A kind of metering high voltage mutual inductor secondary circuit fault detection method and device

Abstract

A kind of metering high-voltage transformer secondary circuit fault detection method and device, when high-voltage transformer secondary circuit appears distorted waveform, the temperature of the body of high-voltage transformer, secondary side outlet joint temperature, incoming line bus temperature are collected, the vibration amplitude of high-voltage transformer is monitored, and the impedance value of secondary current incoming and outgoing line circuit under high-frequency voltage signal is obtained;According to the comparison result of the temperature collected and the corresponding temperature normal range, distinguish whether high-voltage transformer fault or power system fault, and determine the fault type of high-voltage transformer;According to the comparison result of vibration amplitude and the amplitude threshold value set, it is judged whether high-voltage transformer exists installation fault;According to the comparison result of impedance value and the threshold value set, it is judged whether high-voltage transformer secondary circuit exists fault. Multiple detection technologies are integrated, and high-voltage transformer secondary circuit grounding fault and latent secondary circuit short circuit or grounding fault are more comprehensively and intelligently detected.

Description

Technical Field

[0001] This invention relates to the field of instrument transformer technology, and more specifically, to a method and apparatus for detecting faults in the secondary circuit of a metering high-voltage instrument transformer. Background Technology

[0002] The quality of operation of high-voltage current transformers directly affects the accuracy of power system measurement and metering, as well as the reliability of relay protection and automatic devices, and has a significant impact on the safe operation of the power system.

[0003] Existing methods for detecting faults in current transformer connections rely on visual inspection or multimeter measurements. These methods are time-consuming and labor-intensive, requiring regular maintenance or inspections, and often fail to detect faults promptly, resulting in limited effectiveness. Furthermore, determining whether a grounding fault exists in the metering current loop without requiring consultation with the user or a power outage for inspection, thereby improving the professionalism and efficiency of the work, is a problem that urgently needs in-depth research.

[0004] Traditional methods of manually inspecting faults by visual observation or using multimeters for connection testing can only be used for periodic maintenance or inspections. This is time-consuming, labor-intensive, and often fails to detect faults promptly, resulting in poor effectiveness. Existing technology 1 (CN108627793B), "A Fault Identification Method for Electronic Current Transformers Based on Waveform Inversion," proposes inputting a sudden change in instantaneous current at the input terminal of the electronic current transformer and sampling the output waveform. It then uses the distortion of the output waveform to determine if there is a system fault other than a fault in the electronic current transformer itself. When the output waveform is distorted, it performs an inversion operation of differentiation followed by integration. If the inversion fails, a fault in the electronic current transformer is confirmed. Existing technology 1 accurately locates the fault point based on the inverted waveform characteristics, providing technical support for the reliability research of electronic current transformers and the applicability of digital relay protection to electronic current transformers. However, existing technology 1 can only determine whether a current transformer has failed; it cannot further determine the type of fault and cannot provide accurate reference suggestions for subsequent maintenance. At the same time, existing technologies do not organically integrate multiple technical means to form a complete and mutually supportive fault detection method. Furthermore, the detection methods are relatively traditional and difficult to detect minute latent faults. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method and apparatus for detecting grounding faults in the secondary circuit of a high-voltage instrument transformer, thereby detecting the types of grounding faults in the secondary circuit of the high-voltage instrument transformer.

[0006] The present invention adopts the following technical solution.

[0007] This invention proposes a method for detecting faults in the secondary circuit of a metering high-voltage transformer, comprising:

[0008] Step 1: When a distorted waveform appears in the secondary circuit of the high-voltage transformer, collect the body temperature of the high-voltage transformer, the temperature of the secondary side outgoing connector, and the temperature of the incoming busbar. Monitor the vibration amplitude of the high-voltage transformer and obtain the impedance values ​​of the secondary current inlet and outlet circuits under high-frequency voltage signals.

[0009] Step 2: Based on the comparison results of the collected temperatures with the corresponding normal temperature ranges, distinguish between high-voltage transformer faults and power system faults, and determine the type of high-voltage transformer fault; based on the comparison results of vibration amplitude with the set amplitude threshold, determine whether there is an installation fault in the high-voltage transformer; based on the comparison results of impedance value with the set threshold, determine whether there is a fault in the secondary circuit of the high-voltage transformer.

[0010] Preferably, in step 1, the voltage and current waveforms of the secondary circuit of the high-voltage transformer are sampled, and distortion events of the voltage and current waveforms are monitored.

[0011] The distorted waveforms within a set interval before and after the distortion event are collected, and the collected distorted waveforms are sampled twice using the generalized polynomial interpolation method to obtain the distorted waveforms to be inverted.

[0012] The distorted waveform to be inverted is inverted to obtain the inverted waveform. If the inverted waveform is distorted compared with the normal waveform, it is determined that there is a fault in the high voltage transformer. The relevant temperature is collected, the vibration amplitude is monitored, and the corresponding impedance value is obtained.

