The selection requirements of fire retardant cable
1. The intensive cable
More intensive configuration cable of flame retardant, should press "into a bundle of wire and cable fire test method", and the cable is configured, needed to prevent catastrophic accidents and economic and reasonable principle, satisfies the requirement of suitable category.
(1) In the same channel, unfavorable put blame combustion and flame retardant cable joint configuration.
(2) In an external fire time domestic demand to maintain current loop and the following, exposed laying cable fire protection should be implemented or choose has the fire resistance of the cable. Such as fire, police, emergency lighting, dc power supply for the operation of breaking device and the power to save the generator emergency stop and other important loop; Computer monitoring, double double circuit relay protection, security etc and share the same channel is not isolated in one of the circuits.
2. The exposed laying cable implementation of fire protection way
Cable quantity is small, fire retardant coating available, package is added on the cable or cable to wear in the fire pipe.Flexible Cable is large, the same channel should be equipped in the fireproof trough box, and the power cable should be used ventilation type, in the absence of combustible dust environment available semi-closed, laying in the cable protection section of bridge rack is not long, also can use fire.
In oil tank area, important timberwork public buildings, and other high temperature places require high fire-resistant and installing and laying, the situation of economic performance to accept incombustible mineral insulated cable can be used. The oil-filled cable after exposed laying in the public corridor, the passenger tunnel, bridge for implementation of the fire prevention, can take sand buried laying. Near the high pressure oil equipment such as current, voltage transformer in cable trench, appropriate makes the segment trench cover seal.
3. The populated places
In the security requirements of high cable populated places or closed channels, shall be provided with suitable for environment and reliable action of the automatic fire detection alarm device. Exposed laying oil-filled cable oil supply system should be equipped with fire auto alarm and can reflect the state of the injection locking device. Underground cable densely populated parts of the public facilities, and more back into oil-filled cable terminal Settings and places of security requirement is higher, can be installed special fire control facilities such as water spray extinguishing the fire.
Cable fire both at home and abroad have occurred repeatedly, the United States in 1965 ~ 1975 of wire and cable fire, a total of more than 1000 times, direct costs hundreds of millions of dollars. A Japanese power plant 600 mw unit a cable fire, loss of $30 million; In recent 10 years in our country, there are two large chemical plant has a power supply cable fire, a burnt more than 40 kilometers electrical cable, because each blackout once all damage output 30 million power cable fire accident to occur more frequently, severe losses. According to incomplete statistics, nearly 20 years in China has appeared more than 200 cable fire, the cumulative loss of one hundred million yuan directly, affect the national economy an estimated billions of dollars more than indirect losses.
Since the 80s, China had to prevent cable fire spreading combustion method, such as scientific research, confirmed by the ministerial appraisal, including physical simulation in the series on the basis of fire test engineering conditions, to prevent secondary efficacy associated with combustion intensity, refractory effectiveness as sufficient to represent the actual assessment of possible combustion temperature and so on, obtain new knowledge. Under the fire department and so on collaborative, developed diversified flame retardant material products, cable to prevent secondary, refractory technology has remarkable progress.
2016年3月22日星期二
2016年3月7日星期一
The main factors that cause "cable blasting"
Since people found when using electric, wire and cable has become a main carrier of power transmission. Both electrical equipment, lighting and household electrical appliances all aspects without wires. Although it is only a supporting industry, but the better part of a market occupies the electrical industry. The quality of the Wire and cable will directly affect the engineering quality and the safety of the people, will also affect the development prospects of the cable.
In the process of operation, Wire and cable often will appear this or that kind of accident, especially under the condition of use of non-standard wire and cable.Cable at run time, two phase ground fault or alternate with, mostly tripping caused by system, the failure phenomenon is commonly known as - blasting. Let's talk about what are the main factors of "cable blasting".
1. The three-phase cable conductor short-circuit fault occurs between each other, or one of the relative cable sheath fault, will produce a very large quantity of heat, make the burst failure.
2. Such as the insulation layer inside the particles, impurities and air bubbles, or with external mechanical damage.
3. Check whether the cable is too very give hurt the cable bending.
4. Small bending radius, injury of external mechanical forces, dc resistance test ion release, not rated current overload.
