Detection device for gas volume of gas relay

Abstract

The utility model provides a device for detecting the gas volume of a gas relay, and aims to solve the problem of how to improve the detection precision of the gas volume of the gas relay. The device is characterized in that the device comprises a gas relay and a differential pressure sensor, the differential pressure sensor comprises a lower pressure guiding opening and an upper pressure guiding pipe in the shape of two bent pipes, the device further comprises a gear flow meter, one of two ports of an oil cavity of the gas relay is connected with an inflow port of the gear flow meter, and the other port is connected to an oil injection port of an oil pump; the horizontal section and the vertical section of the bent pipe-shaped upper pressure guiding pipe are clamped by alpha, the alpha is larger than or equal to 110 degrees and smaller than or equal to 120 degrees, the vertical section pipe is a reducer pipe, and the reducer pipe means that the inner diameter of a lower half branch pipe of the vertical section is smaller than that of an upper half branch pipe of the vertical section; the two lower pressure guiding ports are arranged up and down.

Description

Technical Field

[0001] This utility model relates to a method and a detection device for detecting the gas volume in a gas relay. Background Technology

[0002] Gas relays are protective devices in power systems. In this system, the gas relay has two ports on its left and right sides, each connected to the transformer and oil tank via flanges. The front and rear ends of the gas relay have two viewing windows. During operation, the gas relay's oil chamber is filled with transformer oil. When a fault or discharge occurs inside the transformer, gas is generated and enters the top of the gas relay's oil chamber through a pipe, causing the oil level to drop. Therefore, it is necessary to monitor the volume of gas occupying the top in real time. Currently, the main methods for detecting the gas volume in gas relays include capacitive gas volume sensors, ultrasonic sensors, and differential pressure sensors. These methods convert the pressure value P generated by the liquid surface measured and calculated by the sensor into an oil level height h_oil. Then, the total height of the gas relay, h_total, is subtracted from the oil level height h_oil to obtain the gas height h in the gas relay, i.e., h_gas = h_total - h_oil. Finally, the gas volume is calculated based on h_gas, as shown in CN 216621357 U. CN216621357 U discloses a gas volume sensor, including a top pressure tap 2 and a liquid surface pressure tap 18, used to calculate the pressure difference between the upper pressure port (the pressure port of the top pressure tap 2) and the lower pressure port (the pressure port of the liquid surface pressure tap 18). Therefore, the gas volume sensor belongs to a differential pressure sensor. It also discloses a gas relay equipped with a gas volume sensor, that is, a detection device composed of a gas volume sensor and a gas relay, used to detect the gas volume in the gas relay. The gas volume sensor is installed on a window 24 of the gas relay, which is then discarded (see paragraphs 45 and 68 of its specification). The gas volume sensor calculates the pressure value generated by the liquid surface P=P2-P1 (see paragraph 30 of its specification) by measuring the pressure value P1 (pressure value of the closed environment) of the top pressure port and the pressure value P2 (the sum of the ambient pressure and the liquid surface pressure) of the liquid surface pressure port. Gas relays come in many varieties, with varying internal structures and shapes. For example, CN 216621357 U uses a method that converts measured pressure values ​​to height, failing to consider the impact of internal structure and shape differences on gas volume, thus affecting the accuracy of gas volume measurement. Secondly, during normal pressure testing, both the upper and lower pressure taps must be filled with transformer oil. CN 216621357 U only has one lower pressure tap, led out from the liquid level tap 18. When transformer oil is injected into the gas relay, the oil level in the oil chamber continuously rises. When it exceeds the lower pressure tap, oil flows into it. However, air cannot be completely expelled from the lower pressure tap, creating trapped air within the tube. The amount of trapped air is uncertain, resulting in pressure measurement errors. In each test, the amount of trapped air varies, leading to different pressure values ​​P2 each time. For the same reason, the pressure value P1 of the pressure tapping tube is different in each measurement, which leads to a progressively larger error in the calculation of the pressure value P = P2 - P1 generated by the liquid surface, and the oil level height h, gas height h, and gas volume V converted from the pressure value P.Finally, each pressure tube is a two-section bent tube, with the two sections at a right angle, i.e., a 90-degree angle between them (see). Figure 4 The two sections refer to the horizontal and vertical sections of the tube. Inserting these two L-shaped pressure-sensing tubes into the oil chamber through the limited-sized opening of the gas relay is not easy. Therefore, copper round tubes (referred to as steel tubes) are generally chosen for the upper and lower pressure-sensing tubes. This involves first bending the L-shaped copper tube by hand to deform it, inserting it into the oil chamber, and then restoring the upper and lower pressure-sensing tubes to their original shape. The repeated bending and deformation by hand makes it difficult to ensure that the height of the upper and lower pressure-sensing tubes matches the calibration, significantly affecting accuracy. Furthermore, the limited diameter of the copper tube makes it easy for air to be trapped during oil filling. Summary of the Invention

[0003] To improve the accuracy of real-time detection of gas volume in a gas relay, the purpose of this invention is to provide a gas relay gas volume detection device.

