CN113311376B - A synthetic pulse detection method for CVT - Google Patents

Abstract

The present invention discloses a synthetic pulse detection method for CVT, comprising the following steps: using a fault-free standard CVT to debug a synthetic pulse detection device; using the debugged synthetic pulse detection device to detect the CVT to be tested. The present invention designs three frequency point signals to approximately synthesize a square wave signal, which has the advantage of making full use of the characteristics of easy generation and high repeatability of sine waves, so that the synthesized square wave has a high degree of repeatability. The synthesis of three frequency points is also conducive to reducing the impact current and the power of the test source.

Description

A synthetic pulse detection method for CVT

Technical Field

The invention relates to the technical field of capacitive voltage transformer (CVT) detection, and in particular to a synthetic pulse detection method of a CVT.

Background Art

The voltage-dividing capacitor and electromagnetic unit of the capacitive voltage transformer CVT solve the problem that the electromagnetic transformer is prone to resonance. However, if a fault occurs in the transformer itself, it may cause various voltage instabilities and trigger the protection system to operate.

In order to analyze the insulation impedance stability of the capacitive voltage transformer, an impulse pulse is needed and its spectrum characteristics are analyzed. However, the existing pulse test sources have a typical problem: poor repeatability, easy to generate overvoltage, and it is difficult to ensure the consistency of the waveform of each impulse pulse, so the overvoltage is also difficult to estimate. Therefore, it is necessary to improve the existing technology.

Summary of the invention

The purpose of the present invention is to provide a synthetic pulse detection method for CVT, which can solve the problems in the prior art that the pulse test source has poor repeatability and the pulse waveform is difficult to ensure consistency.

The objective of the present invention is achieved through the following technical solutions:

In a first aspect, the present invention provides a synthetic pulse detection device for a CVT, comprising a signal generator, a transformer, a capacitor, an adjustable inductor, a normally open relay, a first signal conditioning module, a second signal conditioning module, an analog-to-digital converter and a microprocessor, wherein the output end of the signal generator is connected to the primary side of the transformer, and the secondary side of the transformer is connected to the high voltage side of the CVT to be measured after passing through the capacitor and the adjustable inductor in sequence; the input end of the second signal conditioning module is connected to the secondary voltage end of the CVT to be measured, and the output end is connected to an input end of the analog-to-digital converter; the input end of the first signal conditioning module is connected to the connection node of the capacitor and the adjustable inductor, and the output end is connected to the other input end of the analog-to-digital converter; the output end of the analog-to-digital converter is connected to the first IO port of the microprocessor; the second IO port of the microprocessor is connected to the signal generator, and the third IO port of the microprocessor is connected to the control end of the normally open relay; the normally open relay is connected in parallel with the adjustable inductor.

Furthermore, the signal generator generates three-frequency sine wave signals simultaneously, and the frequency ratios of the three-frequency sine wave signals are 1:3:5 respectively.

Furthermore, the adjustable range of the adjustable inductor is 1uH-10mH.

In a second aspect, the present invention provides a synthetic pulse detection method for a CVT, comprising the following steps:

Debugging synthetic pulse detection device using fault-free standard CVT;

The CVT under test is detected using the debugged synthetic pulse detection device.

Further, the method of debugging the synthetic pulse detection device using a fault-free standard CVT includes:

Connect the fault-free standard CVT to the synthetic pulse detection device, apply three-frequency sinusoidal signals to the high-voltage side of the fault-free standard CVT at the same time, and collect the fault-free standard CVT secondary voltage signal _V1 and high-voltage side voltage signal _V2 in real time;

Analyze the voltage ratio V ₂ /V ₁ of the fault-free standard CVT. When the fluctuation of the voltage ratio V ₂ /V ₁ of the fault-free standard CVT is greater than 1%, find the corresponding maximum frequency in the three-frequency sinusoidal signals, and observe the stability of the phase difference between the secondary voltage signal V ₁ and the high-voltage side voltage signal V ₂ of the fault-free standard CVT. When the fluctuation of the phase difference is greater than 0.5 degrees, adjust the value of the adjustable inductor so that the phase difference fluctuation is less than 0.5 degrees, record the adjusted phase difference as the standard phase difference, and record the adjustment position of the adjusted adjustable inductor; otherwise, directly record the phase difference as the standard phase difference, and record the adjustment position of the adjustable inductor.

