A method for rapid and high-precision calibration of Rogowski coil meters

Abstract

The present invention discloses a method for rapidly and accurately calibrating a Rogowski coil meter. The method is used to calibrate a Rogowski coil meter, and includes step S1: placing the Rogowski coil meter on a transformer calibration station and electrically connecting it, thereby programming the Rogowski coil meter to be calibrated, so that the Rogowski coil meter begins calibration. The method disclosed by the present invention allows rapid calibration of the Rogowski coil meter by modifying the meter calibration algorithm on a conventional transformer calibration station without modifying the calibration station. In actual use, the Rogowski coil meter and the mutual inductance meter can share a single calibration device, thereby resolving the need for large current calibration of the Rogowski coil and the redundancy of equipment use, and improving the accuracy of the Rogowski coil.

Description

Technical Field

[0001] The invention belongs to the technical field of Rogowski coil calibration, and in particular relates to a method for calibrating a Rogowski coil meter quickly and accurately. Background Art

[0002] Existing similar technologies use Rogowski coils for meter calibration, requiring either a dedicated calibration station with a Rogowski coil or the modification of an existing mutual inductance meter. Because conventional Rogowski coils are rated for currents exceeding 500A, the calibration station's requirements are very high; it must be capable of handling a minimum of 500A for current calibration.

[0003] If you modify an existing transformer calibration station, the calibration process is cumbersome and requires reinstallation after production. Besides the demanding calibration conditions, the angular deviation of the Rogowski coil installation significantly affects accuracy, so when using a Rogowski coil for calibration, the accuracy will be far from ideal.

[0004] Therefore, further improvements are made to the above problems. Summary of the Invention

[0005] The main purpose of the present invention is to provide a method for quickly and accurately calibrating a Rogowski coil meter. By modifying the meter calibration algorithm on a conventional mutual inductance calibration station without modifying the calibration station, the Rogowski coil meter can be quickly calibrated. As a result, in actual use, the Rogowski coil meter and the mutual inductance meter can share a single calibration device, thereby resolving the need for high current calibration of the Rogowski coil and the redundancy of the equipment used, and improving the accuracy of the Rogowski coil.

[0006] To achieve the above objectives, the present invention provides a method for quickly and accurately calibrating a Rogowski coil meter, which is used to calibrate a Rogowski coil meter, comprising the following steps:

[0007] Step S1: placing the Rogowski coil meter on a transformer calibration table and making electrical connections, thereby programming the Rogowski coil meter to be calibrated, so that the Rogowski coil meter begins calibration;

[0008] Step S2: The mutual inductor calibration station receives standard meter data including current, voltage, active power, and reactive power, and inputs corresponding parameters into the Rogowski coil meter according to the standard meter data, thereby calibrating the Rogowski coil meter. At this time, the Rogowski coil meter is in a mutual inductance state (in the mutual inductance state, the active and reactive values ​​of the Rogowski coil meter are swapped compared to a normal meter and have negative values).

[0009] Step S3: After the calibration process is completed, the Rogowski coil meter exits the mutual inductance state and enters the normal Rogowski coil state.

[0010] As a further preferred technical solution of the above technical solution, step S2 is specifically implemented as follows:

[0011] Step S2.1: The transformer calibration station calibrates the output voltage and output current of the Rogowski coil meter to obtain the corresponding voltage correction coefficient and current AC correction coefficient;

[0012] Step S2.2: The transformer calibration station calibrates the active power and reactive power of the Rogowski coil meter, thereby obtaining the corresponding active power correction coefficient and reactive power correction coefficient;

[0013] Step S2.3: The Rogowski coil meter saves calibration parameters including the voltage correction factor, the current AC correction factor, the active power correction factor, and the reactive power correction factor.

[0014] As a further preferred technical solution of the above technical solution, in step S2.1:

[0015] After inputting the corresponding parameters into the Rogowski coil meter, the actual output voltage and actual output current are obtained, and the actual output voltage and actual output current are corrected with the standard output voltage and standard output current of the standard table data respectively, thereby obtaining the voltage correction coefficient from the actual output voltage to the standard output voltage and the current correction coefficient from the actual output current to the standard output current.

