Transformer oil return protection device for on-line monitoring of gas dissolved in oil

Abstract

The utility model discloses a transformer oil return protection device for on-line monitoring of gas dissolved in oil, which is provided with a container, the lower end of the container is respectively communicated with an oil inlet pipe and an oil outlet pipe, the oil inlet pipe is provided with a first one-way valve opened towards the direction of the container, and the oil outlet pipe is provided with an oil return valve and a bidirectional gear pump. The upper end of the container is communicated with an exhaust pipe, a second one-way valve, an exhaust valve and a negative pressure pump which are opened in the direction away from the container are sequentially installed on the exhaust pipe, a constant temperature device, a pressure monitoring device, a first liquid level detector and a second liquid level detector are further installed on the container, and the pressure monitoring device is located at the upper end of the container. The first liquid level detector and the second liquid level detector are arranged in a spaced mode from bottom to top, the first liquid level detector is located above the oil outlet pipe, the second liquid level detector is located below the exhaust pipe, other controllable parts except the first one-way valve and the second one-way valve are all connected with the controller, and the operation reliability of the transformer can be improved.

Description

Technical Field

[0001] The utility model relates to a transformer protection device, in particular to a transformer oil return protection device for on-line monitoring of dissolved gases in oil. Background Art

[0002] The on-line monitoring device for dissolved gases in oil is a device for on-line monitoring, analyzing and fault diagnosing the content of dissolved gases (such as hydrogen, carbon monoxide, methane, ethane, ethylene, acetylene, etc.) in the oil used by the transformer. At present, most on-line monitoring devices for dissolved gases in oil are equipped with an oil circulation unit, a degassing unit, a gas sample separation unit, a gas sample signal acquisition unit, a data analysis unit and a control unit. During installation, the inlet pipe and the return pipe of the oil circulation unit are respectively connected to the oil tank of the transformer, forming a circulating oil path between the oil tank of the transformer. During monitoring, first open the inlet valve and the return valve and start the circulating oil pump, replace the oil in the degassing chamber of the degassing unit with the oil inside the transformer through the inlet pipe, then remove the gas in the oil, and the transformer oil from which the gas has been removed returns to the transformer through the return pipe. Since the return pipe of the existing on-line monitoring device for dissolved gases in oil is directly connected to the transformer, the following problems exist:

[0003] 1. If the degassing unit of the on-line monitoring device for dissolved gases in oil fails, there is a potential safety hazard of gas entering the transformer, which is likely to cause the transformer to trip and result in a major accident;

[0004] 2. If the oil returned to the transformer by the on-line monitoring device for dissolved gases in oil contains tiny suspended bubbles, it will cause faults such as internal bubble discharge of the transformer;

[0005] 3. The on-line monitoring device for dissolved gases in oil will increase the content of gases such as oxygen and nitrogen in the oil returned to the transformer. When factors such as the ambient temperature of the transformer operation change, there is a risk of gas saturation and precipitation in the transformer oil. Summary of the Invention

[0006] The utility model is to solve the above technical problems existing in the prior art, and provides a transformer oil return protection device for on-line monitoring of dissolved gases in oil.

[0007] The technical solution of the present utility model is: a transformer oil return protection device for on-line monitoring of dissolved gases in oil, provided with a container, the lower end of the container is respectively communicated with an inlet pipe and an outlet pipe, a first one-way valve opening towards the container is installed on the inlet pipe, a return oil valve and a two-way gear pump are installed on the outlet pipe, the upper end of the container is communicated with an exhaust pipe, and a second one-way valve opening away from the container, an exhaust valve and a negative pressure pump are sequentially installed on the exhaust pipe. A constant temperature device, a pressure monitoring device, a first liquid level detector and a second liquid level detector are also installed on the container. The pressure monitoring device is located at the upper end of the container. The first liquid level detector and the second liquid level detector are arranged at intervals from bottom to top. The first liquid level detector is located above the outlet pipe, and the second liquid level detector is located below the exhaust pipe. The return oil valve, the two-way gear pump, the exhaust valve, the negative pressure pump, the constant temperature device, the pressure monitoring device, the first liquid level detector and the second liquid level detector are electrically connected to a controller. The opening pressure of the first one-way valve and the second one-way valve is 0.2 MPa, and the opening pressure of the second one-way valve is 0.01 MPa;

[0008] The preferred technical solution is that the vertical distance between the first liquid level detector and the outlet pipe is of the height of the container, and the vertical distance between the second liquid level detector and the exhaust pipe is 1 / 3 of the height of the container.

