High-accuracy current ratio standard and implementation method therefor

Abstract

The present invention relates to a high-accuracy current ratio standard and an implementation method therefor. The standard comprises a main current transformer, and a ratio error compensation module and a phase angle error compensation module, which are connected thereto. The ratio error compensation module is formed by connecting a compensating current transformer, a first standard resistor and a first precision trimmer resistor into a four-terminal network. The phase angle error compensation module is formed by connecting an air-core mutual inductance coil, a second standard resistor and a second precision trimmer resistor into a four-terminal network. Two terminals on an input side of the ratio error compensation module are respectively connected to a terminal on a primary side of the main current transformer and a terminal on an input side of the phase angle error compensation module, the other terminal on the primary side of the main current transformer and the other terminal on the input side of the phase angle error compensation module form input ends of the current ratio standard, and two terminals on an output side of the ratio error compensation module and two terminals on an output side of the phase angle error compensation module are all connected in parallel between terminals on a secondary side of the main current transformer, in order to form output ends of the current ratio standard.

Description

High-accuracy current ratio standard and implementation method

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application No. 202411327645.6, filed on September 23, 2024, and entitled "High-accuracy current ratio standard and implementation method", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of electric power measurement standards. Specifically, it relates to a high-accuracy current ratio standard and implementation method. BACKGROUND

[0004] Current transformers are generally used to transform large currents on the primary side of the power grid into small currents on the secondary side. Current transformers can be classified into two categories according to their use: (1) measurement current transformers, which transform high-voltage large currents on the primary side into low-voltage small currents on the secondary side under stable operating conditions of the power system, thereby converting high-power measurement currents into small-power measurement currents, and achieving online monitoring of currents, data storage, and electric energy measurement; (2) protection current transformers, which, when a fault occurs in the power grid, control the system to start the corresponding relay protection device, remove the faulty electromagnetic device in the power system, and put the standby electromagnetic device into operation, thereby ensuring the safe and stable operation of the power system.

[0005] Currently, the commonly used current transformers are mainly electronic current transformers and electromagnetic current transformers. The latter has the advantages of simple principle and easy use, and is more widely used. For measurement current transformers, their accuracy is related to the accuracy of electric energy measurement. The accuracy of current transformers is generally determined through verification and calibration tests, which usually involves comparing the tested current transformer with a current ratio standard. The existing JJG 313-1010 regulation specifies how to verify measurement current transformers, and the existing JJF 1701.1-1018 and JJF 1701.4-1019 technical specifications specify the type evaluation outline for standard current transformers and current transformers for measurement.

[0006] A current ratio standard needs to meet two conditions of stability and traceability. Although the current electromagnetic standard transformer has been widely used as a standard in the field of electric power measurement, there are still defects. In particular, the accuracy of the electromagnetic current transformer is easily affected by environmental temperature, humidity, core space position and other conditions; on the other hand, the working conditions of the electromagnetic current transformer are very complex, for example, the proximity effect caused by the electrical equipment around the transformer and its proximity will cause the error of the transformer to become larger, thereby reducing its accuracy. In addition, with the development of new power systems, the traceability demand of wideband current transformer is becoming more and more urgent.

[0007] Therefore, it is desirable in the art to have a method capable of conveniently realizing a high-accuracy current ratio standard, so that in the case that the error of the current ratio standard exceeds the limit value, the error of the current ratio standard can be compensated by convenient and effective means, so as to reach and maintain high accuracy. SUMMARY

[0008] According to a first aspect of the present application, a high-accuracy current ratio standard is provided, which includes a main current transformer with an accuracy of at least 1 level, a ratio difference compensation module and an angle difference compensation module coupled with the main current transformer, wherein the ratio difference compensation module is formed into a four-terminal network by a compensation current transformer, a first standard resistor and a first precision adjustable resistor, the angle difference compensation module is formed into a four-terminal network by a hollow mutual inductor, a second standard resistor and a second precision adjustable resistor, two terminals of the input side of the ratio difference compensation module are respectively coupled with a terminal of the primary side of the main current transformer and a terminal of the input side of the angle difference compensation module, the other terminal of the primary side of the main current transformer and the other terminal of the input side of the angle difference compensation module form an input end of the current ratio standard, and the two terminals of the output side of the ratio difference compensation module and the two terminals of the output side of the angle difference compensation module are both connected in parallel between the terminals of the secondary side of the main current transformer to form an output end of the current ratio standard, wherein the ratio difference compensation module is configured to compensate the ratio difference of the current ratio standard by adjusting the first precision adjustable resistor based on a predetermined ratio difference compensation amount, so that the ratio difference of the current ratio standard is within the ratio difference limit value range required by high accuracy, and the angle difference compensation module is configured to compensate the angle difference of the current ratio standard by adjusting the second precision adjustable resistor based on a predetermined angle difference compensation amount, so that the angle difference of the current ratio standard is within the angle difference limit value range required by high accuracy.

[0009] According to the preferred embodiment of the first aspect of the present application, the transformation ratio of the compensation current transformer of the ratio error compensation module, the resistance value of the first standard resistance, and the resistance value and adjustment range of the first precision adjustable resistance are configured according to the ratio error, the rated transformation ratio, and the rated secondary load of the main current transformer under the rated operating condition, and the number of turns and the coil size of the air-core transformer coil of the angle error compensation module, the resistance value of the second standard resistance, and the resistance value and adjustment range of the second precision adjustable resistance are configured according to the angle error, the rated transformation ratio, the rated secondary load, and the AC frequency of the rated operating condition of the main current transformer.

