CN209927964U - Power cable intermediate head insulation state on-line measuring device - Google Patents
Power cable intermediate head insulation state on-line measuring device Download PDFInfo
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- CN209927964U CN209927964U CN201920565543.6U CN201920565543U CN209927964U CN 209927964 U CN209927964 U CN 209927964U CN 201920565543 U CN201920565543 U CN 201920565543U CN 209927964 U CN209927964 U CN 209927964U
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Abstract
An on-line detection device for the insulation state of a power cable intermediate joint. To power cables. The utility model provides a convenient on-line monitoring, the power cable intermediate head insulation state on-line measuring device who improves the detection progress. The ultrasonic sensor is adhered to the surface of a cable connector through an epoxy resin coupling agent, converts an acquired ultrasonic signal into an electric signal and transmits the electric signal to the conditioning circuit A; the Rogowski coil transmits the acquired electric signal to a conditioning circuit B; the conditioning circuit A and the conditioning circuit B are respectively connected with an A/D conversion module, and the A/D conversion module, the ARM processor, the communication module and the upper computer are sequentially and electrically connected. The utility model provides high work efficiency to avoid the waste time to bring huge economic loss again.
Description
Technical Field
The utility model relates to a power cable especially relates to power cable intermediate head insulating state on-line measuring device.
Background
The power cable intermediate head need strip in proper order and cut cable copper shield layer, cable inner sheath, cable semi-conducting layer, cable main insulation when the encapsulation, then embolia cold contraction formula intermediate head, copper shield net cover, cable connecting pipe that continues, the fixed and shrink of cold contraction head (fixed copper shield net, cover around package sticky tape, winding armoured tape). The power cable intermediate joint is therefore more complex in construction than the cable intermediate section. Meanwhile, due to the existence of potential risks caused by immature personnel and technology, the power cable intermediate joint becomes a weak link of a part where operation faults mainly occur and cable insulation.
According to incomplete statistics, the proportion of operating faults of high voltage cables caused by faults in the cable intermediate joints is as high as 39%. And because the structure is complicated, especially the armor belt plays a role in insulation protection and shields fault signals to a certain extent, the detection is difficult. At present, a conventional electrical detection method is mostly adopted for insulation faults of a power cable intermediate joint, belongs to off-line detection, and has the defects of long overhaul period, large consumption of manpower and material resources and the like. An ultrasonic-based on-line detection method is emerging for overcoming the defect of off-line detection, but most of the existing ultrasonic detection devices are handheld and mobile, and the problem of reflection attenuation of an air medium to ultrasonic waves is not well solved, so that the detection effect is poor.
SUMMERY OF THE UTILITY MODEL
The utility model provides a to above problem, provide a power cable intermediate head insulating state on-line measuring device of convenient on-line monitoring, improvement detection progress.
The utility model adopts the technical proposal that the ultrasonic wave sensor comprises an ultrasonic sensor, a Rogowski coil, a conditioning circuit A, a conditioning circuit B, A/D conversion module, an ARM processor, a communication module and an upper computer,
the ultrasonic sensor is adhered to the surface of the cable joint through an epoxy resin coupling agent, and converts an acquired ultrasonic signal into an electric signal and transmits the electric signal to the conditioning circuit A;
the Rogowski coil is nested on a grounding wire of the cable intermediate joint, and transmits the acquired electric signal to the conditioning circuit B;
the conditioning circuit A and the conditioning circuit B are respectively connected with an A/D conversion module, and the A/D conversion module, the ARM processor, the communication module and the upper computer are sequentially and electrically connected.
The conditioning circuit A comprises a voltage follower A, a primary amplifying circuit A, a band-pass filter circuit A and a secondary amplifying circuit A which are sequentially connected.
The conditioning circuit B comprises a voltage follower B, a primary amplifying circuit B, a band-pass filter circuit B and a secondary amplifying circuit B which are connected in sequence.
The A/D protection and correction circuit is connected with the A/D conversion module.
The Rogowski coil adopts nickel-zinc ferrite as a magnetic core.
