A New Concentration Detection System for SF₆/N₂ Mixture Gas in Extra/Ultra High Voltage Power Transmission Systems

Abstract

Abstract-This paper develops a new detection system, for the first time, to detect the gas concentrations of the SF 6 /N 2 mixture in extra/ultra-high voltage power transmission systems. The concentrations of SF 6 and N 2 are calculated from the thermal conductivity function of the mixture gas. The main contribution of this work is that a specially-designed thermostatic chamber with adaptive temperature controller is developed to ensure constant pressure of the gas flowed through the thermal conductivity sensor. Another contribution is the combination of multiple sensors (e.g. humidity and electrochemical sensors), which enables the detector to address the penetration effects of H 2 O and O 2 in the SF 6 /N 2 mixture. Experimental evaluation results using the prototype demonstrated that satisfactory accuracy (±1% of the measurement error) has been achieved for the concentration detection of the SF 6 /N 2 mixture under variable operation conditions. Compared with existing detection techniques, the proposed detector not only can detect the SF 6 /N 2 concentration by taking the air infiltration effect into account, but also reduce the cost.Index Terms-SF 6 /N 2 , gas mixture, microfluidic thermal conductivity sensor, constant temperature control, trace O 2

A novel design of flow structure model for online viscosity measurement

“…For example, model D6-T5-R30 was simulated with a 6 mm tube diameter, five spiral turns and a 30 mm spiral radius. The finite element modelling approach [26][27][28] was employed to establish the CFD simulation models. Taking model D6-T5-R30 as an example, its grid model, grid quality and boundary conditions are shown in Figure 3.…”

SF6 mixed in N2 gas sensing responses from CMOS-compatible AlN and ScAlN pyroelectric detectors

“…[3][4] Despite its advantageous properties in electrical insulating systems, SF6 poses a threat to the environment by being a potent greenhouse gas, having the ability to trap infrared radiation 23,500 times more than carbon dioxide (CO2). 5 Replacement of SF6 with alternative non-greenhouse gases have been rigorously researched on [6][7] with SF6 mixed in nitrogen (N2) [8][9][10] as an alternative effort to dilute the concentration of SF6 used in electrical insulating systems. Concurrent to the effort of finding replacement gases or diluting SF6, it is important to identify and prevent SF6 leakage into the environment.…”

Thermal Decomposition Properties of Epoxy Resin in SF6/N2 Mixture

“…SF 6 gas is colorless, odorless and nontoxic, and is widely used as power equipment’s insulation material because of its excellent arc-extinguishing and insulating properties [1,2,3,4,5,6,7]. Its chemical property is so stable that it can stably remain in the atmosphere for 2300 years, and its global warming potential (GWP) is 2500 times that of CO 2 .…”

“…To reduce the use of SF 6 , researchers worldwide have developed new alternatives such as C 4 F 7 N, C 5 F 10 O, SF 6 /CO 2 , and SF 6 /N 2 mixture as insulation gases and put them into practice [3,5,8,9,10]. Among these gases, an SF 6 /N 2 mixture with low SF 6 volume fraction has been widely used in electric equipment such as gas insulated transmission lines (GIL) [6,11,12,13,14]. In the 1970s, 420/550 kV transmission lines of 20% SF 6 /N 2 (volume fraction of SF 6 is 20%) were developed by SIMENS and put into use in Geneva, Switzerland, which proved to be of high economic benefits.…”