Effect of SEBS on water treeing behaviors of cross-linked polyethylene
We investigated the effect of an aromatic polymer, styrene-(co-ethylene-butadiene)-styrene (SEBS), on water tree resistance of cross-linked polyethylene (XLPE). The XLPE/SEBS samples were characterized by means of gel content determination, different scanning calorimetry (DSC), scanning electron microscopy (SEM) and the accelerated water treeing experiment. Our results clearly indicated that the samples with SEBS showed improved water tree resistance in comparison to blank samples. It was also found that the blends had excellent dielectric property form the viewpoint of practical application.
Improvement of breakdown strength by additives and curing conditions on XLPE insulation for power cable
In This work, dielectric strength of XLPE insulation with lamellar densities varied by means of additives and curing conditions was investigated. To increase lamellar density of XLPE insulating material, two kinds of additives were used and cooling rates were controlled as curing conditions. TEM and X-ray diffraction was used to investigate the degree of lamellar density varied by additives. For breakdown strength of XLPE insulation with additives and different cooling rates, the mold-type cable specimens were made and evaluated with Weibull plot parameter. From the results, it is observed that the additives improve the lamellar density. In addition, we found that the dielectric strength of samples manufactured under slow cooling rate is higher than rapid cooling one. TEM and XRD analysis showed that the density in the XLPE insulation at the interface significantly affects dielectric strength of XLPE insulation.
Turbine blade temperature calculation and life estimation - a sensitivity analysis
Abstract The overall operating cost of the modern gas turbines is greatly influenced by the durability of hot section components operating at high temperatures. In turbine operating conditions, some defects may occur which can decrease hot section life. In the present paper, methods used for calculating blade temperature and life are demonstrated and validated. Using these methods, a set of sensitivity analyses on the parameters affecting temperature and life of a high pressure, high temperature turbine first stage blade is carried out. Investigated uncertainties are: (1) blade coating thickness, (2) coolant inlet pressure and temperature (as a result of secondary air system), and (3) gas turbine load variation. Results show that increasing thermal barrier coating thickness by 3 times, leads to rise in the blade life by 9 times. In addition, considering inlet cooling temperature and pressure, deviation in temperature has greater effect on blade life. One of the interesting points that can be realized from the results is that 300 hours operation at 70% load can be equal to one hour operation at base load.