CN115792774A - Variable ratio measuring device and method for straight-through current transformer - Google Patents
Variable ratio measuring device and method for straight-through current transformer Download PDFInfo
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Abstract
The invention discloses a variable ratio measuring device and method for a straight-through current transformer. A cross-core current transformer in a cross-core current transformer transformation ratio value measuring device comprises a cross-core primary winding and a cross-core secondary winding; the measuring device comprises: the punching auxiliary winding with the preset number of turns is arranged on one side of the punching secondary winding; the straight-through primary winding is used for passing current, and the straight-through secondary winding and the straight-through auxiliary winding mutually induce corresponding voltage; the first voltage collector is used for measuring voltages at two ends of the straight-through secondary winding; the second voltage collector is used for measuring the voltage at two ends of the punching auxiliary winding; and the processor is respectively connected with the first voltage collector and the second voltage collector and is used for calculating the variable ratio of the feedthrough current transformer according to the first voltage collected by the first voltage collector, the second voltage collected by the second voltage collector and the preset turns. The variable ratio measurement of the straight-through current transformer disclosed by the invention can be used for rapidly and accurately testing the variable ratio of the current transformer.
Description
Technical Field
The invention relates to the technical field of power systems, in particular to a device and a method for measuring a variable ratio of a feed-through current transformer.
Background
The current transformer is a device widely used in the power industry, and according to related regulations, before and after the current transformer is put into operation, the transformation ratio value (the ratio value of primary current to secondary current) of the current transformer needs to be tested on site for many times, and the change of the value reflects the performance states of a winding, an iron core and the like of the current transformer.
At present, the variable ratio of the current transformer can be calculated by adopting a current method or a voltage method. Fig. 1 is a wiring diagram for a test of calculating a transformation ratio of a current transformer by using a current method in the prior art. As shown in FIG. 1, I is a current source, and an ammeter measures a primary current A of a current transformer 1 The ammeter measures the secondary current A of the current transformer 2 The ratio of the current transformer is the primary winding current A 1 With a secondary winding current A 1 The ratio is:
fig. 2 is a wiring diagram for a test of calculating a ratio of a current transformer by using a voltage method in the prior art. As shown in FIG. 2, V S The voltage source is a voltage source, a voltmeter measures the voltage V at two ends of the secondary winding, a millivolt voltmeter measures the voltage mV at two ends of the primary winding, and the transformation ratio of the current transformer is
The current method or the voltage method is adopted to measure the transformation ratio value of the current transformer, the measuring device is large in size and inconvenient to carry, and in addition, the problems of system error, thick test line, high wiring requirement and low test efficiency exist.
Disclosure of Invention
The invention provides a variable ratio measuring device and method of a straight-through current transformer, which are used for solving the problems of large volume, inconvenience in carrying and inaccurate measurement of the variable ratio measuring device of the straight-through current transformer in the prior art and can realize light, rapid and accurate measurement of the variable ratio of the current transformer.
In a first aspect, an embodiment of the present invention provides a transformation ratio measuring apparatus for a feedthrough current transformer, where the feedthrough current transformer includes a feedthrough primary winding and a feedthrough secondary winding; the measuring device includes:
the punching auxiliary winding is arranged at one side of the punching secondary winding and has a preset number of turns; the straight-through primary winding is used for passing current, and the straight-through secondary winding and the straight-through auxiliary winding mutually induce corresponding voltage;
the first voltage collector is used for measuring the voltage at two ends of the straight-through secondary winding;
the second voltage collector is used for measuring the voltage at two ends of the straight-through auxiliary winding;
and the processor is respectively connected with the first voltage collector and the second voltage collector and is used for calculating the transformation ratio of the feedthrough current transformer according to the first voltage collected by the first voltage collector, the second voltage collected by the second voltage collector and the preset turns.
