阅读说明：本技术 一种局部放电脉冲电流超宽频带检测用耦合装置 (Coupling device for detecting local discharge pulse current ultra wide band ) 是由 司文荣 关宏 姚维强 傅晨钊 徐琴 倪鹤立 于 2021-09-30 设计创作，主要内容包括：本发明涉及一种局部放电脉冲电流超宽频带检测用耦合装置,包括同轴电缆输出终端、同轴电缆输入终端、前金属封盖、后金属封盖、第一绝缘支架、第二绝缘支架、无感电阻Rd、第一匹配电阻、第二匹配电阻、过电压保护器、金属圆筒和接地端；同轴电缆输出终端安装在前金属封盖上,并分别与无感电阻Rd、第一匹配电阻、第二匹配电阻、过电压保护器连接；同轴电缆输入终端安装在后金属封盖,并分别与第一匹配电阻、第二匹配电阻连接；无感电阻Rd分别与第一绝缘支架、第二绝缘支架固定连接；金属圆筒分别与前金属封盖、后金属封盖紧密装配,并与接地端连接。与现有技术相比,本发明具有能够用于纳秒级的频率响应需求等优点。(The invention relates to a coupling device for detecting a local discharge pulse current ultra-wide band, which comprises a coaxial cable output terminal, a coaxial cable input terminal, a front metal sealing cover, a rear metal sealing cover, a first insulating support, a second insulating support, a non-inductive resistor Rd, a first matching resistor, a second matching resistor, an overvoltage protector, a metal cylinder and a grounding end, wherein the coaxial cable output terminal is connected with the coaxial cable input terminal; the coaxial cable output terminal is arranged on the front metal sealing cover and is respectively connected with the non-inductive resistor Rd, the first matching resistor, the second matching resistor and the overvoltage protector; the coaxial cable input terminal is arranged on the rear metal sealing cover and is respectively connected with the first matching resistor and the second matching resistor; the non-inductive resistor Rd is respectively and fixedly connected with the first insulating support and the second insulating support; the metal cylinder is tightly assembled with the front metal sealing cover and the rear metal sealing cover respectively and is connected with the grounding terminal. Compared with the prior art, the method has the advantages of being capable of meeting nanosecond-level frequency response requirements and the like.)

1. A coupling device for detecting local discharge pulse current ultra wide band is characterized by comprising a coaxial cable output terminal (1), a coaxial cable input terminal (2), a front metal sealing cover (3), a rear metal sealing cover (4), a first insulating support (5), a second insulating support (6), a non-inductive resistor Rd, a first matching resistor (7), a second matching resistor (8), an overvoltage protector (9), a metal cylinder (10) and a grounding end (11);

the coaxial cable output terminal (1) is arranged on the front metal sealing cover (3) and is respectively connected with the noninductive resistor Rd, the first matching resistor (7), the second matching resistor (8) and the overvoltage protector (9);

the coaxial cable input terminal (2) is arranged on the rear metal sealing cover (4) and is respectively connected with the first matching resistor (7) and the second matching resistor (8);

the noninductive resistor Rd is respectively and fixedly connected with the first insulating support (5) and the second insulating support (6);

the metal cylinder (10) is tightly assembled with the front metal sealing cover (3) and the rear metal sealing cover (4) respectively and is connected with the grounding end (11).

2. The coupling device for detecting the local discharge pulse current ultra-wide band according to claim 1, wherein the coaxial cable output terminal (1) and the coaxial cable input terminal (2) are provided with coaxial cable connectors of a screw connection or a bayonet mechanism.

3. The coupling device for detecting the local discharge pulse current ultra wide band as claimed in claim 1, wherein the front metal cover (3) and the rear metal cover (4) are both metal round plates processed with external threads, and are respectively tightly assembled with the internal threads of the metal cylinder (10) to form an anti-electromagnetic interference faraday cage after the front and rear integrated plugging is completed.

