Mutual inductor with protection assembly

Abstract

The invention provides a mutual inductor with a protection assembly, and relates to the technical field of mutual inductors. The mutual inductor with the protection assembly comprises the protection assembly, a primary winding, a secondary winding and a body of a wiring terminal, two terminals of a second wiring terminal are externally connected with an external load, a voltage sensor in the protection assembly is connected with a short-circuit protection branch containing a relay and a current-limiting resistor in parallel, and a current sensor is connected between one terminal and a parallel circuit in series. The rectifier bridge takes electricity from a special joint (the number of turns is 5%-10% of the total number of turns) of the secondary winding, the electricity is supplied to each element after being processed, and the controller receives a sensor signal and controls the relay; during normal work, secondary current flows, the sensor detects normal signals, the relay is disconnected, when an external load is open, current drops suddenly, voltage rises suddenly, the controller enables the relay to be closed, the short-circuit branch conducts clamping high voltage, and normal recovery is achieved after faults are removed. The device can monitor a secondary circuit in real time, quickly respond to open-circuit faults and avoid high-voltage hazards, and the power supply is reliable and high in stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mutual inductors, in particular to a mutual inductor with a protection assembly. BACKGROUND

[0002] A mutual inductor is an important device in a power system for transforming voltage or current, which converts high voltage or large current into low voltage or small current in proportion through electromagnetic induction principle, so as to realize functions such as power metering, relay protection and monitoring control, and is mainly divided into two types of current transformers and voltage transformers. Among them, the primary winding of the current transformer is connected in series with the measured circuit, and the secondary winding is connected with external loads such as measuring instruments and protection devices, which can effectively isolate the high-voltage circuit and the low-voltage control circuit, and protect the safety of equipment and personnel.

[0003] In the actual operation of the current transformer, if the two terminals connected with the secondary winding are not in good contact due to loose connection, oxidation and corrosion or vibration and falling off, etc., the external load circuit is easy to be opened. At this time, the magnetic motive force of the primary winding cannot be offset by the current magnetic motive force of the secondary winding, and the core will be saturated due to the magnetic saturation, and a high voltage of several thousand volts will be induced at both ends of the secondary winding. Not only can it break through the winding insulation layer and cause equipment failure, but also can cause electric shock risk to the nearby operators, and the electric arc generated by the high voltage can damage the surrounding components, affecting the stable operation of the power system.

[0004] Therefore, we have developed a new mutual inductor with a protection assembly. SUMMARY

[0005] (I) Technical problems solved In view of the shortcomings of the prior art, the present application provides a mutual inductor with a protection assembly, which solves the problem of high voltage generated by core magnetic saturation when the secondary winding of the current transformer is caused by poor contact of the connection terminal and other reasons. The external load circuit is opened, and then the insulation breakdown of the equipment, the electric shock of the personnel and the damage of the surrounding components are caused.

[0006] (II) Technical solutions In order to achieve the above purpose, the present application is realized by the following technical solutions: a mutual inductor with a protection assembly, comprising a mutual inductor body, characterized in that: the mutual inductor body comprises a protection assembly, a primary winding, a secondary winding, a first connection terminal and a second connection terminal, the first connection terminal and the second connection terminal are electrically connected with the primary winding and the secondary winding respectively, the second connection terminal comprises S1 terminal and S2 terminal, and an external load is connected between the S1 terminal and the S2 terminal. The protection assembly comprises a voltage sensor, a short-circuit protection branch and a rectifier bridge, the voltage sensor and the short-circuit protection branch are in parallel connection, the total incoming line joint of the parallel circuit is connected between the S1 terminal and one connection point of the secondary winding, and the total outgoing line joint of the parallel circuit is connected between the S2 terminal and another connection point of the secondary winding. Preferably, a current sensor is connected in series between the S1 terminal and the total incoming line joint of the parallel circuit.

[0007] Preferably, the short-circuit protection branch comprises a relay and a current-limiting resistor connected in series.

[0008] Preferably, one input end of the rectifier bridge is connected between the S1 terminal and one connection point of the secondary winding, and another input end of the rectifier bridge is connected to a special joint of the secondary winding, the special joint is a part of the coil of the secondary winding, and the number of turns of the part of the coil is 5%-10% of the number of turns of the total coil of the secondary winding.

[0009] Preferably, a first filter capacitor is connected to an output end of the rectifier bridge, a voltage stabilizing chip is connected to an output end of the first filter capacitor, a second filter capacitor is connected to an output end of the voltage stabilizing chip, and the other output end of the rectifier bridge and the output end of the second filter capacitor are both grounded.

[0010] Preferably, the signal output ends of the current sensor, the voltage sensor and the relay are collectively connected to a controller.

