CN113933593B - Current comparator-based large-section cable conductor alternating-current equivalent resistance test system and method - Google Patents
Current comparator-based large-section cable conductor alternating-current equivalent resistance test system and method Download PDFInfo
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Abstract
A large-section cable conductor alternating-current equivalent resistance test system and method based on a current comparator belong to the technical field of electrical test and are provided for solving the problems that a test line of the existing large-section cable conductor test method is complex, weak resistive voltage components are difficult to effectively extract and the like. The current source comprises an alternating current source, a large-section cable conductor, a current transformer, an adjustable inductor, an adjustable resistor, an amplifier A, an amplifier B, a current comparator, a primary side first winding of the current comparator, a primary side second winding of the current comparator, a zero indicator, a resistor A, a resistor B, a resistor C, a resistor D, a load resistor E and a load resistor F. The operation is convenient, the measurement of the alternating-current equivalent resistance of the large-section cable conductor can be realized only by adjusting the adjustable inductor and the adjustable resistor, the sensitivity of the zero indicator of the current comparator is relatively high, the ampere turn balance of the primary winding of the current comparator is realized by increasing the sensitivity of the zero indicator, and the test precision and the anti-interference capability can be improved.
Description
Technical Field
The invention belongs to the technical field of electrical testing, and particularly relates to a large-section cable conductor alternating-current equivalent resistance testing system and method based on a current comparator.
Background
Ac power cable plays an important role in power supply and distribution of urban power gridThe current-carrying capacity is inseparable from the alternating current equivalent resistance. Under the effect of AC excitation, the cable conductor is affected by skin effect, the current density on the surface of the cable conductor is relatively large, and the current in the center of the cable conductor is relatively small, so that the equivalent AC resistance of the AC cable conductor is higher than the DC resistance of the cable conductor. If the direct current resistance of the cable conductor is directly adopted to calculate the current-carrying capacity of the alternating current cable, the error is large. In particular, when the cable conductor cross-sectional area exceeds 1600mm 2 The ac equivalent resistance is much higher than the conductor dc resistance. Therefore, accurate measurement of the alternating-current equivalent resistance of the large-section cable conductor is an important basis for checking the current-carrying capacity of the alternating-current power cable.
At present, the measurement of the alternating-current equivalent resistance of the cable conductor with a large section can be realized by a compensation voltage signal method, a cable sheath return line method, a digital measurement method and the like. The compensation voltage signal method is to compensate the inductive voltage component in the conductor loop with large section to be tested by adopting the inductive voltage component formed by the variable inductor, but the test circuit is relatively complex. The cable sheath reflow method is to use the metal sheath of the cable as the reflow line of the cable conductor, the test line has simple structure and high test precision, but is only suitable for the power cable with the metal sheath. The digital measurement method is to convert the obtained voltage and current data at two ends of the cable conductor from time domain to frequency domain through fast Fourier transform, eliminate the influence of the equivalent inductance voltage component of the cable conductor on the frequency domain, further obtain the equivalent alternating current resistance of the cable conductor, and the method is suitable for the occasion that the resistance voltage component and the inductance voltage component of the cable conductor are similar, but the method is not suitable for the cable conductor with large cross section>1600mm 2 ) Because its resistive voltage component is about forty times less than the inductive voltage component.
The prior art also has the problems of inconvenient operation, limited test precision and limited anti-interference capability.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a large-section cable conductor alternating-current equivalent resistance testing system and method based on a current comparator, which can solve the problems that the testing circuit of the existing large-section cable conductor testing method is complex, the application range is limited, weak resistive voltage components are difficult to effectively extract, and the like.
