Method for measuring inductance value of dry-type air-core reactor

Abstract

The invention discloses a method for measuring the inductance value of a dry-type air-core reactor, and the method comprises the steps: locally selecting a power line, an air switch K, a digital multimeter A, a digital multimeter B, a test connection line and a substitute of a divider resistor R to carry out the measurement line connection, and employing a teakettle as the substitute of the divider resistor R, and performing measurement operation according to the measurement line to obtain the test current Is, the current value I and the voltage value U flowing through the loop, and calculating the inductance value of the reactor. Compared with a digital display type inductance meter measurement mode, the method for measuring the inductance value of the dry-type air-core reactor by using field conditions has the advantages that local materials are used, the method is not limited by conditions, the measurement precision can be ensured, and the problem that the measurement accuracy is high under the condition that no digital display type inductance meter exists is effectively solved. The inductance value of the reactor can be measured quickly, conveniently and accurately, and the measurement efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of dry-type air-core reactor inductance measurement, and in particular relates to a method for measuring the inductance of a dry-type air-core reactor. Background Art

[0002] Dry-type air-core reactor is a coreless reactor, which belongs to an air-core coil. It has the advantages of small size, light weight, no noise, and no maintenance. It is mainly used for reactive power compensation in power systems to improve power quality.

[0003] Regularly measuring the inductance of the reactor can effectively check the welding quality of the reactor winding joints and whether there is inter-turn short circuit in the winding, whether the connecting wires are broken, and whether there is broken strands, so as to ensure the normal and reliable operation of the dry-type air-core reactor.

[0004] The commonly used method to measure the inductance of dry-type air-core reactors is to use a digital inductance meter. When using a digital inductance meter to measure, you only need to select the appropriate measurement gear and connect the test line to the terminal board of the reactor to test. When the displayed value stabilizes, you can get the measured value of the inductance of the reactor.

[0005] But sometimes when measurements need to be made on site, there are often two problems:

[0006] 1) When temporary measurement is needed, the test cannot be completed due to the lack of a digital inductance meter prepared in advance. It is particularly worth mentioning that in a winter in a certain area in the south, a 35kV transmission line was severely covered with ice. The staff prepared to perform AC short-circuit ice-melting work on the line, but the short-circuit current calculated based on the line impedance parameters exceeded the maximum carrying current of the ice-melting power supply. Therefore, it was decided on site to use three dry-type air-core reactors in series with the three phases of the line to limit the excessive ice-melting short-circuit current. In order to ensure the smooth progress of the line ice-melting work, it is urgent to measure the inductance of the three reactors and check whether they are consistent with the nameplate inductance. However, there is no digital inductance meter on site and the test cannot be completed, which seriously affects the power supply needs of users;

[0007] 2) Sometimes, even if a digital inductance meter is prepared, it may be affected by the electromagnetic field interference of the charged equipment in the measurement environment, which will greatly affect the test accuracy and the test cannot be completed. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a method for measuring the inductance of a dry-type air-core reactor, which can quickly, conveniently and accurately measure the inductance of the reactor at any time by utilizing on-site conditions, so that the measurement work can be completed smoothly and quickly.

[0009] The technical solution adopted by the present invention is: a method for measuring the inductance of a dry-type air-core reactor, the method comprising the following steps:

[0010] Step 1. Prepare tools: power cord, air switch K, digital multimeter A, digital multimeter B and test connection line. The substitute of voltage divider resistor R is an electric kettle with rated power P of 1500W and rated voltage U of 220V. The live wire and neutral wire of the power connector of the electric kettle are used as the two ends of the voltage divider resistor R.

