CN214225406U - Test system for current transformer - Google Patents
Test system for current transformer Download PDFInfo
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- CN214225406U CN214225406U CN202022448317.5U CN202022448317U CN214225406U CN 214225406 U CN214225406 U CN 214225406U CN 202022448317 U CN202022448317 U CN 202022448317U CN 214225406 U CN214225406 U CN 214225406U
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Abstract
Embodiments of the present disclosure provide a test system for a current transformer. The test system comprises: the device comprises an energy storage power supply (10), a step-down transformer (20) and a test loop. The test loop is configured to be suitable for connecting the current transformer (30) to provide the current transformer (30) with current for short circuit performance testing. The energy storage power supply (10) comprises a first phase leg (12), a second phase leg (14) and a third phase leg (16), wherein each of the first phase leg (12), the second phase leg (14) and the third phase leg (16) comprises at least one power cell (100). The test system for the current transformer is low in cost and easy to implement.
Description
Technical Field
Embodiments of the present disclosure relate to a test system for a current transformer.
Background
Current transformers are widely used in power networks. A current transformer is generally connected in series in a line of a current to be measured, and converts a large primary-side current into a small secondary-side current by using the principle of electromagnetic induction to measure a circuit in the line. In order to meet safety requirements, the performance of current transformers has stringent standards and regulations, for example, current transformers must have the capability to withstand short-term overcurrents, which are typically much larger than current transformers.
The traditional short-circuit impact test system for the current transformer test system generally needs to use a generator set to supply power to provide short-time large current, the short-circuit impact test system comprises a motor, a generator and other equipment, the whole set of system needs to be matched with auxiliary equipment such as lubrication, protection and barring due to the fact that the whole set of system contains a rotating motor, and the manufacturing cost of the system is very high. Accordingly, it is desirable to provide a low cost test system for current transformers.
Disclosure of Invention
In view of the above, it is an object of the embodiments of the present disclosure to provide a testing system for a current transformer, which can solve at least one or more of the above technical problems in the prior art.
According to a first aspect of the present disclosure, a test system for a current transformer is provided. The test system comprises: an energy storage power supply comprising a three-phase ac power input adapted to receive a first capacity input and a single-phase ac power output adapted to provide a second capacity output greater than the first capacity; a step-down transformer coupled to the AC output of the energy storage power supply; and a test loop coupled to the step-down transformer, wherein the test loop is configured to connect the current transformer to provide the current transformer with current for short circuit performance testing; wherein the energy storage power supply comprises a first phase leg, a second phase leg, and a third phase leg, wherein each of the first phase leg, the second phase leg, and the third phase leg comprises at least one power cell, wherein each power cell comprises: an input coupled to the three-phase alternating current; a rectifier circuit coupled to the pair of input terminals and configured to convert the three-phase alternating current to direct current; a tank circuit configured to store the direct current; an inverter coupled to the tank circuit and configured to convert power from the tank circuit to alternating current; and an output coupled to the inverter.
According to the test system for the current transformer, when single-phase alternating current output can be provided, the problem of load asymmetry of the energy storage power supply can not be caused.
According to one embodiment of the present disclosure, each phase leg includes a plurality of power cells, output terminals of the plurality of power cells are connected in series with each other, and output terminals of the first phase leg, the second phase leg, and the third phase leg are wye-connected.
According to one embodiment of the present disclosure, the respective outputs of the first, second and third phase legs, which are wye connected, are shorted to form the single phase alternating current output. Therefore, the three-phase power supply capacity of the energy storage power supply can be fully utilized during single-phase output. The full capacity output can be achieved during single-phase output.
According to an embodiment of the present disclosure, the test system further comprises a contactor connected to the first, second and third phase legs, wherein the contactor is configured to short respective outputs of the first, second and third phase legs. Therefore, when single-phase output is carried out, the wiring does not need to be changed manually.
According to an embodiment of the present disclosure, each of the first, second and third phase legs comprises an LC filter, respectively. The output waveform of each phase can be smoother through an LC filter so as to obtain smaller harmonic voltage.
According to one embodiment of the disclosure, the current is in a range between 10-100 times a rated current of the current transformer.
According to one embodiment of the present disclosure, the tank circuit includes a tank capacitor having a capacitance of 1 μ F.
According to one embodiment of the present disclosure, the first capacity is less than 1kVA and the second capacity is in the range of 2kVA to 10 kilo kVA.
According to an embodiment of the present disclosure, the test loop further comprises a measurement unit adapted to measure an electrical parameter of the test loop, the measurement unit comprising a current measurement unit adapted to detect a current of the test loop and/or a voltage measurement unit adapted to detect a voltage of the test loop.
