CN110031677A - Dry-type air-core reactor scene impedance measuring circuit and detection method - Google Patents
Dry-type air-core reactor scene impedance measuring circuit and detection method Download PDFInfo
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Abstract
Dry-type air-core reactor scene impedance measuring circuit and detection method.Since there are also other operating reactance devices to work around tested reactor when detecting at the scene, biggish line-frequency induction electric current can be generated in tested reactor, leading to the electric current for flowing through reactor is the superposition of line-frequency induction electric current and the detection electric current applied.Present invention composition includes: current transformer unit (1), current transformer unit is connect with voltage and current signal acquisition unit (2), voltage and current signal acquisition unit is connect with resitstance voltage divider (3), and resitstance voltage divider is in parallel with tested reactor (4), inductanceL 3And capacitorC 1Tested reactor both ends, inductance are connected in parallel on after series connectionL 3With protective resistanceR 4Connection, protective resistance are connect with isolating transformer, and isolating transformer is connect with intermediate frequency power supply (5), and tested reactor and surrounding operating reactance device (6) pass through mutual inductanceM 12Connection.The present invention is used for dry-type air-core reactor impedance in-site measurement.
Description
the technical field is as follows:
the invention relates to a dry-type air-core reactor field impedance measuring circuit and a detection method.
Background art:
with the gradual development of the power grid towards the directions of high capacity, long distance, ultrahigh voltage and extra-high voltage, it is important to ensure the safe and stable operation of the power grid. The reactor can play the roles of compensating reactive power, limiting short-circuit current, filtering higher harmonics and the like, and is widely applied to a power grid at present. The impedance parameter of the reactor is an important index for measuring the quality of the reactor, and the method has great significance for effectively measuring the impedance of the reactor.
The impedance measuring method for the reactor mainly comprises a direct current resistance measuring method and a power frequency measuring method at present. The direct-current resistance measurement method can only measure the resistance of the reactor, and cannot measure the reactance of the reactor. The power frequency detection method is affected by the interference of the power frequency of a test site, so that the frequency of a measurement signal is the same as that of a power frequency induction signal, and the measurement signal and the power frequency induction signal are superposed together and are difficult to distinguish, so that the method cannot realize accurate measurement of the impedance of the reactor. Therefore, it is necessary to invent a method for effectively detecting the impedance of the reactor.
When in on-site detection, because other running reactors work around the reactor to be detected, a large power frequency induction current can be generated in the reactor to be detected, and the current flowing through the reactor is the superposition of the power frequency induction current and the applied detection current.
The invention content is as follows:
the invention aims to provide a dry-type air-core reactor on-site impedance measuring circuit and a detection method. And a formula for eliminating power frequency interference and calculating the impedance parameter of the reactor by using a harmonic analysis method is provided. And judging whether the reactor has a fault according to the measured impedance parameter.
The above purpose is realized by the following technical scheme:
a dry-type air-core reactor field impedance measurement circuit comprises: the current transformer unit is connected with the voltage and current signal acquisition unit, the voltage and current signal acquisition unit is connected with the resistor divider, the resistor divider is connected with the measured reactor in parallel, and the inductorL 3And a capacitorC 1After being connected in series, the inductor is connected in parallel at two ends of the measured reactorL 3And a protective resistorR 4The protection resistor is connected with an isolation transformer, the isolation transformer is connected with an intermediate frequency power supply, and the measured reactor and the surrounding running reactors are mutually inductedM 12And (4) connecting.
The dry-type air-core reactor field impedance measurement circuit is characterized in that the surrounding operation reactor comprises a resistorR 1The above-mentionedR 1And an inductorL 1In series, said resistorR 1And said inductorL 1To operate the equivalent resistance and equivalent reactance of the reactor.
The dry-type air-core reactor field impedance measuring circuit is characterized in that the to-be-detected resistance reactor comprises a resistorR 2The above-mentionedR 2And an inductorL 2In series, said resistorR 2And an inductorL 2The equivalent resistance and the equivalent reactance of the measured reactor.
