STABILITY OF THE GAS-FILLED SURGE ARRESTERS CHARACTERISTICS UNDER SERVICE CONDITIONS

Working point of gaseous filled surge arresters (GFSA) is located near the Paschen curve minimum. It has been proven that the working point of GFSA is more stable when it is located in the vicinity of the Pasch en minimum, as in these points the curvature radius is largest and tha t enables the greatest stability of the working point during exploitat ion. This paper deals with tile influence of external factors (tempera tures from -200 degrees C to 200 degrees C, radiation by high speed ne utrons and thermal neutrons in controlled dosage) and working conditio ns on the stability of commercial GFSA characteristics. Under well con trolled laboratory conditions measurements of pulse and d.c. breakdown voltages were performed for several types of commercial surge arreste rs. During these measurements, following parameters were varied: 1) te mperature, 2) dosage and energy of the previous neutron radiation and 3) energy and the number of previous breakdown occurrences on a surge arrester. In accordance to these measurements, a software package was developed to enable the determination of analytical expressions for a suitable pulse characteristics. Statistical treatment of obtained resu lts determined the influence of temperature, previous neutron radiatio n and previous discharges on the stability of GFSA characteristics. Al so, by application of the statistical tests (U-test), the level of irr eversible changes in GFSA characteristics under experimental condition s was determined. Obtained results are explained theoretically.