Optionally, the apparatus for measuring a transformation ratio of a feedthrough current transformer further comprises: the overvoltage comparator is respectively connected with the output end of the first voltage collector and the control end of the control switch;
the first end of the control switch is connected with the processor, and the second end of the control switch is connected with the feed-through primary winding;
and when the first voltage acquired by the overvoltage comparator is greater than the reference voltage, controlling the control switch to be switched off.
Optionally, the control switch is a relay.
Optionally, the apparatus for measuring a transformation ratio of a feedthrough current transformer further comprises: and one end of the sinusoidal signal generator is connected with the processor, and the other end of the sinusoidal signal generator is connected with the first end of the control switch.
Optionally, the apparatus for measuring a transformation ratio of a feedthrough current transformer further comprises: and one end of the current power amplifier is connected with the other end of the sinusoidal signal generator, and the other end of the current power amplifier is connected with the first end of the control switch.
Optionally, the apparatus for measuring a transformation ratio of a feedthrough current transformer further comprises: the display screen is connected with the processor, the overvoltage comparator is further connected with the processor, and the processor is used for controlling the display screen to display the comparison result of the overvoltage comparator.
Optionally, the apparatus for measuring a transformation ratio of a feedthrough current transformer further comprises: the analog-to-digital converter is respectively connected with the processor, the first voltage collector and the second voltage collector; the first voltage and the second voltage are both converted into digital signals and are output to the processor.
Optionally, the variable ratio of the feedthrough current transformer is obtained by dividing the second voltage by the first voltage and multiplying the second voltage by the preset number of turns.
Optionally, the first voltage collector and the second voltage collector are both voltage meters.
In a second aspect, an embodiment of the present invention further provides a method for measuring a transformation ratio of a feedthrough current transformer, which is implemented based on the device for measuring a transformation ratio of a feedthrough current transformer according to any one of the first aspects, and includes the following steps:
acquiring a first voltage acquired by the first voltage acquirer and a second voltage acquired by the second voltage acquirer; and the preset number of turns of the feedthrough auxiliary winding;
and acquiring the ratio of the first voltage to the second voltage and the product of the ratio and the preset turns as the variable ratio of the feedthrough current transformer.
The embodiment of the invention provides a device and a method for measuring a transformation ratio value of a straight-through current transformer, wherein the straight-through current transformer in the device comprises a straight-through primary winding and a straight-through secondary winding; the measuring device comprises: the punching auxiliary winding with the preset number of turns is arranged on one side of the punching secondary winding; the straight-through primary winding is used for passing current, and the straight-through secondary winding and the straight-through auxiliary winding mutually induce corresponding voltage; the first voltage collector is used for measuring voltages at two ends of the straight-through secondary winding; the second voltage collector is used for measuring the voltage at two ends of the punching auxiliary winding; and the processor is respectively connected with the first voltage collector and the second voltage collector and is used for calculating the variable ratio of the feedthrough current transformer according to the first voltage collected by the first voltage collector, the second voltage collected by the second voltage collector and the preset turns. The variable ratio of the current transformer can be tested quickly and accurately through the preset turns of the first voltage, the second voltage and the punching auxiliary winding, the error is reduced favorably, and the measuring device is light and high in test efficiency.
It should be understood that the statements in this section do not necessarily identify key or critical features of the embodiments of the present invention, nor do they necessarily limit the scope of the invention. Other features of the present invention will become apparent from the following description.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a wiring diagram for testing the current transformer ratio value calculated by current method in the prior art;
FIG. 2 is a wiring diagram for testing the calculation of the ratio of a current transformer by a voltage method in the prior art;
FIG. 3 is an equivalent circuit diagram of a current transformer ratio value tested by a voltage method in the center of the prior art;
fig. 4 is a schematic structural diagram of a transformation ratio measuring apparatus of a feedthrough current transformer according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of another apparatus for measuring a transformation ratio of a feedthrough current transformer according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of another apparatus for measuring a transformation ratio of a feedthrough current transformer according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of another apparatus for measuring a transformation ratio of a feedthrough current transformer according to an embodiment of the present invention;
fig. 8 is a schematic structural diagram of another apparatus for measuring a transformation ratio of a feedthrough current transformer according to an embodiment of the present invention;
fig. 9 is a schematic structural diagram of another apparatus for measuring a transformation ratio of a feedthrough current transformer according to an embodiment of the present invention;
fig. 10 is a schematic flow chart of a method for measuring a transformation ratio of a feedthrough current transformer according to an embodiment of the present invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in other sequences than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
Before describing the scheme of the embodiment of the present invention in detail, a description is first given to a measurement principle of a variable ratio value of a current transformer in an existing power system.
