CT (Computed Tomography) self-power-taking protection device

Abstract

The utility model discloses a CT self-power-taking protection device, and belongs to the technical field of power relay protection. The device comprises a fault current detection loop, a CT power taking loop and a self-protection module. The fault current detection loop is composed of a phase current detection device, a zero-sequence current synthesis detection device and an over-current fuse device and is used for detecting an inter-phase and zero-sequence over-current fault, and the over-current fuse device is fused when the fault occurs; the CT power taking loop is provided with a rectifier bridge, a CT opening voltage storage capacitor, a high-voltage trigger conduction diode and an output loop, CT opening energy can be obtained through the voltage storage capacitor and the diode, and the output loop drives a trip coil to trip off a circuit breaker to cut off a fault loop; the self-protection module comprises an overvoltage protection loop and an overcurrent protection loop, is composed of a current-limiting resistor, and can clamp and discharge abnormal high voltage and overcurrent in the loop. The device adopts a full-analog circuit design, has the advantages of quick response, high reliability, strong interference resistance and the like, can quickly and accurately act in a complex electromagnetic environment, and effectively guarantees the safety of a power system.

Description

Technical Field

[0001] This application belongs to the field of power relay protection technology, and in particular relates to a CT self-power supply protection device. Background Technology

[0002] In power systems, ensuring the safe and stable operation of power lines is crucial, as it directly relates to the reliability of power supply and the safety of electricity consumption for users. Protective devices play an indispensable role in enabling timely protective measures to be taken when line faults occur, preventing further escalation of the fault. Among these, the CT (current transformer) self-powered protection device, as a common power protection equipment, is widely used.

[0003] Currently, most existing traditional CT self-powered protection devices use MCUs (Microcontroller Units) for logic judgment and control. As a core of digital circuit processing, the MCU possesses powerful computing and logic processing capabilities, enabling the protection device to achieve more comprehensive and powerful functions. The MCU analyzes and processes the collected electrical parameters such as current, determines whether a line fault has occurred based on preset protection logic, and uses relays to control the opening and closing coils, thereby quickly cutting off the circuit when a fault occurs, thus protecting the power system.

[0004] However, traditional CT self-power-supply protection devices that use digital circuits such as MCUs for logic judgment and control have some problems that cannot be ignored. Although digital circuits have many advantages in functional implementation, they also have a certain probability of reliability risks. Since MCUs rely on programs to execute various logic judgments and control tasks, if the program has a bug (program vulnerability or error) or an abnormal situation such as a system crash, the protection device will not function properly.

[0005] In power systems, faults are sudden and unpredictable. Protection devices must respond accurately and promptly to disconnect the faulty circuit the instant a fault occurs. However, when traditional CT self-power-supply protection devices fail due to programming issues, the fault cannot be disconnected in time, and the fault current will persist. This not only leads to serious damage to power equipment, increasing maintenance costs and power outage time, but may also trigger more serious power accidents, such as fires and explosions, causing huge property losses and even threatening personal safety. Utility Model Content

[0006] The purpose of this application is to provide a CT self-power supply protection device, which aims to solve the problems existing in the prior art. The device includes a current detection circuit and a trip drive circuit, and through the coordinated work of the various components, it achieves effective protection of the power system.

[0007] To achieve the above objectives, this application provides a CT self-power supply protection device, comprising:

[0008] Fault current detection circuit, CT power supply circuit and self-protection module;

[0009] The fault current detection circuit includes a phase current detection section, a zero-sequence current synthesis detection section, and an overcurrent fuse. The phase current detection section is based on a three-phase circuit structure, which consists of a first phase line L1, a second phase line L2, and a third phase line L3. A first fuse FuseA is connected to the first phase line L1, a second fuse FuseB is connected to the second phase line L2, and a third fuse FuseC is connected to the third phase line L3. The first fuse FuseA, the second fuse FuseB, and the third fuse FuseC are used to blow when an overcurrent occurs in the circuit to protect the fault current detection circuit from damage by excessive current. The zero-sequence current synthesis detection section is implemented by connecting a fourth fuse FuseE in series at the neutral point of the three phase lines of the three-phase circuit structure. The fourth fuse FuseE is used to detect the zero-sequence current and prevent grounding faults from occurring.

