What should be done after the transformer differential protection trips?

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Checking and addressing issues that arise after the operation of the transformer differential protection device are matters that station operators should be aware of. Through the following learning, station operators can gain a deeper understanding of the safe operation and protection of transformers. Preparatory work: 1. Wear appropriate personal protective equipment. 2. Equipment preparation: One 35KV substation ； Transformer protection device ； Transformer measuring device ； 8000KVA transformer ； One set of disconnect switches each on both sides of the 6KV and 35KV main transformers. 3. Equipment preparation: One voltage tester each for 6KV and 35KV ； Wiring cable ； Transformer protection control diagram ； Notebook, pen. Procedure: Step 1: In a substation where differential protection triggers and causes the main transformer to trip, as required by regulations, the following phenomena occur: 1. The alarm bell sounds; 2. The signal relay does not return to its normal state, and the optical indicator lights up. 3. The red light of switch 0031 on the 35KV side of the No. 1 main transformer has gone out, and the green light is flashing. 4. The red light of switch 0001 on the 6KV side of the No. 1 main transformer has gone out, and the green light is flashing. 5. The meters on the No. 1 main transformer are not giving any readings. Item 2: Inspect the protective switches and their tripping conditions
1. Record the time when the fault occurred.
2. The assistant operator resets the audible alarm.
3. The assistant operator moves the KK handle of switch 0031 on the 35 kV side of Main Transformer No. 1 to its post-tripping position.
4. The assistant operator moves the KK handle of switch 0001 on the 6 kV side of Main Transformer No. 1 to its post-tripping position.
5. The main operator checks the protection panel and finds that the differential protection signal relay for Main Transformer No. 1 has dropped out.
6. The main operator reports to the Central Dispatching Center regarding the fault-induced tripping, including the time, changes in instrument readings, and the protective actions taken by the tripped switches.
7. The main operator also reports to the Regional Dispatching Center regarding the same information.
8. The assistant operator resets the signal relay, or manually resets it at the protection panel.
9. Inspect the operating conditions of all equipment connected to the circuit breakers on both the high-voltage and low-voltage sides of the main transformer.
10. Check whether the switches on both the high-voltage and low-voltage sides have tripped, and determine if there are any external short-circuit faults. 11. Check the wiring of the circuit breakers on both the high-voltage and low-voltage sides, as well as the current transformers, to determine if there are any faults. 12. Inspect the isolators on both the high-voltage and low-voltage sides. Thirdly, inspect the transformer itself: 1. Check the exterior of the transformer, its bushings, and leads for any signs of discharge or arcing. 2. Check whether the transformer bushing is dirty or cracked, and whether the leads are broken. 3. Check for any severe leakage or oil spraying from the transformer. 4. Verify that the oil color, oil temperature, and oil level are within normal ranges. 5. Check for any faults in the primary equipment on all sides within the transformer’s differential protection area, as well as in the current transformer leads and bushings. Also, inspect the tap changers.
Fourth item: Checks outside the differential protection circuit
1. Check whether there are any other protection activation signals in the substation.
2. Verify that the voltage of the DC circuit power supply is normal.
3. Ensure that there is no ground fault in the DC power supply system.
Fifth item: Isolate the faulty transformer in accordance with the dispatch instructions. 1. Fill in the switching operation ticket for the shutdown and maintenance of Main Transformer No. 1 correctly under the scheduling instructions. 2. Execute the scheduling command to switch main transformer No. 1 from hot standby to maintenance mode; for the specific procedures, refer to item 6 of the switching operation ticket: record the accident details in the duty log. 1. Keep records of switch failures and tripping incidents, as well as records of relay protection and automatic device adjustments. Precautions: 1. If the cause of the failure is unknown, it is strictly prohibited to put the faulty transformer back into operation. 2. During accident handling, closely monitor the load and oil temperature of the operating transformers to prevent overloading and ensure their safe operation. 3. Check for any faults in the primary equipment within the range covered by the differential protection; determine whether the differential protection has operated correctly. Faults outside this range or failures of the gas protection indicate incorrect operation of the protection system. 4. Protection system errors such as multiple ground faults in the DC system. This article is from: http://www.weijizongbao.com/jishu/145.html Please indicate the source when reproducing this content!