Cables and electrical equipment such as high-temperature tunnel furnaces and other fire prevention issues are very important in the design of power plants abroad. First of all, in cable selection, flame-retardant cables are usually used, and electrical equipment is generally closed. This will prevent the fire from spreading if it catches fire. Electrical equipment such as high and low voltage power distribution devices and relay rooms, etc., 1301 fire extinguishing materials are commonly used, smoke or temperature sensitive elements are used for alarm, and automatic spray fire extinguishing is used. And the places where the cables are dense in the factory building are generally equipped with smoke or temperature sensitive components. Once the cable catches fire, there is a fire alarm device in the control room and the fire protection facilities are automatically started. Use water spray to extinguish fire. It is more reliable to lay the Yamin cable at the same time according to the cable routing path. Obviously, these measures are relatively expensive. Some countries also use cables to lay pipes in order to ensure that the cables are laid in the pipes accordingly, but a large amount of steel must be consumed.
Over the years, there has not been a set of practical and effective fire prevention methods: in the past, the cable fire prevention measures were relatively simple, and most of them only adopted fire doors in the tunnel. Once the cable in the tunnel catches fire, it is isolated by fire doors to prevent the fire from spreading and reduce losses. Since the contradiction between fire door and ventilation is not easy to solve, although the fire door is considered in the design, it is generally difficult to close the door for ventilation during operation, and the fire door is often in the open position during operation. Once a section of the tunnel catches fire, It is too late to close the fire door, in fact, the fire door can not play the role of fire and flame retardant, and some engineering fire doors are not installed at all. High-temperature tunnel furnaces, especially the cables laid overhead in the main factory building, have a high ignition rate, a large number of cables, and no good fire protection facilities. Therefore, there is no good countermeasure for cable fire prevention. Once the overhead cables catch fire, due to the difficulty in extinguishing the fire, Often the damage is serious and the repair is difficult, so cable fire prevention cannot be ignored for power plants.
Analysis of Causes of Cable Fires Over the years, high-temperature tunnel furnace cables in power plants have suffered multiple fire accidents and prolonged fires, causing serious losses. According to survey data, in power plant fire accidents, about 25% of the fire caused by the high temperature tunnel furnace cable itself caused fires to spread.
Fire accident caused by high temperature tunnel furnace cable failure. High temperature tunnel furnace is mainly water and ash accumulation in the cable structure, which makes the cable immersed in water for a long time, causing the cable insulation to decline, aging, and the sheath to rot; due to the insulation being seriously wet, the breakdown is short . In addition, fire accidents caused by cable head explosions. No matter what causes the fire, it has the characteristics of flammability, difficulty in extinguishing fire and large loss.
Followed by the external fire source caused the cable to catch fire. According to the analysis of external factors, there are the following main aspects:
1. Due to oil leakage or oil pipe rupture in the oil system of the steam turbine, the pressure oil sprayed on the high-temperature pipeline with insufficient insulation caused a fire, and the nearby cables were ignited and spread, causing a fire.
2. The explosion-proof door of the boiler's pulverizing system exploded, and the flames rushed to the nearby cables, causing the cables to catch fire or spontaneous combustion of coal powder accumulated by the high-temperature equipment of the boiler, causing the nearby cables to catch fire and spread into disaster.
3. The oil-immersed electrical equipment exploded and ignited the fire. The flame flowed into the cable trench with the oil and caused the cable to catch fire.