Edward Gulski

On-site testing and diagnosis of transmission power cables up to 230 kV using damped AC voltages

This article presents an overview of on-site testing and diagnosis of new and service-aged transmission HV power cables up to 230 kV using damped AC voltages.

New developments in on-site testing of long lengths of (E)HV power cable

This contribution presents new developments in the field of on-site (E)HV cable testing, in particular testing of long lengths of power cable. A modern solution is presented for on-site testing and diagnosis of transmission power cables by means of sinusoidal damped AC voltages. With this testing technique on-site voltage testing is performed with additional non-destructive measuring techniques e.g. partial discharges or dissipation factor measurements. To improve the PD detection and particularly the PD location possibilities on long cable lengths an additional range extension measurement system has been developed for PD detection on longer cable lengths. This distributed measurement system can be installed at cable accessories to detect PD signals.

On-site testing and diagnosis of long medium voltage cables

Many parameters can influence the quality of the PD measurement and various issues are important during the execution of a PD measurement. In particular when testing long lengths of MV cables the PD detection sensitivity and particularly the PD site location is affected. To increase the measurement sensitivity the measurement system can be extended with an additional PD measuring unit at the far end of the cable. This unit measures PD activity with the conventional standardized PD detection synchronized with the damped AC test voltage. This two sided measurement provides higher detection sensitivity in the case of long cable lengths. Furthermore, when the measurement data of the 2 units at both ends of the cable are combined with each other, further analyses provides the PD site location in case of measured PD activity. In this way it is possible to test and diagnose longer lengths of MV cables.

Diagnosis of degradation effects of on-load tap changer in power transformers

By performing diagnostics on on-load tap changers by means of dynamic resistance measurements a condition diagnosis of high-speed resistor-type tap changers can result in pre-failure detection of contact degradation. It provides the measurement parameters that are most suitable for detecting these defects, such as the presence of a contact film, contact wear and pitting. The resistance curves of OLTCs are interpreted, to determine the occurring degradation mechanisms, which can be used to support strategic decisions about the maintenance or overhaul of the tap changer.

On-load tap changer diagnosis with dynamic resistance measurements

A modern tendency is to perform condition-based rather than time-based maintenance on power transformers. This requires the use of diagnostic measurements to know the condition of the tap changer and to determine when and what kind of maintenance is necessary. In addition, diagnostic measurements on OLTCs can be used for the pre-failure detection of defects not seen during maintenance and to assess the condition of parts that are not easily accessible. A number of diagnostic tests can be performed and utilities combine different tests to determine its need for maintenance. Several utilities apply dynamic resistance measurement (DRM) to OLTCs during regular maintenance. Results showed that DRM is sensitive to major degradation mechanisms in on-load tap changers.

On-site testing and diagnosis of distribution and transmission power cables using damped AC voltages

On-site testing and diagnosis of distribution and transmission power cables is one of the issues of asset management within power utilities. Due to the importance of power cables in the transmission network it is of importance to test the initial condition during after-laying, to test the actual condition of HV power cables during operation and to test the repair work after a failure.