[0013] If the inverted waveform is not distorted compared to the normal waveform, it is determined that there is signal interference in the high-voltage transformer.

[0014] Preferably, the inversion operation includes differentiation followed by integration.

[0015] The differential formula is as follows:

[0016]

[0017] In the formula,

[0018] e(t) represents the output voltage and current of the high-voltage transformer.

[0019] i p (t) is a function of the primary current passing through the coil.

[0020] M = μ0·N·A, where μ0 is the permeability of free space, N is the number of turns density of the coil, and A is the area of ​​a single turn of the coil;

[0021] The formula for integral operation is:

[0022]

[0023] In the formula,

[0024] H(s) is the S-domain transfer function of the lossy integrator.

[0025] R1 is the input resistor.

[0026] R2 is a lossy attenuation resistor.

[0027] C is the integrating capacitor.

[0028] s is a complex variable.

[0029] Preferably, in step 2, the body temperature of the high-voltage transformer, the temperature of the secondary side outgoing connector, and the temperature of the incoming busbar are collected.

[0030] If the temperature of the transformer body and the temperature of the incoming bus are both within the set normal temperature range, but the temperature of the secondary side outgoing connector is not within the set normal temperature range, then the high voltage transformer secondary side outgoing connector is determined to be faulty.

[0031] If the temperature of the incoming bus is within the set normal temperature range, but the temperature of the transformer body and the temperature of the secondary side outgoing connector are not within the set normal temperature range, then it is determined to be an internal fault of the high voltage transformer.

[0032] If the temperature of the incoming bus is not within the set normal temperature range, it is determined to be a power system fault.

[0033] Preferably, the set normal temperature range is [T-Δt, T+Δt], where Δt is the set temperature deviation, which is 10℃, and T is the reference temperature, satisfying the following relationship:

[0034] T = T e +k×I

[0035] In the formula, T e Where is the ambient temperature, k is a constant greater than 0, and I is the load current.

[0036] Preferably, in step 2, the vibration amplitude of the high-voltage transformer is monitored, and the amplitude of the high-voltage transformer body and the amplitude of the mounting base are collected. If the difference between the amplitude of the body and the amplitude of the mounting base exceeds the set amplitude threshold, it is determined that there is an installation fault in the high-voltage transformer.

[0037] Preferably, the set amplitude threshold value ranges from greater than or equal to 0.05 mm to less than or equal to 0.10 mm.

[0038] Preferably, in step 2, a 5kHz high-frequency voltage signal is applied to the line between the secondary output port of the transformer and the input port of the meter to calculate the impedance values ​​of the secondary current inlet and outlet circuits; the calculated impedance values ​​are compared with the rated impedance values ​​calculated using the rated parameters of the transformer; if the deviation between the impedance values ​​and the rated impedance values ​​is greater than a set threshold, it is determined that there is a grounding or short-circuit fault in the secondary circuit of the high-voltage transformer.

[0039] Preferably, the threshold value is set to 5% of the impedance rating.

[0040] The present invention also proposes a fault detection device for the secondary circuit of a high-voltage transformer for metering, comprising: a main control unit, a waveform sampling unit, a temperature acquisition unit, a vibration acquisition unit, a high-frequency signal generation unit, and a high-frequency impedance measurement unit;

[0041] The main control unit is used to sample the voltage and current waveforms of the secondary circuit of the high-voltage transformer from the waveform sampling unit and to monitor voltage and current waveform distortion events. When a distorted waveform appears in the secondary circuit of the high-voltage transformer, the temperature acquisition unit is controlled to collect the body temperature of the high-voltage transformer, the temperature of the secondary side outgoing terminal, and the temperature of the incoming bus. The vibration acquisition unit is controlled to monitor the vibration amplitude of the high-voltage transformer. The high-frequency signal generation unit is controlled to apply a 5kHz high-frequency voltage signal to the line between the secondary outgoing port of the transformer and the incoming port of the meter. The high-frequency current signal measurement unit is controlled to calculate the impedance values ​​of the secondary current inlet and outlet circuits.

[0042] The main control unit is also used to distinguish between high-voltage transformer faults and power system faults based on the comparison results of various collected temperatures with the corresponding normal temperature ranges, and to determine the type of high-voltage transformer fault; to determine whether there is an installation fault in the high-voltage transformer based on the comparison results of the vibration amplitude with the set amplitude threshold; and to determine whether there is a fault in the secondary circuit of the high-voltage transformer based on the comparison results of the impedance value with the set threshold.

[0043] Preferably, the device further includes: an alarm unit and a storage unit;

[0044] The alarm unit is used to generate corresponding alarms based on the fault type output by the main control unit.

[0045] Storage unit, used to store collected data and processing results.

