Dielectric Measurement Based Deducted Quantities to Track Repetitive, Short-Term Thermal Aging of Polyvinyl Chloride (PVC) Cable Insulation

The effect of short-term (3- and 6-h-long) periodic thermal aging was investigated at three different temperatures on PVC cables and PVC films. Three different temperatures (110, 125, and 140 degrees C) were used for aging PVC cables and one (110 degrees C) for PVC films. PVC films were prepared for the investigation containing 0, 30, 40, and 50 weight percent of dioctyl phthalate plasticizer (DOP). The effect of short-term thermal aging was monitored by electrical (dielectric spectrum and voltage response measurement) and mechanical (Shore D hardness) methods. From the loss factor measurements, different deducted quantities were calculated and compared with Shore D hardness, which has been shown to be a parameter reflecting the effect of short-term thermal aging on PVC insulation. The measurements revealed that Shore D hardness is not the best property for monitoring aging. Instead, increasing dissipated power and the shifting behavior of tan delta-frequency curves proved to be the best phenomena for assessing the impact of thermal aging. Simple deducted quantities may provide a basis for following short-term thermal aging.