[0011] Preferably, the output end of the voltage stabilizing chip is respectively connected to a positive power supply pin of the current sensor, a positive power supply pin of the voltage sensor, a positive power supply pin of the controller and a positive pin of the control coil of the relay, and the grounded output end of the rectifier bridge is respectively connected to a negative power supply pin of the current sensor, a negative power supply pin of the voltage sensor, a negative power supply pin of the controller and a negative pin of the control coil of the relay.

[0012] (Three) beneficial effects The present application provides a mutual inductor with a protection assembly, which has the following beneficial effects: 1. The mutual inductor with the protection assembly, by arranging the voltage sensor and the short-circuit protection branch in parallel at the output end of the secondary winding, in combination with the current sensor connected in series in the circuit, the current and voltage states of the secondary circuit can be monitored in real time, when the open circuit characteristics of "low current + high voltage" are detected, the controller can quickly trigger the relay to act, and the S1 terminal and the S2 terminal are short-circuited through the current-limiting resistor, thereby effectively clamping the high voltage and avoiding the risk of equipment insulation damage and electric shock.

[0013] 2. This instrument transformer with protective components draws power from a dedicated connector on the secondary winding via a rectifier bridge. After filtering and voltage regulation, it provides a stable power supply to all electronic components. The number of turns of the dedicated connector meets the power supply requirements without affecting the generation and detection of high voltage during open circuit, ensuring the continuous reliability of the protection function. At the same time, the unified power link and signal transmission design simplifies the circuit structure, improves the overall operational stability and anti-interference capability, and ensures the safe operation of the instrument transformer under complex working conditions. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a circuit diagram of the protective component during normal operation of the present invention; Figure 3 This is a circuit diagram of a protection component for an open circuit in the external load circuit of the secondary winding.

[0015] The components include: 1. Current transformer body; 2. First terminal; 3. Second terminal; 4. S1 terminal; 5. S2 terminal; 6. Protection component; 7. External load; 8. Voltage sensor; 9. Short-circuit protection branch; 10. Rectifier bridge; 11. Primary winding; 12. Secondary winding; 13. Current sensor; 14. Relay; 15. Current limiting resistor; 16. First filter capacitor; 17. Voltage regulator chip; 18. Second filter capacitor; 19. Controller; 20. Special connector. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Examples, such as Figure 1 - Figure 3 As shown, this embodiment of the invention provides a current transformer with a protection component, including a current transformer body 1. The current transformer body 1 includes a protection component 6, a primary winding 11, a secondary winding 12, a first terminal 2, and a second terminal 3. The first terminal 2 and the second terminal 3 are electrically connected to the primary winding 11 and the secondary winding 12, respectively. The second terminal 3 includes an S1 terminal 4 and an S2 terminal 5. An external load 7 is connected between the S1 terminal 4 and the S2 terminal 5. The first terminal 2 and the second terminal 3 respectively connect the primary winding 11 to the high-voltage side circuit and the secondary winding 12 to the low-voltage side external load 7, forming the basic current transformation circuit of the current transformer. This ensures that the large current on the primary side is converted into a small current on the secondary side according to the transformation ratio for use by the external load 7 (such as a protection device or an ammeter).

