Device and method for testing sealing performance of transformer

Abstract

The invention relates to the technical field of transformer sealing test, provides a transformer sealing test device and method, and aims to reduce the construction difficulty, save human resources and reduce the operation risk. According to the device, a traditional inflation method is abandoned, the oil pressure of the transformer body is used for replacing gas static pressure for sealing detection, and the safety and reliability of the test are improved. The device has a transformer oil injection function and a real-time oil pressure monitoring capability, can automatically close the electromagnetic valve and stop oil injection when the pressure reaches a set value or is abnormal, and keeps a constant pressure state for 24 hours so as to judge the sealing performance of the transformer. The device structurally comprises an oil tank, an oil pump, a connecting tool, a pressure sensor and a plurality of electromagnetic valves, and efficient oil circulation and pressure adjustment are ensured. According to the method, through a series of steps including oil storage, bubble removal, constant-pressure maintenance and sealing performance detection, the standardization and accuracy of test operation are ensured, and finally high test performance and stability are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of transformer sealing test, in particular to a transformer sealing test device and method. Background Art

[0002] Oil-immersed power transformers are important equipment in power systems. Their main function is to achieve conversion between high voltage and low voltage to meet different power needs. Oil-immersed power transformers often adopt an oil-immersed structure. The oil not only acts as an insulator, but also effectively cools the electrical components inside the transformer to ensure its safe operation under high load conditions.

[0003] According to the countermeasures requirements and relevant maintenance test procedures of the Southern Power Grid, oil-immersed transformers need to undergo a sealing test after installation and maintenance to ensure the reliability of the equipment during operation. The sealing test can effectively detect whether there is oil leakage in the transformer, thereby avoiding equipment failure and environmental pollution caused by oil leakage.

[0004] According to the "DL / T 264-2012 Guidelines for Field Sealing Test of Oil-immersed Power Transformers (Reactors)", the sealing test of oil-immersed transformers mainly includes vacuum sealing test and positive pressure sealing test. The vacuum sealing test requires the installation of a process oil storage cabinet on the transformer cover, and the sealing is tested by applying a certain positive pressure (usually 30kPa) by inputting nitrogen or dry air with a dew point not higher than -40℃ from the breathing port of the oil storage cabinet. Although this process is effective, it also has many limitations.

[0005] Specifically, during the sealing test, the construction personnel need to close the connecting valve between the oil storage cabinet and the transformer body after the vacuum oil filling, install the process oil storage cabinet and adjust its height to the same as the original oil storage cabinet. The construction is difficult and consumes human resources. In addition, the process oil storage cabinet is difficult to operate and has certain operational risks.

[0006] Based on this, the present invention provides a transformer sealing test device and method to reduce construction difficulty, save human resources, and reduce operation risks. Summary of the invention

[0007] The purpose of the present invention is to solve the deficiencies of the prior art and provide a transformer sealing test device and method to reduce the construction difficulty, save human resources, and reduce the risk of operation. Abandoning the traditional inflation method, the transformer body oil pressure is used instead of the gas static pressure to detect the transformer sealing. The device can not only realize the function of oil filling the transformer body, but also monitor the transformer body oil pressure in real time. When the pressure reaches the set value or the pressure is abnormal, the solenoid valve is closed, the oil filling is automatically stopped, and it starts to maintain for 24 hours. The quality of the transformer sealing performance is judged according to the test results. The test device saves costs, is simple to operate, and has stable test performance.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A transformer sealing test device comprises: an oil tank, an oil pump, a connecting tool, a pressure sensor, a plurality of solenoid valves and correspondingly arranged oil outlet pipelines and oil return pipelines;

[0010] The oil inlet of the oil tank is connected to the oil outlet pipe of the transformer oil pillow through a connecting pipe, the oil outlet of the oil tank is connected to the oil inlet of the oil pump through an oil outlet pipeline, the oil outlet of the oil pump is connected to the connecting tool through an oil outlet pipeline, the connecting tool is connected to the bottom of the transformer body, and the connecting tool is respectively connected to the oil outlet pipe of the transformer oil pillow and the oil inlet of the oil tank through an oil return pipeline; the circuit formed by the connecting tool and the oil outlet pipe of the transformer oil pillow is a pressure regulating circuit; the top of the oil tank is connected to the first solenoid valve, and the other end of the first solenoid valve is connected to the vacuum pump;

[0011] A second solenoid valve is provided between the oil tank inlet and the oil outlet pipe of the transformer oil conservator; a third solenoid valve is provided between the oil pump outlet and the connecting tool; a fourth solenoid valve is provided between the connecting tool and the oil tank inlet; a fifth solenoid valve is provided between the connecting tool and the oil outlet pipe of the transformer oil conservator;

[0012] The transformer body is connected to the connecting tooling through a transformer bottom valve; a pressure sensor is provided between the connecting tooling and the transformer body; the oil pump, oil tank and all electric valves are electrically connected to the control system.

