Flame retardant cable and fire-resistant cable structure, characteristics and use under what circumstances ZR cable? Under what circumstances is NH cable used? What is the difference in application? In recent years, in the global power system fire accident, the proportion of the power system power supply interruption due to the ignition of the Power Cable has increased. Therefore, fire-retardant cables are used to prevent the spread of fire in power plants and substations where there are a large number of electrical equipment and a large number of cables are densely laid. It is increasingly important to use fire-resistant cables to ensure the uninterrupted supply of important circuits. Some electrical designers have poorly understood the concepts of flame-retardant cables and fire-resistant cables. They do not understand the structure and characteristics of the two. As a result, they cannot properly design and use these two types of cables according to the power supply requirements. They can design agents or supervise them on site. It is impossible to properly guide the installation of these two types of cables during work. Therefore, a complete and correct understanding of flame-retardant and fire-resistant cables is the primary condition for their proper selection.
1. Flame-retardant cable Flame-retardant cable means that, under the specified test conditions, the sample is burned. After the test fire source is removed, the spread of the flame is only within a limited range. The residual flame or residual light can self-extinguish within a limited time. Cable. Its basic characteristics are: in the event of a fire, it may be burned out and cannot be operated, but it can prevent the spread of fire. In layman's terms, if the cable is misfiring, it can limit the burning to a local area, and it will not cause any sprawl, keep other equipment, and avoid causing greater losses.
1.1 Structural characteristics of flame-retardant cables The structure of flame-retardant cables is basically the same as that of ordinary cables, except that the insulating layer, sheath, outer sheath, and auxiliary materials (bags and fillers) are all or partially flame-retarded. material.
1.2 Classification of Flame-retardant Cables According to the different flame-retardant materials of cables, flame-retardant cables are classified into halogen-containing flame-retardant cables and halogen-free low-smoke flame-retardant cables.
The halogen-containing flame-retardant cable's insulation layer, sheath, outer sheath, and auxiliary materials (bags and filling) are all or part of halogen-containing polyethylene (PVC) flame-retardant materials, and therefore have good flame-retardant properties. However, when the cable is burned, a large amount of smoke and halogen acid gas will be released. The halogen acid gas will cause corrosive damage to the surrounding electrical equipment. Rescue workers must wear gas masks to get close to the site to extinguish the fire. When the cable is burned, it will cause damage to the surrounding electrical equipment and rescue workers, which is not conducive to the fire-fighting and rescue work, resulting in serious "secondary hazards." The halogen-free low-smoke flame-retardant cable has all or part of the insulating layer, sheath, outer sheath, and auxiliary materials (bags and fillers) made of halogen-free cross-linked polyethylene (XLPE) flame retardant material. Better flame-retardant characteristics, and no halogen acid gas is emitted when the cable is burned, and the amount of smoke emitted from the cable is also small. The corrosive gas produced by the cable combustion is also compromised between the flame retardance of the cable and the decrease of the generation of halogen acid gas. A low-halogen low-smoke flame-retardant cable was developed. Its halogen content is about 1/3 of halogen-containing flame retardant cables. The amount of smoke is also close to the recognized "low smoke" level.
According to the "Wire and Cable Burning Test Method," the flame retardant cables evaluated by the bundled combustion test method are classified into categories A, B, and C3. Among them, the test conditions of the Type A cable are the most demanding and the performance is better than that of the Type B and C. It is also the most expensive. In order to realize the flame-retardant of the cable or improve the flame-retardant level of the cable, people developed and developed a new type of so-called “oxygen-insulating layer†or “fire-resisting layer†as a fire-retardant or flame-retardant wrapping (fire-resisting layer). Structure of flame-retardant cable, and this cable is called "oxygen (fire) layer" cable. The main principle is to add metal hydrates to the materials, and to achieve low-halogen, low-smoke, low-smoke, low-smoke and cable flame retardant. However, the so-called "oxygen barrier" and "fire barrier" are just a means to achieve flame retardancy of the cable. In the end, it is still a kind of flame-retardant cable, and the highest flame retardant level it can achieve is also Class A. Therefore, the flame-retardant cable cannot be called an "oxygen barrier" cable, but only the "oxygen barrier" cable is a flame-retardant cable.
1.3 Issues for attention when selecting the design The designer should design and apply the flame retardant cable according to the specific characteristics of the flame-retardant cable, and pay attention to the following issues:
(1) As the halogen-containing flame-retardant cables (including flame-retardant cables and low-halogen low-smoke flame-retardant cables) will emit corrosive halogen acid gases when they are burned, which greatly impedes the firefighting work, delays the time for firefighting and exacerbates the spread of fire. In low-density public places, halogen-free low-smoke and flame-retardant cables should be designed and used as much as possible. Any kind of flame retardant cable can be used in the work area with a small population density.
