Practical experience of insulation condition evaluation in an on-site HV installation applying a PD measuring procedure

Analysis of the types of defects and the degradation modes in different insulation materials of high-voltage (HV) electrical systems has shown that the presence of partial discharges (PD) is a very common characteristic in all of them. Once PD activity is detected, the identification and localization of the associated type of defect is very important to evaluate whether the discharges are harmful or not. During the last two decades, different approaches have been developed and applied to PD measurement and processing techniques to deal with the most common problems arising in on-site and on-line measurements, such as: high levels of background noise, appearance of interferences, simultaneous presence of different PD sources and the difficulty of locating the site of the defects and to identify them. This paper proposes a measuring method together with the implementation of three signal processing tools in order to overcome all these difficulties that appear in on-site and on-line tests. The measuring method has been implemented to evaluate in an on-site practical experience the insulation condition of the power equipment in a GIS substation. After the application of the method, important insulation defects were detected, identified and localized, on time to avoid uncontrolled failures in the electrical system of the substation under test.