4. The coupling device for detecting the local discharge pulse current ultra wide band as claimed in claim 1, wherein the front metal cover (3) and the coaxial cable output terminal (1) are rigidly connected through metal screws, and the rear metal cover (4) and the coaxial cable output terminal (1) are rigidly connected through metal screws.

5. The coupling device for detecting the local discharge pulse current ultra wide band as claimed in claim 1, wherein the first insulating support (5) and the second insulating support (6) both adopt a central axis symmetric circular hole structure, a non-inductive resistor Rd is fixed in the circular hole and is bonded through epoxy resin solid glue, and the non-inductive resistor Rd on the same insulating support circular hole realizes respective parallel connection of the head end and the tail end based on a copper sheet, so that the inductance component in the non-inductive resistor formed after parallel connection is reduced by times.

6. The coupling device for detecting the local discharge pulse current ultra wide band according to claim 1, wherein the non-inductive resistor Rd is a wire-wound non-inductive resistor comprising a tinned copper wire, a copper cap, a copper wire with an insulating layer, a high thermal conductivity ceramic core and a flame retardant insulating coating.

7. The coupling device for detecting the local discharge pulse current ultra wide band as claimed in claim 1, wherein the first matching resistor (7) and the second matching resistor (8) are both metal film type non-inductive resistors, wherein the resistance of the first matching resistor (7) is 50 Ω, and the resistance of the second matching resistor (8) is 75 Ω.

8. The coupling device for detecting the local discharge pulse current ultra wide band as claimed in claim 1, wherein said overvoltage protector (9) is a bidirectional varistor.

9. The coupling device for detecting the local discharge pulse current ultra wide band as claimed in claim 1, wherein the metal cylinder (10) is provided with internal threads at both ends for tightly fitting with a metal cover.

10. The coupling device for detecting the local discharge pulse current ultra wide band as claimed in claim 1, wherein the grounding terminal (11) is a bolt and a matching nut which are reliably connected with the metal cylinder (10) in a metallic manner.

Technical Field

The invention relates to partial discharge measuring equipment, in particular to a coupling device for detecting partial discharge pulse current ultra-wide frequency bands.

Background

According to the accumulated experience of many years on site, the difficulty level of the current transformer alternating current withstand voltage Partial Discharge (PD) test is ranked as follows: factory test (easiest) < new station building test < in-service substation test < in-service converter station test (hardest). In view of the above common problems, there is an urgent need to explore and develop new PD smart detection technology research and engineering applications as a supplement to the existing technical standards. GB/T7354 version 2018 mentions "ultra wide band" partial discharge meters, but no suggestion for this type of approach is made due to lack of experimental research and engineering applications.

The pulse current method is the only PD detection method with national standard (GB/T7354), and the method measures transient pulse current caused by PD through the modes of series connection of a coupling device and a coupling capacitor, series connection of a test article and the like, and obtains information such as apparent discharge capacity, discharge phase, discharge frequency and the like. The pulse current method has the advantages of simple wiring, high detection sensitivity and most extensive application, is the detection method researched at the earliest time, and the pulse waveform output by the coupler device is easy to distinguish. Fig. 1(a) to 1(c) show examples of a detection circuit commonly used in a pulse current PD test.

At present, the coupling device mainly meets the requirements of a GB/T7354 regulation pulse current method on broadband detection and narrow-band detection, wherein the lower limit detection frequency f1 of the broadband detection is between 30kHz and 100kHz, the upper limit detection frequency f2 is not more than 1MHz, the width of a detection frequency band delta f is between 100kHz and 900kHz, and the coupling device has the advantages of high pulse resolution and relatively rich information, but has low signal-to-noise ratio; the narrow-band detection has a small frequency bandwidth delta f, generally 9kHz-30kHz, and a center frequency fm of 50kHz-1MHz, and has the advantages of high sensitivity and strong anti-interference capability, but has the defects of low pulse resolution and insufficient information.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a coupling device for detecting the local discharge pulse current ultra-wide band.

