Adjustable multi-ratio current transformer for power systems

Abstract

The adjustable multiple-ratio current transformer suitable for power systems comprises a shell, two signal output terminals, a primary winding and a secondary winding arranged on the shell, the two signal output terminals are respectively named as a left signal output terminal and a right signal output terminal, there are at least two secondary windings, which are respectively a first secondary winding and a second secondary winding, the first secondary winding comprises a first left tap and a first right tap, the second secondary winding comprises a second left tap and a second right tap, and the adjustable multiple-ratio current transformer further comprises a circuit board arranged in the interior of the shell, the circuit board is provided with a first relay, a second relay and a third relay, and the relay has two control terminals, one wiring terminal and one controlled terminal. Through the arrangement of the two secondary windings, the relay can adjust the increase or decrease of the ratio through the switch, and a reliable current signal is provided for the protection device, thereby breaking the limitation of the fixed ratio of the traditional transformer.

Description

Technical Field

[0001] This utility model relates to power equipment, and in particular to current transformers. Background Technology

[0002] A current transformer (CT) is a key device used in power systems for measurement and protection. It primarily converts high currents to low currents proportionally for measurement or control. CTs can be categorized into measurement CTs that prioritize accuracy and typically require no high voltage when the secondary side is open, and protection CTs that prioritize saturation resistance and must maintain output under fault current conditions.

[0003] However, complex power systems have highly variable measurement and protection requirements, and the fixed ratio of traditional current transformers cannot meet these needs. The market urgently needs a current transformer with adjustable and multiple ratios. Utility Model Content

[0004] The purpose of this invention is to provide an adjustable multi-ratio current transformer suitable for power systems, in order to solve the problems existing in the prior art.

[0005] The above-mentioned technical objective of this utility model is achieved through the following technical solution:

[0006] An adjustable multi-ratio current transformer suitable for power systems includes a housing and two signal output terminals disposed on the housing, a primary winding and a secondary winding, both of which are disposed inside the housing;

[0007] The two signal output terminals are named the left signal output terminal and the right signal output terminal, respectively.

[0008] It has at least two secondary windings, namely a first secondary winding and a second secondary winding;

[0009] The number of turns in the first secondary winding is greater than the number of turns in the second secondary winding;

[0010] The first secondary winding includes a first left-side tap and a first right-side tap;

[0011] The second secondary winding includes a second left-side tap and a second right-side tap;

[0012] It also includes a circuit board disposed inside the housing;

[0013] The circuit board is equipped with a first relay, a second relay, and a third relay;

[0014] The relay has two control terminals, one wiring terminal, and one controlled terminal;

[0015] The first left tap is connected to the left signal output terminal;

[0016] The first right tap is connected to the terminal of the first relay, and the controlled terminal of the first relay is connected to the right signal output terminal.

[0017] The second left tap is connected to the terminal of the second relay, and the controlled terminal of the second relay is connected to the left signal output terminal.

[0018] The second right tap is connected to the terminal of the third relay, and the controlled terminal of the third relay is connected to the right signal output terminal.

[0019] By adopting the above technical solution, multiple different turns ratios can be obtained by adding taps during the winding of the secondary winding. The secondary winding is wound with insulated copper wire on an insulating cylinder fitted on the iron core. Taps of the secondary winding with different turns ratios are led out, and each tap is equipped with its own relay. This forms multiple turns ratios. At the same time, the number of turns of the first and second secondary windings are different and they are independent of each other, which meets the needs of different turns ratios and different accuracy levels under the same primary current. The relays can also be turned on or off according to the input of control signals, thereby improving or reducing the measurement accuracy with different turns ratios, adapting to different situations such as high measurement accuracy and low load. This breaks the limitation of the fixed turns ratio of traditional current transformers. Under different load and current conditions, it can also accurately measure and change the current, ensure the accurate readings of power system measuring instruments, provide reliable current signals for protection devices, effectively identify fault currents, and ensure the safe and stable operation of the system.

[0020] In a further embodiment, at least two segments of the primary winding are provided;

[0021] The number of turns in the primary winding is the same in both sections;

[0022] The two sections of the primary winding pass through the core of the current transformer, respectively.

