Research And Design Of Cable Intermediate Joint Fire Alarm And Automatic Fire Extinguishing System In Power Transmission And Distribution Line

As a weak link in the operation of cables in transmission and distribution lines,the middle connector of the cable will cause long-term power outages and affect the stable economic development.Therefore,it is very important to propose a reliable,safe and intelligent fire prevention and fire fighting scheme for the middle of cable joints,which can reduce the fire frequency of the middle joint of the cable and reduce the economic loss caused by the fire of the middle joint of the cable.In this thesis,through the analysis of the characteristics of the fire in the middle of the cable joint,a fire prevention and fire extinguishing plan for the middle joint of the cable can be realized,and the fire extinguishing system and the early warning system are verified by simulating fire experiments and simulated alarm experiments.feasibility.The main research results are as follows:1.The fire of the intermediate connector of the cable is caused by the arc,overheating and the external heat source caused by the fault of the intermediate connector of the cable,which ignites the insulating layer and the protective layer outside the conductor of the middle conductor of the cable.2.The fire characteristics of the middle connector of the cable include: long-term accumulation of heat in the middle of the cable connector,which is prone to sudden fire;failure of the middle connector of the cable can easily lead to explosion and strong destructiveness;the cable bundles burn and the fire spreads rapidly;easy to generate and accumulate a lot of high-temperature toxic smoke Gas;fire damage is severe and has a wide range of impact.It is difficult to locate faults and fires,and it is difficult to quickly locate,save,and quickly repair after a fire.3.According to the theoretical analysis and practical requirements,the overall design of the fire alarm system for the middle joints of the cable and the automatic fire extinguishing system was carried out,and the prototype of the system was designed based on this.The system consists of a fire warning system and an automatic fire extinguishing device.The fire warning system is composed of a fire detection module,a fire alarm controller,and an early warning signal transmission module.The automatic fire extinguishing device uses an aerosol fire extinguishing agent as the driving force for non-storage pressure super Fine dry powder fire extinguishing device.The fire detection module chooses to use three normally-open temperature control switches with different operating temperatures(60°C,90°C,and 120°C)to realize the multi-level early warning function of the system.The fire early warning controller consists of an early warning unit and a relay unit.The core is the STM8 ultra-low-powermicrocontroller(MCU).The early warning signal transmission module uses the SX1278 LoRa communication module and the GPRS module.The alarm unit power supply adopts lithium thionyl chloride disposable battery power supply,and the emergency backup power adopts a thermoelectric generator to ensure the reliability of power supply.The relay unit adopts the main and standby power supply modes,that is,220 V AC power(main power supply)and 12 V lead-acid battery.(backup power).4.Feasibility verification experiment for fire extinguishing system and warning system.The experimental results of the fire extinguishing system feasibility show that: the greater the amount of fire extinguishing agent,the better the fire-extinguishing effect,120 g aerosol fire extinguishing agent has the best fire extinguishing effect;the pipe network type discharge is relatively direct fire extinguishing,and the extinguishing time is also better.It is greatly shortened;the effect of fire extinguishing is affected by different opening methods of the cover.The upper cover does not open and the next fire is the easiest to extinguish.The cover is fully opened and the fire is most difficult to extinguish.Therefore,the fire extinguishing device using 120 g of hot aerosol fire extinguishing agent and 20 g of ultrafine dry powder fire extinguishing agent has the best effect in the pipe network spray mode.The feasibility experiment of the early warning system shows that three different temperature temperature(60℃、90℃、120℃)control switches can successfully send a sound and light alarm signal in the relay unit when reaching their operating temperature,and find that the average response time is within 1 s.