Fault diagnosis:

1）Disconnection: the failure of one or more core wires of a cable to break the signal, which is tested by the pulse method.

2）Hybrid wire: there are three types：grounding, self-mixing and other mixing . The damage to the insulation layer between the same pair of core wires and the wires of different pairs of wires, the decrease of insulation resistance to a very low level (hundreds to thousands of ohms), or even the occurrence of a short circuit, will seriously affect the signal quality. Such faults can be tested by pulse method first. When the waveform of cable fault tester is difficult to identify, the bridge method side test is carried out.

3）Poor insulation: the insulation material of the cable core is invaded by water or moisture, which reduces the insulation resistance and leads to poor or even blocked communication quality. This fault is similar to self-mixing, mixing and grounding, but the fault resistance is large (more than several thousand ohms) and the fault degree is relatively light. In general, if the insulation resistance is less than 2 megohm, it will affect the signal quality and need to be eliminated. Such faults are usually not detected by the pulse method, so a bridge must be used instead.

When a line failure occurs, megometers, multimeters, and other tools should be used first to determine the nature and severity of the line failure.

Testers understand the direction of the line and fault condition, help to determine the fault point quickly. When cable fault occurs, will consider the fault time, fault area, around the cable line, factors such as joint and the position of the manhole, and the weather, the influence of the system and the possible problems comprehensive consideration, according to the measured results, roughly judge fault segments.

Select test method:

When the fault resistance is less than a few hundred to a few thousand ohms, we become a low resistance fault, otherwise known as poor insulation or high resistance fault, there is no clear boundary between high resistance and low resistance.

The pulse method is suitable for testing the fault of mixed line with broken line and low resistance.Sometimes the pulse method is used to test the more serious faults with poor insulation. The pulse method is intuitive and easy to operate, and does not require the cooperation of partners. It should be used first during the test.

The bridge method can be used to test the insulation fault with high resistance difference, but a good wire must be found and needs to be matched with the other end, and the test preparation is also very tedious, after confirming that the pulse test method cannot be detected, the bridge method should be used.

The fault location:

During the test, the office equipment connected with the fault wire pair shall be disconnected first, and the test shall be conducted in the office to determine the minimum segment of the fault point, and then the test shall be repeated in the field to determine the exact location of the fault point.

According to the test results and drawings of the power cable fault tester instrument, the position of the specific fault point is calibrated.When the drawing information is incomplete or incorrect, the approximate location of the fault point can be estimated according to the cable line condition, and then the fault cause can be analyzed according to the fault situation and surrounding environment until the fault point is found.For example, if there are connectors in the estimation range, you can roughly determine that the point of failure is in the connector, and the longer the range, the greater the measurement error.