[0023] The circuit board is also equipped with a first electronic control switch, a second electronic control switch and a third electronic control switch;

[0024] The electric control switch has two control terminals, one wiring terminal, and one controlled terminal;

[0025] The two primary winding sections are named the previous primary winding and the next primary winding, respectively;

[0026] The input terminal of the previous winding is connected to the terminal of the first electronic control switch, and the controlled terminal of the first electronic control switch is connected to the output terminal of the next winding.

[0027] The input terminal of the previous winding is connected to the terminal of the second electronic control switch, and the controlled terminal of the second electronic control switch is connected to the input terminal of the next winding.

[0028] The controlled terminal of the previous winding is connected to the terminal of the third electronic control switch, and the controlled terminal of the third electronic control switch is connected to the output terminal of the next winding.

[0029] By adopting the above technical solution, the primary winding is divided into two sections, which pass through the core of the transformer respectively, while the secondary winding is divided into two independent windings with taps and different accuracy classes. The primary winding is connected in series or in parallel by turning on or off the electronic control switch. By changing the number of turns of the primary winding, different turns ratios can be obtained. Since the tapped secondary winding itself is divided into two windings with different turns ratios and different accuracy classes, as the electronic control switch on the primary winding is changed, the number of turns of the primary winding changes accordingly, and its turns ratio also changes accordingly, forming turns ratios with multiple measurement accuracies.

[0030] In a further embodiment, the iron core is wound with a shielding strip to prevent secondary winding coupling interference;

[0031] The shielding strip includes insulating capacitor paper and semiconductor crepe paper;

[0032] The surface of the semiconductor crepe paper is bonded with insulating capacitor paper, and thermosetting conductive adhesive is disposed below the insulating capacitor paper. The shielding strip is bonded and fixed by the thermosetting conductive adhesive.

[0033] By adopting the above technical solution, the shielding strip effectively suppresses electromagnetic interference between secondary windings through a multi-layer composite structure. The insulating capacitor paper provides basic insulation performance, while the semiconductor crepe paper can absorb high-frequency stray magnetic fields. The combination of the two significantly reduces capacitive coupling and eddy current losses between windings. The thermosetting conductive adhesive forms a stable bonding layer after high-temperature curing, ensuring that the shielding strip is tightly attached to the iron core and avoiding shielding failure due to vibration. This design can adapt to some scenarios that require measurement accuracy, reduce signal distortion of current transformers in complex electromagnetic environments, and improve the fidelity of the output current waveform.

[0034] In a further embodiment, the relay is an optically isolated switch.

[0035] By adopting the above technical solution, the optical isolating switch achieves electrical isolation through the principle of optocoupler, completely blocking the direct electrical connection between the primary and secondary sides, avoiding the risk of high voltage entering the low voltage measurement circuit. It has a fast response speed, long life, and is not affected by electromagnetic interference, making it suitable for the rapid switching requirements of transient fault current in power systems. In addition, the optical isolation characteristics can prevent poor contact caused by relay contact oxidation, even in humid or dusty environments.

[0036] In a further embodiment, the relay is provided with a heat sink, which is made of aluminum.

[0037] The heat sink has a fin.

[0038] By adopting the above technical solution, the aluminum heat sink utilizes its high thermal conductivity to quickly dissipate the Joule heat during relay operation, while the fin structure enhances the air convection heat dissipation efficiency by increasing the surface area, preventing the relay from malfunctioning or having its lifespan shortened due to excessive temperature rise. This design is particularly suitable for situations where the internal space of a compact current transformer housing is limited. Passive heat dissipation can meet the temperature control requirements under long-term high-current conditions without the need for additional fans or cooling devices, thus reducing energy consumption and maintenance costs.

[0039] In a further embodiment, the right signal output terminal is a protective ground, and the grounding resistance is ≤4Ω.

[0040] By adopting the above technical solution, the low-impedance grounding output terminal provides a reliable equipotential reference point for the secondary side, which can quickly discharge transient overvoltages generated by lightning strikes or short-circuit faults, avoid equipment insulation breakdown, and strictly control the grounding resistance within 4Ω to ensure that the fault current is sufficient to trigger the protection device to operate. In addition, this design can effectively suppress common-mode interference and improve the noise immunity of the measurement signal. Especially in the case of frequency converters or electric arc furnaces with severe harmonic pollution, it can ensure the accuracy of current sampling and the response accuracy of the protection circuit.

