CN117517869A - Fault diagnosis system of high-voltage direct-current circuit - Google Patents
Fault diagnosis system of high-voltage direct-current circuit Download PDFInfo
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
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- G—PHYSICS
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- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The invention discloses a fault diagnosis system of a high-voltage direct current circuit, which relates to the technical field of circuit detection and adopts the following scheme that: a circuit fault detection unit and a circuit fault analysis unit; the circuit fault detection unit includes: the device comprises a voltage fluctuation detection module and a current abnormality detection module. According to the scheme of the direct current circuit fault detection system, in a circuit fault detection unit, faults possibly existing in a high-voltage direct current circuit are comprehensively checked from the aspects of voltage fluctuation detection, current abnormality detection, temperature abnormality detection, resistance measurement, waveform analysis, noise detection, vibration detection and insulation detection; and the detected fault information is screened, analyzed and positioned by means of a fault type identification module, a fault positioning module and a historical data comparison module in the circuit fault analysis unit, and faults and fault types of the circuit can be discovered quickly by combining historical data.
Description
Technical Field
The invention relates to the technical field of circuit detection, in particular to a fault diagnosis system of a high-voltage direct current circuit.
Background
With the continuous development of technology, hvdc transmission has become the dominant technology of electric power systems. With the development of the high-voltage dc circuit, the failure rate of the dc power transmission circuit is gradually increased. The high-voltage direct-current transmission system has more fault types and mainly comprises the following steps: a short-circuit fault between the DC electrodes, a DC voltage reduction fault, a DC current abnormal fault, a DC electrode work abnormal fault, etc.
However, in general, the detection of faults in a high-voltage direct current circuit is to monitor and detect the system by installing various sensors and detection devices, for example, a current transformer and a voltage transformer are installed to monitor the changes of direct current and voltage, but the detected data are often more one-sided, the fault data are often concentrated on two main aspects of current and voltage, and abnormal temperatures, abnormal resistances and the like of outgoing lines in the circuit can also affect the circuit and are factors for generating circuit faults. Aiming at the more implicit detection in the circuit, the invention provides a fault diagnosis system of a high-voltage direct-current circuit.
Disclosure of Invention
In view of the above drawbacks, the present invention provides a fault diagnosis system for a high-voltage dc circuit, comprising the following components:
a circuit fault detection unit and a circuit fault analysis unit;
the circuit fault detection unit includes: the device comprises a voltage fluctuation detection module, a current abnormality detection module, a temperature abnormality detection module, a resistance measurement module, a waveform analysis module, a noise detection module, a vibration detection module and an insulation detection module;
the circuit fault analysis unit includes: the system comprises a fault type identification module, a fault positioning module and a historical data comparison module.
In the above technical solution of a fault diagnosis system for a high voltage direct current circuit, preferably, the voltage fluctuation detection module specifically includes: the voltage fluctuation refers to irregular change of voltage in a certain range, an oscilloscope and a data acquisition device tool are connected on a high-voltage direct-current circuit, and whether the voltage fluctuation is in an allowable range is judged by observing voltage waveforms on the oscilloscope;
the data collector comprises any one of a bus system data collector, an Internet of things data collector, an Ethernet data collector, an anti-interference channel isolation type data collector, an AD conversion data collector, a DA conversion data collector, an analog quantity data collector and a digital quantity data collector, and the data collector provides accurate data for technicians by monitoring voltage fluctuation conditions in real time;
the fluctuation voltage is generally regarded as amplitude-modulated wave which takes the power frequency rated voltage as a carrier wave and the amplitude of the voltage is modulated by the voltage fluctuation component with the frequency range of 0.05Hz-35Hz, so that the detection method of the voltage fluctuation component adopts a demodulation method of a high-power carrier modulation signal in a communication theory, the modulated signal is multiplied by a periodic signal which is in the same frequency and phase with the carrier signal, the voltage fluctuation component is separated from the power frequency carrier voltage, and the fluctuation component is obtained through a band-pass filter;
in consideration of the voltage fluctuation component, a series of amplitude modulation waves are superimposed on the fundamental wave voltage, so that the analysis is simplified and the generality is not lost, and the detection method for researching the voltage fluctuation can analyze the modulation of the amplitude modulation waves with a single frequency on the power frequency carrier wave, and generally, a square demodulation detection method, a full-wave rectification detection method and a half-wave effective value detection method are used.