[0011] Step 2: Measure the wiring:

[0012] 2.1) Connect the two output ends of the power cord to the two input connectors of the air switch K respectively;

[0013] 2.2) Connect one end of one of the test connection wires to an output connector of the air switch K, and connect the other end of the test connection wire to a connector of the voltage divider resistor R;

[0014] 2.3) Connect one end of another test connection line to the other connector of the voltage divider resistor R, and connect the other end of the test connection line to a terminal block of the reactor Q;

[0015] 2.4) Connect one end of the third test connection line to another terminal block of the reactor Q, and connect the other end of the test connection line to the current jack A3 of the digital multimeter A;

[0016] 2.5) Connect one end of the fourth test wire to the current jack A1 of the digital multimeter A, and connect the other end of the test wire to another output connector of the air switch K;

[0017] 2.6) Connect one end of the fifth test connection line to a terminal block of the reactor Q, and connect the other end of the test connection line to the voltage jack B4 of the digital multimeter B;

[0018] 2.7) Connect one end of the sixth test connection line to another terminal block of the reactor Q, and connect the other end of the test connection line to the voltage jack B3 of the digital multimeter B;

[0019] 2.8) Check and confirm that the switch F1 of the digital multimeter A for measuring current is in the appropriate AC current position;

[0020] 2.9) Check and confirm that the switch F2 of the digital multimeter B used to measure voltage is in the appropriate AC voltage position;

[0021] 2.10) Fill the electric kettle with an appropriate amount of water;

[0022] Step 3: Measurement operation:

[0023] 3.1) After the measurement and wiring are completed, connect the two input connectors of the power cord to the 220V AC power supply U s Socket;

[0024] 3.2) Close the air switch K, so that the input connector of the air switch K is connected to the output connector. At this time, the measurement circuit is connected to the 220V AC power supply U s , the test current I flows through the measurement circuit s ;

[0025] 3.3) When the current value displayed on the LCD screen Y1 of the digital multimeter A for measuring current stabilizes, record the current value I;

[0026] 3.4) When the voltage value displayed on the LCD screen Y2 of the digital multimeter B for measuring voltage stabilizes, record the voltage value U;

[0027] 3.5) The current value I and voltage value U are measured, and then the inductance of the reactor is calculated in step 4;

[0028] Step 4: Calculate measurement data

[0029] 4.1) Obtaining the voltage value U and current value I obtained in step 3.5);

[0030] 4.2) Calculate the measured impedance value of the reactor Q:

[0031] 4.3) The calculated impedance value Z defaults to the inductive reactance value X L ;

[0032] 4.4) Calculate the inductance L of the reactor Q:

[0033] According to:X L =ωL=2πfL

[0034] have to:

[0035] Where ω is the angular frequency and f is the grid frequency.

[0036] Furthermore, the test line connected to the wiring board is provided with a quick connector, which is connected to the operating rod. The quick connector includes a hook clamp, the lower end of the hook clamp is vertically fixedly connected to the bias block, and the bias block is detachably fixedly connected to the operating rod at one end of the hook portion away from the hook clamp. The inverted U-shaped hook portion of the hook clamp is arranged with an elastic and retractable polishing component and an elastic and retractable conductive connection component from bottom to top. The polishing component includes a sandpaper layer, a sponge layer and a bottom plate. Two sandpaper layers are used, which are symmetrically fixedly connected to two sponge layers respectively, and the sponge layer is fixedly connected to the bottom plate. The back of the bottom plate is hinged to an elastic telescopic rod 1, and the elastic telescopic rod 1 is horizontally fixedly connected to the side wall of the hook portion. The conductive connection component includes two conductive blocks, which are hinged to two elastic telescopic rods 2, and the two elastic telescopic rods 2 are respectively fixedly connected to the two side walls of the hook portion. The two conductive blocks are connected to the test line, and the lower ends of the two conductive blocks are provided with an eight-shaped open structure, and the conductive blocks on the same side are connected to the back of the bottom plate by a tension spring.

