Switch cabinet ultrasonic partial discharge signal detection circuit

Abstract

The utility model discloses an ultrasonic partial discharge signal detection circuit for a switch cabinet. The ultrasonic partial discharge signal detection circuit comprises an ultrasonic sensor, a pre-amplification circuit, a filter circuit, a detection circuit and an AD conversion circuit, moreover, through the circuit design of the pre-amplification circuit and the filter circuit and the model selection of components in the detection circuit and the AD conversion circuit, the accuracy and sensitivity of ultrasonic partial discharge signal detection can be improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to electronic circuit technology technical field, especially relates to a switchgear ultrasonic partial discharge signal detection circuit. BACKGROUND

[0002] The high voltage switch cabinet is important switch equipment in distribution network system, for high voltage switch cabinet, need through partial discharge monitoring understands the insulation level of switch cabinet in long -term operation process, once the insulation level reduces, will seriously threaten the safe operation of power system. Figure 1 As shown in the figure, when the partial discharge occurs in the insulation inside the power equipment, the ultrasonic signal is generated at the same time, and the ultrasonic signal is conducted to the power equipment shell along the insulation medium, metal piece or air from the partial discharge source, and is propagated to the surrounding air through the medium and gap. Through the ultrasonic sensor installed on the power equipment shell or the equipment nearby, the ultrasonic signal generated by the partial discharge can be coupled, and then the partial discharge condition of the power equipment is judged. In order to obtain more accurate partial discharge condition, a suitable amplification circuit, filter circuit and other processing circuit need to be designed to process the ultrasonic signal captured by the ultrasonic sensor. SUMMARY

[0003] The utility model discloses the purpose at: provide a switchgear ultrasonic partial discharge signal detection circuit, through the reasonable circuit design and component selection, thereby improve the accuracy and sensitivity of ultrasonic partial discharge signal detection.

[0004] In order to realize the above-mentioned utility model purpose, the utility model provides the following technical scheme:

[0005] A switchgear ultrasonic partial discharge signal detection circuit, it includes: ultrasonic sensor, preamplifier circuit, filter circuit, detection circuit and AD conversion circuit, wherein,

[0006] The preamplifier circuit is electrically connected with the ultrasonic sensor, and is used for amplifying and processing the ultrasonic original signal detected by the ultrasonic sensor;

[0007] The filter circuit is electrically connected with the preamplifier circuit, and is used for filtering the ultrasonic original signal amplified by the preamplifier circuit, to obtain the ultrasonic effective signal;

[0008] The detection circuit is electrically connected with the filter circuit, and is used for peak detection of the ultrasonic effective signal obtained by filtering the filter circuit, to obtain the peak voltage of the ultrasonic effective signal;

[0009] The AD conversion circuit is electrically connected with the detection circuit, and is used for AD conversion of a peak voltage of the ultrasonic effective signal obtained through peak detection processing of the detection circuit, to obtain an ultrasonic digital signal.

[0010] According to a specific embodiment, the switch cabinet ultrasonic partial discharge signal detection circuit provided by the utility model includes: a preamplification circuit, a filter circuit, a detection circuit and an AD conversion circuit.

[0011] According to a specific embodiment, the switch cabinet ultrasonic partial discharge signal detection circuit provided by the utility model includes: the filter circuit is a second-order active band-pass filter circuit, which is composed of an input capacitor, a 100kHz low-pass filter circuit, a 35kHz high-pass filter circuit and an operational amplifier, and the passband of the filter circuit is 65kHz.

[0012] According to a specific embodiment, the switch cabinet ultrasonic partial discharge signal detection circuit provided by the utility model includes: the detection circuit includes an amplifier chip with a model of AD8310ARMZ and a peripheral circuit thereof.

[0013] According to a specific embodiment, the switch cabinet ultrasonic partial discharge signal detection circuit provided by the utility model includes: the AD conversion circuit includes an AD conversion chip with a model of ADS7822U and a peripheral circuit thereof.

[0014] According to a specific embodiment, the switch cabinet ultrasonic partial discharge signal detection circuit provided by the utility model includes a power supply circuit, which is used for providing corresponding power supplies for the ultrasonic sensor, the preamplification circuit, the detection circuit and the AD conversion circuit.

[0015] Therefore, the switch cabinet ultrasonic partial discharge signal detection circuit provided by the utility model includes: an ultrasonic sensor, a preamplification circuit, a filter circuit, a detection circuit and an AD conversion circuit. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a schematic diagram of a partial discharge detection principle based on an ultrasonic sensor.