The ARM processor adopts STM32F103ZET6 chip.
The communication module adopts an optical fiber model GYXTW-4A1 b.
The utility model judges the partial discharge position by the sound-electricity comprehensive detection method according to the partial discharge characteristic of the power cable joint during insulation fault; the method combines the traditional electric detection method and the non-electric detection method to achieve the purpose of diagnosing whether the insulation state of the cable joint is good or not. The method overcomes the defect that the conventional detection method cannot realize charged on-line detection, and also improves the detection precision. And simultaneously, the utility model discloses to can send various signals when power cable event partial discharge, can disturb wireless signal like the electromagnetic wave, avoid information transmission inaccurate, propose the mode that adopts wired transmission. The sound-electricity comprehensive detection is used for judging the partial discharge position of the power cable intermediate joint, and a convenient, quick and effective method is provided for positioning and detecting the faults of the power cable intermediate joint.
The utility model provides a basis for the on-site and timely treatment of the insulation weak points of the power cable intermediate joint, which can greatly improve the working efficiency of the related operation and maintenance personnel; therefore, the problem that the cable fault is not found timely, which wastes time and brings huge economic loss is avoided.
Drawings
Figure 1 is a system block diagram of the present invention,
figure 2 is a schematic structural diagram of the acoustoelectric conditioning circuit of the present invention,
figure 3 is a circuit diagram of the acousto-electric signal conditioning circuit of the present invention,
figure 4 is a schematic diagram of the detection device of the present invention,
fig. 5 is a sectional view showing the installation distribution of the ultrasonic sensor of the present invention;
in the figure: 1 is an ultrasonic sensor, 2 is a rogowski coil, 3 is a conditioning circuit A, 4 is a conditioning circuit B, 5 is an A/D conversion module, 6 is an ARM processor, 7 is an A/D protection and correction circuit, 8 is a communication module, 9 is an upper computer, 10 is a voltage follower A, 11 is a primary amplification circuit A, 12 is a band-pass filter circuit A, 13 is a secondary amplification circuit A, 14 is a voltage follower B, 15 is a primary amplification circuit B, 16 is a band-pass filter circuit B, and 17 is a secondary amplification circuit B.
Detailed Description
The invention will be further explained with reference to the drawings and the accompanying description. These figures are simplified schematic diagrams and illustrate the basic structure of the invention in a schematic way only.
As shown in fig. 1-5, the ultrasonic sensor comprises an ultrasonic sensor 1, a Rogowski coil 2(Rogowski), an acoustic-electric signal conditioning circuit (namely a conditioning circuit a3 and a conditioning circuit B4), an a/D conversion module 5, an a/D protection and correction circuit 7, an ARM processor 6, a communication module 8 and an upper computer 9; the ultrasonic sensor is adhered to the surface of a cable joint by adopting an epoxy resin coupling agent, and ultrasonic signals generated when the insulation of the cable joint breaks down are collected and converted into electric signals; the Rogowski coil is nested on a grounding wire of a cable intermediate joint, and the fault current of the cable joint is detected; the acoustoelectric signal conditioning circuit, the A/D conversion module, the A/D protection and correction circuit, the ARM processor and the communication module are electrically connected in sequence, and the collected electric signals are amplified, filtered and converted and transmitted to an upper computer through optical fibers. The conditioning circuit A3 comprises a voltage follower A10, a primary amplifying circuit A11, a band-pass filter circuit A12 and a secondary amplifying circuit A13 which are electrically connected in sequence; the conditioning circuit B4 comprises a voltage follower B14, a primary amplifying circuit B15, a band-pass filter circuit B16 and a secondary amplifying circuit B17 which are electrically connected in sequence. The upper computer can display the acquired signals and has an alarm function.