[0010] The CT power supply circuit includes a rectifier bridge, a CT opening voltage storage capacitor, a high-voltage trigger diode, and an output circuit. The CT opening voltage storage capacitor stores the voltage energy generated by the CT opening. The high-voltage trigger diode conducts in the CT power supply circuit when the circuit voltage reaches the trigger voltage, providing a path for the CT opening voltage storage capacitor to release the voltage. The output circuit outputs the voltage released by the CT opening voltage storage capacitor. The output circuit of the CT power supply circuit is connected to the trip coil. When energized, the trip coil generates electromagnetic force to achieve the trip protection function and disconnect the circuit.

[0011] The self-protection module includes overvoltage and overcurrent protection circuits, which consist of a current-limiting resistor connected in series with the trip coil and the high-voltage trigger diode. It is used to ensure that abnormal high voltage and overcurrent generated in the device circuit are clamped and discharged.

[0012] The fault current detection circuit, CT power supply circuit, and self-protection module work together. When a phase-to-phase overcurrent or zero-sequence overcurrent fault occurs, the fault current detection circuit detects the fault current and the overcurrent fuse blows. The CT power supply circuit obtains CT opening energy through the CT opening voltage storage capacitor and the high-voltage trigger conduction diode, and drives the trip coil to trip the circuit breaker through the output circuit, cutting off the fault circuit and realizing fault protection.

[0013] The method described in the embodiments of this application may also have the following additional technical features:

[0014] Furthermore, the phase current detection section also includes current transformers, which are respectively installed on the first phase line L1, the second phase line L2 and the third phase line L3, to convert the large current in each phase line into a small current proportionally, while achieving electrical isolation.

[0015] Furthermore, the fault current detection circuit also includes a grounding connection GND for detecting ground fault current.

[0016] Furthermore, the device adopts a fully analog circuit design, without any digital control components, and achieves fault detection, CT power supply and self-protection functions solely through the electrical characteristics between analog circuit components.

[0017] The CT self-power supply protection device provided in this application has the following advantages compared with the prior art:

[0018] The fault current detection circuit of this application embodiment can quickly detect phase-to-phase overcurrent or zero-sequence overcurrent faults. Once the fault current is detected, the overcurrent fuse blows in time to cut off the fault current path and prevent the fault from expanding further. At the same time, the CT power supply circuit quickly obtains energy to drive the trip coil to trip the circuit breaker and quickly cut off the fault circuit, realizing fast and accurate fault protection and effectively reducing the damage caused by the fault to the power system.

[0019] The current transformer in the phase current detection section of this application embodiment can convert the large current in the first phase line L1, the second phase line L2 and the third phase line L3 into small currents proportionally. This not only facilitates subsequent circuit processing, but also achieves electrical isolation, improves the safety and reliability of the device, and avoids damage to subsequent circuit components caused by large currents.

[0020] In the fault current detection circuit of this application embodiment, the grounding connection GND can introduce the leakage current to the ground when leakage current occurs, preventing the leakage current from accumulating in the circuit, avoiding potential safety hazards and equipment failures caused by leakage current, and ensuring the safe and stable operation of the device and the power system.

[0021] The device in this application adopts a fully analog circuit design, without any digital control components. It achieves fault detection, CT power supply, and self-protection functions solely through the electrical characteristics between analog circuit components. This design approach enables the device to respond quickly and reliably, operate rapidly and accurately in complex electromagnetic environments, and remain unaffected by potential interference from digital circuits, thus ensuring the safe operation of the power system.

[0022] The overvoltage and overcurrent protection circuit in the self-protection module of this application embodiment can clamp and release abnormal high voltage and overcurrent generated in the device circuit, ensuring that the device can operate normally under various abnormal conditions and will not be damaged due to internal overvoltage and overcurrent, thus extending the service life of the device and reducing maintenance costs.