The invention adopts the technical scheme that:
a large-section cable conductor alternating-current equivalent resistance test system based on a current comparator comprises an alternating-current source, a large-section cable conductor, a current transformer, an adjustable inductor, an adjustable resistor, an amplifier A, an amplifier B, a current comparator, a primary side first winding of the current comparator, a primary side second winding of the current comparator, a zero indicator, a resistor A, a resistor B, a resistor C, a resistor D, a load resistor E and a load resistor F;
one end of an alternating current source is connected with the head end of a large-section cable conductor, the tail end of the large-section cable conductor is connected with one end of the primary side of a current transformer, the other end of the primary side of the current transformer is connected with the other end of the alternating current source, an adjustable inductor and an adjustable resistor are connected in series, two ends of the adjustable inductor and the adjustable resistor are respectively connected with two ends of the secondary side of the current transformer, the other end of the adjustable resistor connected with the adjustable inductor is connected with the ground, the negative polarity input end of an amplifier A is connected with the head end of the large-section cable conductor through a resistor A, the positive polarity input end of the amplifier A is connected with a resistor B, the other end of the resistor B is connected with the ground, the output end of the amplifier A is sequentially connected with the negative polarity input end of the amplifier A through a first winding of the primary side of the current comparator and a load resistor E, the negative polarity input end of the amplifier B is connected with the high voltage end of the adjustable inductor and the adjustable resistor through a resistor C, the positive polarity input end of the amplifier B is connected with the ground through a resistor D, and the output end of the amplifier B is sequentially connected with the primary side of the load winding of the current comparator F and the secondary side of the current comparator is connected with the input of the load winding of the load F;
the alternating current source is used for generating an alternating current source;
the large-section cable conductor is used as a conductor to be tested;
the current transformer is used for current conversion;
the adjustable inductor is used for adjusting the inductance;
the adjustable resistor is used for adjusting the resistance;
the amplifier A is used for passing through the resistor R of the resistor A 1 Converting the voltage at two ends of the large-section cable conductor into current flowing through a load resistor E and a first winding serial branch of the primary side of the current comparator;
the amplifier B is used for passing through a resistor R of a resistor C 2 Converting the voltage across the inductance of the adjustable inductor and the resistance of the adjustable resistor into a current flowing through the load resistor F and the primary second winding series branch of the current comparator;
the current comparator, the primary side first winding of the current comparator and the primary side second winding of the current comparator are used for balancing ampere turns of the primary side winding of the current comparator, and equivalent alternating current resistance values of the large-section cable conductors are calculated from the adjustable inductor and the adjustable resistor;
the zero indicator is used for representing the ampere turn balance of the primary winding of the current comparator when the pointer of the zero indicator indicates zero.
A large-section cable conductor alternating-current equivalent resistance test method based on a current comparator comprises the following steps:
step S1, calculating equivalent alternating current resistance R of large-section cable conductor x Voltage of equivalent inductance L x Is a voltage of (2);
step S2, solving the voltages at two ends of the inductance of the adjustable inductor and the voltages at two ends of the resistance of the adjustable resistor;
s3, obtaining the current of a primary side first winding branch of the current comparator;
s4, obtaining the current of a primary side second winding branch of the current comparator;
and S5, obtaining the equivalent alternating current resistance value of the cable conductor with the large section.
Further, in the step S1, the implementation manner is as follows:
AC current source generates sinusoidal excitation current with frequency fIts equivalent alternating current resistance R in large-section cable conductor x The voltage is generated, and the voltage formula is as follows:
in the formula (1), the components are as follows,is equivalent to an alternating current resistor R x Voltage of>Is current, R x Is equivalent to an alternating current resistor;
l on equivalent inductance x Generating a voltage, wherein the voltage formula is as follows:
in the formula (2), the amino acid sequence of the compound,is equivalent to inductance L x Is the frequency, L x Is equivalent inductance->Is a current.
Further, in the step S2, an embodiment is as follows:
the proportionality coefficient K of the current transformer is used for leading the current of the main loopConversion to a current through the series branch of the adjustable inductor and the adjustable resistor>The current generates a voltage across the inductance of the adjustable inductor, the voltage formula:
in the formula (3), the amino acid sequence of the compound,is the voltage at two ends of the inductor, f is the frequency, L is the inductance value of the adjustable inductor, < ->A current being a series branch of an adjustable resistor;
generating a voltage across the resistance of the adjustable resistor, the voltage formula:
in the formula (4), the amino acid sequence of the compound,is the voltage between two ends of the adjustable resistor, R is the resistance of the adjustable resistor, +.>Is the current of the series branch of the adjustable resistor.