The ultrasonic sensor comprises a metal shell and a piezoelectric body, wherein the piezoelectric body converts a received acoustic signal into an electric signal and outputs the electric signal. The piezoelectric body is made into an arc shape by adopting a method of cutting piezoelectric ceramic and filling organic matters, the curvature can be adjusted according to the cutting depth, the bottom of the metal shell of the ultrasonic sensor also forms a concave curved surface, and the bottom of the metal shell is tightly attached to the surface of the cable joint by using epoxy resin. The used ultrasonic sensors are 4 in total and are distributed in pairwise symmetry. Each ultrasonic sensor generates an electrical signal having a separate conditioning circuit a (3).
The Rogowski coil uses nickel-zinc ferrite with the magnetic conductivity of 200 as a magnetic core, the number of winding turns is 10, the resistance value of the self-integration resistor is 1k omega, and the maximum sensitivity is 40 dB.
The ARM processor adopts STM32F103ZET6 chip.
The communication module adopts an optical fiber model GYXTW-4A1 b.
The utility model discloses combine together traditional electric detection technique and emerging non-electric detection technique, detect the ultrasonic wave of cable joint insulation production and change it into the signal of telecommunication through ultrasonic sensor, the electric current size that combines to detect the rogowski coil carries out the integrated analysis to this judges whether cable joint has reached the fault standard, thereby help relevant personnel make the judgement whether overhaul, guarantees electric power system's safe operation.
The operation flow of the detection device is as follows: when the cable joint is insulated and has partial discharge, an acousto-optic electric signal can be emitted, the ultrasonic sensor converts the ultrasonic signal into an electric signal, the electric signal is subjected to noise reduction, filtering and amplification processing by the conditioning circuit A and then is transmitted to the A/D module, the electric signal generated by induction by the Rogowski coil is subjected to noise reduction, filtering and noise reduction processing by the conditioning circuit B and then is transmitted to the A/D module, the signal is controlled and processed by the ARM processor and then is transmitted to the upper computer through the optical fiber for display, and the upper computer has a display interface designed by LabVIEW and can perform sound alarm.
The detection device is mainly divided into four parts: signal detection, signal processing, signal transmission, and signal display.
1 Signal detection
1.1 ultrasonic sensor
The ultrasonic sensor comprises a metal shell and a piezoelectric body, wherein the piezoelectric body converts a received acoustic signal into an electric signal and outputs the electric signal. The piezoelectric body is made into an arc shape by adopting a method of cutting piezoelectric ceramics and filling organic matters, the curvature can be adjusted according to the cutting depth, the arc shape can increase the receiving wide angle of the ultrasonic sensor, and the detection efficiency and precision are improved. The bottom of the metal shell of the ultrasonic sensor is also a concave curved surface and is tightly attached to the surface of the cable joint by epoxy resin. Ultrasonic waves are attenuated, reflected, and the like when propagating through different media. Especially when passing through different media with large differences in acoustic impedance. The utility model discloses the couplant that uses is epoxy, can improve the acoustic impedance matching degree on ultrasonic sensor and cable joint surface, and then improves and detects the precision.
As shown in fig. 5, the number of the ultrasonic sensors used at each power cable joint is 4, and the ultrasonic sensors are symmetrically distributed in pairs. There is a separate conditioning circuit a for each electrical signal generated by the ultrasonic sensor.
1.2 Rogowski coil
As shown in fig. 4, the rogowski coil is installed at a lead of a power cable joint for detecting the magnitude of current generated when a partial discharge occurs at the cable joint.
The partial discharge signal in the power cable joint has the following characteristics: the amplitude is very small, only in the order of muA; the duration is very short, only in the order of ns; the frequency spectrum in the partial discharge signal is broad. Therefore, the coupler for detecting partial discharge of high-voltage cable should satisfy the following requirements: wide working frequency band, good transient response, high sensitivity, good linearity, small output distortion and good working stability.
The utility model discloses the rogowski coil that uses is nickel zinc ferrite that magnetic conductivity is 200 as the magnetic core, and the coiling number of turns is 10 circles, is 1k omega from the integral resistance, and maximum sensitivity is 40 dB.
