Compensation capacitance box for error test of current transformer

Abstract

The utility model discloses a compensation capacitance box for error testing of a current transformer. The compensation capacitance box comprises a power factor unit, a combined capacitor unit and a resonance suppression unit, the power factor unit is arranged between the input ends or the output ends, the combined capacitor unit is arranged between the input ends or the output ends, the combined capacitor unit is located on one side of the power factor unit, and the resonance suppression unit is connected in a circuit of the combined capacitor unit in series; according to the utility model, the power factor unit and the combined capacitor unit are adopted, a real-time power supply power factor is monitored through the power factor unit, and the combined capacitor unit is used for connection or disconnection; a resonance suppression unit is further arranged, the circuit impedance is optimized by the resonance suppression unit, and the influence of harmonic waves on the circuit is reduced; the adjustable capacitor driven by the servo motor and the parallel RC damping loop work cooperatively, and the compensation capacitance and the circuit impedance are adjusted dynamically.

Description

Technical Field

[0001] This utility model relates to electrical testing equipment, and more specifically, to a compensation capacitor box for testing the error of a current transformer. Background Technology

[0002] In power systems, the error testing of current transformers for metering requires the use of voltage regulators, current boosters, and standard transformers. The principle is to connect the current transformer under test to a high-level standard current transformer according to the prescribed error test wiring, and then test the ratio difference and phase angle difference of the current transformer under test using a transformer calibrator.

[0003] As the transformation ratio of metering current transformers increases, the widespread use of directly supplying the current booster with the output voltage of the voltage regulator is common. However, because the current booster is an inductive device, this method results in a low output power factor for the voltage regulator, requiring high capacity from both the regulator and the test power supply. Another approach is to use a fixed capacitor connected in parallel to the power supply terminal of the current booster for power factor compensation. However, since the power factor of the current booster varies significantly depending on its application, the method of using a fixed capacitor in parallel for compensation is not ideal.

[0004] Existing technical defects: Traditional current booster tests use fixed compensation capacitors, which cannot adapt to a wide range of current changes (50A-10kA), resulting in power factor fluctuations exceeding ±0.178; it is difficult to match the compensation capacitor with the current booster impedance, which can easily lead to resonant overvoltage (reference case: voltage distortion rate reached 12% in a 110kV cable test); manual switching of capacitor banks is time-consuming, reducing test efficiency by more than 40%. Utility Model Content

[0005] One objective of this invention is to provide a new technical solution for a compensation capacitor box for testing the error of a current transformer.

[0006] According to a first aspect of the present invention, a compensation capacitor box for testing the error of a current transformer is provided, comprising a power factor unit, a combined capacitor unit, and a resonance suppression unit.

[0007] The power factor unit is disposed between the input terminal and the output terminal, the combined capacitor unit is disposed between the input terminal and the output terminal, and the combined capacitor unit is located on one side of the power factor unit, and the resonance suppression unit is connected in series in the circuit of the combined capacitor unit.

[0008] Furthermore, the power factor unit includes a current transformer for measuring the current component in the circuit, and a power factor meter for measuring the phase relationship between voltage and current in the circuit.

[0009] Furthermore, the current transformer is electrically connected to the current side of the circuit, and the two ends of the current transformer are respectively connected to the input current and the output current of the circuit. The power factor meter is connected to the voltage side of the circuit and is connected in parallel with the output terminal of the current transformer.

[0010] Furthermore, the combined capacitor unit includes a compensation module and a dynamic adjustment module, with the dynamic adjustment module connected in series with the compensation module.

[0011] Furthermore, the compensation module uses an MKP capacitor bank, and the dynamic adjustment module uses an adjustable capacitor driven by a servo motor.

[0012] Furthermore, the resonance suppression unit includes an adjustable reactor and an RC damping circuit. The adjustable reactor is connected in series with the MKP capacitor bank, and the RC damping circuit is connected in parallel with the adjustable reactor.

[0013] Furthermore, the MKP capacitor bank uses two voltage levels: 50kVar and 100kVar, and the withstand voltage of the MKP capacitor bank is 3kV. The capacitance range of the adjustable capacitor driven by the servo motor is continuously adjustable from 5 to 200kVar, and the resolution is 0.1kVar.

