The electrical performance of electronic and electrical equipment directly affects the safety and reliable operation of the entire electrical system. In order to ensure equipment safety, all electronic and electrical equipment must pass various type tests during production and manufacturing to ensure the safety of the electrical environment. The electrical performance test includes the basic parameter test of conductor or insulation quality, such as conductor resistance, insulation resistance, correct value of dielectric loss angle, capacitance, etc. The higher the working voltage of the cable, the stricter the electrical performance requirements.
Introduction to electrical performance:
1. Electrical performance index, DC resistance and AC impedance of conductor, insulation resistance of insulation layer.
2. The main media of electrical performance are loss, electric field distribution and electric field strength, cable capacitance, inductance, current carrying capacity, and induced voltage and current of metal sheath.
3. The mechanical strength, elongation, mechanical properties, flame retardancy, insulation aging life, etc. of electrical performance cables.
4. The electrical property refers to the electrical characteristics of the electrical load, the importance of the electrical load, the electrical time, occasion, purpose, and allowable outage time of the electrical load.
5. The requirements and impacts on power supply quality are different due to different electrical properties of electrical performance, and the position in the power load curve of the power grid is also different.
Electrical performance test:
The electrical performance test includes the basic parameter test of conductor or insulation quality, such as conductor resistance, insulation resistance, dielectric loss, capacitance, etc. The higher the working voltage of the cable, the stricter the electrical performance requirements.
1. DC resistance test of conductive core:
The resistance of the cable with each nominal section should not exceed a certain equivalent value, or it will increase the core loss of the cable in use, thus causing cable heating. This not only consumes electrical energy, accelerates the aging of plastic cables, but also brings risks to the reliability and stability of cable operation. Double arm bridge is commonly used for measurement.
2. Insulation resistance test
The ratio of the DC voltage U applied to the insulation to the leakage current I is called insulation resistance R. The insulation resistance of the cable is mainly used to judge the moisture degree and insulation quality of the cable insulation layer. If the cable is not dry enough or damp too much during the manufacturing process, the insulation resistance will be greatly reduced. In addition, if the insulation layer contains too many conductive impurities, the insulation resistance will also be reduced. If the insulation resistance of the cable is too small, it will cause large leakage current, which will increase the insulation temperature and accelerate the aging of the wire. Voltage current method is widely used to measure the insulation resistance of cables.
3. Immersion voltage test
Most wires and cables used for electrical equipment do not have metal sheaths or metal wire braids as the outer electrodes for voltage tests. When conducting voltage withstand tests on these products, they must be immersed in water, that is, water is used as the outer electrodes for insulating surfaces and uniform contact resistance between products and products. It is mainly applicable to insulated core and single core sheathed wire and cable of the product. During the test, the conductor core is connected to the high voltage end and the water is connected to the low voltage end. Before the test, check the grounding reliability, and fully discharge after the test.
4. Spark test
Spark withstand voltage test is a fast and connected withstand voltage test method. The purpose of the test is to find out whether there are defects in the process or impurities in the material, so as to ensure the basic electrical performance of the product. During the spark test, the conductor must be grounded.
5. Partial discharge test
It refers to the phenomenon of partial and repeated breakdown and extinction under a certain applied voltage due to the internal weakness of the insulating medium. The purpose of the test is to judge whether there is obvious partial discharge in the sample under the working voltage, and check the dissociation performance in the insulation; Measure the starting voltage of internal discharge of insulation; Measure the degree of partial discharge under the specified voltage. At present, high-frequency electric pulse method is most commonly used for measurement.
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