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.Index Terms-Condition index, cable insulation, damped AC, diagnostic data analysis, statistical analysis, partial discharges. condition of MV/HV power cables depends on several aging factors. The ageing mechanism developing in function of service time and evaluation of PD processes in cable insulation is a complex process. Each part of a cable system is exposed to ageing under influence of thermal, mechanical, chemical and electrical loads during service life. Especially old serviced cable systems with during service on-going PD activity in the insulation and the accessories are extremely sensitive to overstressing. PD "weak spots" presence accelerated by external stresses like: mechanical damages and environmental changes [4] can have direct impact on cable circuit reliability and failures rate ( fig. 1). In the other hand it is well known that degradation and failure mechanisms have statistical nature and for estimation relatively actual condition of the cable circuit, knowledge based on large number of examined cable sets is necessary. With application of statistically estimated diagnostic parameters so called norm values can be used to set e.g. "typical" PD level for particular insulation type with certain age and condition. During service life this value can increase or stay on stable level and the trending of changes may be useful in analyzing the degradation progress. For this reason is important to look for data characteristic in as long service period as it as possible to observe "typical" PD behavior.
I. GENERALIN relation to reliability and availability of distribution cable connections, the MV power cables up to 20 kV play important role. A medium voltage...