Abstract
The accuracy of insulation defect diagnosis based on the dielectric spectrum response is severely influenced by temperature for oil-impregnated paper bushing. The dielectric loss (tan δ) mathematical model with a temperature–frequency factor to restrict the application of the frequency domain dielectric spectrum (FDS) for insulation diagnosis is not clear. In this paper, five temperatures are selected to study the frequency temperature characteristic of the FDS and polarization current for oil-impregnated paper bushing. The experimental results show that the temperature has different effects on the lower frequency (0.001 Hz–1 Hz) and higher frequency (1000 Hz–10 kHz) of FDS. With the increasing temperature, the lower frequency tan δ of 1 mHz–1 Hz shows a better pattern of exponential growth, while the higher frequency tan δ at 1 kHz–10 kHz shows the declining law with the rising temperature. With the increasing temperature, the polarization current shows a better pattern of exponential growth, while resistance obviously shows the declining law of the exponential pattern. The FDS curve of oil-impregnated paper bushings can be amended by the mathematical model of tan δ for the dielectric response on site for accuracy diagnosis.
Highlights
Oil-impregnated paper bushing is one of the main types of ultrahigh-voltage bushing, which plays key roles in the power transmission.1,2 Its operational reliability is directly related to the safety and stability of the entire power network
The experimental method of temperature combining the frequency dielectric spectrum and polarization current was provided for OIP bushings in this paper
The mathematic model of the dissipation factor with temperature can be used for the correction of the frequency domain dielectric spectrum (FDS) measurement in the site
Summary
Oil-impregnated paper bushing is one of the main types of ultrahigh-voltage bushing, which plays key roles in the power transmission. Its operational reliability is directly related to the safety and stability of the entire power network. In the process of operation of oil-impregnated paper bushing, about half of bushing failures result in an explosion and fire, especially in the case of long-term higher heat, electricity, and other external stress. It is very important for accurate evaluation and effective operation and maintenance of a bushing. The dielectric response of PDC and FDS in the laboratory for oil-immersed paper bushing tests at different temperatures, the effect of temperature changes on the measurement results and feature parameters, as well as the effect of temperature changes on the evaluation of the moisture content of insulation pressboard according to the dielectric response results are studied. This paper provides a basis for the follow-up study on the influence of temperature on the insulation diagnosis in a bushing
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