The dry-type air-core reactor on-site impedance measuring circuit is characterized in that the current transformer unit comprises an inductorL 4Said inductorL 4And a capacitorC 2After being connected in series with the resistorR 3And the current transformer units are connected in parallel, and the current of the reactor is extracted by combining the current transformer units.
A detection method using the dry-type air-core reactor on-site impedance measurement circuit of claims 1-4, applies a detection signal with power frequency integer times frequency to the reactor through the intermediate frequency power supply of the detection circuit, and the detection frequency is selected in the frequency range of 50-400Hz closest to the power frequency, so that the detection signal and the power frequency interference signal cannot be distinguished due to the same frequency; required inductanceL 3And a capacitorC 1Resonance is formed under power frequency, so that power frequency induction current generated on the measured reactor generates circulation current in the main circuit, and the influence on a detection power supply is avoided;
the current signal collected by the current sensor comprises two parts of detection frequency current and power frequency induced current, and power frequency interference in the collected current is not eliminated by taking measures;
required inductanceL 4And a capacitorC 2Forming resonance at power frequency to make power frequency signal pass through inductorL 4And a capacitorC 2Short circuit, eliminating power frequency current signal interference and simultaneously requiring inductanceL 4And a capacitorC 2The impedance of the detection signal is far larger than that of the resistorR 3Passing the detection current signal through a resistorR 3Entering a current acquisition module; the voltage at the two ends of the reactor is extracted through a resistance voltage divider, power frequency interference is eliminated through a harmonic analysis method, extraction of detection voltage signals at the two ends of the reactor is completed, and then the impedance of the reactor can be obtained through the collected voltage and current.
The detection method of the dry-type air reactor field impedance measurement circuit comprises the following steps:
first, it is determinedL 3AndC 1is a value of, a requirementL 3AndC 1andL 4andC 2series resonance occurs under power frequency, and then the condition of power frequency resonance is satisfied:
(3)
the electric reactor to be tested applies detection signals of integral multiple of power frequency and the voltage is set asAt power frequencynDoubling;
M 23is a measured reactor andLCthe mutual inductance between the circuits is such that,for applying the detection voltage, the voltage equation can be obtained as follows:
(4)
in which the angular frequency of the applied measuring signal is based onWhen the mutual inductance is maximum, the equation is solved to obtainAndrespectively as follows:
(5)
(6)
by substituting formula (3) for formulae (5) and (6):
(7)
(8)
as can be seen from equations (7) and (8), in the case where the frequency of the detection signal and the electric reactor to be measured are determined,andare all aboutL 3The function of (1) requires that the measured reactor is passed through a larger measuring current, and then needs to be correctedMuch less than(ii) a Then the ones that satisfy the condition can be selected according to the above formulaL 3Can be determined by the formula (3)C 1Taking the value of (A);
in the case of the current transformer module as such,L 4andC 2resonance under power frequency, the relation between the two satisfies the formula (3), thenL 4AndC 2the impedance to the sense current is given by:
(9)
requiring the passage of a detection currentR 3Entering the current collection module to satisfyZIs much larger thanR 3(gettingZHas a value of greater thanR 350 times the value can be consideredZIs much larger thanR 3) According to the above formula, it can be determined that the condition is satisfiedC 2The value of (2) can be determined by the formula (3)L 4The value of (a).
The detection method of the dry-type air-core reactor on-site impedance measurement circuit utilizes the harmonic analysis method to process the acquired reactor voltage and current signals, and ensures that the sampling period is integral multiple of the power frequency and the detection signal frequency.