[0046] Preferably, the input terminal of the waveform sampling unit is connected to the input terminal of the open circuit detection unit, and the input terminal of the open circuit detection unit is connected to the secondary output terminal of the high voltage transformer.

[0047] The input terminal of the temperature acquisition unit is connected to the high voltage transformer body, the connector of the high voltage transformer secondary side output line, and the busbar of the high voltage transformer input line, respectively.

[0048] The input terminals of the vibration acquisition unit are connected to the body of the high-voltage transformer and the mounting base, respectively.

[0049] The input terminals of the high-frequency impedance measurement unit are connected to the secondary current inlet and outlet circuits, respectively.

[0050] The outputs of the open circuit detection unit, temperature acquisition unit, vibration acquisition unit, and high-frequency impedance measurement unit are connected to the main control unit through an OR gate logic circuit.

[0051] Preferably, the open-circuit detection unit includes a first adjustable resistor, a second adjustable resistor, a voltage divider resistor, and a first operational amplifier connected in series. One end of the first adjustable resistor is connected to the secondary output terminal of the high-voltage transformer, and the other end of the first adjustable resistor is connected to one end of the second adjustable resistor and one end of the voltage divider resistor. The other end of the second adjustable resistor is grounded, and the other end of the voltage divider resistor is connected to the inverting input terminal of the first operational amplifier. The non-inverting input terminal of the first operational amplifier receives a power frequency signal that is opposite in direction to the secondary output signal of the high-voltage transformer.

[0052] The output of the first operational amplifier is connected to an OR gate logic circuit.

[0053] Preferably, the temperature acquisition unit includes a temperature sensor, a first digital-to-analog converter, and a second operational amplifier connected in series.

[0054] There are multiple temperature sensors, each of which is installed on the high voltage transformer body, the connector of the high voltage transformer secondary side output line, and the busbar of the high voltage transformer input line. The output of each temperature sensor is connected to the first digital-to-analog converter, the output of the first digital-to-analog converter is connected to the inverting input of the second operational amplifier, and the normal temperature range is input to the non-inverting input of the second operational amplifier.

[0055] The output of the second operational amplifier is connected to an OR gate logic circuit.

[0056] Preferably, the vibration acquisition unit includes a vibration sensor, a second digital-to-analog converter, and a third operational amplifier connected in series.

[0057] There are multiple vibration sensors, each of which is installed on the body and mounting base of the high voltage transformer. The output of each vibration sensor is connected to the second digital-to-analog converter. The output of the second digital-to-analog converter is connected to the inverting input of the third operational amplifier. The non-inverting input of the third operational amplifier is input with the set amplitude threshold.

[0058] The output of the third operational amplifier is connected to an OR gate logic circuit.

[0059] Preferably, the high-frequency impedance measurement unit includes: a high-frequency impedance generation circuit, a third digital-to-analog converter, and a fourth operational amplifier;

[0060] The high-frequency impedance generation circuit includes a high-frequency signal generator, a clamp-on current transformer, a signal conditioner, and a high-pass filter. The high-frequency signal generator is used to apply a high-frequency voltage signal between the current input and output circuits. The clamp-on current transformer is used to measure the secondary circuit current. The signal conditioner is used to filter out low-frequency signals from the mixed current signal. The input terminal of the signal conditioner is connected to the secondary winding of the clamp-on current transformer through an analog signal line, and the output terminal of the signal conditioner is connected to the input terminal of the high-pass filter through an analog signal line.

[0061] The output of the high-pass filter is connected to the input of the third digital-to-analog converter via a differential analog signal line; the output of the third digital-to-analog converter is connected to the inverting input of the fourth operational amplifier, and the non-inverting input of the fourth operational amplifier receives the set threshold.

[0062] The output of the fourth operational amplifier is connected to an OR gate logic circuit.

[0063] The beneficial effects of this invention are that, compared with the prior art, it focuses on the integration of multiple detection technologies, and the proposed high-frequency signal detection method is conducive to detecting latent secondary circuit short circuits or grounding faults. After the integration of technologies, it can more comprehensively and intelligently detect grounding faults in the secondary circuit of high-voltage transformers. Attached Figure Description

[0064] Figure 1 This is a flowchart of a method for detecting faults in the secondary circuit of a high-voltage instrument transformer for metering, as proposed in this invention.

[0065] Figure 2 This is a structural diagram of a high-voltage transformer secondary circuit fault detection device proposed in this invention.

[0066] Figure 2 The accompanying diagrams are described below:

[0067] R1 - First adjustable resistor, R2 - Second adjustable resistor, R3 - Voltage divider resistor

[0068] U1 - First operational amplifier, U2 - Second operational amplifier, U3 - Third operational amplifier, U4 - Fourth operational amplifier

[0069] Y1 - OR gate logic circuit, D / A - digital-to-analog converter, A / D - analog-to-digital converter, T1 - temperature sensor, C1 - vibration sensor, I1 - high-frequency impedance generation circuit. Detailed Implementation

[0070] The present application will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and should not be construed as limiting the scope of protection of the present application.