[0041] In summary, this utility model has the following beneficial effects:

[0042] 1. By setting up secondary windings and relays, two independent primary and secondary windings can be used, with tap structures designed for each. Combined with relay control of the on / off state of different taps, the adjustable ratio of the current transformer is achieved. The primary and secondary windings have more turns, which is suitable for high-precision measurement scenarios, while the secondary windings have fewer turns, focusing on anti-saturation capability to meet protection requirements. The introduction of relays makes ratio switching unnecessary for physical operation, and can be responded to quickly by electrical signals. This solves the pain point that the fixed ratio of traditional current transformers cannot match the changing needs of power systems. This structure not only expands the measurement accuracy range, but also automatically adjusts the ratio when the measurement accuracy is exceeded or the load is low, ensuring the accuracy of the measuring instrument readings and the reliability of the protection device signals. It significantly improves the adaptability and safety of power system operation, and achieves the effect of flexibly switching ratios and adapting to complex operating conditions.

[0043] 2. By using a segmented primary winding and an electronically controlled switch, the primary winding can be divided into two segments with the same number of turns. The two segments can be flexibly switched between series and parallel connections by turning the electronically controlled switch on or off. In series connection, the total number of turns on the primary side is increased, reducing the turns ratio to accommodate large current measurements. In parallel connection, the equivalent number of turns is reduced, increasing the turns ratio for low-current scenarios. This design overcomes the limitation of the traditional fixed primary winding of instrument transformers. Combined with the multi-tap structure of the secondary winding, it forms a richer range of turns ratio combinations, making it particularly suitable for applications with frequent current fluctuations, such as new energy grid connection. It avoids measurement distortion at low currents and can withstand the impact of fault currents, balancing measurement accuracy and protection reliability. It provides hardware support for the dynamic needs of smart grids, effectively adjusting the number of primary turns and optimizing turns ratio combinations.

[0044] 3. By incorporating a shielding strip—composite of insulating capacitor paper and semiconductor crepe paper—wrapped around the iron core and fixed with thermosetting conductive adhesive, a multi-layer electromagnetic shielding system is formed. The insulating layer blocks capacitive coupling, while the semiconductor layer absorbs high-frequency stray magnetic fields, effectively reducing mutual interference between secondary windings. Simultaneously, the right signal output terminal employs a low-impedance protective grounding of ≤4Ω to quickly discharge transient overvoltages and establish a stable reference potential. The combined effect of these two factors significantly reduces noise interference introduced by harmonics, lightning strikes, or fault currents, ensuring the fidelity of the output signal waveform. This structure improves the power system's anti-interference capability and operational stability from a hardware perspective, effectively suppressing interference and ensuring signal purity. Attached Figure Description

[0045] Figure 1 This is a partial circuit diagram of the adjustable multi-ratio current transformer applicable to power systems according to this utility model.

[0046] In the diagram, 1 is the primary winding; 11 is the previous primary winding; 12 is the next primary winding; 2 is the secondary winding; 21 is the first secondary winding; 22 is the second secondary winding; 3 is the signal output terminal; 31 is the left signal output terminal; 32 is the right signal output terminal; 4 is the first relay; 5 is the second relay; 6 is the third relay; 7 is the first electronic control switch; 8 is the second electronic control switch; and 9 is the third electronic control switch. Detailed Implementation

[0047] The present invention will be further described in detail below with reference to the accompanying drawings.

[0048] Identical parts are indicated by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "upper," and "lower" used in the following description refer to the attached figures. Figure 1In this specification, the terms "bottom surface" and "top surface," "inner" and "outer" refer to the direction toward or away from the geometry of a specific component. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this specification, "a plurality of" means two or more, unless otherwise explicitly and specifically defined by the direction of the center.

