CN103713242A - Novel ultrahigh frequency sensor for positioning local discharge source space and array thereof - Google Patents

Abstract

The invention provides a novel ultrahigh frequency sensor for positioning a local discharge source space and an array of the novel ultrahigh frequency sensors. The novel ultrahigh frequency sensor comprises a spherical-conical monopole 1, an insulating supporting piece 2, a grounding metal disk 3 and an N-type connector 5 and further comprises short connecting pillars, wherein the spherical-conical monopole 1, the insulating supporting piece 2, the grounding metal disk 3 and the N-type connector 5 are sequentially connected and coaxially arranged. The two short connecting pillars 4 perpendicular to the grounding metal disk 3 are arranged on the bottom edge of a cone of the spherical-conical monopole 1, the two ends of each short connecting pillar 4 are connected with the bottom edge of the cone and the grounding metal disk 3 respectively, and the central axes of the two short connecting pillars 4 and the central axis of the spherical-conical monopole 1 are located in the same plane. Because the spherical-conical structure is adopted, the novel ultrahigh frequency sensor has the advantages of being wide in frequency band, omnibearing, high in sensitivity, low in standing-wave ratio, good in group delay consistency and the like, the requirement for detecting a discharge source in all directions can be effectively met, the space of the discharge source can be accurately positioned through the ultrahigh frequency sensor array composed of the multiple sensors, and the requirement for positioning the local discharge source space of a transformer substation can be met.

Description

Novel UHF sensor and its array for localization of partial discharge sources

technical field

The invention relates to the field of ultra-high frequency sensing, in particular to a novel ultra-high frequency sensor for spatial positioning of a partial discharge source.

Background technique

The UHF (ultra high frequency, UHF) method has become the focus and hotspot of research in the field of partial discharge detection at home and abroad in the past two decades due to its advantages such as wide coverage, high sensitivity, and the ability to identify and locate discharge sources.

In recent years, Philip Moore and others from the University of Strathclyde in the United Kingdom have proposed the idea of spatial positioning of UHF arrays. Four UHF sensors are used to form a sensing array to realize the detection and spatial positioning of internal discharge sources in the entire substation. Such a system has a simple structure and fully utilizes the advantages of high sensitivity and wide coverage of UHF technology. Compared with the current online monitoring and live detection equipment, it has obvious advantages in terms of economy while meeting the requirements of condition-based maintenance.

The key to successfully realizing the spatial positioning of the discharge source is the UHF sensor. Compared with the conventional UHF sensor, the sensor used for spatial positioning needs to have the characteristics of broadband, low loss, omnidirectional, good group delay stability, and high sensitivity. .

Contents of the invention

Aiming at the defects in the prior art, the object of the present invention is to provide a UHF sensor specially used for spatial positioning. The main body of the sensor adopts a combination of spherical and conical structures, and its performance is adjusted through specific short-connected posts. Both simulation and actual measurement results show that the sensor has excellent performance and can meet the requirements of substation spatial positioning.

According to the present invention, the novel ultra-high frequency sensor for partial discharge source space positioning includes: spherical cone monopole antenna 1, insulating support 2, grounded metal disc 3, shorting post 4, and N-type joint 5;

Spherical cone monopole antenna 1, insulating support 2, grounded metal disc 3, and N-type joint 5 are connected in sequence and coaxially arranged;

Two shorting posts 4 perpendicular to the grounded metal disc 3 are arranged on the bottom edge of the cone of the spherical cone monopole antenna 1, and the two ends of the shorting post 4 are connected to the bottom edge of the cone and the grounded metal disc 3 respectively. The central axis of the shorting post 4 and the central axis of the spherical cone monopole antenna 1 are located in the same plane.

Preferably, the material of the insulating support 2 is epoxy resin.

Preferably, H=7cm, W=14cm, h=0.2cm, wherein, H is the cone height of the spherical cone monopole antenna 1, W is the diameter of the cone bottom surface of the spherical cone monopole antenna 1, and h is the spherical cone monopole antenna The distance from the vertex of the spherical cone to the metal disc is 1.

The UHF sensor array provided according to the present invention includes a plurality of the above-mentioned novel UHF sensors for spatial positioning of partial discharge sources distributed in an array.

