1. The test delivery method primarily focuses on checking the residual current device (RCD) itself. The process involves first disconnecting the power supply, then removing all the load-side leads of the zero-sequence transformer from the RCD (for secondary and tertiary RCDs, simply remove the outgoing lines). After that, reconnect the protector. If the RCD still fails to operate, it indicates a fault within the device, which should be repaired or replaced. However, if the RCD operates normally, it suggests that the issue lies elsewhere—such as in the switchboard or the wiring. To locate the problem, start by cutting off the output of each line or AC contactor. If the RCD still doesn’t trip, the issue is likely with the switchboard. In this case, check whether the insulation of the electrical and instrumentation equipment on each circuit is intact and whether the wiring is correctly installed. If the RCD operates properly, there is no fault on the switchboard. When the fault is confirmed to be on the external line, the branch-line search method can be used to pinpoint the exact location.
2. The intuitive inspection method involves visually examining and identifying the fault phenomenon. This includes inspecting both the RCD and the protected equipment, focusing particularly on areas prone to faults, such as corners, branches, and crossover points of the wiring. This approach is straightforward and efficient for locating issues like broken wires, short circuits, or incorrect wiring.
3. The numerical comparison method involves using instruments to measure the line or equipment and comparing the results with original values to identify the fault point. It's important to note that when the neutral line’s insulation drops or the equipment’s neutral line is repeatedly grounded, it may cause the main protection to trip frequently while the secondary RCD remains unaffected. When addressing tripping issues on the secondary RCD, avoid switching the phase and neutral lines to restore protection. Instead, consider removing the repeated grounding wire to resolve the problem.
4. The line elimination method is useful when troubleshooting line faults. Begin by disconnecting the branch lines of the low-voltage power grid in the order of "main line first, then sub-branches, and finally the end." Test only the main line. If no fault is detected, the main line can operate normally. Then, gradually reintroduce the branches and ends one by one. If the RCD trips upon reactivating a specific line, the fault is located on that particular line. This allows for a centralized identification of the faulty section.
DongGuan BoFan Technology Co.,Ltd. , https://www.ufriendcc.com