Shielded cable for partial discharge detection of power equipment

Abstract

The invention provides a shielded cable for partial discharge detection of power equipment, and the cable comprises a body, a shielding layer, and a filter. The shielding layer wraps the body, and the filters are arranged at the two ends of the body; the shielding layer at least comprises an inner shielding net and an outer shielding net, the outer shielding net wraps the inner shielding net, and the inner shielding net wraps the outer side of the body; the filter at least comprises a high-pass filter and a low-pass filter, and the high-pass filter and the low-pass filter are respectively arranged at two ends of the body and are connected with other equipment or cables through a partial discharge test interface. According to the invention, by designing the inner shielding structure of the graphene-plated copper strip and adding the filter, the effects of eliminating interference and improving the measurement signal transmission accuracy are achieved, and the shielding capability of the cable is greatly enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of electric power, and in particular to a shielded cable used for partial discharge detection of electric power equipment. Background Art

[0002] The interference of partial discharge detection of on-site power equipment is mainly electromagnetic wave interference, including electromagnetic waves generated by corona and suspended discharge in high-voltage sites, electromagnetic waves generated by mobile devices such as mobile phones, electromagnetic waves generated by high-power devices such as radar, electromagnetic waves generated by lighting equipment, etc. These electromagnetic waves have different frequency band, power, and time domain characteristics. At present, they are mainly identified by prpd and prps spectra, but these methods are very dependent on the experience and technical analysis level of on-site technicians. Moreover, the more electromagnetic wave interference is superimposed, such as multi-source interference, the more difficult it is to identify and judge. In addition, for similar source interference, taking the main transformer induction withstand voltage and partial discharge measurement test as an example, the high-voltage site is prone to corona interference due to wiring reasons, which affects the partial discharge measured by the pulse current method. Moreover, corona discharge is the same type as the possible tip discharge inside the transformer. It is difficult to identify on-site, which often leads to misjudgment.

[0003] Therefore, for the shielding of electromagnetic wave signals on site, it is extremely necessary to extract the typical waveform inside the tested equipment as much as possible. According to the principle of electrostatic shielding, only by arranging a metal fully enclosed shell around the signal transmission cable as much as possible can the shielding field be guaranteed. Summary of the invention

[0004] The purpose of the present invention is to provide a shielded cable for partial discharge detection of power equipment, so as to solve the technical problem of how to enhance the shielding capability of the cable.

[0005] On the one hand, a shielded cable for partial discharge detection of power equipment is provided, comprising:

[0006] A body, a shielding layer and a filter; the shielding layer is wrapped outside the body, and the filter is arranged at two ends of the body;

[0007] The shielding layer at least comprises an inner shielding net and an outer shielding net, wherein the outer shielding net is wrapped around the inner shielding net, and the inner shielding net is wrapped around the outer side of the body;

[0008] The filter at least includes a high-pass filter and a low-pass filter, and the high-pass filter and the low-pass filter are respectively arranged at two ends of the body and connected to other devices or cables through a partial discharge test interface.

[0009] Preferably, the inner shielding mesh is a copper tape braided layer, and a shielding plating layer is provided on the surface of the inner shielding mesh.

[0010] Preferably, the outer shielding mesh is a copper wire braided layer, and a shielding plating layer is provided on the surface of the outer shielding mesh.

[0011] Preferably, the body at least comprises a wire core and an insulating layer; the insulating layer is arranged between the wire core and the inner shielding mesh, and a shielding coating is also arranged on the surface of the wire core.

[0012] Preferably, the high-pass filter includes at least any one of a first-order high-pass filter, a second-order high-pass filter, a multi-order high-pass filter, an LC high-pass filter and a composite high-pass filter.

[0013] Preferably, it also includes a protective layer, wherein the protective layer is wrapped around the outside of the shielding layer.

[0014] Preferably, the shielding coating at least includes a graphene coating.

