A pressure plate for checking transformer pressure relief valve

Abstract

The present invention discloses a pressure plate for checking a transformer pressure relief valve, comprising a pressure plate, a screw, a coil, and a current source; the pressure plate is used to fit the pressure relief valve to apply a test pressure to the pressure relief valve, and the pressure plate is provided with a plurality of threaded holes at intervals to avoid the peripheral area of the pressure relief valve; the screw is made of metal material and is screwed onto the threaded holes of the pressure plate; the number of coils is the same as that of the screw, and they are respectively wound around one side of the screw located on the bottom surface of the pressure plate to form an electromagnet; the current source is electrically connected to the coil to supply power to the electromagnet. The present invention is based on the principle of electromagnets, and changes the pressure applied to the pressure relief valve by changing the current of the electromagnet. Compared with the traditional method of stacking heavy objects, the pressure plate for checking is easy to operate, the pressure generated is continuously adjustable, and the pressure value is accurate, which greatly improves the working efficiency and accuracy of the pressure relief valve checking.

Description

Technical Field

[0001] The invention relates to a pressure plate for checking a transformer pressure relief valve. Background Art

[0002] As one of the most important non-electrical protection devices for transformers, the operational reliability of the pressure relief valve is directly related to transformer safety. When a fault occurs within the transformer, the large amount of gas generated by the fault will cause the transformer's internal pressure to increase, requiring the pressure relief valve to release the pressure. If the pressure relief valve fails to operate properly to release pressure, the transformer may disintegrate due to excessive internal pressure. To ensure the safe and stable operation of the pressure relief valve, the China Southern Power Grid's maintenance and testing procedures require regular verification of the operating value of the transformer's pressure relief valve.

[0003] In current practice, there are generally two methods for calibrating pressure relief valves: one is to use a dedicated inflation instrument to accurately fill the pressure relief valve with gas at a specific pressure and record the operating pressure of the pressure relief valve; the other is to apply a pressure plate with a certain weight to the top of the pressure relief valve and reversely calculate the pressure on the pressure relief valve by changing the weight of the pressure plate. Among them, the former method requires dedicated instruments, which are expensive, complicated to operate, and not convenient for on-site implementation. The latter method requires constantly changing the weight of the pressure plate to change the pressure applied to the pressure relief valve during calibration, which is time-consuming and lacks accuracy because the weight of the pressure plate cannot be continuously adjusted. Summary of the Invention

[0004] In response to the above problems, the present invention provides a new pressure plate for calibrating the transformer pressure relief valve. The electromagnetic suction force is generated by an electromagnet, so that the pressure plate is attracted to the transformer casing. By changing the suction force of the electromagnet, the pressure relief valve is subjected to a specific pressure. Therefore, there is no need to change the weight of the pressure plate, which improves the ease of operation. At the same time, the suction force can be continuously adjusted, thereby improving the calibration accuracy.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A pressure plate for calibrating a transformer pressure relief valve comprises a pressure plate, a screw, a coil and a current source; the pressure plate is used to fit the pressure relief valve to apply test pressure to the pressure relief valve, and a plurality of threaded holes are arranged at intervals on the pressure plate avoiding the peripheral area of the pressure relief valve; the screw is made of metal material and is screwed onto the threaded holes of the pressure plate respectively; the number of coils is the same as that of the screw, and they are respectively wound around one side of the screw located on the bottom surface of the pressure plate to form an electromagnet; the current source is electrically connected to the coil to supply power to the electromagnet.

[0007] During use, the pressure plate is pressed against the pressure relief valve on the transformer housing. The screw is rotated to make contact with the transformer housing. When current is passed through the coil, the electromagnet generates electromagnetic attraction, which causes the electromagnet to be tightly attracted to the transformer housing, thereby applying pressure to the pressure relief valve. By adjusting the amount of current passed, the suction force of the electromagnet can be changed, and thus the pressure applied to the pressure relief valve can be changed.

[0008] As an improvement of the present invention, the pressing plate is circular, made of hard plastic, has a diameter of 50 cm and a thickness of 0.5 cm.

[0009] As an improvement of the present invention, the screw is a steel screw with a diameter of 1 cm and a length of 25 cm.

[0010] As an improvement of the present invention, the coil is connected to the current source via a twisted pair.

[0011] As an improvement of the present invention, the current source is a constant current source, model CSA200, which can output 0-20A direct current.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] Based on the principle of electromagnet, the pressure applied to the pressure relief valve is changed by changing the current of the electromagnet. Compared with the traditional method of stacking weights, this calibration pressure plate is easy to operate, the pressure generated is continuously adjustable, and the pressure value is accurate, which greatly improves the work efficiency and calibration accuracy of the pressure relief valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic structural diagram of a pressure plate for checking a transformer pressure relief valve according to the present invention;

[0015] Figure 2 This is a top view of the pressure plate for checking the transformer pressure relief valve of the present invention, omitting the current source and twisted pair wires;

[0016] Figure 3 This is a diagram showing the use of a pressure plate for checking a transformer pressure relief valve according to the present invention;

[0017] Figure 4 This is a schematic diagram of the calibration of the pressure plate for calibrating the transformer pressure relief valve of the present invention;

[0018] Explanation of the accompanying drawings: 1-pressing plate; 2-screw; 3-coil; 4-current source; 5-twisted pair; 6-pressure relief valve; 7-transformer housing; 8-tensile gauge; 9-hanging rope. DETAILED DESCRIPTION

[0019] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] like Figures 1 to 3 As shown, a pressure plate for checking a transformer pressure relief valve includes a pressure plate 1, a screw 2, a coil 3, a current source 4 and a twisted pair 5.

