Wide range zero flux current transformer

Abstract

The application discloses a wide-range zero-flux current transformer, which comprises a shell, a primary busbar arranged in the shell, a first group of zero-flux measuring units and a second group of zero-flux measuring units arranged in the shell, and a magnetic shielding layer arranged between the two groups of zero-flux measuring units. The first group of zero-flux measuring units comprises a first iron core and a second iron core for measuring a first current range; the second group of zero-flux measuring units comprises a third iron core and a fourth iron core for measuring a second current range, and the maximum rated current of the second current range is greater than that of the first current range; and the primary busbar simultaneously passes through the first iron core, the second iron core, the third iron core and the fourth iron core. The application integrates two zero-flux measuring units with different ranges in the same shell and shares the same primary busbar, realizes full-range high-precision measurement, and improves the compactness and signal synchronism of the structure.

Description

Technical Field

[0001] This application relates to the field of power system measurement technology, specifically to a wide-range zero-flux current transformer, and more particularly to a four-core integrated zero-flux current transformer that integrates two zero-flux measurement units with different ranges into the same mechanical structure. Background Technology

[0002] Zero-Flux Current Transformer (ZFCT) eliminates hysteresis and nonlinearity by introducing closed-loop feedback control to bring the bias magnetomotive force in the core to zero, thereby achieving wideband, high-precision current measurement from DC to high frequencies. A typical dual-core differential structure consists of two cores of identical material and size, sharing a common excitation source with their primary windings connected in reverse series. When the primary current is zero, the two cores are magnetized symmetrically, and the detection winding output is zero. When the primary current is not zero, a bias magnetomotive force is generated, disrupting the symmetry, and the detection winding outputs an even-order harmonic, the amplitude of which is proportional to the bias magnetomotive force. By detecting this harmonic and driving the feedback winding to generate a compensation current, the bias magnetomotive force is brought closer to zero. Finally, the primary current is inferred by measuring the feedback current.

[0003] However, single-unit dual-core zero-flux current transformers have inherent dynamic range limitations. In the low-current region, when the primary current is 1% to 5% below the rated value, the second harmonic amplitude in the detection signal is extremely small, the signal-to-noise ratio drops sharply, and the measurement error increases significantly. In the high-current region, when the primary current exceeds the rated value by several times, the core enters a deep saturation region, the nonlinearity of the core increases sharply, the linear relationship between the bias magnetomotive force and the detection signal is disrupted, feedback control fails, and measurement distortion occurs. A single transformer cannot simultaneously achieve high sensitivity at low currents and a wide linear range.

[0004] To overcome the dynamic range limitations of a single current transformer, a parallel dual-transformer scheme has emerged in existing technologies. This scheme employs two independent zero-flux current transformers, one designed for a small range and the other for a large range, with the output selected via an external switching circuit or digital fusion. However, this scheme has significant drawbacks. First, the two independent devices occupy a large space, requiring two sets of housings, terminals, and mounting structures, resulting in complex wiring and higher overall size and cost. Second, the two transformers lack physical tight coupling, requiring the primary bus to pass through two separate core holes. This double core-passing increases the number of connection points, and the output signals of the two transformers exhibit uncertain phase delays, hindering high-precision weighted fusion. Third, the large-range transformer generates a strong leakage magnetic field during operation, which couples to the core and sensing winding of the small-range transformer, introducing additional common-mode or differential-mode interference and affecting the measurement accuracy of the small range. Existing solutions typically lack effective magnetic isolation measures. Finally, each independent device requires a separate excitation source, signal conditioning circuit, and power amplifier, resulting in low hardware resource utilization.

[0005] Therefore, there is an urgent need for a wide-range zero-flux current transformer that is compact, naturally synchronized, and has good electromagnetic isolation. Summary of the Invention

[0006] The embodiments of this disclosure provide a wide-range zero-flux current transformer to at least solve the technical problems existing in the prior art, such as the limited dynamic range of a single-group zero-flux current transformer, the large size of the dual-transformer parallel scheme, phase asynchrony, severe electromagnetic interference, and low hardware resource utilization.

[0007] According to an embodiment of this disclosure, a wide-range zero-flux current transformer is provided, comprising: a housing; a primary busbar passing through the housing; a first set of zero-flux measurement units disposed within the housing for measuring a first current range; wherein the first set of zero-flux measurement units includes a first iron core and a second iron core, and the primary busbar passes through the first iron core and the second iron core; a second set of zero-flux measurement units disposed within the housing for measuring a second current range, wherein the maximum rated current of the second current range is greater than the maximum rated current of the first current range; wherein the second set of zero-flux measurement units includes a third iron core and a fourth iron core, and the primary busbar passes through the third iron core and the fourth iron core; and a magnetic shielding layer disposed between the first set of zero-flux measurement units and the second set of zero-flux measurement units.