[0014] Furthermore, the adjustable reactor has an inductance adjustable from 0.1 to 5 mH, the resistor in the RC damping circuit has a resistance of 2 Ω ± 5%, and the capacitor has a value of 30 μF.

[0015] Furthermore, the adjustable capacitor driven by the servo motor consists of capacitors of different capacities connected in parallel with resistors and switches, with eight capacitors and eight resistors in each capacitor.

[0016] Furthermore, an ammeter is electrically connected to one side of the power factor meter.

[0017] According to one embodiment of this disclosure, a power factor unit and a combined capacitor unit are employed. The power factor unit consists of a small current transformer and a power factor meter, and the combined capacitor unit consists of capacitors of different capacities connected in parallel with resistors and switches.

[0018] The real-time power factor is monitored by the power factor unit. When the power factor is low, the switching on or off of the combined capacitor units of different capacities can be adjusted to compensate the current booster, so as to adjust the power factor and reduce the requirements of power supply capacity and voltage regulator capacity during the test.

[0019] Furthermore, it is equipped with a resonance suppression unit, which optimizes the circuit impedance and reduces the impact of harmonics on the circuit; the adjustable capacitor driven by the servo motor and the parallel RC damping circuit work together to dynamically adjust the compensation capacitance and circuit impedance in real time according to voltage fluctuations and load changes, so as to ensure power quality and system stability.

[0020] Other features and advantages of the present invention will become clear from the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings. Attached Figure Description

[0021] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the present invention and, together with their description, serve to explain the principles of the present invention.

[0022] Figure 1 This is a schematic diagram of the overall structure of a compensation capacitor box for testing the error of a current transformer in one embodiment. Detailed Implementation

[0023] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present invention.

[0024] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0025] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0026] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0027] like Figure 1 As shown, a compensation capacitor box for testing the error of a current transformer includes a power factor unit, a combined capacitor unit, and a resonance suppression unit.

[0028] The power factor unit is disposed between the input terminal and the output terminal, the combined capacitor unit is disposed between the input terminal and the output terminal, and the combined capacitor unit is located on one side of the power factor unit, and the resonance suppression unit is connected in series in the circuit of the combined capacitor unit.

[0029] In this embodiment, preferably, the power factor unit includes a current transformer for measuring the current component in the circuit, and a power factor meter for measuring the phase relationship between voltage and current in the circuit.

[0030] It should be noted that the current transformer is used to collect the current component in the measurement circuit, and the power factor is monitored in real time by the power factor meter. When the power factor is low, the switching on or off of capacitors of different capacities can be adjusted to compensate the current booster, so as to adjust the power factor and reduce the requirements of power supply capacity and voltage regulator capacity during the test.

[0031] In this embodiment, preferably, the current transformer is electrically connected to the current side of the circuit, the two ends of the current transformer are respectively connected to the input current and the output current of the circuit, and the power factor meter is connected to the voltage side of the circuit and is connected in parallel with the output terminal of the current transformer.

[0032] It should be noted that the current transformer is connected to the current side, which facilitates the acquisition of current by the measurement circuit. The power factor meter monitors the real-time power factor of the power supply through the current acquired by the current transformer.

[0033] In this embodiment, preferably, the combined capacitor unit includes a compensation module and a dynamic adjustment module, with the dynamic adjustment module connected in series with the compensation module; the compensation module uses an MKP capacitor bank, and the dynamic adjustment module uses an adjustable capacitor driven by a servo motor; the resonance suppression unit includes an adjustable reactor and an RC damping circuit, with the adjustable reactor connected in series with the MKP capacitor bank, and the RC damping circuit connected in parallel with the adjustable reactor;

[0034] It should be noted that the MKP capacitor bank, as a basic compensation unit, is used to capture and mitigate voltage fluctuations, providing initial capacitance compensation. The adjustable capacitor driven by the servo motor provides dynamically adjustable capacitance values, adjusting the capacitance in real time according to changes in input current and voltage, enhancing capacitance compensation capability, and adapting to different load conditions.

[0035] In this embodiment, preferably, the MKP capacitor bank uses two voltage levels: 50kVar and 100kVar, and the withstand voltage of the MKP capacitor bank is 3kV. The capacitance range of the adjustable capacitor driven by the servo motor is continuously adjustable from 5 to 200kVar, and the resolution is 0.1kVar.