[0016] As a further preferred technical solution of the above technical solution, in step S2.2:

[0017] After correcting the output voltage and output current of the Rogowski coil meter, the actual active power and actual reactive power of the Rogowski coil meter are obtained. The actual active power and actual reactive power are corrected for the difference with the standard active power and standard reactive power of the standard meter data, thereby obtaining the active power correction factor for converting from actual active power to standard active power and the reactive power correction factor for converting from actual reactive power to standard reactive power (that is, the angle is calculated using the active and reactive power of the Rogowski coil meter and compared with the angle of the standard meter data to calibrate the angle difference).

[0018] As a further preferred technical solution of the above technical solution, in step S2.2:

[0019] The actual active power P and actual reactive power Q of a normal electric meter are expressed as:

[0020]

[0021]

[0022] When the voltage and current angles are 60°, the calibration is performed (connecting a common transformer with a 0.5L power calculation, with an angle difference between the voltage and current for better calibration), and the actual active power P and actual reactive power Q of the normal meter are obtained as follows:

[0023] P=I*U*COS60

[0024] Q = I*U*SIN60;

[0025] When the transformer calibration station is connected to the Rogowski coil meter, the actual active power P and actual reactive power Q are expressed as:

[0026] P=I*U*COS(60+90)=-I*U*SIN60

[0027] Q=I*U*SIN(60+90)=-I*U*COS60;

[0028] Therefore, when calibrating the active power and reactive power of the Rogowski coil meter, the parameters of the active power and reactive power are swapped (that is, the active power of the Rogowski coil meter is the reactive power of the normal meter, and the reactive power of the Rogowski coil meter is the active power of the normal meter), and a negative value is added to make the Rogowski coil meter and the transformer calibration station fully compatible (therefore, when calibrating, you only need to swap the actual output active power and reactive power, add a negative value, and then calibrate with the standard meter data).

[0029] It is worth mentioning that due to the characteristics of the Rogowski coil meter, the Rogowski coil is the differential of current with respect to time. The relationship between differential and integral is the relationship between cos and sin, and the angle difference is 90 degrees.

[0030] As a further preferred technical solution of the above technical solution, in step S2.2:

[0031] It is worth mentioning that, in actual situations, the angles produced by the manufacturers of Rogowski coil meters may be inconsistent across batches, resulting in angles that are not exactly 90 degrees apart. Therefore, you can obtain angle data from the manufacturer by batch or perform self-testing to compensate for this angle to achieve high-precision calibration.

[0032] The actual active power P and actual reactive power Q of a normal electric meter are expressed as:

[0033]

[0034]

[0035] When the voltage and current angles are 60°, the calibration is performed (connecting a common transformer with a 0.5L power calculation, with an angle difference between the voltage and current for better calibration), and the actual active power P and actual reactive power Q of the normal meter are obtained as follows:

[0036] P=I*U*COS60

[0037] Q = I*U*SIN60;

[0038] The actual angle x of the Rogowski coil meter can be obtained from the manufacturer's table or through standard equipment. When the transformer calibration station is connected to the Rogowski coil meter, the actual active power P and actual reactive power Q are expressed as follows:

[0039] P=I*U*COS(60+x)=U*I*cos60*sin(x)-U*I*sin60*con(x)

[0040] Q=I*U*SIN(60+x)=U*I*sin60*cos(x)+U*I*cos60*sin(x).

[0041] As a further preferred technical solution of the above technical solution, in step S3, after the calibration process is completed, aging process and re-inspection process are performed in sequence until, in the last step of the re-inspection process, the Rogowski coil meter exits the mutual inductance state and enters the normal Rogowski coil state for final finished product inspection.

[0042] The beneficial effects of the present invention are:

[0043] 1. The meter can be calibrated faster. Previously, a large current was required for calibration, but now only a small current ratio transformer is needed.

[0044] 2. Better accuracy. Calibration with a high-precision transformer can avoid the accuracy impact caused by the Rogowski coil itself or the installation of the Rogowski coil.

[0045] 3. No need for special calibration table for Rogowski coil, saving cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 The present invention provides a flow chart of a method for rapidly and accurately calibrating a Rogowski coil meter. DETAILED DESCRIPTION

[0047] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are for illustrative purposes only, and those skilled in the art will readily appreciate other obvious variations. The basic principles of the present invention defined in the following description may be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the present invention.

