A voltage divider AC withstand voltage test device to prevent adjacent bushings from being broken down.

Abstract

This invention relates to an AC withstand voltage test device for preventing adjacent bushing breakdown using a voltage divider method. The device includes a frequency converter cabinet, an excitation transformer, a voltage divider, and a device under test. The output terminal of the frequency converter cabinet is connected to the input terminal of the excitation transformer. The withstand voltage test device also includes a voltage divider module. The input terminal of the voltage divider module is connected to the output terminal of the excitation transformer. The output side of the voltage divider module has a first output terminal and a second output terminal. The first output terminal is connected to the device under test and the voltage divider, and the second output terminal is connected to the adjacent bushing of the device under test. Compared with existing technologies, this invention can be widely applied to on-site AC withstand voltage tests under conditions of insufficient safety distance between adjacent bushings and other ungrounded adjacent equipment. It can solve the problem of insufficient safety distance between adjacent bushings and ungrounded adjacent equipment during on-site withstand voltage tests, ensuring safe on-site testing.

Description

Technical Field

[0001] This invention relates to AC withstand voltage testing equipment, and more particularly to a voltage-dividing AC withstand voltage testing equipment that prevents adjacent bushings from being broken down. Background Technology

[0002] High-voltage power equipment requires AC withstand voltage testing after commissioning and major overhaul. According to the latest technical standards, the AC withstand voltage test value for all voltage levels of GIS equipment is generally 100% of the factory test value during commissioning.

[0003] After the on-site handover test values ​​are increased to 100% of the factory test values, there is no significant impact on the electrical isolation between internal breaks of the GIS equipment, and there are already relatively mature same-frequency and same-phase testing technologies. However, the increase in test values ​​has a significant impact on the external safety distance. Since the layout and distance of HGIS / GIS remain unchanged in typical substation designs, the insulation margin between the high-voltage section and adjacent equipment is reduced during on-site testing. Especially during withstand voltage tests in expansion projects, the close arrangement of already operational equipment in the confined space poses a risk of air gap breakdown, and the problem of insufficient insulation margin for 500kV HGIS equipment during AC withstand voltage tests is particularly serious.

[0004] The safe distance for 500kV equipment without power interruption is 5 meters. Relevant literature suggests that during AC withstand voltage tests of 550kV GIS equipment, the electrical distance between high-voltage leads, high-voltage capacitor dividers, and other equipment and ground should be no less than 5 meters.

[0005] However, many 500kV HGIS test scenarios cannot meet this requirement. For example, a substation already has a 5012 bay, and when expanding to a 5013 bay, a withstand voltage test needs to be performed on the 5013 bay. Figure 1 As shown. During the test, the bushing voltage in the expanded 5013 bay should be 740kV, while the existing 5012 bay bushing can be grounded or floating. The air clearance between adjacent bushings in the new and old bays is only about 3.5 meters. In this limited space, the air gap insulation distance between adjacent bushings is insufficient, which may cause the air gap between bushings to break down before the test voltage is reached. The breakdown voltage will not only affect adjacent bushings but also prevent the withstand voltage test from being completed normally.

[0006] Currently, to ensure testing safety, the test voltage is often reduced. However, this results in the actual test voltage not meeting the requirements and reduces the effectiveness of AC withstand voltage testing in assessing the quality of GIS equipment. Summary of the Invention

[0007] The purpose of this invention is to provide a voltage-dividing AC withstand voltage test device that prevents adjacent bushings from being broken down. It can be widely used in on-site AC withstand voltage tests when the safety distance between adjacent bushings and other ungrounded adjacent equipment is insufficient. It can solve the problem of insufficient test safety distance between adjacent bushings and ungrounded adjacent equipment during on-site withstand voltage tests, and ensure the safe conduct of on-site tests.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] An AC withstand voltage test device for preventing adjacent bushings from being broken down by voltage divider includes a frequency converter cabinet, an excitation transformer, a voltage divider, and a device under test. The output terminal of the frequency converter cabinet is connected to the input terminal of the excitation transformer. The withstand voltage test device also includes a voltage divider module. The input terminal of the voltage divider module is connected to the output terminal of the excitation transformer. The output side of the voltage divider module is provided with a first output terminal and a second output terminal. The first output terminal is connected to the device under test and the voltage divider, and the second output terminal is connected to an adjacent device of the device under test.

