Distribution cabinet malfunctions mainly refer to the failures that occur during the normal operation of various electrical components (circuit breakers, knife switches, fuses, instrument protectors, etc.) installed on the distribution cabinet.
1. Classification of power distribution cabinet faults
The main faults in the distribution cabinet include air circuit breaker tripping (overcurrent grounding), single-phase operation, burnt contacts, and burnt electrical components such as fuses, knife switches, and circuit breakers.
2. Causes of power distribution cabinet malfunction
Common causes of power distribution cabinet malfunctions include:
Loose connections; mismatched capacity ratios of electrical components; short circuits in the distribution cabinet; mismatch between incoming and outgoing lines and loads; unbalanced three-phase loads in the distribution room; and non-standard electrical components.
3. Troubleshooting Procedures for Power Distribution Cabinets
3.1 Fault Diagnosis
(1) Observe the instruments in the distribution cabinet to see if it is a high-voltage phase loss or a branch circuit trip, and identify the tripped circuit.
(2) If no fault point is found after the protector operates, it is allowed to test power once. If it operates again, the cause should be investigated. Power should not be supplied continuously. It is strictly forbidden to disconnect the protector without authorization.
(3) When one phase is missing, it is mostly caused by overcurrent. Records should be kept, the load of each phase should be measured, and adjustments should be made in a timely manner.
(4) When two phases are missing, a careful analysis should be conducted. First, determine whether it is caused by overcurrent or short circuit. Sometimes, one phase will burn out due to overload, and another phase will burn out due to continuous operation.
(5) Short circuits can also cause phase loss. When two phases are lost, a thorough analysis and investigation are necessary.
Analysis of power distribution cabinet fault handling in power supply station (Image 1)
3.2 Troubleshooting
(1) When a single phase loss occurs, replace the fuse or fuse element and try to power on once. If successful, power can be restored directly.
(2) When two phases are missing, all fuses or their fuse elements can be removed, and power can be supplied to any one of the two phases that are faulty. The other end can be tested for voltage. If there is no voltage, the fault may be caused by overload. The fuse or fuse element can be replaced and the power can be tested. If there is voltage at the lower end when testing for voltage, the fault may be caused by short circuit. The line should be inspected, the short circuit fault should be dealt with, and the power should be tested.
3.3 Troubleshooting Procedures
The standardized operating procedure is as follows: approve fault handling work and accept fault handling work tasks → hold a pre-shift meeting → prepare materials and tools → power outage work and permit work → handle and eliminate faults → work completion and power restoration → hold a post-shift meeting → file documents.
4. Safety Measures
4.1 Organizational measures to ensure safety
On-site survey system, work permit system (power outage work), work authorization system, work supervision system (minimum 2 members in the work team), work interruption system, work completion and power restoration system.
4.2 Technical measures to ensure safety
Power outage (opening the branch circuit breakers on the distribution cabinet and opening the main switch of the distribution cabinet), voltage testing (using a voltage tester to test the voltage of each phase), installation of grounding wires, use of personal safety wires, hanging of signs, installation of fences, and inspection of safety tools and equipment before work, etc.
5. Other precautions
Handling power distribution cabinet malfunctions requires a single person to operate the equipment; all power distribution cabinet malfunctions must be handled with the power off, and live operation is strictly prohibited; strictly adhere to the "two forms, two tickets, and two cards" system, and unauthorized operation by a single person is strictly prohibited; the use of unqualified safety tools and equipment is strictly prohibited, as is the use of non-standard electrical components.
