The indoor SF6 gas and oxygen leakage quantitative online monitoring and alarm system is an online monitoring and alarm system for SF6 insulation gas leakage in indoor SF6 combined electrical equipment in new unmanned substations.
The indoor SF6 and oxygen leakage quantitative online monitoring and alarm system uses imported new high-sensitivity SF6-O2 sensors and temperature and humidity sensors. It can promptly detect even minute changes in the concentration of indoor SF6 and O2. The sensors convert the monitored SF6 gas into an electrical signal through thermal decomposition and chemical synthesis. After signal amplification and anti-interference network, it is converted into a digital signal by a 16-bit high-precision A/D converter and sent to a single-chip computer. The single-chip computer analyzes and processes the signal, and zero-point tracking transmits the results to the main controller via a 485 bus module. The main controller processes, stores, displays in color, alarms, controls the fan, and transmits the results to a remote computer.
A discussion of the characteristics and hazards of SF6 gas:
SF6 was synthesized in 1900 by two French chemists, Moissan and Lebeau. Since the 1960s, SF6 has been widely used in high-voltage circuit breakers and substation equipment in the global power industry as an extremely superior insulating and arc-quenching medium. Today, SF6 gas is almost the sole insulating and arc-quenching medium in high-voltage and ultra-high-voltage circuit breakers and GIS (Gas Insulated Switchgear).
Pure SF6 gas is colorless, odorless, and non-flammable, and its chemical properties are exceptionally stable at room temperature, being more than five times the density of air. However, in power systems, SF6 gas primarily functions as an insulation and arc-quenching medium. Under the influence of factors such as electric arcs, partial discharges, and high temperatures, SF6 gas will decompose. Its decomposition products, upon contact with moisture, form corrosive electrolytes. In particular, some highly toxic decomposition products, such as SF4, S2F2, SOF2, HF, and SO2, can cause dizziness, pulmonary edema, and even coma and death if inhaled in large quantities.
In relatively sealed indoor environments, due to poor air circulation, SF6 and its decomposition products accumulate. Since SF6 gas is colorless and odorless, it poses a significant hazard to inspection and maintenance personnel. When a GIS (Gas Insulated Switchgear) system leaks, SF6 gas accumulates in the lower space above the floor, causing localized oxygen deficiency and potentially leading to asphyxiation and a major accident.
Regarding SF6 security rules
The "Electric Power Safety Work Regulations" (Power Plant and Substation Section) specifically stipulate that the SF6 gas concentration in the power distribution room equipped with SF6 equipment must be less than 1000ppm. In addition to installing powerful ventilation devices, it is also necessary to install an oxygen meter with alarm function and an SF6 gas concentration monitoring alarm device.
Excerpt from SF6 safety regulations:
Article 191. Power distribution rooms and SF6 gas laboratories containing SF6 equipment must be equipped with powerful ventilation systems. Air vents should be located at the lower part of the room.
Article 192. When equipment is filled with SF6 gas indoors, the relative humidity of the surrounding environment must be 80%, the ventilation system must be turned on, and SF6 gas leakage into the work area must be prevented. The SF6 gas content in the air of the work area must not exceed 1000 ppm.
Article 196: Before entering the SF6 power distribution room, staff must ventilate for 15 minutes and measure the SF6 gas content with a leak detector. It is necessary to avoid having only one person enter the SF6 power distribution room for inspection, and no one is allowed to enter to perform maintenance work.
Article 198. Before entering the low-level area of the SF6 power distribution room or cable trench for work, staff shall first test whether the oxygen content (not less than 18%) and SF6 gas content are qualified.
Article 199. An oxygen meter and an SF6 gas leak alarm shall be installed in the low-level area of the SF6 power distribution room. These instruments shall be tested regularly to ensure they are in good working order.
Article 203 In the event of an emergency, all ventilation systems should be activated immediately for ventilation. In the event of a ruptured equipment diaphragm, power should be cut off and the area wiped clean with gasoline or acetone.