Further, in the step S3, an embodiment is as follows:
the amplifier A passes through the resistor R of the resistor A 1 Converting the voltage at two ends of the large-section cable conductor into current flowing through a load resistor E and a first winding serial branch of the primary side of the current comparator;
voltage across large section cable conductors:
in the formula (5), the amino acid sequence of the compound,is a large-section cable guideVoltage across body, < >>For the voltage across the adjustable resistor, +.>Is equivalent to inductance L x Is a voltage of (2);
current of the series branch:
in the formula (6), the amino acid sequence of the compound,for the current flowing through the primary first winding of the current comparator,/or->For the voltage across the adjustable resistor,is equivalent to inductance L x Voltage of R 1 The resistance is the resistance of the resistor A.
Further, in the step S4, an embodiment is as follows:
the amplifier B passes through the resistor R of the resistor C 2 Converting the voltage across the inductance of the adjustable inductor and the resistance of the adjustable resistor into a current flowing through the load resistor F and the primary second winding series branch of the current comparator;
voltage across the adjustable inductor and the adjustable resistor:
in the formula (7), the amino acid sequence of the compound,is composed of adjustable inductor and adjustable resistorVoltage at terminal>For the voltage of the adjustable resistor, +.>Is the voltage of the adjustable inductor;
current flowing through the primary second winding of the current comparator:
in the formula (8), the amino acid sequence of the compound,for the current flowing through the second winding of the primary side of the current comparator,/or->For the voltage of the adjustable resistor, +.>For the voltage of the adjustable inductor, R 2 The resistance is the resistance of the resistor C.
Further, in the step S5, an embodiment is as follows:
regulating the number of turns N of the primary first winding of the current comparator 1 And the number of turns N of the primary side second winding of the current comparator 2 Observing the pointer change of the zero indicator, when the pointer of the zero indicator points to zero, the ampere turn of the primary winding of the current comparator is balanced, and at the moment, the equivalent alternating current resistance value of the cable conductor with the large section can be calculated from the adjustable inductor and the adjustable resistor as follows:
R x ＝N 2 KRR 1 /N 1 R 2 (9)
in the formula (9), R x Is equivalent to alternating current resistance, N 2 The number of turns of the second winding of the primary side of the current comparator is K is the proportionality coefficient of the current transformer, R is the resistance of the adjustable resistor, R 1 Resistance A, N 1 For the number of turns of the primary winding of the current comparator, R 2 The resistance is the resistance of the resistor C.
The beneficial effects of the invention are as follows:
1. the principle is simple, and convenient operation only needs to adjust adjustable inductor and adjustable resistor just can realize the measurement of big cross-section cable conductor alternating current equivalent resistance.
2. The sensitivity of the zero indicator of the current comparator is relatively high, and the ampere turn balance of the primary winding of the current comparator is realized by increasing the sensitivity of the zero indicator, so that the testing precision and the anti-interference capability can be improved.
3. The equivalent inductance of the large-section cable conductor can be obtained while the alternating-current equivalent resistance of the large-section cable conductor is obtained, and experimental basis is provided for analyzing the alternating-current characteristics of the large-section cable conductor.
Drawings
FIG. 1 is a schematic diagram of a large cross section cable conductor AC equivalent resistance test system and method based on a current comparator;
in the figure: 1. an alternating current source; 2. a large section cable conductor; 3. a current transformer; 4. an adjustable inductor; 5. an adjustable resistor; 6. an amplifier A; 7. an amplifier B; 8. a current comparator; 81. a primary side first winding of the current comparator; 82. a primary side second winding of the current comparator; 9. a zero indicator; 10. a resistor A; 11. a resistor B; 12. a resistor C; 13. a resistor D; 14. a load resistor E; 15. and a load resistor F.
Detailed Description
As shown in fig. 1, the present embodiment includes: the current source 1, the large-section cable conductor 2, the current transformer 3, the adjustable inductor 4, the adjustable resistor 5, the amplifier A6, the amplifier B7, the current comparator 8, the current comparator primary side first winding 81, the current comparator primary side second winding 82, the zero indicator 9, the resistor A10, the resistor B11, the resistor C12, the resistor D13, the load resistor E14 and the load resistor F15.