[0071] This invention proposes a method for detecting faults in the secondary circuit of a metering high-voltage transformer, such as... Figure 1 As shown, it includes:

[0072] Step 1: When a distorted waveform appears in the secondary circuit of the high-voltage transformer, collect the body temperature of the high-voltage transformer, the temperature of the secondary side outgoing connector, and the temperature of the incoming busbar. Monitor the vibration amplitude of the high-voltage transformer and obtain the impedance values ​​of the secondary current inlet and outlet circuits under high-frequency voltage signals.

[0073] Specifically, in step 1, the voltage and current waveforms of the secondary circuit of the high-voltage transformer are sampled, and distortion events of the voltage and current waveforms are monitored.

[0074] The distorted waveforms within a set interval before and after the distortion event are collected, and the collected distorted waveforms are sampled twice using the generalized polynomial interpolation method to obtain the distorted waveforms to be inverted.

[0075] The distorted waveform to be inverted is inverted to obtain the inverted waveform. If the inverted waveform is distorted compared with the normal waveform, it is determined that there is a fault in the high voltage transformer. The relevant temperature is collected, the vibration amplitude is monitored, and the corresponding impedance value is obtained.

[0076] If the inverted waveform is not distorted compared to the normal waveform, it is determined that there is signal interference in the high-voltage transformer.

[0077] Specifically, the inversion operation includes differentiation followed by integration.

[0078] The differential formula is as follows:

[0079]

[0080] In the formula,

[0081] e(t) represents the output voltage and current of the high-voltage transformer.

[0082] i p (t) is a function of the primary current passing through the coil.

[0083] M = μ0·N·A, where μ0 is the permeability of free space, N is the number of turns density of the coil, and A is the area of ​​a single turn of the coil;

[0084] The formula for integral operation is:

[0085]

[0086] In the formula,

[0087] H(s) is the S-domain transfer function of the lossy integrator.

[0088] R1 is the input resistor.

[0089] R2 is a lossy attenuation resistor.

[0090] C is the integrating capacitor.

[0091] s is a complex variable.

[0092] By re-sampling the distorted waveform to extract data that reflects the distortion characteristics and eliminating the interference of erroneous data, the curve is smoothed through inversion operation, thereby making the distortion characteristics more prominent and improving the sensitivity of fault detection.

[0093] Step 2: Based on the comparison results of the collected temperatures with the corresponding normal temperature ranges, distinguish between high-voltage transformer faults and power system faults, and determine the type of high-voltage transformer fault; based on the comparison results of vibration amplitude with the set amplitude threshold, determine whether there is an installation fault in the high-voltage transformer; based on the comparison results of impedance value with the set threshold, determine whether there is a fault in the secondary circuit of the high-voltage transformer.

[0094] Specifically, in step 2, the body temperature of the high-voltage transformer, the temperature of the secondary side outgoing connector, and the temperature of the incoming bus are collected.

[0095] If the temperature of the transformer body and the temperature of the incoming bus are both within the set normal temperature range, but the temperature of the secondary side outgoing connector is not within the set normal temperature range, then the high voltage transformer secondary side outgoing connector is determined to be faulty.

[0096] If the temperature of the incoming bus is within the set normal temperature range, but the temperature of the transformer body and the temperature of the secondary side outgoing connector are not within the set normal temperature range, then it is determined to be an internal fault of the high voltage transformer.

[0097] If the temperature of the incoming bus is not within the set normal temperature range, it is determined to be a power system fault.

[0098] Preferably, the set normal temperature range is [T-Δt, T+Δt], where Δt is the set temperature deviation, which is 10℃, and T is the reference temperature, satisfying the following relationship:

[0099] T = T e +k×I

[0100] In the formula, T e Where is the ambient temperature, k is a constant greater than 0, and I is the load current.

[0101] In actual engineering projects, the normal temperature range is set according to the ambient temperature, the regulations and specifications, and the manufacturer's recommended operating temperature for the equipment.

[0102] Specifically, in step 2, the vibration amplitude of the high-voltage transformer is monitored, and the amplitude of the transformer body and the mounting base are collected. If the difference between the amplitude of the transformer body and the amplitude of the mounting base exceeds the set amplitude threshold, it is determined that there is an installation fault in the high-voltage transformer.

[0103] Specifically, the set amplitude threshold value ranges from greater than or equal to 0.05 mm to less than or equal to 0.10 mm.

[0104] Preferably, in step 2, a 5kHz high-frequency voltage signal is applied to the line between the secondary output port of the transformer and the input port of the meter to calculate the impedance values ​​of the secondary current inlet and outlet circuits; the calculated impedance values ​​are compared with the rated impedance values ​​calculated using the rated parameters of the transformer; if the deviation between the impedance values ​​and the rated impedance values ​​is greater than a set threshold, it is determined that there is a grounding or short-circuit fault in the secondary circuit of the high-voltage transformer.

