Analysis and treatment of the protection action of

2022-07-24
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Analysis and treatment of protection action of power transformer

power transformer is one of the most important equipment in substation. The safe operation of transformer plays a decisive role in the safe use of electricity by power customers. The relay protection of transformer is to measure the change of current, voltage, oil temperature, etc. when a fault occurs inside or outside the transformer, through these sudden changes to find and judge the nature and scope of transformer fault, and then make corresponding response and treatment

inspection and treatment after transformer relay protection action

after relay protection action, if it is confirmed that it is quick break protection action, the signal sound can be temporarily removed. If there is gas (gas relay) protection, first check whether the gas protection acts. If it does not act, it indicates that the fault point is outside the transformer. Focus on checking the power supply lines of the transformer and the high-voltage circuit breaker to see if there is phase to phase short circuit fault in the cable and bus. In addition, the connection angle sensor shall also focus on checking whether the high-voltage lead of the transformer has obvious fault points and other obvious abnormal phenomena, such as oil injection, fire and excessive temperature rise of the transformer

if gas action is found, it can be basically judged that the fault is inside the transformer

firstly, when the transformer winding is short circuited locally between turns and layers, the iron core insulation is poor, and the transformer is seriously leaking oil, the oil level drops, and the light gas will act; When a serious fault occurs in the transformer, such as phase to phase short circuit caused by primary winding fault, the fault current causes the transformer to produce strong air flow and oil flow, impacts the heavy gas baffle, makes the heavy gas act, and the circuit breaker trips and sends a signal

secondly, if there is no obvious abnormality in the transformer at that time, the gas in the transformer can be collected to further analyze and determine the nature of the fault. If the collected gas is colorless, tasteless and nonflammable, it indicates that the action of the gas relay is caused by the air discharged from the oil; If the collected gas is yellow and not easy to burn, it indicates that the wooden part of the transformer is faulty; If the gas is light yellow with strong odor and combustible, it is the fault of insulating paper or paperboard; When the gas is gray or black flammable, it is insulation oil fault. For outdoor transformers, the gas valve of the gas relay can be opened to ignite the gas discharged from the vent valve. If the gas is flammable, it will burn and emit a bright flame. It should be noted that when the oil begins to overflow from the vent valve, the vent valve should be closed quickly; For indoor transformer, ignition test shall not be conducted indoors; Judge the gas color quickly, otherwise the gas color will disappear soon; Take gas from transformer after power failure

again, if the cause of the gas protection action has not been found out, in order to further confirm whether the transformer is in good condition, the transformer oil sample can be taken for a simplified test to see whether there is a reduction in withstand voltage and oil flash point. If there is still no problem, the secondary circuit of gas protection shall be further checked to see whether it is due to misoperation of gas protection, so as to verify the reliability of relay protection. When the heavy gas of the transformer acts, the circuit breaker is tripped. If the fault treatment is not carried out and the transformer is not proved to be free of fault, it is not allowed to switch on again for power transmission

if differential protection action is found, it is necessary to judge the cause of action. It is necessary to accurately determine whether it is caused by transformer bushing or voltage transformation. This is the cause of internal failure of a thin-film secondary battery which forms a solid electrolyte on the resin film

precautions relays and protection elements with good quality shall be selected for relay protection devices, and the contacts of elements shall be as few as possible; The installation quality shall be qualified. The protection panel and control panel shall be firm and reliable, and shall not be installed in places with vibration. The quality of wiring terminals shall be qualified and the wiring shall be good. Before the relay is put into operation, the personnel on duty and operating personnel shall clearly understand the working principle of the protection device

during the operation of relay protection device, if any abnormal phenomenon is found, strengthen the monitoring and immediately report to the power dispatching department; Unless approved by the power dispatching department, the relay protection device in operation shall not throw off the protection operation at will, nor change the setting value and secondary line at will; The input or exit of the operating relay protection device by the operator must be approved by the dispatcher or the person in charge, and recorded in the duty record book. If it is necessary to change relay protection setting value or secondary circuit wiring, it must be approved by relay protection professionals

all work on the secondary circuit shall comply with the relevant provisions of the electrical safety work regulations

when switching operation of the operator on duty involves relay protection circuit, necessary treatment shall be carried out for the relay protection according to the performance of the relay protection device and the provisions of the operation regulations, but remember that the operator on duty is only allowed to connect or disconnect the protection pressure plate for the operation of the relay protection device; Change over switch; (2) Determination of yield limit of low carbon steel σ S and strength limit of cast iron σ B. load and unload the fuse of fuse

after the tripping of the relay protection action circuit breaker, do not immediately reset the lost card signal, but check the protection action and find out the cause. Before the different function demands of these products are eliminated and the power supply is restored, all the lost card signals can be reset

in a word, the transformer relay protection must be checked and tested according to the regulations after the action, and the power supply operation is not allowed until the cause is found out

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