[0036] It should be noted that the MKP capacitor bank's 50kVar / 100kVar dual-range adjustment provides greater flexibility, allowing selection of appropriate capacitance values ​​based on different load and voltage fluctuation conditions. Under high voltage fluctuations, a 100kVar capacitor is selected to provide stronger compensation capabilities; while under low fluctuations or low power demands, 50kVar is selected to reduce energy loss. This multi-range adjustment design enables the system to better adapt to dynamic changes and improve overall operating efficiency. The servo motor-driven adjustable capacitor's 5-200kVar capacitance range and 0.1kVar resolution provide precise adjustment, enabling rapid response to load changes and ensuring efficient system operation under various operating conditions. Whether it's grid fluctuations or load fluctuations, these parameters can be effectively addressed through dynamic adjustment, further enhancing the system's adaptability. The servo motor-driven adjustable capacitor, with its 0.1kVar resolution, can precisely adjust the capacitance, reducing energy loss during the adjustment process.

[0037] In this embodiment, preferably, the adjustable reactor has an inductance adjustable from 0.1 to 5 mH, the resistance of the resistor in the RC damping circuit is 2 Ω ± 5%, and the capacitance is 30 μF.

[0038] It should be noted that selecting an adjustable reactor with an inductance of 0.1-5mH and an RC damping circuit with a resistance of 2Ω±5% and a capacitance of 30μF can significantly improve the flexibility, response speed, harmonic suppression capability, and energy efficiency of the current booster. These advantages enable the current booster to provide higher power quality and system stability when facing different voltage fluctuations and load conditions.

[0039] The adjustable reactor has an inductance range of 0.1-5mH, which is adjustable and can dynamically adjust the inductance value according to different voltage fluctuation frequencies and intensities. For low-frequency voltage fluctuations (such as 50Hz or 60Hz), a lower inductance (such as 0.1-1mH) allows for a fast response; for high-frequency voltage fluctuations (such as 400Hz or higher), a higher inductance (such as 4mH-5mH) effectively absorbs energy. This flexible adjustment capability allows the current booster to adapt to various voltage fluctuation conditions. The combination of a 2Ω±5% resistor and a 30μF capacitor in the RC damping circuit can quickly absorb and dissipate energy during voltage fluctuations, providing... Effective voltage suppression; ±5% adjustment range of resistor value and precise setting of capacitor value ensure stable operation of the system under different voltage conditions; adjustment of inductance can quickly change the low-frequency response characteristics of the circuit, quickly absorb or release voltage fluctuations, and reduce the impact on the load; the combination of resistor and capacitor can quickly respond to voltage fluctuations, absorb energy and provide stable output, further improving the dynamic performance of the system; by adjusting the inductance value, the low-frequency response characteristics of the circuit are optimized, and the interference of harmonics on the system is reduced; the parallel RC damping circuit can quickly absorb high-frequency harmonic energy, reduce the harmonic content of the system, and improve the clean energy efficiency.

[0040] In this embodiment, preferably, the adjustable capacitor driven by the servo motor consists of capacitors of different capacities connected in parallel with resistors and switches, and eight capacitors and eight resistors are provided in each capacitor and resistor.

[0041] It should be noted that the values ​​of capacitors C1-C2 are 50μF, C3-C5 are 100μF, and C6-C7 are 100μF, and the resistance is 300kΩ, 2W. The setting of multiple sets of capacitors and resistors facilitates control and adjustment.

[0042] In this embodiment, preferably, an ammeter is electrically connected to one side of the power factor meter;

[0043] It should be noted that the ammeter is used to detect the current collected by the current transformer, and then the current value is displayed.

[0044] Intelligent matching algorithm:

[0045] Real-time acquisition of the current booster output current I, voltage U, and phase angle θ; calculation of dynamic compensation capacity requirements:

[0046]

[0047] Where Q represents the dynamic compensation capacity in kilowatt-hours (kVar), I represents the current in the circuit in amperes (A), U represents the voltage in the circuit in volts (V), θ represents the phase angle between the current and voltage in radians, sinθ represents the sine of the phase angle, dIdt represents the rate of change of current in amperes per second (A / s), and 1000As represents the unit conversion constant used to convert the rate of change of current from the actual measured value to the coefficient in the formula.