In the above technical solution of the fault diagnosis system for a high voltage dc circuit, preferably, the current abnormality detection module specifically includes: the clamp meter, the oscilloscope tool and the clamp meter are used for measuring the real-time current in the circuit, the oscilloscope can display the current waveform, and the technician is helped to judge whether the abnormality exists;
the low-end current detection mode adds an extra wire winding resistance in the ground wire loop, and the high-end current detection mode needs to process larger common mode signals;
the high-side current sensing circuit typically requires a precision op-amp and some precision resistor-capacitor, and the most commonly used high-side current sensing circuit uses a differential op-amp for gain amplification and shifting the signal level from the high-side to the reference ground.
In the above technical solution of the fault diagnosis system for a high voltage dc circuit, preferably, the temperature anomaly detection module specifically includes: the temperature anomaly detection is realized by using an infrared thermometer and a temperature sensor tool. The infrared thermometer can measure the surface temperature of the circuit in a non-contact manner, and the temperature sensor monitors the temperature change in real time;
furthermore, a thermistor circuit is provided in the hvdc circuit, and in order to measure an accurate signal, a differential input should be used instead of a single-ended input; the differential input can eliminate common noise and can reach the sensitivity of mu V level; the accuracy of the measurement depends mainly on the accuracy of Rref, in order to overcome this problem in voltage excitation, the thermistor uses a constant current source instead of a voltage source;
when using a constant current source, the voltage drop across the thermistor depends only on its resistance value and the constant current source value, however, the accuracy of the measurement when using constant current source excitation depends on the accuracy of the current source, since a precise temperature measurement work is performed, the DAC current should be calibrated by the TIA.
In the above technical solution of a fault diagnosis system for a high voltage direct current circuit, preferably, the resistance measurement module specifically includes: mainly by means of a multimeter and a megger tool; the universal meter can measure the resistance value, and the rocking meter can measure the insulation resistance value;
the current detection circuit using the shunt resistor is a simple circuit that measures only voltage, but since the voltage drop of the shunt resistor is small, a circuit that can amplify voltage with high accuracy needs to be fabricated; the circuit current value is detected using a current detection circuit, the voltage value is measured with an oscilloscope and the current flowing direction is observed, and a load is connected to the completed current detection circuit and the detected waveform is observed.
In the above technical solution of the fault diagnosis system for a high voltage dc circuit, preferably, the waveform analysis module specifically includes: the common waveform types in the high-voltage direct current circuit comprise sine waves, square waves and triangular waves, and whether the circuit has faults or not is judged by analyzing the waveforms; the waveform analysis mainly uses an oscilloscope tool, the oscilloscope can display voltage or current waveforms, analyze the shape, amplitude and frequency characteristics of the waveforms and judge whether the circuit is abnormal or not;
the DC circuit waveform is analyzed by adopting a bridge rectifier circuit part, the defects that a full-wave rectifier circuit requires a transformer secondary to have a center tap and a diode to bear large back pressure are overcome, the pulsating voltage flowing through a load contains a DC component and an AC component, the pulsating voltage can be subjected to Fourier analysis, the amplitude of a second harmonic in the harmonic component is the largest, and the ratio of the amplitude of the lowest harmonic to the average value is called as a pulsating coefficient S, and the smaller S is the better.
In the above technical solution of the fault diagnosis system for a high voltage direct current circuit, preferably, the noise detection module specifically includes: judging whether mechanical faults or other abnormal conditions exist or not by monitoring and analyzing noise in the running process of equipment connected with a direct current circuit;
the method comprises the steps of observing key point waveforms in a circuit through an oscilloscope, slowly injecting test signals into the circuit from back to front, detecting abnormality according to output signal waveforms of the oscilloscope, and indicating that a front circuit has faults if the signal waveforms are abnormal;
the components of the connecting circuit are gradually removed by a segmentation method in a step-by-step detection way, a noise-free part is found out, then a noise source is found and determined, in the detection, the circuit is separated from the front to the back, and the detection can be specifically completed by a mode of short wires on a circuit board and pulling out part of plug-ins, wherein the noise-free part is the source of noise;
static measurement is carried out through a universal meter, and faults can be detected through direct current working current and voltage of the universal meter;
the vibration detection module specifically comprises: judging whether mechanical faults or other abnormal conditions exist or not by monitoring and analyzing vibration in the running process of the equipment;
the insulation detection module specifically comprises: monitoring the insulation performance of the equipment;
wherein, the detected voltages of the positive and negative buses of the column circuit are displayed by the liquid crystal on-line detection. Setting U+ and U-to represent positive electrode voltage and negative electrode voltage, wherein Uz is a voltage setting value, and Uz is more than 0;
when |U+| < Uz, |U- | > Uz, the positive electrode insulation is reduced;
when |U+ | > Uz, |U- | < Uz, the negative electrode insulation is reduced;
when the absolute value of U is smaller than the absolute value of Uz, the absolute value of U-is smaller than the absolute value of Uz, and the insulation of the positive electrode and the negative electrode is reduced;
after judging insulation drop through the detection voltage, starting a detection current unit to determine which branch insulation drops;
detecting the insulation resistance of the positive electrode and the negative electrode to the ground, and respectively and automatically throwing the detection resistance into the positive electrode bus and the negative electrode bus under the condition of ensuring no influence on a circuit system;
grounding a plurality of branches, putting a detection resistor R into a negative bus, and detecting all branches with reduced insulation; the insulation of the negative electrode is reduced, and an insulation resistor R is added to the positive bus, so that all insulation reduced branches can be detected; when the positive and negative insulation of the same branch is reduced equally or reduced proportionally, the positive and negative detection resistors are respectively put into the direct current bus, and the leakage current value of each branch of the positive and negative poles can be detected.