According to one embodiment of the present disclosure, the current measuring unit includes a rogowski coil, and the voltage measuring unit includes a first voltage dividing resistor and a second voltage dividing resistor.
According to an embodiment of the present disclosure, the test system further comprises a waveform recorder adapted to observe and/or record the measurement parameters of said measurement unit.
According to one embodiment of the present disclosure, the test system further comprises an isolation switch coupled between the energy storage power supply and the step-down transformer.
Compared with the prior art, the test system for the current transformer is low in cost and easy to implement.
Drawings
Embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:
FIG. 1 shows a test system circuit schematic for a current transformer according to an embodiment of the present disclosure;
FIG. 2 shows an internal circuit schematic of an energy storage power supply according to an embodiment of the disclosure; and
fig. 3 shows a circuit schematic of a power cell of an energy storage power supply according to an embodiment of the disclosure.
Detailed Description
Embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that the same reference numerals may be used in the drawings for similar components or functional elements. The accompanying drawings are only intended to illustrate embodiments of the present disclosure. Alternative embodiments will become apparent to those skilled in the art from the following description without departing from the spirit and scope of the disclosure.
The following describes a schematic circuit diagram of a test system for a current transformer according to an embodiment of the present disclosure with reference to the drawings.
As shown in fig. 1, a test system 1 for a current transformer includes an energy storage power supply 10, a step-down transformer 20, and a test loop. The test loop may be connected to a current transformer 30. The energy storage power supply 10 may be configured to provide a short-term, large capacity output. In some embodiments, the short-time large capacity output may be up to ten thousand kVA or even hundreds of thousands kVA.
The current transformer 30 may be connected in series in a test loop, and the test loop may be utilized to perform performance testing on the current transformer. These current transformers are arranged in the power network for measuring the current of the power network. The current transformer 30 may include a conductor and a measuring coil connected in series in the circuit under test. Since the current transformer 30 is an electric device well known in the art, a detailed description thereof will be omitted.
When a load loop of the power distribution network has a short-circuit fault, dozens of times or dozens of times of short-circuit current flows through the current transformer in the load loop. The short-circuit current will cause the current transformer to generate heat, possibly causing damage to the current transformer. In order to verify the performance of the current transformer in the short circuit, the short circuit performance of the current transformer can be tested through a short-time current test.
In some embodiments, the test circuit in the test loop through which the current transformer flows is tens of times, even tens of times, and in some embodiments, may be hundreds of times or even higher than the rated current of the current transformer.
In some embodiments, the energy storage power supply 10 can provide a test capacity of up to ten thousand kVA, hundreds of thousands kVA, or even millions of kVA. As mentioned in the background, the above-mentioned test capacity is difficult to achieve in a test condition environment that traditionally relies on a utility grid, and traditional test systems rely primarily on a complex and expensive power supply system including generators. The energy storage power supply provided by the embodiment of the disclosure can meet the test capacity requirement, and the cost of the test system can be greatly reduced.
In some embodiments, the energy storage power supply 10 receives a low capacity input and provides a short duration high capacity output. The energy storage power supply 10 may include an energy storage capacitor, with which energy storage and short-term release of energy may be achieved. In some embodiments, the time for the energy storage power supply to output current is in the order of seconds. The low capacity input may be, for example, less than 1kVA, which may be provided, for example, by a mains electricity distribution network, such as may be provided by 380V three-phase mains electricity; the large-capacity output can be in the range of 2kVA to 10 ten thousand kVA; in other embodiments, the large capacity output may be in the range of 30 kilo-kilo.
The output of the energy storage power supply 10 is stepped down by the step-down transformer 20, thereby converting the high-voltage low current of the primary coil into the low-voltage high current of the secondary coil. Therefore, power can be supplied to the test loop; the current outputted at the secondary side of the step-down transformer 20 may flow through the current transformer 30 to test the short circuit performance of the current transformer. In some embodiments, the energy storage power supply 10 may convert voltages of 10kV, tens of kV, or even hundreds of kV to voltages of tens of volts. Different step-down ratios of the step-down transformer may be provided depending on the capacity of the energy storage power source.
In operation of a test system according to embodiments of the present disclosure, a current transformer may be coupled to a test loop. After testing, electrical parameters of the current transformer may be measured and the mechanical structure of the current transformer observed to determine whether the current transformer meets performance requirements specified by a standard or specification.