And the surface of the magnetic ring and the enameled wire are isolated by adopting an insulating tape to prevent crosstalk among the turns of coils. And meanwhile, the coil is wound along the surface of the magnetic ring in a reverse turn so as to counteract the interference of a stray magnetic field vertical to the surface of the magnetic ring. The outermost layer of the Rogowski coil is wrapped by a closed metal shell, so that the Rogowski coil plays roles in water resistance and damage resistance.
2 acoustoelectric signal conditioning circuit
As shown in fig. 3, since the circuits of the conditioning circuit a and the conditioning circuit B are the same, the following is introduced in a unified manner: the conditioning circuit comprises a voltage follower, a primary amplifying circuit, a band-pass filter circuit and a secondary amplifying circuit. Because the rated input voltage of the A/D module is 0-3.3V, and the AC voltage generated by the ultrasonic sensor has a negative half period, 1.5V voltage is added for potential lifting, and a 3.3V voltage stabilizing diode is added at the output end of the circuit, thereby ensuring the operation safety of the A/D module.
2.1 impedance matching
Ultrasonic signals are sometimes weak, and signal energy is attenuated due to reflection, scattering and the like of the signals in the transmission process. Conditioning circuits are needed to reduce the loss of useful signals and to reduce noise interference.
The input impedance of the voltage follower is very large, and the output impedance is very small, so that the voltage follower can be used as an impedance matching circuit of an ultrasonic signal. Due to U+＝U-，Ui＝U+,Uo＝U-So that U iso＝Ui.
2.2 amplifying circuit
The voltage generated by the ultrasonic wave is about 100mv, corresponding amplification treatment is needed to perform better filtering, part of clutter is filtered after filtering, the effective value of the voltage is reduced, and secondary amplification is needed, as shown in fig. 3.
The amplification factor formula of the first-stage operational amplifier is as follows:
the amplification factor formula of the first-stage operational amplifier is as follows:
2.3 band-pass filter circuit
The center frequency of ultrasonic waves generated when partial discharge occurs in the insulation of a power cable joint is about 40KHZ, the bandwidth is 2040KHZ, band-pass filtering is needed for removing ultrasonic noise of other frequencies existing in the environment, the design adopts a two-stage voltage-controlled band-pass filter, and a schematic diagram 3 of the two-stage voltage-controlled band-pass filter is shown in the specification, wherein an operational amplifier U3, R1, R2, R3, R5, C1 and C2 form a second-order voltage-controlled band-pass filter, R5 and C2 form low-pass filtering, and R4 and C2 form high-pass filtering. Voltage positive feedback is introduced by voltage R4, forming a voltage controlled bandpass filter. The transfer function is as follows:
wherein the passband amplification is:
center frequency:
quality factor:
3 Signal processing and Signal Transmission
The utility model discloses a STM32 singlechip carries out signal acquisition and signal processing as the next machine.
The ADC input clock ADC _ CLK of STM32 is generated by APB2 dividing by frequency to a maximum of 14MHz, where the sampling period is 1.5 at a minimum, i.e. if we want to reach the fastest sampling, the sampling period should be set to 1.5 cycles.
Tconv +12.5 cycles of sample time
Where Tconv is the total ADC conversion time, and when ADC _ CLK is 14Mhz, and a sampling time of 1.5 cycles is set, Tcovn is 1.5+12.5 is 14 cycles 1 us.
We need to acquire the center frequency of the ultrasonic signal of 40Khz and the bandwidth of 20DB, so that 200-250 points can be sampled in each signal period when the signal acquisition is performed by using the AD of STM 32.
The design adopts a single-channel sequential sampling mode and adds an ADC median digital filtering technology, so that the conversion result is more effective; the converted signal is transmitted to an upper computer through an optical fiber.
4 upper computer display
An upper computer display interface is designed by applying LabVIEW, and when the collected signal value is larger than a set standard value, the display interface twinkles a red light to prompt relevant personnel to check and maintain.