Cable firing is in the running, cause a sudden trip systems, it is extremely adverse to the production. If we think the cable system fault, often appear blasting of cable line in the construction, operation, maintenance and management problems of the larger, should cause enough attention, after the repair work is done, should be carefully and find the reason to be eliminate, avoid shooting accident again.
In the process of operation, Wire and cable often will appear this or that kind of accident, especially under the condition of use of non-standard wire and cable.Cable at run time, two phase ground fault or alternate with, mostly tripping caused by system, the failure phenomenon is commonly known as - blasting. Let's talk about what are the main factors of "cable blasting".
1. The three-phase cable conductor short-circuit fault occurs between each other, or one of the relative cable sheath fault, will produce a very large quantity of heat, make the burst failure.
2. Such as the insulation layer inside the particles, impurities and air bubbles, or with external mechanical damage.
3. Check whether the cable is too very give hurt the cable bending.
4. Small bending radius, injury of external mechanical forces, dc resistance test ion release, not rated current overload.
Cable firing is in the running, cause a sudden trip systems, it is extremely adverse to the production. If we think the cable system fault, often appear blasting of cable line in the construction, operation, maintenance and management problems of the larger, should cause enough attention, after the repair work is done, should be carefully and find the reason to be eliminate, avoid shooting accident again.
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2016年2月24日星期三
The introduction of special wire cable
Special wire cable is a series of products with unique properties and special structure, the equivalent of ordinary wire and cable quantity bedding face is wide, with high technical content, use more strict conditions, the characteristics of small batch and high added value. Often using new materials, new structure and new technology and new design calculation.This kind of wire cable can be roughly divided into the following four categories.
A. High temperature resistant wire cable
Aerospace, vehicles, energy, steel, non-ferrous metal smelting, oil resistant to high temperature wire and cable, motor, etc. Long-term continuous working temperature of 125 degrees, 135 degrees, 150 degrees, 180 degrees, 200 degrees, 250 degrees and 250 degrees or more resistant to high temperature wire and cable, at present commonly used are radiation crosslinked polyolefin, silicone rubber, fluorine resin, polyimide, mica, magnesium wire and cable, etc.Are introduced; Two kinds of new type high temperature wire and cable, 1. Polyether sulfone insulated wire, 2. Polyether ether ketone insulated wire.
B. The purpose and structure of special wire cable
1. Low inductance cables
With heavy current and weak current, here introduces a kind of high voltage with low sense of cables. The electric cable with a heat dissipation device, used for all kinds of resistance welder, arc welder and pneumatic electrode holder connected between the new type of low water cooled cable, has simple and reasonable structure, large cooling water circulation, will not become blocked block and the limit of flow phenomenon, good heat dissipation effect, long service life, etc.
2. Low noise cable
In bending, vibration, shock, temperature change under the influence of external factors, such as pulse signals generated by the cable itself is less than 5 mv cable called low noise cable, also known as shock instrument cables. Used in industrial, medical, defense and other fields of tiny signal measurement.
C. Functional wires
1. The fluoride resin self-control steady 135 - degree heating cable
Its thermal process is different, show the conductive properties and stability of different level, this is because the matrix crystallization degree and crystal morphology is influenced by different cooling speed because of the insulation.
2. Electroluminescent wire
Electroluminescent wire is a latest product, in the field of international light-emitting display similar shape with ordinary wire and cable.
D. New type of green environmental protection wire and cable insulation
1. The CMP cable
Can pass ul flame retardant highest grade standard cable, for CMP cable. In general, is the base material of low smoke zero halogen polyolefin, it has higher fuel quantity of heat, is highly combustible, so they are mixed with filler metal hydrate, to curb its flammability, but the water of hydration, after running out can cause burning fiercely.
2. The halogen-free cable, new type of green environmental protection wires cables
A. High temperature resistant wire cable
Aerospace, vehicles, energy, steel, non-ferrous metal smelting, oil resistant to high temperature wire and cable, motor, etc. Long-term continuous working temperature of 125 degrees, 135 degrees, 150 degrees, 180 degrees, 200 degrees, 250 degrees and 250 degrees or more resistant to high temperature wire and cable, at present commonly used are radiation crosslinked polyolefin, silicone rubber, fluorine resin, polyimide, mica, magnesium wire and cable, etc.Are introduced; Two kinds of new type high temperature wire and cable, 1. Polyether sulfone insulated wire, 2. Polyether ether ketone insulated wire.
