Secondary open circuit protection device for current transformer of power distribution cabinet

Abstract

The utility model relates to a secondary open circuit protection device for a current transformer of a power distribution cabinet, and relates to the field of power distribution safety. Iron cores of a primary side winding and a secondary side winding of the current transformer are designed into two groups of half core bodies which can be butted and separated, the half core bodies surrounded by the secondary side winding of the current transformer are connected with an insulated transmission assembly, and the transmission assembly controls the two half core bodies to be butted or separated; an open circuit detection circuit used for detecting the open circuit of the secondary loop of the current transformer is arranged, and the open circuit detection circuit is electrically connected with the control unit through an optical coupling isolation communication line; the control unit is electrically connected with the short-circuit circuit through the isolation circuit, controls the short-circuit circuit to short-circuit a secondary winding terminal of the current transformer when the control unit detects that the secondary side of the current transformer is open through the open-circuit detection circuit, and controls the short-circuit circuit to short-circuit the secondary winding terminal of the current transformer when the control unit detects that the secondary winding of the current transformer is open through the open-circuit detection circuit. And the transmission assembly is controlled to separate the two half core bodies.

Description

Technical Field

[0001] The utility model relates to the field of power distribution safety, in particular to a secondary open circuit protection device for a current transformer of a power distribution cabinet. Background Art

[0002] Electricity safety in construction is an important requirement for safe construction. When setting up a construction distribution cabinet, current sensors need to be installed to monitor the current status in order to understand the power supply status.

[0003] The current transformer is composed of a closed iron core and windings. The primary winding of the current transformer has few turns and is connected in series in the circuit of the current to be measured. The secondary winding has more turns and is connected in series in the measuring instrument and protection circuit. When the current transformer is working, its secondary circuit is always closed, so the impedance of the series coil of the measuring instrument and the protection circuit is very small, and the working state of the current transformer is close to short circuit. In this case, the magnetic flux generated by the primary current and secondary current of the current transformer cancel each other out, so that the magnetic flux density in the iron core is maintained at a low level, so the secondary voltage is also low. When the secondary winding and secondary circuit of the current transformer are open, the primary current does not change, the secondary circuit is disconnected, the resistance is very large, and the primary magnetic flux cannot be offset, which will lead to the following serious consequences: (1) high voltage appears on the secondary side, endangering the safety of people and instruments; (2) overheating occurs, which may burn the winding; (3) increase the measurement error. In the prior art, there is a solution for determining whether an open circuit occurs on the secondary side of a current transformer by detecting the secondary side current or voltage, and controlling the secondary side of the current transformer to be short-circuited for protection after the open circuit occurs. However, the open circuit may occur in the secondary winding of the current transformer rather than in the load circuit of the secondary side of the current transformer. General short-circuit measures are connected in parallel with the load circuit and cannot play a protective role when the secondary winding of the current transformer is open. Utility Model Content

[0004] In order to solve the above technical problem or at least partially solve the above technical problem, the utility model provides a secondary open circuit protection device for a current transformer of a power distribution cabinet.

[0005] The utility model provides a secondary open circuit protection device for a current transformer of a power distribution cabinet, comprising: the iron cores of the primary and secondary windings of the current transformer are designed to be two groups of half cores that can be connected and separated, wherein the half cores surrounded by the secondary windings of the current transformer are connected to an insulated transmission component, and the transmission component controls the connection or separation of the two half cores;

[0006] An open circuit detection circuit is provided for detecting an open circuit of a secondary circuit of a current transformer, and the open circuit detection circuit is electrically connected to a control unit via a communication line isolated by an optical coupler;

[0007] The control unit is electrically connected to the short-circuit circuit through the isolation circuit. When the control unit determines through the open circuit detection circuit that the secondary side of the current transformer is open, the control unit controls the short-circuit circuit to short-circuit the secondary winding terminals of the current transformer. When the control unit determines through the open circuit detection circuit that the secondary winding of the current transformer is open, the control unit controls the transmission component to separate the two half cores.

[0008] Furthermore, the short-circuit circuit includes a short-circuit switch, which is connected to a switch driving circuit, a transformer for drawing power, the transformer is electrically connected to an AC-DC conversion circuit, the AC-DC conversion circuit provides the DC power required by the driving circuit of the short-circuit switch, and an optocoupler switch controlled by a control unit.

