Analysis on the fireproof effect of cables

What should I do if the cable’s fire protection effect is not good? Try mineral insulated cables!
Is the cable’s fireproof effect poor? Have you tried mineral insulated fireproof cables! Mineral insulated fireproof cables not only have the characteristics of fire resistance, high temperature resistance and corrosion resistance, but also good waterproof effect, light weight and long life.
(1) In order to prevent electrical fires caused by the quality of the wires and cables themselves, qualified wires and cables must be selected;
(2) The aluminum conductor joints are prone to temperature rise and poor contact due to oxidation. Therefore, copper core wires and cables should be selected as a priority to reduce fire hazards.
(3) For cross-linked polyethylene insulated wires and cables, its electrical and physical properties are better than other wires and cables. It has the advantages of long life, good water resistance, good corrosion resistance, and less harmful combustion products, so it is insulated with polyethylene. Wire and cable (YJV) can be used as a priority;

(4) Because flame-retardant wires and cables can effectively slow down or even prevent the expansion and spread of fire, the use of flame-retardant wires and cables can control the fire at the initial stage of the fire to avoid greater losses, so flame-retardant wires and cables should be selected;
(5) In order to ensure that the electrical circuits can be energized normally during a period of fire, fire-resistant wires and cables should be selected;
(6) Try to use halogen-free low-smoke flame-retardant wire and cable or low-halogen low-smoke flame-retardant wire and cable to avoid generating a large amount of smoke and corrosive gas;


(7) On the one hand, mineral insulated cables provide excellent low grounding resistance and save a grounding wire than other cables. On the other hand, they can effectively ensure the safe operation of workers; for fire-fighting electrical equipment, it should be preferred Mineral insulated fire-resistant cable

Precautions for choosing household powercable

In home decoration, water and electricity decoration is the most important, especially the electrical part, because it involves the safety of electricity use. If there is a problem with the electrical decoration, it may directly affect the safety of the family and the consequences are quite serious. Therefore, whether it is the wiring, connection, or purchase of PE Cable, there must be reasonable planning and prior understanding.
At present, there are two types of wires for household use on the market, single-core and multi-core. Single-core wire means that the internal conductor is a relatively thick copper core, and the multi-core wire is twisted together by multiple thin copper cores. In comparison, single-core wires have higher hardness, and multi-core wires are softer, and their advantages and disadvantages are also obvious. You need to choose according to your own needs.


220V alternating current is used in the family, whether it is a single-core wire or a multi-core cable, as long as the qualified product is suitable for working under such conditions, the performance of the single-core wire will be more stable and the surface area It is small, not easy to be oxidized, and has higher mechanical strength. Multi-core cables are more flexible and easier to pull and bend, which is more convenient in the installation process, and it is not easy to damage the wires. In terms of price, the price of a single core is slightly cheaper, so when considering whether to use a single core or a multi-core wire, you need to choose according to your own needs and the characteristics of the wire.


In addition, when choosingSingle core cable, the most important thing is to see whether it meets the national standard. It cannot be a shoddy non-standard product. There are manufacturers, specifications, wire diameters, certification marks, and anti-counterfeiting queries on the wires. As for the amount of wire to choose at home, it should be determined according to the number and requirements of electrical appliances in the home. Generally speaking, the light wire uses 1.5 square wire, the socket uses 2.5 square wire. There are more electrical appliances in the kitchen and bathroom, and the power is large. It is best to use 4 square wires, vertical air conditioners use 4 square wires, and central air conditioners use 6 square line.

Development of high flexible fireproof cable

With the development of society, the scale of the city has been expanding, high-rise buildings have been emerging, and the number of important buildings has been increasing. The fire caused by the electric line, especially the huge fire accident, endangers the safety of life and property, and some fatal and huge fire, often causes a series of social problems and accountability. Once the fire happens, rescue is very important, fire pump, fire smoke exhaust, emergency lighting, fire elevator and other rescue equipment become the protection of people's escape, and these protection "lifeline" is the fire-proof cable. Due to the frequent occurrence and serious consequences of fire, more and more attention has been paid to the performance and testing of fire-resistant cables. Table 1 gives examples of the structure and standard test conditions of fire-resistant cables in some countries and regions, from Table 1, we can see the different requirements of GB, IEC, BS, AS for the test performance of fire-proof cable. China fire-resistant cables mainly implement the national standards, fire resistance requirements through BS 6387 or BS8491 fire-resistant + vibration + spray fire test.

At present, the fire-proof cables on the market are mainly divided into two categories from insulating materials, namely, magnesium oxide insulated fire-proof cables and mica-mineral compound insulated fire-proof cables, the common custom is respectively called the rigid fireproof cable and the flexible fireproof cable. Because of the difference of structure design and material technology, the two kinds of cables have their own characteristics and need to be improved. As a rigid fireproof cable, it has many advantages, such as high temperature resistance, radiation resistance, long life and good earthing, etc. . The other category is flexible fireproof cable with twisted conductor + mineral composite insulation + Metal Sheath or fireproof mud composite sheath, theoretically speaking, tubular metal or metal sheathed fireproof cable after mechanical deformation through rolling, the flexibility is mainly relative to solid conductors, and the flexibility of fireproof cables with fireproof mud insulation is limited by the hardness of the fireproof mud. Compared with conventional cables, these fireproof cables need special accessories and technology in connection, and it is more difficult to realize pre-branching. Their branch joints are often connected by branch boxes, except for complicated installation, construction strength, fire performance, joint performance and sealing moisture performance is also uneven.