[0008] Optionally, the first iron core, the second iron core, the third iron core, and the fourth iron core are all annular iron cores and are coaxially arranged; the first iron core and the second iron core are arranged sequentially along the axial direction of the primary generatrix and are located in the inner layer in the radial direction; the third iron core and the fourth iron core are arranged sequentially along the axial direction of the primary generatrix and are located in the outer layer in the radial direction; and the geometric centers of the first iron core, the second iron core, the third iron core, and the fourth iron core coincide.

[0009] Optionally, the first iron core, the second iron core, the third iron core, and the fourth iron core are all annular iron cores and are coaxially arranged, and the four are arranged sequentially along the axial direction of the primary busbar.

[0010] Optionally, the permeability of the first and second iron cores is higher than that of the third and fourth iron cores, and the saturation magnetic flux density of the third and fourth iron cores is higher than that of the first and second iron cores.

[0011] Optionally, the number of turns of the windings on the first and second iron cores is greater than the number of turns of the corresponding windings on the third and fourth iron cores.

[0012] Optionally, the excitation frequency of the first group of zero flux measurement units is higher than the excitation frequency of the second group of zero flux measurement units.

[0013] Optionally, the magnetic shielding layer is made of permalloy or nanocrystalline ribbon, and the magnetic shielding layer has a ring structure or a plate structure; the magnetic shielding layer covers at least the full height of the first iron core, the second iron core, the third iron core and the fourth iron core along the axial direction of the primary busbar.

[0014] Optionally, the first group of zero flux measurement units and the second group of zero flux measurement units share a set of feedback power amplifiers, and drive their respective feedback windings in a time-sharing manner through a switching switch.

[0015] Optionally, an insulating sleeve is provided between the primary busbar and the inner holes of the first iron core, the second iron core, the third iron core, and the fourth iron core.

[0016] Optionally, a temperature sensor is also provided inside the housing for monitoring the core temperature.

[0017] The wide-range zero-flux current transformer proposed in this application integrates the first and second sets of zero-flux measurement units into the same housing, shares a primary bus, and has a built-in magnetic shielding layer. This integrated structure significantly reduces the device size and installation complexity. The shared primary bus ensures that the responses of the two sets of zero-flux measurement units to the same current are naturally synchronized, providing a physical basis for subsequent signal fusion. The built-in magnetic shielding layer suppresses electromagnetic interference from the second set of zero-flux measurement units to the first set. Through differentiated design of core materials, dimensions, and winding parameters, the first set of zero-flux measurement units specializes in high-precision measurement of small currents, while the second set covers a wide range of measurement of large currents. The two complement each other to achieve high precision across the entire measurement range. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of this disclosure and form part of this application, illustrate exemplary embodiments of this disclosure and are used to explain this disclosure, but do not constitute an undue limitation of this disclosure. In the drawings: Figure 1 This is a schematic diagram of the appearance of the wide-range zero-flux current transformer according to the embodiments of this application; Figure 2 This is a cross-sectional schematic diagram of a wide-range zero-flux current transformer according to an embodiment of this application; Figure 3 This is a partial structural schematic diagram of a wide-range zero-flux current transformer according to an embodiment of this application. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of this disclosure, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0020] Example According to a first aspect of this embodiment, a wide-range zero-flux current transformer is provided. Figure 1 A schematic diagram of the appearance of this wide-range zero-flux current transformer is shown. Figure 2 A cross-sectional view of this wide-range zero-flux current transformer is shown. Figure 3 A partial structural schematic diagram of this wide-range zero-flux current transformer is shown. (Reference) Figures 1 to 3As shown, the wide-range zero-flux current transformer includes: a housing 1; a primary busbar 2 passing through the housing 1; a first set of zero-flux measurement units 3 disposed within the housing 1 for measuring a first current range; wherein the first set of zero-flux measurement units 3 includes a first iron core 31 and a second iron core 32, and the primary busbar 2 passes through the first iron core 31 and the second iron core 32; a second set of zero-flux measurement units 4 disposed within the housing 1 for measuring a second current range, wherein the maximum rated current of the second current range is greater than the maximum rated current of the first current range; wherein the second set of zero-flux measurement units 4 includes a third iron core 41 and a fourth iron core 42, and the primary busbar 2 passes through the third iron core 41 and the fourth iron core 42; and a magnetic shielding layer 5 disposed between the first set of zero-flux measurement units 3 and the second set of zero-flux measurement units 4.

