A pressure relief valve and oil-immersed power transformer fault detection method

Abstract

The present invention relates to the field of power systems, and in particular to a method for detecting faults in a pressure relief valve and an oil-immersed power transformer. By disposing a pressure sensor and a liquid level sensor at the bottom of the pressure relief valve housing, the present invention can monitor the pressure change status of the transformer oil tank and the amount of oil inside the pressure relief valve in real time and transmit the information to a control unit. The control unit compares the growth rate of the pressure value at the top of the transformer oil tank with the high growth rate alarm threshold and the low growth rate alarm threshold to determine whether the transformer is in a fault state and whether an immediate power outage is required. Furthermore, based on the increase in the oil level inside the pressure relief valve and whether a power outage is not required, the control unit determines the type of transformer fault and issues a corresponding alarm signal. The present invention can effectively improve the safety of the transformer and the entire power system.

Description

Technical Field

[0001] The present invention relates to the field of power systems, and in particular to a pressure relief valve and an oil-immersed power transformer fault detection method. Background Art

[0002] Transformer pressure relief protection is a key method for protecting transformer non-electrical quantities. When a fault occurs within the transformer, the high temperature causes the transformer oil and insulation materials to decompose, producing large amounts of gas. This rapidly increases the pressure inside the transformer tank. To prevent the tank from deforming or bursting, this pressure must be quickly released. This is where the pressure relief valve plays a crucial role. When the pressure inside the transformer tank reaches the preset tank pressure alarm value, the pressure relief valve rapidly opens, releasing the pressure within the tank and rapidly reducing the pressure. Simultaneously, when the pressure relief valve activates, its internal signal contacts connect, generating an alarm signal to notify maintenance personnel of a possible fault. When the tank pressure drops to the preset shutoff pressure, the pressure relief valve automatically closes, preventing air and moisture from entering the tank.

[0003] However, existing pressure relief valves have certain limitations. On the one hand, they can only monitor whether oil is being sprayed. Only when the transformer is spraying oil, that is, after a fault occurs, can they issue a pressure over-limit alarm, indicating that an abnormal pressure problem has occurred inside the transformer. The fault cannot be eliminated in time when the fault occurs, resulting in a significant shortening of the transformer's service life. Frequent replacement of equipment not only costs a lot of money, but also affects the stability and reliability of the power supply. On the other hand, the existing pressure relief valve relies on the top action indicator rod to trigger the sensor during the lifting process to realize the pressure over-limit alarm. However, when installing the indicator rod, due to the negligence of the operator, the indicator rod often gets stuck at the critical moment when the pressure inside the transformer exceeds the limit and needs to be rebounded, or even fails to rebound. In this way, even if the pressure relief valve has been operating normally, it still cannot issue an alarm signal, making it impossible to make a timely judgment and handle the transformer fault. Summary of the Invention

[0004] To this end, the technical problem to be solved by the present invention is to overcome the defects of the existing pressure relief valve fault monitoring lag, which leads to shortened transformer life, affects power supply stability, and the indicator rod is easily stuck and cannot give timely alarm.

[0005] In order to solve the above technical problems, the present invention provides a pressure relief valve installed on the top of an oil-immersed power transformer, comprising:

[0006] A pressure sensor is installed on the inner surface of the bottom of the pressure relief valve housing to monitor the pressure value at the top of the transformer tank;

[0007] A liquid level sensor is installed at the bottom of the sealing body formed by the sealing shell and the sealing plate, and is used to detect the amount of oil inside the pressure relief valve;

[0008] The oil injection port is provided on the side or top of the sealing body, and when the volume of the insulating oil inside the sealing body exceeds the volume carrying capacity, the insulating oil inside the sealing body is sprayed out;

[0009] The explosion-proof diaphragm is installed at the bottom opening of the pressure relief valve housing, and its lower end is connected to the top opening of the transformer tank for sealing. When the pressure value at the top of the transformer tank rises, the explosion-proof diaphragm is pushed up, and insulating oil is sprayed out from the gap between the explosion-proof diaphragm and the top opening of the transformer tank. After the insulating oil in the sealing body is sprayed out from the oil spray port, the explosion-proof diaphragm is re-connected to the transformer tank opening for sealing under the influence of its own gravity.

[0010] A control unit is electrically connected to the pressure sensor and the liquid level sensor, and is used to determine that the internal insulation of the transformer tank is faulty and issue a transformer insulation high fault alarm signal when the growth rate of the pressure value at the top of the transformer tank is greater than a high growth rate alarm threshold;

[0011] When the growth rate of the pressure value at the top of the transformer oil tank is greater than the low growth rate alarm threshold and less than or equal to the high growth rate alarm threshold, it is determined whether the growth amount of the oil level inside the pressure relief valve is greater than 0. If so, it is determined that the internal insulation of the transformer oil tank is faulty and a transformer low insulation fault alarm signal is issued. Otherwise, it is determined that the transformer breathing system is faulty and a transformer breathing obstruction alarm signal is issued.

