Cable Fault Types:
Open Circuit Fault:An open circuit fault occurs when the cable insulation is normal, but the voltage cannot be transmitted normally due to conductor defects. Examples include a partially broken core or ground wire, a large line resistance at a point in the core, or a broken core. Simple open circuit faults are rare; they usually coexist with low-resistance or high-resistance faults.
Low-Resistance Fault:A low-resistance fault occurs when the cable insulation is damaged and can be directly tested using the "low-voltage pulse method" between phases. This is called a leakage-type low-resistance fault. The resistance value is typically below several hundred ohms. If the resistance is zero, it is called a short circuit fault, a special case of a low-resistance fault.
High-Resistance Fault:A high-resistance fault occurs when the cable insulation is damaged, forming a fixed resistance path, but cannot be directly measured using the "low-voltage pulse method" of a cable fault detector. The resistance value is typically above several hundred ohms. During a DC leakage withstand voltage test on a cable in the field, the leakage current value increases continuously with the applied DC voltage, far exceeding the cable's required specification value. Leakage-related high-resistance faults and low-resistance faults are relative and not strictly distinguishable.
Flashover-related high-resistance faults: Within the cable's pre-test voltage range, when the pre-test voltage reaches a certain value, the cable's leakage current value suddenly increases, significantly exceeding the cable's required specification value. This type of fault is called a flashover-related high-resistance fault. At this fault point, although the cable insulation is damaged, a fixed resistance path is not formed.
Panel Introduction
The cabinet door is open, as shown in the diagram below: There are 4 fault distances, with a wave velocity of 200 m/s.
Fault Location 1: Approx. 100 meters
Fault Location 2: Approx. 200 meters
Fault Location 3: Approx. 230 meters
Fault Location 4: Approx. 300 meters
T-Connector: Approx. 340 meters
Total Cable Length: Approx. 370 meters