[0010] According to the second aspect of the present application, another high-accuracy current ratio standardizer is provided, which comprises a main current transformer and a secondary current transformer connected in series at the primary side and having an accuracy of at least 1 class, and a ratio error compensation module and an angle error compensation module coupled with the main current transformer and the secondary current transformer, wherein the ratio error compensation module forms a four-terminal network coupled with a compensation current transformer, a first standard resistance, and a first precision adjustable resistance, the angle error compensation module forms a four-terminal network coupled with an air-core transformer coil, a second standard resistance, and a second precision adjustable resistance, the terminals of the primary side of the main current transformer and the secondary current transformer which are not connected in series form the input terminals of the current ratio standardizer, the terminals of the input side of the ratio error compensation module and the terminals of the input side of the angle error compensation module are connected in series and then connected in parallel between the terminals of the secondary side of the secondary current transformer, and the two terminals of the output side of the ratio error compensation module and the two terminals of the output side of the angle error compensation module are both connected in parallel between the terminals of the secondary side of the main current transformer, forming the output terminals of the current ratio standardizer, wherein the ratio error compensation module is configured to compensate the ratio error of the current ratio standardizer by adjusting the first precision adjustable resistance to achieve a predetermined ratio error compensation amount based on a predetermined ratio error compensation amount, so that the ratio error of the current ratio standardizer is within the ratio error limit range required by the high accuracy, and the angle error compensation module is configured to compensate the angle error of the current ratio standardizer by adjusting the second precision adjustable resistance to achieve a predetermined angle error compensation amount based on a predetermined angle error compensation amount, so that the angle error of the current ratio standardizer is within the angle error limit range required by the high accuracy.

[0011] According to the preferred embodiment of the second aspect of the present application, the transformation ratio of the compensation current transformer of the ratio error compensation module, the resistance value of the first standard resistance, and the resistance value and adjustment range of the first precision adjustable resistance are configured according to the ratio error, the rated transformation ratio, and the rated secondary load of the main current transformer under the rated operating condition, and the number of turns and the coil size of the air-core transformer coil of the angle error compensation module, the resistance value of the second standard resistance, and the resistance value and adjustment range of the second precision adjustable resistance are configured according to the angle error, the rated transformation ratio, the rated secondary load, and the AC frequency of the rated operating condition of the main current transformer under the rated operating condition, and the current transformation ratio of the secondary current transformer.

[0012] According to a third aspect of the present application, a method for implementing a high-accuracy current ratio standardizer is provided, which comprises the following steps: S1, obtaining an electromagnetic current transformer with an accuracy of at least 1 level and measuring the ratio error and the angle error of the electromagnetic current transformer under a rated operating condition, wherein the electromagnetic current transformer is configured as a single primary current transformer or a primary current transformer and a secondary current transformer connected in series at the primary side; S2, calculating the ratio error compensation amount and the angle error compensation amount required to be applied to the primary current transformer for implementing the high-accuracy current ratio standardizer based on the ratio error and the angle error of the current transformer; S3, configuring the parameters of a ratio error compensation module according to the rated transformation ratio, the rated secondary load and the ratio error compensation amount of the primary current transformer, and configuring the parameters of an angle error compensation module according to the rated transformation ratio, the rated secondary load, the alternating current frequency of the rated operating condition and the angle error compensation amount of the primary current transformer, wherein the ratio error compensation module is formed by connecting a compensation current transformer, a first standard resistor and a first precision adjustable resistor to form a four-terminal network, and the angle error compensation module is formed by connecting a hollow mutual inductor, a second standard resistor and a second precision adjustable resistor to form a four-terminal network, the parameters of the ratio error compensation module include the transformation ratio of the compensation current transformer, the resistance value of the first standard resistor and the resistance value and adjustment range of the first precision adjustable resistor, and the parameters of the angle error compensation module include the number of turns and the size of the coil of the hollow mutual inductor, the resistance value of the second standard resistor and the resistance value and adjustment range of the second precision adjustable resistor; S4, connecting the ratio error compensation module and the angle error compensation module to the current transformer to form the current ratio standardizer; S5, measuring the ratio error and the angle error of the current ratio standardizer under the rated operating condition and checking the levels of the ratio error and the angle error of the current ratio standardizer; S6, determining whether the ratio error or the angle error of the current ratio standardizer exceeds the error limit value range required by the high accuracy, and if not, the checking is qualified and goes to step S8, otherwise, it continues to step S7; S7, if the ratio error of the current ratio standardizer exceeds the ratio error limit value range required by the high accuracy, the ratio error of the current ratio standardizer is compensated by adjusting the resistance value of the first precision adjustable resistor, and if the angle error of the current ratio standardizer exceeds the angle error limit value range required by the high accuracy, the angle error of the current ratio standardizer is compensated by adjusting the resistance value of the second precision adjustable resistor, and then goes to step S5; and S8, completing the implementation of the high-accuracy current ratio standardizer.

[0013] According to the preferred embodiment of the third aspect of the application, in the case that the electromagnetic current transformer is configured as a single main current transformer, coupling the ratio difference compensation module and the angle difference compensation module to the current transformer comprises: coupling two terminals of the input side of the compensation current transformer to a terminal of the primary side of the main current transformer and one terminal of the input side of the angle difference compensation module respectively, so that the other terminal of the primary side of the main current transformer and the other terminal of the input side of the angle difference compensation module form an input end of the current ratio standardizer, and coupling both terminals of the output side of the ratio difference compensation module and both terminals of the output side of the angle difference compensation module to the terminals of the secondary side of the main current transformer in parallel to form an output end of the current ratio standardizer, so that the parameter configuration of the ratio difference compensation module satisfies the following formula:

[0014] Rx=R1*K0 / (K1*ΔIf)-R1-Rb

[0015] wherein Rx represents the resistance value of the first precision adjustable resistor, R1 represents the resistance value of the first standard resistor, K0 represents the rated transformation ratio of the main current transformer, K1 represents the current transformation ratio of the compensation current transformer, ΔIf represents the ratio difference compensation amount, and Rb represents the impedance value of the rated secondary load of the main current transformer;

[0016] The parameter configuration of the angle difference compensation module satisfies the following formula:

[0017] RY=U40*K0 / (ΔIδ*I1)-R2-Rb

[0018] wherein RY represents the resistance value of the second precision adjustable resistor, K0 represents the rated transformation ratio of the main current transformer, ΔIδ represents the angle difference compensation amount, I1 represents the rated primary current value of the main current transformer, R2 represents the resistance value of the second standard resistor, Rb represents the impedance value of the rated secondary load of the main current transformer, and U40 represents the induced voltage value generated at the secondary side of the air-core mutual inductor;

[0019] The induced voltage at the secondary side of the air-core mutual inductor is derived from the following formula:

[0020]

[0021] wherein U40 represents the induced voltage value generated at the secondary side of the air-core mutual inductor, μ0 represents the magnetic permeability of air, π is the circular constant, N1 and N2 respectively represent the number of turns of the primary side and the secondary side of the air-core mutual inductor, L represents the axial length of the primary side coil of the air-core mutual inductor, D represents the diameter of the circular cross section surrounded by the air-core mutual inductor, f represents the AC frequency of the rated working condition, and I1 represents the rated primary current value of the main current transformer.