[0012] When the growth rate of the pressure value at the top of the transformer oil tank is less than or equal to the low growth rate alarm threshold, and the growth rate of the oil level inside the pressure relief valve is greater than 0, it is determined that the explosion-proof disk in the pressure relief valve is cracked, and an explosion-proof disk crack alarm signal is issued;

[0013] An information transmission unit is connected to the control unit and the electric power dispatching control center for communicating with the control unit and reporting to the electric power dispatching control center the message "immediate power outage is required to replace the insulation components of the faulty transformer" when the control unit issues a transformer insulation high fault alarm signal;

[0014] When the control unit issues a transformer insulation low fault alarm signal, it reports to the power dispatching control center that "the insulation parts of the transformer fault part can be replaced in accordance with the power outage plan";

[0015] When the control unit issues an alarm signal that the transformer is breathing obstructed, it reports to the power dispatching control center that "it can be processed under power, and the blockage of the breather, the air holding tank, and the excessive injection of transformer insulating oil can be checked";

[0016] When the control unit sends out an alarm signal of explosion-proof membrane disc cracking, it reports to the power dispatching control center that "immediate power outage is required and the explosion-proof membrane disc must be replaced."

[0017] Preferably, the value range of the low growth rate alarm threshold is [15%, 25%], and the value range of the high growth rate alarm threshold is [55%, 65%].

[0018] Preferably, when the pressure value at the top of the transformer oil tank is greater than the oil tank pressure alarm value, it is determined that a fault exists in the transformer and an over-threshold fault alarm signal is issued.

[0019] Preferably, the fuel tank pressure alarm value is 55 kPa.

[0020] Preferably, it includes:

[0021] A pressure relief valve housing, the bottom of which is connected to the top of the transformer tank;

[0022] The spring has an upper end fixedly connected to the lower end of the sealing plate, and a lower end fixedly connected to the upper end of the explosion-proof diaphragm. When the pressure on the transformer tank is only the static pressure brought by the oil conservator, the spring is in a free expansion and contraction state. When the pressure value on the top of the transformer tank rises, the spring is subjected to the pressure of the explosion-proof diaphragm and transmits the pressure to the sealing plate.

[0023] The sealing plate has holes symmetrically arranged on both sides thereof, is inserted into the fixing screw through the holes, and slides on the fixing screw as the pressure of the spring changes;

[0024] A limit bolt is installed on the upper part of the fixing screw to prevent the sealing plate from falling off from the upper part of the fixing screw;

[0025] The sealing housing forms a sealing body with the sealing plate.

[0026] Preferably, the pressure sensor is any one of an MPM489 pressure sensor and a BMP388 pressure sensor.

[0027] Preferably, the liquid level sensor is any one of a mik-LWQ float type liquid level sensor and an E+H capacitive liquid level sensor.

[0028] The present invention also provides a method for detecting faults of an oil-immersed power transformer, which uses the above-mentioned pressure relief valve to detect faults of the oil-immersed power transformer, comprising:

[0029] Use a pressure sensor to monitor the pressure value at the top of the transformer oil tank, and use a liquid level sensor to detect the oil volume inside the pressure relief valve;

[0030] The control unit receives the pressure value at the top of the transformer oil tank and the amount of oil in the pressure relief valve. When the growth rate of the pressure value at the top of the transformer oil tank exceeds the high growth rate alarm threshold, it determines that there is an insulation fault inside the transformer oil tank, issues a transformer insulation high fault alarm signal, and reports the message "immediate power outage is required to replace the insulation parts of the faulty transformer" to the power dispatching control center through the information transmission unit.

[0031] When the growth rate of the pressure value at the top of the transformer oil tank is greater than the low growth rate alarm threshold and less than or equal to the high growth rate alarm threshold, it is determined whether the growth amount of the oil level inside the pressure relief valve is greater than 0. If so, it is determined that the internal insulation of the transformer oil tank is faulty, and a transformer insulation low fault alarm signal is issued. The information transmission unit is used to report to the power dispatching control center that "the transformer faulty part can be replaced in combination with the power outage plan." Otherwise, it is determined that the transformer breathing system is faulty, and a transformer breathing obstruction alarm signal is issued. The information transmission unit is used to report to the power dispatching control center that "the transformer breathing system can be processed under power, and the blockage of the breather, the air holding cabinet, and the excessive injection of transformer insulating oil can be checked."

[0032] When the growth rate of the pressure value at the top of the transformer oil tank is less than or equal to the low growth rate alarm threshold, and the growth rate of the oil level inside the pressure relief valve is greater than 0, it is determined that the explosion-proof membrane disc in the pressure relief valve is cracked, and an explosion-proof membrane disc cracking alarm signal is issued. The information transmission unit reports the information "Immediate power outage is required, and the explosion-proof membrane disc must be replaced" to the power dispatching control center.

[0033] Preferably, before using a pressure sensor to monitor the pressure value at the top of the transformer oil tank and using a liquid level sensor to detect the oil volume inside the pressure relief valve, fault detection of the pressure sensor and the liquid level sensor is performed, including:

[0034] Setting the duration for closing the breather valve of an oil-immersed power transformer based on the transformer's capacity rating;

[0035] The breather valve of the oil-immersed power transformer is closed for a preset time, and the pressure value at the top of the transformer tank is collected in real time using a pressure sensor, and the oil volume inside the pressure relief valve is collected in real time using a liquid level sensor;

[0036] After the pressure relief valve sprays oil, determine whether the increase in the pressure value at the top of the transformer oil tank per unit time is greater than or equal to the preset pressure increase. If so, determine that the pressure sensor is faulty and replace the pressure sensor until the increase in the pressure value at the top of the transformer oil tank per unit time measured by the pressure sensor is less than the preset pressure increase.