[0023] This application embodiment converts AC power to DC power through a rectifier bridge, providing a stable DC power supply for the trip coil. At the same time, it can also protect the trip coil from the influence of reverse voltage, ensuring that the trip coil can stably generate electromagnetic force under normal working conditions, and realize reliable trip protection function. Attached Figure Description

[0024] Figure 1 A structural block diagram of the fault current detection circuit of the CT self-power supply protection device according to an embodiment of this application is shown;

[0025] Figure 2 The diagram shows a structural block diagram of the CT power supply circuit and self-protection module of the CT self-power supply protection device according to an embodiment of this application. Detailed Implementation

[0026] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0027] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0028] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0029] like Figure 1As shown in the figure, this application embodiment provides a fault current detection circuit for a CT self-power supply protection device, including:

[0030] In the phase current detection section, this embodiment constructs a three-phase circuit structure consisting of a first phase line L1, a second phase line L2, and a third phase line L3. A first fuse FuseA is connected in series on the first phase line L1, a second fuse FuseB is connected in series on the second phase line L2, and a third fuse FuseC is connected in series on the third phase line L3. These fuses act as overcurrent protection devices, melting when an overcurrent occurs in the circuit to protect the fault current detection circuit from damage by excessive current.

[0031] This embodiment of the application installs current transformers on the first phase line L1, the second phase line L2, and the third phase line L3, respectively. The current transformers proportionally convert the large currents in each phase line into smaller currents, achieving electrical isolation and facilitating current detection and processing by subsequent circuits.

[0032] This embodiment of the application connects a fourth fuse, FuseE, in series at the neutral point of the three-phase lines in a three-phase circuit structure. The fourth fuse, FuseE, is used to detect the zero-sequence current. When a ground fault occurs, the zero-sequence current will become abnormal. By detecting the state of the fourth fuse, FuseE, it can be determined whether a ground fault exists, thereby preventing the ground fault from occurring.

[0033] This application embodiment incorporates a grounding connection GND in the fault current detection circuit. When leakage current occurs in the circuit, it is introduced to the ground through the grounding connection GND, preventing the leakage current from accumulating in the circuit and thus preventing potential safety hazards and equipment failures caused by leakage current.

[0034] like Figure 2 As shown, this application embodiment provides a CT power supply circuit and self-protection module for a CT self-power supply protection device, including:

[0035] The CT opening voltage storage capacitor, in this embodiment, uses a CT opening voltage storage capacitor of appropriate capacity to store the voltage energy generated by the CT opening. During normal operation, the CT opening generates a certain voltage, and the storage capacitor stores this voltage energy.

[0036] This embodiment also uses a high-voltage trigger diode with a suitable trigger voltage. When the voltage in the CT power supply circuit reaches the trigger voltage, the high-voltage trigger diode turns on, providing a path for the CT opening voltage storage capacitor to release voltage.

[0037] Furthermore, the CT power supply circuit in this embodiment also includes an output circuit, which outputs the voltage released by the CT opening voltage storage capacitor. The output circuit is connected to a trip coil, which generates electromagnetic force when energized, thereby achieving the trip protection function and cutting off the circuit.

[0038] The CT power supply circuit in this embodiment also includes a rectifier bridge for converting alternating current (AC) to direct current (DC). In power systems, the power supply is typically AC, while the trip coil requires a stable DC power supply to operate normally. The rectifier bridge consists of four diodes, which convert the input AC into pulsating DC, and then smooth it into stable DC through a filter circuit (in this embodiment, the capacitor also plays a filtering role to some extent), providing a stable DC power supply for the trip coil. Simultaneously, the rectifier bridge also protects the trip coil from reverse voltage, ensuring that the trip coil can stably generate electromagnetic force under normal operating conditions, achieving reliable trip protection.

[0039] The self-protection module in this embodiment includes an overvoltage protection circuit and an overcurrent protection circuit, which is composed of a current-limiting resistor connected in series with a trip coil and a high-voltage trigger diode. By designing the overvoltage protection circuit, suitable overvoltage detection and protection components (such as Zener diodes, thyristors, etc.) are adopted. When the voltage in the device circuit exceeds the set safety threshold, the overvoltage protection circuit is activated to clamp the abnormal high voltage and limit the voltage within a safe range, preventing overvoltage from damaging the device components.

[0040] By designing an overcurrent protection circuit, current sensing elements (such as current transformers, resistors, etc.) and overcurrent protection elements (such as fuses, current-limiting resistors, etc.) are used. When the current in the circuit exceeds the set safety threshold, the overcurrent protection circuit is activated to discharge the overcurrent, reduce the current magnitude, and protect the circuit from damage caused by excessive current.

[0041] A current-limiting resistor connected in series with the trip coil and the high-voltage trigger diode is used to limit the current in the trip drive circuit. Excessive current in the circuit may damage components such as the trip coil and the high-voltage trigger diode. The current-limiting resistor limits the current through its own resistance, preventing excessive current and ensuring the stable operation of the trip drive circuit.

