SF6 Gas Leakage On-line Monitoring and Alarm System

The gas leakage event generated during the application of SF6 insulation equipment will reduce its insulation performance and pollute the environment. A real-time monitoring system is established for SF6 gas insulation equipment in substation. SF6 gas status is collected mainly by CO2 laser camera, and the leakage source is accurately located by image feature acquisition measures, and the leakage amount is evaluated and determined. This paper mainly discusses and analyzes SF6 gas leakage on-line monitoring and alarm system, hoping to provide reference for relevant personnel.

1. Structure analysis of the SF6 monitor system

For the SF6 gas leakage monitoring part, the laser camera is mainly used to irradiate the gas leakage area through infrared radiation. At this time, SF6 gas will absorb the incident laser, invisible SF6 gas will show black smoke, and the infrared detector will generate images on the screen. The image collected by the camera can be processed and analyzed, and the gas leakage movement track can be obtained, the leakage source can be located, and the leakage amount can be judged. For monitoring data transmission, the wireless module is installed on the camera, and the picture information is transmitted to the wireless module through wireless telecommunication technology, and the information is transmitted through wireless network, which can not only ensure the safe transmission of data information, but also deal with the problems existing in the monitoring equipment, such as a host of taps and complex communication cable wiring, so as to effectively reduce resource consumption.

For background monitoring, the background monitoring receives and transmits picture information, and uses the upper computer to evaluate and display the SF6 gas leakage state, as well as to call and store data. The status display bar can display the data results in real time. It can store equipment images in a database so that they can be retrieved at any time during post-maintenance. The SF6 gas leakage state is shown in the form of a graph, which can optimize and adjust the maintenance plan and comprehensively improve the maintenance efficiency. The system uses touchable large screen true color display, thermal infrared sensor, fan control manual/automatic selection switch. SF6 gas leakage monitoring system is an open system platform that integrates laser technology, data acquisition, data processing and communication technology.

2. Hardware and software design of SF6 monitor system

 
(1) Hardware design

The technique mainly applies Lamberbier's law: When the wavelength of light passes through the measured gas, the intensity of the light decreases and the measured gas content satisfies the law. After red light enters the gas under test, it absorbs gas molecules. The sensor mainly applies the dual-beam detection principle, in which one is the reference speed of light, and the other is the measurement beam. Compared with a single beam, dual-wavelength dual-beam technology can prevent drift due to aging of the light source, contamination of the monitor, and surface of the sampling pool. The monochromatic light of the wavelength modulated by the reference channel will not absorb the measured gas. The stable signal generated by it can only be affected by external factors, not by the measured gas.

(2) Software design

SF6 gas leakage monitoring system software mainly includes functions of gas concentration monitoring and analysis, as well as field programmable gate array sampling and calculation by digital signal processing; The former is mainly developed and designed using C language or assembly language, and its software functions include gas concentration detection, wireless communication, control loop and touch screen man-machine interface. The latter mainly uses QuartusI1 environment developing system language functions, measures and calculates data in field programmable gate array, and then transmits it to ARM soft core to obtain data effective values.

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