1, fault nature diagnosis:
The nature of cable faults can be simply divided into the following categories:
1) Broken wire: One or more wires of the cable are disconnected and the signal is interrupted. This failure is tested by the pulse method.
2) Mixing lines: divided into three types: grounded, self-mixed, and he mixed. They respectively mean that the insulation layer between the core and the lead, the same pair of cores, and the cores of different pairs is damaged. Insulation resistance Falling to a very low level (below a few hundred to several thousand ohms) or even a short circuit, the signal quality is seriously affected. This type of fault can be tested using the pulse method first. When the waveform of the cable fault tester is difficult to identify, the bridge method test is used again.
3) Poor insulation: The insulation material of the cable core is invaded by water or moisture, causing the insulation resistance to drop, resulting in poor communication quality and even blocking. This kind of failure is similar to self-mixing, mixing, and grounding, but the fault resistance is relatively large (a few kilo-ohms or more) and the degree of failure is lighter. In general, if the insulation resistance is less than 2 MΩ, it will affect the signal quality and need to be eliminated. This type of fault is generally not detectable by the pulse method and needs to be tested using the bridge method.
After the line fails, it is necessary to first use the measurement table, megohmmeter, multimeter, and other tools to determine the nature and severity of the line fault in order to select the appropriate test method.
The tester knows where the line is going and what the fault is and helps quickly identify the point of failure. After the cable fails, consider the time when the fault occurred, the range of the fault, the environment where the cable runs, the location of the joint and the manhole, the weather, and possible problems. Based on the result of the measurement, roughly judge the breakdown of the paragraph.
2, select the test method:
When the fault resistance is less than a few hundred to several thousand ohms, we become a low-impedance fault, and vice versa we call it a poorly-insulated or high-impedance fault. There is no clear line between high resistance and low resistance.
The pulse method is suitable for testing broken and low resistance mixed line faults. Severe insulation faults can sometimes be tested using the pulse method. The pulse method is intuitive, easy to use, and does not require mating. It should be used first when testing.
The bridge method can test high-insulation fault insulation faults, but it needs to find a good line, and it needs to be matched at the opposite end, and the preparation for the test is also tedious. The bridge method should be used after confirming that the pulse test method cannot be measured.
3, fault ranging:
When testing, disconnect the internal equipment connected to the fault line pair first. First test in the office to determine the smallest segment of the fault, then go to the site for retesting to determine the exact location of the fault.
4, fault fixed point:
According to the results of the instrument test, the location of the specific fault point is calibrated against the drawing data. When the drawings and data are incomplete or incorrect, the approximate location of the fault point can be estimated based on the cable lines that are available. Then, according to the fault conditions, the surrounding environment can be analyzed and the cause of the fault can be analyzed until the fault point is found. For example, if there is a joint within the estimated range, it can be roughly determined that the point of failure is within the joint. The farther the range, the greater the measurement error.
Magnetic Hold Relay,Magnetic Relay Pcb Type,Relay Magnetic 120A 220V,Double Coil Magnetic Hold Relay
Ningbo Xingchuangzhi Electric Appliance Co.,Ltd. , https://www.xingchuangzhi.com