[0018] The protection assembly 6 comprises a voltage sensor 8, a short-circuit protection branch 9, and a rectifier bridge 10. The voltage sensor 8 and the short-circuit protection branch 9 are in parallel connection, the total incoming line connection point of the parallel circuit is connected between the S1 terminal 4 and one connection point of the secondary winding 12, and the total outgoing line connection point of the parallel circuit is connected between the S2 terminal 5 and the other connection point of the secondary winding 12. The voltage sensor 8 is connected in parallel with the output end of the secondary winding 12, for monitoring the voltage change of the secondary circuit in real time (normal load voltage, and high voltage when open circuit); Specifically, the current sensor 13 is connected in series between the S1 terminal 4 and the total incoming line connection point of the parallel circuit, and the current sensor 13 is connected in series between the secondary winding 12 and the S1 terminal 4, so as to directly detect the secondary current flowing through the external load 7, and provide a key signal for judging whether the circuit is open (the current is suddenly reduced to 0), and the series connection ensures the accuracy of current detection; The short-circuit protection branch 9 comprises a relay 14 and a current-limiting resistor 15 connected in series. The relay 14 is used as a switching element, which is normally open to not affect the secondary circuit, and is closed to realize S1-S2 short circuit when a fault occurs. The current-limiting resistor 15 connected in series can limit the short-circuit current (e.g., controlled within 1.2 times of the rated current), so as to avoid damage to the secondary winding 12 due to long-term short circuit overheating, and quickly clamp the open circuit high voltage; One input end of the rectifier bridge 10 is connected between the S1 terminal 4 and one connection point of the secondary winding 12, and the other input end of the rectifier bridge 10 is connected to a special joint 20 of the secondary winding 12. The special joint 20 is a part of the coil drawn from the total coil of the secondary winding 12, and the number of turns of the part of the coil is 5%-10% of the total number of turns of the secondary winding 12. The rectifier bridge 10 takes power through the special joint 20 (part of the coil of the secondary winding), acquires low-voltage alternating current by electromagnetic induction principle (fewer turns result in lower voltage), meets the power supply requirement, and because the number of turns is much smaller than that of the main winding (5%-10%), the magnetic motive force generated thereby can be ignored, so as not to affect the magnetic saturation high voltage generated when the secondary circuit is open, and to ensure that the voltage sensor 8 can normally detect a fault; One output terminal of the rectifier bridge 10 is electrically connected to a first filter capacitor 16. The output terminal of the first filter capacitor 16 is electrically connected to a voltage regulator chip 17. The output terminal of the voltage regulator chip 17 is electrically connected to a second filter capacitor 18. The other output terminal of the rectifier bridge 10 and the output terminal of the second filter capacitor 18 are both grounded. The rectifier bridge 10 converts AC power into pulsating DC power. The first filter capacitor 16 filters out low-frequency ripple, the voltage regulator chip 17 stabilizes the voltage into DC, and the second filter capacitor 18 further filters out high-frequency interference. Finally, a stable low-voltage DC power supply is output to power subsequent electronic components (sensors, controllers, etc.). The grounding design ensures that the circuit potential reference is consistent. The signal output terminals of current sensor 13, voltage sensor 8 and relay 14 are electrically connected to controller 19. Controller 19 serves as the core judgment unit, receiving inputs from current sensor 13 (current signal) and voltage sensor 8 (voltage signal). It determines the open circuit fault of the secondary circuit through the combination logic of "low current + high voltage" and outputs control signals to relay 14 to realize the automatic control of protection action. The output terminal of the voltage regulator chip 17 is electrically connected to the positive power supply pin of the current sensor 13, the positive power supply pin of the voltage sensor 8, the positive power supply pin of the controller 19, and the positive control coil pin of the relay 14, respectively. The ground output terminal of the rectifier bridge 10 is electrically connected to the negative power supply pin of the current sensor 13, the negative power supply pin of the voltage sensor 8, the negative power supply pin of the controller 19, and the negative control coil pin of the relay 14, respectively. All electronic components are powered through a unified power supply link, ensuring that the operating voltage of each component is matched, avoiding signal interference or component damage caused by inconsistent power supply, while simplifying circuit wiring and improving reliability.

[0019] Working Principle: Under normal operating conditions, the primary winding 11 generates a rated current in the secondary winding 12 with a fixed transformation ratio to the primary side through electromagnetic induction. This current flows out from one end of the secondary winding 12, passing sequentially through the current sensor 13, the main input terminal of the parallel circuit, terminal S1 4, the external load 7, terminal S2 5, and the main output terminal of the parallel circuit, finally returning to the other end of the secondary winding 12, forming a complete current path. At this time, the external load 7 can normally obtain the secondary current to achieve measurement or protection functions. During this process, the current sensor 13 is connected in series in the circuit, which can detect the current value in real time and transmit the signal to the controller 19. Since the circuit is normally conducting, the detected current is the rated value. The voltage sensor 8 is connected in parallel between terminal S1 4 and terminal S2 5. Due to the certain impedance of the external load 7, the voltage across it is maintained within the normal range, and this voltage signal is also transmitted to the controller 19. Meanwhile, the two input terminals of the rectifier bridge 10 are respectively connected between the connection point of the S1 terminal 4 and the secondary winding 12 and the dedicated connector 20 of the secondary winding 12. The dedicated connector 20 is taken from a portion of the coil with 5%-10% of the total turns in the secondary winding 12. The AC voltage induced by it is rectified by the rectifier bridge 10 into a pulsating DC voltage, then filtered by the first filter capacitor 16, and regulated by the voltage regulator chip 17 to output a stable DC voltage. Finally, the second filter capacitor 18 further filters out high-frequency interference, providing working power to the control coils of the current sensor 13, voltage sensor 8, controller 19, and relay 14. At this time, the controller 19 receives normal current and voltage signals, determines that the circuit is fault-free, the relay 14 remains in the open state, and the short-circuit protection branch 9 does not participate in the circuit operation. When an open-circuit fault occurs in the external load 7 between terminals S1 4 and S2 5, the output current of the secondary winding 12 loses its flow path, and the current value detected by the current sensor 13 drops sharply to near zero. This abnormal signal is transmitted to the controller 19. Due to the open circuit in the secondary circuit, the magnetomotive force generated by the primary winding 11 cannot be canceled by the current magnetomotive force of the secondary winding 12, resulting in magnetic saturation of the iron core. A high voltage of several thousand volts is induced across the secondary winding 12, and the voltage sensor 8 detects this high-voltage signal and transmits it to the controller 19. At this time, the rectifier bridge 10 can still obtain the induced voltage from the secondary winding 12 through the dedicated connector 20, process it, and continue to power the various electronic components, ensuring that the monitoring and control functions are not affected. Upon receiving the combined signal of "low current + high voltage", the controller 19 immediately determines that an open circuit fault has occurred in the secondary circuit. It then outputs a control signal to the control coil of the relay 14, causing the contacts of the relay 14 to close and the short-circuit protection branch 9 to be activated. The current flows from terminal S1 4 through the relay 14 and the current-limiting resistor 15 to terminal S2 5. The current-limiting resistor 15 can limit the short-circuit current within a safe range to prevent damage to the secondary winding 12 due to overcurrent. At the same time, it quickly clamps the high voltage between terminal S1 4 and terminal S2 5 to a low level to prevent the high voltage from harming the equipment insulation and personnel safety. When the open-circuit fault of external load 7 is cleared and the circuit is reclosed, the current in the secondary winding 12 returns to its rated value. The current sensor 13 detects a normal current signal, and the voltage across the secondary winding 12 drops to the normal range due to the load connection. The voltage sensor 8 detects a normal voltage signal and transmits it to the controller 19. Based on the restored signal, the controller 19 determines that the fault has been cleared, stops outputting control signals to the relay 14, the contacts of the relay 14 open, the short-circuit protection branch 9 stops working, and the entire transformer returns to normal operation, continuously providing a stable secondary current to the external load 7.