The purpose of the invention can be realized by the following technical scheme:

a coupling device for detecting local discharge pulse current ultra-wide band comprises a coaxial cable output terminal, a coaxial cable input terminal, a front metal sealing cover, a rear metal sealing cover, a first insulating support, a second insulating support, a non-inductive resistor Rd, a first matching resistor, a second matching resistor, an overvoltage protector, a metal cylinder and a grounding end;

the coaxial cable output terminal is arranged on the front metal sealing cover and is respectively connected with the non-inductive resistor Rd, the first matching resistor, the second matching resistor and the overvoltage protector;

the coaxial cable input terminal is arranged on the rear metal sealing cover and is respectively connected with the first matching resistor and the second matching resistor;

the non-inductive resistor Rd is respectively and fixedly connected with the first insulating support and the second insulating support;

the metal cylinder is tightly assembled with the front metal sealing cover and the rear metal sealing cover respectively and is connected with the grounding terminal.

Preferably, the coaxial cable output terminal and the coaxial cable input terminal are provided with coaxial cable connectors of a threaded connection or a bayonet mechanism.

Preferably, the front metal sealing cover and the rear metal sealing cover are both metal round plates processed with external threads, and are respectively and tightly assembled with the internal threads of the metal cylinder to form the anti-electromagnetic interference Faraday cage after the front and rear integrated plugging is completed.

Preferably, the front metal sealing cover and the coaxial cable output terminal are rigidly connected through metal screws, and the rear metal sealing cover and the coaxial cable output terminal are rigidly connected through metal screws.

Preferably, the first insulating support and the second insulating support are both of a central axis symmetric round hole structure, the noninductive resistor Rd is fixed in the round hole and bonded through epoxy resin solid glue, the noninductive resistor Rd on the round hole of the same insulating support is connected in parallel with the head end and the tail end of the same insulating support respectively based on the copper sheet, and therefore inductance components in the noninductive resistor formed after the parallel connection are reduced in a multiplied mode.

Preferably, the non-inductive resistor Rd is a wire-wound non-inductive resistor, and comprises a tinned copper wire, a copper cap, a copper wire with an insulating layer, a high-thermal-conductivity ceramic core and a flame-retardant insulating coating layer.

Preferably, the first matching resistor and the second matching resistor are both metal film type non-inductive resistors, wherein the resistance value of the first matching resistor is 50 Ω, and the resistance value of the second matching resistor is 75 Ω.

Preferably, the overvoltage protector is a bidirectional voltage dependent resistor.

Preferably, the two ends of the metal cylinder are provided with internal threads which are tightly assembled with the metal sealing cover.

Preferably, the grounding terminal is a bolt and a matched nut which are reliably connected with the metal cylinder in a metallic mode.

Compared with the prior art, the invention has the following advantages:

1. the central axis symmetric type circular hole distribution of the sampling insulation support conveniently and simply realizes the configuration of any resistance value of the coupling device under the non-inductive condition, for example, 8 wire-wound non-inductive resistors (the short-time current capacity is 50A) with the resistance value of 800 omega can be connected in parallel to form the coupling device with the resistance value of 100 omega, the short-time current capacity of 400A is achieved, and the inductance value is reduced to 1/8tongliu of a single wire-wound non-inductive resistor.

2. Two signal output terminals with matching resistors of 50 omega and 75 omega are designed, so that the convenient butt joint of the measuring cable of an actual test loop with impedance of 50 omega or 75 omega is met.

3. The coupling device has the advantages of simple structure, convenience in manufacturing and assembling and high frequency response, and can meet the ns-level (hundred MHz-level) frequency response requirement of PD ultra-wideband pulse current detection.