In the above technical solution of a fault diagnosis system for a high voltage direct current circuit, preferably, the fault type identification module specifically includes: common fault types include overvoltage, undervoltage, short circuit, open circuit, etc., overvoltage faults refer to voltages exceeding a normal range, which may cause component damage; undervoltage faults refer to voltages below the normal range, which may lead to reduced system performance; the short circuit fault refers to the fact that current directly flows without passing through a load, and the safety problems such as fire disaster and the like can be caused; open circuit failure refers to disconnection in a circuit, which results in no current flow;
the fault type comprises the following steps:
a short circuit fault of the converter valve; alternating current side alternately generates two-phase short circuit and three-phase short circuit; the current through the faulty valve reverses and increases dramatically; the current on the alternating current side is increased greatly and is many times greater than the normal working current; the direct current side is not much reduced in a short time due to the action of the smoothing reactor; the voltage of a direct current bus of the converter bridge is reduced;
commutation failure is not easy to cause because the rectifier bears reverse voltage in most of the time, but commutation failure is easy to cause because the inverter bears forward voltage in most of the time, such as short circuit of an inverter converter valve, loss of trigger pulse, and failure of an alternating current system can cause commutation failure;
the control system fault causes a valve false opening and a valve non-opening fault, and the direct current control system fault causes abnormal trigger pulse, so that the converter works abnormally, and the valve false opening or the valve non-opening fault occurs;
the direct current switch field equipment faults mainly comprise high-voltage direct current pole bus faults, neutral bus faults, direct current filter faults, direct current wiring mode change-over switch faults and smoothing reactor body faults;
the grounding electrode fault mainly comprises a grounding electrode bus fault, a grounding electrode line fault and an in-station grounding network fault;
in general, when the dc line is short-circuited to the ground, the dc voltage drop and the dc current rise are detected from the rectifying side and the dc voltage and the dc current drop are detected from the inverting side, because the dc line is long in the dc line fault.
In the above technical solution of the fault diagnosis system for a high voltage direct current circuit, preferably, the fault location module specifically includes: in the live positioning process, a monitoring tool such as an oscilloscope and a data collector is used for determining the fault position, and the waveform on the oscilloscope or the data in the data collector are observed to judge which part of the circuit has a problem; in addition, a sectional checking method can be adopted to gradually narrow the fault range and finally find out the fault point;
in the live positioning process, pulse signals are input into the circuit, the condition that signals are transmitted in each part Huang Zijian in the circuit is checked step by using an oscilloscope or a voltmeter and other instruments from the front stage to the rear stage according to the flow of the signals, whether the functions of the ID safety circuit are normal or not is analyzed, and therefore the position of the fault is judged.
In the above technical solution of a fault diagnosis system for a high-voltage direct current circuit, preferably, the historical data comparison module specifically includes: by collecting and comparing historical data, the operation condition and development trend of the circuit are known, for example, by comparing current and voltage data in different time periods, whether the circuit is abnormal or not is judged.