[0048] In the preferred embodiment of the present invention, those skilled in the art should note that the Rogowski coil meter and transformer calibration station involved in the present invention can be regarded as prior art.

[0049] Preferred embodiment.

[0050] The present invention discloses a method for quickly and accurately calibrating a Rogowski coil meter, which is used for calibrating a Rogowski coil meter and comprises the following steps:

[0051] Step S1: placing the Rogowski coil meter on a transformer calibration table and making electrical connections, thereby programming the Rogowski coil meter to be calibrated, so that the Rogowski coil meter begins calibration;

[0052] Step S2: The mutual inductor calibration station receives standard meter data including current, voltage, active power, and reactive power, and inputs corresponding parameters into the Rogowski coil meter according to the standard meter data, thereby calibrating the Rogowski coil meter. At this time, the Rogowski coil meter is in a mutual inductance state (in the mutual inductance state, the active and reactive values ​​of the Rogowski coil meter are swapped compared to a normal meter and have negative values).

[0053] Step S3: After the calibration process is completed, the Rogowski coil meter exits the mutual inductance state and enters the normal Rogowski coil state.

[0054] Specifically, step S2 is implemented as follows:

[0055] Step S2.1: The transformer calibration station calibrates the output voltage and output current of the Rogowski coil meter to obtain the corresponding voltage correction coefficient and current AC correction coefficient;

[0056] Step S2.2: The transformer calibration station calibrates the active power and reactive power of the Rogowski coil meter, thereby obtaining the corresponding active power correction coefficient and reactive power correction coefficient;

[0057] Step S2.3: The Rogowski coil meter saves calibration parameters including the voltage correction factor, the current AC correction factor, the active power correction factor, and the reactive power correction factor.

[0058] More specifically, in step S2.1:

[0059] After inputting the corresponding parameters into the Rogowski coil meter, the actual output voltage and actual output current are obtained, and the actual output voltage and actual output current are corrected with the standard output voltage and standard output current of the standard table data respectively, thereby obtaining the voltage correction coefficient from the actual output voltage to the standard output voltage and the current correction coefficient from the actual output current to the standard output current.

[0060] Furthermore, in step S2.2:

[0061] After correcting the output voltage and output current of the Rogowski coil meter, the actual active power and actual reactive power of the Rogowski coil meter are obtained. The actual active power and actual reactive power are corrected for the difference with the standard active power and standard reactive power of the standard meter data, thereby obtaining the active power correction factor for converting from actual active power to standard active power and the reactive power correction factor for converting from actual reactive power to standard reactive power (that is, the angle is calculated using the active and reactive power of the Rogowski coil meter and compared with the angle of the standard meter data to calibrate the angle difference).

[0062] Furthermore, in step S2.2:

[0063] The actual active power P and actual reactive power Q of a normal electric meter are expressed as:

[0064]

[0065]

[0066] When the voltage and current angles are 60 degrees (in other embodiments, the present invention is not limited to 60 degrees, and other angles are possible, as long as the voltage and current are provided with an angle difference), calibration is performed (connecting a common transformer 0.5L power calculation, and providing an angle difference between the voltage and current for better calibration), thereby obtaining the actual active power P and actual reactive power Q of the normal meter, which are expressed as:

[0067] P=I*U*COS60

[0068] Q = I*U*SIN60;

[0069] When the transformer calibration station is connected to the Rogowski coil meter, the actual active power P and actual reactive power Q are expressed as:

[0070] P=I*U*COS(60+90)=-I*U*SIN60

[0071] Q=I*U*SIN(60+90)=-I*U*COS60;

[0072] Therefore, when calibrating the active power and reactive power of the Rogowski coil meter, the parameters of the active power and reactive power are swapped (that is, the active power of the Rogowski coil meter is the reactive power of the normal meter, and the reactive power of the Rogowski coil meter is the active power of the normal meter), and a negative value is added to make the Rogowski coil meter and the transformer calibration station fully compatible (therefore, when calibrating, you only need to swap the actual output active power and reactive power, add a negative value, and then calibrate with the standard meter data).

[0073] It is worth mentioning that due to the characteristics of the Rogowski coil meter, the Rogowski coil is the differential of current with respect to time. The relationship between differential and integral is the relationship between cos and sin, and the angle difference is 90 degrees.