Drawings

FIG. 1(a) is a schematic diagram of a coupling device in series with a coupling capacitor;

FIG. 1(b) is a schematic diagram of a coupling device connected in series with a sample;

FIG. 1(c) is a schematic view of a test article for measuring self-excitation;

FIG. 2 is a block diagram of a coupling device for detecting an ultra-wideband of local discharge pulse current according to the present invention;

FIG. 3 is a schematic diagram of the operation of the coupling device of the present invention;

FIG. 4 is a schematic view of an insulating support in the coupling device of the present invention;

FIG. 5 is a schematic diagram of a wire wound non-inductive resistor according to the present invention;

FIG. 6 is a frequency response calibration test loop diagram of the coupling device of the present invention;

FIG. 7 is a graph showing the first frequency response test result of the coupling device of the present invention;

FIG. 8 is a second graph of the frequency response test results of the coupling device of the present invention;

FIG. 9 is a diagram showing the test result of the oiled paper insulation defect PD (sharp plate discharge) of the coupling device of the present invention under a negative DC withstand voltage test;

FIG. 10 is a diagram showing the test result of the paper-oil insulation defect PD (air gap discharge) of the coupling device of the present invention under the negative DC withstand voltage test;

FIG. 11 is a diagram showing the test result of the paper-oil insulation defect PD (creeping discharge) of the coupling device of the present invention under the negative DC withstand voltage test;

FIG. 12 is a diagram showing the test result of the paper-oil insulation defect PD (suspension discharge) of the coupling device of the present invention under a negative DC withstand voltage test;

wherein U in FIG. 1 is a high voltage power supply; z is a filter; c_aThe sample is taken as a test sample; c_kIs a coupling capacitor; z_miTo measure the input impedance of the system; CD is a coupling device; CC is a connecting cable; MI is a measuring instrument; OL is an optical connection

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, shall fall within the scope of protection of the present invention.

The invention provides a coupling device for detecting a local discharge pulse current ultra-wide band, which can be used for the frequency response requirement of nanosecond (hundred MHz), so that a novel coupling device is provided for the development of an ultra-wide band local discharge measuring instrument mentioned in version 2018 GB/T7354.

As shown in fig. 2, a coupling device for detecting a local discharge pulse current ultra wide band comprises a coaxial cable output terminal 1, a coaxial cable input terminal 2, a front metal sealing cover 3, a rear metal sealing cover 4, a first insulating support 5, a second insulating support 6, a non-inductive resistor Rd, a first matching resistor 7, a second matching resistor 8, an overvoltage protector 9, a metal cylinder 10 and a grounding end 11; the coaxial cable output terminal 1 is arranged on the front metal sealing cover 3 and is respectively connected with the noninductive resistor Rd, the first matching resistor 7, the second matching resistor 8 and the overvoltage protector 9; the coaxial cable input terminal 2 is arranged on the rear metal sealing cover 4 and is respectively connected with the first matching resistor 7 and the second matching resistor 8; the non-inductive resistor Rd is respectively and fixedly connected with the first insulating bracket 5 and the second insulating bracket 6; the metal cylinder 10 is tightly assembled with the front metal cover 3 and the rear metal cover 4 respectively, and is connected with the grounding terminal 11.

The coaxial cable output terminal 1 and the coaxial cable input terminal 2 are provided with coaxial cable connectors of threaded connection or bayonet mechanism, and can be configured as BNC female connectors;

the front metal sealing cover 3 and the rear metal sealing cover 4 are metal round plates processed with external threads, and are respectively tightly assembled with the internal threads of the metal cylinder 10 to form an anti-electromagnetic interference Faraday cage after the front and rear integrated plugging is completed. The front metal sealing cover 3 and the coaxial cable output terminal 1 and the rear metal sealing cover 4 and the coaxial cable output terminal 1 are rigidly connected through metal screws. The shielding layer of the coaxial cable terminal, i.e. the signal ground, is conducted to the metal cover so as to be grounded to the grounding end of the metal cylinder.

