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Basic cable performance test

Pubdate:2012-04-17 15:16 click:
A routine test: experiments conducted by the manufacturer on all finished cable. Its purpose is to check the quality of products meets the requirements of technical conditions in order to find the chance of defects in the manufacturing process. It is non-destructive experiments, such as the DC resistance of the wire, insulation resistance. Partial discharge detection and pressure testing.

    
The type test: is the manufacturer of the product on a regular basis to conduct a comprehensive performance test, especially stereotypes to mass production of a new product or a product structure, materials and processes have to change which may affect the performance of the cable when the tests. Type test: test of the product can meet the requirements of running, and can be compared with the old product. Such as insulation and sheath heat aging performance, power cable long-term stability tests.

    
Acceptance test: acceptance test is carried on the cable after the cable installation laying, in order to check the quality of installation and found that the damage may have been born in the construction. Such as the installation of the withstand voltage test.

(2) pilot projects
2.1 wire DC resistance measurement
    
Conductive wire core wire and cable for power transmission or electrical signals. The resistance of the wire is the main indicators of its electrical properties, the role of AC voltage line core resistance due to skin effect, proximity effect face than the DC voltage is large, but a small difference of the electric eye frequency is 50Hz, now standard requirements DC resistance or resistivity of the test line core over the provisions of the standard of value that are only requirement, this check can be found some defects in the production process: If the wire break or part of the single-wire fracture; wire section is not meets the standards; the length of the product is not correct. Allow the carrying capacity of the operation of the power cable, but also check whether it will affect the wire and cable products.

    
Measurement of the DC resistance of conductor single-arm DC resistance and the arm DC bridge method, the accuracy of the latter than the former. Test steps over the former complex.

2.2 Insulation resistance test
    
Insulation resistance, an important indicator to reflect the insulating properties of wire and cable products, it is the product of the electric strength, dielectric loss, as well as the gradual deterioration of insulating materials in working condition are closely related. Communication cable, line insulation resistance is too low will increase the loop attenuation, crosstalk between the circuit and the conductive wire core long-distance supply leak, etc., require insulation resistance should be higher than the specified value.

    
Determination of insulation resistance can be found flaws in the process, such as insulation dry through or sheath damage from moisture; insulated by the pollution and conductive contamination; a variety of causes insulation cracking. The running of wires, cables, often to detect insulation resistance and leakage current as to whether the main basis for the continued safe operation.

    
Wire and cable insulation resistance measurements, in addition to the ohmmeter (shake table), commonly used galvanometer Comparative Law impedance meter method (voltage - current law).

2.3 capacitance and loss factor measurement
    
Cable coupled to the AC voltage, there is current flow, when the voltage amplitude and frequency of a certain size of the capacitor current is proportional to the cable capacitance (Cx). Extra high voltage cables, the current of this capacitor may reach values ​​can be compared with the rated current, an important factor to limit the cable capacity and transmission distance. So one of the capacitance of the cable is the cable electrical performance parameters.

    
In the alternating electric field, the cable insulator due to leak current and a variety of polarization exists, will form the dielectric loss, dielectric loss factor or loss tangent (tanδ) said it is not only a waste of electricity, and make the media (insulator ) fever, accelerated insulation aging, the therefore TANδ one of the main parameters of cable.

    
Can be found through the measurement of capacitance and dissipation factor of insulation moisture, insulation and shield off a variety of insulation degradation phenomena in terms of cable manufacturing or cable running capacitance and TANδ measurement.

    
On the high voltage cable Cx and TANδ, measurement of their working conditions, namely the power frequency under high pressure, commonly used high-pressure resistant bridge, this year also started using the current transformer bridge.
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