[0105] Specifically, the threshold value is set at 5% of the impedance rating.

[0106] This invention compares the inverted waveform with the final output waveform. Based on the distortion of both, it determines whether the distorted waveform is caused by external signal interference or a fault in the high-voltage transformer itself, avoiding misjudgments due to external signal interference. After initially determining a fault in the equipment through the distorted waveform, multiple temperature sensors are used to monitor the high-voltage transformer body, the connectors of the high-voltage transformer secondary side outgoing lines, and the busbar of the high-voltage transformer incoming lines. This eliminates the influence of the power system operating load on the temperature of the high-voltage transformer operation, improving the diagnostic accuracy of the transformer fault. In parallel, multiple vibration sensors are used to monitor the high-voltage transformer body and mounting base. The difference in amplitude between the two is used to determine whether the high-voltage transformer is loosely installed, avoiding damage to the transformer due to severe vibration. Simultaneously, a high-frequency signal is applied to the current loop, and the input high-frequency current is compared with the high-frequency current flowing through the meter to achieve live detection of faults in the loop.

[0107] Especially when a high-frequency voltage signal is applied to the secondary circuit to calculate the impedance value of the secondary circuit, faults in the secondary circuit of the instrument transformer can be detected intuitively. Furthermore, the magnitude of the calculated impedance value can be used to distinguish between ground faults and short-circuit faults, making the fault detection results more intuitive and reliable.

[0108] The method proposed in this invention addresses the non-uniformity of faults in high-voltage transformers in practical engineering by simultaneously detecting temperature, amplitude, and high-frequency impedance, thereby enabling a more comprehensive investigation of various faults and improving the reliability of system operation.

[0109] This invention also proposes a fault detection device for the secondary circuit of a metering high-voltage transformer, such as... Figure 2 As shown, it includes: a main control unit, a waveform sampling unit, a temperature acquisition unit, a vibration acquisition unit, a high-frequency signal generation unit, and a high-frequency impedance measurement unit;

[0110] The main control unit is used to sample the voltage and current waveforms of the secondary circuit of the high-voltage transformer from the waveform sampling unit and to monitor voltage and current waveform distortion events. When a distorted waveform appears in the secondary circuit of the high-voltage transformer, the temperature acquisition unit is controlled to collect the body temperature of the high-voltage transformer, the temperature of the secondary side outgoing terminal, and the temperature of the incoming bus. The vibration acquisition unit is controlled to monitor the vibration amplitude of the high-voltage transformer. The high-frequency signal generation unit is controlled to apply a 5kHz high-frequency voltage signal to the line between the secondary outgoing port of the transformer and the incoming port of the meter. The high-frequency current signal measurement unit is controlled to calculate the impedance values ​​of the secondary current inlet and outlet circuits.

[0111] The main control unit is also used to distinguish between high-voltage transformer faults and power system faults based on the comparison results of various collected temperatures with the corresponding normal temperature ranges, and to determine the type of high-voltage transformer fault; to determine whether there is an installation fault in the high-voltage transformer based on the comparison results of the vibration amplitude with the set amplitude threshold; and to determine whether there is a fault in the secondary circuit of the high-voltage transformer based on the comparison results of the impedance value with the set threshold.

[0112] Preferably, the device further includes: an alarm unit, a storage unit, a display unit, and a communication unit;

[0113] The alarm unit is used to generate corresponding alarms based on the fault type output by the main control unit.

[0114] Storage unit, used to store collected data and processing results.

[0115] Preferably, the input terminal of the waveform sampling unit is connected to the input terminal of the open circuit detection unit, and the input terminal of the open circuit detection unit is connected to the secondary output terminal of the high voltage transformer.

[0116] The input terminal of the temperature acquisition unit is connected to the high voltage transformer body, the connector of the high voltage transformer secondary side output line, and the busbar of the high voltage transformer input line, respectively.

[0117] The input terminals of the vibration acquisition unit are connected to the body of the high-voltage transformer and the mounting base, respectively.

[0118] The input terminals of the high-frequency impedance measurement unit are connected to the secondary current inlet and outlet circuits, respectively.

[0119] The outputs of the open circuit detection unit, temperature acquisition unit, vibration acquisition unit, and high-frequency impedance measurement unit are connected to the main control unit through an OR gate logic circuit Y1.

[0120] Furthermore, the OR gate logic circuit is connected to the main control unit via an analog-to-digital converter.

