CN102981035B - Current clamp and power quality monitoring device - Google Patents

Abstract

The invention discloses a current clamp and a power quality monitoring device. Wherein, the current clamp includes: a current sensing device, including an iron core, the iron core has a cavity matched with the measuring body, and electromagnetic induction is generated when the measuring body passes through the cavity, and the current sensing device obtains the temperature in the measuring body through electromagnetic induction. The ground current signal; the DC component separation device, connected with the current sensing device, is used to separate the ground current signal into AC and DC current, so as to obtain and output the DC component signal and the AC component signal. Through the present invention, the synchronous measurement of the AC current signal and the DC current signal of the center point grounding current of the transformer is realized, so that the research and the DC bias magnetic field of the center point grounding of the transformer can be carried out according to the synchronous measurement data of AC and DC in the center point grounding current of the transformer Monitoring of power quality.

Description

Current clamp and power quality monitoring device

technical field

The invention relates to the field of electric equipment, in particular to a current clamp and a power quality monitoring device.

Background technique

A large DC will be generated in the transformer winding running online. We call this phenomenon of DC current in the AC current as the current bias phenomenon. The DC bias phenomenon in the transformer winding can be caused by the following two reasons:

(1) The geomagnetic "storm" generated by the interaction between the dynamic change of the solar plasma wind and the geomagnetic field. The change of the geomagnetic field will induce a potential gradient on the earth's surface, and its magnitude depends on the ground conductivity and the severity of the geomagnetic storm. When this low-frequency electric field with a certain duration acts on a power transformer whose neutral point is grounded, it will The geomagnetic induction current induced in the winding has a frequency between 0.01 and 1 Hz. Compared with the 50 Hz AC system, it can be approximately regarded as DC. This DC current is large in value but short in duration.

(2) Parallel operation of DC transmission lines and AC transmission lines or loads with asymmetrical voltage-current relationship curves in the AC network. The DC transmission system often adopts the single-pole operation mode, because the good conductor of the earth can be used, and a wire can be saved to save costs. Since there is a large direct current flowing underground for a long time, surface current will be generated in a certain area around the converter station. If the transformer in the substation of the AC transmission system running in parallel with it is not far from the converter station, it will be disturbed. The direct manifestation of this interference is to generate a DC component in the excitation current of the AC transformer through the grounded neutral point of the AC transformer. The DC current value is small, but the duration is long.

The DC bias phenomenon occurs in the transformer running on-line. The DC magnetic flux makes the transformer iron core appear more serious magnetic saturation every half cycle, the excitation current is highly distorted, and a large number of harmonics are generated. Increased losses, increased noise and vibration. Severe magnetic saturation will cause the magnetic flux that is normally closed in the iron core to partly leave the iron core, that is, the leakage flux increases, thereby increasing the stray loss in the metal structural parts of the transformer, which may cause it to overheat, destroy insulation, damage Transformer or reduce its service life. In addition, the DC bias is also an important factor affecting the power quality of the power system.

In order to reduce the loss of DC bias on the transformer and the impact on power quality, it is necessary to measure the AC current and DC current at the center point of the transformer grounded to conduct in-depth research on the DC bias phenomenon of the transformer. However, the existing technology is aimed at large For the special cross-section medium of the transformer center point grounding steel plate, the flexible current clamp can only measure the AC current of the transformer center point grounding steel plate, and cannot measure the AC and DC component currents of the transformer center point grounding steel plate at the same time.

Aiming at the problem that the existing technology cannot measure the AC and DC components of the large-scale transformer center-point grounded steel plate at the same time, so that it is impossible to conduct research on the DC bias of the transformer based on the AC and DC components grounded at the transformer center point, no effective solution has been proposed yet.

Contents of the invention

Aiming at the problem in the related technology that the AC and DC components of the large-scale transformer center point grounded steel plate cannot be measured at the same time, so that it is impossible to conduct research on the DC bias of the transformer based on the AC and DC components of the transformer center point grounded steel plate, no effective solution has been proposed so far. Therefore, the main purpose of the present invention is to provide a current clamp and a power quality monitoring device to solve the above problems.