[0010] The voltage divider module is a reactor group, which is composed of multiple reactor sections stacked sequentially. Each reactor section has a connector at its end. The bottom connector of the bottom reactor section is the input terminal of the voltage divider module, which is connected to the output terminal of the excitation transformer. The first output terminal is located at the top connector of the top reactor section, and the second output terminal is located at the top connector of any other reactor section other than the top reactor section.

[0011] The voltage divider module is a combination of a reactor group and a capacitor voltage divider device. The input terminal at the bottom of the reactor group is connected to the output terminal of the excitation transformer. The top of the reactor group is connected to one end of the capacitor voltage divider device as the first output terminal. The other end of the capacitor voltage divider device is connected to the adjacent device of the device under test as the second output terminal.

[0012] The capacitor voltage divider includes a base, an insulating cylinder, and a voltage divider capacitor bank. The insulating cylinder is mounted on the base, and the voltage divider capacitor bank is mounted on the insulating cylinder. Both ends of the voltage divider capacitor bank are provided with equalizing rings. One equalizing ring is connected to a reactor bank, and the other equalizing ring is connected to a nearby device of the device under test.

[0013] There are multiple insulating cylinders, which are stacked vertically in sequence.

[0014] Preferably, the number of insulating cylinders is three.

[0015] The base is a cross-shaped base.

[0016] The base is equipped with multiple adjustable support feet.

[0017] The voltage divider capacitor bank and the insulating cylinder are arranged vertically, and the two ends of the voltage divider capacitor bank are connected to the insulating cylinder through supporting insulating rods, forming a stable triangular force-bearing structure.

[0018] The voltage divider capacitor bank is formed by multiple voltage divider capacitors connected in series, and the voltage divider capacitors are fixed and connected to each other by connecting flanges.

[0019] The low-voltage side of the voltage divider is grounded and used to measure the high voltage of the test system.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. It can be widely used in field AC withstand voltage tests under conditions where the safety distance between adjacent bushings and other ungrounded adjacent equipment is insufficient. It can solve the problem of insufficient test safety distance between adjacent bushings and ungrounded adjacent equipment during field withstand voltage tests, and ensure the safe conduct of field tests.

[0022] 2. High voltage division ratio: Compared with the method of using a step-up transformer to increase voltage, the method of the present invention can achieve a higher voltage division value, with a voltage division ratio of over 50%. The voltage between the tested device and the adjacent bushing is lower, and the safety factor during the test is higher.

[0023] 3. When using the reactance voltage divider method, it is only necessary to use the existing series withstand voltage test equipment to introduce the lower potential of the reactor group into the nearby bushing or other ungrounded nearby equipment.

[0024] 4. When using the capacitor voltage divider method, it is only necessary to add a capacitor voltage divider device to the existing series resonant test equipment, and connect the voltage divider capacitor bank on the capacitor voltage divider device in series with the nearby bushing or other ungrounded nearby equipment.

[0025] 5. The capacitor voltage divider uses an insulating cylinder to support the voltage divider capacitor bank, which can improve the height adaptability of the voltage divider capacitor bank.

[0026] 6. The base of the capacitor voltage divider is equipped with multiple adjustable support feet, which can improve site adaptability.

[0027] 7. A voltage divider capacitor bank is formed by connecting multiple voltage divider capacitors in series, which allows for adjustment of the voltage divider output ratio and has a wider range of applications. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating insufficient distance between adjacent devices during an AC withstand voltage test.

[0029] Figure 2 This is a schematic diagram of one embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of an equivalent circuit according to one embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of another embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of an equivalent circuit according to another embodiment of the present invention;

[0033] Figure 6 A three-dimensional structural diagram of a capacitor voltage divider device;

[0034] Figure 7 This is a schematic diagram of the capacitor voltage divider from the front view.

