Interference signal suppression device and method for partial discharge pulse measurement of electrical equipment

Abstract

The invention relates to an interference signal suppression device and method for partial discharge pulse measurement of electrical equipment. The interference signal during partial discharge test of high-voltage electrical equipment is suppressed and eliminated through hardware isolation. The components used are simple and easy to obtain, with low cost, and no interference signal is generated by themselves. The wiring and operation are simple, and the test detection efficiency is improved and the detection time is shortened. There is no need to distinguish whether the detected signal comes from the outside or the inside of the test product, and the signal source can be automatically determined according to the circuit principle, and the effect of removing the interference signal is remarkable. At the same time, the partial discharge signal after the interference is eliminated can also be amplified, which is convenient for subsequent observation of the signal.

Description

Technical Field

[0001] The invention relates to an interference signal suppression device and an interference signal suppression method used in measuring partial discharge pulses of electrical equipment. Background Art

[0002] Partial discharge detection is a major means of evaluating the insulation condition of electrical equipment, but there are some difficulties in practical application. The main reason is that the interference from various aspects is strong during on-site detection, and the partial discharge signal is difficult to be accurately detected. Therefore, in the partial discharge detection process of power equipment, only by maximally suppressing and shielding the interference signal can the information of partial discharge of electrical equipment be effectively obtained, which is crucial to evaluating the insulation condition of electrical equipment.

[0003] For various interference signals in partial discharge detection, the existing methods of suppressing interference signals mainly include using hardware isolation or digital filtering of signals. Hardware isolation often uses isolation transformers, adding electromagnetic shielding to the test area, and other methods. The use of isolation transformers will increase the test cost, and the test site environment is generally more complex, and complete electromagnetic shielding cannot be achieved. The interference suppression method of digital filtering is mainly used in long-term online monitoring of partial discharge of equipment. It is necessary to continuously collect a large amount of electrical equipment operating data as raw data for algorithm training to achieve a more accurate interference suppression effect. In this process, more computer resources will be consumed. If the operating conditions of the electrical equipment change, the accuracy of the algorithm will be significantly reduced, and the algorithm needs to be retrained, which consumes time and resources.

[0004] The patent application with publication number CN102565645A, "An Anti-interference Online Monitoring Method for Partial Discharge of Generators", proposes to install sensors at the near and far ends of the generator under test, and distinguish the interference signal from the partial discharge signal by calculating the time delay Δt of the two signals. This method involves more hardware equipment such as sensors, coaxial cables and special connectors, which is relatively expensive. Digital filters are used to filter out interference signals, which consumes more computer resources accordingly. The patent application with publication number CN111458616A, "A Common-mode Interference Suppression Partial Discharge Signal-to-Noise Ratio Improvement Device and Method", uses Rogowski coils to cancel out partial discharge signals in the external environment in the Rogowski coils, thereby suppressing interference signals. However, when the Rogowski coils are used to measure non-sinusoidal currents or currents of unknown frequencies, in order to improve the accuracy, an integrator needs to be configured, which adds extra workload and cost. Therefore, its improvement and innovation are imperative. Summary of the invention

[0005] In view of the above situation, in order to overcome the defects of the prior art, the purpose of the present invention is to provide an interference signal suppression device and method for partial discharge pulse measurement of electrical equipment, which can effectively solve the problem of suppressing and eliminating interference signals during partial discharge testing of high-voltage electrical equipment through hardware isolation.

[0006] The technical solution provided by the present invention is:

[0007] An interference signal suppression device for partial discharge pulse measurement of electrical equipment, comprising a three-phase power supply, a frequency converter, a step-up transformer, and a test equipment C x , adjustable coupling capacitor C k and a partial discharge detection device, the device also includes an interference signal elimination device based on a differential operational amplifier, a three-phase power supply is connected to a frequency converter, the frequency converter is connected to a step-up transformer, and the step-up transformer terminal is connected to the test equipment C x High voltage side and adjustable coupling capacitor C k High voltage side parallel connection;