Compared with the prior art, the fault diagnosis system of the high-voltage direct current circuit has the following beneficial effects:
according to the scheme of the direct current circuit fault detection system, in a circuit fault detection unit, faults possibly existing in a high-voltage direct current circuit are comprehensively checked from the aspects of voltage fluctuation detection, current abnormality detection, temperature abnormality detection, resistance measurement, waveform analysis, noise detection, vibration detection and insulation detection; and the detected fault information is screened, analyzed and positioned by means of a fault type identification module, a fault positioning module and a historical data comparison module in the circuit fault analysis unit, and faults and fault types of the circuit can be discovered quickly by combining historical data.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description will make brief description and illustrations of the drawings used in the description of the embodiments of the present invention or the prior art. It is obvious that the drawings in the following description are only some embodiments of the present invention and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.
Fig. 1 is a schematic diagram of a fault diagnosis system of a hvdc circuit according to the present invention.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is apparent that the embodiments described below are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. In order to make the explanation and the description of the technical solution and the implementation of the present invention clearer, several preferred embodiments for implementing the technical solution of the present invention are described below.
Specific examples:
reference is made to fig. 1; the fault diagnosis system of the high-voltage direct current circuit comprises:
a circuit fault detection unit and a circuit fault analysis unit;
the circuit fault detection unit includes: the device comprises a voltage fluctuation detection module, a current abnormality detection module, a temperature abnormality detection module, a resistance measurement module, a waveform analysis module, a noise detection module, a vibration detection module and an insulation detection module; the circuit fault analysis unit includes: the system comprises a fault type identification module, a fault positioning module and a historical data comparison module.
The voltage fluctuation refers to irregular change of voltage in a certain range, an oscilloscope and a data acquisition device tool are connected on a high-voltage direct-current circuit, and whether the voltage fluctuation is in an allowable range is judged by observing voltage waveforms on the oscilloscope; the data collector comprises any one of a bus system data collector, an Internet of things data collector, an Ethernet data collector, an anti-interference channel isolation type data collector, an AD conversion data collector, a DA conversion data collector, an analog quantity data collector and a digital quantity data collector, and the data collector provides accurate data for technicians by monitoring voltage fluctuation conditions in real time;
the fluctuation voltage is generally regarded as amplitude-modulated wave which takes the power frequency rated voltage as a carrier wave and the amplitude of the voltage is modulated by the voltage fluctuation component with the frequency range of 0.05Hz-35Hz, so that the detection method of the voltage fluctuation component adopts a demodulation method of a high-power carrier modulation signal in a communication theory, the modulated signal is multiplied by a periodic signal which is in the same frequency and phase with the carrier signal, the voltage fluctuation component is separated from the power frequency carrier voltage, and the fluctuation component is obtained through a band-pass filter;
in consideration of the voltage fluctuation component, a series of amplitude modulation waves are superimposed on the fundamental wave voltage, so that the analysis is simplified and the generality is not lost, and the detection method for researching the voltage fluctuation can analyze the modulation of the amplitude modulation waves with a single frequency on the power frequency carrier wave, and generally, a square demodulation detection method, a full-wave rectification detection method and a half-wave effective value detection method are used.
The current abnormality detection module specifically comprises: the clamp meter, the oscilloscope tool and the clamp meter are used for measuring the real-time current in the circuit, the oscilloscope can display the current waveform, and the technician is helped to judge whether the abnormality exists;
the low-end current detection mode adds an extra wire winding resistance in the ground wire loop, and the high-end current detection mode needs to process larger common mode signals; the high-side current sensing circuit typically requires a precision op-amp and some precision resistor-capacitor, and the most commonly used high-side current sensing circuit uses a differential op-amp for gain amplification and shifting the signal level from the high-side to the reference ground.
The temperature anomaly detection module specifically comprises: the temperature anomaly detection is realized by using an infrared thermometer and a temperature sensor tool, the infrared thermometer can be used for measuring the surface temperature of a circuit in a non-contact manner, and the temperature sensor is used for monitoring the temperature change in real time;
furthermore, a thermistor circuit is provided in the hvdc circuit, and in order to measure an accurate signal, a differential input should be used instead of a single-ended input; the differential input can eliminate common noise and can reach the sensitivity of mu V level; the accuracy of the measurement depends mainly on the accuracy of Rref, in order to overcome this problem in voltage excitation, the thermistor uses a constant current source instead of a voltage source; when using a constant current source, the voltage drop across the thermistor depends only on its resistance value and the constant current source value, however, the accuracy of the measurement when using constant current source excitation depends on the accuracy of the current source, since a precise temperature measurement work is performed, the DAC current should be calibrated by the TIA.