B. The purpose and structure of special wire cable
1. Low inductance cables
With heavy current and weak current, here introduces a kind of high voltage with low sense of cables. The electric cable with a heat dissipation device, used for all kinds of resistance welder, arc welder and pneumatic electrode holder connected between the new type of low water cooled cable, has simple and reasonable structure, large cooling water circulation, will not become blocked block and the limit of flow phenomenon, good heat dissipation effect, long service life, etc.
2. Low noise cable
In bending, vibration, shock, temperature change under the influence of external factors, such as pulse signals generated by the cable itself is less than 5 mv cable called low noise cable, also known as shock instrument cables. Used in industrial, medical, defense and other fields of tiny signal measurement.
C. Functional wires
1. The fluoride resin self-control steady 135 - degree heating cable
Its thermal process is different, show the conductive properties and stability of different level, this is because the matrix crystallization degree and crystal morphology is influenced by different cooling speed because of the insulation.
2. Electroluminescent wire
Electroluminescent wire is a latest product, in the field of international light-emitting display similar shape with ordinary wire and cable.
D. New type of green environmental protection wire and cable insulation
1. The CMP cable
Can pass ul flame retardant highest grade standard cable, for CMP cable. In general, is the base material of low smoke zero halogen polyolefin, it has higher fuel quantity of heat, is highly combustible, so they are mixed with filler metal hydrate, to curb its flammability, but the water of hydration, after running out can cause burning fiercely.
2. The halogen-free cable, new type of green environmental protection wires cables
2016年2月18日星期四
Influence of insulation eccentricity to cables
For rubber plastic insulated power cable, due to the reason of the manufacturing process, its surrounding the conductor insulation thickness may not be equal, namely, insulation eccentricity.
In the structure of radial electric field H cable shielding layer on the surface of the conductor insulation layer is the end point of the electric field, when the insulation thickness, the electric field for coaxial cylinder electric field. The electric field of rubber cable insulation layer distribution is uniform, that is in the same radius of insulation on the circumference of a circle of electric field intensity are equal.
When the uneven thickness of insulation and eccentric, electric field is no longer a coaxial cylinder electric field, the electric field distribution within the insulation layer is not uniform, deterioration of the electric field will be concentrated in insulating thin place, where the insulation of the thinner of the electric field intensity. Visible, insulation eccentricity for the radial electric field of the structure of the H cable, it is very harmful, when serious can cause insulation breakdown.
The current cable in the national standard GB/T 12706, demand for cable insulation layer is:
(1) the insulation thickness shall be not less than 6 average nominal thickness.
(2) the minimum insulation thickness shall be not less than 90% of the nominal value -- 0.1mm.
(3) for more than 35kv voltage grade of cable, the eccentricity (maximum thickness) divided by the difference between the maximum and minimum thickness thickness should be not greater than 15%.
In low voltage cable, is using the radial electric field structure, namely each phase no shielding layer insulation surface, such as PVC cable, etc. This cable will not because of excessive deteriorating insulation eccentricity and electric field, the insulation thickness as long as the foot against the requirements of the former two.
In the structure of radial electric field H cable shielding layer on the surface of the conductor insulation layer is the end point of the electric field, when the insulation thickness, the electric field for coaxial cylinder electric field. The electric field of rubber cable insulation layer distribution is uniform, that is in the same radius of insulation on the circumference of a circle of electric field intensity are equal.
When the uneven thickness of insulation and eccentric, electric field is no longer a coaxial cylinder electric field, the electric field distribution within the insulation layer is not uniform, deterioration of the electric field will be concentrated in insulating thin place, where the insulation of the thinner of the electric field intensity. Visible, insulation eccentricity for the radial electric field of the structure of the H cable, it is very harmful, when serious can cause insulation breakdown.
The current cable in the national standard GB/T 12706, demand for cable insulation layer is:
(1) the insulation thickness shall be not less than 6 average nominal thickness.
(2) the minimum insulation thickness shall be not less than 90% of the nominal value -- 0.1mm.
(3) for more than 35kv voltage grade of cable, the eccentricity (maximum thickness) divided by the difference between the maximum and minimum thickness thickness should be not greater than 15%.