Furthermore, the method for adjusting the value of the adjustable inductance is: observe the phase difference of the frequency spectrum data of the fault-free standard CVT secondary voltage signal _V1 and the high-voltage side voltage signal _V2 at three frequencies; if the three phase differences show a decreasing trend, increase or decrease the adjustable inductance value in the same direction until the phase difference is stable and in the minimum value interval; and record the stable phase difference in the minimum value interval as the standard phase difference and the adjustment position of the adjustable inductance.

Furthermore, the method of detecting the CVT under test by using the debugged synthetic pulse detection device specifically includes:

Simultaneously applying three frequency sinusoidal signals to the CVT under test, collecting the waveforms of the secondary voltage signal V ₁ ′ and the high-voltage side voltage signal V ₂ ′ of the CVT under test;

When the highest frequency of the three-frequency sinusoidal signal is less than 100kHz, V ₁ ′ or V ₂ ′ has an overvoltage phenomenon, it is determined that the CVT under test has an insulation fault; when the highest frequency of the three-frequency sinusoidal signal is ≥100kHz, the secondary voltage signal V ₁ ′ or the high-voltage side voltage signal V ₂ ′ of the CVT under test has an overvoltage phenomenon, the adjustable inductor is short-circuited to eliminate the overvoltage; when the phase difference of the CVT under test is greater than or equal to 100kHz, the CVT under test has an insulation fault. When the phase difference of the sinusoidal signal of at least one frequency is greater than the set value compared with the standard phase difference, it is determined that the CVT under test has a fault.

Furthermore, the set value is 0.25 degrees.

Furthermore, the method for eliminating overvoltage is: when the adjustable inductor is short-circuited, the value of the adjustable inductor is adjusted, the normally open relay is turned off, and the secondary voltage signal V ₁ ′ or the high-voltage side voltage signal V ₂ ′ of the CVT under test is continuously observed to see whether there is an overvoltage phenomenon; if so, the adjustable inductor is short-circuited, and the adjustable inductor is continuously adjusted; the relay is turned off again to observe whether there is an overvoltage phenomenon, until there is no overvoltage phenomenon.

Furthermore, the overvoltage phenomenon refers to that the secondary voltage signal V ₁ ′ or the high-voltage side voltage signal V ₂ ′ of the CVT under test is greater than 30% of the rated output voltage.

The synthetic pulse detection method of CVT of the present invention designs the signals of three frequency points to approximately synthesize the square wave signal, which has the advantage of making full use of the characteristics of easy generation and high repeatability of sine wave, so that the synthesized square wave has high repeatability. The synthesis of three frequency points is also conducive to reducing the impact current and the power of the test source.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

FIG1 is a circuit block diagram of a synthetic pulse detection device of the present invention;

FIG2 is a schematic diagram of the steps of the synthetic pulse detection method of the present invention;

FIG3 is a schematic diagram of the steps of debugging a synthetic pulse detection device using a fault-free standard CVT according to the present invention;

FIG. 4 is a schematic diagram of the steps of detecting a CVT under test using the debugged synthetic pulse detection device of the present invention.

DETAILED DESCRIPTION

The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

The following describes the embodiments of the present disclosure through specific examples, and those skilled in the art can easily understand other advantages and effects of the present disclosure from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all of the embodiments. The present disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present disclosure.

A synthetic pulse detection device for a CVT of the present invention, as shown in FIG1, comprises a signal generator, a transformer, a capacitor, an adjustable inductor, a normally open relay, a signal conditioning module 1, a signal conditioning module 2, an analog-to-digital converter and a microprocessor, wherein the output end of the signal generator is connected to the primary side of the transformer, and the secondary side of the transformer is connected to the capacitor and the adjustable inductor in sequence and then connected to the high voltage side of the CVT to be measured. The input end of the signal conditioning module 2 is connected to the secondary voltage end of the CVT to be measured, and the output end is connected to an input end of the analog-to-digital converter. The input end of the signal conditioning module 1 is connected to the connection node of the capacitor and the adjustable inductor, and the output end is connected to the other input end of the analog-to-digital converter. The output end of the analog-to-digital converter is connected to the first IO port of the microprocessor. The second IO port of the microprocessor is connected to the signal generator. The third IO port of the microprocessor is connected to the control end of the normally open relay. The normally open relay is connected in parallel with the adjustable inductor.