In order to achieve the above object, according to one aspect of the present invention, a current clamp is provided, which includes: a current sensing device, including an iron core, the iron core has a cavity that matches the measurement body, when the measurement body passes through the cavity Electromagnetic induction is generated during the cavity, and the current sensing device obtains the ground current signal in the measuring body through electromagnetic induction; the DC component separation device is connected with the current sensing device, and is used to separate the ground current signal from AC and DC to obtain and output DC Component signal and AC component signal.

Further, the current sensing device includes: an iron core winding wound on the iron core, wherein the iron core includes a first sub-iron core and a second sub-iron core, wherein one end of the first sub-iron core is a closed end, and the other end The open end of the first sub-core is connected to the second sub-core to form a cavity inside the core, wherein the cavity is a rectangular cavity; the core winding is wound on the first sub-core .

Further, the DC component separation device includes: a DC component separation circuit, connected to the first output end of the iron core winding, and used for current separation of the ground current signal output by the first output end of the iron core winding, so as to obtain the DC component signal ; The DC output terminal is connected with the DC component separation circuit for outputting the DC component signal; the AC output terminal is connected with the second output terminal of the iron core winding and is used for outputting the grounding current signal.

Further, the DC component separation device includes: a current supply circuit, connected to the DC component separation circuit, for supplying electric energy to the DC component separation sub-circuit.

Further, the open end of the first sub-core includes a first sub-open end and a second sub-open end, wherein the first sub-open end is connected to the first end of the second sub-core through a hinge, and the first sub-open end In the state where the iron core is engaged with the second sub-iron core, the opening end of the second sub-iron core is connected to the second end of the second sub-iron core, and the first sub-iron core is engaged with the second sub-iron core to form an iron core.

Further, the hinge includes an elastic locking mechanism.

Further, a handle is installed outside the closed end of the first sub-core, and the DC component separation device is installed inside the handle.

Further, an insulating material is wrapped on the outside of the current sensing device.

In order to achieve the above object, according to another aspect of the present invention, a power quality monitoring device is provided, and the power quality monitoring device includes a current clamp.

Further, the power quality monitoring device also includes: a first collection device connected to the AC output end of the current clamp for collecting AC current signals; a second collection device connected to the DC output end of the current clamp for collecting DC current Signal.

According to the present invention, the iron core of the current sensing device of the current clamp has a cavity that matches the measuring body, so that electromagnetic induction is generated when the measuring body passes through the cavity of the iron core, so that the current sensing device obtains the measuring body through electromagnetic induction The ground current signal in the ground current signal, and then the DC component separation device separates the DC and AC components of the ground current signal, obtains and outputs the DC component signal and the AC component signal, and solves the problem that the existing technology cannot simultaneously measure the grounding steel plate at the center point of a large transformer Therefore, it is impossible to study the DC bias magnetic field of the transformer according to the AC and DC components of the center point grounding of the transformer. The synchronous measurement of the AC current signal and the DC current signal of the grounding current of the transformer center point is realized, so that it can be According to the synchronous measurement data of AC and DC in the center point grounding current of the transformer, the research on the DC bias magnetic field of the center point grounding of the transformer and the monitoring of the power quality are carried out.

Description of drawings

The accompanying drawings described here are used to provide a further understanding of the present invention and constitute a part of the application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention. In the attached picture:

Fig. 1 is a schematic structural view of a current clamp according to an embodiment of the present invention;

2 is a schematic diagram of the working principle of a current clamp according to an embodiment of the present invention;

Fig. 3 is a detailed structural schematic diagram of a current clamp according to an embodiment of the present invention; and

Fig. 4 is a schematic structural diagram of a power quality monitoring device according to an embodiment of the present invention.

Detailed ways

It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and examples.

FIG. 1 is a schematic structural diagram of a current clamp according to an embodiment of the present invention. Fig. 2 is a schematic diagram of the working principle of the current clamp according to the embodiment of the present invention. Fig. 3 is a schematic diagram of a detailed structure of a current clamp according to an embodiment of the present invention.

