NOYAFA Electronic specializing in testing instruments and cable testers for 16 years
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NOYAFA Electronic specializing in testing instruments and cable testers for 16 years
Author: Noyafa–Cable Tester Manufacturer
Cable fault finding Cable fault property classification Cable fault finding Power cable faults are caused by damaged electrical insulation of the cables, and the projects of vivid faults are generally divided into two categories: low-resistance blocking, excavation and congestion faults; high-resistance faults wind and flashover faults. Low-resistance faults, where the insulation resistance at the fault point of the cable drops to the characteristic impedance of the cable, or even the faults with zero DC resistance, are called low-resistance faults or plugging faults (Note: This definition is from the perspective of applying the pulse mapping method, considering the Due to the influence of the different wave impedance on the polarity change of the reflected pulse, for this railway bridge method, the concept of low-resistance fault is not limited by the definition of characteristic impedance) Here is a reference value of cable characteristic impedance: aluminum The characteristic impedance of a power cable with a cross-sectional area of 240m2 is about 10Ω, the characteristic impedance of the power cable of the profiler with aluminum core 35m2 is about 40ΩThe characteristic impedance of aluminum core power cables of any cross-sectional area can be calculated carefully. Generally, the cable resistance is infinite or the insulation resistance value of the normal cable is the same, but the voltage can never be fed to the user. The faults in which the DC resistance at the fault point of the resistance fault cable overwhelms the characteristic impedance of the cable are all high resistance faults. Leakage fault When the cable is quenched and tested for insulation, the leakage current increases with the increase of the test voltage.
When the test voltage rises sharply to the rated value (sometimes far reaching the default rated value), the leakage current exceeds the allowable value. The indicator value of the degree meter rises steadily, and the needle shakes in a flashover manner. When the voltage drops slightly, this phenomenon disappears, but the cable insulation still has a very high resistance value, which indicates that the cable is faulty. And this kind of failure point never distributes the floodway to Qin Muchu resistance, unless the failure after the discharge of tea or wine or the external failure of the flashover is called a flashover failure. Classification of cable faults Cable fault finding Shenzhen Noyafa Electronic Technology Co., Ltd.
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