[0004] The method for detecting the gas volume of a gas relay involved in this utility model is as follows:

[0005] Step 1: Establish a pressure-gas volume correspondence table. Specifically, use a differential pressure sensor to measure the pressure value of the gas relay in the set state (i.e., P=P2-P1 as described in CN 216621357 U): ① Measure the pressure value P0 when the gas relay is full of transformer oil, at which time the gas volume V0 in the gas relay is 0; ② Sequentially discharge and measure, where discharge refers to discharging D milliliters (D=1, 2, or 3) of transformer oil, and measurement refers to measuring the pressure value after discharge. Repeat the sequential discharge and measurement n times to obtain pressure values ​​P1, P2, ..., Pn, and establish a one-to-one correspondence between the discharged oil volume D, 2D, ..., nD, and also a one-to-one correspondence between the discharged oil volume and the discharged gas volume (under the same pressure, the discharged oil volume and the discharged gas volume are the same); ③ Together with the gas volume V0=0 corresponding to P0, establish a pressure Pi-gas volume Vi correspondence table (i=1, 2, ..., n);

[0006] Step 2: Use a differential pressure sensor to measure the current (non-set state) pressure value P of the gas relay; after obtaining the P value, find the upper and lower limits of the P value, i.e., the Pi value and Pi-1 value, and their corresponding gas volumes Vi and Vi-1 in the pressure-gas volume correspondence table established in Step 1;

[0007] Step 3: Calculate the current gas volume V of the gas relay. Since Vi-1 ≤ V ≤ Vi, and Vi - Vi-1 = D, therefore...

[0008] V=V i-1 +D(PP) i-1 ) / (P i -P i-1 (1)

[0009] Substitute the set value D, the measured current pressure value P, and the values ​​Vi and Vi-1 from the pressure-volume correspondence table into equation (1) to obtain the current gas volume V of the gas relay.

[0010] The above D is inversely proportional to n; the smaller the D value, the higher the detection accuracy.

[0011] The detection device implementing the above method, namely this utility model, includes a gas relay and a differential pressure sensor. The differential pressure sensor includes a lower pressure inlet and an upper pressure inlet in the shape of two bent sections. The upper pressure inlet, characterized in that the horizontal and vertical sections of the bent sections are angled by α, where α ≤ 110° ≤ 120°, and the vertical section is a reducing pipe, meaning the inner diameter of the lower half of the vertical section is smaller than the inner diameter of the upper half. This utility model eliminates the lower pressure inlet and provides two lower pressure inlets arranged vertically. It also includes a gear flow meter and two ports of the gas relay oil chamber; one port is connected to the inlet of the gear flow meter, and the other port is connected to the oil pump's inlet. In other words, when using the above method to detect the gas volume in the gas relay, the transformer and oil tank must be removed before connecting the gear flow meter and oil pump. The method of use is as follows: First, use an oil pump to fill the oil chamber of the gas relay with transformer oil. When the oil is full, the gas volume V0 in the gas relay is 0. Then, use a differential pressure sensor to measure and record the pressure value P0 when the oil is full. Next, discharge the oil n times through a gear flow meter, discharging D milliliters of oil each time. After each discharge of D milliliters of oil, use a differential pressure sensor to measure the pressure value of the gas relay at that time, obtain the values ​​P1, P2, ..., Pn, and record them. Then, establish a pressure-volume correspondence table according to the method described in step 1.

[0012] The upper pressure tap of the differential pressure sensor is modified so that its two ends form obtuse angles, which facilitates venting from the pipe. The vertical section of the upper pressure tap is replaced with a reducing pipe, which causes the oil pressure at the lower middle end of the pipe to increase non-linearly, which helps to break up air bubbles in the pressure tap and thus vent them smoothly. The reducing pipe refers to the pipe whose inner diameter gradually increases from the lower end to the upper end. This invention eliminates the lower pressure tap of the differential pressure sensor, freeing up more space for the upper pressure tap without affecting the detection. The differential pressure sensor is equipped with two lower pressure taps arranged vertically, so that air will be expelled from the higher hole during oil injection, eliminating trapped air and improving the accuracy of the oil surface pressure P2 measurement.

[0013] Compared with existing technologies, this invention effectively avoids the impact of internal structural differences on measurement accuracy and improves the detection accuracy of gas volume in gas relays. Attached Figure Description

[0014] The present invention will be further described below with reference to the accompanying drawings.

[0015] Figure 1This is a schematic diagram of the gas volume detection device in a gas relay.

[0016] Figure 2 yes Figure 1 Schematic diagram of differential pressure sensor 30.

[0017] Figure 3 yes Figure 2 View B.