As shown in Figure 1, the current clamp provided by the present invention includes: a current induction device 10, including an iron core 101, the iron core 101 has a cavity matched with the measurement body, and when the measurement body passes through the cavity, electromagnetic induction is generated, and the current The induction device 10 obtains the ground current signal in the measurement body through electromagnetic induction; the DC component separation device 30 is connected with the current induction device 10, and is used to separate the ground current signal from AC and DC current, so as to obtain and output the DC component signal and the AC current signal. component signal.

Using the current clamp of the present invention, the current sensing device and the measuring body generate electromagnetic induction to obtain the ground current signal in the measuring body, the DC component separating device is connected with the current sensing device, and the grounding current signal obtained by the DC component separating device is exchanged Separated from the DC current to obtain and output the DC component signal and the AC component signal, wherein the current sensing device includes an iron core, the iron core has a cavity that matches the measurement body, and electromagnetic induction is generated when the measurement body passes through the cavity, The current sensing device obtains the ground current signal in the measuring body through electromagnetic induction. According to the present application, the iron core of the current sensing device of the current clamp has a cavity that matches the measuring body, so that the measuring body can generate electromagnetic induction when passing through the cavity of the iron core, so that the current sensing device obtains the measurement body through electromagnetic induction. The ground current signal, and then the DC component separation device separates the DC and AC components of the ground current signal, obtains and outputs the DC component signal and the AC component signal, and solves the problem that the grounding steel plate at the center point of the large transformer cannot be measured at the same time in the prior art AC and DC components, so that it is impossible to study the DC bias of the transformer based on the AC and DC components of the transformer center point grounding. The simultaneous measurement of the AC current signal and the DC current signal of the transformer center point grounding current is realized, so that it can be based on The synchronous measurement data of AC and DC in the ground current of the transformer center point is used to study the DC bias of the transformer.

Wherein, the measuring body may be a transformer center point grounding device, specifically, the transformer center point grounding device may be a transformer center point grounding steel plate.

In the above-mentioned embodiment of the present application, as shown in FIG. 2 , the current sensing device 10 includes: an iron core winding wound on an iron core 101, wherein the iron core 101 includes a first sub-iron core and a second sub-iron core, Specifically, as shown in FIG. 3 , one end of the first sub-core is a closed end, and the other end is an open end, and the open end of the first sub-core is connected to the second sub-core to form a The cavity, wherein the cavity is a rectangular cavity, and the measuring body passes through the rectangular cavity, so that the iron core 101 and the measuring body generate electromagnetic induction, and an electromagnetic field is generated in the iron core 101; the iron core winding is wound on the first sub-iron core , used to acquire ground current signals through electromagnetic induction with electromagnetic fields.

Specifically, in the current clamp shown in FIG. 3 , the open end of the first sub-core includes a first sub-open end and a second sub-open end, wherein the first sub-open end is connected to the second sub-open end of the second sub-core through a hinge. One end is connected, in the state where the first sub-core and the second sub-core are fastened, the second sub-open end is connected to the second end of the second sub-core, and the first sub-core and the second sub-core The snap-fit connection forms the core 101 .

Wherein, the hinge in the above embodiments may include an elastic locking mechanism. Specifically, the elastic locking mechanism uses a spring to achieve elastic locking.

Specifically, as shown in Figures 2 and 3, the second sub-core connected to the open end of the first sub-core of the current clamp in the above embodiment is opened to open the rectangular cavity of the core 101, so that the measurement The main body passes through the rectangular cavity, and then the first sub-core and the second sub-core are buckled, so that the inside of the core 101 forms the above-mentioned rectangular cavity, and then the ground current signal of the measuring body can be measured through the current clamp. During the measurement process, the measuring body is used as a primary winding. Since there is an alternating current flowing through the measuring body, the iron core 101 can induce the alternating current and generate electromagnetic force, and then the iron core winding wound on the iron core 101 (the The iron core winding (as the secondary winding) obtains the ground current signal through electromagnetic induction, and outputs the ground current signal to the DC component separation device 30 .

Wherein, the length of the rectangular cavity may be 50 cm, and the width of the rectangular cavity may be 10 cm, wherein, as shown in FIG. 3 , the width of the rectangular cavity is also the opening width of the opening end of the first sub-core.