Reactor current signal acquired by harmonic analysis methodIAnd reactor terminal voltage signalVIs required to be atnIntegration over one fundamental period, and requiring adjustmentnA value of (A) tonTIs an integral multiple of the power frequency period; thus, the power frequency interference signal isnTIn intervals of a full period of timenTThe integral value in the interval is zero, and the integral result is the calculation result of the applied detection signal at the moment, so that the purpose of eliminating power frequency interference is achieved, and the principle is as follows:
if the intermediate frequency measures the current of the power supply flowing through the reactor asThe voltage drop generated across the reactor isThe power frequency induced current and the voltage on the reactor are respectivelyAndand the current and the voltage of the measured reactor are superposed, and the current collected by the mutual inductor and the voltages at the two ends of the current flowing through the reactor are respectively as follows:
(10)
whereinAndwith a Fourier expansion as:
(11)
(12)
wherein,f 0is the frequency of the fundamental wave and is,a i0is composed ofV i The direct-current component of (a) is,A ik is composed ofV i Is/are as followskThe magnitude of the sub-harmonics,is composed ofV i Is/are as followskThe initial phase of the subharmonic;a u0is composed ofV u The direct-current component of (a) is,A uk is composed ofV u Is/are as followskThe magnitude of the sub-harmonics,is composed ofV u Is/are as followskThe initial phase of the subharmonic.
In the formula (10), the first and second groups,andcan be expressed by the following expression:
(13)
thenAndwith a Fourier expansion as:
(14)
in thatnIntegration over one fundamental period, and requiring adjustmentnA value of (A) tonTIs an integral multiple of the power frequency period, so that the power frequency interference signal is innTOver a whole period of time, i.e.Andin thatnTThe integral value of the interval is zero, only the applied detection signal is left at the moment, the purpose of eliminating power frequency interference is achieved, and according to the analysis, the imaginary parts of the two fundamental wave signals can be obtaineda i1、a u1And real partb i1、b u1Comprises the following steps:
(15)
then the amplitudes of the two groups of fundamental wave signals are respectively:
the initial phases of the fundamental voltage signal and the fundamental current signal are respectively as follows:
the proportion of the current transformer module to the resistance voltage divider is respectively set asn 1Andn 2then, a calculation expression of the reactor impedance is obtained through a series of mathematical deductions as follows:
(16)
has the advantages that:
the invention can be used for field measurement of the impedance of the reactor. The fault condition of the reactor can be reflected by the measured reactor impedance parameter. Research shows that when the reactor does not have a fault, the resistance parameter of the reactor does not change along with the frequency of the applied detection signal. When the reactor has turn-to-turn short circuit and turn number deviation fault, the resistance parameter of the reactor is increased along with the increase of the frequency of the detection signal, so that whether the reactor has fault or not can be judged according to the change rate of the resistance of the reactor.
The invention provides a circuit for detecting a resistance parameter of a reactor by adopting power frequency integer multiple frequency. And the harmonic analysis method is used for eliminating power frequency interference on the measuring site, so that the on-site measurement of the impedance of the reactor is realized. And provides a basis for judging the fault of the reactor according to the measured impedance parameters. The method well solves the problem that the existing reactor impedance measurement method cannot measure the reactance and is greatly interfered by power frequency, so that the measurement result is inaccurate.
Description of the drawings:
FIG. 1 is a schematic structural diagram of the present invention.
FIG. 2 is a parallel circuit of reactor and LC of the invention under the detection signal of integral multiple.
The specific implementation mode is as follows:
example 1:
a dry-type air-core reactor field impedance measurement circuit comprises: the current transformer unit 1, the current transformer unit be connected with voltage current signal acquisition unit 2, voltage current signal acquisition unit be connected with resistance voltage divider 3, resistance voltage divider and surveyed reactance ware 4 parallelly connected, inductanceL 3And a capacitorC 1After being connected in series, the inductor is connected in parallel at two ends of the measured reactorL 3And a protective resistorR 4The protection resistor is connected with an isolation transformer, the isolation transformer is connected with an intermediate frequency power supply 5, and the measured reactor and a surrounding running reactor 6 are mutually inductedM 12And (4) connecting.
Example 2:
according to example 1The dry-type air-core reactor field impedance measurement circuit is characterized in that the ambient operation reactor comprises a resistorR 1The above-mentionedR 1And an inductorL 1In series, said resistorR 1And said inductorL 1To operate the equivalent resistance and equivalent reactance of the reactor.