The working principle of the current transformer is the same as that of a transformer, and the current transformer follows the electromagnetic induction principle: the alternating current in the primary winding generates alternating main magnetic flux in the iron core, the main magnetic flux induces induced electromotive force in the secondary winding, and the induced electromotive force generates secondary current in a closed secondary loop consisting of the winding and the load. According to the electromagnetic induction principle, the ratio of the number of turns of the primary winding to the number of turns of the secondary winding is used for determining the transformation ratio of the current transformer.
According to the electrical principle, the turn ratio of the primary winding to the secondary winding is equal to the ratio of the induced voltages of the primary winding to the secondary winding and also equal to the reciprocal of the current ratio of the primary winding to the secondary winding. Therefore, the turn ratio, namely the variable ratio, can be calculated by measuring the voltage ratio and the current ratio.
The primary side rated current of a current transformer in a power system is in a common range of 100A-5000A, the common power range of the existing device for testing the transformation ratio of the current transformer by adopting a current method is 3kVA-5kVA, the output current range is 0A-1000A, and a large current generator is formed by using a mechanical voltage regulator, a current booster and other devices inside the device. However, the method for measuring the transformation ratio has the problems of large volume, heavy weight and inconvenience in carrying, and in addition, the test line is thick, the wiring requirement is high and the test efficiency is low.
In recent years, the value of the transformation ratio of the current transformer is measured by adopting a voltage methodThe method is developed and popularized rapidly, but systematic measurement errors exist by adopting a voltage method. Fig. 3 is an equivalent circuit diagram of a current transformer ratio value measured by a voltage method in the center of the prior art. As shown in FIG. 3, V S A voltmeter measures the voltage V across the secondary winding, and a millivolt voltmeter measures the voltage mV across the primary winding, as a voltage source. I is e For exciting current of current transformer, U 1 For primary voltage of current transformer, U 2 ' is the secondary voltage of the current transformer converted to the primary side, r 1 And x 1 Respectively a primary coil resistance, a leakage reactance, r of the current transformer 2 ' and x 2 ' secondary coil resistance, leakage reactance, Z of current transformer converted to primary side m Is a current transformer excitation impedance.
Specifically, with continued reference to fig. 3, when the ratio of the current transformer is measured by the voltage method, the primary coil is open-circuited, and the test voltage U applied to the secondary coil is now applied 2 ', also the excitation voltage of the transformer, I e Therefore, U 'can be obtained by the exciting current generated under the exciting voltage' 2 +I e ×(r′ 2 +jx′ 2 ) And = U. U is the actual voltage across the secondary winding.
Wherein, I e ×(r′ 2 +jx′ 2 ) For the voltage drop caused by the field current through the secondary winding impedance,
the existing equipment considers that the voltage drop is not large, neglects the term, considers that the voltage ratio of the two ends of the primary winding and the secondary winding is equal to the turn ratio of the current transformer, namely U 1 /U＝U 1 /U′ 2 . Note that I is ignored e ×(r′ 2 +jx′ 2 ) The reason for (a) is on the one hand to consider r 2 ′、x 2 ' it is not easy to measure (if these values are measured, assistance from other equipment is required), and the two values are typically not large (typically not more than 10 Ω). On the other hand, when the voltage method is used for testing, the amplitude of the applied voltage is controlled to ensure that the exciting current I at the moment e Not exceeding 10mA. Therefore, when the existing voltage method is adopted for testing, the system error exists, particularly along with the change of the current transformerThe ratio increases and the voltage induced in the primary winding decreases, the voltage drop across the secondary winding impedance being negligible with respect to the voltage induced in the primary winding. In addition, when a voltage method is adopted for testing, the primary coil is open-circuited, the magnetic density of the iron core is high, the magnetic flux of the iron core is easily saturated when voltage is applied to the secondary winding, and the exciting current is rapidly increased.