[0008] The interference signal elimination device comprises a housing and a differential operational amplifier, adjustable resistors R5 and R6, adjustable capacitors C1 and C2, resistors R1, R2, R3 and R4 installed in the housing. The negative input end of the differential operational amplifier serves as a voltage input end, which is respectively connected to one end of the resistor R1 and one end of the resistor R3. The other end of R1 is respectively connected to one end of the adjustable resistor R5 and one end of the adjustable capacitor C1. The common end serves as a first signal input terminal of the interference signal elimination device and is connected to the adjustable coupling capacitor C1. k The positive input terminal of the differential operational amplifier is used as another voltage input terminal, which is respectively connected to one end of the resistor R2 and one end of the resistor R4. The other end of the resistor R2 is respectively connected to one end of the adjustable resistor R6 and one end of the adjustable capacitor C2. The common end is used as the second signal input terminal of the interference signal elimination device and connected to the tested equipment C x The other end of the adjustable resistor R5 is connected to the other end of the adjustable capacitor C1, the other end of the adjustable resistor R6 and the other end of the adjustable capacitor C2 respectively, and the common end is grounded as the third signal input terminal of the interference signal elimination device, the other end of the resistor R3 is connected to the output end of the differential operational amplifier, and the common end of the two and the other end of the resistor R4 are respectively connected to the partial discharge detection device as the two output ends of the interference signal elimination device, wherein:

[0009] The three-phase power supply is used to provide power for detecting partial discharge of electrical equipment;

[0010] The frequency converter is used to adjust the frequency and amplitude of the input power supply;

[0011] The interference signal elimination device is used to eliminate the interference signal passing through the test equipment C x and coupling capacitor C kThe signal is sampled and the interference signal is eliminated to retain the partial discharge signal;

[0012] The partial discharge detection device is used to receive and display the partial discharge signal processed by the interference signal elimination device;

[0013] The part of the adjustable resistor R5 and the adjustable capacitor C1 connected in parallel is used as the first detection impedance Z m1 The part of the adjustable resistor R6 and the adjustable capacitor C2 in parallel is used as the second detection impedance Z m2 ;

[0014] If the interfered signal comes from outside, the first detection impedance Z m1 and the second detection impedance Z m2 The upper potential is equal to the same polarity, and the voltage U of the two signal input terminals of the differential operational amplifier circuit is in1 , U in2 Also equal in magnitude and polarity, the output signal

[0015] If a real partial discharge signal is generated inside the test product, the first detection impedance Z m1 and the second detection impedance Z m2 The voltages at the two signal input terminals of the differential operational amplifier circuit are equal in magnitude and opposite in polarity. in1 , U in2 are equal in magnitude and opposite in polarity, the output signal

[0016] A method for suppressing interference signals based on the above interference signal suppression device comprises the following steps:

[0017] Step 1: Wiring

[0018] The three-phase power supply is connected to the inverter, the inverter is connected to the step-up transformer, and the terminal of the step-up transformer is connected to the C terminal of the test equipment. x High voltage side and adjustable coupling capacitor C k High voltage side parallel, adjustable coupling capacitor C k The low voltage side is connected to the first signal input terminal of the interference signal elimination device, and the test equipment C x The low voltage side is connected to the second signal input terminal of the interference signal elimination device, the third signal input terminal of the interference signal elimination device is grounded, and the two output ends of the interference signal elimination device are connected to the partial discharge detection device;

[0019] Step 2: Adjust parameters

[0020] Measuring the device under test C x Assuming the capacitance of the test product is x F, adjust the adjustable coupling capacitor C kThe capacitance of the two capacitors is equal, and then the values ​​of the adjustable resistors R5 and R6 and the adjustable capacitors C1 and C2 are adjusted as follows:

[0021] The capacitance of the adjustable capacitors C1 and C2 is adjusted to 0.5x F;

[0022] The resistance values ​​of adjustable resistors R5 and R6 are adjusted to

[0023] Step 3: Collect partial discharge signals

[0024] Turn on the power supply and adjust the frequency converter to change the voltage and frequency at both ends of the equipment under test. After reaching the test voltage, read the partial discharge signal on the partial discharge detection device to obtain the partial discharge signal with external interference signals filtered out.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1) Hardware isolation is used to suppress and eliminate interference signals during partial discharge tests of high-voltage electrical equipment. The components used are simple and easy to obtain, low in cost, and do not generate interference signals themselves;

[0027] 2) Simple wiring and operation, improving test efficiency and shortening test time;

[0028] 3) It does not need to distinguish whether the detected signal comes from the outside or inside of the test product. The signal source can be automatically determined according to the circuit principle, and the effect of removing interference signals is significant;

[0029] 4) At the same time, the local discharge signal after the interference is eliminated can also be amplified to facilitate subsequent signal observation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The schematic diagram of the circuit of the present invention is shown in FIG.