Example 3:
the dry air reactor in-situ impedance measurement circuit as in embodiment 2, wherein the resistor reactor to be tested comprises a resistorR 2The above-mentionedR 2And an inductorL 2In series, said resistorR 2And an inductorL 2The equivalent resistance and the equivalent reactance of the measured reactor.
Example 4:
the dry air reactor in-situ impedance measuring circuit of embodiment 3, wherein the current transformer unit comprises an inductorL 4Said inductorL 4And a capacitorC 2After being connected in series with the resistorR 3And the current transformer units are connected in parallel, and the current of the reactor is extracted by combining the current transformer units.
Example 5:
a detection method using the dry-type air-core reactor on-site impedance measurement circuit of claims 1-4, applies a detection signal with power frequency integer times frequency to the reactor through the intermediate frequency power supply of the detection circuit, and the detection frequency is selected in the frequency range of 50-400Hz closest to the power frequency, so that the detection signal and the power frequency interference signal cannot be distinguished due to the same frequency; required inductanceL 3And a capacitorC 1Resonance is formed under power frequency, so that power frequency induction current generated on the measured reactor generates a ring in the main circuitThe current is ensured not to influence the detection power supply;
the current signal collected by the current sensor comprises two parts of detection frequency current and power frequency induced current, and power frequency interference in the collected current is not eliminated by taking measures;
required inductanceL 4And a capacitorC 2Forming resonance at power frequency to make power frequency signal pass through inductorL 4And a capacitorC 2Short circuit, eliminating power frequency current signal interference and simultaneously requiring inductanceL 4And a capacitorC 2The impedance of the detection signal is far larger than that of the resistorR 3Passing the detection current signal through a resistorR 3Entering a current acquisition module; the voltage at the two ends of the reactor is extracted through a resistance voltage divider, power frequency interference is eliminated through a harmonic analysis method, extraction of detection voltage signals at the two ends of the reactor is completed, and then the impedance of the reactor can be obtained through the collected voltage and current.
In the context of the attached figure 1,R 2andL 2the equivalent resistance and the equivalent reactance of the measured reactor are obtained;R 1andL 1the equivalent resistance and the equivalent reactance of the running reactor;M 12mutual inductance between the reactors; applying a detection frequency signal by an intermediate frequency power supply; resistance (RC)R 4To protect the resistance;L 3andC 1after being connected in series, the two ends of the reactor to be tested are connected in parallel. In the current sensor circuitL 4AndC 2after being connected in series withR 3And the current is connected in parallel and is combined with a current transformer to finish the extraction of the current of the reactor. The resistance voltage divider realizes the extraction of voltage signals at two ends of the reactor.
As can be seen from the attached figure 1, mutual inductance exists between the operating reactor and the measured reactorM 12When the power frequency signal is induced, the power frequency induction current generated on the reactor to be tested is short-circuited to obtain a circuitThe equation is:
(1)
whereinAndis the current and voltage of the reactor operating around,the power frequency induction current generated on the reactor to be tested is obtained. The power frequency induction voltage of the reactor is as follows:
(2)
for the working current of normal reactor, generally several hundreds to several thousands of amperes, the power frequency induced voltage on the reactor to be tested can reach several thousands of volts or even higher, so it is necessary to shield the power frequency interference during field detection.