[0042] In the CT self-power supply protection device, the fault current detection circuit, the CT power supply circuit, and the self-protection module are three core components. They are closely connected and work together to ensure that the device can respond to faults accurately and quickly and protect the safety of the power system.

[0043] Specifically, the fault current detection circuit is mainly responsible for detecting fault currents in the circuit, including phase-to-phase overcurrent and zero-sequence overcurrent. When a fault current is detected, although it does not directly send a signal to the CT power supply circuit, the presence of the fault current is one of the prerequisites for triggering the CT power supply circuit to operate (in some design logics, the detection of fault current may indirectly affect the start-up or adjustment of the CT power supply circuit). In reality, the CT power supply circuit may continuously draw energy from the CT, but the detection result of the fault current will determine whether the energy output from the CT power supply circuit is subsequently needed to drive the trip coil. When the fault current detection circuit detects a fault current, although it does not directly control the operation of the self-protection module, the abnormality of the fault current may trigger the overcurrent protection section in the self-protection module to protect the circuit and prevent the fault from escalating. The self-protection module may monitor the current state in the fault current detection circuit, and when the current exceeds a set threshold, it will activate overcurrent protection measures.

[0044] The CT power take-off circuit obtains energy from the CT and stores it in a voltage storage capacitor. When the fault current detection circuit detects a fault, the CT power take-off circuit releases the energy from the voltage storage capacitor through its output circuit, driving the trip coil to trip the circuit breaker and disconnect the faulty circuit. This coordinated operation ensures that the device can act quickly after detecting a fault, preventing further damage to the power system. The CT power take-off circuit itself has energy storage and discharge functions, but it is usually designed to be relatively independent of the self-protection module. However, the self-protection module may monitor the voltage and current status in the CT power take-off circuit to ensure that it operates within normal ranges. When abnormal high voltage or overcurrent occurs in the CT power take-off circuit, the self-protection module will activate corresponding protection measures, such as clamping or bleeding, to protect the CT power take-off circuit and the entire device from damage.

[0045] The overcurrent protection section of the self-protection module monitors the current status in the fault current detection circuit. When the current exceeds a set threshold, protective measures are taken, such as disconnecting part of the circuit or reducing the current, to prevent the fault current from damaging the detection circuit. As mentioned earlier, the self-protection module monitors the voltage and current status in the CT power supply circuit to ensure it operates within normal ranges. When an abnormality occurs, protective measures are activated to protect the CT power supply circuit and the entire device. As the "safety guardian" of the device, the self-protection module not only protects individual modules from damage but also coordinates the operation of the entire system, ensuring rapid and accurate action in the event of a fault, thus safeguarding the power system's safety.

[0046] When a phase-to-phase overcurrent or zero-sequence overcurrent fault occurs in the power system, the phase current detection section and the zero-sequence current synthesis detection section in the fault current detection circuit detect the fault current respectively. The phase current detection section detects the current of each phase line through a current transformer, while the zero-sequence current synthesis detection section detects the zero-sequence current through the fourth fuse, FuseE. Once a fault current is detected, the first fuse, FuseA, the second fuse, the third fuse, FuseC, or the fourth fuse, FuseE, will blow according to the current magnitude, cutting off the fault current path. The CT opening voltage storage capacitor in the CT power take-off circuit continuously stores the voltage energy generated by the CT opening. When the fault current detection circuit detects a fault, the voltage in the CT power take-off circuit reaches the trigger voltage of the high-voltage trigger diode, the diode conducts, and the storage capacitor releases the voltage. The released voltage drives the trip coil through the output circuit, the trip coil is energized to generate electromagnetic force, causing the circuit breaker to trip, cutting off the fault circuit, and realizing fault protection. During the operation of the device, the self-protection module monitors the voltage and current status in the circuit in real time. When abnormal high voltage or overcurrent occurs, the overvoltage protection circuit and the overcurrent protection circuit are activated respectively to clamp the abnormal high voltage and release the overcurrent, ensuring that the device can operate normally under various abnormal conditions and will not be damaged due to internal overvoltage or overcurrent.