[0037] Beneficial effects of the present invention: Compared with the prior art, the present invention uses the above-mentioned method for measuring the inductance of a dry-type air-core reactor using on-site conditions. Compared with the measurement method of a digital inductance meter, the present invention uses local materials, is not limited by conditions, and can ensure the accuracy of measurement. It effectively solves the problem of being able to quickly, conveniently and accurately complete the measurement of the inductance of the reactor in the absence of a digital inductance meter, thereby improving the measurement efficiency. A 220V AC power supply is used, and the cable connected to the reactor has a voltage of 220V, which can offset the strong electromagnetic field interference generated by equipment near the reactor (the reactor is powered off during the test), and the ammeter and voltmeter can be far away from the test, which can further effectively avoid the influence of the strong electromagnetic field, effectively solving the problem that the digital inductance meter is interfered by the electromagnetic field, resulting in the inability to complete the measurement and large errors;

[0038] In summary: (1) local materials are used and are not restricted by conditions, which ensures measurement accuracy and improves test efficiency; (2) the application range is wide. This method can be applied to the measurement of the inductance of dry-type air-core reactors of various voltage levels. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of digital multimeter measurement;

[0040] Figure 2 It is the schematic diagram of the measurement circuit;

[0041] Figure 3 This is the measurement wiring diagram;

[0042] Figure 4 This is a schematic diagram of the measurement operation;

[0043] Figure 5 It is a schematic diagram of the quick connector hanging structure;

[0044] Figure 6 This is a schematic diagram of the quick connector structure. DETAILED DESCRIPTION

[0045] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0046] Theoretical analysis: Analyze the two problems existing in the background technology. If there is no digital inductance meter on site (such as a substation or other workplace), the inductance of the dry-type air-core reactor can be measured according to the site conditions and using tools and instruments obtained on site (such as a substation or other workplace). The following technical solutions are proposed:

[0047] 1. Measurement conditions obtained by using local materials:

[0048] (1) Tools: air switch, power cord, digital multimeter, test cable.

[0049] (2) Reactor nameplate parameters: Rated voltage U n , rated current I n .

[0050] (3) Power supply required for measurement: 220V AC power supply U s .

[0051] 2. Measurement, calculation and analysis:

[0052] (1) Taking a 10 kV dry-type air-core reactor as an example, the nameplate rated voltage of the reactor is U n =2356V; rated current I n =1500A. Based on these two nameplate parameters, the rated impedance of the reactor is first calculated.

[0053] (2) If the AC current jack of digital multimeter A is connected in series with the reactor coil Q using a test connection line, and the AC voltage jack of digital multimeter B is connected in parallel with the reactor coil Q using a test connection line, (see Figure 1 (shown)

[0054] When the air switch K is closed, the 220V AC power supply voltage U is connected s When the test current of the measuring circuit is This current greatly exceeds the maximum carrying current of the A AC current range of the digital multimeter, and the test cannot be carried out.

[0055] (3) At this time, a voltage divider resistor R needs to be connected in series with the measurement circuit to limit the test current I of the measurement circuit. s .(See Figure 2 (shown)

[0056] (4) The maximum current carrying capacity of the AC current range of a digital multimeter is generally 10A, that is, we need to set the test current I s Control within 10A. From the inductance formula of air-core coil It can be seen that the inductance L of the air-core coil is related to the length l of the coil, the cross-sectional area S of the coil, and the number of turns N of the coil, but has nothing to do with the magnitude of the current passing through the coil. Its inductance L is a constant and does not change with the magnitude of the current in the coil. Therefore, the test current I s Controlling it within 10A meets the measurement requirements.

[0057] (5) At this time, according to the test current I flowing through the measurement circuit s =7A is used as the calculation basis to calculate how much ohm (Ω) voltage divider resistor R needs to be connected in series in the measurement circuit.

[0058] If a voltage divider resistor R is connected in series with the measurement circuit, the total impedance of the circuit is According to the known power supply voltage U s =220V, the rated impedance of the reactor Q is Z≈1.57Ω.

[0059] Then the test current I of the measuring circuit is s for:

[0060]

[0061] We can get:

[0062]

[0063] The required voltage divider resistor is:

[0064] (6) The required power P is calculated based on the voltage divider resistance:

[0065]

[0066] (7) Select a replacement for the voltage divider resistor R based on the calculated power P:

[0067] At the site (such as substations and other workplaces), electrical appliances with a power P of 1500W that can be selected from local materials include electric kettles, rice cookers, etc., which can be used as a replacement for the voltage divider resistor R.