[0048] Security protection strategy:

[0049] When the harmonic content THD is detected to be ≥5%, the RC damping circuit is automatically activated and the capacitor adjustment mechanism is locked.

[0050] When the current mutation rate dI / dt ≥ 500 A / s, the fixed capacitor bank should be put into operation first for rapid compensation.

[0051] Performance improvements:

[0052] The power factor is stable in the range of 0.95-0.99 (a 15% improvement compared to traditional solutions);

[0053] During the 10kA test, the required voltage regulator capacity is reduced by 60% (originally a 500kVA voltage regulator is now only required to a 200kVA voltage regulator);

[0054] Reliability improvements:

[0055] The resonance occurrence rate is reduced by 90%; the capacitor bank switching response time is ≤50ms (compared to ≥200ms in traditional solutions).

[0056] Example 1: Cable Current Increase Test

[0057] A continuous current test of 5kA was conducted under a 220V / 50Hz power supply.

[0058] The compensation box operates as follows: when dI / dt = 800 A / s is detected, a 100 kVar fixed capacitor bank is activated first; the adjustable capacitor is adjusted to 72.3 kVar to complete accurate compensation; the final power factor PF = 0.98 and the voltage distortion rate THD = 2.1%.

[0059] Example 2: Resonance Suppression Test

[0060] The simulation system's impedance abruptly triggered the fifth harmonic resonance;

[0061] Protection system response:

[0062] The RC damping circuit is activated within 3ms;

[0063] Limit capacitor terminal voltage fluctuation to ≤±5% (traditional solutions ≥±15%).

[0064] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A compensating capacitor box for current transformer error testing, characterized by: The power factor unit, the combined capacitor unit, and the resonance suppression unit are included. The power factor unit is arranged between the input end and the output end, the combined capacitor unit is arranged between the input end and the output end, and the combined capacitor unit is arranged on one side of the power factor unit, and the resonance suppression unit is connected in series in the circuit of the combined capacitor unit.

2. The compensating capacitor box for testing error of current transformer according to claim 1, characterized in that: The current transformer for measuring the current component in the circuit is included in the power factor unit, and the power factor table for measuring the phase relationship between the voltage and the current in the circuit is included.

3. The compensating capacitor box for testing error of a current transformer according to claim 2, characterized in that: The current transformer is electrically connected to the current side of the circuit, the input current and the output current of the circuit are respectively connected to the two ends of the current transformer, and the power factor table is connected to the voltage side of the circuit and is connected in parallel with the output end of the current transformer.

4. The compensating capacitor box for testing error of a current transformer according to claim 1, characterized in that: The compensation module and the dynamic adjustment module are included in the combined capacitor unit, and the dynamic adjustment module is connected in series on the compensation module.

5. A compensating capacitor box for testing error of a current transformer according to claim 4, characterized in that: The MKP capacitor group is adopted as the compensation module, and the servo motor driven adjustable capacitor is adopted as the dynamic adjustment module.

6. The compensating capacitor box for testing error of a current transformer according to claim 5, characterized in that: The adjustable reactor and the RC damping circuit are included in the resonance suppression unit, the adjustable reactor is connected in series with the MKP capacitor group, and the RC damping circuit is connected in parallel with the adjustable reactor.

7. A compensating capacitor box for testing current transformers for error according to claim 6, characterized in that: The MKP capacitor group adopts two grades of 50kVar / 100kVar, the withstand voltage of the MKP capacitor group is 3kV, the capacity range of the servo motor driven adjustable capacitor is 5-200kVar continuously adjustable, and the resolution is 0.1kVar.

8. The compensating capacitor box for testing error of a current transformer according to claim 6, characterized in that: The inductance of the adjustable reactor is 0.1-5mH adjustable, the resistance value of the resistance in the RC damping circuit is 2Ω±5%, and the value of the capacitor is 30μF.

9. The compensating capacitor box for testing error of a current transformer according to claim 5, characterized in that: The servo motor driven adjustable capacitor is composed of capacitors with different capacities, resistors, and switches in parallel, and eight capacitors and eight resistors are arranged in the capacitors and the resistors.

10. The compensating capacitor box for testing error of a current transformer according to claim 2, characterized in that: One side of the power factor table is electrically connected with an ammeter.

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