For example, taking 1 field test data of a current transformer for measuring 10kV and 5000A/5A as an example, the applied voltage of the secondary coil is 25V, the measured voltage of the primary coil is 25mV, the excitation current of the secondary coil is about 10mA, the resistance and the leakage reactance of the secondary coil are about 15 omega, and I is e ×(r′ 2 +jx′ 2 ) =150mV, the error due to neglecting the impedance drop of the secondary winding has reached 0.6% (error of 150mV compared to 25V).
Therefore, in the prior art, a voltage method is adopted to measure the variable ratio of the current transformer, so that on one hand, system errors caused by impedance voltage drop in a secondary winding can be avoided; on the other hand, the device has large testing power, large volume, inconvenient carrying and complex use.
Next, a technical solution of the apparatus for measuring a transformation ratio of a feedthrough current transformer according to an embodiment of the present invention is explained in detail.
Fig. 4 is a schematic structural diagram of a device for measuring a transformation ratio of a feedthrough current transformer according to an embodiment of the present invention. As shown in fig. 4, the feedthrough current transformer 10 includes a feedthrough primary winding 100 and a feedthrough secondary winding 200; the measuring device comprises: the punching auxiliary winding 300 with the preset number of turns is arranged on one side of the punching secondary winding 200; the straight-through primary winding 100 is used for passing current, and the straight-through secondary winding 200 and the straight-through auxiliary winding 300 mutually induce corresponding voltage; first voltage collector V for measuring voltage at two ends of core-through secondary winding 200 11 (ii) a Second voltage collector V for measuring voltages at two ends of punching auxiliary winding 22 (ii) a A processor 400, the processor 400 and the first voltage collector V 11 And a second voltage collector V 22 Connection for collecting a voltage according to a first voltage V 11 Collected first voltage and second voltage collector V 22 The second collected voltage and the preset number of turnsThe variation ratio of the feedthrough current transformer 10 is calculated.
Illustratively, with continued reference to FIG. 4, a current source I 1 A fixed amount of alternating current may be applied to the through-core primary winding 100, which current is used to establish an excitation flux to the core. The piercing auxiliary winding 300 can be a rubber insulation test wire pierced with a plurality of turns on site as an auxiliary measurement winding, and a second voltage collector V is used 22 The voltage across the feedthrough auxiliary winding 300 is measured, i.e. the second voltage may be U 22 For example, the predetermined number of turns T of the piercing auxiliary winding 300 may be 1 to 10 turns. Second voltage collector V 22 Measuring the terminal voltage of the auxiliary winding, i.e. the second voltage may be U 22 。
Illustratively, the processor 400 may employ an STM32F103E chip. First voltage collector V 11 And a second voltage sampler V 22 The TL082 op-amp signal may be processed.
In particular, with continued reference to FIG. 4, processor 400 may collect V from a first voltage 11 The collected first voltage U 11 And a second voltage collector V 22 The second voltage U is collected 22 And calculating the preset turns T of the feedthrough auxiliary winding 300, so as to obtain the turn ratio of the feedthrough secondary winding 200 to the feedthrough primary winding 100, that is, the variable ratio of the feedthrough current transformer 10.