The utility model discloses a be applied to cable joint insulation fault on-line measuring's device specially, its characteristics have threely: firstly, the device combines a non-electric detection method and a conventional electric detection method, and improves the detection precision and the detection accuracy. The detection device is characterized in that the ultrasonic sensor is adhered to the surface of the cable joint by using epoxy resin, so that the serious attenuation and reflection of an air film to ultrasonic waves are eliminated, the acoustic impedance matching degree is increased, and the detection precision is improved. Third, the ultrasonic sensor that this detection device used, its resonance body and shell are concave curved surface, and the camber can change according to particular case, compares with traditional planar sensor can be inseparabler laminating on the cable joint surface, the ultrasonic signal that produces when the insulating trouble of better receipt transition cable joint.
The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only illustrative of the working principle of the present invention, and that various changes and modifications can be made without departing from the spirit and scope of the present invention, and these changes and modifications are all within the scope of the claimed invention. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (7)
1. The device for detecting the insulation state of the power cable intermediate joint on line is characterized by comprising an ultrasonic sensor (1), a Rogowski coil (2), a conditioning circuit A (3), a conditioning circuit B (4), an A/D conversion module (5), an ARM processor (6), a communication module (8) and an upper computer (9),
the ultrasonic sensor (1) is adhered to the surface of a cable joint through an epoxy resin coupling agent, and the ultrasonic sensor (1) converts acquired ultrasonic signals into electric signals and transmits the electric signals to the conditioning circuit A (3);
the Rogowski coil (2) is nested on a ground wire of a cable middle joint, and the Rogowski coil (2) transmits the acquired electric signal to a conditioning circuit B (4);
the conditioning circuit A (3) and the conditioning circuit B (4) are respectively connected with the A/D conversion module (5), and the A/D conversion module (5), the ARM processor (6), the communication module (8) and the upper computer (9) are sequentially and electrically connected.
2. The on-line detection device for the insulation state of the power cable intermediate joint according to claim 1, wherein the conditioning circuit A (3) comprises a voltage follower A (10), a primary amplification circuit A (11), a band-pass filter circuit A (12) and a secondary amplification circuit A (13) which are connected in sequence.
3. The on-line detection device for the insulation state of the power cable intermediate joint according to claim 1, wherein the conditioning circuit B (4) comprises a voltage follower B (14), a primary amplification circuit B (15), a band-pass filter circuit B (16) and a secondary amplification circuit B (17) which are connected in sequence.
4. The on-line detection device of the insulation state of the middle joint of the power cable according to claim 1, characterized by further comprising an A/D protection and correction circuit (7), wherein the A/D protection and correction circuit (7) is connected with the A/D conversion module (5).
5. The on-line detection device for insulation state of power cable intermediate joint according to claim 1, characterized in that said rogowski coil (2) uses nickel-zinc ferrite as magnetic core.
6. The on-line detection device for the insulation state of the power cable intermediate joint as recited in claim 1, wherein the ARM processor (6) adopts STM32F103ZET6 chip.
7. The device for the on-line detection of the insulation state of the power cable intermediate joint according to claim 1, characterized in that the communication module (8) adopts an optical fiber model GYXTW-4A1 b.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201920565543.6U CN209927964U (en) | 2019-04-23 | 2019-04-23 | Power cable intermediate head insulation state on-line measuring device |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201920565543.6U CN209927964U (en) | 2019-04-23 | 2019-04-23 | Power cable intermediate head insulation state on-line measuring device |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109975674A (en) * | 2019-04-23 | 2019-07-05 | 国网江苏省电力有限公司扬州供电分公司 | A kind of intermediate joint of electric cable state of insulation on-line measuring device |
| CN113138048A (en) * | 2021-03-25 | 2021-07-20 | 四川大学 | Nondestructive live-line detection method for cable joint interface pressure based on stress ultrasound |
-
2019
- 2019-04-23 CN CN201920565543.6U patent/CN209927964U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109975674A (en) * | 2019-04-23 | 2019-07-05 | 国网江苏省电力有限公司扬州供电分公司 | A kind of intermediate joint of electric cable state of insulation on-line measuring device |
| CN113138048A (en) * | 2021-03-25 | 2021-07-20 | 四川大学 | Nondestructive live-line detection method for cable joint interface pressure based on stress ultrasound |
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