[0009] The present utility model can be connected between the return oil pipe of the on-line dissolved gas in oil monitoring device and the transformer oil return flange. By adopting the method of negative pressure and constant temperature, the return oil of the on-line dissolved gas in oil monitoring device is firstly processed, the air bubbles in the oil can be removed, and it is avoided that the oil returning to the transformer contains trace air bubbles, which may cause internal discharge of the transformer. Secondly, the gas content of oxygen, nitrogen and other gases in the return oil can be reduced to negative saturation and reach -3.2 mL, avoiding the precipitation of saturated gas in the oil. At the same time, when a failure occurs in the degassing part of the on-line dissolved gas in oil monitoring device, it can prevent gas from directly entering the transformer, thus avoiding a great accident caused by the tripping of the transformer. Description of the Drawings

[0010] Figure 1 is a schematic structural diagram of an embodiment of the present utility model.

[0011] Figure 2 is a circuit block diagram of an embodiment of the present utility model.

[0012] Figure 3 is a flowchart of the protection method of an embodiment of the present utility model. Detailed Embodiments

[0013] A transformer oil return protection device for on-line monitoring of dissolved gases in oil according to the present utility model, as Figure 1As shown in the figure, there is a container 1. The lower end of the container 1 communicates with an oil inlet pipe 2 and an oil outlet pipe 3 respectively. A first one-way valve 2-1 that opens towards the container 1 is installed on the oil inlet pipe 2. A return oil valve 3-1 and a two-way gear pump 3-2 are installed on the oil outlet pipe 3. The upper end of the container 1 communicates with an exhaust pipe 4. A second one-way valve 4-1 that opens away from the container 1, an exhaust valve 4-2 and a negative pressure pump 4-3 are sequentially installed on the exhaust pipe 4. A constant temperature device 5, a pressure monitoring device 6, a first liquid level detector 7 and a second liquid level detector 8 are also installed on the container 1. The pressure monitoring device 6 is located at the upper end of the container. The first liquid level detector 7 and the second liquid level detector 8 are arranged at intervals from bottom to top. The first liquid level detector 7 is located above the oil outlet pipe 3. The vertical distance between the two is preferably 1 / 3 of the height of the container. The second liquid level detector 8 is located below the exhaust pipe 4. The vertical distance between the two is preferably 1 / 3 of the height of the container. The circuit block diagram is as Figure 2 As shown, the return oil valve 3-1, the two-way gear pump 3-2, the exhaust valve 4-2, the negative pressure pump 4-3, the constant temperature device 5, the pressure monitoring device 6, the first liquid level detector 7 and the second liquid level detector 8 are electrically connected to a controller 9. The opening pressure of the first one-way valve 2-1 and the second one-way valve 4-1 is 0.2 MPa, and the opening pressure of the second one-way valve 4-1 is 0.01 MPa;

[0014] The protection method based on the present invention is carried out according to the following steps:

[0015] Step 1. The oil inlet pipe 2 is connected to the return oil pipe of the dissolved gas in oil on-line monitoring device, and the two-way gear pump 3-2 is connected to the transformer return oil flange;

[0016] Step 2. The controller 9 controls the constant temperature device 5 to keep the container 1 at a constant temperature of 50 °C; regularly collect the signals of the first liquid level detector 7, the second liquid level detector 8 and the pressure monitoring device 6;

[0017] Step 3. Judge whether the pressure in the container 1 is greater than -0.08 MPa. If yes, the controller 9 controls the exhaust valve 4-2 and the negative pressure pump 4-3 to act to make the pressure in the container 1 -0.08 MPa. If no, go to Step 4;

[0018] Step 4. Determine whether there is a liquid level signal from the first liquid level detector 7. If not, the controller 9 controls the oil return valve 3-1 to open and starts the two-way gear pump 3-2 to pump the transformer oil into the container 1 until the first liquid level detector 7 detects a liquid level signal. Then, the two-way gear pump 3-2 and the oil return valve 3-1 are closed, and return to Step 3; if yes, proceed to Step 5. This step can achieve self-checking, so that the oil level in the container 1 is always above the drain pipe 3 communicating with the transformer, that is, it acts as an oil seal for the oil drain port, avoiding gas from directly entering the transformer through the drain pipe 3, and at the same time avoiding the oil return of the dissolved gas in oil on-line monitoring device from directly entering the transformer;

[0019] Step 5. Determine whether there is a liquid level signal from the second liquid level detector 8. If not, return to Step 4; if yes, the controller 9 controls the oil return valve 3-1 to open and starts the two-way gear pump 3-2 to drain the transformer oil in the container 1 into the transformer through the transformer oil return flange until the first liquid level detector 7 has no liquid level signal. Then, the controller 9 controls the two-way gear pump 3-2 to pump the transformer oil back into the container 1 until the first liquid level detector 7 detects a liquid level signal. Then, the two-way gear pump 3-2 and the oil return valve 3-1 are closed, and the process ends.

