Why does the copper wire of the cable and wire become black?

(1) The area of the drawing emulsification oil pool is small, the return pipeline is short and sealed, resulting in slow heat dissipation and high temperature of the emulsified oil.

(2) It is caused by the annealing of the copper wire. First, the cooling water used in the continuous retreat is generally tap water and groundwater. Since the water quality varies from place to place, the PH value of the water quality in some areas is low, only 5.5~5.0 (normally 7.0~7.5). The anti-oxidation oil film has been cleaned off, and the annealed copper wire is easy to oxidize and turn black; the second is to anneal the finished copper wire drawn by the ordinary wire drawing machine on another annealing line, and the cooling water does not use antioxidants, and the anti-oxidation time Short, the phenomenon of oxidation blackening will appear soon;

(3) Some old factories still use annealing cylinders for annealing. The following reasons can also cause oxidation and blackening: First, the annealing cylinder nut is not tightened, and air leaks after carbon dioxide or high-purity nitrogen is flushed; second, the cylinder is discharged When the temperature of the copper wire is too high, exceeding 30 °C; the third is that the maintenance of the drawing emulsion is not enough, and the PH value is too low; these situations are more common when the temperature is high in summer, and the emulsion will be lost if it is used continuously, and when the temperature is high, it will be lost. Faster, if new crude oil is not replenished in time, the fat content is very small at this time, coupled with high temperature, the temperature of the emulsion may also exceed 45 °C, which will easily cause oxidation and blackening.

(4) Another situation is that due to the common use of high-speed wire drawing at present, its speed is increased, and the relative heat dissipation time is reduced, which brings a certain space and time to oxidation. Therefore, it is recommended that manufacturers pay more attention to the fat content of the emulsion. Whether the temperature and pH of use are appropriate, the bacteria multiply rapidly in the spring yellow mold and rainy season, you can use bactericidal and mildew proofing agents, and in summer, antioxidants can be used to solve the problems of oxidation and blackening.

Reasons:

1. The deformation of the finished mold is too small;
2. The periphery and front of the mold sleeve are not well sealed.

Solution:

Add a rubber pad to the exit direction of the finished mold, and then press the finished mold with threads to solve the problem of oil leakage.

The deformation of the finished mold is too small, which is a common mistake. The single-mode deformation requires a minimum amount of deformation, so that the pressure generated may be greater than the yield limit of the metal, plastic deformation can be realized, and the size can be stable. Only single-line surfaces will have the light generated by cold drawing.

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Insulation resistance test:

Insulation resistance reflects an important indicator of the insulation properties of wire and cable products, which is closely related to the electrical strength of the product, dielectric loss, and the gradual deterioration of insulating materials under working conditions. For communication cables, if the insulation resistance between lines is too low, it will also increase loop attenuation, crosstalk between loops, and long-distance power supply leakage on the conductive core. Therefore, the insulation resistance should be higher than the specified value.

Determination of insulation resistance can find defects in the process, such as insulation dry and impervious or sheath damaged and damp; insulation is polluted and mixed with conductive impurities; insulation layer cracking caused by various reasons, etc. In the operation of wires and cables, it is often necessary to detect insulation resistance and leakage current as the main basis for continued safe operation.

At present, in addition to the ohmmeter (shake meter), the commonly used galvanometer comparison method is the high resistance meter method (voltage-current method) to measure the insulation resistance of wires and cables.

Measurement of capacitance and dissipation factor:

When the AC voltage is applied to the cable, a current flows. When the amplitude and frequency of the voltage are constant, the magnitude of the capacitor current is proportional to the capacitance (Cx) of the cable. For ultra-high voltage cables, the current of this capacitor may reach a value comparable to the rated current, which becomes an important factor for maximum cable capacity and transmission distance. Therefore, the capacitance of the cable is also one of the main electrical performance parameters of the cable.

Partial discharge measurement:

There is basically no local power generation for oil-filled cables; even if there is partial discharge in oil-paper cables, it is usually very weak, such as a few PCs, so these cables can be exempted from partial discharge in the factory test. For extruded cables, not only the possibility of partial discharge is high, but also the damage of partial discharge to plastic and rubber is also serious. For extruded cables, partial discharge measurements are required in the factory test.

There are many measurement methods for partial discharge. The discharge pulse can be measured according to the instantaneous charge exchange generated by the discharge (electric measurement method); the voltage can also be measured according to the ultrasonic wave generated during the discharge (acoustic measurement method); it can also be measured according to the light generated by the discharge. , to measure the intensity of light (photometry). For cables, the electrical measurement method is basically used.