[0037] Determine whether the increment of the oil level inside the pressure relief valve before and after the pressure relief valve sprays oil is less than or equal to the preset liquid level increment. If so, determine that the liquid level sensor is faulty and replace the liquid level sensor until the increment of the oil level inside the pressure relief valve before and after the pressure relief valve sprays oil measured by the liquid level sensor is greater than the preset liquid level increment.

[0038] The above technical solution of the present invention has the following beneficial effects compared with the prior art:

[0039] The pressure relief valve and oil-immersed power transformer fault detection method described in the present invention can monitor the transformer oil tank pressure change state and the oil level inside the pressure relief valve in real time by arranging a pressure sensor and a liquid level sensor at the bottom of the pressure relief valve shell. Unlike the existing pressure relief valve, the pressure exceeding limit alarm can be realized only when the transformer oil tank pressure value is greater than the oil tank pressure alarm value by triggering the sensor during the lifting process of the top action indicator rod. Instead, it judges whether it is a transformer fault and whether it is necessary to apply for power outage by comparing the growth rate of the transformer oil tank top pressure value with the high growth rate alarm threshold and the low growth rate alarm threshold. The fault type is further determined by the growth rate of the oil level inside the pressure relief valve; when the growth rate of the transformer oil tank top pressure value is greater than the high growth rate alarm threshold, it is determined that the transformer is faulty. If the transformer indicates an internal tank insulation fault, an immediate power outage is required, and a transformer insulation high fault alarm is issued. When the growth rate of the transformer tank top pressure value is greater than the low growth rate alarm threshold and less than or equal to the high growth rate alarm threshold, the transformer is determined to be in a faulty state. Further, the increase in the oil level inside the pressure relief valve is determined to be greater than 0. If so, the transformer is diagnosed with an internal tank insulation fault, which can be addressed in conjunction with the power outage plan and a transformer insulation low fault alarm is issued. Otherwise, the transformer is diagnosed with a breathing system fault, requiring no power outage, and a transformer breathing obstruction alarm is issued. When the growth rate of the transformer tank top pressure value is less than or equal to the low growth rate alarm threshold, and the increase in the oil level inside the pressure relief valve is greater than 0, the explosion-proof diaphragm in the pressure relief valve is determined to be cracked, requiring a power outage and issuing a explosion-proof diaphragm crack alarm. This system can generate corresponding alarm signals in the early stages of a fault, alerting operators and maintenance personnel whether a power outage is necessary. This effectively improves the safety of the transformer and the entire power system, reducing the risk of safety accidents caused by equipment failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0041] Figure 1 It is a structural diagram of a pressure relief valve of the present invention.

[0042] Figure 2 The present invention is a flowchart of the steps of a method for detecting a fault of an oil-immersed power transformer.

[0043] Figure 3 The present invention is a flow chart of a method for detecting faults of an oil-immersed power transformer.

[0044] Explanation of the accompanying symbols: 1. Pressure relief valve housing; 2. Explosion-proof membrane disk; 3. Pressure sensor; 4. Liquid level sensor; 5. Spring; 6. Sealing plate; 7. Fixing screw; 8. Limiting bolt; 9. Sealing housing; 10. Oil injection port. DETAILED DESCRIPTION

[0045] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0046] Reference Figure 1 As shown, this embodiment provides a pressure relief valve, including:

[0047] The bottom of the pressure relief valve housing 1 is connected to the top of the transformer tank;

[0048] The explosion-proof diaphragm 2 is installed at the bottom opening of the pressure relief valve housing 1, and its lower end is connected to the top opening of the transformer tank for sealing. When the pressure value at the top of the transformer tank rises, the explosion-proof diaphragm 2 is pushed up, and the insulating oil is sprayed out from the gap between the explosion-proof diaphragm 2 and the top opening of the transformer tank; after the oil injection port 10 sprays the insulating oil inside the sealing body, the explosion-proof diaphragm 2 is affected by its own gravity to connect and seal with the transformer tank opening again;

[0049] The pressure sensor 3 is installed on the inner surface of the bottom of the pressure relief valve housing 1 and is used to monitor the pressure value at the top of the transformer tank;

[0050] The liquid level sensor 4 is installed at the bottom of the sealing body formed by the sealing shell 9 and the sealing plate 6, and is used to detect the oil level inside the pressure relief valve;

[0051] The control unit is electrically connected to the pressure sensor 3 and the liquid level sensor 4 and is used to determine that the transformer has an internal insulation fault in the oil tank when the growth rate of the pressure value at the top of the transformer oil tank is greater than the high growth rate alarm threshold, requiring immediate power outage and issuing a transformer insulation high fault alarm signal;

[0052] When the growth rate of the pressure value at the top of the transformer oil tank is greater than the low growth rate alarm threshold and less than or equal to the high growth rate alarm threshold, it is determined whether the growth amount of the oil level inside the pressure relief valve is greater than 0. If so, it is determined that the internal insulation of the transformer oil tank is faulty and a transformer low insulation fault alarm signal is issued. Otherwise, it is determined that the transformer breathing system is faulty and a transformer breathing obstruction alarm signal is issued.

[0053] When the growth rate of the pressure value at the top of the transformer oil tank is less than or equal to the low growth rate alarm threshold, and the growth rate of the oil level inside the pressure relief valve is greater than 0, it is determined that the explosion-proof disk 2 in the pressure relief valve is cracked, and a explosion-proof disk 2 crack alarm signal is issued;

[0054] The spring 5 has its upper end fixedly connected to the lower end of the sealing plate 6, and its lower end fixedly connected to the upper end of the explosion-proof disk 2. When the pressure on the transformer tank is only the static pressure brought by the oil conservator, the spring 5 is in a free expansion and contraction state. When the pressure value at the top of the transformer tank rises, the spring 5 is subjected to the pressure of the explosion-proof disk 2 and transmits the pressure to the sealing plate 6.