[0021] In this embodiment, the wide-range zero-flux current transformer mainly includes a housing 1, a primary busbar 2, a first set of zero-flux measurement units 3, a second set of zero-flux measurement units 4, and a magnetic shielding layer 5 disposed between the two. The housing 1 serves as an integral housing structure, internally accommodating the first set of zero-flux measurement units 3, the second set of zero-flux measurement units 4, and the magnetic shielding layer 5. The housing 1 has through holes for the primary busbar 2 to pass through and is equipped with secondary terminals. The housing 1 can be made of cast aluminum alloy and is divided into upper and lower halves for sealing and waterproofing. The secondary terminals can be aviation connectors, used to lead out the excitation signals, detection signals, and feedback signals of the first set of zero-flux measurement units 3 and the second set of zero-flux measurement units 4, respectively.

[0022] The primary busbar 2 is a single conductor that passes through the central holes of the first iron core 31, the second iron core 32, the third iron core 41, and the fourth iron core 42. To achieve good conductivity, the primary busbar 2 can be a solid or hollow copper conductor, and its surface can be plated with silver to reduce contact resistance. Standard terminals are provided at both ends of the primary busbar 2 for series connection with external primary circuits. Insulating supports or insulating sleeves are provided between the primary busbar 2 and the housing 1, and between the primary busbar 2 and the inner holes of each iron core, to ensure electrical isolation between the primary and secondary circuits.

[0023] The first set of zero flux measurement units 3 and the second set of zero flux measurement units 4 are both housed within the housing 1. They are used to measure the first current range and the second current range, where the maximum rated current is greater than the first current range, respectively. The first set of zero flux measurement units 3 includes a first iron core 31 and a second iron core 32, and the second set of zero flux measurement units 4 includes a third iron core 41 and a fourth iron core 42. The primary busbar 2 passes through the four iron cores in sequence.

[0024] The first iron core 31 and the second iron core 32 together form a set of dual-core differential structures, on which excitation windings, detection windings, and feedback windings are wound. The excitation winding is used to apply a high-frequency sinusoidal excitation voltage; the detection winding is used to sense the differential signal caused by the bias magnetomotive force of the first iron core 31 and the second iron core 32; the feedback winding is used to inject a compensation current, the magnetomotive force generated by this compensation current being opposite in direction to the bias magnetomotive force generated by the primary current, so as to maintain the bias magnetomotive force tending towards zero. The excitation signal, detection signal, and feedback signal of the first set of zero flux measurement units 3 are led out through the secondary terminals on the housing 1.

[0025] Similarly, the third core 41 and the fourth core 42 of the second group of zero flux measurement units 4 together constitute another set of dual-core differential structures. Both are wound with excitation windings, detection windings, and feedback windings, and their working principle is the same as that of the first group of zero flux measurement units 3. The excitation signal, detection signal, and feedback signal of the second group of zero flux measurement units 4 are also led out through the secondary terminals on the housing 1. The detection signals of the first group of zero flux measurement units 3 and the second group of zero flux measurement units 4 are independently led out to their respective signal processing circuits, or sent to the same digital processor for fusion calculation through a multi-channel analog-to-digital converter.

[0026] The magnetic shielding layer 5 is located between the first group of zero flux measurement units 3 and the second group of zero flux measurement units 4. It is made of a high-permeability material and is used to guide most of the magnetic field lines of the leakage magnetic field generated by the second group of zero flux measurement units 4 into the interior of the shielding layer, thereby reducing the degree to which the leakage magnetic field penetrates into the first group of zero flux measurement units 3. The magnetic shielding layer 5 covers at least the full height of four iron cores along the axial direction of the primary busbar 2, and has openings or gaps to avoid forming closed short-circuit loops and generating eddy current losses.

[0027] Through the above configuration, this embodiment integrates the first group of zero flux measurement units 3 and the second group of zero flux measurement units 4 into the same housing 1 and shares a primary bus 2, effectively reducing the overall volume and simplifying the installation process. At the same time, the shared primary bus 2 ensures that the responses of the two groups of zero flux measurement units to the same current are completely aligned in time, with no phase delay or sampling time difference, providing a physical basis for subsequent weighted fusion or seamless switching. In addition, the magnetic shielding layer 5 located between the two groups of zero flux measurement units can effectively suppress the coupling interference of the leakage magnetic field of the second group of zero flux measurement units 4 to the first group of zero flux measurement units 3, ensuring the measurement accuracy and stability of the first group of zero flux measurement units 3 in a strong magnetic field environment. The first group of zero flux measurement units 3 and the second group of zero flux measurement units 4 each achieve closed-loop feedback control through excitation winding, detection winding and feedback winding, and their ranges are complementary, jointly breaking through the dynamic range limitation of a single current transformer.