The working principle of Figure 1 is: the signal generator simultaneously sends out three-frequency sinusoidal wave signals, which are sequentially input to the high-voltage side of the CVT after passing through the transformer, capacitor, and adjustable inductor. The signal conditioning module 2 collects the CVT secondary voltage signal and feeds it back to the analog-to-digital converter. The signal conditioning module 1 collects the signal of the node where the adjustable inductor and capacitor are connected (i.e., the CVT high-voltage side voltage signal) and feeds it back to the analog-to-digital converter. The digital-to-analog converter converts the signal and sends it to the microprocessor. After receiving the signal from the analog-to-digital converter, the microprocessor analyzes the two signals and controls the closing or closing of the normally open relay according to the analysis results.

Furthermore, the frequency ratios of the three-frequency sine wave signals are 1:3:5 respectively. The signal conditioning module has at least two paths, one of which is connected to the secondary voltage terminal of the CVT, and the other is connected to the output power supply on the high-voltage side of the CVT. The output end of the signal conditioning module 1 and the output end of the signal conditioning module 2 are respectively connected to the two channels corresponding to the analog-to-digital converter.

Furthermore, the adjustable range of the adjustable inductor is 1uH-10mH.

A synthetic pulse detection method for a CVT of the present invention comprises the following steps:

Step S1, using a fault-free standard CVT to debug the synthetic pulse detection device.

Further, debugging the synthetic pulse detection device using a fault-free standard CVT includes:

Step S101, connect the fault-free standard CVT to the synthetic pulse detection device, apply three-frequency sinusoidal signals to the high-voltage side of the fault-free standard CVT at the same time, and collect the fault-free standard CVT secondary voltage signal _V1 and high-voltage side voltage signal _V2 in real time.

Step S102, analyzing the voltage ratio _V2 / _V1 of the fault-free standard CVT. When the fluctuation of the voltage ratio _V2 / _V1 of the fault-free standard CVT is greater than 1%, find the corresponding maximum frequency in the three-frequency sinusoidal signal, observe the stability of the phase difference between the secondary voltage signal _V1 and the high-voltage side voltage signal _V2 , and when the fluctuation of the phase difference is greater than 0.5 degrees, it is considered that the fault-free standard CVT does not match the synthetic pulse detection device, and the value of the adjustable inductor is adjusted so that the phase difference fluctuation is less than 0.5 degrees. The adjusted phase difference is recorded as the standard phase difference, and the adjustment position of the adjustable inductor is recorded; otherwise, the phase difference is directly recorded as the standard phase difference, and the adjustment position of the adjustable inductor is recorded.

Specifically, the method for adjusting the value of the adjustable inductance is: observe the phase difference of the frequency spectrum data of the fault-free standard CVT secondary voltage signal _V1 and the high-voltage side voltage signal _V2 at three frequencies. If the three phase differences show a decreasing trend, increase or decrease the adjustable inductance value in the same direction until the phase difference is stable and in the minimum value range. Record the phase difference at the three frequency points as the standard phase difference and the adjustable inductance adjustment position.

Step S2: Detect the CVT under test by using the debugged synthetic pulse detection device, specifically:

Step S201: applying the three-frequency sinusoidal signals to the CVT under test simultaneously, and collecting the waveforms of the secondary voltage signal V ₁ ′ and the high-voltage side voltage signal V ₂ ′ of the CVT under test.

The CVT under test must be of the same specification as the fault-free standard CVT in step S1. Otherwise, the debugging step of step S1 is meaningless.

Step S202: when the highest frequency of the three-frequency sinusoidal signals is less than 100 kHz and an overvoltage occurs in V ₁ ′ or V ₂ ′, it is determined that the CVT under test has an insulation fault;

When the highest frequency of the three-frequency sinusoidal signals is ≥100kHz and overvoltage occurs on V ₁ ′ or V ₂ ′, the adjustable inductor is short-circuited to make the entire test loop deviate from resonance and eliminate the overvoltage;

When the phase difference between V ₂ ′ and V ₁ ′ When the phase difference of the sinusoidal signal of at least one frequency is greater than the set value compared with the standard phase difference, it is determined that the CVT under test has a fault.

