Informatics Publishing Limited

C. Viswanatha ¹, V. Mohan Babu ², K. G. Rakesh ³

Affiliations
1 Joint Director, DCCD, Central Power Researh Institute, Bangalore - 560080, IN
2 Engineering Assistant, DCCD Central Power Researh Institute, Bangalore - 560080, IN
3 Engineering Assistant, DCCD, Central Power Researh Institute, Bangalore - 560080, IN

Abstract

The circuit breaker of SF₆ type has many advantages over conventional type, being better performance and dielectric properties. SF₆ circuit breaker are now being employed widely in substations for better electrical network functioning. Even then, it is associated with some failures which are reported in the field. Two kinds of circuit breaker are studied in this work with point of thermal behavior. A rated current is passed through SF₆ circuit breaker and thermal mapping is recorded at incoming terminal and outgoing terminal, enclosure and other points for investigations. The steady state condition of temperature is taken as reference in finding temperature rise over the environment condition. The temperature at predecided points of circuit breaker both for passed sample and failed sample are recorded. The data obtained is analyzed and attempt is made to understand the failure of SF₆ breaker in the context of excessive temperature than the prescribed limits of International Specifications. This paper deals with sample arrangement, experimental details, results and analysis. Both failed sample and passed sample have shown contrast performance in final analysis.

Keywords

Circuit breaker, temperature, thermal mapping, steady state, SF6 gas, thermocouples.

Full Text

     

Moumita Naskar ¹, P. N. Ashitha ¹, K. G. Rakesh ¹

Affiliations
1 Insulation Division, Central Power Research Institute, Bangalore – 560080, Karnataka, IN

Abstract

Underground Polyvinylchloride (PVC) sheath power cables are exposed to the atmospheric condition during installation. Depending on the atmospheric conditions the cable sheath is facing extreme environmental stresses such as ambient temperature (high and low), direct sunlight (UV) radiation, rain or water accumulation etc. The life of PVC cables is reduced by being exposed to harsh environmental conditions and can subsequently damage the unprotected cables. This work is aimed to the study of the effects of UV radiation and low temperature on PVC cable outer sheaths. Three commercially available PVC cable were chosen for the study. UV exposed PVC insulations become brittle after UV exposure and in low temperature. UV exposure eventually results in material degradation, diminishing the performance characteristics of the material. Thermogravimetric Analysis (TGA) was used to characterize the thermal behavior of PVC cable insulation materials before and after UV ageing. In addition, Fourier-transform infrared spectroscopy (FTIR) was used to reveal the chemical processes that caused the UV degradation of the sample. A good agreement between results of the methods was found. Exposure to low temperature resulted in a reduction in stiffness of the polymeric structure caused embrittlement which transformed the PVC structure from a flexible material capable of undergoing large strain elastic behaviour to a stiffer material with higher yield behaviour.

Keywords

Cold Elongation, UV Radiation, FTIR, PVC, TGA

Full Text