In some embodiments, the test loop may comprise a measurement unit adapted to measure an electrical parameter of the test loop. In some embodiments, the measurement unit may comprise a current measurement unit adapted to detect the current of the test loop. As an example, in the illustrated embodiment, the current measurement unit may include a rogowski coil. It should be understood that this is merely exemplary and that the present disclosure may employ other current measuring units known in the art.
In other embodiments, the measurement unit may further comprise a voltage measurement unit adapted to detect the voltage of the test loop. As an example, in the illustrated embodiment, the voltage measuring unit includes a first voltage-dividing resistor and a second voltage-dividing resistor connected in parallel with the test loop, and the voltage of the test loop may be measured by measuring a node voltage between the first voltage-dividing resistor and the second voltage-dividing resistor. It should be understood that this is merely exemplary and that the present disclosure may employ various other voltage measurement units known in the art.
According to one embodiment of the present disclosure, as shown, the test system further comprises a waveform recorder 60 adapted to observe and/or record the measurement parameters of the measurement unit. For example, the measurement unit may be connected to a waveform recorder 60, and the waveform recorder 60 may record and/or display the measurements for analysis of whether the test parameters meet the requirements. It should be understood that the waveform recorder is merely exemplary and that other measurement parameter recording units or display units may be used.
According to one embodiment of the present disclosure, as shown, the test system may further include an isolation switch 70. An isolation switch 70 may be coupled between the energy storage power supply 10 and the step-down transformer 20. Via the isolating switch 70, control and/or protection can be implemented for the test loop, ensuring the safety of the test.
The energy storage power supply according to the embodiment of the disclosure is explained in detail with reference to fig. 2 and 3. Fig. 2 shows an internal circuit schematic of the energy storage power supply 10 according to an embodiment of the disclosure. Fig. 3 shows a schematic structural diagram of a power cell 100 according to an embodiment of the present disclosure.
The energy storage power supply 10 may comprise an ac input terminal receiving a first capacity input and an ac output terminal OUT adapted to provide a second capacity output greater than the first capacity. In some embodiments, the ac input may be coupled to a mains power distribution network and the ac output OUT may be coupled to a test system or a test loop according to embodiments of the present disclosure.
The energy storage power supply 10 may include a first phase leg 12, a second phase leg 14, and a third phase leg 16. Each of the first, second, and third phase legs 12, 14, 16 includes at least one power cell 100. In the illustrated embodiment, each phase leg includes a plurality of power cells 100.
The energy storage power supply 10 may include a phase shifting transformer (not shown). In the illustrated embodiment, a, b, c are a set of windings from a phase shifting transformer, and ac1, ac2 are the inverted outputs of the power cell. When SPWM pulse signals are applied to IGBT control electrodes g1, g2, g3 and g4, single-phase positive sine wave pulse width modulation output voltages can be obtained by the output ends ac1 and ac 2. The SPWM modulation signal is variable in frequency, for example the fundamental frequency can achieve an output frequency of 0.01Hz to 300 Hz. It should be understood that the above described inversion schemes are merely exemplary and that other inversion schemes known to those skilled in the art or developed in the future may be used.
As shown in fig. 3, each power cell 100 may include: an input 110 coupled to a three-phase alternating current; a rectifier circuit 120 coupled to the pair of input terminals and configured to convert the three-phase alternating current into direct current; a tank circuit 130 configured to store direct current; an inverter 140 coupled to the tank circuit 130 and configured to convert power from the tank circuit 130 into alternating current; and an output 150 coupled to the inverter 140.
The rectifying circuit 120 is adapted to convert alternating current received by the energy storage power supply 10 into direct current. In the illustrated embodiment, the rectification circuit 120 may include a full bridge rectifier bridge. The tank circuit 130 may include a tank capacitor. An appropriate energy storage capacitor may be selected according to the output capacity of the energy storage power supply 10. In some embodiments, the storage capacitor may be a 1 μ F storage capacitor. In some embodiments, the storage capacitor may be a 10 μ F, 100 μ F, 1000 μ F, 2000 μ F, 3000 μ F, 5000 μ F storage capacitor. It should be understood that this is merely exemplary and one skilled in the art can select an appropriate capacity of the storage capacitor as desired. The inverter 119 is adapted to convert the electric power from the tank circuit 130 into alternating current. The frequency and waveform of the modulation signal of the inverter 119 are adjusted to obtain a desired output waveform and voltage.
In the illustrated embodiment, the outputs of the N power cells per phase are connected in series, where N is 1 or an integer greater than or equal to. A high voltage output of nxv 1 volts is available between the head end of the first power cell and the tail end of the last power cell. In some embodiments, the outputs of the three phase legs may be wye-wired. Thus, a three-phase N × V1 × √ 3 volt output power source can be obtained. In other embodiments, the outputs of the three phase legs may be wired in other ways known in the art.