[0049] like Figure 1 As shown, an adjustable multi-ratio current transformer suitable for power systems includes a housing and two signal output terminals 3, a primary winding 1, and a secondary winding 2 mounted on the housing. Both the primary winding 1 and the secondary winding 2 are located inside the housing. The two signal output terminals 3 are designated as left signal output terminal 31 and right signal output terminal 32, respectively. The transformer has at least two secondary windings 2, namely a first secondary winding 21 and a second secondary winding 22. The first secondary winding 21 has a greater number of turns than the second secondary winding 22. The first secondary winding 21 includes a first left-side tap and a first right-side tap, and the second secondary winding 22 includes a second left-side tap and a second right-side tap. It also includes a circuit board, which is located inside the housing. The circuit board has a first relay 4, a second relay 5, and a third relay 6. Each relay has two control terminals, one wiring terminal, and one controlled terminal. The first left tap is connected to the left signal output wiring terminal 31, the first right tap is connected to the wiring terminal of the first relay 4, and the controlled terminal of the first relay 4 is connected to the right signal output wiring terminal 32. The second left tap is connected to the wiring terminal of the second relay 5, and the controlled terminal of the second relay 5 is connected to the left signal output wiring terminal 31. The second right tap is connected to the wiring terminal of the third relay 6, and the controlled terminal of the third relay 6 is connected to the right signal output wiring terminal 32.

[0050] By adopting the above technical solution, multiple different turns ratios can be obtained by adding taps when winding the secondary winding 2. The secondary winding 2 is wound with insulated copper wire on an insulating cylinder fitted on the iron core. Taps of the secondary winding 2 with different turns ratios are led out, and each tap is equipped with its own relay. In this way, multiple turns ratios are formed. At the same time, the number of turns of the first secondary winding 21 and the second secondary winding 22 are different and independent, which meets the needs of different turns ratios and different accuracy levels under the same primary current. The relays can also be turned on or off according to the input of control signals, thereby improving or reducing the measurement accuracy with different turns ratios, adapting to different situations such as high measurement accuracy and low load, breaking the limitations of the fixed turns ratio of traditional current transformers. Under different load and current conditions, it can also accurately measure and change the current, ensure the accurate reading of power system measuring instruments, provide reliable current signals for protection devices, effectively identify fault currents, and ensure the safe and stable operation of the system.

[0051] This provides the hardware foundation for intelligent control systems (such as microprocessor systems) to intelligently adjust the transformation ratio and current intensity of current transformers by controlling the working state of each relay.

[0052] for example:

[0053] When only the first and second windings are used, the first relay 4 is closed, making the first right tap connected to the right signal output terminal 32, and the second relay 5 and the third relay 6 are disconnected, cutting off the connection of the second and second windings.

[0054] The current flows from the first left tap to the left signal output terminal 31, then to the load, then to the right signal output terminal 32, and finally to the first right tap, achieving the effect of only the first and second windings participating in the work and outputting a smaller secondary current.

[0055] When only the second secondary winding is used, the second relay 5 and the third relay 6 are closed, respectively connecting the second left tap to the left signal output terminal 31 and the second right tap to the right signal output terminal 32. The first relay 4 is opened, cutting off the right-side path of the first secondary winding.

[0056] The current flows from the second left tap to the left signal output terminal 31, then to the load, then to the right signal output terminal 32, and finally to the second right tap, achieving the effect of only the second secondary winding participating in the work and outputting a larger secondary current.

[0057] When the two secondary windings are connected in parallel, all relays are closed. The left taps of the first secondary winding and the second secondary winding are connected to the left signal output terminal 31, and the right taps are connected to the right signal output terminal 32.

[0058] The two windings are connected in parallel to share the load current. The equivalent number of turns is the parallel combination of the number of turns of the two windings. The output current is between that of using the high / low number of turns windings alone.

[0059] In a further embodiment, there are at least two primary windings 1, with the same number of turns. The two primary windings 1 pass through the core of the current transformer. The circuit board is also equipped with a first electronic control switch 7, a second electronic control switch 8, and a third electronic control switch 9. Each electronic control switch has two control terminals, one wiring terminal, and one controlled terminal. The two primary windings 1 are named the upper primary winding 11 and the lower primary winding 12, respectively. The input terminal of the upper primary winding 11 is connected to the wiring terminal of the first electronic control switch 7, and the controlled terminal of the first electronic control switch 7 is connected to the output terminal of the lower primary winding 12. The input terminal of the upper primary winding 11 is connected to the wiring terminal of the second electronic control switch 8, and the controlled terminal of the second electronic control switch 8 is connected to the input terminal of the lower primary winding 12. The controlled terminal of the upper primary winding 11 is connected to the wiring terminal of the third electronic control switch 9, and the controlled terminal of the third electronic control switch 9 is connected to the output terminal of the lower primary winding 12.

