Piotr Cichecki

On-site testing and PD diagnosis of high voltage power cables

In addition to after-laying of new-installed high voltage (HV) power cables the use of on-site non-destructive on-site testing and diagnosis of service aged power cables is becoming an important issue to determine the actual condition of the cable systems and to determine the future performances. In this paper based on field experience an overview is presented on on-site testing and partial discharge diagnosis of HV power cables with regard to on-site testing methods: energizing, diagnostic aspects, possibilities and implications for new and service aged power cables.

Statistical approach in power cables diagnostic data analysis

This paper describes the application of statistical analysis to the on-site diagnostic data of HV power cables to set-up knowledge rules and measuring criteria for particular cable insulations and accessory (joints, terminations). Such approaches can successfully be employed later in Asset Management decision processes. In this paper based on different cable data populations of two diagnostic parameters like: partial discharges and tan delta, statistical analysis has been applied. Besides this, several practical examples also have been presented.

Use of dissipation factor for life consumption assessment and future life modeling of oil-filled high-voltage power cables

Tan δ measurements can be used to assess the condition of OF insulation in HV power cables. Data showing the behavior of tan δ as a function of temperature at constant electrical stress, and as a function of electrical stress at constant temperature, at different stages of degradation (or aging) are essential. By combining on-site and laboratory measurements, the remaining service lifetime of a cable can be estimated for various future loading levels using a model incorporating ground temperature, the age of the cable, and its loading history.

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.

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.

Dielectric losses diagnosis of serviced aged oil impregnated paper insulation of HV power cables.

This contribution is focused on the application of laboratory dielectric losses measurements to the insulation of service aged oil-impregnated HV power cables. The goal is to investigate the dependence between the electrical and temperature stresses to impregnated paper insulation at different aging stages. By means of laboratory tests with differential transformer testing circuit on aged paper samples the following has been investigated: • The influence of voltage stress on tan δ measured on samples taken from different parts of cable insulation: close to conductor, middle part and outer part. • The behaviour of dielectric losses as a function of test voltage and temperature for paper samples in different age condition.

Building a Transformer Defects Database for UHF Partial Discharge Diagnostics

In the case of a defective transformer, when a partial discharge is detected and recorded, critical information can be deduced from its pattern, such as the type of defect, its criticality or even information on the level of degradation of the insulation. This information can help to determine the remaining life of the transformer and thus provide criteria for its maintenance and operation. In this paper different artificial PD patterns will be recorded in the laboratory, representative of specific transformer defects, in order to build a database for comparison purposes when measuring on-line. This can greatly improve the recognition and identification of the defect and thus help take some important life assessment conclusions on the transformer.

Life time estimation of serviced aged oil-paper insulated HV power cables based on the dielectric loss measurements (tan δ)

this contribution focuses on the application of dielectric loss measurements for service aged oil-impregnated high voltage power cables. The results of the project focused on condition assessment of service aged oil-impregnated HV power cables will be discussed. The final goal of this project is: to develop by using laboratory and on-site tanδ measurements a tool to support the condition assessment and asset management decisions. By combination laboratory measurements and on-site diagnostics, an investigation have been performed into several complete cable circuits to find the relation between electrical and thermal stresses of paper oil-impregnated insulation, at different aging stages. The result of this investigation, in particular influence of electrical and thermal stressing of samples in different stage of aging, with combination of on-site diagnostics has been applied to develop a tool for supporting asset management decision process.

Statistical analysis of large amount of power cables diagnostic data

In this contribution statistical analysis were applied to evaluate condition of serviced aged MV power cables systems. Analysis were based on large number of diagnostic data as obtained from the on-site inspections of 89 mass insulated power cables, 26 XLPE insulated power cables and 126 mixed-insulated power cable. Statistical analysis input data was represented with several diagnostic parameters regarding to partial discharges phenomenon (PD). Investigated parameters were obtained with application of damped AC (DAC) diagnostic system during on-site tests. After a survey of all relevant parameters describing condition of the particular cable system components, sub-groups of different cable accessories were created (e.g. joints, termination, insulation types) For proper interpretation of collected data related to cable insulation condition as well as different accessories condition, categorization based on such diagnostic parameters e.g. PDIV (partial discharge inception voltage), PD occurrence, and PD mappings was assumed. Moreover investigated statistically PD parameters were employed to estimate experience norms and measuring criteria. Based on knowledge rules and estimated statistically norms example of so called ldquoexperimental condition indexrdquo was used to indicate overall condition of discussed MV power cables systems.

On-site condition monitoring of HV power cables up to 150kV

For advanced, non-destructive on-site condition monitoring of HV power cables up to 150 kV by partial discharge detection and dielectric losses measurement it is necessary to energize the disconnected cable system. One of the methods available for this purpose is based on applying damped AC voltages up to 150 kV. In this contribution, the use of modern technological solutions in power electronics and signal processing as well as in technical design and production methods will be discussed on the basis of ultra light system which is able to on-site service aged HV cables.