[0068] Example 1: Reference Figure 3-4 As shown, a method for measuring the inductance of a dry-type air-core reactor comprises the following steps:

[0069] 1. Preparation of tools and equipment required:

[0070] Before using this method to measure, select the following tools and instruments: power cord, air switch K, digital multimeter A, digital multimeter B, test connection line, substitute for voltage divider resistor R (electric kettle with rated power P of 1500W and rated voltage U of 220V), cut off the power connection line of the electric kettle, and transform it into live wire and neutral wire as the two ends of voltage divider resistor R;

[0071] 2. Measurement wiring instructions (see Figure 3 shown):

[0072] (1) Connect one end of the power cord 1101 and one end of the power cord ear 1102 to the connector 1 3 and connector 2 4 of the air switch K respectively;

[0073] (2) Connect one end of the first test connection line 1201 to the connector 3 5 of the air switch K, and connect the other end of the first test connection line 1201 to the connector 1 7 of the voltage divider resistor R;

[0074] (3) Connect one end of the second test connection line 1202 to the connector 2 8 of the voltage-dividing resistor R, and connect the other end of the second test connection line 1202 to the terminal block 1 9 of the reactor Q;

[0075] (4) Connect one end of the third test connection line 1205 to the terminal block 2 10 of the reactor Q, and connect the other end of the third test connection line 1205 to the current jack A3 of the digital multimeter A;

[0076] (5) Connect one end of the fourth test connection line 1206 to the current jack A1 of the digital multimeter A, and connect the other end of the fourth test connection line 1206 to the connector 96 of the air switch K;

[0077] (6) Connect one end of the fifth test connection line 1203 to the terminal block 9 of the reactor Q, and connect the other end of the fifth test connection line 1203 to the voltage jack B4 of the digital multimeter B;

[0078] (7) Connect one end of the sixth test connection line 1204 to the terminal block 2 10 of the reactor Q, and connect the other end of the sixth test connection line 1204 to the voltage jack B3 of the digital multimeter B;

[0079] (8) Check and confirm that the switch F1 of the digital multimeter A for measuring current is in the appropriate AC current position (i.e., the current position meets the test range requirements);

[0080] (9) Check and confirm that the switch F2 of the digital multimeter B used to measure voltage is in the appropriate AC voltage position (i.e., the voltage position meets the test range requirements);

[0081] (10) If the selected substitute for the voltage divider resistor R is an electric kettle, it is necessary to put an appropriate amount of water in the kettle to avoid dry boiling;

[0082] 3. Measurement operation instructions (see Figure 4 shown):

[0083] (1) After the measurement and wiring are completed, connect the power connector 1 at the other end of the power line 1101 and the power connector 2 at the other end of the power line 2102 to the 220V AC power supply U s ;

[0084] (2) Close the air switch K, connect the connector 1 (3) of the air switch K to the connector 3 (5), and connect the connector 2 (4) of the air switch K to the connector 4 (6). At this time, the measurement circuit is connected to the 220V AC power supply U s , the test current I flows through the measurement circuit s ;

[0085] (3) When the current value displayed on the LCD screen Y1 of the digital multimeter A for measuring current stabilizes, record the current value I;

[0086] (4) When the voltage value displayed on the LCD screen Y2 of the digital multimeter B for measuring voltage stabilizes, record the voltage value U;

[0087] (5) The inductance of the reactor is calculated by measuring the current value I and voltage value U;

[0088] 4. Measurement data calculation

[0089] The following is the actual measured data of a 10 kV dry-type air-core reactor with a nameplate inductance of 5 mH:

[0090] (1) Voltage measurement value U: 10.21V, current measurement value I: 6.78A;

[0091] (2) Calculate the measured impedance value of the reactor Q:

[0092] (3) Because the DC resistance value R of the reactor Q is relatively large relative to the inductive reactance value X L So the impedance value Z we calculated is the inductive reactance value X by default. L ;

[0093] (4) At this time, the inductance L of the reactor Q can be calculated:

[0094] According to:X L =ωL=2πfL

[0095] We can get:

[0096] (5) In order to verify whether the inductance L calculated by this measurement method is accurate, the data is compared with that measured by a digital inductance meter (under experimental conditions without electromagnetic interference). The inductance measured by the digital inductance meter is 4.76mH. The data measured by the two methods are basically consistent with the nameplate inductance, and the test accuracy of the measurement method of the present invention is better than that of the digital inductance meter. The data comparison is shown in Table 1.