By means of a multimeter and a megger tool; the universal meter can measure the resistance value, and the rocking meter can measure the insulation resistance value; the current detection circuit using the shunt resistor is a simple circuit that measures only voltage, but since the voltage drop of the shunt resistor is small, a circuit that can amplify voltage with high accuracy needs to be fabricated; the circuit current value is detected using a current detection circuit, the voltage value is measured with an oscilloscope and the current flowing direction is observed, and a load is connected to the completed current detection circuit and the detected waveform is observed.
The common waveform types in the high-voltage direct current circuit comprise sine waves, square waves and triangular waves, and whether the circuit has faults or not is judged by analyzing the waveforms; the waveform analysis mainly uses an oscilloscope tool, the oscilloscope can display voltage or current waveforms, analyze the shape, amplitude and frequency characteristics of the waveforms and judge whether the circuit is abnormal or not;
the DC circuit waveform is analyzed by adopting a bridge rectifier circuit part, the defects that a full-wave rectifier circuit requires a transformer secondary to have a center tap and a diode to bear large back pressure are overcome, the pulsating voltage flowing through a load contains a DC component and an AC component, the pulsating voltage can be subjected to Fourier analysis, the amplitude of a second harmonic in the harmonic component is the largest, and the ratio of the amplitude of the lowest harmonic to the average value is called as a pulsating coefficient S, and the smaller S is the better.
Judging whether mechanical faults or other abnormal conditions exist or not by monitoring and analyzing noise in the running process of equipment connected with a direct current circuit; the critical point waveform in the circuit is observed through the oscilloscope, the test signal is slowly injected into the circuit from back to front, then the abnormality is detected according to the output signal waveform of the oscilloscope, and if the signal waveform shows abnormality, the fault of the front circuit is indicated.
The components of the connecting circuit are gradually removed by a segmentation method in a step-by-step detection way, a noise-free part is found out, then a noise source is found and determined, in the detection, the circuit is separated from the front to the back, and the detection can be specifically completed by a mode of short wires on a circuit board and pulling out part of plug-ins, wherein the noise-free part is the source of noise;
static measurement is carried out through a universal meter, and faults can be detected through direct current working current and voltage of the universal meter; judging whether mechanical faults or other abnormal conditions exist or not by monitoring and analyzing vibration in the running process of the equipment;
the insulation detection module specifically comprises: monitoring the insulation performance of the equipment;
wherein, the detected voltages of the positive and negative buses of the column circuit are displayed by the liquid crystal on-line detection. Setting U+ and U-to represent positive electrode voltage and negative electrode voltage, wherein Uz is a voltage setting value, and Uz is more than 0;
when |U+| < Uz, |U- | > Uz, the positive electrode insulation is reduced;
when |U+ | > Uz, |U- | < Uz, the negative electrode insulation is reduced;
when the absolute value of U is smaller than the absolute value of Uz, the absolute value of U-is smaller than the absolute value of Uz, and the insulation of the positive electrode and the negative electrode is reduced;
after judging insulation drop through the detection voltage, starting a detection current unit to determine which branch insulation drops; detecting the insulation resistance of the positive electrode and the negative electrode to the ground, and respectively and automatically throwing the detection resistance into the positive electrode bus and the negative electrode bus under the condition of ensuring no influence on a circuit system; grounding a plurality of branches, putting a detection resistor R into a negative bus, and detecting all branches with reduced insulation; the insulation of the negative electrode is reduced, and an insulation resistor R is added to the positive bus, so that all insulation reduced branches can be detected; when the positive and negative insulation of the same branch is reduced equally or reduced proportionally, the positive and negative detection resistors are respectively put into the direct current bus, and the leakage current value of each branch of the positive and negative poles can be detected.
Common fault types include overvoltage, undervoltage, short circuit, open circuit, etc., overvoltage faults refer to voltages exceeding a normal range, which may cause component damage; undervoltage faults refer to voltages below the normal range, which may lead to reduced system performance; the short circuit fault refers to the fact that current directly flows without passing through a load, and the safety problems such as fire disaster and the like can be caused; open circuit failure refers to disconnection in a circuit, which results in no current flow;
the fault types include: a short circuit fault of the converter valve; alternating current side alternately generates two-phase short circuit and three-phase short circuit; the current through the faulty valve reverses and increases dramatically; the current on the alternating current side is increased greatly and is many times greater than the normal working current; the direct current side is not much reduced in a short time due to the action of the smoothing reactor; the voltage of a direct current bus of the converter bridge is reduced; commutation failure is not easy to cause because the rectifier bears reverse voltage in most of the time, but the inverter bears forward voltage in most of the time, such as short circuit of inverter converter valve, loss of trigger pulse, failure of AC system and the like, all cause commutation failure.