[0060] By adopting the above technical solution, the primary winding 1 is divided into two sections, which pass through the core of the current transformer respectively, while the secondary winding 2 is divided into two independent windings with taps and different accuracy classes. The primary winding 1 is connected in series or in parallel by turning on or off the electronic control switch. By changing the number of turns of the primary winding 1, different turns ratios can be obtained. Since the secondary winding 2 with taps is itself divided into two windings with different turns ratios and different accuracy classes, as the electronic control switch on the primary winding 1 is changed, the number of turns of the primary winding 1 changes accordingly, and its turns ratio also changes accordingly, forming a turns ratio with multiple measurement accuracies.

[0061] for example:

[0062] Two primary windings are connected in series. The second electronic control switch 8 is closed, connecting the input terminal of the previous primary winding 11 to the output terminal of the next primary winding 12. The second electronic control switch 9 is closed, connecting the output terminal of the previous primary winding 11 to the output terminal of the next primary winding 12. The first electronic control switch 7 is open to avoid short circuit. This can increase the number of turns on the primary side and reduce the secondary current, which is suitable for high turns ratio measurement (such as high current system).

[0063] Two primary windings are connected in parallel. The first electronic control switch 7 is closed, connecting the input terminal of the upper primary winding 11 to the output terminal of the lower primary winding, and opening the second electronic control switch 8 and the third electronic control switch 9 to avoid short circuit. This allows the equivalent number of turns on the primary side to remain unchanged, but allows a larger primary current to pass through, which is suitable for low turns ratio measurement (such as small current system).

[0064] In addition, it can be linked with the secondary winding for more flexible turns ratio combinations.

[0065] In a further embodiment, a shielding strip is wound around the iron core to avoid coupling interference of the secondary winding 2. The shielding strip includes insulating capacitor paper and semiconductor crepe paper. The insulating capacitor paper is bonded to the surface of the semiconductor crepe paper, and thermosetting conductive adhesive is disposed under the insulating capacitor paper. The shielding strip is bonded and fixed by the thermosetting conductive adhesive.

[0066] By adopting the above technical solution, the shielding strip effectively suppresses electromagnetic interference between the secondary windings 2 through a multi-layer composite structure. The insulating capacitor paper provides basic insulation performance, while the semiconductor corrugated paper can absorb high-frequency stray magnetic fields. The combination of the two significantly reduces capacitive coupling and eddy current losses between the windings. The thermosetting conductive adhesive forms a stable adhesive layer after curing at high temperature, ensuring that the shielding strip is tightly attached to the iron core and avoiding shielding failure due to vibration. This design can adapt to some scenarios that require measurement accuracy, reduce signal distortion of the current transformer in complex electromagnetic environments, and improve the fidelity of the output current waveform.

[0067] In a further embodiment, the relay uses an optically isolated switch.

[0068] By adopting the above technical solution, the optical isolating switch achieves electrical isolation through the principle of optocoupler, completely blocking the direct electrical connection between the primary and secondary sides, avoiding the risk of high voltage entering the low voltage measurement circuit. It has a fast response speed, long life, and is not affected by electromagnetic interference, making it suitable for the rapid switching requirements of transient fault current in power systems. In addition, the optical isolation characteristics can prevent poor contact caused by relay contact oxidation, even in humid or dusty environments.

[0069] In a further embodiment, the relay is provided with a heat sink, which is made of aluminum and has a fin.

[0070] By adopting the above technical solution, the aluminum heat sink utilizes its high thermal conductivity to quickly dissipate the Joule heat during relay operation, while the fin structure enhances the air convection heat dissipation efficiency by increasing the surface area, preventing the relay from malfunctioning or having its lifespan shortened due to excessive temperature rise. This design is particularly suitable for situations where the internal space of the compact current transformer housing 1 is limited. Passive heat dissipation can meet the temperature control requirements under long-term high-current conditions without the need for additional fans or cooling devices, thus reducing energy consumption and maintenance costs.

[0071] In a further embodiment, the right signal output terminal 32 is a protective ground, and the grounding resistance is ≤4Ω.