In low voltage cable, is using the radial electric field structure, namely each phase no shielding layer insulation surface, such as PVC cable, etc. This cable will not because of excessive deteriorating insulation eccentricity and electric field, the insulation thickness as long as the foot against the requirements of the former two.
2016年1月5日星期二
Repair methods of Power cable fault
Maintenance countermeasures
In view of the power cable to the above several types of fault, can develop countermeasures according to the reality.
To the middle connector and terminal head of production process, can strengthen the net cable head attachment test, on the basis of the relevant provisions, strictly controlled; Stripping sheath, insulation shield semiconductor layer careful operation, carried out on the insulation surface grinding and clean thoroughly, prevent the impurity particles legacy on the insulation; Installation environment humidity below 70%.
Make a series of specific provision on cable installation: armoured layer and copper shield must be separate grounding, and its cross section is not less than 25 square millimeter; Single core cable must be affected by one-point earthing electricity end, three core cable ends must be grounded, at the same time to the cable nose do tin plating processing.
In order to prevent the cable from external force damage, can do it for mechanical parts wear tube and protection to be fixed, the middle joint external protection, on both sides of the joint plus fixed protection; In the process of construction, ensure no external force to line the nasal twist deformation, if must do twisting process, measures should be taken to make the surface smooth;Near the cable construction team, to increase the smart card, send someone remind construction personnel when necessary.
Cut joint: before cut, first to check whether there is water inside the joint and moisture, if any, cannot use cut torch connector, because the burner heating makes moisture from joint on both sides of the inside to the cable, it is better to hammer and rationalism knife cut casing; If there is no moisture and moisture, usable burner to lead a very hot, in addition to the lead of dirt, scrape rusty spot, wipe the soldering tin slag, away from the flexible power cable joint, for reuse.
Remove moisture, baking method available. It is with a torch or charcoal fire roasted, expelling dampness. This method can only be used for a small amount of moisture. When the paper insulated conductor by moisture, can use casting wax, to remove the moisture with hot wax. Ash from 60% and 40% of medium-sized vaseline blend to heat up to 130-140 degrees which, when casting wax control in 120-130 degrees, water the wax from the two side lead sheath incision 10 to 15cm in lead sheath, gradually to move water cut, and after condensation of wax material again to slit to the joint central casting, until no air bubbles on core and the voice of the impregnation.
In view of the power cable to the above several types of fault, can develop countermeasures according to the reality.
To the middle connector and terminal head of production process, can strengthen the net cable head attachment test, on the basis of the relevant provisions, strictly controlled; Stripping sheath, insulation shield semiconductor layer careful operation, carried out on the insulation surface grinding and clean thoroughly, prevent the impurity particles legacy on the insulation; Installation environment humidity below 70%.
Make a series of specific provision on cable installation: armoured layer and copper shield must be separate grounding, and its cross section is not less than 25 square millimeter; Single core cable must be affected by one-point earthing electricity end, three core cable ends must be grounded, at the same time to the cable nose do tin plating processing.
In order to prevent the cable from external force damage, can do it for mechanical parts wear tube and protection to be fixed, the middle joint external protection, on both sides of the joint plus fixed protection; In the process of construction, ensure no external force to line the nasal twist deformation, if must do twisting process, measures should be taken to make the surface smooth;Near the cable construction team, to increase the smart card, send someone remind construction personnel when necessary.
Cut joint: before cut, first to check whether there is water inside the joint and moisture, if any, cannot use cut torch connector, because the burner heating makes moisture from joint on both sides of the inside to the cable, it is better to hammer and rationalism knife cut casing; If there is no moisture and moisture, usable burner to lead a very hot, in addition to the lead of dirt, scrape rusty spot, wipe the soldering tin slag, away from the flexible power cable joint, for reuse.
Remove moisture, baking method available. It is with a torch or charcoal fire roasted, expelling dampness. This method can only be used for a small amount of moisture. When the paper insulated conductor by moisture, can use casting wax, to remove the moisture with hot wax. Ash from 60% and 40% of medium-sized vaseline blend to heat up to 130-140 degrees which, when casting wax control in 120-130 degrees, water the wax from the two side lead sheath incision 10 to 15cm in lead sheath, gradually to move water cut, and after condensation of wax material again to slit to the joint central casting, until no air bubbles on core and the voice of the impregnation.
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