[0028] Optionally, the first iron core 31, the second iron core 32, the third iron core 41, and the fourth iron core 42 are all annular iron cores and are coaxially arranged; the first iron core 31 and the second iron core 32 are arranged sequentially along the axial direction of the primary busbar 2 and are located in the inner layer in the radial direction; the third iron core 41 and the fourth iron core 42 are arranged sequentially along the axial direction of the primary busbar 2 and are located in the outer layer in the radial direction; and the geometric centers of the first iron core 31, the second iron core 32, the third iron core 41, and the fourth iron core 42 coincide.

[0029] In this embodiment, the first iron core 31, the second iron core 32, the third iron core 41, and the fourth iron core 42 all adopt a ring structure, and the four iron cores are coaxially arranged with their geometric centers coinciding on the same axis. Specifically, the first iron core 31 and the second iron core 32 constitute the first group of zero flux measurement units 3, arranged sequentially along the axial direction of the primary generatrix 2, and both located in the radial inner layer; the third iron core 41 and the fourth iron core 42 constitute the second group of zero flux measurement units 4, also arranged sequentially along the axial direction of the primary generatrix 2, and both located in the radial outer layer. That is, the first iron core 31 and the second iron core 32 have smaller ring sizes and are arranged one after the other in the inner layer along the direction of the primary generatrix 2; the third iron core 41 and the fourth iron core 42 have larger ring sizes and are also arranged one after the other in the outer layer along the direction of the primary generatrix 2, forming a ring-shaped gap between the inner and outer iron cores. The magnetic shielding layer 5 is configured as a ring structure and is disposed within the annular gap, specifically between the outer periphery of the inner core and the inner side of the outer core. It is coaxially aligned with the cores, and the magnetic shielding layer 5 covers at least the full height of four cores along the axial direction of the primary busbar 2. The magnetic shielding layer 5 has axial openings or gaps to prevent the formation of closed short-circuit loops that could lead to eddy current losses. The primary busbar 2 passes sequentially through the central holes of the first core 31, the second core 32, the third core 41, and the fourth core 42 along the axial direction.

[0030] Thus, through a coaxial nested layout, the first set of zero flux measurement units 3 in the inner layer and the second set of zero flux measurement units 4 in the outer layer share the same axis, resulting in good magnetic circuit symmetry and high space utilization. The magnetic shielding layer 5 is placed in the annular gap between the inner and outer layers, which can effectively guide the leakage magnetic field lines generated by the outer core to the inside of the shielding layer, greatly reducing the degree of leakage magnetic field penetration into the inner core. This suppresses the magnetic coupling interference of the second set of zero flux measurement units 4 to the first set of zero flux measurement units 3 when working, ensuring the high accuracy and stability of the first set of zero flux measurement units 3 when measuring small currents.

[0031] Optionally, the first iron core 31, the second iron core 32, the third iron core 41 and the fourth iron core 42 are all annular iron cores and are coaxially arranged, and the four are arranged sequentially along the axial direction of the primary busbar 2.

[0032] In this embodiment, the first iron core 31, the second iron core 32, the third iron core 41, and the fourth iron core 42 all adopt a ring structure. The four iron cores are coaxially arranged and sequentially arranged along the axial direction of the primary busbar 2. That is, the four iron cores are arranged in a line in the direction through which the primary busbar 2 passes, and their central holes are all for the same primary busbar 2 to pass through. A gap is left along the axial direction between the first group of zero flux measurement units 3 and the second group of zero flux measurement units 4. The magnetic shielding layer 5 is a plate-shaped structure and is disposed in the gap, located between the first group of zero flux measurement units 3 and the second group of zero flux measurement units 4. The magnetic shielding layer 5 is made of a high-permeability material and is plate-shaped. Its coverage along the axial direction of the primary busbar 2 covers at least the full height of the four iron cores, so as to guide most of the magnetic field lines of the leakage magnetic field generated by the second group of zero flux measurement units 4 into the interior of the shielding layer, thereby playing a role in magnetic flux diversion. The primary busbar 2 passes through the first iron core 31, the second iron core 32, the magnetic shielding layer 5 (when the magnetic shielding layer is a plate-shaped structure and has through holes for the primary busbar to pass through), the third iron core 41, and the fourth iron core 42 in sequence along the axial direction.

[0033] Thus, through a side-by-side layout, the four iron cores are arranged sequentially along the axial direction of the primary busbar 2, with each iron core and winding distributed in the axial direction, leaving operating space between them, which facilitates winding and lead-out wiring, and is conducive to simplifying the production process and making daily maintenance convenient. At the same time, the plate-shaped magnetic shielding layer 5 is placed in the gap between the two sets of zero flux measurement units, which can also effectively suppress the coupling interference of the leakage magnetic field of the second set of zero flux measurement units 4 to the first set of zero flux measurement units 3.

