on-line testing of motors, diagnostics and motor monitoring have increased substantially over the past few years. Voltage and current signature analyses have improved the quality of predictive maintenance (PdM) compared to what RMS current and voltage measurements or power-factor readings have been able to achieve.

Surveyor DX software

Lithium ion batteries consist of a family of batteries. They have different chemistries and characteristics to suit different applications.

Each issue of Electrical Tester has a range of hand-picked industry articles for high-voltage electrical engineers working on utilities.