Example 6:
according to the detection method of the dry-type air-core reactor field impedance measurement circuit in the embodiment 5, the parameter determination method of the detection circuit comprises the following steps:
first, it is determinedL 3AndC 1is a value of, a requirementL 3AndC 1andL 4andC 2series resonance occurs under power frequency, and then the condition of power frequency resonance is satisfied:
(3)
the electric reactor to be tested applies detection signals of integral multiple of power frequency and the voltage is set asAt power frequencynDoubling;
M 23is a measured reactor andLCthe mutual inductance between the circuits is such that,for applying the detection voltage, the voltage equation can be obtained as follows:
(4)
in which the angular frequency of the applied measuring signal is based onWhen the mutual inductance is maximum, the equation is solved to obtainAndrespectively as follows:
(5)
(6)
by substituting formula (3) for formulae (5) and (6):
(7)
(8)
as can be seen from equations (7) and (8), in the case where the frequency of the detection signal and the electric reactor to be measured are determined,andare all aboutL 3The function of (1) requires that the measured reactor is passed through a larger measuring current, and then needs to be correctedMuch less than(ii) a Then the ones that satisfy the condition can be selected according to the above formulaL 3Can be determined by the formula (3)C 1Taking the value of (A);
in the case of the current transformer module as such,L 4andC 2resonance under power frequency, the relation between the two satisfies the formula (3), thenL 4AndC 2the impedance to the sense current is given by:
(9)
requiring the passage of a detection currentR 3Entering the current collection module to satisfyZIs much larger thanR 3(gettingZHas a value of greater thanR 350 times the value can be consideredZIs much larger thanR 3) According to the above formula, it can be determined that the condition is satisfiedC 2The value of (2) can be determined by the formula (3)L 4The value of (a).
Example 7:
according to the detection method of the dry-type air-core reactor on-site impedance measurement circuit in the embodiment 5, the harmonic analysis method is used for processing the acquired reactor voltage and current signals, and the sampling period is ensured to be integral multiples of the power frequency and the detection signal frequency.
Reactor current signal acquired by harmonic analysis methodIAnd reactor terminal voltage signalVIs required to be atnIntegration over one fundamental period, and requiring adjustmentnA value of (A) tonTIs an integral multiple of the power frequency period; thus, the power frequency interference signal isnTIn intervals of a full period of timenTThe integral value in the interval is zero, and the integral result is the calculation result of the applied detection signal at the moment, so that the purpose of eliminating power frequency interference is achieved, and the principle is as follows:
if the intermediate frequency measures the current of the power supply flowing through the reactor asThe voltage drop generated across the reactor isThe power frequency induced current and the voltage on the reactor are respectivelyAndand the current and the voltage of the measured reactor are superposed, and the current collected by the mutual inductor and the voltages at the two ends of the current flowing through the reactor are respectively as follows:
(10)
whereinAndwith a Fourier expansion as:
(11)
(12)
wherein,f 0is the frequency of the fundamental wave and is,a i0is composed ofV i The direct-current component of (a) is,A ik is composed ofV i Is/are as followskThe magnitude of the sub-harmonics,is composed ofV i Is/are as followskThe initial phase of the subharmonic;a u0is composed ofV u The direct-current component of (a) is,A uk is composed ofV u Is/are as followskThe magnitude of the sub-harmonics,is composed ofV u Is/are as followskThe initial phase of the subharmonic.
In the formula (10), the first and second groups,andcan be expressed by the following expression:
(13)
thenAndwith a Fourier expansion as:
(14)
in thatnIntegration over one fundamental period, and requiring adjustmentnA value of (A) tonTIs an integral multiple of the power frequency period, so that the power frequency interference signal is innTOver a whole period of time, i.e.Andin thatnTThe integral value of the interval is zero, only the applied detection signal is left at the moment, the purpose of eliminating power frequency interference is achieved, and according to the analysis, the imaginary parts of the two fundamental wave signals can be obtaineda i1、a u1And real partb i1、b u1Comprises the following steps:
(15)
then the amplitudes of the two groups of fundamental wave signals are respectively:
the initial phases of the fundamental voltage signal and the fundamental current signal are respectively as follows:
the proportion of the current transformer module to the resistance voltage divider is respectively set asn 1Andn 2then, a calculation expression of the reactor impedance is obtained through a series of mathematical deductions as follows:
(16)
reactance measured in the present inventionZExtract the real part of the Chinese characterRNamely, the resistance of the reactor under the detection frequency is combined with the rated resistance of the reactorR 0The invention provides a formula for judging the fault of the reactor, which is as follows:
(17)
when the reactor works normallyClose to 0, in the event of failureWill become larger, in generalIf the current is more than 25%, the fault of the reactor can be judged. According to the method, whether the reactor has a fault or not can be judged.