[0021] The pressure plate 1 is used to fit over the pressure relief valve 6 to apply test pressure to the pressure relief valve 6. In this embodiment, the pressure plate 1 is a circular hard plastic plate with a diameter of 50 cm and a thickness of 0.5 cm. Six threaded holes are spaced apart in the area surrounding the pressure relief valve 6, away from the pressure relief valve 6, for mounting screws 2. The screws 2 are made of metal, for example, steel, with a diameter of 1 cm and a length of 25 cm. There are six screws, the same number of threaded holes, threaded into the threaded holes of the pressure plate 1. The extension of the screws 2 can be adjusted by rotating the screws 2.

[0022] The number of coils 3 is the same as the number of screws 2, and they are wound around each screw 2 on one side of the bottom surface of the pressure plate 1, forming an electromagnet. The ends of the screws 2 on the bottom surface of the pressure plate 1 are in contact with the transformer housing 7. A current source 4 is connected to the coils 3 via a twisted pair cable 5 to supply power to the electromagnet. In this embodiment, the current source 4 is a constant current source, model CSA200, capable of outputting a DC current of 0-20A.

[0023] like Figure 3 As shown, during use, the pressure plate 1 is pressed against the pressure relief valve 6 on the transformer housing 7, and the screw 2 is rotated to make contact with the transformer housing 7. The electromagnet formed by the coil 3 and the screw 2 is connected to the current source 4 via a twisted pair 5. When current is passed through the coil 3, the electromagnet generates an electromagnetic attraction, which causes the electromagnet to be tightly attracted to the transformer housing 7, thereby applying pressure to the pressure relief valve 6. By adjusting the amount of current, the suction force of the electromagnet can be changed, and thus the pressure applied to the pressure relief valve 6 can be changed.

[0024] When the coil is energized, the pressure applied to the pressure relief valve is:

[0025] F=F1+mg (1)

[0026] Where F is the pressure applied to the pressure relief valve, F1 is the electromagnetic attraction generated by the electromagnet, m is the total mass of the device (excluding the current source), and g is the acceleration due to gravity, g = 9.8 m / s 2 .

[0027] According to relevant electromagnetic theorems, the calculation formula of electromagnetic attraction F1 is:

[0028] F1=aI 2 (2)

[0029] Where I is the coil current, and a is a parameter related to the coil structure, such as the coil cross-section, number of turns, and core material.

[0030] Although the size of F can be calculated theoretically, the actual electromagnet structure is difficult to measure accurately, and the shell materials of different transformers are different, resulting in poor calculation accuracy. Therefore, the device needs to be calibrated before each use. The calibration method is as follows:

[0031] 1) Place the entire device horizontally on the transformer housing 7 to be tested, adjust the screw rods 2 so that all six screw rods 2 are in contact with the transformer housing 7, and the pressure plate 1 is in contact with the pressure relief valve 6.

[0032] 2) Turn on the current source 4 and pass a 1A current into the coil 3.

[0033] 3) Use the dynamometer 8 to lift the pressure plate 1 upwards (the two are connected by a suspension rope 9), as shown in the following example: Figure 4 As shown. Slowly increase the pulling force and record the pulling force value that just makes the screw 2 separate from the transformer housing 7. This value is F. According to formulas (1) and (2), the parameter a can be calculated, and the calibration is now complete.

[0034] As can be seen from the above, the steps for using the pressure plate for checking the transformer pressure relief valve of the present application are as follows:

[0035] 1) Calibrate the device.

[0036] 2) Press the pressing plate 1 onto the pressure relief valve 6 on the transformer housing 7 and rotate the screw 2 so that the screw 2 contacts the transformer housing 7 .

[0037] 3) According to the required pressure and the calibration results, supply the corresponding current.

[0038] The above detailed description is a specific description of a feasible embodiment of the present invention. The embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not depart from the present invention should be included in the patent scope of this case.

Claims

1. A pressure plate for checking a transformer pressure relief valve, characterized by: The invention comprises a pressing plate (1), a screw rod (2), a coil (3) and a current source (4); the pressing plate (1) is used to fit the pressure relief valve to apply a test pressure to the pressure relief valve, and the pressing plate (1) is provided with a plurality of threaded holes at intervals in an area around the pressure relief valve; the screw rod (2) is made of a metal material and is screwed to the threaded holes of the pressing plate (1); the number of the coils (3) is the same as that of the screw rod (2), and they are respectively wound around one side of the screw rod (2) located on the bottom surface of the pressing plate (1) to form an electromagnet; the current source (4) is electrically connected to the coil (3) to supply power to the electromagnet; The coil (3) is connected to the current source (4) via a twisted pair of wires; The current source (4) is a constant current source, model CSA200, which can output 0-20A direct current.

2. The pressure plate for checking the transformer pressure relief valve according to claim 1, characterized in that: The pressing plate (1) is circular, made of hard plastic, with a diameter of 50 cm and a thickness of 0.5 cm.

3. The pressure plate for checking the transformer pressure relief valve according to claim 2, characterized in that: The screw (2) is a steel screw with a diameter of 1 cm and a length of 25 cm.

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