[0121] Preferably, the open-circuit detection unit includes a first adjustable resistor R1, a second adjustable resistor R2, a voltage divider resistor R3, and a first operational amplifier U1 connected in series. One end of the first adjustable resistor is connected to the secondary output terminal of the high-voltage transformer, and the other end of the first adjustable resistor is connected to one end of the second adjustable resistor and one end of the voltage divider resistor. The other end of the second adjustable resistor is grounded, and the other end of the voltage divider resistor is connected to the inverting input terminal of the first operational amplifier. The non-inverting input terminal of the first operational amplifier receives a power frequency signal V0 that is opposite in direction to the secondary output signal of the high-voltage transformer.

[0122] The output of the first operational amplifier is connected to an OR gate logic circuit.

[0123] Preferably, the temperature acquisition unit includes a temperature sensor T1, a first digital-to-analog converter (D / A), and a second operational amplifier U2 connected in series.

[0124] There are multiple temperature sensors, each of which is installed on the high voltage transformer body, the connector of the secondary side output line of the high voltage transformer, and the busbar of the high voltage transformer input line. The output of each temperature sensor is connected to the first digital-to-analog converter. The output of the first digital-to-analog converter is connected to the inverting input of the second operational amplifier. The normal temperature range V1 is input to the non-inverting input of the second operational amplifier.

[0125] The output of the second operational amplifier is connected to an OR gate logic circuit.

[0126] Preferably, the vibration acquisition unit includes a vibration sensor C1, a second digital-to-analog converter (D / A), and a third operational amplifier U3 connected in series.

[0127] There are multiple vibration sensors, each of which is installed on the body and mounting base of the high voltage transformer. The output of each vibration sensor is connected to the second digital-to-analog converter. The output of the second digital-to-analog converter is connected to the inverting input of the third operational amplifier. The non-inverting input of the third operational amplifier is input with the set amplitude threshold.

[0128] The output of the third operational amplifier is connected to an OR gate logic circuit.

[0129] Preferably, the high-frequency impedance measurement unit includes: a high-frequency impedance generation circuit I1, a third digital-to-analog converter (D / A), and a fourth operational amplifier U4;

[0130] The high-frequency impedance generation circuit includes a high-frequency signal generator, a clamp-on current transformer, a signal conditioner, and a high-pass filter. The high-frequency signal generator is used to apply a high-frequency voltage signal between the current input and output circuits. The clamp-on current transformer is used to measure the secondary circuit current. The signal conditioner is used to filter out low-frequency signals from the mixed current signal. The input terminal of the signal conditioner is connected to the secondary winding of the clamp-on current transformer through an analog signal line, and the output terminal of the signal conditioner is connected to the input terminal of the high-pass filter through an analog signal line.

[0131] The output of the high-pass filter is connected to the input of the third digital-to-analog converter via a differential analog signal line; the output of the third digital-to-analog converter is connected to the inverting input of the fourth operational amplifier, and the non-inverting input of the fourth operational amplifier receives the set threshold.

[0132] The output of the fourth operational amplifier is connected to an OR gate logic circuit.

[0133] In this embodiment, the output of the ARM main control processor is connected to the display module, and the input is connected to the operation keyboard. The ARM processor is connected to the DDS frequency synthesizer via the SPI bus to control the high-frequency voltage signal generation part. It is connected to the DSP signal processor via the AD converter. The ARM main control processor calculates relevant parameters such as the impedance of the secondary circuit of the current transformer based on the AD conversion data. The measured parameters can be used to determine whether there is a grounding or short-circuit fault in the secondary circuit of the current transformer under test, as well as the display module and operation keyboard.

[0134] The applicant of this invention has provided a detailed description of the embodiments of the invention in conjunction with the accompanying drawings. However, those skilled in the art should understand that the above embodiments are merely preferred embodiments of the invention. The detailed description is only intended to help readers better understand the spirit of the invention and is not intended to limit the scope of protection of the invention. On the contrary, any improvements or modifications made based on the inventive spirit of the invention should fall within the scope of protection of the invention.

Claims

1. A method for detecting faults in the secondary circuit of a metering high-voltage transformer, characterized in that, The method includes: Step 1: When a distorted waveform appears in the secondary circuit of the high-voltage transformer, collect the body temperature of the high-voltage transformer, the temperature of the secondary side outgoing connector, and the temperature of the incoming busbar. Monitor the vibration amplitude of the high-voltage transformer and obtain the impedance values ​​of the secondary current inlet and outlet circuits under high-frequency voltage signals. Step 2: Based on the comparison results of the collected temperatures with the corresponding normal temperature ranges, distinguish between high-voltage transformer faults and power system faults, and determine the type of high-voltage transformer fault; based on the comparison results of vibration amplitude with the set amplitude threshold, determine whether there is an installation fault in the high-voltage transformer; based on the comparison results of impedance value with the set threshold, determine whether there is a fault in the secondary circuit of the high-voltage transformer. The normal temperature range is [T-Δt, T+Δt], where Δt is the set temperature deviation, taken as 10℃, and T is the reference temperature, satisfying the following relationship: T=T e +k×I In the formula, T e Where is the ambient temperature, k is a constant greater than 0, and I is the load current.