[0031] Figure 2 The figure is a circuit diagram of the interference signal elimination device of the present invention. DETAILED DESCRIPTION

[0032] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0033] Depend on Figure 1-2 The present invention provides an interference signal suppression device for partial discharge pulse measurement of electrical equipment, comprising a three-phase power supply, a frequency converter, a step-up transformer, a test equipment C x , adjustable coupling capacitor C k and a partial discharge detection device, the device also includes an interference signal elimination device based on a differential operational amplifier, a three-phase power supply is connected to a frequency converter, the frequency converter is connected to a step-up transformer, and the step-up transformer terminal is connected to the test equipment Cx High voltage side and adjustable coupling capacitor C k High voltage side parallel connection;

[0034] The interference signal elimination device comprises a housing and a differential operational amplifier, adjustable resistors R5 and R6, adjustable capacitors C1 and C2, resistors R1, R2, R3 and R4 installed in the housing. The negative input end of the differential operational amplifier serves as a voltage input end, which is respectively connected to one end of the resistor R1 and one end of the resistor R3. The other end of R1 is respectively connected to one end of the adjustable resistor R5 and one end of the adjustable capacitor C1. The common end serves as a first signal input terminal of the interference signal elimination device and is connected to the adjustable coupling capacitor C1. k The positive input terminal of the differential operational amplifier is used as another voltage input terminal, which is respectively connected to one end of the resistor R2 and one end of the resistor R4. The other end of the resistor R2 is respectively connected to one end of the adjustable resistor R6 and one end of the adjustable capacitor C2. The common end is used as the second signal input terminal of the interference signal elimination device and connected to the tested equipment C x The other end of the adjustable resistor R5 is connected to the other end of the adjustable capacitor C1, the other end of the adjustable resistor R6 and the other end of the adjustable capacitor C2 respectively, and the common end is grounded as the third signal input terminal of the interference signal elimination device, the other end of the resistor R3 is connected to the output end of the differential operational amplifier, and the common end of the two and the other end of the resistor R4 are respectively connected to the partial discharge detection device as the two output ends of the interference signal elimination device, wherein:

[0035] The three-phase power supply is used to provide power for detecting partial discharge of electrical equipment;

[0036] The frequency converter is used to adjust the frequency and amplitude of the input power supply;

[0037] The interference signal elimination device is used to eliminate the interference signal passing through the test equipment C x and coupling capacitor C k The signal is sampled and the interference signal is eliminated to retain the partial discharge signal;

[0038] The partial discharge detection device is used to receive and display the partial discharge signal processed by the interference signal elimination device;

[0039] The part of the adjustable resistor R5 and the adjustable capacitor C1 connected in parallel is used as the first detection impedance Z m1 The part of the adjustable resistor R6 and the adjustable capacitor C2 in parallel is used as the second detection impedance Z m2 ;

[0040] The interference signal elimination device includes a signal sampling part and an interference signal elimination and partial discharge signal amplification part. The first detection impedance Z m1 and the second detection impedance Z m2The parallel part constitutes a signal sampling part, and the differential operational amplifier constitutes an interference signal elimination and partial discharge signal amplification part;

[0041] Differential operational amplifiers are generally used in integrated circuits, and are often used to amplify analog signals and suppress zero-point drift of analog electronic components. They are not used in high-voltage electrical tests to eliminate interference signals. Interference signals all flow from the outside of the test object through the test object and then enter the partial discharge detection system. The actual partial discharge signal of the electrical equipment is generated by its internal insulation degradation, and then amplified and detected by the partial discharge detection system after being detected by the detection impedance. The present invention suppresses and eliminates interference signals during routine tests of high-voltage electrical equipment through a hardware isolation method.

[0042] If the interfered signal comes from outside, the first detection impedance Z m1 and the second detection impedance Z m2 The upper potential is equal to the same polarity, and the voltage U of the two signal input terminals of the differential operational amplifier circuit is in1 , U in2 They are also equal in size and polarity. According to the operational characteristics of the differential amplifier circuit, the output signal

[0043] If a real partial discharge signal is generated inside the test product, the first detection impedance Z m1 and the second detection impedance Z m2 The voltages at the two signal input terminals of the differential operational amplifier circuit are equal in magnitude and opposite in polarity. in1 , U in2 are equal in magnitude and opposite in polarity. According to the operational characteristics of the differential amplifier circuit, the output signal

[0044] The shell of the interference signal elimination device is a magnetic metal shell, which is used for electromagnetic shielding.