One end of an alternating current source 1 is connected with the head end of a large-section cable conductor 2, the tail end of the large-section cable conductor 2 is connected with one end of the primary side of a current transformer 3, the other end of the primary side of the current transformer 3 is connected with the other end of the alternating current source 1, an adjustable inductor 4 is connected with an adjustable resistor 5 in series, two ends of the adjustable inductor 4 and the adjustable resistor 5 are respectively connected with two ends of the secondary side of the current transformer 3, the other end of the adjustable resistor 5 connected with the adjustable inductor 4 is connected with the ground, the negative polarity input end of an amplifier A6 is connected with the head end of the large-section cable conductor 2 through a resistor A10, the positive polarity input end of the amplifier A6 is connected with a resistor B11, the other end of the resistor B11 is connected with the ground, the output end of the amplifier A6 is sequentially connected with the input end of the amplifier A6 through a first winding 81 of the primary side of the current comparator and a load resistor E14, the negative polarity input end of the amplifier B7 is connected with the input end of the adjustable inductor 4 and the load resistor E14 through a resistor C12, the positive polarity input end of the amplifier B7 is connected with the negative polarity end of the load resistor B7 through a second winding D7, and the current input end of the load resistor B7 is sequentially connected with the positive polarity end of the load 7 is connected with the load 7 through the load winding B9.
The alternating current source 1 is used for generating an alternating current source;
the large-section cable conductor 2 is used as a conductor to be tested;
the current transformer 3 is used for current conversion;
the adjustable inductor 4 is used for adjusting the inductance;
the adjustable resistor 5 is used for adjusting the resistance;
the amplifier A6 is used for passing through the resistor R of the resistor A10 1 Converting the voltage across the large section cable conductor 2 into a current flowing through the load resistor E14 and the series branch of the primary first winding 81 of the current comparator;
the amplifier B7 is used for passing through a resistor R of a resistor C12 2 Converting the voltage across the inductance of the adjustable inductor 4 and the resistance of the adjustable resistor 5 into a current flowing through the series branch of the load resistor F15 and the primary second winding 82 of the current comparator;
the current comparator 8, the primary side first winding 81 and the primary side second winding 82 are used for balancing ampere turns of the primary side winding of the current comparator, and the equivalent alternating current resistance value of the large-section cable conductor 2 is calculated from the adjustable inductor 4 and the adjustable resistor 5
The zero indicator 9 is used for representing the ampere turn balance of the primary winding of the current comparator when the pointer thereof points to zero.
The implementation of this example is as follows:
as shown in fig. 1, the device mainly comprises an alternating current source 1, a large-section cable conductor 2, a current transformer 3, an adjustable reactor 4, an adjustable resistor 5, an amplifier A6, an amplifier B7, a current comparator 8, a zero indicator 9 and the like.
The alternating current source 1 generates a sinusoidal excitation current with a frequency fIts equivalent ac resistance R at large section cable conductor 2 x The voltage is generated, and the voltage formula is as follows:
in the formula (1), the components are as follows,is equivalent to an alternating current resistor R x Voltage of>Is current, R x Is equivalent to an alternating current resistor.
L on equivalent inductance x Generating a voltage, wherein the voltage formula is as follows:
in the formula (2), the amino acid sequence of the compound,is equivalent to inductance L x Is the frequency, L x Is equivalent to electricityFeel (I)>Is a current.
The scaling factor K of the current transformer 3 will be the current of the main loopConverted into a current through the series branch of the adjustable inductor 4 and the adjustable resistor 5 +.>. This current produces a voltage across the inductance of the adjustable inductor 4, the voltage formula:
in the formula (3), the amino acid sequence of the compound,is the voltage across the inductor, f is the frequency, L is the inductance value of the adjustable inductor 4, < ->The current of the series branch for the adjustable resistor 5.
A voltage is generated across the resistance of the adjustable resistor 5, the voltage formula:
in the formula (4), the amino acid sequence of the compound,for the voltage across the adjustable resistor 5, R is the resistance of the adjustable resistor 5, +.>The current of the series branch for the adjustable resistor 5.
The negative polarity input end of the amplifier A6 is connected with the head end of the large-section cable conductor 2 through the resistor A10, the positive polarity input end of the amplifier A6 is connected with the tail end of the large-section cable conductor 2, and the output end of the amplifier A6 is fed back to the negative polarity input end of the amplifier A6 through the primary side first winding 81 of the current comparator and the load resistor E14.