2. The method for detecting faults in the secondary circuit of a metering high-voltage transformer according to claim 1, characterized in that, In step 1, the voltage and current waveforms of the secondary circuit of the high-voltage transformer are sampled, and distortion events of the voltage and current waveforms are monitored. The distorted waveforms within a set interval before and after the distortion event are collected, and the collected distorted waveforms are sampled twice using the generalized polynomial interpolation method to obtain the distorted waveforms to be inverted. The distorted waveform to be inverted is inverted to obtain the inverted waveform. If the inverted waveform is distorted compared with the normal waveform, it is determined that there is a fault in the high voltage transformer. The relevant temperature is collected, the vibration amplitude is monitored, and the corresponding impedance value is obtained. If the inverted waveform is not distorted compared to the normal waveform, it is determined that there is signal interference in the high-voltage transformer.

3. The method for detecting faults in the secondary circuit of a metering high-voltage transformer according to claim 2, characterized in that, Inversion operations involve differentiation followed by integration. The differential formula is as follows: In the formula, e(t) represents the output voltage and current of the high-voltage transformer. i p (t) is a function of the primary current passing through the coil. M = μ0·N·A, where μ0 is the permeability of free space, N is the number of turns density of the coil, and A is the area of ​​a single turn of the coil; The formula for integral operation is: In the formula, H(s) is the S-domain transfer function of the lossy integrator. R1 is the input resistor. R2 is a lossy attenuation resistor. C is the integrating capacitor. s is a complex variable.

4. The method for detecting faults in the secondary circuit of a metering high-voltage transformer according to claim 2, characterized in that, In step 2, the body temperature of the high-voltage transformer, the temperature of the secondary side outgoing connector, and the temperature of the incoming busbar are collected. If the temperature of the transformer body and the temperature of the incoming bus are both within the set normal temperature range, but the temperature of the secondary side outgoing connector is not within the set normal temperature range, then the high voltage transformer secondary side outgoing connector is determined to be faulty. If the temperature of the incoming bus is within the set normal temperature range, but the temperature of the transformer body and the temperature of the secondary side outgoing connector are not within the set normal temperature range, then it is determined to be an internal fault of the high voltage transformer. If the temperature of the incoming bus is not within the set normal temperature range, it is determined to be a power system fault.

5. The method for detecting faults in the secondary circuit of a metering high-voltage transformer according to claim 4, characterized in that, The set temperature deviation is 10℃.

6. The method for detecting faults in the secondary circuit of a metering high-voltage transformer according to claim 2, characterized in that, In step 2, the vibration amplitude of the high-voltage transformer is monitored. The amplitude of the transformer body and the amplitude of the mounting base are collected. If the difference between the amplitude of the transformer body and the amplitude of the mounting base exceeds the set amplitude threshold, it is determined that there is an installation fault in the high-voltage transformer.

7. The method for detecting faults in the secondary circuit of a metering high-voltage transformer according to claim 6, characterized in that, The set amplitude threshold value ranges from greater than or equal to 0.05 mm to less than or equal to 0.10 mm.

8. The method for detecting faults in the secondary circuit of a metering high-voltage transformer according to claim 2, characterized in that, In step 2, a 5kHz high-frequency voltage signal is applied to the line between the secondary output port of the instrument transformer and the input port of the meter to calculate the impedance values ​​of the secondary current inlet and outlet circuits. The calculated impedance values ​​are compared with the rated impedance values ​​calculated using the rated parameters of the instrument transformer. If the deviation between the impedance values ​​and the rated impedance values ​​is greater than the set threshold, it is determined that there is a grounding or short-circuit fault in the secondary circuit of the high-voltage instrument transformer.

9. The method for detecting faults in the secondary circuit of a metering high-voltage transformer according to claim 8, characterized in that, The threshold value is set to 5% of the impedance rating.

10. A fault detection device for the secondary circuit of a metering high-voltage transformer, implementing the method described in any one of claims 1 to 9, comprising: The main control unit, waveform sampling unit, temperature acquisition unit, vibration acquisition unit, high-frequency signal generation unit, and high-frequency impedance measurement unit are characterized by: The main control unit is used to sample the voltage and current waveforms of the secondary circuit of the high-voltage transformer from the waveform sampling unit and to monitor voltage and current waveform distortion events. When a distorted waveform appears in the secondary circuit of the high-voltage transformer, the temperature acquisition unit is controlled to collect the body temperature of the high-voltage transformer, the temperature of the secondary side outgoing terminal, and the temperature of the incoming bus. The vibration acquisition unit is controlled to monitor the vibration amplitude of the high-voltage transformer. The high-frequency signal generation unit is controlled to apply a 5kHz high-frequency voltage signal to the line between the secondary outgoing port of the transformer and the incoming port of the meter. The high-frequency current signal measurement unit is controlled to calculate the impedance values ​​of the secondary current inlet and outlet circuits. The main control unit is also used to distinguish between high-voltage transformer faults and power system faults based on the comparison results of various collected temperatures with the corresponding normal temperature ranges, and to determine the type of high-voltage transformer fault; to determine whether there is an installation fault in the high-voltage transformer based on the comparison results of the vibration amplitude with the set amplitude threshold; and to determine whether there is a fault in the secondary circuit of the high-voltage transformer based on the comparison results of the impedance value with the set threshold.