[0055] The sealing plate 6 has holes symmetrically provided on both sides thereof, through which the fixing screw 7 is inserted and slides on the fixing screw 7 as the pressure of the spring 5 changes;

[0056] A limiting bolt 8 is installed on the upper portion of the fixing screw 7 to prevent the sealing plate 6 from falling off from the upper portion of the fixing screw 7;

[0057] A sealing housing 9, which forms a sealing body with the sealing plate 6;

[0058] The oil injection port 10 is provided on the side or top of the sealing body, and when the volume of the insulating oil inside the sealing body exceeds the volume carrying capacity, the insulating oil inside the sealing body is sprayed out.

[0059] In this embodiment, preferably, it further includes:

[0060] An information transmission unit is connected to the control unit and the electric power dispatching control center for communicating with the control unit and reporting to the electric power dispatching control center the message "immediate power outage is required to replace the insulation components of the faulty transformer" when the control unit issues a transformer insulation high fault alarm signal;

[0061] When the control unit issues a transformer insulation low fault alarm signal, it reports to the power dispatching control center that "the insulation parts of the transformer fault part can be replaced in accordance with the power outage plan";

[0062] When the control unit issues an alarm signal that the transformer is breathing obstructed, it reports to the power dispatching control center that "it can be processed under power, and the blockage of the breather, the air holding tank, and the excessive injection of transformer insulating oil can be checked";

[0063] When the control unit sends out an alarm signal indicating that the explosion-proof membrane disc 2 is cracked, it reports to the power dispatching control center that "power outage is required immediately and the explosion-proof membrane disc needs to be replaced."

[0064] During normal operation, the pressure at the top of the transformer tank increases at a relatively steady rate. However, if the pressure growth rate exceeds the high growth rate alarm threshold, this abnormal indicator indicates significant pressure fluctuations within the transformer. Insulation failures often trigger partial discharges, causing the insulation material to decompose and produce large amounts of gas. Simultaneously, insulation breakdown short circuits generate significant heat, accelerating the decomposition and gasification of the transformer oil. These rapidly generated gases and heat accumulate within the tank, causing a sharp increase in pressure. Furthermore, thermal decomposition of the insulation material under high temperature and electric fields can further accelerate the pressure increase. A respiratory system failure is unlikely to cause such rapid and significant pressure changes, so an insulation failure is determined to be present within the transformer tank.

[0065] Existing pressure relief valves only activate when the pressure inside the transformer tank reaches the preset tank pressure alarm value, relying on the top-actuated indicator lever to trigger a sensor during its rise to provide an over-pressure alarm. However, even if the pressure inside the transformer tank does not exceed the tank pressure alarm value of 55kPa, if the pressure growth rate at the top of the transformer tank exceeds the high growth rate alarm threshold, the sudden pressure fluctuation can cause serious damage to the transformer's internal structural components. For example, excessive pressure fluctuations can subject the windings to additional mechanical stress, causing them to deform or even break, further damaging the insulation structure and expanding the scope of the fault. Furthermore, other internal components, such as the core and insulating supports, can also be damaged by the drastic pressure fluctuations, affecting the transformer's normal operation and performance.

[0066] Therefore, if the growth rate of the pressure value at the top of the transformer oil tank exceeds the high growth rate alarm threshold, it may cause the transformer to explode and catch fire, causing a large-scale power outage. The operation and maintenance personnel must immediately issue a transformer insulation high fault alarm signal. This situation indicates that there is a serious insulation fault inside the transformer oil tank, which has caused great damage to the insulation performance of the transformer. The operation and maintenance personnel should promptly request a power outage. The operation and maintenance personnel will drain the oil and then lift the cover of the transformer to identify the specific insulation fault inside the transformer, replace the insulation components in the faulty area, and then reinstall the transformer.

[0067] When the growth rate of the pressure value at the top of the transformer oil tank is greater than the low growth rate alarm threshold and less than or equal to the high growth rate alarm threshold, it indicates that a slight pressure change has occurred inside the transformer. At this time, it is crucial to accurately analyze the cause of this pressure change to determine whether it is necessary to apply for an immediate power outage or combine the treatment measures with the subsequent power outage plan.

[0068] If the growth rate of the pressure at the top of the transformer tank exceeds the low growth rate alarm threshold and is less than or equal to the high growth rate alarm threshold, and the increase in the oil level inside the pressure relief valve is greater than 0, indicating that the transformer has been exposed to oil, this indicates an internal tank insulation fault. For example, there may be a localized, minor discharge within the transformer. This discharge may be caused by minor defects in the insulation material over long-term operation, resulting in an uneven electric field distribution and, consequently, localized discharge. Although the energy generated by this discharge is relatively small, it only causes a small amount of transformer oil to decompose and produce gas, which in turn causes a slight increase in tank pressure and a small amount of insulating oil overflow. While this insulation fault may not currently significantly impact transformer operation, it should not be ignored. If not promptly addressed, these minor defects may gradually expand over time, eventually leading to a more serious insulation fault and impacting normal transformer operation. Since the fault is relatively minor, it can be addressed in conjunction with a planned power outage to ensure power supply stability and minimize user impact. Furthermore, to ensure timely monitoring of equipment status by maintenance personnel, the control unit issues a transformer low insulation fault alarm signal as a warning.

