Improvement of dielectric performance of solid/gas composite insulation with YSZ/ZTA coatings

Abstract

N 2 has been introduced to gas-insulated switchgears (GIS) as an environmentally friendly insulation medium for SF 6 gas. Considering the low breakdown strength of N 2 , it’s essential to apply a dielectric coating on part of the electrode in GIS. In the current work, yttria-stabilized zirconia (YSZ) and zirconia-toughened alumina (ZTA) ceramics are tactfully applied as dielectric coating materials and successfully coated on the surface of rod electrode via high efficiency supersonic atmospheric plasma spraying method. It is demonstrated that both YSZ and ZTA have excellent thermal stability. In the measured frequency range 10 −2 –10 6 Hz, the dielectric constant ( ε ′) decreases with the increase in frequency. At measured temperatures (0–140 °C), ε ′ increases from 15.45 to 16.31 for YSZ ceramic at 1 kHz, while it varies between 30.23 and 39.34 for ZTA ceramic. As compared to that of bare electrode, the 50% BDV (U 50 ) of solid/gas composite insulation system is significantly improved when using YSZ and ZTA as coating materials. Furthermore, the U 50 increases with the increase of coating thickness. For the electrode coated with ZTA ceramic (500 μm), the U 50 value reaches to 86 kV, which is enhanced about 21.13% in comparison with that of bare electrode. With respect to YSZ ceramic coating (500 μm), a higher U 50 value of 88 kV is obtained. This is mainly due to that YSZ has a lower permittivity, which can generate a more uniform electric field distribution between the rod and plane electrodes, bringing about a higher breakdown voltage.

Investigation of Structural and Thermal Evolution in Novel Layered Perovskite NdSrMn2O5+δ via Neutron Powder Diffraction and Thermogravimetric Analysis

“…In the first step (200 °C-500 °C), the weight loss was high due to the moisture evaporation [47], and the decline in this region was about 0.084%. Above 500 °C, the weight loss was less because all the organic compounds and all other elements end up in this step and the sample behaves as a thermally stable material [48][49][50][51][52][53]; from 500 °C to 950 °C, the weight loss was approximately 0.016%. e total weight loss observed was about 0.10% for a temperature range between 20 and 950 °C which is comparable with other perovskite materials; SmBaMn 2 O 5+δ (0.036%) [54] and PrSrMn 2 O 5+δ [30].…”

Computational Insights into Degradation Probability of Small Fluorocarbon Compounds

“…Among potential candidates, perfluorocarbon (PFC) compounds have emerged as promising alternative insulating gases to replace SF 6 in various electrical applications primarily owing to the probability of identifying PFC compounds with relatively low GWP. − Additionally, PFCs exhibit excellent thermal and electrical performances under a wide range of operating conditions, ensuring the reliability and efficiency of electrical systems . Extensive efforts have been therefore dedicated to improving the other core insulating properties, such as dielectric strength, dielectric constant, and electron affinity, which should meet the guidelines for practical applications. − For instance, the dielectric strengths of various PFC compounds have been identified to range from 8.0 to 12 kV/mm with the lowest (highest) values for C 10 F 18 (C 2 F 6 ) . Recently, the 3M company developed various NOVEC gases with the aim of replacing the conventional SF 6 , represented by NOVEC-4710 gas (C 3 F 7 CN) .…”

Contribution to the Understanding of the Dielectric Breakdown Mechanism of ZTA Ceramics

“…The insulation performance of ZTA ceramics is the key to determining whether it can be used in electrical equipment, because once the ZTA ceramics break down, which causes irreversible damage to the entire equipment, thereby failing. [ 11 ] Therefore, research on the insulating properties of ZTA ceramics is essential.…”