Specifically, the current clamp is applied to the measurement of the transformer center point ground current signal, as shown in Figure 2 and Figure 3, the first sub-core of the current clamp has an open end, and a cavity is formed inside the core 101 The size of the measuring body matches the measurement body, so that the measurement of the grounding current signal of the wide-section conductor grounded at the center point of the transformer can be realized.

In the above embodiments of the present invention, the DC component separation device 30 may include: a DC component separation circuit, connected to the first output end of the iron core winding, and used to perform a ground current signal output from the first output end of the iron core winding The current separation is to obtain the DC component signal; the DC output terminal is connected to the DC component separation circuit for outputting the DC component signal; the AC output terminal is connected to the second output terminal of the iron core winding and is used for outputting the ground current signal. Among them, the ground current signal output by the AC output terminal is used as the ground current signal. Although the ground current signal contains both the AC component signal and the DC component signal, in the subsequent processing of the AC current signal, the DC component is not It will not affect subsequent processing.

Wherein, the DC component separation device 30 may further include: a current supply circuit connected to the DC component separation circuit for providing electric energy for the DC component separation sub-circuit.

Through the above-mentioned embodiments of the present application, the current clamp includes an openable iron core 101, an iron core winding wound on the iron core 101, a DC component separation circuit, and dual output terminals. The iron core 101 and the iron core winding can cooperate to pass electromagnetic induction Obtain the ground current signal of the measurement body, and then the DC component separation circuit separates the DC component in the ground current signal, and outputs the DC and AC component signals separately through the dual output terminals, so that the AC current and DC in the measurement body can be measured simultaneously portion.

In the above embodiments of the present invention, a handle may be installed outside the closed end of the first sub-core, and the DC component separation device 30 may be installed inside the handle. The DC component separation device 30 can be installed inside the handle, which can reduce the volume of the current clamp, thus making the current clamp more convenient to carry.

In addition, insulating materials can be wrapped on the outside of the current sensing device 10, so that safe measurement can be realized, the safety of the measurer can be well protected, and safety accidents can be reduced.

FIG. 4 is a schematic structural diagram of a power quality monitoring device according to an embodiment of the present invention. The power quality monitoring device shown in FIG. 4 includes a current clamp 1 .

According to the present application, the iron core of the current sensing device of the current clamp has a cavity that matches the measuring body, so that electromagnetic induction is generated when the measuring body passes through the cavity of the iron core, so that the current sensing device obtains the measuring body through electromagnetic induction The ground current signal in the ground current signal, and then the DC component separation device separates the DC and AC components of the ground current signal, obtains and outputs the DC component signal and the AC component signal, and solves the problem that the existing technology cannot simultaneously measure the grounding steel plate at the center point of a large transformer Therefore, it is impossible to study the DC bias magnetic field of the transformer according to the AC and DC components of the center point grounding of the transformer. The synchronous measurement of the AC current signal and the DC current signal of the grounding current of the transformer center point is realized, so that it can be The power quality monitoring is carried out according to the synchronous measurement data of AC and DC in the center point grounding current of the transformer.

In the above-mentioned embodiment of the present invention, the power quality monitoring device may also include: a first collection device 3, connected to the AC output end of the current clamp, for collecting the AC current signal; a second collection device 5, connected to the DC output of the current clamp The output terminal is connected to collect the DC current signal. Wherein, the AC current signal output by the AC output terminal is the above-mentioned ground current signal, although the ground current signal includes both the AC component signal and the DC component signal, but in the subsequent process of processing the AC current signal, the The DC component does not affect subsequent processing.

The power quality monitoring device in the above embodiments can measure the DC component. Wherein, the processing device in the power quality monitoring device can perform current analysis on the current signals collected by the first acquisition device and the second acquisition device. Specifically, the current analysis includes: analyzing the distribution law of the DC current signal on the time axis, Comparatively analyze the waveform of the DC current signal and the waveform of the AC current signal, compare and analyze the waveform of the AC current signal and the waveform of the DC current signal relative to the power quality monitoring data of the monitoring point, and compare and analyze the results of the above distribution laws and waveforms Obtain the occurrence rule of the DC current component at this power grid node, study the correlation between the DC bias phenomenon and the power quality event according to the occurrence rule, and predict the DC current component (DC bias) while obtaining the power quality monitoring data generation.