[0069] When the growth rate of the pressure at the top of the transformer tank exceeds the low growth rate alarm threshold but does not exceed the high growth rate alarm threshold, if the oil level inside the pressure relief valve increases by zero and no insulating oil overflow is detected, this indicates that the transformer is not injecting oil. In this case, the abnormal pressure change is likely caused by a problem with the transformer's breathing system. The transformer's breathing system includes components such as the oil conservator and the breather, which maintain pressure balance within the tank. Obstructions to the conservator or the breather, such as damage to the conservator capsule or blockage of the breather's desiccant, can impede gas exchange between the tank and the outside world. As the transformer operates, rising oil temperature causes the oil to expand, preventing the generated gas from properly discharging, leading to an abnormal increase in tank pressure. This type of fault caused by respiratory system problems can be handled under power, such as replacing the desiccant of the respirator, repairing the capsule of the oil conservator, etc. Therefore, the operation and maintenance personnel should be promptly reminded to deal with the breathing problem of the transformer under power. The transformer breathing obstruction is mainly caused by the transformer respirator and the oil conservator holding air, which can be handled under power. If the transformer breathing system has problems due to blockage of the respirator, the respirator should be replaced under power; if the transformer breathing system has problems due to holding air in the oil conservator, the gas in the oil conservator should be discharged under power; if the transformer breathing system has problems due to excessive injection of transformer insulating oil, the oil should be discharged under power to reduce the transformer insulating oil content to restore the normal operating state of the transformer and avoid further damage to the transformer due to continued abnormal pressure.

[0070] When the growth rate of the pressure at the top of the transformer tank is less than or equal to the low growth rate alarm threshold, this indicates that the transformer tank pressure is relatively stable and has not changed significantly. During normal operation of the transformer, the insulating oil expands and contracts due to changes in ambient temperature. When the ambient temperature rises, the insulating oil expands, causing the pressure inside the tank to rise slightly. When the ambient temperature drops, the insulating oil contracts, causing the pressure inside the tank to drop accordingly. However, the pressure fluctuations caused by this thermal expansion and contraction are limited and generally do not exceed the low growth rate alarm threshold.

[0071] In order to more comprehensively and accurately judge the operating status of the transformer, it is necessary to conduct further analysis in combination with the monitoring data of the liquid level sensor 4. If the liquid level sensor 4 does not detect the phenomenon of insulating oil overflow, this further proves that the internal pressure of the transformer remains stable and there is no abnormality. Because during normal operation and when there is no abnormal change in pressure, the pressure relief valve will not operate, and there will be no insulating oil overflow. If insulating oil overflow is detected, and the growth rate of the pressure value at the top of the transformer oil tank is less than or equal to the low growth rate alarm threshold, it means that the explosion-proof membrane disc 2 may be cracked due to its own quality problems, long-term mechanical stress or chemical corrosion, etc., thereby causing the insulating oil to leak, and then be detected by the liquid level sensor 4, which means that the explosion-proof membrane disc 2 of the pressure relief valve has cracked. By issuing an explosion-proof membrane disc 2 cracking alarm signal, the operation and maintenance personnel are reminded to promptly shut down the power supply and replace the explosion-proof membrane disc 2.

[0072] In this embodiment, specifically, the low growth rate alarm threshold The value range is [15%, 25%], the high growth rate alarm threshold The value range is [55%, 65%].

[0073] In this embodiment, preferably, the low growth rate alarm threshold is 20%, and the high growth rate alarm threshold is 60%. Setting the low growth rate alarm threshold to 20% takes into account the characteristics of pressure fluctuations during normal transformer operation and the need for early fault warning. During the daily operation of the transformer, the pressure value at the top of the oil tank will naturally fluctuate to a certain extent due to factors such as changes in ambient temperature and normal load fluctuations. After monitoring and analyzing a large amount of actual operating data, it was found that setting the low growth rate alarm threshold at 20% can not only effectively avoid the pressure fluctuation range during normal operation and avoid frequent false alarms, but also trigger an alarm in time when early signs of failure such as localized minor discharges and minor overheating appear inside the transformer, causing the pressure to begin to show an abnormal growth trend.

[0074] Setting the high growth rate alarm threshold to 60% has been verified through long-term practice and data analysis. It can achieve a good balance between accurately warning of faults, ensuring equipment safety and reducing unnecessary interference. When serious faults such as winding short circuit and large-area insulation breakdown occur inside the transformer, the pressure value at the top of the oil tank will increase rapidly and significantly. Setting the high growth rate alarm threshold to 60% can accurately define the range where the pressure growth is abnormally severe and the equipment is in a serious dangerous state. Once the pressure growth rate exceeds this threshold, it means that the internal fault of the transformer is critical, and emergency measures such as power outages must be taken immediately to avoid equipment damage and safety accidents. This is more in line with the actual needs of transformer operation monitoring and fault handling.

[0075] In this embodiment, specifically, when the pressure value at the top of the transformer oil tank is greater than the oil tank pressure alarm value of 55kPa, it is determined that there is a fault in the transformer and an over-threshold fault alarm signal is issued; the information transmission unit reports to the power dispatching control center the information that "immediate power outage is required to check for transformer insulation fault and transformer breathing system fault."