[0034] Optionally, the permeability of the first iron core 31 and the second iron core 32 is higher than that of the third iron core 41 and the fourth iron core 42, and the saturation magnetic flux density of the third iron core 41 and the fourth iron core 42 is higher than that of the first iron core 31 and the second iron core 32.

[0035] In this embodiment, the first core 31 and the second core 32 of the first group of zero flux measurement units 3 differ from the third core 41 and the fourth core 42 of the second group of zero flux measurement units 4 in terms of material selection. Specifically, the first core 31 and the second core 32 are made of magnetic materials with high permeability, such as nanocrystalline alloys, while the saturation magnetic flux density of this material is relatively low; the third core 41 and the fourth core 42 are made of magnetic materials with high saturation magnetic flux density, such as oriented silicon steel, while the permeability of this material is relatively low. In terms of the geometric dimensions of the cores, the first core 31 and the second core 32 have smaller cross-sectional areas and shorter magnetic circuit lengths to meet the requirements of high sensitivity during small current measurements; the third core 41 and the fourth core 42 have larger cross-sectional areas and longer magnetic circuit lengths to meet the requirements of a wide linear range during large current measurements.

[0036] Therefore, the first set of zero-flux measurement units 3, due to the high permeability of its core material, can generate a strong detection signal under low-current conditions, making it specifically designed for high-sensitivity measurements in the low-current region. The second set of zero-flux measurement units 4, due to the high saturation magnetic flux density of its core material, is less prone to entering the saturation region under high-current conditions, enabling it to cover a wide range of linear measurements in the high-current region. The two sets complement each other in terms of material properties; the first set of zero-flux measurement units 3 focuses on improving sensitivity, while the second set focuses on expanding the linear range. Together, they overcome the dynamic range limitations of a single current transformer, achieving high-precision measurement across the entire measurement range. Furthermore, the core materials and geometric dimensions of the two sets of zero-flux measurement units can be independently optimized according to their respective range requirements, without mutual constraints, facilitating serialized development and flexible adaptation for different application scenarios.

[0037] Optionally, the number of turns of the windings on the first iron core 31 and the second iron core 32 is greater than the number of turns of the corresponding windings on the third iron core 41 and the fourth iron core 42.

[0038] In this embodiment, the number of turns in the excitation winding, the number of turns in the detection winding, and the number of turns in the feedback winding on the first core 31 and the second core 32 of the first group of zero flux measurement units 3 are all greater than the number of turns in the corresponding windings (i.e., excitation winding, detection winding, and feedback winding) on ​​the third core 41 and the fourth core 42 of the second group of zero flux measurement units 4. That is, the number of turns in the excitation winding on the first core 31 and the second core 32 is greater than the number of turns in the excitation winding on the third core 41 and the fourth core 42, the number of turns in the detection winding is greater than the number of turns in the detection winding on the third core 41 and the fourth core 42, and the number of turns in the feedback winding is also greater than the number of turns in the feedback winding on the third core 41 and the fourth core 42.

[0039] Thus, the first set of zero-flux measurement units 3, with its higher number of winding turns, increases the detection signal strength generated per ampere of current, resulting in a higher signal-to-noise ratio and measurement sensitivity in the low-current region. The second set of zero-flux measurement units 4, with its lower number of winding turns, reduces sensitivity but correspondingly achieves a wider linear measurement range and higher saturation current withstand capability. The number of winding turns for the two sets of zero-flux measurement units is independently set according to their respective range requirements, further strengthening the differentiation between them in terms of range division of labor. This makes the first set of zero-flux measurement units 3 suitable for precision measurement of small currents, while the second set of zero-flux measurement units 4 is suitable for wide-range measurement of large currents.

[0040] Optionally, the excitation frequency of the first group of zero flux measurement units 3 is higher than the excitation frequency of the second group of zero flux measurement units 4.

[0041] In this embodiment, the excitation frequency applied by the first group of zero flux measurement units 3 and the excitation frequency applied by the second group of zero flux measurement units 4 are set independently. Specifically, the first group of zero flux measurement units 3 uses a higher excitation frequency, for example, 10kHz to 50kHz; the second group of zero flux measurement units 4 uses a lower excitation frequency, for example, 1kHz to 5kHz. Each of the two groups of zero flux measurement units is configured with its own excitation source to achieve independent adjustment of the excitation frequency.

[0042] Thus, the first set of zero flux measurement units 3 further improves the signal-to-noise ratio under small signal conditions through a higher excitation frequency, which is beneficial for accurate detection of small currents; the second set of zero flux measurement units 4 reduces eddy current losses and temperature rise in the iron core through a lower excitation frequency, which is beneficial for long-term stable operation under high current conditions. The excitation frequencies of the two sets of zero flux measurement units can be independently optimized according to their respective iron core materials and measurement range requirements, without mutual constraints.

