A saturated compensation current transformer with auxiliary winding

Abstract

This utility model relates to the field of current transformer measurement technology, specifically a saturation-compensated current transformer with an auxiliary winding. It is characterized by comprising an iron core, a primary winding, a secondary winding, an auxiliary winding, an overcurrent detection unit, a signal conditioning circuit, a saturation determination module, and a compensation current injection module. The output of the secondary winding is sequentially connected to the overcurrent detection unit and the signal conditioning circuit, and then connected to the saturation determination module. The saturation determination module includes a comparator. When the determination module detects that the iron core is approaching or entering the saturation region, it drives the compensation current injection module to inject current into the auxiliary winding, forming a reverse magnetomotive force to cancel out the excess portion of the main magnetic flux and stabilize the secondary output. This solution does not require changes to the main magnetic circuit structure and has the advantages of simple structure, fast determination, and accurate compensation. It can effectively reduce saturation errors and improve the measurement accuracy of the current transformer under high current impact conditions and the reliability of relay protection.

Description

Technical Field

[0001] This utility model relates to the field of current transformer measurement technology, and in particular to a saturated compensation type current transformer with auxiliary winding. Background Technology

[0002] Current transformers, commonly used measurement and protection components in power systems, are connected in series with the power line through their primary winding. They proportionally convert large primary currents into smaller secondary currents for use by measurement, metering, and relay protection devices. To ensure metering accuracy and relay protection reliability, the core of the current transformer should be kept within its normal operating magnetic flux range during operation. However, when a short-circuit fault occurs on the primary side or during heavy load operation, the current flowing through the primary winding increases significantly, easily causing the core to enter the magnetic saturation region. In saturation, the core permeability decreases sharply, the transformer's magnetizing inductance decreases, resulting in distortion and reduced amplitude of the secondary output waveform, and may even cause the protection device to malfunction or fail to operate. Existing saturation detection and compensation methods mainly fall into two categories: one relies on external communication or data fusion, calculating and judging the core saturation state by acquiring voltage and current waveforms from multiple points on the primary and secondary sides. This type of method requires additional data transmission channels and high-performance processors, resulting in high hardware costs, and its real-time performance is affected by communication latency. The other type utilizes high-frequency signal injection or complex flux calculation circuits to monitor saturation. However, this type of solution typically requires additional high-frequency generation and detection modules, resulting in complex circuit structures and high power consumption, making it unsuitable for long-term deployment in a large number of operating current transformers. Therefore, how to accurately judge the core saturation state of current transformers without relying on external communication and high-frequency injection, and how to take timely compensation measures when the core approaches saturation to ensure the output accuracy of the transformer and the reliability of protection actions, is a pressing technical problem that needs to be solved. Utility Model Content

[0003] The purpose of this invention is to overcome the problems of existing technologies, such as reliance on external communication or high-frequency signal injection for saturation detection, complex structure, and poor real-time performance. It proposes a device that can determine whether the core of a current transformer is close to saturation and compensate for it locally in real time, so as to ensure the accuracy of the transformer output and the reliability of the protection action.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A saturation-compensated current transformer with an auxiliary winding is characterized by comprising an iron core, a primary winding, a secondary winding, an auxiliary winding, an overcurrent detection unit, a signal conditioning circuit, a saturation determination module, and a compensation current injection module. The output of the secondary winding is sequentially connected to the overcurrent detection unit and the signal conditioning circuit, and then connected to the saturation determination module. The saturation determination module includes a comparator. The determination module determines whether the iron core is close to or has entered a saturation state by detecting the waveform distortion degree and peak value change characteristics of the secondary current signal, thereby driving the compensation current injection module to inject current into the auxiliary winding to form a reverse magnetomotive force, which cancels out the excess part in the main magnetic flux and stabilizes the secondary output.

[0006] Preferably, the overcurrent detection unit is used to acquire the output current signal of the secondary winding.

[0007] Preferably, the saturation determination module determines the change in core magnetic flux density based on the degree of distortion of the secondary current waveform or the change in the peak current.

[0008] Preferably, the filtering section of the signal conditioning circuit includes capacitors C8, C9, and C6 and resistor R. 10 R 11 R 12 An active filter circuit is constructed.

[0009] Preferably, the reference voltage V of the comparator ref The voltage value corresponding to the current signal detected when the iron core is close to the saturation point is set to the equivalent voltage of the knee current after being amplified by the sampling resistor and the signal conditioning circuit.