[0022] According to the preferred embodiment of the third aspect of the application, in the case that the electromagnetic current transformer is configured as a primary side series connection of a main current transformer and a secondary current transformer, the coupling of the ratio difference compensation module and the angle difference compensation module to the current transformer comprises: connecting the terminals of the input side of the ratio difference compensation module and the terminals of the input side of the angle difference compensation module in series and connecting them between the terminals of the secondary side of the secondary current transformer, connecting the two terminals of the output side of the ratio difference compensation module and the two terminals of the output side of the angle difference compensation module in parallel and connecting them between the terminals of the secondary side of the main current transformer to form the output end of the current ratio standardizer, and the terminals of the primary side of the main current transformer and the secondary current transformer which are not connected in series form the input end of the current ratio standardizer. Thus, the parameter configuration of the ratio difference compensation module satisfies the following formula:

[0023] Rx=R1*K0 / (K1*K2*ΔIf)-R1-Rb,

[0024] wherein Rx represents the resistance value of the first precision adjustable resistor, R1 represents the resistance value of the first standard resistor, K0 represents the rated transformation ratio of the main current transformer, K1 represents the current transformation ratio of the compensation current transformer, K2 represents the current transformation ratio of the secondary current transformer, ΔIf represents the ratio difference compensation amount, and Rb represents the impedance value of the rated secondary load of the main current transformer;

[0025] The parameter configuration of the angle difference compensation module satisfies the following formula:

[0026] RY=U40*K0 / (ΔIδ*I1)-R2-Rb

[0027] wherein RY represents the resistance value of the second precision adjustable resistor, K0 represents the rated transformation ratio of the main current transformer, ΔIδ represents the angle difference compensation amount, I1 represents the rated primary current value of the main current transformer, R2 represents the resistance value of the second standard resistor, Rb represents the impedance value of the rated secondary load of the main current transformer, and U40 represents the induced voltage value generated at the secondary side of the air-core mutual inductor;

[0028] The induced voltage generated at the secondary side of the air-core mutual inductor is obtained by the following formula:

[0029]

[0030] wherein U40 represents the induced voltage value generated at the secondary side of the air-core mutual inductor, μ0 represents the magnetic permeability of air, π is the circular constant, N1 and N2 respectively represent the number of turns of the primary side and the secondary side of the air-core mutual inductor, L represents the axial length of the primary side coil of the air-core mutual inductor, D represents the diameter of the circular cross section surrounded by the air-core mutual inductor, f represents the AC frequency of the rated working condition, I1 represents the rated primary current value of the main current transformer, and K2 represents the current transformation ratio of the secondary current transformer.

[0031] According to the preferred embodiments of the foregoing aspects of the present application, the first precision adjustable resistor and the second precision adjustable resistor are both multi-turn adjustable resistors, and the maximum resistance values of the first precision adjustable resistor and the second precision adjustable resistor are both configured to be at least 10000 times the impedance of the rated secondary load of the primary current transformer.

[0032] According to the preferred embodiments of the foregoing aspects of the present application, the current transformer used by the ratio and phase difference compensation module is a current transformer with an accuracy of 1st class or higher.

[0033] The high-accuracy current ratio standardizer and the implementation method provided by the present application have the following advantages: (1) a high-accuracy current ratio standardizer can be conveniently realized by using a conventional accuracy electromagnetic current transformer; (2) in the case where the error of the current ratio standardizer exceeds the rated limit range, the ratio and phase difference of the current ratio standardizer can be respectively adjusted by the continuously adjustable error compensation, so that the current ratio standardizer can conveniently achieve high accuracy; (3) the ratio difference compensation module of the current ratio standardizer can compensate for the ratio difference current component in phase with the secondary current vector, the phase difference compensation module of the current ratio standardizer can compensate for the phase difference current component orthogonal to the secondary current vector, the accuracy of the phase difference compensation is higher, and the high-frequency response performance is better. BRIEF DESCRIPTION OF DRAWINGS

[0034] One or more embodiments of the present application are exemplarily illustrated by corresponding drawings, which do not constitute a limitation on the embodiments, and elements with the same reference numerals in the drawings represent similar elements, unless otherwise stated, and the drawings do not constitute a proportional limit.

[0035] FIG. 1 shows a working principle diagram of a current transformer.

[0036] FIG. 2 shows a circuit principle diagram of a current ratio standardizer according to a first embodiment of the present application.

[0037] FIG. 3 shows a circuit principle diagram of a current ratio standardizer according to a second embodiment of the present application.

[0038] FIG. 4 shows a circuit principle diagram of a current ratio standardizer according to a third embodiment of the present application.

[0039] FIG. 5 shows a circuit principle diagram of a current ratio standardizer according to the first embodiment of the present application coupled with an alternating current source and a secondary load for error compensation.

[0040] FIG. 6 shows a flowchart of an implementation method of a current ratio standardizer according to an embodiment of the present application.

[0041] FIG. 7 shows an error compensation vector diagram of a current ratio standardizer according to an embodiment of the present application.