Claims (7)
1. A dry-type air-core reactor field impedance measurement circuit comprises: the current transformer unit is characterized in that: the current transformer unit is connected with a voltage and current signal acquisition unit, the voltage and current signal acquisition unit is connected with a resistance voltage divider, the resistance voltage divider is connected with a tested reactor in parallel, and an inductorL 3And a capacitorC 1After being connected in series, the inductor is connected in parallel at two ends of the measured reactorL 3And a protective resistorR 4The protection resistor is connected with the isolation transformerThe isolation transformer is connected with a medium-frequency power supply, and the measured reactor and the surrounding running reactors are mutually inductedM 12And (4) connecting.
2. The dry-type air-core reactor field impedance measurement circuit according to claim 1, characterized in that: the reactor comprises a resistorR 1The above-mentionedR 1And an inductorL 1In series, said resistorR 1And said inductorL 1To operate the equivalent resistance and equivalent reactance of the reactor.
3. The dry-type air-core reactor field impedance measurement circuit according to claim 2, characterized in that: the detected resistance reactor comprises a resistorR 2The above-mentionedR 2And an inductorL 2In series, said resistorR 2And an inductorL 2The equivalent resistance and the equivalent reactance of the measured reactor.
4. The dry-type air-core reactor field impedance measurement circuit according to claim 3, characterized in that: the current transformer unit comprises an inductorL 4Said inductorL 4And a capacitorC 2After being connected in series with the resistorR 3And the current transformer units are connected in parallel, and the current of the reactor is extracted by combining the current transformer units.
5. A method of testing a dry air reactor field impedance measurement circuit using the dry air reactor of claims 1-4, comprising: applying a detection signal with power frequency integer times frequency to the reactor through a medium-frequency power supply of the detection circuit, wherein the detection frequency is selected in a frequency range of 50-400Hz closest to the power frequency, so that the detection signal and a power frequency interference signal cannot be distinguished due to the same frequency; required inductanceL 3And a capacitorC 1Form resonance at power frequency toThe power frequency induction current generated on the measured reactor generates a circulating current in the main circuit, so that the detection power supply is not influenced;
the current signal collected by the current sensor comprises two parts of detection frequency current and power frequency induced current, and power frequency interference in the collected current is not eliminated by taking measures;
required inductanceL 4And a capacitorC 2Forming resonance at power frequency to make power frequency signal pass through inductorL 4And a capacitorC 2Short circuit, eliminating power frequency current signal interference and simultaneously requiring inductanceL 4And a capacitorC 2The impedance of the detection signal is far larger than that of the resistorR 3Passing the detection current signal through a resistorR 3Entering a current acquisition module; the voltage at the two ends of the reactor is extracted through a resistance voltage divider, power frequency interference is eliminated through a harmonic analysis method, extraction of detection voltage signals at the two ends of the reactor is completed, and then the impedance of the reactor can be obtained through the collected voltage and current.
6. The detection method of the dry-type air-core reactor field impedance measurement circuit according to claim 4, characterized in that: the parameter determination method of the detection circuit comprises the following steps:
first, it is determinedL 3AndC 1is a value of, a requirementL 3AndC 1andL 4andC 2series resonance occurs under power frequency, and then the condition of power frequency resonance is satisfied:
(3)
the electric reactor to be tested applies detection signals of integral multiple of power frequency and the voltage is set asAt power frequencynDoubling;
M 23is a measured reactor andLCbetween circuitsThe mutual inductance is generated by the mutual inductance,for applying the detection voltage, the voltage equation can be obtained as follows:
(4)
in which the angular frequency of the applied measuring signal is based onWhen the mutual inductance is maximum, the equation is solved to obtainAndrespectively as follows:
(5)
(6)
by substituting formula (3) for formulae (5) and (6):
(7)
(8)
as can be seen from equations (7) and (8), in the case where the frequency of the detection signal and the electric reactor to be measured are determined,andare all aboutL 3The function of (1) requires that the measured reactor is passed through a larger measuring current, and then needs to be correctedMuch less than(ii) a Then the ones that satisfy the condition can be selected according to the above formulaL 3Can be determined by the formula (3)C 1Taking the value of (A);
in the case of the current transformer module as such,L 4andC 2resonance under power frequency, the relation between the two satisfies the formula (3), thenL 4AndC 2the impedance to the sense current is given by:
(9)
requiring the passage of a detection currentR 3Entering the current collection module to satisfyZIs much larger thanR 3Get itZHas a value of greater thanR 350 times the value can be consideredZIs much larger thanR 3According to the above formula, it can be determined that the condition is satisfiedC 2The value of (2) can be determined by the formula (3)L 4The value of (a).
