Sensitive Online PD-Measurements of Onsite Oil/Paper-Insulated Devices by Means of Optimized Acoustic Emission Techniques (AET)

Abstract

Recently developed monitoring-systems show the need as also the possibilities for online-and offline-onsite-diagnostics. The limit in sensitivity for electrical pd-measurements according to IEC 60270 which is reached using filters for sinusoidal disturbances and compensation for corona impulses is still not satisfactory. The acoustic partial discharge measurement (pd-measurement) is also a well known and reliable method often used by transformer manufacturers in testing. In laboratory setups a gain in sensitivity of the acoustic in comparison to the electrical pd measurements could be established. This is reached by adapting the sensors to the propagation path, a modern but moderately priced acquisition hardware and the introduction of new signal processing algorithms. The developed sophisticated measuring systems show remarkable results in online acoustic pd-measurements onsite.

Solving a Set of Spherical Equations for Localization of Partial Discharges by Acoustic Emission Method

“…On the basis of unknowns from (14), (15) the matrix (16) was written and its determinant (17) and matrix (18) are determined from Eqs. (14) and (15):…”

Artificial recognition system for defective types of transformers by acoustic emission

“…Therefore, an ideal way to judge the performance of transformer online is based on computer-aided AE method for PD detection. The following are three highlights of AE methods in PD detection for transformer (Boczar & Zmarzly, 2004;Chen, Tsao, & Lin, 2005;Grossmann & Feser, 2005;Gupta & Ramu, 2001;Lundgaard, 2001).…”

Diagnosis of Power Transformer Insulation

“…Acoustic methods are a further possibility to detect partial discharges and with a number of sensors a localisation is possible under certain conditions possible. The advantage is the suppression of the electrical disturbances but the disadvantages are that the method can not be calibrated and the results can therefore not be compared to former measurements of the apparent charge and that partial discharge signals generated on the core side of the winding may hardly recognised by the acoustic sensors due to the strong absorption of the signal [14] Within the last years ultra high frequency measurements (UHF) comes up, originally used for partial discharge measurements in gas-insulated substations [15]. This method records signals in the range of some 100 MHz up to some GHz where the amplitude of the noise signals could be very low.…”