[0010] In the above technical solution, the saturated compensation current transformer with auxiliary winding provided by this utility model has the following beneficial effects:

[0011] 1. Compared with detection methods based on high-frequency signal injection, this utility model can determine the saturation state by only acquiring low-frequency signals on the secondary side, without the need to add a high-frequency signal source and detection circuit. It has a simple structure, low power consumption, and is easy to achieve long-term online operation.

[0012] 2. This utility model can be directly integrated into existing current transformers without affecting the normal operation of the original main magnetic circuit and secondary circuit, and is suitable for the renovation and upgrading of newly built and in-operation current transformers. Attached Figure Description

[0013] Figure 1 Saturation-compensated current transformer structural schematic diagram Detailed Implementation

[0014] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0015] like Figure 1 As shown, this utility model provides a saturation-compensated current transformer with an auxiliary winding, comprising an iron core, a primary winding, a secondary winding, an auxiliary winding, a saturation determination module, and a compensation current injection module. The primary winding is connected in series with the power line under test and is used to collect the primary side current; the secondary winding is connected to the load (such as a measuring meter or a protective relay) and is used to output a proportionally reduced measuring current; the auxiliary winding is wound at a specific position on the iron core and is electrically connected to the compensation current injection module.

[0016] The saturation detection module is used to detect the saturation trend of the current transformer core. Its input terminal is connected to the secondary winding through a sampling resistor Rs to acquire the secondary side current signal. This signal is first amplified by an operational amplifier, and then passed through capacitors C8, C9, C6, and resistor Rs. 10 R 11 R 12 A filtering and phase compensation network is constructed to extract characteristic components related to the core excitation state. The processed signal is then fed into a comparator and compared with a reference voltage Vref, where V... ref The current transformer core's knee-point characteristics are used as the reference: the equivalent voltage obtained by converting the knee-point current through a sampling resistor and signal conditioning circuit is used as the benchmark, with a 5%~10% lead time allowed to ensure timely triggering when the core approaches saturation. If the detected signal amplitude reaches or exceeds this threshold, the comparator outputs a saturation judgment signal OUT1, which is used to control the subsequent compensation current injection module.

[0017] The input terminal of the compensation current injection module is electrically connected to the output terminal of the saturation determination module, and its output terminal is connected to the auxiliary winding. When the saturation determination module outputs a saturation signal, the compensation current injection module generates a compensation current in the opposite direction to the primary current magnetic field. This current applies a reverse magnetomotive force to the iron core through the auxiliary winding, offsetting part of the excitation flux and reducing the core flux density to the unsaturated range. This improves the secondary output waveform and reduces amplitude error.

[0018] In actual operation, this device can monitor the excitation state of the current transformer in real time and automatically execute the compensation process. The entire detection and compensation control is completed locally without relying on external communication or high-frequency signal sources, which can significantly improve the accuracy and reliability of the current transformer under high current or transient impact conditions.

[0019] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A saturated compensation current transformer with auxiliary winding, characterized in that, It includes an iron core, a primary winding, a secondary winding, an auxiliary winding, an overcurrent detection unit, a signal conditioning circuit, a saturation determination module, and a compensation current injection module. The output of the secondary winding is connected to the overcurrent detection unit and the signal conditioning circuit in sequence, and then connected to the saturation determination module. The saturation determination module includes a comparator. The determination module determines whether the iron core is close to or has entered a saturation state by detecting the waveform distortion and peak change characteristics of the secondary current signal. Then, it drives the compensation current injection module to inject current into the auxiliary winding to form a reverse magnetomotive force, which cancels the excess part in the main magnetic flux and stabilizes the secondary output.

2. A saturated compensation current transformer with auxiliary winding according to claim 1, characterized in that, The overcurrent detection unit is used to collect the output current signal of the secondary winding.

3. A saturated compensation current transformer with auxiliary winding according to claim 1, characterized in that, The saturation determination module judges the change in core magnetic flux density based on the degree of distortion of the secondary current waveform or the change in the peak current.

4. A saturated compensation current transformer with auxiliary winding according to claim 1, characterized in that, The filtering section of the signal conditioning circuit includes capacitors C8, C9, and C6 and resistor R. 10 R 11 R 12 An active filter circuit is constructed.

5. A saturated compensation current transformer with auxiliary winding according to claim 1, characterized in that, The reference voltage Vref of the comparator is set to the voltage value corresponding to the current signal detected when the iron core is close to the saturation point. It is the equivalent voltage of the knee current after being amplified by the sampling resistor and the signal conditioning circuit.

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