11. The fault detection device for the secondary circuit of a metering high-voltage transformer according to claim 10, characterized in that, The device also includes: an alarm unit and a storage unit; The alarm unit is used to generate corresponding alarms based on the fault type output by the main control unit. Storage unit, used to store collected data and processing results.

12. The fault detection device for the secondary circuit of a metering high-voltage transformer according to claim 10, characterized in that, The input terminal of the waveform sampling unit is connected to the input terminal of the open circuit detection unit, and the input terminal of the open circuit detection unit is connected to the secondary output terminal of the high voltage transformer. The input terminal of the temperature acquisition unit is connected to the high voltage transformer body, the connector of the high voltage transformer secondary side output line, and the busbar of the high voltage transformer input line, respectively. The input terminals of the vibration acquisition unit are connected to the body of the high-voltage transformer and the mounting base, respectively. The input terminals of the high-frequency impedance measurement unit are connected to the secondary current inlet and outlet circuits, respectively. The outputs of the open circuit detection unit, temperature acquisition unit, vibration acquisition unit, and high-frequency impedance measurement unit are connected to the main control unit through an OR gate logic circuit.

13. The fault detection device for the secondary circuit of a metering high-voltage transformer according to claim 12, characterized in that, The open-circuit detection unit includes a first adjustable resistor, a second adjustable resistor, a voltage divider resistor, and a first operational amplifier connected in series. One end of the first adjustable resistor is connected to the secondary output terminal of the high-voltage transformer. The other end of the first adjustable resistor is connected to one end of the second adjustable resistor and one end of the voltage divider resistor. The other end of the second adjustable resistor is grounded. The other end of the voltage divider resistor is connected to the inverting input terminal of the first operational amplifier. The non-inverting input terminal of the first operational amplifier receives a power frequency signal that is opposite in direction to the secondary output signal of the high-voltage transformer. The output of the first operational amplifier is connected to an OR gate logic circuit.

14. The fault detection device for the secondary circuit of a metering high-voltage transformer according to claim 12, characterized in that, The temperature acquisition unit includes a temperature sensor, a first digital-to-analog converter, and a second operational amplifier connected in series. There are multiple temperature sensors, each of which is installed on the high voltage transformer body, the connector of the high voltage transformer secondary side output line, and the busbar of the high voltage transformer input line. The output of each temperature sensor is connected to the first digital-to-analog converter, the output of the first digital-to-analog converter is connected to the inverting input of the second operational amplifier, and the normal temperature range is input to the non-inverting input of the second operational amplifier. The output of the second operational amplifier is connected to an OR gate logic circuit.

15. The fault detection device for the secondary circuit of a metering high-voltage transformer according to claim 12, characterized in that, The vibration acquisition unit includes a vibration sensor, a second digital-to-analog converter, and a third operational amplifier connected in series. There are multiple vibration sensors, each of which is installed on the body and mounting base of the high voltage transformer. The output of each vibration sensor is connected to the second digital-to-analog converter. The output of the second digital-to-analog converter is connected to the inverting input of the third operational amplifier. The non-inverting input of the third operational amplifier is input with the set amplitude threshold. The output of the third operational amplifier is connected to an OR gate logic circuit.

16. The fault detection device for the secondary circuit of a metering high-voltage transformer according to claim 12, characterized in that, The high-frequency impedance measurement unit includes: a high-frequency impedance generation circuit, a third digital-to-analog converter, and a fourth operational amplifier; The high-frequency impedance generation circuit includes a high-frequency signal generator, a clamp-on current transformer, a signal conditioner, and a high-pass filter. The high-frequency signal generator is used to apply a high-frequency voltage signal between the current input and output circuits. The clamp-on current transformer is used to measure the secondary circuit current. The signal conditioner is used to filter out low-frequency signals from the mixed current signal. The input terminal of the signal conditioner is connected to the secondary winding of the clamp-on current transformer through an analog signal line, and the output terminal of the signal conditioner is connected to the input terminal of the high-pass filter through an analog signal line. The output of the high-pass filter is connected to the input of the third digital-to-analog converter via a differential analog signal line; the output of the third digital-to-analog converter is connected to the inverting input of the fourth operational amplifier, and the non-inverting input of the fourth operational amplifier receives the set threshold. The output of the fourth operational amplifier is connected to an OR gate logic circuit.

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