[0009] Furthermore, the open circuit detection circuit includes a current sampling unit and a voltage sampling unit which are arranged in the secondary side loop of the current transformer.

[0010] Furthermore, the control unit is connected to an optical fiber temperature sensor arranged on the current transformer core and a temperature transmitter arranged in the environment, and the optical fiber temperature sensor and the temperature transmitter are electrically connected to the control unit.

[0011] Furthermore, the control unit is connected to an arc sensor, and the arc sensor is arranged at the secondary winding of the current transformer to detect an open-circuit arc of the secondary winding.

[0012] Furthermore, the transmission assembly includes an insulating connection seat for fixing the half core where the secondary winding of the current transformer is located, the insulating connection seat is slidably set on a slide rail, the end of the slide rail is fixed to an electric telescopic rod that drives the insulating connection seat, and the electric telescopic rod is connected to the control unit through a telescopic rod driving circuit.

[0013] Furthermore, the control unit is electrically connected to a current transformer abnormality warning unit.

[0014] The above technical solution provided by the embodiment of the utility model has the following advantages compared with the prior art:

[0015] The utility model designs the iron cores of the primary and secondary windings of a current transformer into two groups of half cores that can be connected and separated. The half core surrounded by the secondary winding of the current transformer is connected to an insulated transmission component, and the transmission component controls the connection or separation of the two half cores; an open circuit detection circuit for detecting the open circuit of the secondary circuit of the current transformer is provided, and the open circuit detection circuit is electrically connected to a control unit via a communication line isolated by an optical coupler; the control unit is electrically connected to a short circuit through an isolation circuit, and when the control unit determines that the secondary side of the current transformer is open through the open circuit detection circuit, the short circuit is controlled to short-circuit the secondary winding terminals of the current transformer, and when the control unit determines that the secondary winding of the current transformer is open through the open circuit detection circuit, the transmission component is controlled to separate the two half cores. In response to an open circuit occurring outside the secondary winding of a current transformer, the control unit of the present application controls the short-circuit circuit to short-circuit the secondary winding of the current transformer for protection. If the open circuit detection circuit is still abnormal after the short circuit, the control unit controls the transmission assembly to separate the two half cores of the iron core by a sufficient distance so that the magnetic induction between the primary winding and the secondary winding of the current transformer is weakened and disappears, thereby achieving protection when the secondary winding is accidentally open-circuited and avoiding the risks caused by the open circuit of the secondary winding of the current transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings herein are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present utility model, and together with the description, are used to explain the principles of the present utility model.

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the utility model or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0018] Figure 1 A schematic diagram of the circuit architecture of a secondary open circuit protection device for a current transformer in a power distribution cabinet provided by the utility model;

[0019] Figure 2 The utility model provides a schematic diagram of a transmission component of a secondary open circuit protection device of a current transformer in a power distribution cabinet.

[0020] The symbols and their meanings in the figure are as follows:

[0021] 1. Iron core, 2. Insulation connection seat, 3. Slide rail, 4. Electric telescopic rod. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the embodiment of the utility model clearer, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is a part of the embodiment of the utility model, not all of the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0023] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0024] See also Figure 1 As shown, an embodiment of the utility model provides a secondary open circuit protection device for a current transformer in a power distribution cabinet, and provides a protection solution for a secondary open circuit of a current transformer.

[0025] The present application designs the core of the primary and secondary windings of the current transformer into two groups of half cores that can be docked and separated, wherein the half core surrounded by the secondary winding of the current transformer is connected to an insulated transmission component, and the transmission component controls the docking or separation of the two half cores. The transmission component is controlled to connect to the control unit via an isolation circuit. An exemplary transmission component includes an insulating connection seat that fixes the half core where the secondary winding of the current transformer is located, and the insulating connection seat is slidably set on a slide rail. The end of the slide rail is fixed to an electric telescopic rod that drives the insulating connection seat, and the electric telescopic rod is connected to the control unit via a telescopic rod driving circuit.