The control system fault causes a valve false opening and a valve non-opening fault, and the direct current control system fault causes abnormal trigger pulse, so that the converter works abnormally, and the valve false opening or the valve non-opening fault occurs; the direct current switch field equipment faults mainly comprise high-voltage direct current pole bus faults, neutral bus faults, direct current filter faults, direct current wiring mode change-over switch faults and smoothing reactor body faults; the grounding electrode fault mainly comprises a grounding electrode bus fault, a grounding electrode line fault and an in-station grounding network fault; in general, when the dc line is short-circuited to the ground, the dc voltage drop and the dc current rise are detected from the rectifying side and the dc voltage and the dc current drop are detected from the inverting side, because the dc line is long in the dc line fault.
In the live positioning process, a monitoring tool such as an oscilloscope and a data collector is used for determining the fault position, and the waveform on the oscilloscope or the data in the data collector are observed to judge which part of the circuit has a problem; in addition, a sectional checking method can be adopted to gradually narrow the fault range and finally find out the fault point;
in the live positioning process, pulse signals are input into the circuit, the condition that signals are transmitted in each part Huang Zijian in the circuit is checked step by using an oscilloscope or a voltmeter and other instruments from the front stage to the rear stage according to the flow of the signals, whether the functions of the ID safety circuit are normal or not is analyzed, and therefore the position of the fault is judged. By collecting and comparing historical data, the operation condition and development trend of the circuit are known, for example, by comparing current and voltage data in different time periods, whether the circuit is abnormal or not is judged.
Finally, it should be further noted that the structures, proportions, sizes, etc. shown in the drawings are merely for the purpose of understanding and reading the disclosure, and are not intended to limit the applicable limitations of the present application, so that any structural modifications, proportional changes, or adjustments of sizes may be made without affecting the efficacy or achievement of the present application and are within the scope of what is disclosed herein. The present invention is not limited to the above-mentioned preferred embodiments, and any person who can learn the structural changes made under the teaching of the present invention can fall within the scope of the present invention if the present invention has the same or similar technical solutions.
Claims (10)
1. A fault diagnosis system of a high-voltage direct current circuit comprises the following units:
a circuit fault detection unit and a circuit fault analysis unit;
the circuit fault detection unit includes: the device comprises a voltage fluctuation detection module, a current abnormality detection module, a temperature abnormality detection module, a resistance measurement module, a waveform analysis module, a noise detection module, a vibration detection module and an insulation detection module;
the circuit fault analysis unit includes: the system comprises a fault type identification module, a fault positioning module and a historical data comparison module.
2. The fault diagnosis system of a high voltage direct current circuit according to claim 1, wherein the voltage fluctuation detection module specifically comprises: the voltage fluctuation refers to irregular change of voltage in a certain range, an oscilloscope and a data acquisition device tool are connected on a high-voltage direct-current circuit, and whether the voltage fluctuation is in an allowable range is judged by observing voltage waveforms on the oscilloscope;
the data collector comprises any one of a bus system data collector, an Internet of things data collector, an Ethernet data collector, an anti-interference channel isolation type data collector, an AD conversion data collector, a DA conversion data collector, an analog quantity data collector and a digital quantity data collector, and the data collector provides accurate data for technicians by monitoring voltage fluctuation conditions in real time;
the fluctuation voltage is generally regarded as amplitude-modulated wave which takes the power frequency rated voltage as a carrier wave and the amplitude of the voltage is modulated by the voltage fluctuation component with the frequency range of 0.05Hz-35Hz, so that the detection method of the voltage fluctuation component adopts a demodulation method of a high-power carrier modulation signal in a communication theory, the modulated signal is multiplied by a periodic signal which is in the same frequency and phase with the carrier signal, the voltage fluctuation component is separated from the power frequency carrier voltage, and the fluctuation component is obtained through a band-pass filter;
in consideration of the voltage fluctuation component, a series of amplitude modulation waves are superimposed on the fundamental wave voltage, so that the analysis is simplified and the generality is not lost, and the detection method for researching the voltage fluctuation can analyze the modulation of the amplitude modulation waves with a single frequency on the power frequency carrier wave, and generally, a square demodulation detection method, a full-wave rectification detection method and a half-wave effective value detection method are used.