[0042] Reference signs

[0043] 1 - electromagnetic current transformer, 2 - current ratio standard, 10 - secondary load of current transformer, 3 - ratio error compensation module, 30 - compensation current transformer, 32 - first standard resistor, 34 - first precision adjustable resistor, 4 - phase error compensation module, 40 - air-core mutual inductor, 42 - second standard resistor, 44 - second precision adjustable resistor, CT1 - main current transformer, CT2 - auxiliary current transformer, P1, P2 - primary side terminals of main current transformer, S1, S2 - secondary side terminals of main current transformer, XP1, XP2 - input side terminals of ratio error compensation module, XS1, XS2 - output side terminals of ratio error compensation module, YP1, YP2 - input side terminals of phase error compensation module, YS1, YS2 - output side terminals of phase error compensation module, A, B - input terminals of current ratio standard, a, b - output terminals of current ratio standard, I1 - input current of current ratio standard, IX - ratio error compensation current, IY - phase error compensation current, I20 - secondary current of main current transformer, I21 - current after ratio error compensation of secondary current of main current transformer, I22 - current after ratio error compensation and phase error compensation of secondary current of main current transformer, I30 - current flowing through input side of ratio error compensation module, I40 - current flowing through input side of phase error compensation module, U40 - induced voltage generated at secondary side of air-core mutual inductor, R1 - resistance value of first standard resistor, R2 - resistance value of second standard resistor, RX - resistance value of first precision adjustable resistor, RY - resistance value of second precision adjustable resistor, Rb - impedance value of secondary load, AC - alternating current source. Embodiment of the present application

[0044] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0045] It should be noted that the various features of the embodiments of the present application can be combined with each other if there is no conflict, and all are within the protection scope of the present application. In addition, although the functional modules are divided in the schematic diagram, and the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order from the order in the schematic diagram or the flowchart.

[0046] Unless otherwise defined, all technical and scientific terms used in the present disclosure have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. All publications, patent applications, patents, and other references mentioned in this specification are herein incorporated by reference in their entirety for the purpose of describing and disclosing, for example, the methodologies described in such publications, which might provide useful background to the present application.

[0047] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings of the embodiments of the present application, so that the purposes and advantages of the present application are more apparent. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments.

[0048] Fig. 1 shows a working principle diagram of the electromagnetic current transformer 1. When the alternating current source AC is coupled between the primary side terminals P1, P2 of the electromagnetic current transformer 1, the primary current output by the alternating current source AC flows through the primary winding of the electromagnetic current transformer 1, and according to the principle of electromagnetic induction, an electromotive force will be induced in the secondary winding of the electromagnetic current transformer 1. When the secondary side terminals S1, S2 are connected to the secondary load 10, a secondary current flowing through the secondary load 10 will be generated.

[0049] Fig. 2 shows a circuit principle diagram of the current ratio standardizer 2 according to the first embodiment of the present application. The current ratio standardizer 2 comprises a single electromagnetic current transformer 1 (also referred to as a main current transformer CT1) with an accuracy of at least 1 class, a ratio difference compensation module 3 and an angle difference compensation module 4 coupled with the electromagnetic current transformer 1. Preferably, the accuracy of the electromagnetic current transformer 1 is at least 0.1 class.

[0050] Further referring to Fig. 2, the output terminals a, b of the current ratio standard 2 are formed by the secondary side terminals S1, S2 of the main current transformer CT1. The ratio error compensation module 3 of the current ratio standard 2 is formed as a four-terminal network by the compensation current transformer 30, the first standard resistor 32 and the first precision adjustable resistor 34. In particular, the input side terminals XP1, XP2 of the ratio error compensation module 3 are formed by the primary side terminals of the compensation current transformer 30, the first standard resistor 32 is connected between the secondary side terminals of the compensation current transformer 30, and the first precision adjustable resistor 34 is connected in series with the first standard resistor 32, and the non-connected terminals of both form the output side terminals YS1, YS2 of the ratio error compensation module 3. The phase error compensation module 4 of the current ratio standard 2 is formed as a four-terminal network by the air-core transformer coil 40, the second standard resistor 42 and the second precision adjustable resistor 44. In particular, the input side terminals YP1, YP2 of the phase error compensation module 4 are formed by the leads of the primary side coil of the air-core transformer coil 40, the second standard resistor 42 and the second precision adjustable resistor 44 are connected in series with the secondary side coil of the air-core transformer coil 40, and the non-connected terminals of the secondary side coil of the air-core transformer coil 40, the second standard resistor 42 or the second precision adjustable resistor 44 form the output side terminals YS1, YS2 of the phase error compensation module 4.

[0051] In the embodiment shown in Fig. 2, the input side terminals XP1, XP2 of the ratio error compensation module 3 are connected to the terminal P2 of the primary side of the main current transformer CT1 and to the input side terminal YP1 of the phase error compensation module 4, respectively, the other terminal P1 of the primary side of the main current transformer CT1 and the other input side terminal YP2 of the phase error compensation module 4 form the input terminals A, B of the current ratio standard 2, and the output side terminals YS1, YS2 of the ratio error compensation module 3 and the output side terminals YP1, YP2 of the phase error compensation module 4 are all connected between the terminals S1, S2 of the secondary side of the main current transformer CT1, forming the output terminals a, b of the current ratio standard 2.

[0052] In the embodiment shown in Fig. 2, the current transformation ratio of the compensation current transformer 30 of the ratio error compensation module 3, the resistance value of the first standard resistor 32, and the resistance value and adjustment range of the first precision adjustable resistor 34 can be configured according to the ratio error, the rated transformation ratio, and the rated secondary load of the main current transformer CT1 under the rated operating condition. The number of turns and the coil size of the air-core transformer coil 40 of the phase error compensation module 4, the resistance value of the second standard resistor 42, and the resistance value and adjustment range of the second precision adjustable resistor 44 can be configured according to the phase error, the rated transformation ratio, the rated secondary load, and the AC frequency of the rated operating condition of the main current transformer CT1. The ratio error compensation module 3 is configured to compensate the ratio error of the main current transformer CT1 by adjusting the resistance value of the first precision adjustable resistor 34 to achieve a predetermined ratio error compensation amount based on the predetermined ratio error of the main current transformer CT1, so that the ratio error of the current ratio standardizer 2 is within the ratio error limit value range of the high accuracy requirement. The phase error compensation module 4 is configured to compensate the phase error of the main current transformer CT1 by adjusting the resistance value of the second precision adjustable resistor 44 to achieve a predetermined phase error compensation amount based on the predetermined phase error of the main current transformer CT1, so that the phase error of the current ratio standardizer 2 is within the phase error limit value range of the high accuracy requirement.

[0053] Fig. 3 shows a circuit schematic diagram of a current ratio standardizer 2 according to a second embodiment of the present application. The current ratio standardizer 2 comprises two electromagnetic current transformers 1 (identified as the main current transformer CT1 and the auxiliary current transformer CT2 in Fig. 3) connected in series at the primary side and having an accuracy of at least 1 class, and a ratio error compensation module 3 and a phase error compensation module 4 coupled to the main current transformer CT1 and the auxiliary current transformer CT2. Preferably, the accuracy of the main current transformer CT1 and the auxiliary current transformer CT2 is at least 0.1 class.

