Cable Tray Faults Comparison and Solutions

We understand that low-voltage cables have relatively low insulation performance requirements, and during operation, the current is generally large. Therefore, after a fault occurs, it will exhibit more obvious characteristics. These characteristics can be summarized into the following categories.

• The entire cable line is completely burned or one of the phases is damaged, causing all the current relays on the distribution cabinet to activate. The damage at the fault location is extremely severe.
• Short circuits occur in all phases of the cable, which will also trigger the interlocking reaction of the current relays and voltage relays on the distribution cabinet. The damage at the fault point of the cable is also very severe (possibly due to external forces).
• If only one phase of the cable tray is open, the current relay will activate, and the damage at the fault point is relatively minor but more noticeable. This situation may be caused by excessive current in that phase or a quality issue with the cable itself.
• A short circuit occurs inside the cable without leaving any traces on the surface. This type of fault usually stems from a quality issue with the cable itself and is considered rare.

In the DW type low-voltage cable fault location system, the combined use of the distance meter and the locator can conveniently complete the detection work. In addition, various fault characteristics and the length of the cable tray can also be tested separately. The specific operations are as follows:

• For the first and second types of faults, if the cable length is relatively short (less than 500 m), there is no need to use a distance meter. The fault can be located by only using the locator. Simply walk along the path (measuring as you go) with the handheld receiver to determine the fault point.
• For the third type of fault, since the damage to the cable tray at the fault point is relatively minor and the signal leakage from the transmitter is small, the indication range when using the locator is narrow. In this case, the approximate distance to the fault point can be measured first with the distance meter, and then the locator can be used for precise positioning, making the operation quite convenient.
• For the fourth type of fault, this type of fault is currently the most troublesome among all cable faults. At this time, a rangefinder can be used to test at both ends of the cable, and then the test results can be compared with the actual length, thereby locking the fault point within a very small range (about 1–3 m). At this time, the cable can be excavated to find suspicious points, or this section of the cable can be directly cut off (low-voltage cables are inexpensive, have low insulation requirements, and joints are easy to make), or a locator can be used to employ audio positioning technology within this range to determine the fault point.