Compared with the prior art, the present invention has the following beneficial effects:

Based on the spherical cone monopole antenna theory, the invention designs a novel ultra-high frequency sensor that can be used for spatial positioning of substation partial discharge. The sensor provided by the invention adopts a spherical conical structure, which has the characteristics of wide frequency band, omnidirectional, high sensitivity, low standing wave ratio and good group delay consistency, and can effectively meet the requirements of omnidirectional detection of discharge sources. The UHF sensor array composed of sensors can accurately locate the discharge source in space, and can meet the spatial positioning requirements of the partial discharge source in the substation.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

Fig. 1 is the schematic side view of the UHF sensor provided by the present invention;

Fig. 2 is a schematic top view of the UHF sensor provided by the present invention;

Fig. 3 is the standing wave ratio curve of traditional spherical cone sensor;

Fig. 4 is the standing wave ratio curve of the UHF sensor provided by the present invention;

Fig. 5 is the group delay curve of sensor;

Figure 6 is the simulated calculation of the E-plane (XOZ plane) pattern of the sensor at 600MHz;

Figure 7 is the H plane (XOY plane) direction diagram of the sensor calculated by simulation at 600MHz;

Figure 8 shows the sensitivity _He curve of the sensor.

In the picture:

1 is a spherical cone monopole antenna;

2 is an insulating support;

3 is a grounded metal disc;

4 is a shorting post;

5 is an N-type connector.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

In order to realize the spatial positioning of the discharge source in the substation, the following aspects need to be considered in the design of the UHF sensor used in the sensor array:

1.1 Broadband

PD is a broadband pulse signal, the frequency can be as high as several GHz, and according to the different types of defects, the main frequency components of PD signals are quite different. In order to meet the needs of PD signal detection, UHF sensors need to have a wider frequency band , the operating frequency range of a typical UHF sensor is 500MHz-1500MHz.

1.2 Low reflection loss

When the antenna does not match the feeder, reflection loss will occur. The greater the reflection loss, the lower the efficiency of the antenna. In order to improve the efficiency of the antenna, the power loss is generally required to be less than 10%. Corresponding to this indicator, the standing wave ratio of the antenna is required to be less than 2, that is, the standing wave ratio of the UHF sensor used for space positioning should be less than 2.

1.3 Stable group delay

Group delay reflects the sensor's response to different spectral components of broadband signals. After the wide-band signal is received by the sensor, if the response of the sensor to the various spectral components of the signal differs greatly, it will cause dispersion of the signal and affect the waveform of the detected signal.

For broadband sensors used for partial discharge detection, it is an ideal situation that the group delay is constant. When the stability of the group delay is poor, the rising edge of the partial discharge pulse waveform received by the sensor will be distorted, and it is difficult to obtain a clear rising edge of the pulse. Affects the localization of PD sources. In order to meet the needs of spatial positioning, engineering generally requires the sensor to have better group delay stability, and the fluctuation range is less than 1ns.

1.4 Isotropic

Gain is used to quantitatively describe the concentration degree of electromagnetic wave radiation energy of antenna. According to the reciprocity theorem of antenna, gain reflects the concentration degree of electromagnetic wave energy received by antenna. Definition of UHF sensor gain: the ratio of the square of the electric field intensity generated by the directional antenna and the non-directional antenna in the predetermined direction.

For the UHF sensor used for partial discharge space positioning, it is required to have approximately the same gain characteristics in all directions, that is, isotropy, and the gain of the sensor is close to 0dB.

1.5 high sensitivity

Sensitivity reflects the ability of the sensor to convert the space electric field into a voltage output. The sensitivity _He (f) of the UHF sensor is defined by the following formula:

${\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; V</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula, V(f) is the induced electric potential of the antenna, E(f) is the electric field intensity of the incident electromagnetic wave, and f is the frequency of the incident electromagnetic wave.

Sensitivity is one of the most important parameters of UHF sensors, which directly determines the effectiveness of detection and positioning systems. For this reason, the British NGC company has made clear regulations on the sensitivity of UHF sensors. In the frequency range of 500MHz-1500MHz, the minimum sensitivity of more than 80% of the frequency range is not less than 2mm, and the average sensitivity of the entire frequency range is not less than 6mm.

The design of the UHF sensor is described in detail below.

2.1 The structure and working principle of the sensor

The UHF sensor provided by the present invention is an improved spherical cone antenna, which is mainly composed of a spherical cone monopole antenna, an insulating support, a grounded metal disc, a short-connected post, and a 50-ohm N-type connector. Its model structure is as follows As shown in Figure 1 and Figure 2.

The prototype spherical conical monopole antenna is a broadband omnidirectional antenna, which does not include the shorting post in Figure 1, and its lower limit frequency f _L (corresponding to VSWR≤2) (VSWR, Voltage Standing Wave Ratio, voltage standing wave ratio) can be calculated by the following formula:

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 7.5</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{\mathrm{<span\; class="notranslate">\; 3</span>}}}{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; W</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Among them, h is the distance between the apex of the cone and the grounding disc, a _p is the outer radius of the cone, calculated by the formula (3), b _p is the axis of the spherical cone, and the length is the distance from the point of intersection with a _p to the apex of the spherical cone, W is the diameter of the bottom surface of the cone; the unit of a _p , b _p , h, W is cm, and the unit of f _L is MHz.