[0013] Preferably, a first self-sealing joint is provided between the oil outlet pipe of the transformer oil pillow and the second solenoid valve; a fourth self-sealing joint is provided between the third solenoid valve and the connecting tooling; and a second self-sealing joint is provided between the connecting tooling and the fourth solenoid valve.

[0014] Preferably, a transformer oil return regulating valve is provided between the connecting tooling and the fifth solenoid valve; and a third self-sealing joint is provided between the transformer oil return regulating valve and the connecting tooling.

[0015] Preferably, a first one-way valve is provided between the oil outlet of the oil pump and the third solenoid valve, and a second one-way valve is provided between the third solenoid valve and the connecting tooling.

[0016] Preferably, a Y-type filter is provided between the second solenoid valve and the oil inlet of the oil tank.

[0017] Preferably, the oil tank has a capacity of 5-7L, and is provided with a liquid level gauge and a vacuum gauge, wherein the liquid level gauge is divided into a middle liquid level gauge and a low liquid level gauge.

[0018] Preferably, the oil tank is provided with a safety valve and a pressure switch connected to the third solenoid valve.

[0019] Preferably, the control system has an alarm function while controlling the on and off of each solenoid valve and adjusting to maintain a constant pressure.

[0020] Another object of the present invention is to provide a method for performing a transformer sealing test using the above-mentioned transformer sealing test device, comprising the following steps:

[0021] S1. First, set the transformer oil pressure value, oil supply differential pressure, oil tank level value, vacuum degree and test time required for the test in the control system, set all valves to the closed state, and close the transformer gas relay valve;

[0022] S2, storing oil, opening the second solenoid valve, the first solenoid valve and the vacuum pump, sucking the oil in the transformer oil pillow into the oil tank, and when the oil in the oil tank reaches the set middle liquid level, closing the second solenoid valve to stop the oil intake;

[0023] S3, circulating to eliminate bubbles, closing the second solenoid valve, opening the third solenoid valve and the fourth solenoid valve, and turning on the oil pump, so that the oil in the oil tank fills the corresponding pipeline, and the oil in the oil tank is internally circulated in the pipeline to defoam the oil. If the oil in the oil tank is lower than the set low liquid level during this process, the second solenoid valve is opened to allow oil to flow in until the oil in the oil tank reaches the set middle liquid level, and the second solenoid valve is closed, and circulating again to eliminate bubbles;

[0024] S4, maintain constant pressure, open the transformer bottom valve and transformer oil return regulating valve, increase the oil pressure inside the transformer, and maintain the transformer body pressure constant. If the pressure sensor detects that the pressure value is lower than the set pressure, the oil pump will start to inject oil. If the pressure sensor detects that the pressure value is higher than the set pressure, the oil pump will stop working. At the same time, the fifth solenoid will open to return the oil to the transformer oil pillow.

[0025] S5. Check the pressure tightness of the transformer. After maintaining constant pressure for 24 hours, check whether the transformer body has oil leakage and whether the oil pressure can be maintained stable.

[0026] S6. After the test is completed, close the transformer bottom valve, the first solenoid valve, and the fourth solenoid valve, open the fifth solenoid valve, the third solenoid valve, and the oil pump, and inject the oil in the oil tank, the oil outlet pipeline, and the oil return pipeline back into the transformer oil pillow, waiting for the next sealing test.

[0027] The present invention discloses a transformer sealing test device and method having the following beneficial effects.

[0028] 1. Reduce construction difficulty. The present invention abandons the traditional inflation method and adopts the oil pressure of the transformer body instead of the gas static pressure to perform the sealing test. By directly using the oil pressure for the test, the use of gas is avoided and the test process is simplified.

[0029] 2. Save human resources. Due to the high degree of automation of this device, multiple links in the test process can be automatically managed through the control system, and the staff can supervise under the monitoring system, thereby effectively saving human resources and greatly reducing dependence on manual operation.