The overvoltage phenomenon refers to V ₁ ′ or V ₂ ′ being greater than 30% of the rated output voltage.

Preferably, the set value is 0.25 degrees.

Further, the method of short-circuiting the adjustable inductor is: connecting a normally open relay in parallel to the adjustable inductor, and controlling the normally open relay to close by a microprocessor. Conversely, if the adjustable inductor is to be restored, the normally open relay is controlled to close by the microprocessor.

Further, the steps to eliminate overvoltage are:

When the adjustable inductor is short-circuited, adjust the adjustable inductor, turn off the normally open relay, and continue to observe whether V ₁ ′ or V ₂ ′ has overvoltage. If so, short-circuit the adjustable inductor, continue to adjust the adjustable inductor, turn off the relay again to observe whether there is overvoltage, until there is no overvoltage.

The present invention focuses on proposing a method of applying three odd-frequency sine waves simultaneously, using the three sine waves to synthesize a square wave, and then because the three waveform frequencies of the test power supply are known, it can play a role of a better stable test source. In this case, it can be observed whether there is a problem of current stability under the test voltage.

In order to eliminate the resonant overvoltage caused by CVT defects and the impulse test pulse circuit, a fast detuning measure was designed to facilitate the rapid protection of the device and the simultaneous observation of the stability of the CVT.

In order to better illustrate the working principle and beneficial effects of the present invention, the following is a description in combination with specific test data:

Assume that a 220kV CVT is tested, and the three applied signals are 1.5kV signals of 300Hz, 900Hz, and 1500Hz, respectively. The specifications of the transformer are: 600 turns of the three primary windings and 200 turns of the secondary winding. Assume that the coupling capacitor has a capacitance of 10uF and the adjustable range of the adjustable inductor is 1uH-10mH. Assume that when the standard CVT is tested normally, the phase difference of the three frequency points is less than 0.05 degrees. When testing the CVT under test, the phase differences of the three frequency points were observed to be 0.08 degrees, 0.1 degrees, and 0.55 degrees, respectively. The phase difference at the 1500Hz frequency point is significantly greater than the set value of 0.25. It can be considered that the CVT under test has a weak ability to withstand impact signals or high-frequency signals.

It can be seen that when applying three frequency signals for synthesis, it is necessary to perform spectrum analysis on the output waveform and the collected waveform to extract the amplitude and phase information of the three frequency points. Since the CVT is subjected to signals at multiple frequency points at the same time, the energy distribution of the internal distributed parameters achieves an effect of withstanding shock pulses, rather than simply applying three frequency signals separately. Therefore, the observed phase difference is more practical. On the contrary, if a signal at a certain frequency point is applied alone, the phase difference may be less than 0.05.

The three frequency points selected in this embodiment are all relatively low. In this case, theoretically, there will be no resonant overvoltage phenomenon. If the resonant overvoltage phenomenon has occurred within 100kHz, the highest frequency point among the three frequency points, indicating that the CVT itself has insulation abnormalities, resulting in the internal resonant voltage frequency being too low. Based on this situation, the CVT fault can be directly determined.

In the present invention, unless otherwise clearly specified and limited, the first feature "on" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. "Multiple" means at least two, such as two, three, etc., unless otherwise clearly and specifically limited.

In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

The above is only for explaining the implementation mode of the present invention and is not intended to limit the present invention. For those skilled in the art, any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention without creative work should be included in the protection scope of the present invention.