[0043] Optionally, the magnetic shielding layer 5 is made of permalloy or nanocrystalline ribbon, and the magnetic shielding layer 5 has a ring structure or a plate structure; the magnetic shielding layer 5 covers at least the full height of the first iron core 31, the second iron core 32, the third iron core 41 and the fourth iron core 42 along the axial direction of the primary busbar 2.

[0044] In this embodiment, the magnetic shielding layer 5 is made of permalloy (e.g., 1J85) or nanocrystalline ribbon. These materials have high magnetic permeability and can effectively concentrate and guide magnetic field lines. The specific structural form of the magnetic shielding layer 5 is determined according to the layout of the iron cores: for the aforementioned coaxial nested layout, the magnetic shielding layer 5 is configured as a ring structure, specifically a cylindrical shape, and is disposed in the annular gap between the outer periphery of the inner iron core (first iron core 31 and second iron core 32) and the inner side of the outer iron core (third iron core 41 and fourth iron core 42), and is coaxially arranged with the iron cores; for the aforementioned side-by-side layout, the magnetic shielding layer 5 is configured as a plate structure and is disposed in the axial gap between the first group of zero flux measurement units 3 and the second group of zero flux measurement units 4. Regardless of the structural form adopted, the coverage area of ​​the magnetic shielding layer 5 along the axial direction of the primary busbar 2 covers at least the full height of the four iron cores to ensure that most of the magnetic field lines of the leakage magnetic field generated by the second group of zero flux measurement units 4 are guided into the interior of the shielding layer. In addition, the magnetic shielding layer 5 has an axial opening or a gap to avoid forming a closed short-circuit ring and generating eddy current losses.

[0045] Thus, the magnetic shielding layer 5, through the flux shunting effect of the high-permeability material, effectively suppresses the coupling interference of the leakage magnetic field of the second group of zero-flux measurement units 4 to the first group of zero-flux measurement units 3, significantly reducing crosstalk and ensuring that the first group of zero-flux measurement units 3 can maintain high measurement accuracy and stability even under the strong magnetic field environment of the second group of zero-flux measurement units 4 with a large current. Simultaneously, the ring structure and plate structure are adapted to different core layouts, and the axial coverage of the shielding layer ensures the uniformity and integrity of the shielding effect at different axial positions.

[0046] Optionally, the first group of zero flux measurement units 3 and the second group of zero flux measurement units 4 share a set of feedback power amplifiers and drive their respective feedback windings in a time-sharing manner through a switching switch.

[0047] In this embodiment, the feedback windings of the first group of zero flux measurement units 3 and the second group of zero flux measurement units 4 are not each equipped with independent feedback power amplifiers, but rather share the same set of feedback power amplifiers. A switching switch, which can be an analog switch or a relay, is provided between them to selectively connect the output of the feedback power amplifier to either the feedback winding of the first group of zero flux measurement units 3 or the feedback winding of the second group of zero flux measurement units 4. In actual operation, when the primary current is within the first current range, the switching switch connects the feedback power amplifier to the feedback winding of the first group of zero flux measurement units 3, at which point the feedback winding of the second group of zero flux measurement units 4 is short-circuited or open-circuited; when the primary current exceeds the first current range, the switching switch switches to the feedback winding of the second group of zero flux measurement units 4.

[0048] Thus, the two sets of zero flux measurement units share a single feedback power amplifier through time-division multiplexing, which reduces the number of power amplifiers while ensuring their respective feedback control functions, thereby reducing hardware costs and circuit complexity and improving hardware resource utilization.

[0049] Optionally, an insulating sleeve 6 is provided between the primary busbar 2 and the inner holes of the first iron core 31, the second iron core 32, the third iron core 41 and the fourth iron core 42.

[0050] In this embodiment, an insulating sleeve 6 is provided at the position where the primary busbar 2 passes through the central holes of the four iron cores. The insulating sleeve 6 is sleeved on the outer periphery of the primary busbar 2 and located between the primary busbar 2 and the inner wall of each iron core's inner hole, electrically isolating the primary busbar 2 from each iron core. At the same time, an insulating support structure is also provided between the primary busbar 2 and the housing 1.

[0051] Thus, the insulating bushing 6 ensures electrical isolation between the primary circuit (primary busbar) and the secondary circuit (iron core and windings), preventing the high voltage of the primary busbar from being directly transmitted to the iron core and secondary circuit, effectively improving the safe and reliable operation of the equipment.

[0052] Optionally, a temperature sensor is also provided inside the housing 1 for monitoring the core temperature.

[0053] In this embodiment, a temperature sensor is also integrated inside the housing 1. This temperature sensor can be located near the first iron core 31, the second iron core 32, the third iron core 41, or the fourth iron core 42 to monitor the temperature changes of the iron cores in real time during operation. The detection signal from the temperature sensor can be led out through the secondary terminals on the housing 1 for acquisition by an external signal processing circuit or digital processor.