[0076] During normal operation, the top of the transformer tank is only subjected to the static pressure of the oil conservator, a value that depends on the height of the conservator. The pressure at the top of the transformer tank is typically between 20kPa and 30kPa. When pressure sensor 3 detects that the pressure at the top of the transformer tank exceeds the tank pressure alarm value of 55kPa, this data change clearly indicates that the pressure inside the transformer tank has exceeded the safe range and reached a dangerous level. There are many potential causes for increased pressure in the tank. A common one is an internal transformer fault, such as a winding short circuit. The high temperature generated by the short circuit rapidly decomposes the transformer oil and produces a large amount of gas, which in turn causes a sharp increase in tank pressure. Another possible cause is a problem with the transformer's breathing system, such as a clogged breathing valve, which prevents normal gas exchange between the tank and the outside world. As gas is generated during operation and the oil expands due to changes in oil temperature, pressure accumulates within the tank. When the pressure becomes too high, the tank may deform or burst.

[0077] Therefore, in this situation of excessive pressure, regardless of whether the pressure relief valve sprays oil, it fully demonstrates that the condition inside the transformer is extremely serious. Even if there is no oil spraying, the excessive pressure may cause irreversible damage to the transformer's insulation structure, leading to more serious failures and even major safety accidents such as equipment explosions. Therefore, once this situation is detected, the control unit must issue an over-threshold fault alarm signal, immediately notifying the operation and maintenance personnel of the extremely serious transformer fault. The operation and maintenance personnel should promptly request a power outage from the higher authorities to conduct a comprehensive inspection and repair of the transformer, prevent further deterioration of the fault, and ensure the safe and stable operation of the power system.

[0078] In this embodiment, specifically, the formula for the growth rate of the pressure value at the top of the fuel tank is:

[0079] ,

[0080] in, for The growth rate of the pressure value at the top of the tank at the moment, for The pressure value at the top of the fuel tank at that moment, for The pressure value at the top of the fuel tank at that moment.

[0081] In this embodiment, specifically, when the pressure on the transformer oil tank is only the static pressure brought by the oil conservator, the spring 5 is in a free expansion and contraction state, and the sealing plate 6 and the sealing housing 9 together form a seal to prevent external moisture from entering;

[0082] When a fault occurs inside the transformer, the pressure at the top of the transformer tank increases, the explosion-proof disk 2 is pushed upward, and the spring 5, under the pressure of the explosion-proof disk 2, transmits the pressure to the sealing plate 6. When the pressure value at the top of the tank is greater than or equal to the tank pressure alarm value, the sealing plate 6 is pushed upward under the action of the spring 5, and the insulating oil is ejected from the gap between the explosion-proof disk 2 and the opening at the top of the transformer tank. When the volume of the insulating oil inside the sealing shell 9 exceeds the volume carrying capacity, the insulating oil inside the sealing shell is ejected from the oil injection port 10.

[0083] After the insulating oil is sprayed out, the pressure on the top of the transformer tank drops, and the explosion-proof membrane disc 2 is affected by its own gravity to re-dock and seal with the opening of the transformer tank. The explosion-proof membrane disc 2 drives the spring 5 to pull back the sealing plate 6, and the sealing plate 6 and the sealing shell 9 form a sealed body again.

[0084] In this embodiment, specifically, the pressure sensor 3 is any one of an MPM489 pressure sensor and a BMP388 pressure sensor.

[0085] In this embodiment, specifically, the liquid level sensor 4 is any one of a mik-LWQ float type liquid level sensor and an E+H capacitive type liquid level sensor.

[0086] This application can promptly detect abnormal increases or decreases in transformer pressure through real-time monitoring of the pressure value at the top of the oil tank, providing key pressure dimension information for the equipment's operating status. Combining the pressure value at the top of the oil tank and the amount of oil inside the pressure relief valve body to generate different alarm signals can achieve more comprehensive and accurate monitoring of the equipment's operating status, helping operation and maintenance personnel quickly locate the root cause of the problem and distinguish between pressure-related faults and faults in the pressure relief valve itself, so that targeted and effective measures can be taken in a timely manner to avoid missing potential risks due to the limitations of a single monitoring indicator, significantly improving the safety and reliability of equipment operation, reducing the probability of equipment damage and accidents, and ensuring the stable operation of the system.

[0087] refer to Figure 2 、 Figure 3 As shown, Figure 2 This is a flow chart of the steps of a method for detecting a fault of an oil-immersed power transformer according to the present invention. Figure 3 The present invention is a flow chart of a method for detecting faults of an oil-immersed power transformer.

[0088] The second embodiment provides a method for detecting faults of an oil-immersed power transformer, which uses the pressure relief valve to detect faults of the oil-immersed power transformer, including:

[0089] Step S1: Using the pressure sensor 3 to monitor the pressure value at the top of the transformer oil tank, and using the liquid level sensor 4 to detect the oil volume inside the pressure relief valve;

[0090] Step S2: receiving the pressure value at the top of the transformer oil tank and the oil volume inside the pressure relief valve through the control unit;

[0091] Step S3: When the growth rate of the pressure value at the top of the transformer oil tank is greater than the high growth rate alarm threshold, it is determined that there is an insulation fault inside the transformer oil tank, and a transformer insulation high fault alarm signal is issued;

[0092] Step S4: When the growth rate of the pressure value at the top of the transformer oil tank is greater than the low growth rate alarm threshold and less than or equal to the high growth rate alarm threshold, determine whether the growth amount of the oil level inside the pressure relief valve is greater than 0. If so, it is determined that the internal insulation of the transformer oil tank is faulty and a transformer low insulation fault alarm signal is issued; otherwise, it is determined that the transformer breathing system is faulty and a transformer breathing obstruction alarm signal is issued;

[0093] Step S5: When the growth rate of the pressure value at the top of the transformer oil tank is less than or equal to the low growth rate alarm threshold, and the growth rate of the oil level inside the pressure relief valve is greater than 0, it is determined that the explosion-proof membrane disc 2 in the pressure relief valve is cracked, and an explosion-proof membrane disc 2 cracking alarm signal is issued.