[0017] Figure 2 The structure schematic view of the switch cabinet ultrasonic partial discharge signal detection circuit is provided in the utility model;

[0018] Figure 3 The circuit diagram of the preamplifier circuit in the utility model;

[0019] Figure 4 The circuit diagram of the filter circuit in the utility model;

[0020] Figure 5 The circuit diagram of the detection circuit in the utility model;

[0021] Figure 6 The circuit diagram of the AD conversion circuit in the utility model;

[0022] Figure 7 The connection schematic view of the power supply for the power supply circuit. DETAILED DESCRIPTION

[0023] The utility model will be described further in detail below in combination with the drawings and specific embodiments. But this should not be understood as the range of the above-mentioned subject matter of the utility model is limited to the following embodiments, and all the technologies realized based on the content of the utility model belong to the range of the utility model.

[0024] As Figure 2 shown, the switch cabinet ultrasonic partial discharge signal detection circuit provided by the utility model comprises an ultrasonic sensor, a preamplifier circuit, a filter circuit, a detection circuit and an AD conversion circuit, wherein,

[0025] The preamamplifier circuit is electrically connected with the ultrasonic sensor and is used for amplifying the ultrasonic original signal detected by the ultrasonic sensor;

[0026] The filter circuit is electrically connected with the preamplifier circuit and is used for filtering the ultrasonic original signal amplified by the preamplifier circuit to obtain an ultrasonic effective signal;

[0027] The detection circuit is electrically connected with the filter circuit and is used for peak detection of the ultrasonic effective signal obtained by filtering of the filter circuit to obtain the peak voltage of the ultrasonic effective signal;

[0028] The AD conversion circuit is electrically connected with the detection circuit and is used for AD conversion of the peak voltage of the ultrasonic effective signal obtained by peak detection of the detection circuit to obtain an ultrasonic digital signal.

[0029] Specifically, as Figure 3As shown, in the ultrasonic partial discharge signal detection circuit for switchgear provided by this utility model, the preamplifier circuit includes: operational amplifier u1, operational amplifier u2, filter capacitor C0, and input impedance R1. One end of the filter capacitor C0 and one end of the input impedance R1 are connected to the signal input terminal of the preamplifier circuit. The other end of the filter capacitor C0 is grounded. The other end of the input impedance R1 is connected to the non-inverting input terminal of the operational amplifier u1. The output terminal of the operational amplifier u1 is connected to the non-inverting input terminal of the operational amplifier u2. The output terminal of the operational amplifier u2 is connected to the signal output terminal of the preamplifier circuit.

[0030] During implementation, the main frequency of the original ultrasonic signal generated by partial discharge can reach several 35kHz to 100kHz, while the maximum amplitude does not exceed 100mV. To ensure measurement accuracy and sensitivity, the original ultrasonic signal is first amplified, taking into account the signal bandwidth. Therefore, the amplifier U1 model is selected as OPA846, which has extremely high gain bandwidth, extremely low input voltage noise, high DC accuracy, and extremely low distortion amplification characteristics. Moreover, the amplification factor of amplifier U1 is: A = 1 + R2 / R3 (the resistance value can be changed according to the amplification factor requirements). Based on the ultrasonic detection principle, the filter capacitor C0 should be minimized as much as possible to filter out high-frequency noise. To avoid wave reflection, the input impedance is matched to 50Ω.

[0031] like Figure 4 As shown, in the ultrasonic partial discharge signal detection circuit for switchgear provided by this utility model, the filtering circuit is a second-order active bandpass filter circuit, which consists of an input capacitor, a 100kHz low-pass filter circuit, a 35kHz high-pass filter circuit, and a cascaded operational amplifier.

[0032] During implementation, given that the frequency of the ultrasonic signal is known to be between 35kHz and 100kHz, a bandpass filter was selected. The upper cutoff frequency is 100kHz, the lower cutoff frequency is 35kHz, the passband is 65kHz, and the filter bandwidth is chosen to be between 35kHz and 100kHz. This effectively suppresses high-frequency or low-frequency interference signals outside the ultrasonic signal bandwidth. Simultaneously, the active filter has strong anti-interference capabilities, can compensate for signal attenuation during the filtering process, facilitates gain adjustment, and can achieve a higher Q value and a steeper crossover point.

