1. Correctly and fully utilize the fault information provided by the microcomputer. Simple accidents that frequently occur are easy to troubleshoot, but for a few faults, relying solely on experience is difficult to resolve; correct methods and steps should be adopted.
1.1 Correctly handle human-caused accidents. After some relay protection accidents, the cause of the fault cannot be found based on on-site signal indications, or there is no signal indication after the circuit breaker trips, making it impossible to determine whether it is a human-caused accident or equipment accident. This situation often occurs due to insufficient attention from the staff, inadequate measures, and other reasons. Human-caused accidents must be truthfully reported to facilitate analysis and avoid wasting time.
1.2 Fully utilize fault recording and time records. Microcomputer event records, fault recording waveforms, and device light display signals are important bases for accident handling. Making correct judgments based on useful information is the key to solving problems. If a comprehensive inspection of the primary and secondary systems reveals that the primary system fault caused the relay protection to operate correctly, then there is no issue of relay protection accident handling; if it is determined that the fault lies in the relay protection, the original state should be maintained as much as possible, records should be made, and work should be carried out after formulating a fault handling plan to avoid unnecessary trouble caused by destroying the original state.
2. Use correct inspection methods
2.1 Reverse order inspection method. If the root cause of the accident cannot be found in a short time using microcomputer event records and fault recording, attention should be paid to starting from the result of the accident and tracing back level by level until the root cause is found. This method is often applied when protection malfunctions occur.
2.2 Sequential inspection method. This method uses inspection and debugging means to find the root cause of the fault. It is carried out in the order of external inspection, insulation detection, setting value inspection, power supply performance testing, protection performance inspection, etc. This method is mainly applied in accident handling where microcomputer protection refuses to operate or logic problems occur.
2.3 Use the whole group test method. The main purpose of this method is to check whether the action logic and action time of the protection device are normal. It can often reproduce the fault in a very short time and determine the root cause of the problem. If abnormalities occur, combine with other methods for inspection.
3. Precautions in accident handling
3.1 Requirements for test power supply. When conducting microcomputer protection tests, it is required to use a separate power supply, and verify whether the test power supply used is three-phase positive sequence and symmetrical voltage, and check whether the sine wave and neutral line are good, and whether the power capacity is sufficient, etc.
3.2 Requirements for instruments and meters. Instruments that take voltage signals, such as multimeters, voltmeters, oscilloscopes, etc., must be selected with high input impedance. For relay protection testers, phase shifters, and three-phase voltage regulators, attention should be paid to their performance stability.
