PD measurement is a worldwide-accepted method for insulation diagnosis and a required part of the acceptance testing for many HV assets. To facilitate PD measurements different techniques/methods have been developed and they are in use for laboratory and on-site applications. All these methods can be divided into conventional and unconventional PD measuring methods. The latter are the subject of this guide.@en

This investigation aims to perform a probabilistic prediction of the lifetime of epoxy resin insulation of transformer windings. To support the prediction, several accelerated electrical aging tests were conducted at different voltage levels on epoxy resin insulated transformer winding specimens. The lifetimes achieved from the tests show a ¿flat z-shaped¿ V-t (voltage vs. lifetime) curve and indicate the well known threshold stress effect. Since the operation stress is in the convex part of the V-t curve, the life exponent n was not predetermined, but estimated from a data pool obtained at the lowest voltage levels. As a result, the operation life and its confidence intervals were predicted from the breakdown data at these low voltage levels.@en

The abstraction of meaningful diagnostic information from raw condition monitoring data in domains where diagnostic expertise and knowledge is limited and constantly evolving presents a significant research challenge. Expert diagnosis and location of partial discharges in high voltage electrical plant is one such domain. This paper describes the functionality of a knowledge-based decision support system capable of providing engineers with a comprehensive diagnosis of the defects responsible for partial discharge activity detected in oil-filled power transformers. Plant data captured from partial discharge (PD) sensors can be processed to generate phase-resolved partial discharge (PRPD) patterns. This paper proposes a means of abstracting the salient features characterizing the observed PRPD patterns. Captured knowledge describing the visual interpretation of these patterns can be applied for defect diagnosis and location. The knowledge-based PRPD pattern interpretation system can support on-line plant condition assessment and defect diagnosis by presenting a comprehensive diagnosis of PD activity detected and classification of the defect source. The paper also discusses how the system justifies its diagnosis of the PD activity to offer the expert greater confidence in the result, a feature generally absent in 'black-box' pattern recognition techniques. The incremental approach exhibited by the system reflects that of a PD expert's visual interpretation of the PRPD pattern. The paper describes how this functional system design has evolved from the approach taken by PD experts to the visual interpretation of PRPD patterns.@en

Since the early nineties, ultra-high-frequency (UHF) partial discharge (PD) measurements are being applied to SF6 gas-insulated equipment. Over the years, PD measurements revealed the presence of some insulation defects in the 380 kV GIS. The measuring results have been compared to laboratory experiments. Moreover, locating was possible as well. Cigre TF D1.03.09 has been working on a risk-assessment procedure to assess the risk for a failure for insulation defects, based on PD measurements. So this procedure is only applicable to insulation defects that give detectable PD activity. The paper will show examples of the application of this risk assessment method on the different detected PD sources. Finally the actions initiated by the DSO/TSO for these analyzed insulation defects will be described.@en