[0054] With further reference to Fig. 3, the output terminals a, b of the current ratio standardizer 2 are formed by the secondary side terminals S1, S2 of the main current transformer CT1. The four-terminal network configuration of the ratio error compensation module 3 and the phase error compensation module 4 is similar to that described in the first embodiment described above, which will not be repeated here. In the embodiment shown in Fig. 3, the input side terminals XP1, XP2 of the ratio error compensation module 3 are connected in series with the input side terminals of the phase error compensation module 4 and are connected between the terminals of the secondary side of the auxiliary current transformer CT2, the output side terminals YS1, YS2 of the ratio error compensation module 3 and the output side terminals YP1, YP2 of the phase error compensation module 4 are all connected in parallel between the terminals S1, S2 of the secondary side of the main current transformer CT1, forming the output terminals a, b of the current ratio standardizer 2, and the terminals of the primary side of the main current transformer CT1 and the auxiliary current transformer CT2 which are not connected in series form the input terminals A, B of the current ratio standardizer 2.

[0055] In the embodiment shown in Fig. 3, the current transformation ratio of the compensation current transformer 30, the resistance value of the first standard resistor 32, and the resistance value and adjustment range of the first precision adjustable resistor 34 of the ratio error compensation module 3 can be configured according to the ratio error, the rated transformation ratio, the rated secondary load of the primary current transformer CT1 under the rated operating condition, and the current transformation ratio of the secondary current transformer CT2. The number of turns and the coil size of the air-core transformer coil 40 of the phase error compensation module 4, the resistance value of the second standard resistor 42, and the resistance value and adjustment range of the second precision adjustable resistor 44 can be configured according to the phase error, the rated transformation ratio, the rated secondary load, the AC frequency of the rated operating condition of the primary current transformer CT1, and the current transformation ratio of the secondary current transformer CT2. The ratio error compensation module 3 is configured to compensate the ratio error of the primary current transformer CT1 by adjusting the resistance value of the first precision adjustable resistor 34 to achieve a predetermined ratio error compensation amount based on the predetermined ratio error of the primary current transformer CT1, so that the ratio error of the current proportioning standard device 2 is within the ratio error limit value range of high accuracy requirement. The phase error compensation module 4 is configured to compensate the phase error of the primary current transformer CT1 by adjusting the resistance value of the second precision adjustable resistor 44 to achieve a predetermined phase error compensation amount based on the predetermined phase error of the primary current transformer CT1, so that the phase error of the current proportioning standard device 2 is within the phase error limit value range of high accuracy requirement.

[0056] Fig. 4 shows a circuit schematic diagram of a current proportioning standard device 2 according to a third embodiment of the present application. The current proportioning standard device 2 comprises a single electromagnetic current transformer 1 with an accuracy of at least 1 class, a ratio error compensation module 3 and a phase error compensation module 4 coupled with the electromagnetic current transformer 1. The four-terminal network configuration of the ratio error compensation module 3 and the phase error compensation module 4 in the embodiment shown in Fig. 4 is also similar to that in the first embodiment described above, and thus will not be described again. Different from the first embodiment described above, the input side terminals XP1, XP2 of the ratio error compensation module 3 and the input side terminals of the phase error compensation module 4 are connected in series and connected between the secondary side terminals of the electromagnetic current transformer 1 in the embodiment shown in Fig. 4, while the input terminals A, B and the output terminals a, b of the current proportioning standard device 2 are formed by the primary side terminals P1, P2 and the secondary side terminals S1, S2 of the electromagnetic current transformer 1. In the embodiment shown in Fig. 4, since the equivalent resistance formed by the coupling of the ratio error compensation module 3 and the phase error compensation module 4 is in parallel relationship with respect to the secondary load of the electromagnetic current transformer 1, the shunt effect of the impedance of the equivalent resistance on the secondary current of the electromagnetic current transformer 1 cannot be ignored, and thus the embodiment is only applicable to the case where the electromagnetic current transformer 1 is loaded with a fixed secondary load.

[0057] In practice, the ratio error and the phase error of the electromagnetic current transformer 1 and the current ratio standard 2 can be obtained by the measurement method described in the existing JJG 313-1010 regulation, so as to obtain the corresponding ratio error compensation and the phase error compensation. Alternatively, the ratio error compensation and the phase error compensation can also be obtained by other measurement methods known to those skilled in the art.

[0058] The present application is based on the principle of item-by-item approximation, and the ratio error compensation module 3 and the phase error compensation module 4 are respectively used to implement item-by-item approximation compensation of the ratio error compensation and the phase error compensation of the main current transformer CT1. The significant advantage is that even if the current ratio standard 2 has error drift due to changes in circuit element performance or environmental changes, the ratio error and the phase error after the drift can be conveniently compensated by the ratio error compensation module 3 and the phase error compensation module 4, and the compensation process of the ratio error and the phase error is continuous, linear and controllable, thereby ensuring that the current ratio standard 2 remains at high accuracy after error compensation.

[0059] Referring to FIG. 5, a circuit principle diagram of the current ratio standard 2 coupled with the alternating current source AC and the secondary load 10 for error compensation according to the first embodiment of the present application is shown. In particular, the alternating current source AC can output an alternating current signal with an effective value of the rated primary current of the main current transformer CT1 and the current of each corresponding rated measurement point. Specifically, in the embodiment shown in FIG. 5, the main function of the compensation current transformer 30 of the ratio error compensation module 3 is to obtain a current component in phase with the secondary current vector of the main current transformer CT1, thereby realizing compensation of the ratio error component in phase with the secondary current of the main current transformer CT1; the main function of the air-core mutual inductor coil 40 of the phase error compensation module 4 is to obtain a current component orthogonal in phase to the secondary current vector, thereby realizing compensation of the phase error component orthogonal in phase to the secondary current of the main current transformer CT1. The basic principle of the present application for obtaining the orthogonal current component is based on Ampere's law and the law of electromagnetic induction. In particular, after the alternating current flows through the primary side coil of the air-core mutual inductor coil 40, the phase of the induced electromotive force generated by the secondary side coil is shifted by 90° compared to the phase of the alternating current. Since the secondary current of the main current transformer CT1 is substantially in phase with the alternating current flowing through the primary side coil of the air-core mutual inductor coil 40, the current flowing through the secondary side coil of the air-core mutual inductor coil 40 can be obtained by extracting the current flowing through the secondary side coil of the air-core mutual inductor coil 40 through the resistance coupled with the air-core mutual inductor coil 40, thereby obtaining the phase error compensation current vector substantially orthogonal in phase to the secondary current of the main current transformer CT1.