(2) Flame-retardant cables are classified into categories A, B, and C3. Among them, the performance of category A flame-retardant cables is better than that of categories B and C, and the price is also the most expensive. Designers should indicate the type of flame-retardant cable when ordering.
(3) From the appearance, it is impossible to distinguish the category A, B, and C of the flame-retardant cable, and it is only by the manufacturer to guarantee the supply. Therefore, the cable manufacturer should be carefully selected when designing.
(4) Halogen-free and low-smoke flame-retardant cables have the advantages of low corrosion and low smoke compared with halogen-containing flame-retardant cables, but their electrical and mechanical properties are significantly reduced. Therefore, halogen-free low-smoke flame retardant is used during cable laying. The cable should have a larger bending radius than the halogen-containing flame-retardant cable.
(5) In the cable laying design, the non-flame-retardant cables and the flame-retardant cables should not be laid side by side, and the flame-retardant cables with different flame-retardant types should not be laid side by side.
2. Fire-resistant cable series Fire-resistant cable means that under the specified test conditions, the sample is burned in the flame and the performance of normal operation can still be maintained within a certain period of time. Its fundamental characteristic is that the cable can still maintain the normal operation of the line for a period of time under the burning conditions. In layman's terms, in the event of a fire, the cable will not burn at once and the circuit will be safer. Therefore, the main difference between the fire-resistant cable and the flame-retardant cable is that the fire-resistant cable can maintain the normal power supply for a period of time when the fire occurs, and the flame-retardant cable does not have this characteristic. This characteristic determines that the fire-resistant cable plays an important role in modern cities and industrial buildings, because once the fire occurs, the power supply circuits of the system such as control, monitoring, guidance, and alarming must maintain normal operation. Therefore, the cable is mainly used in emergency power supply to the user of fire-fighting equipment, fire alarm equipment, ventilation smoke exhaust equipment, guided lights, emergency power outlets, emergency elevators and other power supply circuits.
2.1 Structural characteristics of fire-resistant cables The structure of fire-resistant cables is basically the same as that of ordinary cables. The difference is that the conductors of fire-resistant cables are made of copper conductors with good fire resistance (melting point of copper is 1 083°C), and they are between conductors and insulation layers. Increase the refractory layer. The refractory layer is wrapped by multi-layer mica tape. Because the allowable working temperature of different mica tapes varies greatly, the key to the fire resistance of cables is the mica tape.
2.2 Classification of fire-resistant cables In China, ordinary fire-resistant cables are classified into Category A and Category B: Category B cables can withstand fire for at least 90 minutes in a flame at 750°C to 800°C and at a rated voltage and the cable is not broken down (ie 3A fuse is not blown). On the basis of improving the manufacturing process of the fire-retardant layer and increasing the refractory layer, a Class A fire-retardant cable was also developed. It can withstand the fire for at least 90 minutes and the cable is not broken down in the flame at 950°C to 1 000°C and at the rated voltage. (ie 3A fuse is not blown). Class A fire-resistant cables have better fire resistance than Class B. In addition, the Mineral Insulated Cable is a kind of excellent performance in the fire-resistant cable. It is made of copper core, copper sheath, and magnesium oxide insulating material, and is abbreviated as MI (minerl insulated cables) cable. The cable is entirely composed of inorganic materials, and the refractory layer of ordinary fire-resistant cables is composed of inorganic materials and common organic compounds. Therefore, the MI cable has better fire resistance than ordinary fire-resistant cables and does not decompose due to combustion. gas. MI cable has good fire resistance and can work under high temperature of 250°C for a long time. It also has explosion-proof, strong corrosion resistance, large current carrying capacity, radiation resistance, high mechanical strength, small size, light weight, long service life, and no smoke. specialty. However, the price is expensive, the process is complicated, and the construction is difficult. In the oil-filled areas, important wooden structure public buildings, high-temperature places and other fire-resistant requirements and economical acceptable conditions, this kind of fire-resistant cable can be used.
2.3 Issues to be taken into consideration for use When selecting the design of a fire-retardant cable, designers should pay attention to the following issues:
(1) When fire-resistant cables are used in cable-dense cable tunnels, cable jackets, or in flammable places such as oil pipes and oil depots, Class A fire-resistant cables should be used first. In addition to the above cases and when the number of cable configurations is small, Class B fire-resistant cables may be used.