The amplifier A6 passes through the resistor R of the resistor 10 1 The voltage across the large-section cable conductor 2 is converted into a current through the series branch of the load resistor E14 and the primary first winding 81 of the current comparator,
voltage across large section cable conductor 2:
in the formula (5), the amino acid sequence of the compound,for the voltage across the large-section cable conductor 2, < >>For the voltage across the adjustable resistor 5, < >>Is equivalent to inductance L x Is set in the above-described voltage range.
Current of the series branch:
in the formula (6), the amino acid sequence of the compound,for the current through the primary first winding 81 of the current comparator,/>For the voltage across the adjustable resistor 5, < >>Is equivalent to inductance L x Voltage of R 1 Is the resistance of resistor 10.
The negative polarity input of the amplifier B7 is connected to the high voltage terminals of the adjustable inductor 4 and the adjustable resistor 5 through a resistor C12, the positive polarity input of the amplifier B7 is connected to ground through a resistor D13, and the output of the amplifier B7 is fed back to the negative polarity input of the amplifier B7 through the current comparator primary side second winding 82 and the load resistor F15.
Amplifier B7 has a resistance R through a resistance C12 2 The voltage across the inductance of the adjustable inductor 4 and the resistance of the adjustable resistor 5 is converted into a current flowing through the series branch of the load resistor F15 and the primary second winding 82 of the current comparator.
The voltage across the adjustable inductor 4 and the adjustable resistor 5:
in the formula (7), the amino acid sequence of the compound,for the voltage across the adjustable inductor 4 and the adjustable resistor 5 +.>For the voltage of the adjustable resistor 5 +.>Is the voltage of the adjustable inductor 4.
The current flowing through the primary second winding 82 of the current comparator:
in the formula (8), the amino acid sequence of the compound,comparator for flowing currentCurrent of primary second winding 82, +.>For the voltage of the adjustable resistor 5,for the voltage of the adjustable inductor 4, R 2 Is the resistance of the resistor C12.
Regulating the number of turns N of the primary winding 81 of the current comparator 1 And current comparator primary second winding 82 turns N 2 Observing the pointer change of the zero indicator 9, when the pointer of the zero indicator 9 points zero, the ampere turns of the primary winding of the current comparator are balanced, and at the moment, the equivalent alternating current resistance value of the large-section cable conductor 2 can be calculated from the adjustable inductor 4 and the adjustable resistor 5 as follows:
R x ＝N 2 KRR 1 /N 1 R 2 (9)
in the formula (9), R x Is equivalent to alternating current resistance, N 2 For the number of turns of the primary second winding 82 of the current comparator, K is the proportionality coefficient of the current transformer 3, R is the resistance of the adjustable resistor 5, R 1 Resistance as resistor 10, N 1 81 turns of the primary winding of the current comparator, R 2 Is the resistance of the resistor C12.
The equivalent inductance of the large-section cable conductor 2 is
L x ＝N 2 KLR 1 /N 1 R 2 (10)
In the formula (10), L x Equivalent inductance of large-section cable conductor 2, N 2 For the number of turns of the primary second winding 82 of the current comparator, K is the proportionality coefficient of the current transformer 3, L is the inductance value of the adjustable inductor 4, R 1 Resistance as resistor 10, N 1 81 turns of the primary winding of the current comparator, R 2 Is the resistance of the resistor C12.
In the embodiment, the model of an alternating current source is NHAC10V-100A of Jinan Nehua electromechanical device Limited company, the model of a differential amplifier is Nanjing Hongbin weak signal detection Limited company 815A, the model of a current transformer is CTA200 of Shenzhen electric Limited company, and the model of a digital acquisition card is NIUSB 6009.
