Terminal wires always have many connection points on the electrical circuit, such as wires and wires, wires and switches, wiring pile heads of wires and electrical appliances, connection points of wires and shielding devices, etc. These joints are different from other parts of wires. At the joints, the insulation layer is stripped. If the wrapping is not well wrapped and two wires collide, it may constitute short circuit, fever or spark.
1、 It is easy to cause wire collision
Wires are generally protected by insulation. As long as the insulation is not damaged, although two wires collide, there will be no problems. Accidents caused by non-standard electrical connectors, cable connectors, and terminal connectors emerge in an endless stream. The reason is that many electrical placement constructors are always careless about the placement quality when laying wires: no sleeves are installed where insulating sleeves should be used; There is no junction box installed where the junction box should be used; It causes continuous fever at the interface when the power is on, gradually drying and charring the wooden boards around, and then burning, causing a fire alarm.
2、 It is easy to get fever due to excessive contact resistance
Difference measures shall be taken at the terminal wire joint in real time, and it is also impossible to achieve "perfect". If the contact area is smaller than the conductor cross-sectional area, it can be seen from the fact that the resistance is inversely proportional to the conductive area that the smaller the contact area of the connection point is, the greater the resistance is; The greater the resistance is, the more likely it is to have a fever. Therefore, the joint is more likely to have a fever than other parts of the conductor. If the joint quality is good, the heat generated is not large, and the heat dissipation is good, the heat will quickly spread out, and the temperature of the connection point will not rise too high to cause an accident. Otherwise, the possibility of causing an accident is great. The wire is connected in a hook shape, and the contact area of the wire is up to 1/8 of the wire's cross-sectional area, so the resistance of the connection part is 8 times that of other parts, The amount of fever is similar to 8 times, so this part is prone to accidents. In addition, under the external vibration, the hook shaped connection will also show the condition of intermittent connection, which may show electric sparks, and it is easy to cause the burning of combustibles around. Because the contact resistance of the joint is too large, it may also produce high temperature, which can discolor or even melt the metal conductor, causing the conductor insulation layer to catch fire and other materials to burn, which will become a fire accident.
3、 The connection of the wires should be kept as low as possible
The wire that is often dragged and used should be the whole wire, and there should be no connector left in the middle. For example, there should be no connector in the roof of the house.
4、 Poor placement quality
(1) If the connecting conductor is not twisted as required, or even connected by the hook method, the connection of the joint will not be firm, and it is easy to loose. There is a cotton processing plant, and the wires in the penthouse (the empty pavilion on the interlayer of the roof) also use the hook connection method once. As the mouse moves in the penthouse, it touches the connector of the wire, causing the connector to loose and generating electric sparks, causing the fire in the penthouse. The fire spread rapidly along the wire, and became a serious fire accident.
(2) Wires, switches and electrical appliances are connected through wire posts. Because of the carelessness of construction, no washers are added to the wiring posts and the gongs are not tightened, the contact resistance will also increase. For example, in a hotel, for this reason, the conductor in the distribution box will melt, and the molten bead will fall on the cardboard box below, causing a fire alarm.
(3) Copper wire and aluminum wire are not connected according to the specified method, which is often a dream in the same bed, and the contact resistance is relatively large, leading to hidden dangers.
(4) The wire core of the multi strand conductor is not twisted properly, and some of the filaments (wire cores) are warped out, forming a short circuit analogy after the collision. When a department store installed a wire socket, it did not twist the multi strand copper core wire properly. As a result, some of the copper wire warps were exposed, touching another phase wire, causing a short circuit after power on, causing a fire alarm.
(5) During construction, the joints of each phase line are not staggered, which will also cause accidents on the same section. For example, when a mobile crane is stacked in a ginning plant and the wire truck with joints is used to unload goods in the warehouse in violation of regulations, the wire joints are pulled off and the joints are short circuited between phases, generating electric sparks, causing jute burning, leading to a serious accident.
5、 Loose connector after long-term opening
Some joints are of good quality when they are placed. However, due to thermal expansion and cold contraction, or long-term vibration, the joints will become loose. For example, the electrical circuit in a bridgehead of a bridge will often produce violent vibration when vehicles cross the bridge, which will slowly loosen the joints of conductors, increase the contact resistance, and cause a fire alarm.
6、 Dust pollution
On the construction site, in the threshing plant and other open spaces, there are often soil and dust seeping into the connection points of conductors, interfering with the contact between conductors, making the connection points overheat, causing the burning of combustible objects around the threshing plant. This is why some electrical fire alarms are generated.
7、 Oxidation occurs at conductor junction
In the ecology of humid and corrosive air, it is easy to form an oxide layer on the conductor (copper oxide will appear on the copper conductor, aluminum oxide is more likely to be generated on the aluminum conductor). The conductor of this kind of oxide can be very poor. For example, in the electroplating workshop of a factory, the conductor has been corroded by acid air for a long time, and the conductor forms an oxide layer on the appearance, resulting in increased contact resistance, high temperature after power on, and in serious cases, the conductor even turns red. Fortunately, it feels real-time, Then it didn't become an accident.