[0074] Preferably, in step S2.2:

[0075] It is worth mentioning that, in actual situations, the angles produced by the manufacturers of Rogowski coil meters may be inconsistent across batches, resulting in angles that are not exactly 90 degrees apart. Therefore, you can obtain angle data from the manufacturer by batch or perform self-testing to compensate for this angle to achieve high-precision calibration.

[0076] The actual active power P and actual reactive power Q of a normal electric meter are expressed as:

[0077]

[0078]

[0079] When the voltage and current angles are 60°, the calibration is performed (connecting a common transformer with a 0.5L power calculation, with an angle difference between the voltage and current for better calibration), and the actual active power P and actual reactive power Q of the normal meter are obtained as follows:

[0080] P=I*U*COS60

[0081] Q = I*U*SIN60;

[0082] The actual angle x of the Rogowski coil meter can be obtained from the manufacturer's table or through standard equipment. When the transformer calibration station is connected to the Rogowski coil meter, the actual active power P and actual reactive power Q are expressed as follows:

[0083] P=I*U*COS(60+x)=U*I*cos60*sin(x)-U*I*sin60*con(x)

[0084] Q=I*U*SIN(60+x)=U*I*sin60*cos(x)+U*I*cos60*sin(x).

[0085] Preferably, in step S3, after the calibration process is completed, aging process and re-inspection process are performed in sequence until, in the last step of the re-inspection process, the Rogowski coil meter exits the mutual inductance state and enters the normal Rogowski coil state for final finished product inspection.

[0086] Preferably, a current transformer operates on the principle of electromagnetic induction, similar to a transformer. While a transformer converts voltage, a current transformer converts current. The winding connected to the current being measured (N1 turns) is called the primary winding (or primary winding); the winding connected to the measuring instrument (N2 turns) is called the secondary winding (or secondary winding).

[0087] The current ratio of the current transformer primary winding current I1 to the secondary winding current I2 is called the actual current ratio K. The current ratio when the current transformer operates at rated current is called the current transformer rated current ratio, which is represented by Kn.

[0088] Kn=I1n / I2n

[0089] A current transformer (CT) converts a larger primary current into a smaller secondary current using a specific transformation ratio. This is used for protection and measurement purposes. For example, a CT with a transformation ratio of 400 / 5 can convert a current of 400A into 5A.

[0090] A Rogowski coil is a hollow annular coil that comes in two types: flexible and rigid. It can be directly placed on the conductor to measure AC current.

[0091] The theoretical basis for measuring current with a Rogowski coil is Faraday's law of electromagnetic induction and Ampere's law of loops. When the measured current passes through the center of the Rogowski coil along its axis, a correspondingly changing magnetic field with an intensity of H occurs within the volume enclosed by the annular winding. According to Ampere's law of loops, we get:

[0092] ∮H·dl=I(t)

[0093] From B=μH, e(t)=dΦ / dt, Ф=N∫B·dS, e(t)=M·di / dt, we get:

[0094] When its cross section is rectangular, the mutual inductance coefficient M and self-inductance coefficient L are:

[0095] M=μ0Nhln(b / a) / 2π

[0096] L=μ0N^2hln(b / a) / 2π

[0097] In the above formula, H is the magnetic field strength within the coil, B is the magnetic induction strength within the coil, μ is the vacuum permeability, N is the number of turns in the coil, e(t) is the induced voltage across the coil, a and b are the inner and outer diameters of the coil cross section, respectively, and h is the cross-sectional height. This shows that once the coil is in time, M is a constant, and the coil's output voltage is proportional to di / dt.

[0098] The outputs of the secondary sides of a Rogowski coil and a transformer are different signals. A transformer can be understood as a reduction of the current signal, while a Rogowski coil differentiates the current with respect to time. They must be used with an integrator to function properly, as shown in the figure above. Our Rogowski coil meters are already equipped with an integrator. The relationship between differentiation and integration is similar to that between cosine and sin, with a 90-degree difference in angle. Therefore, under existing technology, Rogowski coil meters and transformer meters cannot be used interchangeably.