[0015] In summary, the implementation of the embodiments of the present invention has the following beneficial effects:

[0016] The shielded cable for partial discharge detection of power equipment provided by the present invention eliminates interference and improves the accuracy of measurement signal transmission by designing an inner shielding structure with a graphene-plated copper tape and adding a filter, thereby greatly enhancing the shielding capability of the cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying creative labor, other drawings obtained based on these drawings still belong to the scope of the present invention.

[0018] Figure 1 The figure is a schematic diagram of a shielded cable used for partial discharge detection of power equipment in an embodiment of the present invention.

[0019] Figure 2 The figure is a schematic diagram of a shielded cable used for partial discharge detection of power equipment in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0021] like Figure 1 and Figure 2 FIG. 1 is a schematic diagram of an embodiment of a shielded cable for partial discharge detection of power equipment provided by the present invention. In this embodiment, it includes:

[0022] The main body, the shielding layer and the filter 6; the shielding layer is wrapped outside the main body, and the filter 6 is arranged at both ends of the main body; the shielding layer at least includes an inner shielding net 3 and an outer shielding net 4, the outer shielding net 4 is wrapped outside the inner shielding net 3, and the inner shielding net 3 is wrapped outside the main body; the filter 6 at least includes a high-pass filter and a low-pass filter 6, the high-pass filter and the low-pass filter 6 are respectively arranged at both ends of the main body, and connected with other devices or cables through a partial discharge test interface 7. It also includes a protective layer 5, which is wrapped outside the shielding layer. It is understandable that the shielding material of the traditional coaxial cable is iron mesh. According to the field application effect, the electromagnetic shielding effect is not good. The shielding effect of materials such as graphene is much greater than that of iron mesh. Therefore, the inner shielding layer of the coaxial cable will use graphene-plated copper tape; due to the complex electromagnetic environment of the substation, there are many noise sources and large signals. For weak signals such as partial discharge, the electromagnetic shielding ability required by the detection cable is strong. Therefore, it is necessary to wrap a layer of shielding net on the outer layer of the cable. According to the Gaussian principle, this can greatly enhance the shielding ability of the cable. In the coaxial cable, its inner shielding layer will use graphene-plated copper tape, and a double-layer shielding layer is set. In addition, in order to simulate the selection of the filter 6, it is necessary to realize the high-pass filtering and low-pass filtering functions, and the high-pass filter and the low-pass filter 6 are connected at both ends of the cable.

[0023] In one embodiment, the inner shielding net 3 is a copper tape braided layer, and a shielding coating is disposed on the surface of the inner shielding net 3. The outer shielding net 4 is a copper wire braided layer, and a shielding coating is disposed on the surface of the outer shielding net 4.

[0024] In one embodiment, the body at least includes a core 1 and an insulating layer 2; the insulating layer 2 is arranged between the core 1 and the inner shielding net 3, and a shielding coating is also arranged on the surface of the core 1. The shielding coating at least includes a graphene coating. Traditional shielding materials have poor shielding effects and are not suitable for measuring weak signals such as partial discharge; according to technical experience in the military field, the shielding effect of materials such as graphene is much greater than that of iron nets, so the inner shielding layer of the coaxial cable developed in this project will use graphene-plated copper tape.

[0025] In one embodiment, the high-pass filter includes at least one of a first-order high-pass filter, a second-order high-pass filter, a multi-order high-pass filter, an LC high-pass filter and a composite high-pass filter. It is understandable that the high-pass filtering and low-pass filtering functions need to be realized, while ensuring the matching resistance of 50Ω, and the high-pass filter and the low-pass filter are connected at both ends of the cable.

[0026] The working principle of passive high-pass filter is mainly based on the frequency response characteristics of capacitors and inductors. Capacitors and inductors have different impedance characteristics for signals of different frequencies: the impedance of capacitors decreases as the frequency increases, while the impedance of inductors increases as the frequency increases.

[0027] In a passive high-pass filter, these components are cleverly combined to achieve the selective passage or suppression of different frequency signals. Specifically, when the input signal contains multiple frequency components: when a low-frequency signal passes through the filter, since the impedance of the capacitor is relatively large (for low-frequency signals), most of the energy will be absorbed or reflected by the capacitor, so the low-frequency signal is attenuated or prevented from passing.

