Abstract
The rapid growth of power grid capacity and the widespread use of a large number of power electronics and non-linear loads have led to harmonics in the power system. Harmonics in the power system will cause safety hazards to the normal operation of power equipment, exacerbate the aging of insulation materials, and reducing the overall operation reliability of the system. In the present work, we used power frequency ac voltage superimposed harmonics to carry out ageing experiments on power cable terminals. Then, we tested the infrared spectra, dielectric spectra, electrical conductivity, and surface potential decay characteristics of silicone rubber insulation materials on the cable terminals aged for different times. The experimental results show that the dielectric constant and dielectric loss of silicone rubber gradually increase with the aging time. In particular, the dielectric loss of silicone rubber changed greatly at low frequencies. The effect of dc conductance of aged silicone rubber on dielectric loss is significantly enhanced at low frequencies, which causes the dielectric loss to increase as the frequency decreases following an inverse power law. The surface potential decay rates of silicone rubber insulation after positive and negative corona charging accelerate with increasing the aging time, which is consistent with the experimental results of electrical conductivity. By analyzing the distribution characteristics of electron and hole traps in silicone rubbers, it is found that the trap energy levels of electron and hole traps become shallower as the operating time increases. The calculation of the carrier hopping conduction model shows that the shallow trap formed with increasing the aging time will lead to increases in both carrier mobility and conductivity. When the conductivity rises to a certain value, the silicone rubber will lose its insulation performance, resulting in insulation failure.
Highlights
The rapid growth of power grid capacity, the development of power electronics technology, and the wide utilization of a large number of power electronic devices and non-linear loads results in voltage and current distortions of the power system and generation of harmonic components [1].Various iron core equipment, such as transformers, electromagnetic voltage transformers, and reactors; Appl
The test used a three-electrode system, which was placed in the shielding box and included high-voltage, measuring, Figure 2 shows the Fourier-transform infrared spectrometer (FTIR) spectra of the silicone rubbers on the cable terminals operated for and grounding electrodes
It is generally believed that the lifespan of insulation materials in power equipment will be reduced by 50% for every
Summary
The rapid growth of power grid capacity, the development of power electronics technology, and the wide utilization of a large number of power electronic devices and non-linear loads results in voltage and current distortions of the power system and generation of harmonic components [1]. Various iron core equipment, such as transformers, electromagnetic voltage transformers, and reactors; Appl. Sci. 2020, 10, 6006 various ac/dc converters, such as rectifiers and inverters; bidirectional thyristors; and controllable switches can generate harmonic components during operation. Harmonic components in the power system will cause safety hazards to the normal operation of the power transmission, transformation, and power consumption; reduce the quality of power; and exacerbate the aging of internal insulation materials in power equipment, which may reduce the overall operating life of the power system [2]
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