[0097] Table 1 Data comparison as shown in Table

[0098]

[0099] In order to further verify the feasibility and accuracy of the measurement method of the present invention, three dry-type air-core reactors with different inductances were tested respectively. The test data are shown in Table 2.

[0100] Table 2 Data test as shown in table

[0101]

[0102] Compared with the measurement method of digital inductance meter, the above method of measuring the inductance of dry-type air-core reactor by utilizing on-site conditions uses local materials, is not restricted by conditions, and can ensure the measurement accuracy. It effectively solves the problem of quickly, conveniently and accurately completing the measurement of reactor inductance in the absence of digital inductance meter, thereby improving the measurement efficiency.

[0103] like Figure 5-6As shown, in order to quickly connect the test line, the test line connected to the wiring board 30 is provided with a quick connector 10, and the quick connector 10 is connected to the operating rod 20. The quick connector includes a hook clamp 101, and the lower end of the hook clamp 101 is vertically fixedly connected to the bias block 102, and the bias block 102 is detachably fixedly connected to the operating rod 20 at one end of the hook portion away from the hook clamp 101. The inverted U-shaped hook portion of the hook clamp 101 is sequentially arranged with an elastically retractable polishing component 103 and an elastically retractable conductive connection component 104 from bottom to top, and the conductive connection component 104 is connected to the test line. The surface of the connecting piece is polished by the polishing component. After the metal layer is smooth, the conductive connection component is pushed in for elastic extrusion contact conductive connection, which can ensure the reliability of the conductive connection and make the test more reliable and accurate. The polishing component 103 includes a sandpaper layer 105, a sponge layer 106 and a bottom plate 107. The sandpaper layer 105 is made of two sheets, which are symmetrically fixedly connected to the two sponge layers 106 respectively. The sponge layer 106 is fixedly connected to the bottom plate 107. The back of the bottom plate 107 is hinged on an elastic telescopic rod 108. The elastic telescopic rod 108 is horizontally fixedly connected to the side wall of the hook. The conductive connection component 104 includes two conductive blocks 109. The two conductive blocks 109 are hinged The two elastic telescopic rods 110 are connected to the two side walls of the hook, and the two conductive blocks 109 are connected to the test line, and the lower ends of the two conductive blocks 109 are provided with an eight-shaped open structure. The conductive blocks 109 on the same side are connected to the back of the bottom plate 107 through a tension spring 111. The polishing structure formed by the sandpaper layer, the sponge layer and the bottom plate can quickly and safely polish the connecting plate, and the polishing is easy. The elastic and retractable hinged structure can ensure that the sandpaper layer always keeps in contact with the connecting plate. The polishing is smoother and faster by moving up and down multiple times. The retractable conductive block cooperates with the hinged structure, and can adaptively fit the two conductive blocks tightly to the connecting plate. The connection contact surface is larger and the conductive reliability is higher. The tops of the two conductive blocks 109 are conductively connected through the spiral retractable soft test line 112, which can further improve the conductive reliability. The open structure is adopted to facilitate the connecting plate to be inserted between the conductive blocks. The use of a tension spring can ensure that it can smoothly enter the hinged conductive block after grinding. The free length of the tension spring ensures that the bottom plate and the conductive block remain parallel. The two test lines connected to the connecting plate are connected to the same quick connector, which improves the hanging efficiency and reduces labor.