3. The fault diagnosis system of a high voltage direct current circuit according to claim 1, wherein the current abnormality detection module specifically comprises: the clamp meter, the oscilloscope tool and the clamp meter are used for measuring the real-time current in the circuit, the oscilloscope can display the current waveform, and the technician is helped to judge whether the abnormality exists;
the low-end current detection mode adds an extra wire winding resistance in the ground wire loop, and the high-end current detection mode needs to process larger common mode signals;
the high-side current sensing circuit typically requires a precision op-amp and some precision resistor-capacitor, and the most commonly used high-side current sensing circuit uses a differential op-amp for gain amplification and shifting the signal level from the high-side to the reference ground.
4. The fault diagnosis system of a high voltage direct current circuit according to claim 1, wherein the temperature abnormality detection module specifically comprises: the temperature anomaly detection is realized by using an infrared thermometer and a temperature sensor tool, the infrared thermometer can be used for measuring the surface temperature of a circuit in a non-contact manner, and the temperature sensor is used for monitoring the temperature change in real time;
furthermore, a thermistor circuit is provided in the hvdc circuit, and in order to measure an accurate signal, a differential input should be used instead of a single-ended input; the differential input can eliminate common noise and can reach the sensitivity of mu V level; the accuracy of the measurement depends mainly on the accuracy of Rref, in order to overcome this problem in voltage excitation, the thermistor uses a constant current source instead of a voltage source;
when using a constant current source, the voltage drop across the thermistor depends only on its resistance value and the constant current source value, however, the accuracy of the measurement when using constant current source excitation depends on the accuracy of the current source, since a precise temperature measurement work is performed, the DAC current should be calibrated by the TIA.
5. The fault diagnosis system of a high voltage direct current circuit according to claim 1, wherein the resistance measurement module specifically comprises: mainly by means of a multimeter and a megger tool; the universal meter can measure the resistance value, and the rocking meter can measure the insulation resistance value;
the current detection circuit using the shunt resistor is a simple circuit that measures only voltage, but since the voltage drop of the shunt resistor is small, a circuit that can amplify voltage with high accuracy needs to be fabricated; the circuit current value is detected using a current detection circuit, the voltage value is measured with an oscilloscope and the current flowing direction is observed, and a load is connected to the completed current detection circuit and the detected waveform is observed.
6. The fault diagnosis system of a high voltage direct current circuit according to claim 1, wherein the waveform analysis module specifically comprises: the common waveform types in the high-voltage direct current circuit comprise sine waves, square waves and triangular waves, and whether the circuit has faults or not is judged by analyzing the waveforms; the waveform analysis mainly uses an oscilloscope tool, the oscilloscope can display voltage or current waveforms, analyze the shape, amplitude and frequency characteristics of the waveforms and judge whether the circuit is abnormal or not;
the DC circuit waveform is analyzed by adopting a bridge rectifier circuit part, the defects that a full-wave rectifier circuit requires a transformer secondary to have a center tap and a diode to bear large back pressure are overcome, the pulsating voltage flowing through a load contains a DC component and an AC component, the pulsating voltage can be subjected to Fourier analysis, the amplitude of a second harmonic in the harmonic component is the largest, and the ratio of the amplitude of the lowest harmonic to the average value is called as a pulsating coefficient S, and the smaller S is the better.