[0060] In particular, the ratio error compensation module 3 shown in the dashed box of FIG. 5 comprises a compensation current transformer 30, a first standard resistor 32 connected in parallel with the secondary side of the compensation current transformer 30, and a first precision adjustable resistor 34 connected with the first standard resistor 32. According to the ratio error of the main current transformer CT1 under the rated operating condition, the rated transformation ratio, and the rated secondary load, the parameters of the ratio error compensation module 3 are configured, provided that the series branch of the first precision adjustable resistor 34 and the secondary load of the main current transformer CT1 shunts the ratio error compensation current corresponding to the predetermined ratio error compensation amount of the main current transformer CT1 from the secondary side of the compensation current transformer 30, the parameters of the ratio error compensation module 3 need to be configured to satisfy the following formula:

[0061] I30 / K1*R1 / (R1+Rx+Rb)= I1 / K0*ΔIf Formula (1),

[0062] wherein I30 represents the current flowing through the input side of the ratio error compensation module 3 (i.e., the primary current value flowing through the compensation current transformer 30), I1 represents the primary current flowing through the main current transformer CT1, Rx represents the resistance value of the first precision adjustable resistor 34, R1 represents the resistance value of the first standard resistor 32, Rb represents the impedance value of the rated secondary load of the main current transformer CT1, K0 represents the rated transformation ratio of the main current transformer CT1, K1 represents the current transformation ratio of the compensation current transformer 30, and ΔIf represents the ratio error compensation amount required by the main current transformer CT1. In this embodiment, the current I30 flowing through the input side of the ratio error compensation module 3 is the same as the primary current I1 flowing through the main current transformer CT1, and thus the following formula can be obtained from formula (1):

[0063] Rx=R1*K0 / (K1*ΔIf)-R1-Rb Formula (1.1),

[0064] In this way, the ratio error compensation module 3 can compensate the secondary current I20 of the main current transformer CT1 with the ratio error compensation current IX corresponding to the predetermined ratio error compensation amount of the main current transformer CT1.

[0065] The angle error compensation module 4 shown in the other dashed box of FIG. 5 comprises a hollow mutual inductor 40, a second standard resistor 42 connected in series with the secondary side coil of the hollow mutual inductor 40, and a second precision adjustable resistor 44. According to the angle error of the main current transformer CT1 under the rated operating condition, the rated transformation ratio, the rated secondary load, and the alternating current frequency of the rated operating condition, the parameters of the angle error compensation module 4 are configured, provided that the series resistance of the second standard resistor 42, the second precision adjustable resistor 44, and the secondary load of the main current transformer CT1 generates the angle error compensation current corresponding to the predetermined angle error compensation amount of the main current transformer CT1, the parameters of the angle error compensation module 4 need to be configured to satisfy the following formula (2):

[0066] RY= U40 * K0 / (ΔIδ * I1) - R2 - Rb Formula (2.1),

[0067] wherein RY represents the resistance value of the second precision adjustable resistor 44, K0 represents the rated transformation ratio of the main current transformer CT1, ΔIδ represents the required angle difference compensation amount of the main current transformer CT1, I1 represents the rated primary current value of the main current transformer CT1, R2 represents the resistance value of the second standard resistor 42, Rb represents the impedance value of the rated secondary load of the main current transformer CT1, and U40 represents the induced voltage value generated at the secondary side of the air-core mutual inductor 40. In this way, the angle difference compensation module 4 can compensate the secondary current I20 of the main current transformer CT1 with an angle difference compensation current IY corresponding to the predetermined angle difference compensation amount of the main current transformer CT1.

[0068] The induced voltage generated at the secondary side of the air-core mutual inductor 40 is equal to the product of the rate of change of the magnetic flux in the circular cross section of the air-core mutual inductor 40 and the number of turns of the secondary side coil of the air-core mutual inductor 40, and the magnetic flux in the circular cross section of the air-core mutual inductor 40 is equal to the product of the magnetic induction intensity in the air-core mutual inductor 40 and the area of the circular cross section surrounded by the air-core mutual inductor 40. It is known to those skilled in the art that the magnetic induction intensity in the air-core mutual inductor 40 is uniformly distributed at the central cross section and can be calculated by a given formula. Therefore, the induced voltage U40 generated at the secondary side of the air-core mutual inductor 40 can be obtained by the following formula:

[0069] Formula (3.1),

[0070] wherein U40 represents the induced voltage value generated at the secondary side of the air-core mutual inductor 40, μ0 represents the magnetic permeability of air, π is the circular constant, N1 and N2 represent the number of turns of the primary side and secondary side coils of the air-core mutual inductor 40, respectively, L represents the axial length of the primary side coil of the air-core mutual inductor 40, D represents the diameter of the circular cross section surrounded by the air-core mutual inductor 40, f represents the alternating current frequency of the rated operating condition, and I1 represents the rated primary current value of the main current transformer CT1 (which is the same as the current I40 flowing through the primary side coil of the air-core mutual inductor 40).

[0071] In the embodiment as shown in FIG. 3, the current transformer is configured as a main current transformer CT1 and an auxiliary current transformer CT2 connected in series at the primary side, and the current flowing through the input side of the ratio difference compensation module 3 and the angle difference compensation module 4 is the secondary current of the auxiliary current transformer CT2. In this case, the parameter configuration of the ratio difference compensation module should satisfy the following formula to enable the series branch of the first precision adjustable resistor 34 and the secondary load of the main current transformer CT1 to shunt the secondary side of the compensation current transformer 30 with a ratio difference compensation current corresponding to the predetermined ratio difference compensation amount of the main current transformer CT1:

[0072] Rx = R1 * K0 / (K1 * K2 * ΔIf) - R1 - Rb Formula (1.2),

[0073] Wherein, Rx represents the resistance of the first precision adjustable resistor 34, R1 represents the resistance of the first standard resistor 32, K0 represents the rated transformation ratio of the main current transformer CT1, K1 represents the current transformation ratio of the compensation current transformer 30, K2 represents the current transformation ratio of the auxiliary current transformer CT2, ΔIf represents the required ratio error compensation amount of the main current transformer CT1, and Rb represents the impedance value of the rated secondary load of the main current transformer CT1.

