A pressurized AC withstand voltage test device for preventing a near casing from being punctured

Abstract

The present application relates to a kind of AC withstand voltage test equipment of pressurized prevention of adjacent casing being broken, including frequency conversion cabinet, excitation transformer, booster transformer, reactor group, voltage divider, device under test, and the adjacent device of device under test side, the output end of frequency conversion cabinet is connected to the input end of excitation transformer and booster transformer respectively, the output end of excitation transformer is connected to the low voltage side of reactor group, the high voltage side of reactor group is connected to the high voltage side of voltage divider and the casing of device under test, the output end of booster transformer is connected to the casing top of adjacent device.Compared with prior art, the present application can be widely applied in the field of AC withstand voltage test under the condition of insufficient safety distance of adjacent casing and other non-grounded adjacent equipment, to ensure the safe performance of field test.

Description

Technical Field

[0001] This invention relates to AC withstand voltage testing equipment, and more particularly to a pressurized 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 acceptance testing and major overhaul. 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 testing. Series resonant devices are further divided into inductively modulated and frequency-modulated types. Due to the manufacturing difficulties, short service life, and large size of inductively modulated test devices, frequency-modulated series resonant test devices are now more commonly used.

[0003] In recent years, the field testing requirements of domestic technical standards have been gradually increasing, and the current field acceptance test voltage value has been raised to 100% of the factory test value. While the increased field acceptance test voltage value has no significant impact on the electrical isolation between internal breaks in GIS equipment, and relatively mature same-frequency and same-phase testing technologies already exist, the increased test value has a significant impact on external safety distances. Because the layout and distance of HGIS in typical substation designs have not increased, the insulation margin between the high-voltage section and adjacent equipment is reduced during field testing. This is particularly problematic during withstand voltage tests in expansion projects, where the already operational equipment is densely packed, posing a risk of air gap breakdown in confined spaces. The insufficient insulation margin is especially severe for 500kV HGIS equipment during AC withstand voltage tests.

[0004] Generally, the safe distance for 500kV equipment without power interruption is 5 meters. Relevant literature suggests that during AC withstand voltage tests of 550kV GIS or HGIS 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 pressurized AC withstand voltage test device to prevent 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 is insufficient, or when the safety distance between adjacent non-grounded equipment is insufficient.

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

[0009] An AC withstand voltage test device for preventing adjacent bushing breakdown by boosting the voltage includes a frequency converter cabinet, an excitation transformer, a step-up transformer, a reactor group, a voltage divider, a device under test, and an adjacent device next to the device under test. The output terminal of the frequency converter cabinet is connected to the input terminals of the excitation transformer and the step-up transformer, respectively. The output terminal of the excitation transformer is connected to the low-voltage side of the reactor group. The high-voltage side of the reactor group is connected to the high-voltage side of the voltage divider and the bushing of the device under test. The output terminal of the step-up transformer is connected to the top of the bushing of the adjacent device.

[0010] The low-voltage side of the voltage divider is grounded and used to measure the high voltage of the test system.

[0011] The input terminal of the frequency converter cabinet is connected to an AC power supply.

[0012] The rated voltage of the primary winding of the step-up transformer is the same as the rated voltage of the primary winding of the excitation transformer.

[0013] The rated voltage of the secondary winding of the step-up transformer is generally 10 to 20 times that of the rated voltage of the secondary winding of the excitation transformer.

[0014] The reactor assembly is connected to the high-voltage side of the voltage divider and the top of the bushing of the device under test via an expanded diameter conductor.

[0015] The input terminal of the step-up transformer is connected in parallel with the input terminal of the excitation transformer.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. Wide range of applications: It can be widely used in field AC withstand voltage tests when the safety distance between adjacent bushings is insufficient, as well as when the safety distance between adjacent non-grounded equipment is insufficient.

[0018] 2. Reliable and clear voltage increase: The increased voltage is directly connected to the bushing of the nearby device from the output terminal of the step-up transformer. The voltage value is directly determined by the turns ratio of the step-up transformer and the power supply. The voltage value is stable and reliable, and can be easily calculated and determined in advance.

[0019] 3. Easy to implement: Only an additional step-up transformer needs to be added to the existing series resonant test equipment. The high output voltage of the transformer is then introduced to the top of the bushing of a nearby device or other ungrounded nearby equipment. Step-up transformers are common test equipment; existing transformers can be used, eliminating the need to purchase new equipment.