In the illustrated embodiment, the respective outputs of the wye-connected first, second and third phase legs 12, 14, 16 are shorted to form a single-phase ac output OUT. Therefore, single-phase alternating current can be led OUT from the terminal between the OUT and the N.
In some embodiments, the energy storage power supply 10 may include a contactor (not shown) that may be used to automatically short the 3 output terminals of the three-phase branch. Thus, the single-phase power is led OUT from the terminal between the OUT and the N of the contactor. In this case, the problem of load asymmetry in the power supply is not caused in the single-phase output, and the three-phase power supply capacity of the power supply can be fully utilized in the single-phase output. The full capacity output can be achieved during single-phase and three-phase output. The single-phase and three-phase output modes are automatically switched without manually changing the wiring.
Many modifications and other embodiments of the disclosure set forth herein will come to mind to one skilled in the art to which this disclosure pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the embodiments of the disclosure are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the disclosure. Moreover, while the above description and the related figures describe example embodiments in the context of certain example combinations of components and/or functions, it should be appreciated that different combinations of components and/or functions may be provided by alternative embodiments without departing from the scope of the present disclosure. In this regard, for example, other combinations of components and/or functions than those explicitly described above are also contemplated as within the scope of the present disclosure. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
Claims (10)
1. A test system for a current transformer, comprising:
an energy storage power supply (10) comprising a three-phase ac input adapted to receive a first capacity input and a single-phase ac output adapted to provide a second capacity output greater than the first capacity;
a step-down transformer (20) coupled to the alternating current output of the energy storage power supply (10); and
a test loop coupled to the step-down transformer (20), wherein the test loop is configured to connect the current transformer (30) to provide the current transformer (30) with current for a short circuit performance test;
wherein the energy storage power supply (10) comprises a first phase leg (12), a second phase leg (14) and a third phase leg (16),
wherein each of the first phase leg (12), the second phase leg (14) and the third phase leg (16) comprises at least one power cell (100),
wherein each power cell (100) comprises:
an input (110) coupled to the three-phase alternating current;
a rectifier circuit (120) coupled to the input and configured to convert the three-phase alternating current to direct current;
a tank circuit (130) configured to store the direct current;
an inverter (140) coupled to the tank circuit (130) and configured to convert power from the tank circuit (130) into alternating current; and
an output (150) coupled to the inverter (140).
2. The test system according to claim 1, wherein each phase leg comprises a plurality of power cells (100), the outputs (150) of the plurality of power cells (100) are connected in series with each other, and the outputs of the first phase leg (12), the second phase leg (14) and the third phase leg (16) are wye connected.
3. A test system according to claim 2, wherein the respective outputs of the first (12), second (14) and third (16) phase legs being wye connected are shorted to form the single phase alternating current output.
4. The test system according to claim 2, further comprising an output contactor connected to the first phase leg (12), the second phase leg (14) and the third phase leg (16), wherein the output contactor is configured to short respective outputs of the first phase leg (12), the second phase leg (14) and the third phase leg (16).
5. A test system according to claim 3, wherein each of the first phase branch (12), the second phase branch (14) and the third phase branch (16) comprises an LC filter, respectively.
6. A test system according to any of claims 1-5, characterized in that the current for short circuit performance test is in the range between 10-100 times the rated current of the current transformer (30).
7. The test system of claim 1, wherein the first capacity is less than 1kVA and the second capacity is in the range of 2kVA to 10 kilo-VA.
8. The test system according to any one of claims 1-5, wherein the test loop further comprises a measurement unit adapted to measure an electrical parameter of the test loop, the measurement unit comprising a current measurement unit (40) adapted to detect a current of the test loop and/or a voltage measurement unit adapted to detect a voltage of the test loop,
the current measuring unit comprises a Rogowski coil, and the voltage measuring unit comprises a first voltage dividing resistor and a second voltage dividing resistor.
9. The test system according to claim 8, further comprising a waveform recorder (60) adapted to observe and/or record the measurement parameters of the measurement unit.
10. The test system according to any one of claims 1-5, further comprising a disconnector (70) coupled between the energy storage power supply (10) and the step-down transformer (20).
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| CN202022448317.5U CN214225406U (en) | 2020-10-29 | 2020-10-29 | Test system for current transformer |
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| CN202022448317.5U CN214225406U (en) | 2020-10-29 | 2020-10-29 | Test system for current transformer |
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| CN214225406U true CN214225406U (en) | 2021-09-17 |
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