[0035] Wherein: 1. Test device, 2. Adjacent device, 3. Voltage divider module, 4. Capacitive voltage divider device, 41. Base, 42. Insulating cylinder, 43. Supporting insulating rod, 44. Voltage divider capacitor bank, 45. Connecting flange, 46. Equalizing ring, 47. Adjustable support foot, S. AC power supply, V. Frequency converter cabinet, T1. Excitation transformer, L1. First reactor, L2. Second reactor, C2. Equivalent capacitance of adjacent device, C1. Equivalent capacitance of test device, C3. Voltage divider, C0. Equivalent capacitance of capacitive voltage divider device. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0037] Because test transformers for voltage levels of 500kV and above are large and inconvenient to transport, series resonant test devices are currently commonly used in high-voltage AC withstand voltage tests. Series resonant devices are further divided into inductance-tuned and frequency-tuned types. Due to the manufacturing difficulties, short service life, and large size of inductance-tuned test devices, frequency-modulated series resonant test devices are now more commonly used.

[0038] During the test, the excitation transformer T1 is used to excite the series resonant circuit. The output frequency of the frequency converter V is adjusted so that the circuit inductance and capacitor resonate in series. The resonant voltage is the voltage applied to the test object.

[0039] High-voltage equipment generally includes a voltage divider C3 and a voltage divider module 3. The voltage divider module 3 contains a reactor group, which is often a series of multiple reactors. The voltage on each reactor is basically the same. For example, the field withstand voltage of 500kV HGIS is generally 2-3 reactors.

[0040] When the air gap between the device under test and the adjacent bushing is too small to meet the test safety distance, part of the voltage of the voltage divider module 3 is connected to the adjacent bushing. Due to the voltage divider principle, there will be an intermediate potential on the adjacent bushing during the test, which will reduce the voltage between the air gaps and ensure that the gaps are not broken down.

[0041] This invention provides an AC withstand voltage test device for preventing adjacent bushings from being damaged by voltage divider, comprising a frequency converter V, an excitation transformer T1, a voltage divider C3, and a device under test 1. The output terminal of the frequency converter V is connected to the input terminal of the excitation transformer T1. The withstand voltage test device also includes a voltage divider module 3, the input terminal of which is connected to the output terminal of the excitation transformer T1. The output side of the voltage divider module is provided with a first output terminal 301 and a second output terminal 302, wherein the first output terminal 301 is connected to the device under test 1 and the voltage divider C3, and the second output terminal 302 is connected to the adjacent device 2 of the device under test.

[0042] Implementation Method 1

[0043] Specifically, in this embodiment, the voltage divider module 3 is a reactor group, which uses the inductive voltage divider principle to achieve voltage division. The reactor group is composed of multiple reactor sections stacked sequentially. Each reactor section has a connector at its end. A suitable connector in the middle of the reactor group is directly connected to the adjacent bushing, so the voltage on the adjacent bushing is a portion of the reactor group's voltage. During the test, as the test voltage increases, the voltage U of the tested device... 试验 and the voltage U of the adjacent bushing 临近 Both will increase accordingly; the voltage between the tested device and the adjacent bushing is U. 试验 -U 临近 This reduces the gap voltage, thus preventing the gap from breaking down.

[0044] Implementation method one is as follows Figure 2 and Figure 3 As shown, voltage divider module 3 is a reactor group. The bottom connector of the lowest reactor in the reactor group is the input terminal of the voltage divider module, which is connected to the output terminal of the excitation transformer. The first output terminal 301 is located at the top connector of the uppermost reactor, and the second output terminal 302 is located at the top connector of other suitable reactors that are not the uppermost reactor.

[0045] Connect the adjacent bushing to a connector at the bottom of the reactor group, i.e., the second output terminal 302, using an expanded diameter conductor. The tap position of the reactor group 3 can be selected according to actual needs. Then, the voltage U2 on the adjacent bushing is the voltage on the second reactor L2 at the bottom, and the voltage U1 on the device under test is the voltage of the entire reactor group. In this way, the voltage between the device under test and the adjacent bushing is reduced (i.e., U1-U2), thereby reducing the probability of breakdown and improving the safety factor of the test.