[0094] In this embodiment, preferably, before using the pressure sensor 3 to monitor the pressure value at the top of the transformer oil tank and using the liquid level sensor 4 to detect the oil level inside the pressure relief valve, fault detection of the pressure sensor 3 and the liquid level sensor 4 is performed, including:

[0095] Setting the duration for closing the breather valve of an oil-immersed power transformer based on the transformer's capacity rating;

[0096] The breather valve of the oil-immersed power transformer is closed for a preset time, and the pressure value at the top of the transformer tank is collected in real time using the pressure sensor 3, and the oil level inside the pressure relief valve is collected in real time using the liquid level sensor 4;

[0097] After the pressure relief valve sprays oil, determine whether the increase in the pressure value at the top of the transformer oil tank per unit time is greater than or equal to the preset pressure increase. If so, determine that the pressure sensor 3 is faulty and replace the pressure sensor 3 until the increase in the pressure value at the top of the transformer oil tank per unit time measured by the pressure sensor 3 is less than the preset pressure increase.

[0098] Determine whether the increment of the oil level inside the pressure relief valve before and after the pressure relief valve sprays oil is less than or equal to the preset liquid level increment. If so, determine that the liquid level sensor 4 is faulty, and replace the liquid level sensor 4 until the increment of the oil level inside the pressure relief valve before and after the pressure relief valve sprays oil measured by the liquid level sensor 4 is greater than the preset liquid level increment.

[0099] By pre-detecting sensor failures, data anomalies caused by sensor failures can be avoided, thereby ensuring that the collected pressure value at the top of the transformer tank and the oil level inside the pressure relief valve are true and reliable, providing an accurate basis for subsequent transformer fault diagnosis.

[0100] The patent of the present invention is practical and simple. By arranging a pressure sensor 3 and a liquid level sensor 4 inside the pressure relief valve, it can monitor the pressure change status of the transformer oil tank and the amount of insulating oil sprayed inside the pressure relief valve in real time. The pressure data and the amount of oil inside the pressure relief valve are used to provide differentiated early warning strategies for operation and maintenance personnel, which can effectively protect the safe and stable operation of the equipment.

[0101] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present application may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0102] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0103] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0104] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0105] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A pressure relief valve installed on the top of an oil-immersed power transformer, characterized in that: include: A pressure sensor is installed on the inner surface of the bottom of the pressure relief valve housing to monitor the pressure value at the top of the transformer tank; A liquid level sensor is installed at the bottom of the sealing body formed by the sealing shell and the sealing plate, and is used to detect the amount of oil inside the pressure relief valve; The oil injection port is provided on the side or top of the sealing body, and when the volume of the insulating oil inside the sealing body exceeds the volume carrying capacity, the insulating oil inside the sealing body is sprayed out; The explosion-proof diaphragm is installed at the bottom opening of the pressure relief valve housing, and its lower end is connected to the top opening of the transformer tank for sealing. When the pressure value at the top of the transformer tank rises, the explosion-proof diaphragm is pushed up, and insulating oil is sprayed out from the gap between the explosion-proof diaphragm and the top opening of the transformer tank. After the insulating oil in the sealing body is sprayed out from the oil spray port, the explosion-proof diaphragm is re-connected to the transformer tank opening for sealing under the influence of its own gravity. A control unit is electrically connected to the pressure sensor and the liquid level sensor, and is used to determine that the internal insulation of the transformer tank is faulty and issue a transformer insulation high fault alarm signal when the growth rate of the pressure value at the top of the transformer tank is greater than a high growth rate alarm threshold; When the growth rate of the pressure value at the top of the transformer oil tank is greater than the low growth rate alarm threshold and less than or equal to the high growth rate alarm threshold, it is determined whether the growth amount of the oil level inside the pressure relief valve is greater than 0. If so, it is determined that the internal insulation of the transformer oil tank is faulty and a transformer low insulation fault alarm signal is issued. Otherwise, it is determined that the transformer breathing system is faulty and a transformer breathing obstruction alarm signal is issued. When the growth rate of the pressure value at the top of the transformer oil tank is less than or equal to the low growth rate alarm threshold, and the growth rate of the oil level inside the pressure relief valve is greater than 0, it is determined that the explosion-proof disk in the pressure relief valve is cracked, and an explosion-proof disk crack alarm signal is issued; An information transmission unit, which is in communication with the control unit and the electric power dispatching control center, is used to report to the electric power dispatching control center the need for immediate power outage and replacement of insulation components at the faulty transformer location when the control unit issues a transformer insulation high fault alarm signal; When the control unit issues a transformer insulation low fault alarm signal, it reports to the power dispatching control center that "the insulation components at the faulty part of the transformer can be replaced in accordance with the power outage plan." When the control unit issues a transformer breathing obstruction alarm signal, it reports to the power dispatching control center that "live processing is possible, check for blockage of the breather, air holding back in the oil conservator, and excessive injection of transformer insulating oil"; When the control unit sends out an alarm signal indicating that the transformer explosion-proof diaphragm is cracked, it reports to the power dispatching control center that "power outage is required immediately and the explosion-proof diaphragm needs to be replaced." 2. A pressure relief valve according to claim 1, characterized in that: The value range of the low growth rate alarm threshold is [15%, 25%], and the value range of the high growth rate alarm threshold is [55%, 65%].