[0020] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A current transformer with protective components, comprising a current transformer body (1), characterized in that: The transformer body (1) includes a protection component (6), a primary winding (11), a secondary winding (12), a first terminal (2) and a second terminal (3). The first terminal (2) and the second terminal (3) are electrically connected to the primary winding (11) and the secondary winding (12) respectively. The second terminal (3) includes an S1 terminal (4) and an S2 terminal (5). An external load (7) is connected between the S1 terminal (4) and the S2 terminal (5). The protection component (6) includes a voltage sensor (8), a short-circuit protection branch (9), and a rectifier bridge (10). The voltage sensor (8) and the short-circuit protection branch (9) are connected in parallel. The main input terminal of the parallel circuit is connected between the S1 terminal (4) and one terminal of the secondary winding (12), and the main output terminal of the parallel circuit is connected between the S2 terminal (5) and another terminal of the secondary winding (12).

2. A current transformer with a protective component according to claim 1, characterized in that, A current sensor (13) is connected in series between the S1 terminal (4) and the main input contact of the parallel circuit.

3. A current transformer with a protective component according to claim 2, characterized in that, The short-circuit protection branch (9) includes relays (14) and current-limiting resistors (15) connected in series.

4. A current transformer with a protective component according to claim 3, characterized in that, One input terminal of the rectifier bridge (10) is connected between the S1 terminal (4) and a contact point of the secondary winding (12). The other input terminal of the rectifier bridge (10) is connected to a dedicated connector (20) of the secondary winding (12). The dedicated connector (20) is a portion of the coil drawn from the total coil of the secondary winding (12). The number of turns of this portion of the coil is 5%-10% of the total number of turns of the secondary winding (12).

5. A current transformer with a protective component according to claim 4, characterized in that, One output terminal of the rectifier bridge (10) is electrically connected to a first filter capacitor (16), the output terminal of the first filter capacitor (16) is electrically connected to a voltage regulator chip (17), the output terminal of the voltage regulator chip (17) is electrically connected to a second filter capacitor (18), and the other output terminal of the rectifier bridge (10) and the output terminal of the second filter capacitor (18) are both grounded.

6. A current transformer with a protective component according to claim 5, characterized in that, The signal output terminals of the current sensor (13), voltage sensor (8) and relay (14) are all electrically connected to the controller (19).

7. A current transformer with a protective component according to claim 6, characterized in that, The output terminal of the voltage regulator chip (17) is electrically connected to the positive power supply pin of the current sensor (13), the positive power supply pin of the voltage sensor (8), the positive power supply pin of the controller (19), and the positive control coil pin of the relay (14), respectively. The ground output terminal of the rectifier bridge (10) is electrically connected to the negative power supply pin of the current sensor (13), the negative power supply pin of the voltage sensor (8), the negative power supply pin of the controller (19), and the negative control coil pin of the relay (14), respectively.

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