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

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

For advanced, non-destructive on-site condition monitoring of HV power cables up to 150kV 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 150kV. In this paper, 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 the ultra light system (300kg) which is able to test cables up to 20km lengths.@en