Diagnostics of HV power cables are playing an important role in the meaning of two aspects: 1) on-site diagnostic of new installation, where a commissioning test has to prove the absence of any defects in the cable insulation and accessories, after transportation and installation. 2) On-site diagnostic of a serviced aged power cable where the condition after a period in service or information about workmanship of repairs has to be known. As it is known some installation defects can result in breakdown even after a successful after-laying test. Obtaining more diagnostic parameters like; Withstand Voltage, Partial Discharges (PD) and Dielectric Loss (tan ¿), providing a indication of insulation condition and accessory performance. In this paper several examples of on-site tests on new and serviced aged XLPE HV power cables will be discussed. Examples of: after-repair, after-laying, and condition assessment tests will be presented as performed with Damped AC diagnostics.@en

Partial discharges (PD) diagnostics play an important role in insulation diagnosis of HV power cables all over the world. By application of such diagnostic it is possible to asses the quality of final product (cable) during factory test, during after-laying test or during service life. In this way knowledge about the discharging defects in a particular cable insulation system including the accessories can be done. Using sensitive PD diagnostic parameters like: PD inception voltage, PD magnitude, PD fingerprint pattern characteristics, can help to recognize the symptoms of discharging insulation weak spots. In this contribution the application of two different PD detection methods will be discussed: conventional PD detection according to IEC 60270 and unconventional radio frequency (RF) PD detection. To investigate the sensitivity issues both methods have been applied to full size 150 kV cables system (length of 100 m). An example of insulation defect in a cable joint was used to investigate above mentioned PD detections methods as applied at different types of AC voltage energizing: continuous AC and damped AC voltages. Observed PD parameters have been analyzed and compared for both energizing methods (AC 50 Hz and DAC 60 Hz and 400 Hz) and PD detection methods.@en

This document describes application of statistical analysis to several diagnostic parameters obtained during on-site measurements on MV power cables. The goal of this analysis is to estimate statistical borders values for different diagnostic parameters related to PD phenomena for cable insulation as well as different cable accessories like joint and termination. Data input introduced to analysis consist of mass, XLPE and mixed (XLPE +PILC) insulated power cables. Investigated parameters were obtained with application of damped AC (DAC) diagnostic system during on-site non-destructive tests. For the purpose of clear distinction between cable components (joints, termination, insulation parts) categories, of different cable accessories were created). 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 done. Additionally crated in this way measuring criteria based on calculated statistical norms by fitting data to several statistic distributions were employed for overall condition indexing. Later on condition indexing was used to indicate percentage ration how big population of insulation and components are in very good, good and moderate condition.@en

Knowledge rules for paper/oil insulated high voltage (HV) power cables are necessary to support asset management decision processes. For development of these knowledge rules investigation has been done into a diagnostic method, for integral condition assessment of paper/oil insulation to DC voltage charging. This method is called the recovery voltage measurement and is based on the dielectric response of cable insulation. In the recovery voltage (RV), parameters have been investigated on possibility to indicate insulation degradation. In this paper single and periodic measurements with different temperatures have been performed. These measurements result in the conclusion that an increase in insulation degradation can be observed by selected recovery voltage parameters as well as dielectric losses behavior in function of test voltage. Measurement results of HV power cables performed at two temperatures can be used in line with dielectric losses measurements to support condition assessment.@en

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: ldr The influence of voltage stress on tan delta measured on samples taken from different parts of cable insulation: close to conductor, middle part and outer part. ldrThe behaviour of dielectric losses as a function of test voltage and temperature for paper samples in different age condition.@en

Already existing knowledge about aging phenomenon in type insulated power cables as well as measuring criteria has been continuously improved during last 20-30 years. Nowadays many HV power circuit with paper insulation reach their end of service life time due to extensive deterioration of insulation under high operational temperatures and electrical, mechanical overstressing. Growing demand of energy market for new sources of energy and increment of current loads on existing serviced HV power transmission cables change aging rates and lead to often unexpected failures. Accelerate in this way insulation deterioration processes in many cases need new interpretation of diagnostic parameters related to aging of cable insulation to support condition assessment decision and foreseen failure development. Additionally when costs of repairs, cable replacement and customer claims due to breakdown and blackouts are taken into consideration, finance balance for the repair of a single failure in a 150 kV link can costs around 75 kC. For this reason reliable judgment of actual cable condition with available on market diagnostic methods is in great of importance from utility point of view. In this contribution effort was put to estimate actual service condition of four sections of external gas pressure 110 kV-150 kV power cables with two integral diagnostic methods. Interpretation of diagnostic data has been done with aspect to several diagnostic parameters. All relevant diagnostic parameters were obtained during on-site tests in with low-voltage method based on recovery voltage phenomena and high voltage method based in DAC voltages to estimated dielectric losses.@en

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.@en

Diagnostics of HV power cables are playing an important role in the meaning of two aspects: 1) on-site diagnostic of new installation, where a commissioning test has to prove the absence of any defects in the cable insulation and accessories, after transportation and installation. 2) On-site diagnostic of a serviced aged power cable where the condition after a period in service or information about workmanship of repairs has to be known. As it is known some installation defects can result in breakdown even after a successful after-laying test. Obtaining more diagnostic parameters like; Withstand Voltage, Partial Discharges (PD) and Dielectric Loss (tan ¿), providing a indication of insulation condition and accessory performance. In this paper several examples of on-site tests on new and serviced aged XLPE HV power cables will be discussed. Examples of: after-repair, after-laying, and condition assessment tests will be presented as performed with Damped AC diagnostics.@en

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.@en

The thesis focuses on on-site testing and diagnosis of transmission power cables circuits. Based on the application of methods for on-site voltage generation and its use for advanced diagnosis, comprehensive testing and diagnostic procedures have been investigated in this thesis.@en