[0045] A method for suppressing interference signals based on the above interference signal suppression device comprises the following steps:

[0046] Step 1: Wiring

[0047] The three-phase power supply is connected to the inverter, the inverter is connected to the step-up transformer, and the terminal of the step-up transformer is connected to the C terminal of the test equipment. x High voltage side and adjustable coupling capacitor C k High voltage side parallel, adjustable coupling capacitor C k The low voltage side is connected to the first signal input terminal of the interference signal elimination device, and the test equipment C x The low voltage side is connected to the second signal input terminal of the interference signal elimination device, the third signal input terminal of the interference signal elimination device is grounded, and the two output ends of the interference signal elimination device are connected to the partial discharge detection device;

[0048] Step 2: Adjust parameters

[0049] Measuring the device under test C x Assuming the capacitance of the test product is x F, adjust the adjustable coupling capacitor C k The capacitance of the two capacitors is equal, and then the values ​​of the adjustable resistors R5 and R6 and the adjustable capacitors C1 and C2 are adjusted as follows:

[0050] The capacitance of the adjustable capacitors C1 and C2 is adjusted to 0.5x F;

[0051] The resistance values ​​of adjustable resistors R5 and R6 are adjusted to

[0052] The principle of adjustable resistance calculation is as follows: β is a constant, usually 2.5×10 5 In the formula, Rm is R5 or R6 in the schematic diagram of the present invention, and Cm is C1 or C2 in the schematic diagram of the present invention, and the values ​​of the adjustable resistors R5 and R6 are obtained as follows:

[0053] In this embodiment, the capacitance of the test product is 0.5μF, then C1=C2=0.25μF, R5=R6=8Ω

[0054] Step 3: Collect partial discharge signals

[0055] Turn on the power supply and adjust the frequency converter to change the voltage and frequency at both ends of the equipment under test. After reaching the test voltage, read the partial discharge signal on the partial discharge detection device to obtain the partial discharge signal with external interference signals filtered out.

[0056] The local discharge signal is a series of pulse signals with periodic changes and fixed phases. At this time, the interference signal from the outside is filtered out, and the remaining signal is the local discharge signal of the electrical equipment after being amplified 3-5 times. The staff can identify the type of local discharge inside the electrical equipment based on the extracted discharge pulse waveform.

[0057] The amplification factor of the differential operational amplifier in the interference signal elimination device is 3-5 times.

[0058] In order to amplify the signal while keeping the signal undistorted, the present embodiment selects the amplification factor of 3 times. According to the differential operational amplifier signal amplification factor formula: Take R1=R2=10kΩ, R3=R4=30kΩ.

[0059] The device and method of the present invention are verified by using the electronic simulation software Multisim. External interference signals and real partial discharge signals are applied simultaneously. The external interference signals are added from the outside of the tested electrical equipment Cx, and the real partial discharge signals are added from the inside of the tested product Cx. The simulated interference signals and partial discharge signals appear at the same time. The final processed signal is displayed using an oscilloscope. The final partial discharge signal is amplified by 3 times, and the interference signal is filtered out, realizing the function of filtering out the interference amplified signal. The specific simulation waveforms are square waves and peak waves for verification, and the specific data are shown in the following table.

[0060] Table 1 Injected pulse signal and the pulse signal left after filtering

[0061]

[0062] It can be seen from the table that a total of 8 groups of interference pulse signals with different frequencies, amplitudes and duty cycles were injected, and 2 groups of partial discharge pulse signals with certain frequencies, amplitudes and duty cycles were injected. After simulation verification using the analog electronic simulation software Multisim, the 8 groups of interference signals were filtered out, while the 2 groups of partial discharge pulse signals were retained and amplified.