[0046] When calculating the resonant frequency, first calculate the parallel capacitance of the equivalent capacitance C3 of the voltage divider and the equivalent capacitance C1 of the device under test. Then, connect it in series with the inductance L1 of the first reactor in the upper part to obtain the impedance Z1. Then, connect it in parallel with the equivalent capacitance C2 of the adjacent bushing to ground to obtain the impedance Z2. Finally, the sum of the impedance Z2 and the impedance of the inductance L2 of the second reactor in the lower part is zero, thus achieving resonance.

[0047] The following is an example.

[0048] The equivalent capacitances to ground of ungrounded nearby equipment, C2, are 1000pC, 2000pC, and 4000pC, respectively.

[0049] The equivalent capacitance C3 of the voltage divider is 1000pC, and the equivalent capacitance C1 of the test sample is 239pC.

[0050] The reactor group consists of 4 units connected in series, with the lower reactor L2 having an inductance of 47.7H and the upper reactor L1 having an inductance of 143.1H.

[0051] The resonant frequency was calculated using the series resonance principle described above and compared with the actual frequency. Then, the voltage U2 on the adjacent equipment and the voltage U1 on the test object were calculated using the high-voltage side current of the excitation transformer and compared with the actual voltage values. The test results are shown in Table 1.

[0052] Table 1. Test parameters and voltage values ​​for the examples.

[0053]

[0054]

[0055] As shown in the table, the calculated series resonant frequency is comparable to the actual frequency, and the calculated voltage values ​​of the lower reactor U2 (i.e., the voltage of the adjacent equipment) and the upper reactor U1 (i.e., the voltage of the test object) are also within a reasonable range. Using an oscilloscope to read the voltage waveforms of U1 and U2, their phases are basically the same, and there is no situation where the phase difference between the transformers is too large, indicating that this voltage division method is feasible.

[0056] Implementation Method 2

[0057] Specifically, the voltage divider module 3 in this embodiment includes a reactor group and a capacitor voltage divider device 4, which uses the capacitor voltage divider principle to achieve voltage division. The input terminal at the bottom of the reactor group is connected to the output terminal of the excitation transformer, and the top of the reactor group is connected to one end of the capacitor voltage divider device 4, which also serves as the first output terminal 301. The other end of the capacitor voltage divider device 4 serves as the second output terminal 302 and is connected to the adjacent device 2 of the device under test.

[0058] In this way, the capacitor voltage divider 4 is connected between the high voltage side and the adjacent bushing. Due to the principle of capacitor voltage division, there will be an intermediate potential on the adjacent bushing during the test, which will reduce the voltage between the gaps and ensure that the gaps are not broken down.

[0059] In addition to the conventional series resonance test setup, a capacitor voltage divider device 4 needs to be added. The two ends of the voltage-dividing capacitor bank 44 at the top of the capacitor voltage divider device 4 are connected to the high-voltage side of the reactor bank and the adjacent bushing, respectively. In this way, the equivalent capacitance C0 of the capacitor voltage divider device 4, the equivalent capacitance C2 of the adjacent bushing and its connected GIS portion to ground are connected in series. According to the principle of capacitor voltage division, U... 临近 =U 试验 *C0 / (C0+C2). Thus, U is obtained on the adjacent sleeve. 试验 A fixed proportion of potential.

[0060] Based on the equivalent capacitance C2 to ground of the adjacent bushing and its connected GIS section, select a suitable equivalent capacitance C0 for the capacitor voltage divider 4, generally making U 临近 1 / 4 to 1 / 2 U 试验 .

[0061] Generally, the equivalent capacitance C2 of the GIS part near the bushing and its connection is about 300 to 1000pF. The equivalent capacitance C0 of the capacitor voltage divider 4 can be selected in the range of 500 to 1000pF to meet the needs of most application scenarios.

[0062] During the test, as the output voltage V of the frequency converter cabinet increases, the voltage U of the test object also increases. 试验 and the voltage U of the adjacent bushing 临近 All of these will increase accordingly, and will always be in phase; the voltage between the test sample and the adjacent bushing is U. 试验 -U 临近 This reduces the gap voltage, thus preventing the gap from breaking down.

