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
Buried cable power supply has been more and more widely used because of its advantages of safety, reliability, and beautifying the layout of cities and factories and mines. However, buried cables are generally buried underground. Once a fault occurs, it is necessary to use a suitable buried cable fault test method. Buried cable power supply has become more and more widely used because of its safety, reliability, and advantages such as beautifying the layout of cities and factories and mines. Applications. However, buried cables are generally buried in the ground. Once a fault occurs, it is necessary to use a suitable buried cable fault test method to find the fault point as accurately as possible, and quickly repair the buried cable fault to reduce losses caused by power outages.
The finding of buried cable faults generally goes through three steps: diagnosis, ranging (pre-positioning), and fixed-point (precise positioning). After a buried cable fault occurs, the nature of the fault is generally first determined by measuring the insulation resistance; Before and after this position, carefully probe the fixed point until the precise fault point position is found, so as to realize the fault repair of the buried cable. Fault types of buried cables To repair the faults of buried cables, first analyze the causes of the faults of buried cables and determine the types of faults of buried cables.
There are many reasons for the failure of buried cables, such as: mechanical damage, insulation damp, aging and deterioration of insulation, overvoltage, material defects, loss of cable insulation, poor design and manufacturing process, and sheath corrosion. According to the location of the buried cable fault, the fault types can be roughly divided into disconnection fault, main insulation fault and sheath fault. The disconnection is generally caused by the fault current of the buried cable being too large, the core wire of the cable is blown or the external mechanical damage is caused, and the test is relatively simple.
The main insulation fault can generally be equivalent to a circuit, in which the resistance scale mainly depends on the carbonization degree of the cable medium, the breakdown voltage of the gap G depends on the distance of the discharge channel, and the capacitance Cf depends on the fault point and the degree of moisture in its vicinity (their The value is small and can generally be ignored). According to the fault resistance and breakdown gap, the main insulation faults are usually divided into low resistance, high resistance and flashover faults. The distinction between low-resistance faults and high-resistance faults is generally 10 times the wave impedance of the cable itself, but it is not required to be strictly distinguished in actual test work.
The resistance of the fault point of the flashover fault is extremely high, and a higher voltage can be applied to the faulty cable, and the fault point will flash over and break down. This is often the case with failures that occur in preventive tests.
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