[0033] like Figure 5As shown in the utility model provides a switchgear ultrasonic partial discharge signal detection circuit, the detection circuit includes: logarithmic amplifier chip u4 and its peripheral circuit, in implementation, logarithmic amplifier chip u2 model is AD8310ARMZ, it has excellent common mode rejection (70dB (10MHz)) performance, wide voltage input range, and is logarithmic detection, dynamic range is big, can satisfy the amplitude change of ultrasonic signal, avoid easy saturation.

[0034] As Figure 6 As shown in the utility model provides a switchgear ultrasonic partial discharge signal detection circuit, the AD conversion circuit includes: AD conversion chip u5 and its peripheral circuit, AD conversion chip u5 model is ADS7822U, the highest sampling frequency is 200kHz, wide dynamic range, 12 bit AD output, micro power consumption, can fully satisfy the sampling needs of ultrasonic signal.

[0035] As Figure 7 As shown in the utility model provides a switchgear ultrasonic partial discharge signal detection circuit, and the power supply circuit is used to provide corresponding power supply for the ultrasonic sensor, the preamplifier circuit, the detection circuit and the AD conversion circuit.

[0036] In implementation, the utility model provides a switchgear ultrasonic partial discharge signal detection circuit, and the power supply circuit can provide stable 5V voltage, selects SPX3819 to do power management chip, and noise is low, precision is high and power consumption is low, wherein, switchgear ultrasonic partial discharge signal detection circuit whole needs 3.3V power supply, operational amplifier needs +5V and-5V power supply, and AD conversion chip needs 5V power supply.

[0037] Therefore, the utility model provides a switchgear ultrasonic partial discharge signal detection circuit, which includes: an ultrasonic sensor, a preamplifier circuit, a filter circuit, a detection circuit, and an AD conversion circuit.

[0038] The above is only the preferred embodiment of the utility model, and does not limit the utility model, any modification, equivalent replacement and improvement within the spirit and principle of the utility model should be included in the protection scope of the utility model.

Claims

1. A switchgear ultrasonic partial discharge signal detection circuit, characterized in that, include: The system includes an ultrasonic sensor, a preamplifier circuit, a filter circuit, a detector circuit, and an AD conversion circuit; among which, The preamplifier circuit is electrically connected to the ultrasonic sensor and is used to amplify the raw ultrasonic signal detected by the ultrasonic sensor. The filtering circuit is electrically connected to the preamplifier circuit and is used to filter the original ultrasonic signal amplified by the preamplifier circuit to obtain an effective ultrasonic signal. The detection circuit is electrically connected to the filter circuit and is used to perform peak detection on the effective ultrasonic signal obtained after filtering by the filter circuit to obtain the peak voltage of the effective ultrasonic signal. The AD conversion circuit is electrically connected to the detection circuit and is used to perform AD conversion on the peak voltage of the effective ultrasonic signal obtained by the peak detection processing of the detection circuit to obtain an ultrasonic digital signal. The preamplifier circuit includes: a first-stage operational amplifier, a second-stage operational amplifier, a filter capacitor, and an input impedance. One end of the filter capacitor and one end of the input impedance are connected to the signal input terminal of the preamplifier circuit. The other end of the filter capacitor is grounded. The other end of the input impedance is connected to the non-inverting input terminal of the first-stage operational amplifier. The output terminal of the first-stage operational amplifier is connected to the non-inverting input terminal of the second-stage operational amplifier. The output terminal of the second-stage operational amplifier is connected to the signal output terminal of the preamplifier circuit. The filter circuit is a second-order active bandpass filter circuit, consisting of an input capacitor, a 100kHz low-pass filter circuit, a 35kHz high-pass filter circuit, and cascaded operational amplifiers, with a bandwidth of 65kHz.

2. The switchgear ultrasonic partial discharge signal detection circuit of claim 1, wherein, The detection circuit includes an amplifier chip of model AD8310ARMZ and its peripheral circuitry.

3. The switchgear ultrasonic partial discharge signal detection circuit of claim 2, wherein, The AD conversion circuit includes an AD conversion chip of model ADS7822U and its peripheral circuits.

4. The switchgear ultrasonic partial discharge signal detection circuit according to any one of claims 1-3, wherein, It includes a power supply circuit for providing corresponding power to the ultrasonic sensor, the preamplifier circuit, the detector circuit, and the AD conversion circuit.

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