We study the structure and material of the fireproof cable deeply, and take the flexibility, fireproof safety and construction convenience as the research direction, develop a kind of flexible fireproof cable, it has passed GB, IEC, BS and AS tests, and is a kind of truly flexible fireproof cable. On this basis, we developed the prefabricated branch type environmental protection fireproof cable. This prefabricated branch type fireproof cable has low manufacturing cost and not only retains the advantages of the traditional fireproof cable, the utility model also overcomes the problems of moisture absorption of the fire-proof layer of the general fire-proof cable and the poor flexibility of the cable, and is convenient to install and lay.

Is it better to buy ACSR Cable online or in physical stores?

I don’t know whether to buy ASTM 477 MCM ACSR Cable online or in physical stores. It mainly depends on which part of the demand you need to meet. For users with higher quality requirements, you can buy them in physical stores. After all, you can get in touch with the real thing. , Specifications, voltage, etc. to prevent errors.


Those users who are more price sensitive can order directly online; the advantage of online purchase is that the price is much cheaper than offline, because it can save the cost of site rent increase and other costs, especially the one-stop supply of ACSR Cable online. Manufacturers have special supply channels and direct sales at factory prices, which is very cost-effective.


For users who are unsure about the quality of the wire purchased online, this is actually unnecessary. We can identify the quality of the product through the sample map. Users in the same city can also directly check the production workshop; and the manufacturer has spent so much money to make the website online, it is not necessary For the sake of a single order, the previous efforts have been broken, so it is still very reliable to place an order online, provided that you must look for a more formal wire and cable website.
Yu Zheng is entangled in whether the cable is bought online or bought in a physical store. Jinhaotai suggests that you can first consult the product price online, then go to the physical store to check the quality in the same city, and then decide where to buy. After all, the advantages of online and physical stores have their own advantages.

Cable Broken Core Detection Method

The broken core fault point has the following methods to detect:

1.1. Induction method
It can be used with induction pen and digital multimeter; suitable for cables without metal armor and steel tape shielding; attention should be paid to prevent electric shock, the test place and the terminal connection when the equipment is rewinded.

specific methods:
1) Hang the conductor core of the cable in the air, and ensure that it will not cause road and electric shock accidents; at the same time, ensure that the cable is as far away as possible from the grounding body (such as the ground, equipment, etc.);
2) Select a good insulation core in the cable, connect the 220VAC phase wire (live wire), not the ground wire;
3) If you use an induction pen, touch your finger to the induction contact on the pen, and test whether the pen is normal outside the insulating layer of the charged body. If you use a digital multimeter, put the multimeter in the 20 or 200mV range, put a thinner plastic insulating sleeve on the red test lead, and hold the black test lead with your hand; test it outside the insulating layer of the clearly charged body, and take the reading; then remove it The charged body is far away, and read; compare the difference between the two readings, usually on the charged body, there should be a higher reading, such as 0.4mV, while the farther away from the charged body is lower, such as 0.15mV; remember this feature, you can Start testing.
4) Test close to the cable along the cable. When the indicator light of the induction pen is dimmed or the reading of the multimeter drops significantly, the change is the breakpoint.
5) The test is completed, pay attention to discharge!  

 

1.2. Capacitance method

When there is a metal armor layer such as copper or steel tape armored cable outside the cable, the induction method cannot be used for detection. At this time, the capacitance method is used; it is suitable for all cables; when using the capacitance method, first understand the principle of capacitance testing-when testing capacitance, The AC/pulse signal is used in the test loop, that is, measuring the AC partial voltage or charging and discharging the capacitor (two mutually insulated metal poles) to test the accumulated electricity on the capacitor and convert it to the reading of the capacitance.

Capacitance method may affect the accuracy due to the inductance formed by winding the cable into a circle, the insulating cores being wound together, the resistance of improper conductors (such as steel strips), and the stray capacitance between conductors; among them The inductance is very small and can be ignored; the resistance has little effect on the measured capacitance, but the difference in capacitance between the bare conductor and the steel strip and the unconnected capacitance is not big, and it can be ignored; but the stray capacitance has a greater impact, so I did an experiment : The capacitance between the intact core and the steel strip is 117nF. Connect the other cores to the steel strip. The measured result is still 117nF, while there is 72nF between the two cores.

For the convenience of description, suppose the cable is a 2-core steel tape armored cable with 1 core with 1 break point; the specific methods are as follows:

1) Hang all insulated cable core conductors and armor layers at both ends of the cable;
2) Measure the capacitance value of the intact insulating core and the broken core insulating core to the steel strip (or the third intact insulating core) at both ends, and record the value; at this time, the corresponding intact insulating core is measured at both ends The capacitance value should be very close; the sum of the capacitance value at both ends of the same broken core should be slightly greater than the capacitance value of the intact insulated core at the same position, it means there is only one breakpoint, or multiple breakpoints but very close; if both ends of the same broken core The sum of the capacitance values ​​is less than the capacitance value of the intact insulating core at the same position, indicating that there are at least two breakpoints;
Note: Theoretically, if there is only one breakpoint or multiple breakpoints but very close, the sum of the capacitance values ​​at both ends should be greater than the capacitance value of the intact insulating core at the same position. The amount varies with different cables. See the following theoretical analysis.
3) Compare and calculate the capacitance value of the broken core insulation core and the intact insulation core, and obtain the lengths of the two ends respectively. At this time, the length may be different from the actual length. The next step is to re-calibrate; but the two-core unarmored cable cannot be Make corrections.
4) If the sum of the calculated length is greater than the actual length, the extra length will be negative, and if it is less than the actual length, it will be positive; then use the capacitance value of the broken core insulating core to allocate the difference and divide the long segment to correct the long segment , The short segment is corrected for the short segment (see the following theoretical analysis), and the actual position of the breakpoint is obtained.