[0104] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for measuring the inductance of a dry-type air-core reactor, characterized in that: The method comprises the following steps: Step 1. Prepare tools: power cord, air switch K, digital multimeter A, digital multimeter B and test connection line. The substitute of voltage divider resistor R is an electric kettle with rated power P of 1500W and rated voltage U of 220V. The live wire and neutral wire of the power connector of the electric kettle are used as the two ends of the voltage divider resistor R. Step 2: Measure the wiring: 2.1) Connect the two output ends of the power cord to the two input connectors of the air switch K respectively; 2.2) Connect one end of one of the test connection wires to an output connector of the air switch K, and connect the other end of the test connection wire to a connector of the voltage divider resistor R; 2.3) Connect one end of another test connection line to the other connector of the voltage divider resistor R, and connect the other end of the test connection line to a terminal block of the reactor Q; 2.4) Connect one end of the third test connection line to another terminal block of the reactor Q, and connect the other end of the test connection line to the current jack A3 of the digital multimeter A; 2.5) Connect one end of the fourth test wire to the current jack A1 of the digital multimeter A, and connect the other end of the test wire to another output connector of the air switch K; 2.6) Connect one end of the fifth test connection line to a terminal block of the reactor Q, and connect the other end of the test connection line to the voltage jack B4 of the digital multimeter B; 2.7) Connect one end of the sixth test connection line to another terminal block of the reactor Q, and connect the other end of the test connection line to the voltage jack B3 of the digital multimeter B; 2.8) Check and confirm that the switch F1 of the digital multimeter A for measuring current is in the appropriate AC current position; 2.9) Check and confirm that the switch F2 of the digital multimeter B used to measure voltage is in the appropriate AC voltage position; 2.10) Fill the electric kettle with an appropriate amount of water; Step 3: Measurement operation: 3.1) After the measurement and wiring are completed, connect the two input connectors of the power cord to the 220V AC power supply U s Socket; 3.2) Close the air switch K, so that the input connector of the air switch K is connected to the output connector. At this time, the measurement circuit is connected to the 220V AC power supply U s , the test current I flows through the measurement circuit s ; 3.3) When the current value displayed on the LCD screen Y1 of the digital multimeter A for measuring current stabilizes, record the current value I; 3.4) When the voltage value displayed on the LCD screen Y2 of the digital multimeter B for measuring voltage stabilizes, record the voltage value U; 3.5) The current value I and voltage value U are measured, and then the inductance of the reactor is calculated in step 4; Step 4: Calculate measurement data 4.1) Obtaining the voltage value U and current value I obtained in step 3.5); 4.2) Calculate the measured impedance value of the reactor Q: 4.3) The calculated impedance value Z defaults to the inductive reactance value X L ; 4.4) Calculate the inductance L of the reactor Q: According to:X L =ωL=2πfL have to: Where ω is the angular frequency and f is the grid frequency.

2. A method for measuring the inductance of a dry-type air-core reactor according to claim 1, characterized in that: A test line connected to a wiring board (30) is provided with a quick connector (10), which is connected to an operating rod (20), and comprises a hook clamp (101), the lower end of which is vertically fixedly connected to a bias block (102), and one end of the bias block (102) which is away from the hook portion of the hook clamp (101) is detachably fixedly connected to the operating rod (20), and an inverted U-shaped hook portion of the hook clamp (101) is sequentially arranged with an elastically retractable polishing component (103) and an elastically retractable conductive connection component (104) from bottom to top, and the polishing component (103) comprises a sandpaper layer (105), a sponge layer (106) and a bottom plate (107), and the sandpaper layer (105) is provided in two sheets, which are symmetrically fixedly connected to the two pieces. The sponge layer (106) is fixedly connected to a bottom plate (107), the back of the bottom plate (107) is hinged to an elastic telescopic rod (108), the elastic telescopic rod (108) is horizontally fixedly connected to a side wall of the hook, the conductive connection assembly (104) comprises two conductive blocks (109), the two conductive blocks (109) are hinged to two elastic telescopic rods (110), the two elastic telescopic rods (110) are respectively fixedly connected to two side walls of the hook, the two conductive blocks (109) are connected to a test line, and the lower ends of the two conductive blocks (109) are provided with an open structure in an eight-shaped shape, and the conductive blocks (109) on the same side are connected to the back of the bottom plate (107) through a tension spring (110).

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