Specifically, as shown in Figure 4, the first acquisition device 3 is connected to the AC output end of the current clamp, and the second acquisition device 5 is connected to the DC output end, and the first acquisition device 3 and the second acquisition device 5 respectively collect the current clamp The AC current signal and the DC current signal are output, and the AC current signal and the DC current signal are applied to subsequent power quality monitoring.

From the above description, it can be seen that the present invention achieves the following technical effects: through this application, the iron core of the current sensing device of the current clamp has a cavity that matches the measurement body, so that when the measurement body passes through the iron core Electromagnetic induction is generated when the cavity is in the cavity, so that the current sensing device obtains the ground current signal in the measurement body through electromagnetic induction, and then the DC component separation device separates the DC and AC components of the ground current signal, and obtains and outputs the DC component signal and the AC component. The component signal solves the problem in the prior art that the AC and DC components of the grounded steel plate at the center point of the large transformer cannot be measured at the same time, so that it is impossible to conduct research on the DC bias of the transformer based on the AC and DC components grounded at the center point of the transformer. Synchronous measurement of the AC current signal and DC current signal of the center point ground current, so that the research of the DC bias magnetic field of the transformer center point ground and the monitoring of the power quality can be carried out according to the synchronous measurement data of AC and DC in the center point ground current of the transformer.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (8)

1. a current clamp, is characterized in that, comprising:

Current sensing means, comprise iron core, described iron core has the cavity matched with measurement body, and when described measurement body produces electromagnetic induction through during described cavity, described current sensing means obtains the ground current signal in described measurement body by described electromagnetic induction; Described current sensing means comprises: be wrapped in the iron core winding on described iron core, wherein, described iron core comprises the first sub-iron core and the second sub-iron core, wherein, one end of described first sub-iron core is blind end, and the other end is openend, the openend of described first sub-iron core is connected with the second sub-iron core, to form described cavity in the inside of described iron core, wherein, described cavity is rectangular enclosure; Described iron core winding is wrapped on described first sub-iron core; The openend of described first sub-iron core comprises the first sub-openend and the second sub-openend, wherein, described first sub-openend is connected by the first end of articulated elements with described second sub-iron core, under the state that described first sub-iron core and described second sub-iron core fasten, described second sub-openend is connected with the second end of described second sub-iron core, and described first sub-iron core and described second sub-iron core are fastened and connected and form described iron core;

DC component tripping device, is connected with described current sensing means, for described ground current signal is carried out AC and DC current separation, to obtain and output DC component signal and AC compounent signal,

Wherein, the width of described rectangular enclosure is the A/F of the openend of described first sub-iron core, and described measurement body is transformer central point earthing device, and described transformer central point earthing device is transformer central point ground connection steel plate.

2. current clamp according to claim 1, is characterized in that, described DC component tripping device comprises:

DC component separation circuit, is connected with the first output terminal of described iron core winding, carries out current separation, to obtain DC component signal for the ground current signal exported the first output terminal of described iron core winding;

DC output end, is connected with described DC component separation circuit, for exporting described DC component signal;

Ac output end, is connected with the second output terminal of described iron core winding, for exporting described ground current signal.

3. current clamp according to claim 2, is characterized in that, described DC component tripping device comprises:

Current suppling circuit, is connected with described DC component separation circuit, for providing electric energy for described DC component separation circuit.

4. current clamp according to claim 1, is characterized in that, described articulated elements comprises elastic locking mechanism.

5. current clamp according to claim 1, is characterized in that, be provided with handle in the outside of the blind end of described first sub-iron core, described DC component tripping device is arranged on the inside of described handle.

6. current clamp according to claim 1, is characterized in that, at the outer wrap insulating material of described current sensing means.

7. an equipment for monitoring power quality, is characterized in that, comprises the current clamp in claim 1 to 6 described in any one.

8. equipment for monitoring power quality according to claim 7, is characterized in that, described equipment for monitoring power quality also comprises:

First harvester, is connected with the ac output end of described current clamp, for gathering ac current signal;

Second harvester, is connected with the DC output end of described current clamp, for gathering DC current signal.