(2) Fire-resistant cables are mostly used as power supply circuits for emergency power supplies and require normal operation in fire. As the ambient temperature rises rapidly during a fire, in order to ensure the transmission capacity of the line and reduce the voltage drop, for a circuit with a long power supply line and strictly limiting the allowable voltage drop, the section of the fire-resistant cable should be enlarged at least one step.
(3) Fire-resistant cables cannot be used as high-temperature cables.
(4) In order to reduce the failure probability of cable joints in fire accidents, the number of joints should be minimized during installation to ensure that the line can work normally in a fire. If you need to make branch wiring, handle the joints to prevent fire.
1. Flame-retardant cable Flame-retardant cable means that, under the specified test conditions, the sample is burned. After the test fire source is removed, the spread of the flame is only within a limited range. The residual flame or residual light can self-extinguish within a limited time. Cable. Its basic characteristics are: in the event of a fire, it may be burned out and cannot be operated, but it can prevent the spread of fire. In layman's terms, if the cable is misfiring, it can limit the burning to a local area, and it will not cause any sprawl, keep other equipment, and avoid causing greater losses.
1.1 Structural characteristics of flame-retardant cables The structure of flame-retardant cables is basically the same as that of ordinary cables, except that the insulating layer, sheath, outer sheath, and auxiliary materials (bags and fillers) are all or partially flame-retarded. material.
1.2 Classification of Flame-retardant Cables According to the different flame-retardant materials of cables, flame-retardant cables are classified into halogen-containing flame-retardant cables and halogen-free low-smoke flame-retardant cables.
The halogen-containing flame-retardant cable's insulation layer, sheath, outer sheath, and auxiliary materials (bags and filling) are all or part of halogen-containing polyethylene (PVC) flame-retardant materials, and therefore have good flame-retardant properties. However, when the cable is burned, a large amount of smoke and halogen acid gas will be released. The halogen acid gas will cause corrosive damage to the surrounding electrical equipment. Rescue workers must wear gas masks to get close to the site to extinguish the fire. When the cable is burned, it will cause damage to the surrounding electrical equipment and rescue workers, which is not conducive to the fire-fighting and rescue work, resulting in serious "secondary hazards." The halogen-free low-smoke flame-retardant cable has all or part of the insulating layer, sheath, outer sheath, and auxiliary materials (bags and fillers) made of halogen-free cross-linked polyethylene (XLPE) flame retardant material. Better flame-retardant characteristics, and no halogen acid gas is emitted when the cable is burned, and the amount of smoke emitted from the cable is also small. The corrosive gas produced by the cable combustion is also compromised between the flame retardance of the cable and the decrease of the generation of halogen acid gas. A low-halogen low-smoke flame-retardant cable was developed. Its halogen content is about 1/3 of halogen-containing flame retardant cables. The amount of smoke is also close to the recognized "low smoke" level.
According to the "Wire and Cable Burning Test Method," the flame retardant cables evaluated by the bundled combustion test method are classified into categories A, B, and C3. Among them, the test conditions of the Type A cable are the most demanding and the performance is better than that of the Type B and C. It is also the most expensive. In order to realize the flame-retardant of the cable or improve the flame-retardant level of the cable, people developed and developed a new type of so-called “oxygen-insulating layer†or “fire-resisting layer†as a fire-retardant or flame-retardant wrapping (fire-resisting layer). Structure of flame-retardant cable, and this cable is called "oxygen (fire) layer" cable. The main principle is to add metal hydrates to the materials, and to achieve low-halogen, low-smoke, low-smoke, low-smoke and cable flame retardant. However, the so-called "oxygen barrier" and "fire barrier" are just a means to achieve flame retardancy of the cable. In the end, it is still a kind of flame-retardant cable, and the highest flame retardant level it can achieve is also Class A. Therefore, the flame-retardant cable cannot be called an "oxygen barrier" cable, but only the "oxygen barrier" cable is a flame-retardant cable.
1.3 Issues for attention when selecting the design The designer should design and apply the flame retardant cable according to the specific characteristics of the flame-retardant cable, and pay attention to the following issues:
(1) As the halogen-containing flame-retardant cables (including flame-retardant cables and low-halogen low-smoke flame-retardant cables) will emit corrosive halogen acid gases when they are burned, which greatly impedes the firefighting work, delays the time for firefighting and exacerbates the spread of fire. In low-density public places, halogen-free low-smoke and flame-retardant cables should be designed and used as much as possible. Any kind of flame retardant cable can be used in the work area with a small population density.
(2) Flame-retardant cables are classified into categories A, B, and C3. Among them, the performance of category A flame-retardant cables is better than that of categories B and C, and the price is also the most expensive. Designers should indicate the type of flame-retardant cable when ordering.