[0020] 4. It can solve the problem of insufficient test safety distance for nearby bushings and ungrounded nearby equipment during on-site withstand voltage tests, ensuring the safe and smooth conduct of on-site tests. Attached Figure Description

[0021] Figure 1 A schematic diagram illustrating insufficient time intervals for expansion;

[0022] Figure 2 This is a schematic diagram of the structure of the present invention;

[0023] Figure 3 This is a schematic diagram of the equivalent circuit of the present invention;

[0024] Wherein: 1. Test device, 2. Adjacent device, S, AC power supply, V, frequency converter, T1, excitation transformer, T2, step-up transformer, L, reactor group, C1, equivalent capacitance of adjacent device, C2, equivalent capacitance of test device, C3, voltage divider. Detailed Implementation

[0025] 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.

[0026] During the test, an excitation transformer T1 is used to excite the series resonant circuit. The output frequency of the frequency converter V is adjusted to make the circuit inductance and capacitance resonate in series. The resonant voltage is the voltage applied to the test object. High-voltage equipment generally includes a voltage divider C3 and a reactor group L.

[0027] The concept of this application is as follows: when the gap between the bushings of the device under test and the adjacent device is too small to meet the test safety distance, an intermediate potential is added to the adjacent bushing to reduce the voltage between the gaps, thereby ensuring that the gaps are not broken down.

[0028] Specifically, such as Figure 2 and Figure 3As shown, an AC withstand voltage test device for preventing adjacent bushings from being broken down includes a frequency converter cabinet V, an excitation transformer T1, a step-up transformer T2, a reactor group L, a voltage divider C3, a device under test 1, and an adjacent device 2 next to the device under test. The output terminal of the frequency converter cabinet V is connected to the input terminals of the excitation transformer T1 and the step-up transformer T2, respectively. The output terminal of the excitation transformer T1 is connected to the low-voltage side of the reactor group L. The high-voltage side of the reactor group L is connected to the high-voltage side of the voltage divider C3 and the bushing of the device under test 1. The output terminal of the step-up transformer T2 is connected to the top of the bushing of the adjacent device 2.

[0029] In addition to the conventional series resonant test setup, a step-up transformer T2 was added. Both the step-up transformer T2 and the excitation transformer T1 are connected to the same output frequency converter V. This ensures that the primary windings of both transformers T2 and T1 are in phase, and their secondary output windings are also in phase with a higher output voltage. A suitable transformer ratio is selected for T2, such as a 180kV / 220kV single-phase test transformer on the high-voltage side, so that the output voltage of T2 during the withstand voltage test is a portion of the test voltage. Generally, the output voltage of T2 is 1 / 5 to 1 / 3 of the total test voltage, i.e., U... 升压 =1 / 5 to 1 / 3U 试 Verification.

[0030] A bushing is provided on the adjacent device 2 of the device under test 1, and the output terminal of the step-up transformer T2 is connected to this bushing. The output voltage of the step-up transformer T2 is directly applied to the adjacent bushing, so the voltage on the adjacent bushing is the output voltage U of the step-up transformer T2. 升压 During the test, as the output voltage V of the frequency converter cabinet increased, the voltage U of the test object also increased. 试验 and the voltage U of the adjacent bushing 升压 Both will increase accordingly; the voltage between the test sample and the adjacent bushing is U. 试验 -U 升压 This reduces the air gap voltage between the test sample and the adjacent bushing, thus ensuring that the gap is not broken down.

[0031] The input terminal of the frequency converter cabinet V is connected to the AC power supply S.

[0032] The low-voltage side of voltage divider C3 is grounded and used to measure the high voltage of the test system.

[0033] The rated voltage of the primary winding of the step-up transformer T2 is the same as the rated voltage of the primary winding of the excitation transformer.

[0034] The rated voltage of the secondary winding of the step-up transformer T2 is typically 10 to 20 times that of the rated voltage of the secondary winding of the excitation transformer. In some embodiments, the step-up transformer is a single-phase test transformer with a high-voltage side rated voltage of 110kV to 220kV.

[0035] The reactor assembly is connected to the high-voltage side of the voltage divider and the top of the bushing of the device under test via an expanded diameter conductor.

[0036] The input terminal of the step-up transformer is connected in parallel with the input terminal of the excitation transformer.