Claims (7)
1. The large-section cable conductor alternating-current equivalent resistance testing system based on the current comparator is characterized by comprising an alternating-current source (1), a large-section cable conductor (2), a current transformer (3), an adjustable inductor (4), an adjustable resistor (5), an amplifier A (6), an amplifier B (7), a current comparator (8), a primary side first winding (81) of the current comparator, a primary side second winding (82) of the current comparator, a zero indicator (9), a resistor A (10), a resistor B (11), a resistor C (12), a resistor D (13), a load resistor E (14) and a load resistor F (15);
one end of an alternating current source (1) is connected with the head end of a large-section cable conductor (2), the tail end of the large-section cable conductor (2) is connected with one end of the primary side of a current transformer (3), the other end of the primary side of the current transformer (3) is connected with the other end of the alternating current source (1) to be grounded, an adjustable inductor (4) and an adjustable resistor (5) are connected in series, two ends of the adjustable inductor (4) and the adjustable resistor (5) are respectively connected with two ends of the secondary side of the current transformer (3), the adjustable resistor (5) is connected with the two ends of the secondary side of the current transformer (3), the other end of the adjustable resistor (5) is connected with the ground, the negative polarity input end of an amplifier A (6) is connected with the head end of the large-section cable conductor (2) through a resistor A (10), the positive polarity input end of the amplifier A (6) is connected with the tail end of the large-section cable conductor (2), the positive polarity input end of the amplifier A (6) is connected with a resistor B (11), the other end of the resistor B (11) is connected with the ground, the output end of the amplifier A (6) is sequentially connected with the negative polarity (81) of the negative polarity (12) of the current (6) through the first current-side (14) and the negative polarity (1) of the amplifier (6) and the negative polarity (1) of the amplifier (6) is connected with the negative polarity (81), the positive polarity input end of the amplifier B (7) is connected with the ground through a resistor D (13), the output end of the amplifier B (7) is connected with the negative polarity input end of the amplifier B (7) through a primary side second winding (82) of the current comparator and a load resistor F (15) in sequence, and the zero indicator (9) is connected with a secondary side winding of the current comparator (8);
the alternating current source (1) is used for generating an alternating current source;
the large-section cable conductor (2) is used as a conductor to be tested;
the current transformer (3) is used for current conversion;
the adjustable inductor (4) is used for adjusting the inductance;
the adjustable resistor (5) is used for adjusting the resistance;
the amplifier A (6) is used for passing through the resistor R of the resistor A (10) 1 Converting the voltage across the large section cable conductor (2) into a current flowing through the series branch of the load resistor E (14) and the primary first winding (81) of the current comparator;
the amplifier B (7) is used for passing through a resistor R of a resistor C (12) 2 Converting the voltage across the inductance of the adjustable inductor (4) and the resistance of the adjustable resistor (5) into a current flowing through the series branch of the load resistor F (15) and the primary second winding (82) of the current comparator;
the current comparator (8), the current comparator primary side first winding (81) and the current comparator primary side second winding (82) are used for balancing ampere turns of the current comparator primary side winding, and equivalent alternating current resistance values of the large-section cable conductor (2) are calculated from the adjustable inductor (4) and the adjustable resistor (5);
the zero indicator (9) is used for representing the ampere turn balance of the primary winding of the current comparator when the pointer thereof indicates zero.
2. A large-section cable conductor alternating-current equivalent resistance testing method based on a current comparator is characterized by comprising the following steps:
step S1, obtaining the equivalent alternating current resistance R of the large-section cable conductor (2) x Voltage of equivalent inductance L x Is a voltage of (2);
step S2, obtaining voltages at two ends of the inductance of the adjustable inductor (4) and voltages at two ends of the resistance of the adjustable resistor (5);
s3, obtaining the current of a branch of a primary side first winding (81) of the current comparator;
s4, obtaining the current of a branch of a primary side second winding (82) of the current comparator;
and S5, obtaining the equivalent alternating current resistance value of the large-section cable conductor (2).
3. The method for testing the ac equivalent resistance of the large-section cable conductor based on the current comparator according to claim 2, wherein the implementation manner of the step S1 is as follows:
the AC current source (1) generates a sinusoidal excitation current with frequency fIts equivalent alternating current resistance R in large section cable conductor (2) x The voltage is generated, and the voltage formula is as follows:
in the formula (1), the components are as follows,is equivalent to an alternating current resistor R x Voltage of>Is current, R x Is equivalent to an alternating current resistor;
l on equivalent inductance x Generating a voltage, wherein the voltage formula is as follows:
in the formula (2), the amino acid sequence of the compound,is equivalent to inductance L x Is the frequency, L x Is equivalent inductance->Is a current.