[0072] By adopting the above technical solution, the low-impedance grounding output terminal provides a reliable equipotential reference point for the secondary side, which can quickly discharge transient overvoltages generated by lightning strikes or short-circuit faults, avoid equipment insulation breakdown, and strictly control the grounding resistance within 4Ω to ensure that the fault current is sufficient to trigger the protection device to operate. In addition, this design can effectively suppress common-mode interference and improve the noise immunity of the measurement signal. Especially in the case of frequency converters or electric arc furnaces with severe harmonic pollution, it can ensure the accuracy of current sampling and the response accuracy of the protection circuit.

[0073] In the embodiments disclosed in this utility model, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; "linking" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments disclosed in this utility model according to the specific circumstances.

[0074] This specific embodiment is merely an explanation of the present utility model and is not intended to limit the present utility model. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the claims of the present utility model, they are protected by patent law.

Claims

1. An adjustable multi-ratio current transformer suitable for power systems, comprising a housing and two signal output terminals (3) disposed on the housing, a primary winding (1) and a secondary winding (2), characterized in that: Both the primary winding (1) and the secondary winding (2) are located inside the outer casing; The two signal output terminals (3) are named the left signal output terminal (31) and the right signal output terminal (32) respectively; It has at least two secondary windings (2), namely a first secondary winding (21) and a second secondary winding (22); The number of turns of the first secondary winding (21) is greater than the number of turns of the second secondary winding (22); The first secondary winding (21) includes a first left tap and a first right tap; The second secondary winding (22) includes a second left tap and a second right tap; It also includes a circuit board disposed inside the housing; The circuit board is equipped with a first relay (4), a second relay (5), and a third relay (6); The relay has two control terminals, one wiring terminal, and one controlled terminal; The first left tap is connected to the left signal output terminal (31); The first right tap is connected to the terminal of the first relay (4), and the controlled terminal of the first relay (4) is connected to the right signal output terminal (32); The second left tap is connected to the terminal of the second relay (5), and the controlled terminal of the second relay (5) is connected to the left signal output terminal (31); The second right tap is connected to the terminal of the third relay (6), and the controlled terminal of the third relay (6) is connected to the right signal output terminal (32).

2. The adjustable multi-ratio current transformer for power systems according to claim 1, characterized in that: It has at least two segments of the primary winding (1); The number of turns in the primary winding (1) of both sections is the same; The two sections of the primary winding (1) pass through the core of the current transformer respectively; The circuit board is also equipped with a first electronic control switch (7), a second electronic control switch (8) and a third electronic control switch (9); The electric control switch has two control terminals, one wiring terminal, and one controlled terminal; The two primary windings (1) are named the upper primary winding (11) and the lower primary winding (12) respectively; The input terminal of the previous winding (11) is connected to the terminal of the first electronic control switch (7), and the controlled terminal of the first electronic control switch (7) is connected to the output terminal of the next winding (12). The input terminal of the previous winding (11) is connected to the terminal of the second electronic control switch (8), and the controlled terminal of the second electronic control switch (8) is connected to the input terminal of the next winding (12). The controlled end of the previous winding (11) is connected to the terminal of the third electronic control switch (9), and the controlled end of the third electronic control switch (9) is connected to the output terminal of the next winding (12).

3. The adjustable multi-ratio current transformer for power systems according to claim 2, characterized in that: The iron core is wrapped with a shielding strip to prevent secondary winding coupling interference; The shielding strip includes insulating capacitor paper and semiconductor crepe paper; The surface of the semiconductor crepe paper is bonded with insulating capacitor paper, and thermosetting conductive adhesive is disposed below the insulating capacitor paper. The shielding strip is bonded and fixed by the thermosetting conductive adhesive.

4. The adjustable multi-ratio current transformer for power systems according to claim 1, characterized in that: The relay is an optically isolated switch.

5. The adjustable multi-ratio current transformer for power systems according to claim 4, characterized in that: The relay is equipped with a heat sink, which is made of aluminum. The heat sink has a fin.

6. The adjustable multi-ratio current transformer for power systems according to claim 1, characterized in that: The right signal output terminal (32) is for protective grounding, and the grounding resistance is ≤4Ω.

Images