Further, with continued reference to fig. 4, by applying a constant alternating current to the piercing-through primary winding 100, the alternating current generates a main magnetic flux Φ in the iron core, the main magnetic flux Φ generates an induced electromotive force E2 in the piercing-through secondary winding 200, and an induced electromotive force E1 is generated in the piercing-through auxiliary winding 300, as can be known from the electromagnetic induction principle:
E1＝4.44*N1*f*Φ；
E2＝4.44*N2*f*Φ；
wherein N1 and N2 are the number of turns of the feedthrough primary winding 100 and the feedthrough secondary winding 200, respectively, and f is the frequency.
Specifically, the induced voltage in the feedthrough secondary winding 200 and the induced voltage in the feedthrough auxiliary winding 300 are proportional to the number of winding turns thereof, since the coils of the feedthrough secondary winding 200,The cross-core auxiliary winding 300 coils are all kept in an open circuit state, and no current flows in the coils. Therefore, the voltage across the coil is identical to the induced electromotive force, that is, the first voltage collector V 11 The collected first voltage U 11 And a second voltage collector V 22 The second voltage U is collected 22 The number of turns of the straight-through primary winding 100 and the straight-through secondary winding 200 is proportional, and the number of turns of the straight-through auxiliary winding 300 is known (during testing, a tester is used for winding the straight-through winding, generally the straight-through winding is performed for 1 turn, and a plurality of turns can be wound when the transformation ratio is large), so that the accurate turn ratio of the straight-through secondary winding 200 to the straight-through auxiliary winding 300 can be obtained, and further the transformation ratio of the straight-through current transformer 10 is obtained (the straight-through primary winding 100 in the straight-through current transformer 10 is the straight-through 1 turn).
Optionally, fig. 5 is a schematic structural diagram of another apparatus for measuring a transformation ratio of a feedthrough current transformer according to an embodiment of the present invention. As shown in fig. 5, the apparatus for measuring the transformation ratio of the feedthrough current transformer further comprises: an overvoltage comparator 500 and a control switch 600, the overvoltage comparator 500 and the first voltage collector V respectively 11 Is connected with the control terminal of the control switch 600; wherein, the first end of the control switch 600 is connected with the processor 400, and the second end is connected with the feedthrough primary winding 100; when the first voltage U is obtained by the over-voltage comparator 500 11 And when the reference voltage is greater than the reference voltage, the control switch 600 is controlled to be turned off.
Illustratively, the over-voltage comparator 500 may be a peak circuit based on the operational amplifier OP277, which is divided and then enters the LM311 comparator.
In particular, with continued reference to fig. 4 and 5, overvoltage comparator 500 can track the value of the voltage across feedthrough secondary winding 200, i.e., first voltage U 11 When the voltage exceeds the reference voltage, the processor 400 controls the control switch 600 to be switched off, so that the winding breakdown caused by overlarge voltage at two ends of the through secondary winding 200 of the through current transformer 10 is prevented; in addition, when the overvoltage comparator 500 obtains the first voltage U 11 When the voltage is higher than the reference voltage, the overvoltage comparator 500 transmits an output signal to the processor 400, which indicates that the feedthrough secondary winding 200 is overvoltage, and the processor 400 controls the control switch 600 to be turned off to switch off the feedthrough secondary windingThereby realizing overvoltage protection.
Optionally, with continued reference to fig. 4 and 5, the control switch 600 is a relay.
Specifically, the control switch 600 is a relay, and when the current passing through the feedthrough primary winding 100 of the feedthrough current transformer 10 is too large or reaches a certain amount, the relay is automatically turned off, thereby avoiding the occurrence of electrical safety accidents.
Optionally, fig. 6 is a schematic structural diagram of another apparatus for measuring a transformation ratio of a feedthrough current transformer according to an embodiment of the present invention. As shown in fig. 6, the apparatus for measuring the transformation ratio of the feedthrough current transformer further comprises: and a sinusoidal signal generator 700, wherein one end of the sinusoidal signal generator 700 is connected with the processor 400, and the other end is connected with the first end of the control switch 600.