[0030] 3. Reduce operational risks. When the present invention uses oil pressure to perform a sealing test, a pressure regulating circuit is set up to maintain a constant pressure mode. In the event of abnormal pressure, the oil injection can be stopped in time and the oil can be returned to the transformer oil pillow in time, thereby reducing the operational risks caused by equipment failure or operational errors and improving operational safety.

[0031] 4. Improve the test accuracy. The pressure sensor and control system integrated in the device can monitor the oil pressure inside the transformer in real time and can accurately detect the oil pressure changes. In addition, the oil in the storage tank is circulated internally under the action of the vacuum pump, oil pump and various solenoid valves to achieve the purpose of defoaming, which can further ensure the test accuracy. The reliability and accuracy of the test results can be improved, making the sealing detection more effective.

[0032] 5. Easy to maintain and manage, the device of the present invention is equipped with a liquid level meter and a vacuum meter to monitor the liquid level and vacuum degree of the oil tank in real time. At the same time, the setting of the safety valve and pressure switch also enhances the safety and convenience of the equipment.

[0033] 6. Cost saving: by optimizing the test process and improving the automation level of the equipment, the present invention significantly reduces the manpower and material costs in the test process. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The present invention is a process flow chart of the transformer sealing test device.

[0035] Figure 2 It is a partial control loop principle diagram of the present invention.

[0036] Figure 3It is a partial control loop principle diagram of the present invention.

[0037] Figure 4 It is a partial control loop principle diagram of the present invention.

[0038] Figure 5 The control principle diagram of the transformer sealing test device working for the present invention.

[0039] In the attached figure: 1, oil tank; 2, connecting tooling; M1, vacuum pump; M2, oil pump; PT, pressure sensor; YV1, first solenoid valve; YV2, second solenoid valve; YV3, third solenoid valve; YV4, fourth solenoid valve; YV5, fifth solenoid valve; V1, transformer return oil regulating valve; V2, transformer bottom valve; CV1, first one-way valve; CV2, second one-way valve; VF1, first self-sealing joint; VF2, second self-sealing joint; VF3, third self-sealing joint; VF4, fourth self-sealing joint; CF1, Y-type filter; PI1, vacuum gauge; SL1, low liquid level gauge; SL2, middle liquid level gauge; PS1, pressure switch; RV1, safety valve; QF1, first circuit breaker; QF2, second circuit breaker; KA1, first relay; KA2, second relay; A1, frequency converter. DETAILED DESCRIPTION

[0040] In order to explain in detail the possible application scenarios, technical principles, specific schemes that can be implemented, and the purposes and effects that can be achieved, the following is a detailed description of the specific embodiments listed in conjunction with the accompanying drawings. The embodiments described herein are only used to more clearly illustrate the technical solutions of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0041] Reference to "embodiment" herein means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The term "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or association with other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the various technical features mentioned in the embodiments can be combined in any way to form a corresponding implementable technical solution.

[0042] Unless otherwise defined, the technical terms used in this document have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms in this document is only for describing specific embodiments and is not intended to limit this application.

[0043] In the description of this application, the term "and / or" is an expression used to describe the logical relationship between objects, indicating that three relationships may exist, for example, A and / or B, which means: A exists, B exists, and A and B exist at the same time. In addition, the character " / " in this article generally indicates that the objects before and after are in an "or" logical relationship.

[0044] Without further limitations, in this application, the words "include", "comprises", "has" or other similar expressions used in the sentences are intended to cover non-exclusive inclusion. These expressions do not exclude the presence of additional elements in the process, method or product including the elements, so that the process, method or product including a series of elements may include not only those limited elements, but also other elements not explicitly listed, or also include elements inherent to such process, method or product.

[0045] Unless otherwise expressly specified or limited, in the description of the embodiments of the present application, the terms such as "install", "connect", "connect", "fix", "set", etc. used should be understood in a broad sense. For example, the "connection" can be a fixed connection, a detachable connection, or an integrated setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. For technicians in the technical field to which the present application belongs, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0046] Example 1

[0047] Please refer to Figure 1 , a transformer sealing test device, comprising: an oil tank 1, an oil pump M2, a connecting tool 2, a pressure sensor PT, a plurality of solenoid valves and correspondingly arranged oil outlet pipelines and oil return pipelines;