[0099] The technical solution of the present invention can make the mutual inductor calibration station compatible with Rogowski coil meters and mutual inductor meters. The present invention mainly uses the translation of the current waveform to achieve fast and high-precision calibration of the Rogowski coil, and there is no need to change the original calibration mode, which saves the use of the Rogowski coil, speeds up the calibration and re-inspection, and improves the accuracy. From the beginning of the program burning, the meter has been in the calibration state, that is, the active and reactive power are reversed until the re-inspection is completed. This is to ensure that the calibration software can correctly compare the multi-function parameters of the meter during calibration and re-inspection. After the re-inspection is completed, the meter will exit the calibration state and enter the normal state for delivery to the customer.

[0100] It is worth mentioning that the technical features such as the Rogowski coil meter and the transformer calibration station involved in the patent application of this invention should be regarded as prior art. The specific structure, working principle and possible control method and spatial layout method of these technical features can be selected by conventional options in the field and should not be regarded as the inventive point of this patent. This patent will not be further elaborated.

[0101] For those skilled in the art, it is still possible to modify the technical solutions described in the aforementioned embodiments, or to make equivalent replacements for some of the technical features therein. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for quickly and accurately calibrating a Rogowski coil meter, which is used to calibrate a Rogowski coil meter, characterized in that: The following steps are involved: Step S1: placing the Rogowski coil meter on a transformer calibration table and making electrical connections, thereby programming the Rogowski coil meter to be calibrated, so that the Rogowski coil meter begins calibration; Step S2: The mutual inductor calibration station receives standard meter data including current, voltage, active power and reactive power, and inputs corresponding parameters into the Rogowski coil meter according to the standard meter data, thereby calibrating the Rogowski coil meter and placing the Rogowski coil meter in a mutual inductance state. Step S3: After the calibration process is completed, the Rogowski coil meter exits the mutual inductance state and enters the normal Rogowski coil state; Step S2 is specifically implemented as follows: Step S2.1: The transformer calibration station calibrates the output voltage and output current of the Rogowski coil meter to obtain the corresponding voltage correction coefficient and current AC correction coefficient; Step S2.2: The transformer calibration station calibrates the active power and reactive power of the Rogowski coil meter, thereby obtaining the corresponding active power correction coefficient and reactive power correction coefficient; Step S2.3: The Rogowski coil meter saves calibration parameters including voltage correction coefficient, current AC correction coefficient, active power correction coefficient, and reactive power correction coefficient; In step S2.1: After inputting corresponding parameters into the Rogowski coil meter, the actual output voltage and actual output current are obtained, and the actual output voltage and actual output current are corrected with the standard output voltage and standard output current of the standard meter data respectively, thereby obtaining the voltage correction coefficient from the actual output voltage to the standard output voltage and the current correction coefficient from the actual output current to the standard output current; In step S2.2: After correcting the output voltage and output current of the Rogowski coil meter, the actual active power and actual reactive power of the Rogowski coil meter are obtained, and the actual active power and actual reactive power are corrected by comparing the difference with the standard active power and standard reactive power of the standard meter data, thereby obtaining an active power correction factor for converting the actual active power to the standard active power and a reactive power correction factor for converting the actual reactive power to the standard reactive power; In step S2.2: The actual active power P and actual reactive power Q of a normal electric meter are expressed as: ； When the voltage and current angles are 60°, the actual active power P and actual reactive power Q of the normal meter are obtained and expressed as: ； When the transformer calibration station is connected to the Rogowski coil meter, the actual active power P and actual reactive power Q are expressed as: ； Therefore, when calibrating the active power and reactive power of the Rogowski coil meter, the parameters of active power and reactive power are swapped and negative values ​​are added to make the Rogowski coil meter fully compatible with the transformer calibration station. In step S2.2: The actual active power P and actual reactive power Q of a normal electric meter are expressed as: ； When the voltage and current angles are 60°, the actual active power P and actual reactive power Q of the normal meter are obtained and expressed as: ； The actual angle x of the Rogowski coil meter can be obtained from the manufacturer's table or through standard equipment. When the transformer calibration station is connected to the Rogowski coil meter, the actual active power P and actual reactive power Q are expressed as follows: 。 2. The method for rapid and high-precision calibration of a Rogowski coil meter according to claim 1, characterized in that: In step S3, after the calibration process is completed, aging process and re-inspection process are performed in sequence until, in the last step of the re-inspection process, the Rogowski coil meter exits the mutual inductance state and enters the normal Rogowski coil state for the final finished product inspection.

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