As shown in fig. 4, the first insulating support 5 and the second insulating support 6 both adopt a central axis symmetric circular hole structure, a non-inductive resistor Rd is fixed in the circular hole, and is bonded by epoxy resin solid glue to prevent movement, the non-inductive resistor Rd on the same insulating support circular hole is respectively connected in parallel at the head end and the tail end based on a copper sheet, so that the inductance component (the number n of Rd) in the non-inductive resistor formed after parallel connection is reduced by multiple times, and broadband response of the coupling device is realized; the parallel structure can further reduce the inductance component in the non-inductive resistor, thereby improving the frequency response characteristic of the coupling device.

The non-inductive resistor Rd is a wire-wound non-inductive resistor and comprises a tinned copper wire, a copper cap, a copper wire with an insulating layer, a high-thermal-conductivity ceramic core and a flame-retardant insulating coating layer.

The first matching resistor 7 and the second matching resistor 8 are both metal film type non-inductive resistors, wherein the resistance value of the first matching resistor 7 is 50 omega, and the resistance value of the second matching resistor 8 is 75 omega, so that matching is performed by conveniently or meeting the requirement of measuring the cable impedance of an actual test loop.

The overvoltage protector 9 is a bidirectional voltage dependent resistor. The protection device is used for protecting a data acquisition device (an acquisition instrument, an oscilloscope and the like) connected with the signal output of the coupling device by overvoltage generated by breakdown of a test article or potential rise under other working conditions. Internal threads are machined at two ends of the metal cylinder 10 and are tightly assembled with the metal sealing cover to form the electromagnetic interference resistant Faraday cage. The grounding end 11 is a bolt and a matched nut which are reliably connected with the metal cylinder 10 in a metal manner, so that the grounding end is conveniently and reliably connected with and disassembled from a grounding wire.

Fig. 6 is a diagram of a frequency response verification test loop for a coupling device. A square wave signal generator with a nanosecond (ns) grade falling edge, namely a square wave source, is used as signal input, a coaxial cable is used for being in butt joint with the input end of the coupling device, and meanwhile a high-speed oscilloscope is used for measuring the output end response signal of the coupling device.

Fig. 7 and 8 are graphs showing the results of frequency response testing of the coupling device. The recording parameters of the high-speed oscilloscope are set to be 2.5GS/s sampling rate and 500MHz analog bandwidth. The non-inductive resistor configuration mode of the coupling device adopts 4 wire-wound non-inductive resistors (the short-time current capacity is 50A) with the resistance value of 400 omega to be connected in parallel to form the coupling device with the resistance value of 100 omega, and the coupling device has the short-time current capacity of 200A; and a measuring cable with impedance of 50 omega is connected with the high-speed oscilloscope after being butted with the matching resistor 1. Fig. 7 and 8 show the time domain waveform comparison of the steep falling edge signal of a square wave source with the signal after passing through the coupling means. In the original diagram of fig. 7, the signal with the large amplitude is a square wave source signal, and the signal with the small amplitude is a signal obtained by the coupling device; fig. 8 is a graph showing the normalized amplitude. It can be seen that the high speed oscilloscope measures the falling edge of the square wave source <1ns, while the falling edge after passing through the coupling device is also <1ns, compared to a slight increase in the falling edge. The waveform has no overshoot and oscillation phenomena, and the weak oscillation existing in comparison with the waveforms in fig. 7 and 8 is of the square wave source signal itself. Accordingly, it can be concluded that the performance of the coupling device is such that it meets the use requirements for PD ultra-wideband pulse current waveform measurement.

Fig. 9-12 are graphs showing the test results of the oiled paper insulation defect PD of the coupling device under the negative polarity dc withstand voltage test. It can be seen that the PD ultra-wideband pulse current waveforms under the sharp plate discharge, the air gap discharge, the creeping discharge and the floating discharge all have ns-level rising edges.

While the invention has been described with reference to specific embodiments, the invention is not limited thereto, and various equivalent modifications and substitutions can be easily made by those skilled in the art within the technical scope of the invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.