[0048] The oil inlet of the oil tank 1 is connected to the oil outlet pipe of the transformer oil pillow through a connecting pipe, the oil outlet of the oil tank 1 is connected to the oil inlet of the oil pump M2 through an oil outlet pipeline, the oil outlet of the oil pump M2 is connected to the connecting fixture 2 through an oil outlet pipeline, the connecting fixture 2 is connected to the bottom of the transformer body, and the connecting fixture 2 is respectively connected to the oil outlet pipe of the transformer oil pillow and the oil inlet of the oil tank 1 through an oil return pipeline; the circuit formed by the connecting fixture 2 and the oil outlet pipe of the transformer oil pillow is a pressure regulating circuit; the top of the oil tank 1 is connected to the first solenoid valve YV1, and the other end of the first solenoid valve YV1 is connected to the vacuum pump M1;

[0049] A second solenoid valve YV2 is provided between the oil inlet of the oil tank 1 and the oil outlet pipe of the transformer oil conservator; a third solenoid valve YV3 is provided between the oil outlet of the oil pump M2 and the connecting fixture 2; a fourth solenoid valve YV4 is provided between the connecting fixture 2 and the oil inlet of the oil tank 1; a fifth solenoid valve YV5 is provided between the connecting fixture 2 and the oil outlet pipe of the transformer oil conservator;

[0050] The transformer body is connected to the connecting tool 2 through the transformer bottom valve V2; a pressure sensor PT is provided between the connecting tool 2 and the transformer body; the oil pump M2, the oil tank 1 and all the electric valves are electrically connected to the control system, which can realize the sealing test of the transformer body. The pressure sensor PT is used to monitor the pressure of the test transformer. According to the monitored pressure, the control system of the device controls the on-off and adjustment of each solenoid valve, and performs oil replenishment and oil discharge to maintain constant pressure. The oil pressure inside the transformer is monitored in real time through the pressure sensor PT to ensure that the sealing test is carried out within the set pressure range.

[0051] A first self-sealing joint VF1 is provided between the oil outlet pipe of the transformer oil pillow and the second solenoid valve YV2; a fourth self-sealing joint VF4 is provided between the third solenoid valve YV3 and the connecting tool 2; a second self-sealing joint VF2 is provided between the connecting tool 2 and the fourth solenoid valve YV4.

[0052] A transformer oil return regulating valve V1 is provided between the connecting tooling 2 and the fifth solenoid valve YV5; that is, a transformer oil return regulating valve V1 is provided on the pressure regulating circuit, and a third self-sealing joint VF3 is provided between the transformer oil return regulating valve V1 and the connecting tooling 2. The function of this circuit is to automatically adjust the pressure of the transformer body. When the transformer body exceeds the set pressure, the oil automatically returns to the transformer oil pillow to maintain a constant pressure mode.

[0053] A first one-way valve CV1 is provided between the oil outlet of the oil pump M2 and the third solenoid valve YV3 , and a second one-way valve CV2 is provided between the third solenoid valve YV3 and the connecting tooling 2 .

[0054] A Y-type filter CF1 is provided between the second solenoid valve YV2 and the oil inlet of the oil tank 1. The Y-type filter CF1 filters dirt and impurities in the transformer oil to ensure the purity of the oil, extend the service life of the equipment and reduce maintenance costs.

[0055] Example 2

[0056] Please refer to Figure 1Based on Example 1, this embodiment provides an oil tank 1 of a transformer sealing test device, the top of the oil tank 1 is connected to the first electromagnetic valve YV1, and the other end of the first electromagnetic valve YV1 is connected to the vacuum pump M1; the oil tank 1 has a volume of 5-7L, and a liquid level gauge and a vacuum gauge PI1 are provided on the oil tank 1. The liquid level gauge is divided into a middle liquid level gauge SL2 and a low liquid level gauge SL1. The detection volume of the low liquid level gauge SL1 is 1L, and the detection volume of the middle liquid level gauge SL2 is 3L. The flow rate of the oil pump M2 is 0.5-4L / min.

[0057] The oil tank 1 is equipped with a safety valve RV1 and a pressure switch PS1 connected to the third solenoid valve YV3. The safety valve RV1 and pressure switch PS1 configured on the oil tank 1 can timely monitor the pressure changes inside the oil tank 1 to prevent overpressure and potential safety hazards;

[0058] The design of the first solenoid valve YV1 and the vacuum pump M1 connected to the top of the oil tank 1 enables the oil tank 1 to quickly extract air and maintain the vacuum state of the oil. The vacuum pump M1 is started and stopped by the vacuum gauge PI1. The vacuum degree range is -0.05-0.08mpa. The vacuum pump M1 adopts the commercially available HP-550. The liquid level gauges (middle liquid level gauge SL2 and low liquid level gauge SL1) equipped on the oil tank 1 can monitor the liquid level of the oil in real time to ensure that the appropriate amount of oil is always maintained during the test.