[0074] The parameter configuration of the angle error compensation module 4 should still satisfy the formula (2.1) described above. In order to distinguish the formula numbers, the parameter configuration formula number of the angle error compensation module 4 in the embodiment shown in FIG. 3 is formula (2.2).

[0075] RY = U40 * K0 / (ΔIδ * I1) - R2 - Rb Formula (2.2),

[0076] Wherein, the induced voltage value generated on the secondary side of the air-core mutual inductor 40 is obtained by the following formula:

[0077] Formula (3.2),

[0078] Wherein, U40 represents the induced voltage value generated on the secondary side of the air-core mutual inductor 40, μ0 represents the magnetic permeability of air, π is the circular constant, N1 and N2 respectively represent the number of turns of the primary side and the secondary side of the air-core mutual inductor 40, L represents the axial length of the primary side coil of the air-core mutual inductor 40, D represents the diameter of the circular cross section surrounded by the air-core mutual inductor 40, f represents the AC frequency of the rated working condition, I1 represents the rated primary current value of the main current transformer CT1, and K2 represents the current transformation ratio of the auxiliary current transformer.

[0079] Continuing to refer to FIG. 5 to explain the principle of error compensation of the main current transformer CT1, after the current ratio standardizer 2 is coupled with the AC current source AC and the secondary load 10, the current inputted by the AC current source AC to the primary side of the current ratio standardizer 2 is marked as I1, the secondary current of the main current transformer CT1 is marked as I20, the secondary current I20 is compensated by the ratio error compensation and is marked as I21, the current after further angle error compensation is marked as I22, and I22 is the current flowing through the secondary load 10 between the output terminals a and b of the current ratio standardizer 2. In other words, I22 is the secondary current of the current ratio standardizer 2.

[0080] It should be noted that, since the secondary load of the current ratio standardizer 2 is usually a resistive load with very small resistance, in order to avoid the error caused by the shunt of the secondary current I20 of the main current transformer CT1 by the branch formed by the first standard resistor 32 and the first precision adjustable resistor 34 in series of the ratio difference compensation module 3 and the branch formed by the second standard resistor 42 and the second precision adjustable resistor 44 in series of the angle difference compensation module 4 being too large, the total resistance of the first standard resistor 32 and the first precision adjustable resistor 34 and the total resistance of the second standard resistor 42 and the second precision adjustable resistor 44 should be configured to be at least three orders of magnitude larger than the impedance of the rated secondary load of the main current transformer CT1. Since the first standard resistor 32 and the second standard resistor 42 are resistors with limited resistance for protection, and the first precision adjustable resistor 34 and the second precision adjustable resistor 44 need to have a certain adjustment range, the maximum resistance of the first precision adjustable resistor 34 and the second precision adjustable resistor 44 should be configured to be at least 10000 times the impedance of the rated secondary load of the main current transformer. Preferably, the first precision adjustable resistor 34 and the second precision adjustable resistor 44 are both configured as multi-turn adjustable resistors, and the adjustment fineness can reach one ten-thousandth of the maximum resistance.

[0081] The principle of realizing ratio difference compensation and angle difference compensation by the ratio difference compensation module 3 and the angle difference compensation module 4 is based on Ohm's law, i.e., the resistance shunt principle. Since the total resistance of the first standard resistor 32 and the first precision adjustable resistor 34 and the total resistance of the second standard resistor 42 and the second precision adjustable resistor 44 are much larger than the impedance of the rated secondary load of the main current transformer CT1, the value of the ratio difference compensation current Ix injected into the secondary current I20 of the main current transformer CT1 by the ratio difference compensation module 3 is approximately I1*R1 / K1(Rx+R1+Rb), which, combined with formula (1.1), can be obtained as follows:

[0082] Ix=ΔIf*I1 / K0 Formula (4),

[0083] The current flowing through the second standard resistor 42 (i.e., the angle difference compensation current IY) is approximately IY= U40 / (RY+R2+Rb), which, combined with formula (2.1) or formula (2.2) described above, can be obtained as follows:

[0084] IY=ΔIδ*I1 / K0 Formula (5),

[0085] It should be noted that the phase difference compensation current IY and the ratio difference compensation current Ix are approximately in phase quadrature. As described above, the air-core mutual inductor 40 of the phase difference compensation module 4 generates a secondary-side induced voltage through electromagnetic induction, and the phase of the current flowing through the second standard resistor 42 is shifted by 90° compared to the phase of the current I40 flowing through the primary side of the air-core mutual inductor, while the current I40 flowing through the primary side of the air-core mutual inductor (i.e., the primary current I1 of the main current transformer CT1 in FIG. 5) is substantially in phase with the secondary current I20 of the main current transformer CT1, so the phase difference between the phase difference compensation current IY and the secondary current I20 of the main current transformer CT1 is about 90°. In contrast, the ratio difference compensation current Ix is substantially in phase with the secondary current I20 of the main current transformer CT1.