(3) From the appearance, it is impossible to distinguish the category A, B, and C of the flame-retardant cable, and it is only by the manufacturer to guarantee the supply. Therefore, the cable manufacturer should be carefully selected when designing.
(4) Halogen-free and low-smoke flame-retardant cables have the advantages of low corrosion and low smoke compared with halogen-containing flame-retardant cables, but their electrical and mechanical properties are significantly reduced. Therefore, halogen-free low-smoke flame retardant is used during cable laying. The cable should have a larger bending radius than the halogen-containing flame-retardant cable.
(5) In the cable laying design, the non-flame-retardant cables and the flame-retardant cables should not be laid side by side, and the flame-retardant cables with different flame-retardant types should not be laid side by side.
2. Fire-resistant cable series Fire-resistant cable means that under the specified test conditions, the sample is burned in the flame and the performance of normal operation can still be maintained within a certain period of time. Its fundamental characteristic is that the cable can still maintain the normal operation of the line for a period of time under the burning conditions. In layman's terms, in the event of a fire, the cable will not burn at once and the circuit will be safer. Therefore, the main difference between the fire-resistant cable and the flame-retardant cable is that the fire-resistant cable can maintain the normal power supply for a period of time when the fire occurs, and the flame-retardant cable does not have this characteristic. This characteristic determines that the fire-resistant cable plays an important role in modern cities and industrial buildings, because once the fire occurs, the power supply circuits of the system such as control, monitoring, guidance, and alarming must maintain normal operation. Therefore, the cable is mainly used in emergency power supply to the user of fire-fighting equipment, fire alarm equipment, ventilation smoke exhaust equipment, guided lights, emergency power outlets, emergency elevators and other power supply circuits.
2.1 Structural characteristics of fire-resistant cables The structure of fire-resistant cables is basically the same as that of ordinary cables. The difference is that the conductors of fire-resistant cables are made of copper conductors with good fire resistance (melting point of copper is 1 083°C), and they are between conductors and insulation layers. Increase the refractory layer. The refractory layer is wrapped by multi-layer mica tape. Because the allowable working temperature of different mica tapes varies greatly, the key to the fire resistance of cables is the mica tape.
2.2 Classification of fire-resistant cables In China, ordinary fire-resistant cables are classified into Category A and Category B: Category B cables can withstand fire for at least 90 minutes in a flame at 750°C to 800°C and at a rated voltage and the cable is not broken down (ie 3A fuse is not blown). On the basis of improving the manufacturing process of the fire-retardant layer and increasing the refractory layer, a Class A fire-retardant cable was also developed. It can withstand the fire for at least 90 minutes and the cable is not broken down in the flame at 950°C to 1 000°C and at the rated voltage. (ie 3A fuse is not blown). Class A fire-resistant cables have better fire resistance than Class B. In addition, the Mineral Insulated Cable is a kind of excellent performance in the fire-resistant cable. It is made of copper core, copper sheath, and magnesium oxide insulating material, and is abbreviated as MI (minerl insulated cables) cable. The cable is entirely composed of inorganic materials, and the refractory layer of ordinary fire-resistant cables is composed of inorganic materials and common organic compounds. Therefore, the MI cable has better fire resistance than ordinary fire-resistant cables and does not decompose due to combustion. gas. MI cable has good fire resistance and can work under high temperature of 250°C for a long time. It also has explosion-proof, strong corrosion resistance, large current carrying capacity, radiation resistance, high mechanical strength, small size, light weight, long service life, and no smoke. specialty. However, the price is expensive, the process is complicated, and the construction is difficult. In the oil-filled areas, important wooden structure public buildings, high-temperature places and other fire-resistant requirements and economical acceptable conditions, this kind of fire-resistant cable can be used.
2.3 Issues to be taken into consideration for use When selecting the design of a fire-retardant cable, designers should pay attention to the following issues:
(1) When fire-resistant cables are used in cable-dense cable tunnels, cable jackets, or in flammable places such as oil pipes and oil depots, Class A fire-resistant cables should be used first. In addition to the above cases and when the number of cable configurations is small, Class B fire-resistant cables may be used.
(2) Fire-resistant cables are mostly used as power supply circuits for emergency power supplies and require normal operation in fire. As the ambient temperature rises rapidly during a fire, in order to ensure the transmission capacity of the line and reduce the voltage drop, for a circuit with a long power supply line and strictly limiting the allowable voltage drop, the section of the fire-resistant cable should be enlarged at least one step.
(3) Fire-resistant cables cannot be used as high-temperature cables.
(4) In order to reduce the failure probability of cable joints in fire accidents, the number of joints should be minimized during installation to ensure that the line can work normally in a fire. If you need to make branch wiring, handle the joints to prevent fire.
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