For example, with continued reference to fig. 4 and 6, the sinusoidal signal generator 700 may generate a power frequency sinusoidal voltage signal, and further, the processor 400 may control the sinusoidal signal generator 700 to output a sinusoidal voltage signal value, which can be transmitted to the feedthrough primary winding 100 through the control switch 600, so that the feedthrough current transformer 10 operates normally. The sine signal generator 700 may be composed of a C8051F330 single chip microcomputer and a MAX506 model DAC chip.
Optionally, fig. 7 is a schematic structural diagram of another apparatus for measuring a transformation ratio of a feedthrough current transformer according to an embodiment of the present invention. As shown in fig. 7, the apparatus for measuring a transformation ratio of a feedthrough current transformer further includes: and a current power amplifier 800, wherein one end of the current power amplifier 800 is connected with the other end of the sinusoidal signal generator 700, and the other end of the current power amplifier 800 is connected with the first end of the control switch 600.
For example, the current power amplifier 800 may be a push-pull amplifier circuit based on MJ11032 and MJ11033, and the current power amplifier 800 may generate a constant amplitude alternating current for testing, the magnitude of which is proportional to the control signal output by the processor 400. In addition, the sinusoidal signal generator 700 generates a power frequency sinusoidal voltage signal to control the current power amplifier 800 to output a desired ac current with a constant amplitude. That is, the sinusoidal signal generator 700 generates a power frequency sinusoidal voltage signal that controls the magnitude of the output of the current power amplifier 800.
Specifically, with continued reference to fig. 4 and 7, the sinusoidal signal generator 700 generates a local frequency sinusoidal voltage signal to control the ac current with a constant amplitude required by the output of the current power amplifier 800, and the current is output to the feedthrough primary winding 100 of the feedthrough current transformer 10 through the control switch 600, so as to generate a main magnetic flux in the core, and the main magnetic flux generates induced electromotive force in the feedthrough secondary winding and the feedthrough auxiliary winding.
Optionally, fig. 8 is a schematic structural diagram of another apparatus for measuring a transformation ratio of a feedthrough current transformer according to an embodiment of the present invention. As shown in fig. 8, the apparatus for measuring a transformation ratio of a feedthrough current transformer further includes: the display screen 900, the display screen 900 is connected with the processor 400, the overvoltage comparator 500 is further connected with the processor 400, and the processor 400 is configured to control the display screen 900 to display the comparison result of the overvoltage comparator 500.
Specifically, with continued reference to fig. 8, the processor 400 is configured to control the display 900 to display the comparison result of the over-voltage comparator 500 when the over-voltage comparator 500 obtains the first voltage U 11 When the voltage is greater than the reference voltage, the overvoltage comparator 500 transmits the output signal to the processor 400, and the processor 400 can prompt a user that the piercing-through secondary winding 200 is overvoltage through the display screen 900, so that overvoltage protection is realized, and the user can conveniently check the overvoltage. It should be noted that the display screen 900 may also receive an input parameter of the user to the feedthrough current transformer variable ratio measuring apparatus, so as to implement human-computer interaction. Illustratively, the user input parameter may be the on and off of the control switch 600.
Optionally, fig. 9 is a schematic structural diagram of another apparatus for measuring a transformation ratio of a feedthrough current transformer according to an embodiment of the present invention. As shown in fig. 9, the apparatus for measuring the transformation ratio of the feedthrough current transformer further comprises: an analog-to-digital converter 1000 connected to the processor 400 and the first voltage collector V respectively 11 A second voltage collector V 22 Connecting; for applying a first voltage U 11 And a second voltage U 22 Are converted into digital signals and output to the processor 400.
As an example, the analog-to-digital converter 1000 may be model AD 7607.
Specifically, with continued reference to FIG. 9, the first voltage U 11 And a second voltage U 22 Is an analog signal. The analog-to-digital converter 1000 may convert analog signals with continuous time and continuous amplitude into digital signals with discrete time and discrete amplitude, and output the digital signals to the processor 400, so that the processor 400 controls the liquid crystal panel 900 and the sinusoidal signal generator 700 to operate normally.