[0018] Figure 4 yes Figure 3 AA cross-section view. Detailed Implementation

[0019] The method for detecting the gas volume of a gas relay involved in this utility model is as follows:

[0020] Step 1: Establish a pressure-gas volume correspondence table. Specifically, use a differential pressure sensor to measure the pressure value of the gas relay in the set state: ① Measure the pressure value P0 when the gas relay is full of transformer oil, at which time the gas volume V0 in the gas relay is 0; ② Sequentially discharge and measure, where discharge refers to discharging 2 ml (D=2) of transformer oil, and measurement refers to measuring the pressure value after discharge. Repeat the sequential discharge and measurement n times to obtain pressure values ​​P1, P2, ..., Pn, and establish a one-to-one correspondence between the discharged oil volume 2, 4, ..., 2n and the discharged gas volume (under the same pressure, the discharged oil volume and the discharged gas volume are the same); ③ Together with the gas volume V0=0 corresponding to P0, establish a pressure Pi-gas volume Vi correspondence table (i=1, 2, ..., n); the above D value can also be 1 or 3, depending on the required detection accuracy.

[0021] Step 2: Use a differential pressure sensor to measure the current pressure value P of the gas relay; after obtaining the P value, find the upper and lower limits of the P value, i.e., the Pi value and Pi-1 value, and their corresponding gas volumes Vi and Vi-1 in the pressure-gas volume correspondence table established in Step 1;

[0022] Step 3: Calculate the current gas volume V of the gas relay. Since Vi-1 ≤ V ≤ Vi, and Vi - Vi-1 = D, therefore...

[0023] V=V i-1 +D(PP) i-1 ) / (P i -P i-1 (1)

[0024] Substitute the set value D=2, the measured current pressure value P, and the values ​​Vi and Vi-1 in the pressure-volume correspondence table into equation (1) to obtain the current gas volume V of the gas relay.

[0025] The gas volume detection device in the gas relay implementing the above method includes a gas relay 20 and a differential pressure sensor 30. The differential pressure sensor includes a lower pressure inlet and an upper pressure inlet 31 in the shape of two bent sections. The horizontal section 311 and the vertical section 312 of the upper pressure inlet 31 in the shape of bent sections form a 115° angle. The vertical section is a reducing pipe, meaning that the inner diameter of the lower half of the vertical section is smaller than the inner diameter of the upper half, forming a step 313 between them. This invention eliminates the lower pressure inlet, and two lower pressure inlets 32 are provided, arranged in an upper and lower configuration. This invention also includes a gear flow meter 10, with two ports of the gas relay oil chamber. One port is connected to the inlet of the gear flow meter, and the other port is connected to the oil inlet of the oil pump. That is to say, when the device for detecting the gas volume in the gas relay using the above method is needed, the transformer and oil tank need to be removed first, and then the gear flow meter and oil pump need to be connected. The method of use is as follows: First, use an oil pump to fill the oil chamber of the gas relay with transformer oil. When the oil is full, the gas volume V0 in the gas relay is 0. Then, use a differential pressure sensor to measure and record the pressure value P0 when the oil is full. Next, discharge the oil n times through a gear flow meter, discharging D milliliters of oil each time. After each discharge of D milliliters of oil, use a differential pressure sensor to measure the pressure value of the gas relay at that time, obtain the values ​​P1, P2, ..., Pn, and record them. Then, establish a pressure-volume correspondence table according to the method described in step 1.

[0026] The upper pressure tap of the differential pressure sensor is modified so that its two ends form obtuse angles, which facilitates venting from the pipe. The vertical section of the upper pressure tap is replaced with a reducing pipe, which causes the oil pressure at the lower middle end of the pipe to increase non-linearly, which helps to break up air bubbles in the pressure tap and thus vent them smoothly. The reducing pipe refers to the pipe whose inner diameter gradually increases from the lower end to the upper end. This invention eliminates the lower pressure tap of the differential pressure sensor, freeing up more space for the upper pressure tap without affecting the detection. The differential pressure sensor is equipped with two lower pressure taps arranged vertically, so that air will be expelled from the higher hole during oil injection, eliminating trapped air and improving the accuracy of the oil surface pressure P2 measurement.

Claims

1. A gas relay gas volume detection device, comprising a gas relay and a differential pressure sensor, wherein the differential pressure sensor comprises a lower pressure port and an upper pressure port in the shape of two bent tubes, characterized in that; It also includes a gear flow meter, two ports of the gas relay oil chamber, one port connected to the inlet of the gear flow meter, and the other port connected to the oil pump's inlet; the horizontal and vertical sections of the curved upper pressure pipe are angled at α, 110°≤α≤120°, and the vertical section is a reducing pipe, meaning the inner diameter of the lower half of the vertical section is smaller than the inner diameter of the upper half; two lower pressure ports are provided, arranged vertically.

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