The specific dimensions of the spherical cone monopole antenna designed by the present invention are: H=7cm, W=14cm, the material of the sensor insulating support is epoxy resin, h=0.2cm. In the case of not adding a shorting post, according to formula (2), the lower limit operating frequency of the sensor can be calculated as 750MHz.

Adding a shorting post is an effective way to lower the resonant frequency of the sensor and reduce the size of the sensor. For this reason, the present invention adds two symmetrical short-connected columns on the edge of the bottom of the cone during design, thereby obtaining the following characteristics:

- Working frequency bandwidth is 500MHz～2GHz;

-Has near-omnidirectional characteristics;

- Low loss, VSWR less than 2;

- The group delay is stable, and the fluctuation value is between 0.5-1ns;

- High sensitivity, the average value of sensitivity He _is greater than 12mm.

The laboratory discharge source positioning results show that the UHF sensor designed in the present invention can fully meet the needs of substation partial discharge source spatial positioning, as follows.

2.2 Sensor parameter calculation and performance analysis

Figure 3 and Figure 4 are the standing wave ratio curves of the spherical cone sensor, among which, Figure 3 is the standing wave ratio curve of the traditional spherical cone sensor, and Figure 4 is the improved spherical cone sensor, that is, a short-connected column is added. The dotted line in the figure is the standing wave ratio curve obtained by simulation calculation, and the solid line is the standing wave ratio curve obtained by testing with Agilent E5071C network analyzer.

From the simulation and measured standing wave ratio curves in Figure 3 and Figure 4, it can be seen that for the spherical cone sensor, the frequency range corresponding to VSWR less than 2 is 730MHz-2000MHz, and after adding the short-circuit post, the frequency range is extended to 480MHz-2000MHz . It can be seen from formula (2) that for the spherical-cone sensor, when the lower limit frequency is 480MHz, H=10.94cm. In other words, the same lower limit frequency is obtained, and the size of the sensor is reduced by 34.8% by adding a short-circuit post.

It can be seen from Fig. 4 that the bandwidth (VSWR≤2) of the improved spherical-cone sensor provided by the present invention covers the main frequency range of the PD signal energy distribution.

Figure 5 is the group delay curve of the sensor, in which the dotted line is the result obtained from the simulation calculation, and the solid line is the test result of the Agilent E5071C network analyzer.

It can be seen from Figure 5 that the group delay of the sensor is between 0.5-1 ns in the frequency range of 500MHz-2000MHz, which ensures that after the broadband PD pulse is received by the sensor, the signal dispersion is small and a clear pulse rising edge can be obtained.

Figure 6 and Figure 7 are the simulated and calculated directions of the E-plane (XOZ plane) and H-plane (XOY plane) of the sensor at 600MHz respectively.

From the simulation results in Figure 6 and Figure 7, it can be seen that the gain (indicated by the dotted line) of the sensor in the direction of 0-360 degrees on the E-plane and H-plane is close to 0dB, and on the E-plane (XOZ plane) and H-plane (XOY plane) has approximately omnidirectional directional characteristics.

Figure 8 shows the sensitivity _He curve of the sensor. It can be seen from Figure 8 that the average value of sensor sensitivity _He in the frequency range of 500MHz-2000MHz is 12.86mm, and over 80% of the frequency range _He is greater than 2mm, which meets the requirements of the British NGC. Sensitivity requirements for UHF sensors.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (4)

1. a novel local discharge source space orientation superfrequency sensor, is characterized in that, comprising: ball cone unipole antenna (1), insulated support (2), grounded metal disk (3), short circuit post (4), N connector (5);

Ball is bored unipole antenna (1), insulated support (2), grounded metal disk (3), N connector (5) connects successively and coaxially setting;

Conical base edge at ball cone unipole antenna (1) is provided with two perpendicular to the short circuit post (4) of grounded metal disk (3), the two ends of short circuit post (4) connect respectively conical base edge and grounded metal disk (3), and the axis of the axis of these two short circuit posts (4) and ball cone unipole antenna (1) is positioned at same plane.

2. novel local discharge source according to claim 1 space orientation superfrequency sensor, is characterized in that, the material of described insulated support (2) is epoxy resin.

3. novel local discharge source according to claim 1 space orientation superfrequency sensor, it is characterized in that, H=7cm, W=14cm, h=0.2cm, wherein, H is the cone height of ball cone unipole antenna (1), W is the circular cone bottom surface diameter of ball cone unipole antenna (1), and h is that the ball conical point of ball cone unipole antenna (1) is to rosette distance.

4. a superfrequency sensor array, is characterized in that, comprises the novel local discharge source space orientation superfrequency sensor described in any one in the claims 1 to 3 of a plurality of array distribution.

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