[0037] The specific test procedure is as follows: Prepare a series resonance test setup, including an AC power supply S, a frequency converter V, an excitation transformer T1, a reactor group L, and a voltage divider C3, and complete the test wiring according to the series resonance principle. The top of the reactor group L is connected to the top of the bushing of the device under test and the top of the voltage divider C3 via an expanded diameter wire. The resonant voltage at the top of the reactor group L is the voltage U applied to the test object. 试验 .

[0038] Prepare an additional step-up transformer T2 and connect the primary winding of the step-up transformer T2 to the output terminal of the frequency converter cabinet V, so that the step-up transformer and the excitation transformer have the same power supply.

[0039] Then, connect the high-voltage output terminal of the step-up transformer's output winding to the top of the nearest bushing using an expanded diameter conductor. The voltage across the nearest bushing is then the output voltage U of the step-up transformer. 升压 .

[0040] During the test, as the output voltage V of the frequency converter cabinet increases, the voltage U on the test object also increases. 试验 and the voltage U of the adjacent bushing 升压 All of these will rise accordingly.

[0041] The output voltage of the excitation transformer and the output voltage U of the step-up transformer 升压 The phases are the same; since both the excitation transformer secondary winding and the reactor group L are inductive elements, the resonant voltage U at the top of the reactor group L is... 试验 The phase of U is basically the same as the phase of the output voltage of the excitation transformer; therefore, U 试验 and U 升压 Their phases are basically the same.

[0042] Due to U 试验 and U 升压 Since their phases are basically the same, 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.

[0043] The invention obtains a high voltage with the same frequency and phase by connecting a step-up transformer T2 in parallel on the output side of the frequency converter cabinet V, and then applies this voltage to the adjacent bushing, so that the adjacent bushing has an increased intermediate potential, thereby reducing the voltage between the test object and the adjacent bushing, reducing the risk of the air gap being broken down and the withstand voltage test being unable to be carried out normally.

[0044] When using this application to conduct an on-site AC withstand voltage test on a 500kV HGIS device, the test voltage is 740kV. Without this method, if the nearby HGIS device is grounded, the voltage between the test object and the nearby bushing is 740kV.

[0045] Using a step-up transformer T2 with a rated input voltage of 350V and a rated output voltage of 200kV, when the resonant voltage of the reactor bank L circuit reaches 740kV, the output voltage of the step-up transformer is 140kV. Therefore, the voltage between the test object and adjacent equipment is 740kV - 140kV = 600kV, which significantly reduces the potential difference between the gaps, decreases the electric field strength between the gaps, and ensures test safety.

Claims

1. A pressurized AC withstand voltage test device for preventing adjacent bushings from being broken down, characterized in that, The system includes a frequency converter cabinet, an excitation transformer, a step-up transformer, a reactor group, a voltage divider, a device under test, and a bushing adjacent to the device under test. The output terminals of the frequency converter cabinet are connected to the input terminals of the excitation transformer and the step-up transformer, respectively. The output terminal of the excitation transformer is connected to the low-voltage side of the reactor group. The high-voltage side of the reactor group is connected to the high-voltage side of the voltage divider and the bushing of the device under test. The output terminal of the step-up transformer is connected to the top of the bushing of the adjacent bushing. The low-voltage side of the voltage divider is grounded and used to measure the high voltage of the test system. The rated voltage of the secondary winding of the step-up transformer is generally 10 to 20 times that of the rated voltage of the secondary winding of the excitation transformer; An excitation transformer is used to excite the series resonant circuit. The output frequency of the frequency converter is adjusted to make the circuit inductance and capacitance resonate in series. The resonant voltage is the voltage applied to the device under test. An intermediate potential is added to the adjacent bushings to reduce the voltage between the gaps and ensure that the gaps are not broken down.

2. The AC withstand voltage test equipment for preventing adjacent bushings from being broken down, as described in claim 1, is characterized in that, The input terminal of the frequency converter cabinet is connected to an AC power supply.

3. The AC withstand voltage test equipment for preventing adjacent bushings from being broken down, as described in claim 1, is characterized in that... The rated voltage of the primary winding of the step-up transformer is the same as that of the primary winding of the excitation transformer.

4. The AC withstand voltage test equipment for preventing adjacent bushings from being broken down according to claim 1, characterized in that, The reactor assembly is connected to the high-voltage side of the voltage divider and the top of the bushing of the device under test via an expanded diameter conductor.

5. The AC withstand voltage test equipment for preventing adjacent bushings from being broken down according to claim 1, characterized in that, The input terminal of the step-up transformer is connected in parallel with the input terminal of the excitation transformer.

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