Optionally, with continued reference to fig. 4, the transformation ratio of the feedthrough current transformer 10 is a second voltage U 22 Divided by a first voltage U 11 And multiplied by a preset number of turns.
For example, the transformation ratio of the feedthrough current transformer 10 may be represented as Q, and the preset number of turns may be recorded according to actual winding on site, and may be represented as T. Further, the turn ratio of the through secondary winding 200 to the through primary winding 100, i.e. the transformation ratio Q of the current transformer 10, can be expressed as
By adopting the method to calculate the variable ratio value, the system error caused by the impedance voltage drop in the secondary winding during the traditional voltage method test can be avoided, and the measurement precision of the variable ratio value is improved.
Optionally, with continued reference to fig. 4, a first voltage harvester V 11 And a second voltage collector V 22 All are voltage meters.
Specifically, a first voltage collector V 11 And a second voltage collector V 22 Respectively collecting first voltages U 11 And a second voltage U 22 Through the second voltage collector V 22 The voltage of the punching auxiliary winding can be measured instead of the voltage applied by the secondary winding, and the error caused by the exciting current can be avoided.
The embodiment of the invention provides a device for measuring a transformation ratio value of a straight-through current transformer, wherein the straight-through current transformer in the device comprises a straight-through primary winding and a straight-through secondary winding; the measuring device comprises: the punching auxiliary winding with the preset number of turns is arranged on one side of the punching secondary winding; the straight-through primary winding is used for passing current, and the straight-through secondary winding and the straight-through auxiliary winding mutually induce corresponding voltage; the first voltage collector is used for measuring voltages at two ends of the straight-through secondary winding; the second voltage collector is used for measuring the voltage at two ends of the punching auxiliary winding; and the processor is respectively connected with the first voltage collector and the second voltage collector and is used for calculating the variable ratio of the feedthrough current transformer according to the first voltage collected by the first voltage collector, the second voltage collected by the second voltage collector and the preset turns. The variable ratio of the current transformer can be quickly and accurately tested through the preset turns of the first voltage, the second voltage and the punching auxiliary winding, and the measuring device is light and high in test efficiency.
Based on the same inventive concept, an embodiment of the present invention further provides a method for measuring a transformation ratio value of a feedthrough current transformer, which is implemented based on the device for measuring a transformation ratio value of a feedthrough current transformer described in the foregoing embodiment, and fig. 10 is a schematic flow diagram of the method for measuring a transformation ratio value of a feedthrough current transformer provided in the embodiment of the present invention. As shown in fig. 10, the method comprises the steps of:
s101, acquiring a first voltage acquired by a first voltage acquirer and a second voltage acquired by a second voltage acquirer; and a preset number of turns of the feedthrough auxiliary winding.
Exemplary, first Voltage harvester V 11 The collected first voltage may be U 11 Second voltage collector V 22 The second collected voltage may be U 22 . The predetermined number of turns of the feedthrough auxiliary winding may be T.
S102, obtaining a ratio of the first voltage to the second voltage and a product of the ratio and a preset turn number as a transformation ratio value of the feedthrough current transformer.
Illustratively, the first voltage U 11 And a second voltage U 22 Can be P, then
The product of the ratio P and the preset number of turns T is used as the transformation ratio of the feedthrough current transformer, the transformation ratio can be expressed as Q, then Q = PxT, that is to say
The number of turns of the feedthrough primary winding is 1 turn.
The embodiment of the invention provides a method for measuring a transformation ratio value of a straight-through current transformer, which comprises the steps of acquiring a first voltage acquired by a first voltage acquirer and a second voltage acquired by a second voltage acquirer; and the preset number of turns of the straight-through auxiliary winding; and acquiring the ratio of the first voltage to the second voltage and the product of the ratio and the preset turns as the transformation ratio of the feedthrough current transformer. The method can quickly and accurately test the variable ratio of the current transformer, and has high test efficiency.
