RESUMO
The use of flexible, built-in, ultra-high-frequency (UHF) antenna sensors is an effective method to solve the weak high-frequency electromagnetic wave signal sensing of partial discharge (PD) inside gas-insulated switchgears (GISs), and the compatibility of flexible UHF antenna sensor substrate materials and SF6/N2 mixtures is the key to the realization of a flexible UHF antenna sensor inside a GIS. Based on this, this paper builds an experimental platform for the compatibility of a 30% SF6/70% N2 gas mixture and a PD flexible UHF antenna sensor substrate and conducts compatibility experiments between the 30% SF6/70% N2 gas mixture and PD flexible UHF antenna sensor substrate under different temperatures in combination with the actual operating temperature range of the GIS. In this article, a Fourier transform infrared spectrometer, scanning electron microscope and X-ray photoelectron spectrometer were used to test and analyze the gas composition, the surface morphology and the elemental change in the PD flexible UHF antenna sensor substrate, respectively. PET material will be slightly oxidized under the environment of a 30% SF6/70% N2 gas mixture at 110 °C, PI material will generate metal fluoride under the environment of a 30% SF6/70% N2 gas mixture and only PDMS material will remain stable under the environment of a 30% SF6/70% N2 gas mixture; therefore, it is appropriate to use PDMS substrate in the development of flexible UHF antenna sensors.
RESUMO
Spiral antenna sensors are commonly used in partial discharge (PD) ultra-high frequency (UHF) detection in gas-insulated switchgears (GISs). However, most of the existing UHF spiral antenna sensors are based on a rigid base and balun, such as FR-4. The safe built-in installation of antenna sensors requires the complex structural transformation of GISs. To solve this problem, a low-profile spiral antenna sensor is designed based on a polyimide (PI) flexible base, and its performance is optimized by improving the clearance ratio. The simulation and measurement results show that the profile height and diameter of the designed antenna sensor is 0.3 mm and 137 mm, which is 99.7% and 25.4% smaller than the traditional spiral antenna. Under a different bending radius, the antenna sensor can maintain VSWR ≤ 5 in 650 MHz~3 GHz, and its maximum gre is up to 6.1 dB. Finally, the PD detection performance of the antenna sensor is carried out on a real 220 kV GIS. The results show that, after being built in, the PD with a weak discharge magnitude of 4.5 pC can be effectively detected by the antenna sensor, and the antenna sensor has the ability to quantify the severity of PD. In addition, through the simulation, the antenna sensor has potential for the detection of micro water in GISs.
RESUMO
The stability and processing capacity of membrane bioreactor can be improved with long sludge retention time. However, phosphorus removal will be markedly reduced under long sludge retention time and membrane fouling will be aggravated. Adding aluminum (Al) salt is a common way to achieve chemical phosphorus removal and membrane fouling reduction. But, accumulated Al will cause the decline of metabolic activity of activated sludge. In this study, biofilm-membrane flocculation reactor was proposed to enhance simultaneous nutrients removal and membrane fouling reduction. It showed that the removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) in biofilm-membrane flocculation reactor were 95.7%, 96.7%, 87.4%, and 97.2%, respectively. Compared with the control group, accumulated Al increased extracellular polymeric substances (EPS) secretion by 1.9%-35.4%, biofilm biomass by 12.4%-26.1%, and the activities of ammonia oxidation bacteria (AOB) and nitrite oxidation bacteria (NOB) in the biofilm increased by 42.9% and 65.9%, respectively. The relative abundance of Nitrospira, Dechloromonas, and Terrimonas in the biofilm increased by 1.78%, 3.01%, and 2.88%, respectively, which was conducive to facilitating the nitrification. Therefore, biofilm-membrane flocculation reactor is a promising way for enhancing simultaneous nutrients removal and membrane fouling reduction.