3. A pressure relief valve according to claim 1, characterized in that: When the pressure value at the top of the transformer oil tank is greater than the oil tank pressure alarm value, it is determined that the transformer is faulty and an over-threshold fault alarm signal is issued.

4. A pressure relief valve according to claim 3, characterized in that: The fuel tank pressure alarm value is 55kPa.

5. A pressure relief valve according to claim 1, characterized in that: include: A pressure relief valve housing, the bottom of which is connected to the top of the transformer tank; The spring has an upper end fixedly connected to the lower end of the sealing plate, and a lower end fixedly connected to the upper end of the explosion-proof diaphragm. When the pressure on the transformer tank is only the static pressure brought by the oil conservator, the spring is in a free expansion and contraction state. When the pressure value on the top of the transformer tank rises, the spring is subjected to the pressure of the explosion-proof diaphragm and transmits the pressure to the sealing plate. The sealing plate has holes symmetrically arranged on both sides thereof, is inserted into the fixing screw through the holes, and slides on the fixing screw as the pressure of the spring changes; A limit bolt is installed on the upper part of the fixing screw to prevent the sealing plate from falling off from the upper part of the fixing screw; The sealing housing forms a sealing body with the sealing plate.

6. A pressure relief valve according to claim 1, characterized in that: The pressure sensor is any one of an MPM489 pressure sensor and a BMP388 pressure sensor.

7. A pressure relief valve according to claim 1, characterized in that: The liquid level sensor is any one of a mik-LWQ float type liquid level sensor and an E+H capacitive liquid level sensor.

8. A method for detecting faults in an oil-immersed power transformer, characterized in that: Detecting faults of an oil-immersed power transformer using the pressure relief valve according to any one of claims 1 to 7 comprises: Use a pressure sensor to monitor the pressure value at the top of the transformer oil tank, and use a liquid level sensor to detect the oil volume inside the pressure relief valve; The control unit receives the pressure value at the top of the transformer tank and the amount of oil in the pressure relief valve. When the growth rate of the pressure value at the top of the transformer tank exceeds the high growth rate alarm threshold, it determines that there is an insulation fault inside the transformer tank and issues a transformer insulation high fault alarm signal. The information transmission unit then reports to the power dispatching control center that "immediate power outage is required to replace the insulation components at the faulty transformer location." When the growth rate of the pressure value at the top of the transformer oil tank is greater than the low growth rate alarm threshold and less than or equal to the high growth rate alarm threshold, it is determined whether the growth amount of the oil level inside the pressure relief valve is greater than 0. If so, it is determined that the internal insulation of the transformer oil tank is faulty, and a transformer insulation low fault alarm signal is issued. The information transmission unit is used to report to the power dispatching control center that "the transformer faulty part can be replaced in accordance with the power outage plan." Otherwise, it is determined that the transformer breathing system is faulty, and a transformer breathing obstruction alarm signal is issued. The information transmission unit is used to report to the power dispatching control center that "the transformer breathing system can be handled under power, and the blockage of the breather, the air conservator, and the excessive injection of transformer insulating oil can be checked." When the growth rate of the pressure value at the top of the transformer oil tank is less than or equal to the low growth rate alarm threshold, and the growth rate of the oil level inside the pressure relief valve is greater than 0, it is determined that the explosion-proof disk in the pressure relief valve is cracked, and an explosion-proof disk cracking alarm signal is issued. The information transmission unit reports the message "Immediate power outage is required to replace the explosion-proof disk" to the power dispatching control center.

9. The method for detecting faults of an oil-immersed power transformer according to claim 8, wherein: Before using a pressure sensor to monitor the pressure value at the top of the transformer tank and using a liquid level sensor to detect the oil volume inside the pressure relief valve, perform fault detection on the pressure sensor and liquid level sensor, including: Setting the duration for closing the breather valve of an oil-immersed power transformer based on the transformer's capacity rating; The breather valve of the oil-immersed power transformer is closed for a preset time, and the pressure value at the top of the transformer tank is collected in real time using a pressure sensor, and the oil volume inside the pressure relief valve is collected in real time using a liquid level sensor; After the pressure relief valve sprays oil, determine whether the increase in the pressure value at the top of the transformer oil tank per unit time is greater than or equal to the preset pressure increase. If so, determine that the pressure sensor is faulty and replace the pressure sensor until the increase in the pressure value at the top of the transformer oil tank per unit time measured by the pressure sensor is less than the preset pressure increase. Determine whether the increment of the oil level inside the pressure relief valve before and after the pressure relief valve sprays oil is less than or equal to the preset liquid level increment. If so, determine that the liquid level sensor is faulty and replace the liquid level sensor until the increment of the oil level inside the pressure relief valve before and after the pressure relief valve sprays oil measured by the liquid level sensor is greater than the preset liquid level increment.

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