[0026] The present application is provided with an open circuit detection circuit for detecting an open circuit of a secondary circuit of a current transformer, and the open circuit detection circuit is electrically connected to a control unit via a communication line isolated by an optical coupler.

[0027] In a specific implementation process, the open circuit detection circuit includes a current sampling unit arranged in the secondary side loop of the current transformer. The number of measurement channels of the current sampling unit is not less than the number of segments of the secondary winding of the current transformer, and the current sampling unit is provided with a communication interface, and the communication interface of the current sampling unit is electrically connected to the control unit through a communication line isolated by an optical coupler.

[0028] The open circuit detection circuit includes a voltage sampling unit connected in parallel to the secondary side loop of the current transformer, the number of measurement channels of the voltage sampling unit is not less than the number of segments of the secondary winding of the current transformer. The voltage sampling unit is provided with a communication interface, and the communication interface of the voltage sampling unit is electrically connected to the control unit through an optically isolated communication line.

[0029] The control unit is electrically connected to the short-circuit circuit. When the control unit determines that the secondary side of the current transformer is open-circuited through the open-circuit detection circuit, the control unit controls the short-circuit circuit to short-circuit the secondary winding terminal of the current transformer. The short-circuit circuit includes a short-circuit switch for short-circuiting the secondary side of the current transformer. The short-circuit switch adopts a contactless switch. The short-circuit switch is connected to a switch drive circuit. The switch drive circuit is connected to the control unit through an isolation circuit. The switch drive circuit includes: a transformer for taking power, the transformer is electrically connected to an AC-DC conversion circuit, the AC-DC conversion circuit provides the DC power required by the drive circuit of the short-circuit switch, and an optical coupler switch controlled by the control unit. The optical coupler switch drives the short-circuit switch to turn on or off.

[0030] The control unit determines whether the secondary side of the current transformer is open based on the current signal and the voltage signal collected by the current sampling unit and the voltage sampling unit. The control unit determines that the secondary side of the current transformer is open when the current sampling unit samples the secondary circuit current of the current transformer at a current lower than 0.2 amperes. When the secondary circuit of the current transformer is open, the voltage gradually increases, and the secondary circuit voltage of the current transformer is collected by the voltage sampling unit. The control unit determines that the secondary side of the current transformer is open based on the increase in voltage. The control unit controls the short-circuit switch to short-circuit the secondary winding terminals of the current transformer to reduce the voltage of the secondary circuit of the current transformer.

[0031] After the control unit controls the short-circuit switch to short-circuit the secondary winding terminal of the current transformer, the control unit obtains the current of the current sampling unit and the voltage of the voltage sampling unit in the open circuit detection circuit. When the current is lower than 0.2A after the secondary winding terminal of the current transformer is short-circuited, or the voltage still rises, the control unit determines that the secondary winding of the current transformer is open. That is, when the control unit determines that the secondary winding of the current transformer is open through the open circuit detection circuit, the transmission component is controlled to separate the two half cores. This makes the electromagnetic induction effect of the current transformer ineffective, and provides uninterrupted protection.

[0032] The control unit is connected to an optical fiber temperature sensor arranged on the core of the current transformer and a temperature transmitter arranged in the environment, and the optical fiber temperature sensor and the temperature transmitter are electrically connected to the control unit. In a specific implementation process, the optical fiber temperature sensor is arranged on the half core where the primary winding of the current transformer is located.

[0033] The control unit is connected to an arc sensor, and the arc sensor is arranged at the secondary winding of the current transformer to detect the arc light of the secondary winding open circuit, so as to assist in the secondary winding open circuit detection of the current transformer.

[0034] The control unit is electrically connected to a warning unit for prompting abnormal current transformers, the warning unit includes an indicator light indicating abnormal current transformers, and the warning unit includes a display screen for prompting abnormal current transformer information.