[0020] The process of Step 5 is described in detail as follows: After Step 4, it is in the waiting state for the oil return operation of the dissolved gas in oil on-line monitoring device. If the dissolved gas in oil on-line monitoring device does not perform the oil return operation, the second liquid level detector 8 has no liquid level signal and the first one-way valve 2-1 is not opened, so return to Step 4; when the dissolved gas in oil on-line monitoring device performs the oil return operation, since the minimum oil drain pressure of the dissolved gas in oil on-line monitoring device is 0.34 MPa, the oil drain pressure will open the first one-way valve 2-1, and the transformer oil will flow into the container 1. Under the action of constant temperature and negative pressure, the suspended bubbles in the oil and gases such as oxygen and nitrogen contained in the oil will precipitate. The oil level gradually rises. When the oil level reaches the second liquid level detector 8, the second liquid level detector 8 will send a liquid level signal to the controller 9. The controller 9 controls the oil return valve 3-1 to open and starts the two-way gear pump 3-2 to drain the transformer oil in the container 1 into the transformer through the transformer oil return flange. At this time, the oil level will decrease. When it is below the first liquid level detector 7, the first liquid level detector 7 cannot detect the liquid level signal. The controller 9 immediately controls the two-way gear pump 3-2 to reverse and pump the transformer oil into the container 1 until the first liquid level detector 7 detects a liquid level signal. At this time, the two-way gear pump 3-2 and the oil return valve 3-1 are closed, which can avoid gas from directly entering the transformer through the drain pipe 3, and the first oil return protection ends. It can return to Step 3 to achieve the next oil return protection.

[0021] Take the transformer oil of the embodiment of the present utility model and the transformer oil of the comparative example, and conduct saturation measurement in accordance with the relevant provisions of the national standard "Guide for the Analysis and Judgment of Dissolved Gases in Transformer Oil", that is, test how much high-purity nitrogen can be dissolved in a unit of transformer oil under the state of constant temperature and variable pressure or constant pressure and variable temperature. If the dissolution is negative, the larger the absolute value of the negative value, the more gas can be dissolved in the oil, that is, the lower the saturation (gas content).

[0022] The transformer oil of the embodiment of the present utility model is the transformer oil after being processed by the method of the embodiment of the present utility model for 30 minutes. The transformer oil of the comparative example is the transformer oil after being processed by changing the temperature or pressure of the container for 30 minutes on the basis of the embodiment of the present utility model.

[0023] The specific temperature, pressure and measurement results are shown in Table 1 and Table 2.

[0024] Table 1

[0025]

[0026] Serial number 9 in Table 1 is the embodiment of the present utility model, and the rest are comparative examples. Although the saturation is the lowest in the comparative example at a temperature of 50 °C and a pressure of -0.09 MPa, the greater the negative pressure, the longer the running time of the negative pressure vacuum pump, and it is easy to have failures.

[0027] Table 2

[0028]

[0029] Serial number 5 in Table 2 is the embodiment of the present utility model, and the rest are comparative examples. It can be seen that the saturation of the transformer oil of the embodiment of the present utility model is the lowest. Generally, the gas content (saturation) in transformer oil is between -2.5 and -1.0. The gas content (saturation) index of the transformer oil processed by the embodiment of the present utility model is better than that of the original transformer oil.

Claims

1. A transformer oil return protection device for on-line monitoring of dissolved gases in oil, characterized in that: There is a container (1), the lower end of the container (1) is respectively communicated with an oil inlet pipe (2) and an oil outlet pipe (3). A first one-way valve (2-1) opening towards the container (1) is installed on the oil inlet pipe (2). An oil return valve (3-1) and a two-way gear pump (3-2) are installed on the oil outlet pipe (3). The upper end of the container (1) is communicated with an exhaust pipe (4). A second one-way valve (4-1) opening away from the container (1), an exhaust valve (4-2) and a negative pressure pump (4-3) are successively installed on the exhaust pipe (4). A temperature control device (5), a pressure monitoring device (6), a first liquid level detector (7) and a second liquid level detector (8) are also installed on the container (1). The pressure monitoring device (6) is located at the upper end of the container. The first liquid level detector (7) and the second liquid level detector (8) are arranged at intervals from bottom to top. The first liquid level detector (7) is located above the oil outlet pipe (3). The second liquid level detector (8) is located below the exhaust pipe (4). The oil return valve (3-1), the two-way gear pump (3-2), the exhaust valve (4-2), the negative pressure pump (4-3), the temperature control device (5), the pressure monitoring device (6), the first liquid level detector (7) and the second liquid level detector (8) are electrically connected to a controller (9). The opening pressure of the first one-way valve (2-1) is 0.2 MPa, and the opening pressure of the second one-way valve (4-1) is 0.01 MPa.

2. The transformer oil return protection device for on-line monitoring of dissolved gases in oil according to claim 1, characterized in that: The vertical distance between the first liquid level detector (7) and the oil outlet pipe (3) is 1 / 3 of the height of the container (1). The vertical distance between the second liquid level detector (8) and the exhaust pipe (4) is 1 / 3 of the height of the container (1).

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