The above-described embodiments should not be construed as limiting the scope of the invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions may be made in accordance with design requirements and other factors. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A cross-core current transformer transformation ratio value measuring device is characterized in that the cross-core current transformer comprises a cross-core primary winding and a cross-core secondary winding; the measuring device includes:
the punching auxiliary winding with the preset number of turns is arranged on one side of the punching secondary winding; the straight-through primary winding is used for passing current, and the straight-through secondary winding and the straight-through auxiliary winding mutually induce corresponding voltage;
the first voltage collector is used for measuring voltages at two ends of the straight-through secondary winding;
the second voltage collector is used for measuring the voltage at two ends of the punching auxiliary winding;
and the processor is respectively connected with the first voltage collector and the second voltage collector and is used for calculating the transformation ratio of the feedthrough current transformer according to the first voltage collected by the first voltage collector, the second voltage collected by the second voltage collector and the preset turns.
2. The apparatus for measuring transformation ratio of a feedthrough current transformer as claimed in claim 1, further comprising: the overvoltage comparator is respectively connected with the output end of the first voltage collector and the control end of the control switch;
the first end of the control switch is connected with the processor, and the second end of the control switch is connected with the feed-through primary winding;
and when the first voltage acquired by the overvoltage comparator is greater than the reference voltage, controlling the control switch to be switched off.
3. The apparatus for measuring the transformation ratio of a feedthrough current transformer as claimed in claim 1, wherein the control switch is a relay.
4. The apparatus for measuring transformation ratio of a feedthrough current transformer according to claim 2, further comprising: and one end of the sinusoidal signal generator is connected with the processor, and the other end of the sinusoidal signal generator is connected with the first end of the control switch.
5. The apparatus for measuring transformation ratio of a feedthrough current transformer as claimed in claim 4, further comprising: and one end of the current power amplifier is connected with the other end of the sinusoidal signal generator, and the other end of the current power amplifier is connected with the first end of the control switch.
6. The apparatus for measuring transformation ratio of a feedthrough current transformer according to claim 2, further comprising: the display screen is connected with the processor, the overvoltage comparator is further connected with the processor, and the processor is used for controlling the display screen to display the comparison result of the overvoltage comparator.
7. The apparatus for measuring transformation ratio of a feedthrough current transformer according to claim 1, further comprising: the analog-to-digital converter is respectively connected with the processor, the first voltage collector and the second voltage collector; the first voltage and the second voltage are both converted into digital signals and are output to the processor.
8. The apparatus of claim 1, wherein the transformation ratio of the feedthrough current transformer is the second voltage divided by the first voltage and multiplied by the predetermined number of turns.
9. The apparatus according to claim 1, wherein the first voltage collector and the second voltage collector are both voltage meters.
10. A transformation ratio measuring method of a feedthrough current transformer, which is realized based on the transformation ratio measuring device of the feedthrough current transformer as claimed in any one of claims 1 to 9, and comprises the following steps:
acquiring a first voltage acquired by the first voltage acquirer and a second voltage acquired by the second voltage acquirer; and the preset number of turns of the feedthrough auxiliary winding;
and acquiring the ratio of the first voltage to the second voltage and the product of the ratio and the preset turns as the variable ratio of the feedthrough current transformer.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211465016.0A CN115792774A (en) | 2022-11-22 | 2022-11-22 | Variable ratio measuring device and method for straight-through current transformer |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211465016.0A CN115792774A (en) | 2022-11-22 | 2022-11-22 | Variable ratio measuring device and method for straight-through current transformer |
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| CN115792774A true CN115792774A (en) | 2023-03-14 |
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| CN202211465016.0A Pending CN115792774A (en) | 2022-11-22 | 2022-11-22 | Variable ratio measuring device and method for straight-through current transformer |
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