[0063] like Figure 4 and Figure 5 As shown, prepare the series resonance test apparatus and complete the test wiring according to the series resonance principle. The top of the reactor group in voltage divider device 3 is connected to the top of the bushing of the test object via an expanded diameter wire. The resonant voltage at the top of the reactor group is the voltage U applied to the test object. 试验 .

[0064] An additional capacitor voltage divider 4 is prepared as part of the voltage divider 3. An expanding-diameter wire is used to connect the top of the reactor assembly to the equalizing ring 46 at one end of the voltage-dividing capacitor bank 44 at the top of the capacitor voltage divider 4. Then, an expanding-diameter wire is used to connect the equalizing ring 46 at the other end of the voltage-dividing capacitor bank 44 at the top of the capacitor voltage divider 4 to the top of the adjacent bushing. This achieves a series connection between the voltage-dividing capacitor bank 44 at the top of the capacitor voltage divider 4, the adjacent bushing, and the connected GIS portion to ground.

[0065] Then the voltage U on the bushing 临近 =U 试验 *C0 / (C0+C2)

[0066] During the test, as the output voltage V of the frequency converter cabinet increases, the voltage U of the test object also increases. 试验 and the voltage U of the adjacent bushing 临近 All of these will rise accordingly.

[0067] Due to U 试验 and U 临近 Since they are in phase, the voltage between the test sample and the adjacent bushing is always U. 试验 -U 升压 This reduces the voltage between the air gaps and decreases the electric field strength in the gaps, thus ensuring that the gaps are not broken down.

[0068] For example, when conducting an on-site AC withstand voltage test on a new 500kV HGIS device, the test voltage is 740kV. Without this method, if nearby equipment is grounded, the voltage between the test object and the nearby equipment will be 740kV.

[0069] Using the method of this embodiment, the equivalent capacitance C2 to ground of the adjacent bushing and its connected GIS portion is approximately 400pF, and the equivalent capacitance C0 of the voltage divider capacitor bank of the capacitor divider device 4 is 1000pF. According to the principle of capacitive voltage division, the voltage U on the adjacent bushing... 临近 =U 试验 *C0 / (C0+C2)=2 / 7U 试验 During the withstand voltage test, the voltage between the test specimen and adjacent equipment is U. 试验 -2 / 7U 试验 =5 / 7U 试验 =528.6kV, which greatly reduces the potential difference between the gaps, reduces the electric field strength, and ensures test safety. At the same time, the voltage applied to the adjacent bushing is 211.4kV, which is much lower than the normal maximum operating voltage of 318kV of the adjacent bushing, and will not cause damage to the adjacent equipment.

[0070] like Figure 6 and Figure 7As shown, the capacitor voltage divider device 4 includes a base 41, an insulating cylinder 42, and a voltage divider capacitor bank 44. The insulating cylinder 42 is disposed on the base 41, and the voltage divider capacitor bank 44 is disposed on the insulating cylinder 42. Both ends of the voltage divider capacitor bank 44 are provided with equalizing rings 46. One equalizing ring 46 is connected to the top of the reactor group, and the other equalizing ring 46 is connected to the adjacent device 2 of the device under test 1.

[0071] The insulating cylinder 42 is vertically installed in the center of the base 41. Multiple insulating cylinders 42 can be connected in series as needed. In this embodiment, there are three insulating cylinders 42. The insulating cylinders 42 are made of insulating materials such as epoxy resin.

[0072] The base 41 is a cross-shaped base 41, and the base 41 is provided with multiple adjustable support feet 47.

[0073] The voltage divider capacitor bank 44 and the insulating cylinder 42 are arranged vertically, and the two ends of the voltage divider capacitor bank 44 are connected to the insulating cylinder 42 through the supporting insulating rod 43. The supporting insulating rod 43 is installed at an angle, with its bottom fixed to the insulating cylinder 42 and its top fixed to the equalizing rings 46 at both ends, mainly serving to support the voltage divider capacitor bank 44.