[0035] The working principle of the secondary open circuit protection device of the current transformer of the power distribution cabinet provided by the embodiment of the utility model is as follows:

[0036] The utility model designs the iron cores of the primary and secondary windings of a current transformer into two groups of half cores that can be connected and separated. The half core surrounded by the secondary winding of the current transformer is connected to an insulated transmission component, and the transmission component controls the connection or separation of the two half cores; an open circuit detection circuit for detecting the open circuit of the secondary circuit of the current transformer is provided, and the open circuit detection circuit is electrically connected to a control unit via a communication line isolated by an optical coupler; the control unit is electrically connected to a short circuit through an isolation circuit, and when the control unit determines that the secondary side of the current transformer is open through the open circuit detection circuit, the short circuit is controlled to short-circuit the secondary winding terminals of the current transformer, and when the control unit determines that the secondary winding of the current transformer is open through the open circuit detection circuit, the transmission component is controlled to separate the two half cores. In response to an open circuit occurring outside the secondary winding of a current transformer, the control unit of the present application controls the short-circuit circuit to short-circuit the secondary winding of the current transformer for protection. If the open circuit detection circuit is still abnormal after the short circuit, the control unit controls the transmission assembly to separate the two half cores of the iron core by a sufficient distance so that the magnetic induction between the primary winding and the secondary winding of the current transformer is weakened and disappears, thereby achieving protection when the secondary winding is accidentally open-circuited and avoiding the risks caused by the open circuit of the secondary winding of the current transformer.

[0037] In the embodiments provided by the present utility model, it should be understood that the disclosed devices can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the description division of the circuit is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling shown or discussed can be indirect coupling through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0038] The above description is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but should conform to the widest scope consistent with the principles and novel features applied herein.

Claims

1. A secondary open circuit protection device for current transformer of power distribution cabinet, characterized in that: include: The iron cores of the primary and secondary windings of the current transformer are two groups of half cores that can be connected and separated, wherein the half core surrounded by the secondary winding of the current transformer is connected to an insulated transmission component, and the transmission component controls the connection or separation of the two half cores; An open circuit detection circuit is provided for detecting an open circuit of a secondary circuit of a current transformer, and the open circuit detection circuit is electrically connected to a control unit via a communication line isolated by an optical coupler; The control unit is electrically connected to the short-circuit circuit through the isolation circuit. When the control unit determines through the open circuit detection circuit that the secondary side of the current transformer is open, the control unit controls the short-circuit circuit to short-circuit the secondary winding terminals of the current transformer. When the control unit determines through the open circuit detection circuit that the secondary winding of the current transformer is open, the control unit controls the transmission component to separate the two half cores.

2. According to claim 1, the secondary open circuit protection device of the current transformer of the power distribution cabinet is characterized in that: The short-circuit circuit includes: a short-circuit switch, the short-circuit switch is connected to a switch driving circuit, a transformer for taking power, the transformer is electrically connected to an AC-DC conversion circuit, the AC-DC conversion circuit provides the DC power required by the driving circuit of the short-circuit switch, and an optocoupler switch controlled by a control unit, the optocoupler switch drives the short-circuit switch to be turned on or off.

3. The secondary open circuit protection device for current transformer of power distribution cabinet according to claim 1 is characterized in that: The open circuit detection circuit includes a current sampling unit and a voltage sampling unit which are arranged in the secondary side loop of the current transformer.

4. The secondary open circuit protection device for current transformer of power distribution cabinet according to claim 1, characterized in that: The control unit is connected to an optical fiber temperature sensor arranged on the current transformer core and a temperature transmitter arranged in the environment, and the optical fiber temperature sensor and the temperature transmitter are electrically connected to the control unit.

5. The secondary open circuit protection device for current transformer of power distribution cabinet according to claim 1, characterized in that: The control unit is connected to an arc sensor, and the arc sensor is arranged at the secondary winding of the current transformer to detect an open-circuit arc of the secondary winding.

6. The secondary open circuit protection device for current transformer of power distribution cabinet according to claim 1, characterized in that: The transmission assembly includes an insulating connection seat for fixing the half core where the secondary winding of the current transformer is located. The insulating connection seat is slidably arranged on a slide rail. The end of the slide rail is fixed to drive an electric telescopic rod for driving the insulating connection seat. The electric telescopic rod is connected to a control unit through a telescopic rod driving circuit.

7. The secondary open circuit protection device for current transformer of power distribution cabinet according to claim 1, characterized in that: The control unit is electrically connected to a current transformer abnormality warning unit.

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