7. The fault diagnosis system of a high voltage direct current circuit according to claim 1, wherein the noise detection module specifically comprises: judging whether mechanical faults or other abnormal conditions exist or not by monitoring and analyzing noise in the running process of equipment connected with a direct current circuit;
the method comprises the steps of observing key point waveforms in a circuit through an oscilloscope, slowly injecting test signals into the circuit from back to front, detecting abnormality according to output signal waveforms of the oscilloscope, and indicating that a front circuit has faults if the signal waveforms are abnormal;
the components of the connecting circuit are gradually removed by a segmentation method in a step-by-step detection way, a noise-free part is found out, then a noise source is found and determined, in the detection, the circuit is separated from the front to the back, and the detection can be specifically completed by a mode of short wires on a circuit board and pulling out part of plug-ins, wherein the noise-free part is the source of noise;
static measurement is carried out through a universal meter, and faults can be detected through direct current working current and voltage of the universal meter;
the vibration detection module specifically comprises: judging whether mechanical faults or other abnormal conditions exist or not by monitoring and analyzing vibration in the running process of the equipment;
the insulation detection module specifically comprises: monitoring the insulation performance of the equipment;
wherein, the detected voltages of the positive and negative buses of the column circuit are displayed by the liquid crystal on-line detection. Setting U+ and U-to represent positive electrode voltage and negative electrode voltage, wherein Uz is a voltage setting value, and Uz is more than 0;
when |U+| < Uz, |U- | > Uz, the positive electrode insulation is reduced;
when |U+ | > Uz, |U- | < Uz, the negative electrode insulation is reduced;
when the absolute value of U is smaller than the absolute value of Uz, the absolute value of U-is smaller than the absolute value of Uz, and the insulation of the positive electrode and the negative electrode is reduced;
after judging insulation drop through the detection voltage, starting a detection current unit to determine which branch insulation drops;
detecting the insulation resistance of the positive electrode and the negative electrode to the ground, and respectively and automatically throwing the detection resistance into the positive electrode bus and the negative electrode bus under the condition of ensuring no influence on a circuit system;
grounding a plurality of branches, putting a detection resistor R into a negative bus, and detecting all branches with reduced insulation; the insulation of the negative electrode is reduced, and an insulation resistor R is added to the positive bus, so that all insulation reduced branches can be detected; when the positive and negative insulation of the same branch is reduced equally or reduced proportionally, the positive and negative detection resistors are respectively put into the direct current bus, and the leakage current value of each branch of the positive and negative poles can be detected.
8. The fault diagnosis system of a high voltage direct current circuit according to claim 1, wherein the fault type identification module specifically comprises: common fault types include overvoltage, undervoltage, short circuit, open circuit, etc., overvoltage faults refer to voltages exceeding a normal range, which may cause component damage; undervoltage faults refer to voltages below the normal range, which may lead to reduced system performance; the short circuit fault refers to the fact that current directly flows without passing through a load, and the safety problems such as fire disaster and the like can be caused; open circuit failure refers to disconnection in a circuit, which results in no current flow;
the fault type comprises the following steps:
a short circuit fault of the converter valve; alternating current side alternately generates two-phase short circuit and three-phase short circuit; the current through the faulty valve reverses and increases dramatically; the current on the alternating current side is increased greatly and is many times greater than the normal working current; the direct current side is not much reduced in a short time due to the action of the smoothing reactor; the voltage of a direct current bus of the converter bridge is reduced;
commutation failure is not easy to cause because the rectifier bears reverse voltage in most of the time, but commutation failure is easy to cause because the inverter bears forward voltage in most of the time, such as short circuit of an inverter converter valve, loss of trigger pulse, and failure of an alternating current system can cause commutation failure;
the control system fault causes a valve false opening and a valve non-opening fault, and the direct current control system fault causes abnormal trigger pulse, so that the converter works abnormally, and the valve false opening or the valve non-opening fault occurs;
the direct current switch field equipment faults mainly comprise high-voltage direct current pole bus faults, neutral bus faults, direct current filter faults, direct current wiring mode change-over switch faults and smoothing reactor body faults;
the grounding electrode fault mainly comprises a grounding electrode bus fault, a grounding electrode line fault and an in-station grounding network fault;
in general, when the dc line is short-circuited to the ground, the dc voltage drop and the dc current rise are detected from the rectifying side and the dc voltage and the dc current drop are detected from the inverting side, because the dc line is long in the dc line fault.
9. The fault diagnosis system of a high voltage direct current circuit according to claim 1, wherein the fault locating module specifically comprises: in the live positioning process, a monitoring tool such as an oscilloscope and a data collector is used for determining the fault position, and the waveform on the oscilloscope or the data in the data collector are observed to judge which part of the circuit has a problem; in addition, a sectional checking method can be adopted to gradually narrow the fault range and finally find out the fault point;
in the live positioning process, pulse signals are input into the circuit, the condition that signals are transmitted in each part Huang Zijian in the circuit is checked step by using an oscilloscope or a voltmeter and other instruments from the front stage to the rear stage according to the flow of the signals, whether the functions of the ID safety circuit are normal or not is analyzed, and therefore the position of the fault is judged.
10. The fault diagnosis system of a high voltage direct current circuit according to claim 1, wherein the historical data comparison module specifically comprises: by collecting and comparing historical data, the operation condition and development trend of the circuit are known, for example, by comparing current and voltage data in different time periods, whether the circuit is abnormal or not is judged.
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| CN202311623829.2A CN117517869A (en) | 2023-11-30 | 2023-11-30 | Fault diagnosis system of high-voltage direct-current circuit |
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