4. The method for testing the ac equivalent resistance of the large-section cable conductor based on the current comparator according to claim 2, wherein the implementation manner of the step S2 is as follows:
the proportionality coefficient K of the current transformer (3) is used for leading the current of the main loopConverted into a current through a series branch of an adjustable inductor (4) and an adjustable resistor (5)>The current generates a voltage across the inductance of the adjustable inductor (4), the voltage formula:
in the formula (3), the amino acid sequence of the compound,is the voltage at two ends of the inductor, f is the frequency, L is the inductance value of the adjustable inductor (4), and +.>-current for the series branch of the adjustable resistor (5);
generating a voltage across the resistance of the adjustable resistor (5), the voltage formula:
in the formula (4), the amino acid sequence of the compound,is the voltage across the adjustable resistor (5), R is the resistance of the adjustable resistor (5)>The current of the series branch is an adjustable resistor (5).
5. The method for testing the ac equivalent resistance of the large-section cable conductor based on the current comparator according to claim 2, wherein the implementation manner of the step S3 is as follows:
the amplifier A (6) passes through the resistor R of the resistor A (10) 1 Converting the voltage across the large section cable conductor (2) into a current flowing through the series branch of the load resistor E (14) and the primary first winding (81) of the current comparator;
voltage across large section cable conductor (2):
in the formula (5), the amino acid sequence of the compound,for the voltage across the large-section cable conductor (2), ->For the voltage across the adjustable resistor (5), ->Is equivalent to inductance L x Is a voltage of (2);
current of the series branch:
in the formula (6), the amino acid sequence of the compound,for the current flowing through the primary first winding (81) of the current comparator,/for the current>For the voltage across the adjustable resistor (5), ->Is equivalent to inductance L x Voltage of R 1 Is the resistance of the resistor A (10).
6. The method for testing the ac equivalent resistance of the large-section cable conductor based on the current comparator according to claim 2, wherein the implementation manner of the step S4 is as follows:
the amplifier B (7) passes through the resistor R of the resistor C (12) 2 Converting the voltage across the inductance of the adjustable inductor (4) and the resistance of the adjustable resistor (5) into a current flowing through the series branch of the load resistor F (15) and the primary second winding (82) of the current comparator;
voltage across the adjustable inductor (4) and the adjustable resistor (5):
in the formula (7), the amino acid sequence of the compound,for the voltage across the adjustable inductor (4) and the adjustable resistor (5), ->For the voltage of the adjustable resistor (5), ->Is the voltage of the adjustable inductor (4);
the current flowing through the primary second winding (82) of the current comparator:
in the formula (8), the amino acid sequence of the compound,for the current flowing through the primary second winding (82) of the current comparator,/for the current>For the voltage of the adjustable resistor (5),for the voltage of the adjustable inductor (4), R 2 Is the resistance of the resistor C (12).
7. The method for testing the ac equivalent resistance of the large-section cable conductor based on the current comparator according to claim 2, wherein the implementation manner of the step S5 is as follows:
regulating the number of turns N of the primary first winding (81) of the current comparator 1 And the number of turns N of the primary second winding (82) of the current comparator 2 Observing the pointer change of the zero indicator (9), when the pointer of the zero indicator (9) points to zero, the primary winding ampere turn of the current comparator is balanced, and at the moment, the equivalent alternating current resistance value of the large-section cable conductor (2) can be calculated from the adjustable inductor (4) and the adjustable resistor (5) as follows:
R x ＝N 2 KRR 1 /N 1 R 2 (9)
in the formula (9), R x Is equivalent to alternating current resistance, N 2 The number of turns of the second winding (82) at the primary side of the current comparator is K is the proportionality coefficient of the current transformer (3), R is the resistance of the adjustable resistor (5), R 1 Resistance A (10), N 1 For the number of turns of the primary first winding (81) of the current comparator, R 2 Is the resistance of the resistor C (12).
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| CN202111254349.4A CN113933593B (en) | 2021-10-27 | 2021-10-27 | Current comparator-based large-section cable conductor alternating-current equivalent resistance test system and method |
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