Discussion on fire protection design scheme of the

Discussion on the fire prevention design scheme of 35kV miniaturized substation

fire prevention of small and medium-sized substations in rural reconstruction has always been a difficult point, because the rigid provisions of the national fire protection regulations force the power industry to implement them, but what scheme to choose is more suitable for small substations in the power system, which is the discussion center of this article

according to the author's observation in recent years and relevant domestic technical data statistics, the areas where fire may occur in the substation are:

(1) oil filled electrical equipment, such as transformers, outdoor multi oil switches

(2) cables in cable trench

(3) relay protection equipment in the control room (mainly electromagnetic equipment, storage battery and 10kV, 35kV transformer explosion)

main causes of fire:

(1) fire caused by transformer due to inter turn short circuit, poor wiring of tap changer, etc

(2) fire caused by overheating due to poor contact of multi oil circuit breaker

(3) fire caused by cable passing short-circuit current and poor heat dissipation and sealing

(4) voltage transformer resonance causes explosion

(5) fire caused by equipment in the control room through short-circuit current

(6) poor ventilation of the battery pack causes an explosion caused by high concentration of flammable gas

to sum up, we can find a rule that most of the fires in the power system come from the interior of the equipment. The fire extinguishing schemes recommended in the regulations include: sand, oil storage tank, chemical extinguishing agent, water mist fire extinguishing system, etc. Their advantages and disadvantages are as follows: ① sand basin: cheap, no maintenance. However, the fire extinguishing capacity is the worst, causing secondary pollution. ② Chemical extinguishing agent: it is cheap, flexible to use and has little pollution. But the fire extinguishing capacity is poor. ③ Water mist fire extinguishing system: it has strong fire extinguishing capacity, but the investment is large. Based on the study of the code, the author's consideration of the fire protection design can be summarized as follows:

(1) most of the electrical fires in the substation are caused by electrical equipment, especially the equipment with oil. If sandy soil is used for dumping, it will lead to serious pollution of the equipment, which will bring great difficulties to the equipment repair after the accident. It is estimated that 3000 tons of industrial grade lithium carbonate will be recovered, and this method has little effect on fire fighting. The specification recommends the use of wheeled or portable chemical fire extinguishers with high fire extinguishing performance for oil fires, such as dry powder and 1211. Such extinguishers are allowed to be stored for a long time, require less frequent inspection and maintenance, save initial investment, and are flexible and convenient to use. There is no need for professional fire brigade. It is possible to extinguish the initial fire before the professional fire brigade arrives

(2) for rooms with important instruments and meters on fire, it is not suitable to use foam or carbon dioxide fire extinguishers with high profits, nor water fire fighting, nor sandy soil, because such facilities will stain or damage the instruments and equipment that are not on fire. The fire extinguishers recommended in the specification will not cause pollution. Gas fire extinguishers mainly refer to halon fire extinguishers, of which 1211 is relatively cheap

(3) the fire accident barrier of the cable is relatively high, but the cable is widely distributed. If fixed fire extinguishing facilities are used everywhere, it is too uneconomical and unrealistic. In order to prevent the cable fire from spreading to the main buildings and various equipment, the scope of the accident should be minimized and the repair time should be shortened accordingly. The main measures recommended in the specification are separation and flame retardation, such as blocking all the gaps of the cable entry in the main control room with fire-proof materials such as fire-proof mastic, Practice has proved that it can prevent the cable from leading the fire into the main building. China's scientific research institutions may have mastered the relevant technology. The purpose of flame retardant measures is to separate. For example, the cable between the main control room and the cable interlayer can be blocked by coating the fire-proof coating within 1m above and below the floor. Of course, if it is used together with the fire-proof mastic to fill the holes, the effect will be better. The longer cable trench or cable tunnel, Similar segmented flame retardant measures can also be adopted

(4) fire fighting countermeasures for oil immersed transformers. The basic countermeasures for standardizing the initial fire of this kind of transformer are to try to put out or suppress the fire with chemical fire extinguishers. For serious fires caused by internal faults, it depends on fire prevention distance (or fire partition), accident oil drainage facilities and chemical fire extinguishers to effectively prevent the expansion and spread of the fire

35kv ~ 110kV substations have a large number and a wide range. According to the statistics of relevant parts, more than 3000 substations are planned to be put into operation in the next five years. If the specifications require the installation of transformer water mist fire extinguishing system generally, it will lead to an increase of more than 300million yuan in infrastructure investment in the next five years, while the use of chemical fire extinguishers will only increase by 30million yuan. In addition, according to the operation part, the pipelines, valves and sprinklers of the water mist fire extinguishing system installed outdoors are headquartered in parccorp., Romeville, Illinois, USA The new business direction is being promoted, and the preservative, antifreeze, dust prevention, debris prevention of the pool and the system spray test once or twice a year are all practical problems that are difficult to deal with in operation

finally, I think that for the fire prevention scheme of small-scale substation, it is not suitable to set up sand basins, oil storage wells and other civil facilities, but the first scheme is as follows:

(1) set a reasonable fire separation or firewall according to the requirements of the specification, and set up wheeled fire extinguishers to suppress the fire at the initial stage, and use the fire separation or firewall to prevent the spread of the fire

(2) for the fire prevention of cables in cable trench, fire-proof materials such as fire-proof mastic shall be used to block all gaps at the cable entrance of the main control room, and 1m wide fire-proof coating shall be applied on the cable every 1m, blocking by sections

(3) for the fire prevention of indoor electrical equipment, use gas fire extinguishers

(4) fire hydrants are used for all conditions of large capacity substation