[0054] Therefore, by integrating temperature sensors, the system can acquire the operating temperature data of the iron core in real time, providing data support for subsequent temperature drift compensation and helping to further improve the measurement accuracy and long-term operational stability of the transformer over a wide temperature range.

[0055] The following provides specific application examples of the present invention. It should be noted that the specific parameters (current value, size, number of turns, etc.) in the following examples are for illustrative purposes only and do not constitute a limitation on the present invention.

[0056] In a specific example, the aforementioned wide-range zero-flux current transformer is applied to the DC bus current measurement of a converter station in a high-voltage direct current transmission line. In this example, the rated primary current of the first current range is ±50A, and the rated primary current of the second current range is ±5kA. The first core 31 and the second core 32 are made of 1K107 nanocrystalline toroidal cores with an outer diameter of 30mm, an inner diameter of 20mm, and a height of 10mm. The excitation winding on the first core 31 and the second core 32 has 200 turns, the detection winding has 500 turns, and the feedback winding has 100 turns. The excitation frequency of the first set of zero-flux measurement units 3 is 20kHz, and the excitation amplitude is 5V. The third core 41 and the fourth core 42 are 0.23mm thick grain-oriented silicon steel toroidal cores with an outer diameter of 120mm, an inner diameter of 80mm, and a height of 30mm. The excitation windings on the third core 41 and the fourth core 42 have 50 turns, the detection windings have 100 turns, and the feedback windings have 20 turns. The excitation frequency of the second set of zero flux measurement units 4 is 1kHz, and the excitation amplitude is 10V. The primary busbar 2 is a 15mm diameter copper rod with a silver-plated surface, passing through the central holes of the first core 31, the second core 32, the third core 41, and the fourth core 42. The magnetic shielding layer 5 is made of permalloy 1J85 wound into a cylindrical structure with a thickness of 1mm. Its radial position is between the outer periphery of the first set of zero flux measurement units 3 and the inner side of the second set of zero flux measurement units 4, and its axial position covers the full height of the four cores. The housing 1 is made of cast aluminum alloy, divided into upper and lower halves, and is sealed and waterproof. The secondary wiring terminals use aviation connectors, leading out the excitation signals, detection signals, and feedback signals of the first group of zero flux measurement units 3 and the second group of zero flux measurement units 4, respectively. In actual operation, when the absolute value of the primary current is less than 50A, the digital processor accepts the output of the first group of zero flux measurement units 3; when the absolute value of the primary current is greater than 70A, the digital processor accepts the output of the second group of zero flux measurement units 4. In the transition range of 50A to 70A, linear weighted fusion is used, with the weight of the first group of zero flux measurement units 3 decreasing linearly from 1 to 0, and the weight of the second group of zero flux measurement units 4 increasing from 0 to 1. This scheme achieves a measurement accuracy better than 0.05% across the entire current range of 0 to ±5kA.

[0057] Furthermore, according to a second aspect of this embodiment, a method for manufacturing a wide-range zero-flux current transformer is provided, comprising the following steps: winding excitation windings, detection windings, and feedback windings on a first iron core 31, a second iron core 32, a third iron core 41, and a fourth iron core 42 respectively, wherein the first iron core 31 and the second iron core 32 have the same number of turns, and the third iron core 41 and the fourth iron core 42 have the same number of turns; assembling the first iron core 31 and the second iron core 32 coaxially and connecting their detection windings in reverse series to form a first set of zero-flux measurement units 3. The third iron core 41 and the fourth iron core 42 are assembled coaxially and their detection windings are connected in reverse series to form the second set of zero flux measurement units 4; the magnetic shielding layer 5 is installed between the first set of zero flux measurement units 3 and the second set of zero flux measurement units 4; the primary busbar 2 is passed through the center holes of the first iron core 31, the second iron core 32, the third iron core 41 and the fourth iron core 42 in sequence, and an insulating sleeve 6 is set between the primary busbar 2 and the inner hole of each iron core; the assembled whole component is put into the housing 1, the insulating material is potted, the wiring terminals are installed, and the encapsulation is completed.

[0058] This application achieves at least the following beneficial effects through the above technical solution: (1) Improved structural integration and synchronization performance. This application integrates two zero-flux measurement units into one housing, sharing a single primary current bus. Compared to the scheme of two independent CTs, the overall volume is significantly reduced, and installation is more convenient, making it particularly suitable for space-constrained applications. More importantly, the shared physical primary bus ensures that the responses of the two measurement units to the same current are perfectly aligned in time, eliminating phase delays and sampling time differences between independent devices. This provides an ideal physical basis for achieving high-precision weighted fusion or seamless switching.