[0074] The voltage divider capacitor bank 44 is formed by connecting multiple voltage divider capacitors in series, which are fixed and connected by connecting flanges. The voltage divider capacitors are arranged horizontally and can be connected in series in multiple sections; in this embodiment, two sections are connected in series. The internal components of each voltage divider capacitor are capacitors in series and parallel configurations, while the external casing is a sealed cylindrical shape made of insulating materials such as epoxy resin. The inside of the voltage divider capacitor is filled with insulating gas or insulating oil. At both ends of the voltage divider capacitor are equalizing rings 46 made of metal material, which serve to uniformly distribute the electric field and facilitate lead connection. A connecting flange 45 connects the two voltage divider capacitor sections, primarily for connection and fixation.

Claims

1. An AC voltage withstand test device for preventing a nearby casing from being punctured by voltage division, characterized by, The voltage-withstanding test device comprises a variable frequency cabinet, an excitation transformer, a voltage divider and a device under test, the output end of the variable frequency cabinet is connected to the input end of the excitation transformer, the voltage-withstanding test device further comprises a voltage dividing module, the input end of the voltage dividing module is connected to the output end of the excitation transformer, the output side of the voltage dividing module is provided with a first output end and a second output end, wherein the first output end is connected to the device under test and the voltage divider, and the second output end is connected to the adjacent sleeve of the device under test, the voltage dividing module comprises a reactor group, and the reactor group is formed by sequentially stacking a plurality of reactors. The excitation transformer excites a series resonance circuit, the output frequency of the variable frequency cabinet is adjusted, the inductance and the capacitance in the circuit are in series resonance, and the resonance voltage is the voltage applied to the device under test; due to the voltage dividing principle, there is an intermediate potential on the adjacent sleeve during the test, so that the voltage between the air gaps is reduced, and the gaps are prevented from being broken down.

2. The AC voltage withstand test device of claim 1, wherein, The end of each reactor is provided with a connector, the bottom connector of the lowermost reactor is connected to the output end of the excitation transformer, the first output end is arranged at the top connector of the uppermost reactor, and the second output end is arranged at the top connector of any other reactor except the uppermost reactor.

3. The AC voltage withstand test apparatus according to claim 1, wherein The voltage dividing module further comprises a capacitor voltage dividing device, the input end of the bottom of the reactor group is connected to the output end of the excitation transformer, the top of the reactor group is connected to one end of the capacitor voltage dividing device and serves as the first output end, and the other end of the capacitor voltage dividing device serves as the second output end and is connected to the adjacent sleeve of the device under test.

4. The AC voltage withstand test apparatus according to claim 3, wherein The capacitor voltage dividing device comprises a base, an insulating cylinder and a capacitor voltage dividing group, the insulating cylinder is arranged on the base, the capacitor voltage dividing group is arranged on the insulating cylinder, and both ends of the capacitor voltage dividing group are provided with voltage equalizing rings, one of the voltage equalizing rings is connected to the reactor group, and the other voltage equalizing ring is connected to the adjacent sleeve of the device under test.

5. The AC voltage withstand test apparatus according to claim 4, wherein A plurality of insulating cylinders are arranged in sequence and vertically stacked.

6. The AC voltage withstand test apparatus for preventing a nearby casing from being punctured by a voltage according to claim 5, wherein The number of the insulating cylinders is three.

7. The AC voltage withstand test apparatus according to claim 4, wherein The base is a cross-shaped base.

8. The AC voltage withstand test apparatus according to claim 4, wherein A plurality of adjustable supporting legs are arranged on the base.

9. The AC voltage withstand test apparatus for preventing a nearby casing from being punctured by a voltage according to claim 4, wherein The capacitor voltage dividing group and the insulating cylinder are arranged vertically, and both ends of the capacitor voltage dividing group are connected to the insulating cylinder through inclined supporting insulating rods.

10. The AC voltage withstand test apparatus for preventing a nearby casing from being punctured by a partial pressure according to claim 4, wherein The capacitor voltage dividing group is formed by connecting a plurality of capacitor voltage dividing groups in series, and the capacitor voltage dividing groups are fixed and connected through connecting flanges.

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