Claims

1. An interference signal suppression device for partial discharge pulse measurement of electrical equipment, including a three-phase power supply, a frequency converter, a step-up transformer, and a test equipment C x , adjustable coupling capacitor C k and a partial discharge detection device, characterized in that, The device also includes an interference signal elimination device based on a differential operational amplifier. The three-phase power supply is connected to the frequency converter, the frequency converter is connected to the step-up transformer, and the high-voltage side terminal of the step-up transformer is connected to the C of the test equipment. x And adjustable coupling capacitor C k in parallel; The interference signal elimination device comprises a housing and a differential operational amplifier, adjustable resistors R5 and R6, adjustable capacitors C1 and C2, resistors R1, R2, R3 and R4 installed in the housing. The negative input end of the differential operational amplifier serves as a voltage input end, which is respectively connected to one end of the resistor R1 and one end of the resistor R3. The other end of R1 is respectively connected to one end of the adjustable resistor R5 and one end of the adjustable capacitor C1. The common end serves as a first signal input terminal of the interference signal elimination device and is connected to the adjustable coupling capacitor C1. k The positive input terminal of the differential operational amplifier is used as another voltage input terminal, which is respectively connected to one end of the resistor R2 and one end of the resistor R4. The other end of the resistor R2 is respectively connected to one end of the adjustable resistor R6 and one end of the adjustable capacitor C2. The common end is used as the second signal input terminal of the interference signal elimination device and connected to the test equipment C x The other end of the adjustable resistor R5 is connected to the other end of the adjustable capacitor C1, the other end of the adjustable resistor R6 and the other end of the adjustable capacitor C2 respectively, and the common end is grounded as the third signal input terminal of the interference signal elimination device, the other end of the resistor R3 is connected to the output end of the differential operational amplifier, and the common end of the two and the other end of the resistor R4 are respectively connected to the partial discharge detection device as the two output ends of the interference signal elimination device, wherein: The three-phase power supply is used to provide power for detecting partial discharge of electrical equipment; The frequency converter is used to adjust the frequency and amplitude of the input power supply; The interference signal elimination device is used to eliminate the interference signal passing through the test equipment C x and coupling capacitor C k The signal is sampled and the interference signal is eliminated to retain the partial discharge signal; The partial discharge detection device is used to receive and display the partial discharge signal processed by the interference signal elimination device; The part of the adjustable resistor R5 and the adjustable capacitor C1 connected in parallel is used as the first detection impedance Z m1 The part of the adjustable resistor R6 and the adjustable capacitor C2 in parallel is used as the second detection impedance Z m2 ; The interference signal comes from the outside, the first detection impedance Z m1 and the second detection impedance Z m2 The upper potential is equal to the same polarity, and the voltage U of the two signal input terminals of the differential operational amplifier circuit is in1 , U in2 Also equal in magnitude and polarity, the output signal If a real partial discharge signal is generated inside the test product, the first detection impedance Z m1 and the second detection impedance Z m2 The voltages at the two signal input terminals of the differential operational amplifier circuit are equal in magnitude and opposite in polarity. in1 , U in2 are equal in magnitude and opposite in polarity, the output signal 2. The interference signal suppression device for partial discharge pulse measurement of electrical equipment according to claim 1, characterized in that: The shell of the interference signal elimination device is a magnetic metal shell, which is used for electromagnetic shielding.

3. A method for suppressing interference signals based on the interference signal suppression device according to claim 1, characterized in that: The following steps are involved: Step 1: Wiring The three-phase power supply is connected to the inverter, the inverter is connected to the step-up transformer, and the high-voltage side terminal of the step-up transformer is connected to the C terminal of the test equipment. x One end and adjustable coupling capacitor C k One end is connected in parallel, and the coupling capacitor C is adjustable k The other end is connected to the first signal input terminal of the interference signal elimination device. x The other end is connected to the second signal input terminal of the interference signal elimination device, the third signal input terminal of the interference signal elimination device is grounded, and the two output ends of the interference signal elimination device are connected to the partial discharge detection device; Step 2: Adjust parameters Measuring the device under test C x Assuming the capacitance of the test product is x F, adjust the adjustable coupling capacitor C k The capacitance of the two capacitors is equal, and then the values ​​of the adjustable resistors R5 and R6 and the adjustable capacitors C1 and C2 are adjusted as follows: The capacitance of the adjustable capacitors C1 and C2 is adjusted to 0.5x F; The resistance values ​​of adjustable resistors R5 and R6 are adjusted to Step 3: Collect partial discharge signals Turn on the power supply and adjust the frequency converter to change the voltage and frequency at both ends of the equipment under test. After reaching the test voltage, read the partial discharge signal on the partial discharge detection device to obtain the partial discharge signal with external interference signals filtered out.

4. The interference signal suppression method according to claim 3, characterized in that: The amplification factor of the differential operational amplifier in the interference signal elimination device is 3-5 times.

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