[0059] (2) Enhanced electromagnetic compatibility and anti-interference capability. This application sets a high-permeability magnetic shielding layer between the two sets of measurement units, which effectively suppresses the coupling interference of the leakage magnetic field generated by the large-range unit to the small-range unit during operation. Experimental results show that the shielding layer can significantly reduce crosstalk, thereby ensuring that the small-range unit can maintain high measurement accuracy and stability even in a strong magnetic field environment with a large current applied to the large-range unit.

[0060] (3) Improved measurement accuracy and design flexibility across the entire range. This application utilizes differentiated designs in core material, size, and winding turns ratio. The small-range unit specializes in high-sensitivity measurement in the low-current region, while the large-range unit covers a wide range of linear measurement in the high-current region. The two complement each other, breaking through the dynamic range limitation of a single current transformer and achieving high-precision measurement across the entire range. At the same time, the structural scheme of this application allows for flexible parameter adjustment according to different application requirements, enabling various range combinations. Furthermore, the optimized parameters of the two sets of measurement units are independent of each other and do not restrict each other, facilitating serial development.

[0061] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A wide-range zero-flux current transformer, characterized in that, include: Shell (1); A primary busbar (2) is installed in the housing (1). The first set of zero flux measurement units (3) is disposed inside the housing (1) and is used to measure the first current range; and the first set of zero flux measurement units (3) includes a first iron core (31) and a second iron core (32), and the primary bus (2) passes through the first iron core (31) and the second iron core (32). The second set of zero flux measurement units (4) is disposed inside the housing (1) and is used to measure the second current range. The maximum rated current of the second current range is greater than the maximum rated current of the first current range. The second set of zero flux measurement units (4) includes a third iron core (41) and a fourth iron core (42). The primary bus (2) passes through the third iron core (41) and the fourth iron core (42). as well as A magnetic shielding layer (5) is disposed between the first group of zero flux measurement units (3) and the second group of zero flux measurement units (4).

2. The wide-range zero-flux current transformer according to claim 1, characterized in that, The first iron core (31), the second iron core (32), the third iron core (41) and the fourth iron core (42) are all toroidal iron cores and are coaxially arranged; The first iron core (31) and the second iron core (32) are arranged sequentially along the axial direction of the primary busbar (2) and are located in the inner layer in the radial direction; The third iron core (41) and the fourth iron core (42) are arranged sequentially along the axial direction of the primary busbar (2) and are located in the outer layer in the radial direction; Furthermore, the geometric centers of the first iron core (31), the second iron core (32), the third iron core (41), and the fourth iron core (42) coincide.

3. The wide-range zero-flux current transformer according to claim 1, characterized in that, The first iron core (31), the second iron core (32), the third iron core (41) and the fourth iron core (42) are all ring-shaped iron cores and are coaxially arranged, and the four are arranged sequentially along the axial direction of the primary busbar (2).

4. The wide-range zero-flux current transformer according to claim 1, characterized in that, The permeability of the first iron core (31) and the second iron core (32) is higher than that of the third iron core (41) and the fourth iron core (42), and the saturation magnetic flux density of the third iron core (41) and the fourth iron core (42) is higher than that of the first iron core (31) and the second iron core (32).

5. The wide-range zero-flux current transformer according to claim 1, characterized in that, The number of turns of the windings on the first iron core (31) and the second iron core (32) is greater than the number of turns of the corresponding windings on the third iron core (41) and the fourth iron core (42).

6. The wide-range zero-flux current transformer according to claim 1, characterized in that, The excitation frequency of the first group of zero flux measurement units (3) is higher than that of the second group of zero flux measurement units (4).

7. The wide-range zero-flux current transformer according to claim 1, characterized in that, The magnetic shielding layer (5) is made of permalloy or nanocrystalline ribbon, and the magnetic shielding layer (5) is a ring structure or a plate structure; the magnetic shielding layer (5) covers at least the full height of the first iron core (31), the second iron core (32), the third iron core (41) and the fourth iron core (42) along the axial direction of the primary busbar (2).

8. The wide-range zero-flux current transformer according to claim 1, characterized in that, The first group of zero flux measurement units (3) and the second group of zero flux measurement units (4) share a set of feedback power amplifiers and drive their respective feedback windings in a time-sharing manner through a switching switch.

9. The wide-range zero-flux current transformer according to claim 1, characterized in that, An insulating sleeve (6) is provided between the primary busbar (2) and the inner holes of the first iron core (31), the second iron core (32), the third iron core (41) and the fourth iron core (42).

10. The wide-range zero-flux current transformer according to claim 1, characterized in that, The housing (1) is also equipped with a temperature sensor for monitoring the core temperature.

Images