The SF6 and oxygen online monitoring and alarm system is mainly used in the 35KV SF6 switch room and the 500KV, 220KV and 110KV GIS room in substations to monitor the SF6 gas leakage and oxygen content in the air in real time.
When an SF6 gas leak occurs, because SF6 is more than five times denser than air, it accumulates in lower-level spaces, causing localized oxygen deficiency and potentially leading to a major accident. The SF6 and oxygen online monitoring and alarm system employs multiple sets of new, high-sensitivity imported SF6-O2 sensors, as well as temperature and humidity sensors. When the concentration of SF6 and O2 in the room changes slightly, the sensors immediately respond to these changes, effectively monitoring even SF6 concentrations as low as 10 ppmv. The concentration changes monitored by the sensors are converted into SF6 digital signals via a transmitter, A/D module, SF6 communication module, and microcontroller control. These signals are then sent to the main controller via a field RS-485 bus. The main controller processes and stores the data, determines whether to trigger an alarm, activate the fan, and perform remote communication functions.
ICbuy.com provides imported SF6-O2 sensors and temperature and humidity sensors for SF6 and oxygen online monitoring and alarm systems: Infrared SF6 sensor IR-SF6, SF6 infrared sensor WFS-S1-S, oxygen sensor KE-25F3, and temperature and humidity sensor module HTW-211.
The Figaro KE-25F3 oxygen sensor from Japan: The GS KE series oxygen sensors (KE-25F3/KE-25/KE-50) are a unique galvanic cell type oxygen sensor developed in Japan in 1985. Their significant features include long service life, excellent chemical stability, and resistance to CO2 interference. The KE series sensors were developed to meet the growing demand for oxygen detection in various industries, such as combustible gas detection, biotechnology applications, medical device applications, and residential gas appliances.
The IR-SF6 series diffused SF6 gas sensor is based on single-source dual-wavelength non-dispersive infrared (NDIR) measurement technology. It utilizes a high-end infrared light source and detector, employing gold-plated components as the optical path reflection channel to improve measurement accuracy and stability. Incorporating several advanced technologies enhances its environmental adaptability. It can be widely used in industries such as power, petrochemicals, food processing, and semiconductors, and is suitable for leak alarms, environmental protection, and industrial safety applications.
WINFOSS WFS-S1-S SF6 Infrared Sensor (Switzerland): Based on dual-beam, dual-wavelength infrared measurement technology and high-precision digital processing technology, the SF6 infrared sensor (WFS-S1-S) is widely used in SF6 gas leak monitoring (0-100ppm) in high-voltage switchgear GIS rooms, SF6 gas leak detectors (0-50ppm), and SF6 purity analyzers (0-100%). It integrates complete automatic drift control and temperature compensation circuitry.
The SF6 infrared sensor (WFS-S1-S/WFS-S1-S) employs dual-beam non-dispersive infrared (NDIR) detection technology, offering advantages such as resistance to interference from other gases, easy maintenance, high stability, and built-in temperature compensation. It supports the standard Modbus ASCII protocol and offers selectable digital and analog outputs.
Samyoung's HTW-211 temperature and humidity sensor module from South Korea is a precise and reliable humidity measurement sensor based on HumiChip®. The sensor's humidity output is temperature-compensated and is a linear voltage, allowing direct connection to a microcomputer with an ADC input. Specially designed molding and coating materials ensure durability and reliability even in harsh environments. It can be widely used in smart homes, HCPV control, industrial process control, medical, automotive, environmental monitoring, and many other fields.
The SF6 and oxygen online monitoring and alarm system can monitor up to 64 monitoring points in the environment. It can also be controlled by a network of multiple main control units and communicate with the power station automation system. Effective monitoring of indoor SF6 and O2 concentrations greatly improves the safety of unattended substation operation, especially ensuring the personal safety of daily inspection and maintenance personnel.