[0028] When a high-frequency signal passes through the filter, the impedance of the capacitor is small and the signal can pass more smoothly; at the same time, the impedance of the inductor to the high-frequency signal is also small, further promoting the passage of the high-frequency signal.

[0029] Therefore, the passive high-pass filter can amplify and transmit high-frequency signals while suppressing the passage of low-frequency signals. In addition, the passive high-pass filter also has a certain phase delay characteristic. Since the capacitor and inductor have different effects on the phase of the signal, when the signal passes through the filter 6, its phase will be shifted to a certain extent. This phase delay characteristic may require special attention in some applications.

[0030] Passive high-pass filters can be divided into many types according to their circuit structure and component combination, including first-order high-pass filters, second-order high-pass filters, multi-order high-pass filters, LC high-pass filters and composite high-pass filters. The following is a brief description of several common types: First-order high-pass filter, circuit structure: composed of a capacitor and a resistor in series. Features: It has a wide passband and a gentle roll-off characteristic, suitable for occasions with low frequency selectivity requirements or wide signal bandwidth. However, due to its slow roll-off slope, the suppression effect on low-frequency signals is relatively weak.

[0031] Second-order high-pass filter, circuit structure: An inductor or capacitor element is added to the first-order high-pass filter to form a more complex circuit structure. Features: It has a steeper roll-off characteristic and stronger low-frequency suppression ability, suitable for occasions with high frequency selectivity requirements or better suppression of low-frequency noise. However, the design of the second-order high-pass filter is relatively complex and may introduce additional phase delay and distortion.

[0032] LC high-pass filter, circuit structure: composed of inductor and capacitor in series. Features: using the resonant characteristics of inductor and capacitor to amplify and transmit high-frequency signals, while suppressing the passage of low-frequency signals. It has the advantages of simple structure, convenient design, and low cost, and has been widely used in many applications. However, its frequency selectivity is relatively limited, and may be limited by the volume and weight of the inductor component.

[0033] In summary, the implementation of the embodiments of the present invention has the following beneficial effects:

[0034] The shielded cable for partial discharge detection of power equipment provided by the present invention eliminates interference and improves the accuracy of measurement signal transmission by designing an inner shielding structure with a graphene-plated copper tape and adding a filter, thereby greatly enhancing the shielding capability of the cable.

[0035] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A shielded cable for partial discharge detection of power equipment, characterized in that: include: A body, a shielding layer and a filter; the shielding layer is wrapped outside the body, and the filter is arranged at two ends of the body; The shielding layer at least comprises an inner shielding net and an outer shielding net, wherein the outer shielding net is wrapped around the inner shielding net, and the inner shielding net is wrapped around the outer side of the body; The filter at least includes a high-pass filter and a low-pass filter, and the high-pass filter and the low-pass filter are respectively arranged at two ends of the body and connected to other devices or cables through a partial discharge test interface.

2. The shielded cable according to claim 1, characterized in that The inner shielding mesh is a copper tape braided layer, and a shielding plating layer is arranged on the surface of the inner shielding mesh.

3. The shielded cable according to claim 2, characterized in that The outer shielding mesh is a copper wire braided layer, and a shielding plating layer is arranged on the surface of the outer shielding mesh.

4. The shielded cable according to claim 3, characterized in that The body at least comprises a wire core and an insulating layer; the insulating layer is arranged between the wire core and the inner shielding net, and a shielding coating is also arranged on the surface of the wire core.

5. The shielded cable according to claim 4, characterized in that The high-pass filter includes at least any one of a first-order high-pass filter, a second-order high-pass filter, a multi-order high-pass filter, an LC high-pass filter and a composite high-pass filter.

6. The shielded cable according to claim 1, characterized in that It also includes a protective layer, which is wrapped around the outside of the shielding layer.

7. The shielded cable according to claim 5, characterized in that The shielding coating at least includes a graphene coating.

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