[0059] The control system not only controls the on / off of each solenoid valve and adjusts to maintain constant pressure, but also has an alarm function. It can issue an alarm in time when the liquid level is too low or the pressure is abnormal, reminding the operator to take necessary measures. The control system uses Siemens series PLC. When the liquid level is lower than the low level, the second solenoid valve YV2 is opened; when the liquid level is higher than the medium level, the second solenoid valve YV2 is closed.

[0060] Example 3

[0061] Please refer to Figures 2 to 4 Based on Examples 1 to 2, this embodiment provides a control loop; the control loop includes: a vacuum pump M1 control loop, an oil pump M2 control loop, and a PLC control panel power supply; the control loop integrates the control functions of the vacuum pump M1 and the oil pump M2, and realizes highly automated management through the PLC control panel, reduces manual intervention, and improves operational efficiency.

[0062] The control circuit of the vacuum pump M1 includes the first circuit breaker QF1, the first relay KA1, the first solenoid valve YV1, and the vacuum pump M1. When the first circuit breaker QF1 is closed, the first relay KA1 is energized, the first solenoid valve YV1 is opened, and the vacuum pump M1 operates;

[0063] The oil pump M2 control circuit includes the second circuit breaker QF2, the frequency converter A1, and the oil pump M2. When the second circuit breaker QF2 is closed, the frequency converter A1 is powered, and the oil pump M2 is running. The function of the frequency converter A1 is to adjust the speed of the oil pump M2, and then adjust the oil flow rate to achieve constant pressure. The frequency converter A1 adopts the commercially available Schneider series; the incoming line also includes a fuse to play the role of current limiting protection. The frequency converter A1 used in the oil pump M2 control circuit allows the speed of the oil pump M2 to be flexibly adjusted, thereby accurately controlling the oil flow rate and achieving constant pressure.

[0064] The control switches on the control panel include: pressure switch PS1, low liquid level gauge SL1, middle liquid level gauge SL2, inverter A1 fault, vacuum gauge; first relay KA1 control, vacuum pump M1 control, second relay KA2 oil pump M2 control, second solenoid valve YV2 control, third solenoid valve YV3 control, fourth solenoid valve YV4 control, fifth solenoid valve YV5 control switch, which can realize oil outlet pressure monitoring, low liquid level stop oil discharge, middle liquid level stop oil intake, inverter A1 fault alarm, vacuum degree detection, vacuum pump M1 control, oil pump M2 control, second solenoid valve YV2, third solenoid valve YV3, fourth solenoid valve YV4, fifth solenoid valve YV5 control functions. The pressure sensor PT, liquid level gauge and fault alarm function on the control panel enable the equipment to monitor the pressure and liquid level status of the oil in real time.

[0065] The control panel includes a pressure sensor PT, which can realize pressure data transmission and monitoring.

[0066] By integrating the control functions of vacuum pump M1 and oil pump M2, a high degree of automated management is achieved, manual intervention is reduced, and operational efficiency is improved. The frequency converter A1 used in the control loop of oil pump M2 allows the speed of oil pump M2 to be flexibly adjusted to accurately control the oil flow rate and ensure constant pressure, thereby improving the accuracy and reliability of the test. The integrated fuse and pressure switch PS1 provide effective current limiting and overpressure protection for the system to ensure the safety of equipment and operators. The pressure sensor PT and liquid level gauge on the control panel enable the equipment to monitor the status of the oil in real time, quickly feedback and issue alarms to reduce potential risks. Multifunctional control allows the realization of functions such as oil outlet pressure monitoring, stopping oil discharge at low liquid level, stopping oil inlet at medium liquid level, and frequency converter A1 fault alarm, which improves operational flexibility and adaptability. The well-known brand products selected in the control loop enhance the stability and reliability of the system and improve the overall performance and service life of the equipment.

[0067] The design of this control loop not only improves the automation level and operating efficiency of the transformer sealing test device, but also ensures the safety and accuracy of the test process through multiple protection mechanisms and real-time monitoring functions, providing users with a more efficient and economical solution.

