As an indispensable core equipment in the power system, the stable operation of transformers is directly related to the safety and continuity of power supply. Both the commonly used 250 kva power transformer and the isolation power transformer used for electrical isolation and equipment safety protection may trip due to various faults during long-term operation. Timely and scientific handling of transformer tripping accidents can effectively avoid fault expansion, reduce economic losses, and extend equipment service life. This article will detail the handling methods of various transformer tripping accidents, providing professional reference for industry practitioners.
This article is compiled and released by JINSHANMEN TECHNOLOGY CO., LTD. The company mainly produces oil immersed power transformers, dry-type power transformers, oil immersed three-dimensional coiled power transformers, dry-type three-dimensional coiled power transformers, mining explosion-proof dry-type transformers, mining explosion-proof mobile substations, amorphous alloy power transformers, on load capacity regulating power transformers, locomotive dry-type transformers, as well as prefabricated substations, modular substations, wind energy box type substations, high and low voltage switchgear and other transmission and distribution equipment. With professional production technology and perfect quality control, it provides reliable power transmission and distribution solutions for global users.
I. Handling After Transformer Gas Protection Operation
1. Handling After Light Gas Protection Operation
After the light gas protection sends a signal, the sound signal should be stopped first, and the nature of the gas in the gas relay should be inspected to judge whether a fault has occurred based on color, odor, and flammability. If the light gas protection operation is not caused by a transformer fault, such as air entering the transformer due to oil filtration or refueling, slow drop of oil level due to temperature decrease and oil leakage, or misoperation caused by the impact of external through short-circuit current, insulation damage of DC circuit or contact deterioration, the transformer can continue to operate after resetting the signal. The handling logic of light gas misoperation is applicable to both 250 kva power transformer and isolation power transformer. If a small amount of gas is generated due to a minor transformer fault, a report should be made immediately after resetting the signal; if it is confirmed to be an internal fault of the transformer, the transformer should be taken out of operation and necessary inspections should be carried out.
2. Handling After Heavy Gas Protection Operation
If the operating transformer trips due to gas protection action, it may be due to a serious transformer fault, a sharp drop in oil level, a fault in the secondary circuit of the protection device, or rapid oil filling after maintenance with short static time, which causes the heavy gas protection to trip after air separation in the oil. After the gas signal is sent, the sound signal should be stopped first, and the gas in the gas relay should be collected to judge the cause of the gas relay action according to the amount, color, odor, and flammability of the gas.
To further determine the nature of the internal fault of the transformer, oil samples should be taken immediately for gas chromatographic analysis and necessary tests. After the heavy gas protection trips, the transformer shall not be put into operation without detailed inspection and measurement and unknown causes. This requirement applies to all types of transformers, including 250 kva power transformer and isolation power transformer, to avoid fault expansion caused by blind power transmission.
II. Handling After Transformer Differential Protection Operation
All transformers with a capacity of 10000KVA and above are equipped with differential protection. The main transformer differential protection is manufactured according to the circulating current principle, and the transformer differential protection action will trip the switches on both sides. For the 250 kva power transformer, although its capacity does not reach 10000KVA, some transformers of this model used in industrial scenarios are also equipped with differential protection according to needs. The isolation power transformer is often used for power supply of precision equipment, so the reliability of its differential protection is particularly important.
After opening the disconnectors of the circuit breakers on both sides, the following key inspections should be carried out:
(1)Whether the transformer bushings are intact and whether there are signs of flashover on the busbars connected to the transformer;
(2)Inspect all primary equipment within the transformer differential protection zone (all equipment and connections between the high and low voltage side circuit breakers) for abnormalities.
If there is no problem in the above inspections, further inspect whether there is an internal fault of the transformer. If the transformer trips due to an external short circuit outside the differential protection zone, the transformer can be put into no-load closing test power transmission.
III. Handling After Transformer Backup Protection Operation
(1)When the transformer time-limit overcurrent protection trips, the sound should be lifted first, and then a detailed inspection should be carried out to see if there is a possibility of overstep tripping, that is, check the operation of the protection device of each outgoing circuit breaker: whether each signal relay is dropped; whether each operating mechanism is stuck.
(2)If it is impossible to find out which outgoing line causes the overstep tripping, all circuit breakers on the low-voltage side should be disconnected, and the low-voltage busbar and transformer body should be inspected for abnormalities. If there is no abnormality, a no-load test can be performed once. After normal operation, power can be supplied to each line one by one to find out which outgoing line causes the overstep tripping.
(3)If there is no fault in the transformer body but a fault in the busbar, the test closing power transmission can be carried out after the busbar fault is eliminated. If there is a fault in the transformer body, it is not allowed to close and transmit power. A report should be made to the superior and wait for handling. For the isolation power transformer, because it undertakes the important role of electrical isolation, the inspection after the backup protection action needs to be more detailed to avoid affecting the safety of downstream precision equipment due to faults.
IV. Handling of Transformer Cooling Device Faults
(1)When a single fan fails, stop the cooling unit first, report to the shift leader to contact maintenance personnel to repair or isolate the faulty fan, and then the cooling unit can be put back into operation;
(2)If the oil pump or secondary circuit fails and the cooling unit trips automatically, check whether the standby cooling unit is put into operation automatically; if not, put it into operation manually, and then check the cause of the fault;
(3)When there is a large amount of oil leakage from the cooling unit components, stop the operation of the cooling unit immediately, close the oil inlet and outlet valves of the cooling unit, and disconnect the power supply of the cooling unit;
(4)If the working power supply of the cooling device is interrupted, the other circuit should be automatically switched on. If the automatic switching is successful, check whether the contactor is operating well and switch the power switch to the corresponding position; if the automatic switching is not successful, quickly manually switch on the other circuit to restore the normal operation of the cooling device;
(5)When the cooling device fails and all cooling units are out of service, the temperature of the transformer will rise rapidly. The oil temperature and winding temperature of the transformer shall not exceed the maximum allowable temperature, and contact maintenance for handling at the same time; if all cooling units are out of service due to power failure, the power supply should be restored as soon as possible, striving to handle it within 20 minutes;
(6)When all main transformer cooling units are out of service, if it cannot be handled within 20 minutes, the upper oil temperature should be monitored at this time. If it does not exceed 75℃, it can be extended to 60 minutes; if it cannot be handled within 60 minutes, timely report to the shift leader to contact shutdown handling;
(7)After all cooling units are out of service, while closely monitoring the upper oil temperature, timely report to the shift leader to reduce the load operation. If the oil temperature continues to rise, apply for immediate shutdown handling before the upper oil temperature of the transformer reaches 75℃. The stable operation of the cooling device is crucial for the continuous power supply of the 250 kva power transformer, which can effectively avoid tripping accidents caused by overheating.
JINSHANMEN TECHNOLOGY CO., LTD reminds practitioners that the core of handling transformer tripping accidents is "judge first, then inspect, and then transmit power". It is strictly prohibited to blindly close the switch when the cause is unknown. Whether it is 250 kva power transformer, isolation power transformer, or other types of power transformers, regular maintenance and daily inspection are the key to preventing tripping accidents. The company can provide professional equipment maintenance guidance and high-quality transformer products to help enterprises achieve stable operation of the power system.