Claims (4)

1. A synthetic pulse detection method for a CVT, using a synthetic pulse detection device, the synthetic pulse detection device comprising: a signal generator, a transformer, a capacitor, an adjustable inductor, a normally open relay, a first signal conditioning module, a second signal conditioning module, an analog-to-digital converter and a microprocessor, the output end of the signal generator is connected to the primary side of the transformer, the secondary side of the transformer is connected to the high voltage side of the CVT to be measured after passing through the capacitor and the adjustable inductor in sequence; the input end of the second signal conditioning module is connected to the secondary voltage end of the CVT to be measured, and the output end is connected to an input end of the analog-to-digital converter; the first signal The input end of the conditioning module is connected to the connection node of the capacitor and the adjustable inductor, and the output end is connected to another input end of the analog-to-digital converter; the output end of the analog-to-digital converter is connected to the first IO port of the microprocessor; the second IO port of the microprocessor is connected to the signal generator, and the third IO port of the microprocessor is connected to the control end of the normally open relay; the normally open relay is connected in parallel with the adjustable inductor; the signal generator simultaneously generates three-frequency sine wave signals, and the frequency ratios of the three-frequency sine wave signals are 1:3:5 respectively, and the adjustable range of the adjustable inductor is 1uH-10mH, It is characterized by comprising the following steps: The synthetic pulse detection device is debugged using a fault-free standard CVT; the synthetic pulse detection device is debugged using a fault-free standard CVT, comprising: Connect the fault-free standard CVT to the synthetic pulse detection device, apply three-frequency sinusoidal signals to the high-voltage side of the fault-free standard CVT at the same time, and collect the fault-free standard CVT secondary voltage signal V1 and the high-voltage side voltage signal V2 in real time; Analyze the voltage ratio V2/V1 of the fault-free standard CVT. When the fluctuation of the voltage ratio V2/V1 of the fault-free standard CVT is greater than 1%, find the corresponding maximum frequency in the sinusoidal signals of the three frequencies, observe the stability of the phase difference between the secondary voltage signal V1 and the high-voltage side voltage signal V2 of the fault-free standard CVT, and when the fluctuation of the phase difference is greater than 0.5 degrees, adjust the value of the adjustable inductance so that the phase difference fluctuation is less than 0.5 degrees, record the adjusted phase difference as the standard phase difference, and record the adjustment position of the adjusted adjustable inductance; otherwise, directly record the phase difference as the standard phase difference, and record the adjustment position of the adjustable inductance; the method for adjusting the value of the adjustable inductance is: observe the phase difference of the frequency spectrum data of the fault-free standard CVT secondary voltage signal V1 and the high-voltage side voltage signal V2 at three frequencies, if the three phase differences show a decreasing trend, increase or decrease the adjustable inductance value in the same direction until the phase difference is stable and in the minimum value interval, and record the stable phase difference in the minimum value interval as the standard phase difference and the adjustment position of the adjustable inductance; The method of detecting the CVT under test by using the debugged synthetic pulse detection device comprises: Simultaneously applying three frequency sinusoidal signals to the CVT under test, collecting the waveforms of the secondary voltage signal V1′ and the high-voltage side voltage signal V2′ of the CVT under test; When the highest frequency of the three-frequency sinusoidal signals is less than 100kHz and overvoltage occurs in V1′ or V2′, it is determined that the CVT under test has an insulation fault; when the highest frequency of the three-frequency sinusoidal signals is ≥100kHz and overvoltage occurs in the secondary voltage signal V1′ or the high-voltage side voltage signal V2′ of the CVT under test, the adjustable inductor is short-circuited to eliminate the overvoltage; when the phase difference ø(V2′)-ø(V1′) of the CVT under test is compared with the standard phase difference, if the phase difference of at least one frequency of the sinusoidal signal is greater than the set value, it is determined that the CVT under test has a fault. 2 . The synthetic pulse detection method of CVT according to claim 1 , wherein the set value is 0.25 degrees. 3. The synthetic pulse detection method of CVT according to claim 1 is characterized in that the method for eliminating overvoltage is: when the adjustable inductor is short-circuited, the value of the adjustable inductor is adjusted, the normally open relay is turned off, and the secondary voltage signal V1′ or the high-voltage side voltage signal V2′ of the CVT under test is continuously observed to see whether there is an overvoltage phenomenon; if so, the adjustable inductor is short-circuited and the adjustable inductor is continuously adjusted; the relay is turned off again to observe whether there is an overvoltage phenomenon until there is no overvoltage phenomenon. 4. The synthetic pulse detection method of CVT according to claim 1 is characterized in that the overvoltage phenomenon refers to the secondary voltage signal V1′ or the high-voltage side voltage signal V2′ of the CVT under test being greater than 30% of the rated output voltage.