[0068] Example 4

[0069] Please refer to Figure 5 Based on Examples 1-3, this embodiment provides a transformer sealing test method, comprising the following steps:

[0070] S1. First, set the transformer oil pressure value, oil supply differential pressure, oil tank 1 liquid level value, vacuum degree and test time required for the test in the control system, set all valves to the closed state, and close the transformer gas relay valve;

[0071] S2, to store oil, open the second solenoid valve YV2, the first solenoid valve YV1 and the vacuum pump M1, and suck the oil in the transformer oil pillow into the oil tank 1. When the oil in the oil tank 1 reaches the set middle liquid level, close the second solenoid valve YV2 to stop the oil intake;

[0072] S3, circulate and eliminate bubbles, close the second solenoid valve YV2, open the third solenoid valve YV3 and the fourth solenoid valve YV4, turn on the oil pump M2, fill the corresponding pipeline with oil in the oil tank 1, and circulate the oil in the oil tank 1 internally in the pipeline to defoam the oil. If the oil in the oil tank 1 is lower than the set low liquid level during this process, open the second solenoid valve YV2 to let the oil in until the oil in the oil tank 1 reaches the set middle liquid level, close the second solenoid valve YV2, and circulate again to eliminate bubbles;

[0073] S4, maintain constant pressure, open the transformer bottom valve V2, transformer oil return regulating valve V1, increase the oil pressure inside the transformer, and maintain the transformer body pressure constant, if the pressure sensor PT detects that the pressure value is lower than the set pressure, the oil pump M2 will work to inject oil, if the pressure sensor PT detects that the pressure value is higher than the set pressure, the oil pump M2 will stop working, and the fifth solenoid will open at the same time to return the oil to the transformer oil pillow;

[0074] S5. Check the pressure tightness of the transformer. After maintaining constant pressure for 24 hours, check whether the transformer body has oil leakage and whether the oil pressure can be maintained stable.

[0075] S6. After the test is completed, close the transformer bottom valve V2, the first solenoid valve YV1, and the fourth solenoid valve YV4, open the fifth solenoid valve YV5, the third solenoid valve YV3, and the oil pump M2, and inject the oil in the oil tank 1, the oil outlet pipeline, and the oil return pipeline back into the transformer oil pillow, waiting for the next sealing test.

[0076] By presetting the transformer oil pressure value, oil supply differential pressure, oil tank 1 liquid level value, vacuum degree and test time in the control system, human operation errors can be effectively reduced and the accuracy of the test can be improved.

[0077] The oil storage and bubble removal steps are automated to ensure timely oil replenishment and cyclic defoaming, ensuring the quality of the oil inside the transformer and the stability of the sealing. The design of this process can minimize the impact of bubbles on the properties of the oil, thereby improving the reliability of the test.

[0078] The constant pressure maintenance mechanism can automatically adjust the working state of the oil pump M2 by real-time monitoring the data of the pressure sensor PT to ensure the stability of the internal pressure of the transformer. This dynamic pressure adjustment function can effectively avoid test failures caused by pressure fluctuations and improve the credibility of the test results.

[0079] Finally, the convenient test end process, through the automated closing and oil draining design, makes the cleanup work after the test more efficient, reduces the workload of operators, and prepares for the next sealing test. This design not only improves work efficiency, but also facilitates the maintenance and management of the equipment.

[0080] This transformer sealing test method improves the accuracy and reliability of the test through systematic steps, automated control and efficient maintenance mechanism, providing a solid guarantee for the safe operation of the transformer.

[0081] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. The substitution may be a substitution of a part of the structure, device, method step, or a complete technical solution. The equivalent replacement or change according to the technical solution and the inventive concept of the present invention shall be covered within the protection scope of the present invention.