[0047] The CT self-power-supply protection device in this application embodiment, through the coordinated operation of the fault current detection circuit and the CT power-supply circuit, can quickly detect faults and drive the trip coil to trip the circuit breaker, achieving fast and accurate fault protection and effectively reducing the damage caused by faults to the power system. The use of a current transformer enables the conversion from high current to low current and electrical isolation, improving the safety and reliability of the device. The grounding connection GND can promptly introduce leakage current to the ground, ensuring the safe and stable operation of the device and the power system. The fully analog circuit design makes the device have a fast response speed and high reliability, enabling it to operate quickly and accurately in complex electromagnetic environments, unaffected by digital circuit interference. The overvoltage and overcurrent protection circuits in the self-protection module ensure the device operates normally under various abnormal conditions, extending the device's service life and reducing maintenance costs.

[0048] In summary, in the CT self-powered protection device, the connection between the fault current detection circuit, the CT power supply circuit, and the self-protection module is close and coordinated. The fault current detection circuit is responsible for detecting the fault current, the CT power supply circuit is responsible for obtaining energy from the CT and driving the trip coil, and the self-protection module is responsible for monitoring and protecting the entire device from damage caused by abnormal high voltage and overcurrent. These three parts cooperate with each other to form an efficient and reliable power system protection device.

[0049] It should be noted that, in this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0050] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A CT self-power supply protection device, characterized in that, The device includes: Fault current detection circuit, CT power supply circuit and self-protection module; The fault current detection circuit includes a phase current detection section, a zero-sequence current synthesis detection section, and an overcurrent fuse. The phase current detection section is based on a three-phase circuit structure, which consists of a first phase line L1, a second phase line L2, and a third phase line L3. A first fuse FuseA is connected to the first phase line L1, a second fuse FuseB is connected to the second phase line L2, and a third fuse FuseC is connected to the third phase line L3. The first fuse FuseA, the second fuse FuseB, and the third fuse FuseC are used to blow when an overcurrent occurs in the circuit, thereby protecting the fault current detection circuit from damage by excessive current. The zero-sequence current synthesis detection section is implemented by connecting a fourth fuse FuseE in series at the neutral point of the three phase lines of the three-phase circuit structure. The fourth fuse FuseE is used to detect the zero-sequence current and prevent grounding faults from occurring. The CT power supply circuit includes a rectifier bridge, a CT opening voltage storage capacitor, a high-voltage trigger diode, and an output circuit. The CT opening voltage storage capacitor stores the voltage energy generated by the CT opening. The high-voltage trigger diode conducts in the CT power supply circuit when the circuit voltage reaches the trigger voltage, providing a path for the CT opening voltage storage capacitor to release the voltage. The output circuit outputs the voltage released by the CT opening voltage storage capacitor. The output circuit of the CT power supply circuit is connected to a trip coil, which generates electromagnetic force when energized to achieve the trip protection function and disconnect the circuit. The rectifier bridge converts AC power to DC power, providing a stable DC power supply to the trip coil and protecting it from reverse voltage. The self-protection module includes overvoltage and overcurrent protection circuits, which are composed of a current-limiting resistor connected in series with the trip coil and the high-voltage trigger diode, and are used to ensure that abnormal high voltage and overcurrent generated in the device circuit are clamped and discharged. The fault current detection circuit, CT power supply circuit, and self-protection module work together. When a phase-to-phase overcurrent or zero-sequence overcurrent fault occurs, the fault current detection circuit detects the fault current and the overcurrent fuse blows. The CT power supply circuit obtains CT opening energy through the CT opening voltage storage capacitor and the high-voltage trigger conduction diode, and drives the trip coil to trip the circuit breaker through the output circuit, cutting off the fault circuit and realizing fault protection.

2. The CT self-power supply protection device as described in claim 1, characterized in that, The phase current detection section also includes current transformers, which are respectively installed on the first phase line L1, the second phase line L2 and the third phase line L3, to convert the large current in each phase line into a small current proportionally, while achieving electrical isolation.

3. The CT self-power supply protection device as described in claim 1, characterized in that, The fault current detection circuit also includes a grounding connection GND for detecting ground fault current.

4. The CT self-power supply protection device as described in claim 1, characterized in that, The device adopts a fully analog circuit design and does not contain any digital control components. It achieves fault detection, CT power supply and self-protection functions only through the electrical characteristics between analog circuit components.

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