7. The detection method of the dry-type air-core reactor field impedance measurement circuit according to claim 5, characterized in that: processing the acquired voltage and current signals of the reactor by using the harmonic analysis method, and ensuring that the sampling period is integral multiple of the power frequency and the frequency of the detection signal;
reactor current signal acquired by harmonic analysis methodIAnd reactor terminal voltage signalVIs required to be atnThe integration is carried out over a period of one fundamental wave,and require adjustmentnA value of (A) tonTIs an integral multiple of the power frequency period; thus, the power frequency interference signal isnTIn intervals of a full period of timenTThe integral value in the interval is zero, and the integral result is the calculation result of the applied detection signal at the moment, so that the purpose of eliminating power frequency interference is achieved, and the principle is as follows:
if the intermediate frequency measures the current of the power supply flowing through the reactor asThe voltage drop generated across the reactor isThe power frequency induced current and the voltage on the reactor are respectivelyAndand the current and the voltage of the measured reactor are superposed, and the current collected by the mutual inductor and the voltages at the two ends of the current flowing through the reactor are respectively as follows:
(10)
whereinAndwith a Fourier expansion as:
(11)
(12)
wherein,f 0is the frequency of the fundamental wave and is,a i0is composed ofV i The direct-current component of (a) is,A ik is composed ofV i Is/are as followskThe magnitude of the sub-harmonics,is composed ofV i Is/are as followskThe initial phase of the subharmonic;a u0is composed ofV u The direct-current component of (a) is,A uk is composed ofV u Is/are as followskThe magnitude of the sub-harmonics,is composed ofV u Is/are as followskThe initial phase of the subharmonic;
in the formula (10), the first and second groups,andcan be expressed by the following expression:
(13)
thenAndwith a Fourier expansion as:
(14)
in thatnIntegration over one fundamental period, and requiring adjustmentnA value of (A) tonTIs the power frequency cycleIntegral multiple of the period, known from the above formula, so that the power frequency interference signal is innTOver a whole period of time, i.e.Andin thatnTThe integral value of the interval is zero, only the applied detection signal is left at the moment, the purpose of eliminating power frequency interference is achieved, and according to the analysis, the imaginary parts of the two fundamental wave signals can be obtaineda i1、a u1And real partb i1、b u1Comprises the following steps:
(15)
then the amplitudes of the two groups of fundamental wave signals are respectively:
the initial phases of the fundamental voltage signal and the fundamental current signal are respectively as follows:
the proportion of the current transformer module to the resistance voltage divider is respectively set asn 1Andn 2then, a calculation expression of the reactor impedance is obtained through a series of mathematical deductions as follows:
(16)。
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| CN111666703A (en) * | 2020-06-09 | 2020-09-15 | 云南电网有限责任公司电力科学研究院 | Method and device for calculating impedance variation of dry-type air-core reactor |
| CN111830426A (en) * | 2020-01-13 | 2020-10-27 | 哈尔滨理工大学 | Method and system for detecting turn-to-turn short circuit fault and turn deviation of reactor |
| CN112505416A (en) * | 2020-11-17 | 2021-03-16 | 广东电网有限责任公司 | Method for measuring grounding impedance |
| CN112505421A (en) * | 2020-11-16 | 2021-03-16 | 广东电网有限责任公司 | Measuring circuit for direct current resistance of dry-type air-core reactor |
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| CN112505416A (en) * | 2020-11-17 | 2021-03-16 | 广东电网有限责任公司 | Method for measuring grounding impedance |
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