Claims

1. A transformer sealing test device, characterized in that: include: Oil tank, oil pump, connecting tooling, pressure sensor, several solenoid valves and corresponding oil outlet and return pipelines; The oil inlet of the oil tank is connected to the oil outlet pipe of the transformer oil pillow through a connecting pipe, the oil outlet of the oil tank is connected to the oil inlet of the oil pump through an oil outlet pipeline, the oil outlet of the oil pump is connected to the connecting tooling through an oil outlet pipeline, the connecting tooling is connected to the bottom of the transformer body, and the connecting tooling is respectively connected to the oil outlet pipe of the transformer oil pillow and the oil inlet of the oil tank through an oil return pipeline; the circuit formed by the connecting tooling and the oil outlet pipe of the transformer oil pillow is a pressure regulating circuit; the top of the oil tank is connected to a first solenoid valve, and the other end of the first solenoid valve is connected to a vacuum pump; a second solenoid valve is provided between the oil inlet of the oil tank and the oil outlet pipe of the transformer oil pillow; a third solenoid valve is provided between the oil outlet of the oil pump and the connecting tooling; a fourth solenoid valve is provided between the connecting tooling and the oil inlet of the oil tank; a fifth solenoid valve is provided between the connecting tooling and the oil outlet pipe of the transformer oil pillow; the transformer body is connected to the connecting tooling through the bottom valve of the transformer; a pressure sensor is provided between the connecting tooling and the transformer body; the oil pump, the oil tank and all the electric valves are electrically connected to the control system.

2. The transformer sealing test device according to claim 1, characterized in that: A first self-sealing joint is provided between the oil outlet pipe of the transformer oil pillow and the second solenoid valve; a fourth self-sealing joint is provided between the third solenoid valve and the connecting tooling; and a second self-sealing joint is provided between the connecting tooling and the fourth solenoid valve.

3. The transformer sealing test device according to claim 1, characterized in that: A transformer oil return regulating valve is arranged between the connecting tooling and the fifth solenoid valve; and a third self-sealing joint is arranged between the transformer oil return regulating valve and the connecting tooling.

4. The transformer sealing test device according to claim 1, characterized in that: A first one-way valve is provided between the oil outlet of the oil pump and the third solenoid valve, and a second one-way valve is provided between the third solenoid valve and the connecting tooling.

5. The transformer sealing test device according to claim 1, characterized in that: A Y-type filter is provided between the second solenoid valve and the oil inlet of the oil tank.

6. The transformer sealing test device according to claim 1 or 5, characterized in that: The oil tank has a capacity of 5-7L and is provided with a liquid level gauge and a vacuum gauge. The liquid level gauge is divided into a middle liquid level gauge and a low liquid level gauge.

7. The transformer sealing test device according to claim 6, characterized in that: The oil tank is provided with a safety valve and a pressure switch connected with the third solenoid valve.

8. The transformer sealing test device according to claim 1, characterized in that: The control system has an alarm function while controlling the on and off of each solenoid valve and adjusting to maintain constant pressure.

9. A leakage and overcurrent protection method, using the transformer sealing test device according to any one of claims 1 to 8, characterized in that: The steps include: S1. First, set the transformer oil pressure value, oil supply differential pressure, oil tank level value, vacuum degree and test time required for the test in the control system, set all valves to the closed state, and close the transformer gas relay valve; S2, storing oil, opening the second solenoid valve, the first solenoid valve and the vacuum pump, sucking the oil in the transformer oil pillow into the oil tank, and when the oil in the oil tank reaches the set middle liquid level, closing the second solenoid valve to stop the oil intake; S3, circulating to eliminate bubbles, closing the second solenoid valve, opening the third solenoid valve and the fourth solenoid valve, and turning on the oil pump, so that the oil in the oil tank fills the corresponding pipeline, and the oil in the oil tank is internally circulated in the pipeline to defoam the oil. If the oil in the oil tank is lower than the set low liquid level during this process, the second solenoid valve is opened to allow oil to flow in until the oil in the oil tank reaches the set middle liquid level, and the second solenoid valve is closed, and circulating again to eliminate bubbles; S4, maintain constant pressure, open the transformer bottom valve and transformer oil return regulating valve, increase the oil pressure inside the transformer, and maintain the transformer body pressure constant. If the pressure sensor detects that the pressure value is lower than the set pressure, the oil pump will start to inject oil. If the pressure sensor detects that the pressure value is higher than the set pressure, the oil pump will stop working. At the same time, the fifth solenoid will open to return the oil to the transformer oil pillow. S5. Check the pressure tightness of the transformer. After maintaining constant pressure for 24 hours, check whether the transformer body has oil leakage and whether the oil pressure can be maintained stable. S6. After the test is completed, close the transformer bottom valve, the first solenoid valve, and the fourth solenoid valve, open the fifth solenoid valve, the third solenoid valve, and the oil pump, and inject the oil in the oil tank, the oil outlet pipeline, and the oil return pipeline back into the transformer oil pillow, waiting for the next sealing test.

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