[0086] Referring to FIG. 6, a flow chart of an implementation method of the current ratio standardizer 2 according to an embodiment of the present application is shown. The method comprises the following steps: S1, obtaining an electromagnetic current transformer with an accuracy of at least 1st level and measuring its ratio error and angle error under rated operating conditions, wherein the current transformer is configured as a single primary current transformer or a primary current transformer and a secondary current transformer connected in series at the primary side; S2, calculating the ratio error compensation amount and the angle error compensation amount to be applied to the primary current transformer based on the ratio error and the angle error of the current transformer for implementing a high-accuracy current ratio standardizer; S3, configuring the parameters of the ratio error compensation module according to the rated transformation ratio, the rated secondary load and the ratio error compensation amount of the primary current transformer, and configuring the parameters of the angle error compensation module according to the rated transformation ratio, the rated secondary load, the AC frequency of the rated operating conditions and the angle error compensation amount of the primary current transformer, wherein the ratio error compensation module is formed by a compensation current transformer, a first standard resistor and a first precision adjustable resistor connected to form a four-terminal network, and the angle error compensation module is formed by a hollow mutual inductor, a second standard resistor and a second precision adjustable resistor connected to form a four-terminal network, the parameters of the ratio error compensation module include the transformation ratio of the compensation current transformer, the resistance value of the first standard resistor and the resistance value and adjustment range of the first precision adjustable resistor, and the parameters of the angle error compensation module include the number of turns and the size of the coil of the hollow mutual inductor, the resistance value of the second standard resistor and the resistance value and adjustment range of the second precision adjustable resistor; S4, connecting the ratio error compensation module and the angle error compensation module to the current transformer to form the current ratio standardizer; S5, measuring the ratio error and the angle error of the current ratio standardizer under the rated operating conditions and checking the levels of the ratio error and the angle error of the current ratio standardizer; S6, determining whether the ratio error or the angle error of the current ratio standardizer exceeds the error limit value range required by the high accuracy, and if not, the checking is qualified and goes to step S8, otherwise, it continues to step S7; S7, if the ratio error of the current ratio standardizer exceeds the ratio error limit value range required by the high accuracy, the ratio error of the current ratio standardizer is compensated by adjusting the resistance value of the first precision adjustable resistor, and if the angle error of the current ratio standardizer exceeds the angle error limit value range required by the high accuracy, the angle error of the current ratio standardizer is compensated by adjusting the resistance value of the second precision adjustable resistor, and then goes to step S5; S8, completing the implementation of the high-accuracy current ratio standardizer, i.e., the ratio error and the angle error of the current ratio standardizer are both within the error limit value range required by the high accuracy after compensation.

[0087] In the case where the electromagnetic current transformer 1 is configured as a single main current transformer CT1 as shown in Fig. 2, the coupling of the ratio difference compensation module 3 and the angle difference compensation module 4 to the current transformer in step S4 of the above method comprises: coupling the two terminals of the input side of the compensation current transformer 30 to the terminals of the primary side of the main current transformer CT1 and one terminal of the input side of the angle difference compensation module 4 respectively, so that the other terminal of the primary side of the main current transformer CT1 and the other terminal of the input side of the angle difference compensation module 4 form the input end of the current proportioning standard 2, and coupling the two terminals of the output side of the ratio difference compensation module 3 and the two terminals of the output side of the angle difference compensation module 4 to the terminals of the secondary side of the main current transformer CT1 in parallel to form the output end of the current proportioning standard 2. The parameter configuration of the ratio difference compensation module 3 and the angle difference compensation module 4 is derived according to the above-mentioned formulae 1.1, 2.1 and 3.1.

[0088] In the case where the electromagnetic current transformer 1 is configured as a primary side series connection of the main current transformer CT1 and the auxiliary current transformer CT2 as shown in Fig. 3, the coupling of the ratio difference compensation module 3 and the angle difference compensation module 4 to the current transformer in step S4 of the above method comprises: coupling the terminal of the input side of the ratio difference compensation module 3 and the terminal of the input side of the angle difference compensation module 4 in series and then coupling them to the terminals of the secondary side of the auxiliary current transformer CT2 in parallel, coupling the two terminals of the output side of the ratio difference compensation module 3 and the two terminals of the output side of the angle difference compensation module 4 to the terminals of the secondary side of the main current transformer CT1 in parallel to form the output end of the current proportioning standard, and the terminals of the primary side of the main current transformer CT1 and the auxiliary current transformer CT2 which are not series connected form the input end of the current proportioning standard. The parameter configuration of the ratio difference compensation module 3 and the angle difference compensation module 4 is derived according to the above-mentioned formulae 1.2, 2.2 and 3.2.

[0089] In practice, the terminals of the output side of the ratio difference compensation module 3 and the terminals of the secondary side of the main current transformer CT1 can be configured to be coupled in pairs of opposite name terminals or in pairs of same name terminals according to the positive or negative of the ratio difference of the main current transformer CT1. Similarly, the terminals of the output side of the angle difference compensation module 4 and the terminals of the secondary side of the main current transformer CT1 can be configured to be coupled in pairs of opposite name terminals or in pairs of same name terminals according to the positive or negative of the angle difference of the main current transformer CT1.

[0090] It can be understood that the significant advantage of the ratio difference compensation module 3 configured according to the present application is that when the ratio difference of the current proportioning standard 2 needs to be compensated because it is out of limit, the ratio difference can be accurately compensated by continuously adjusting the resistance value Rx of the first precision adjustable resistor 34. Similarly, the significant advantage of the angle difference compensation module 4 is that when the angle difference of the current proportioning standard 2 needs to be compensated because it is out of limit, the angle difference can also be accurately compensated by continuously adjusting the resistance value RY of the second precision adjustable resistor 44. The compensation process of the ratio difference and the angle difference is continuous, linear and controllable.

[0091] Figure 7 shows a vector diagram of error compensation of the current ratio standard 2 according to an embodiment of the present application. Referring to Figures 5 and 7 simultaneously, assuming that I1 is the input current of the current ratio standard 2, and I20 is the secondary current of the primary current transformer CT1 in the current ratio standard 2, the error compensation process of the current ratio standard 2 is as follows: first, the secondary current I20 of the primary current transformer CT1 is subjected to vector compensation of the ratio difference compensation current Ix by the ratio difference compensation module 3, and the vector of the secondary current I20 of the primary current transformer CT1 changes to I21 after ratio difference compensation; then, the current I21 of the primary current transformer CT1 after ratio difference compensation is further subjected to vector compensation of the angle difference compensation current IY by the angle difference compensation module 4, and finally the primary current transformer CT1 is compensated for the vector current AI = Ix + j * IY, where j is the imaginary unit, and the secondary current I20 of the primary current transformer CT1 changes to I22 after compensation of the vector current AI, i.e., the output current of the current ratio standard 2. In Figure 7, the vectors of the ratio difference compensation current Ix and the angle difference compensation current IY are approximately orthogonal, and their vector sum is the vector current AI to be compensated, where a is the included angle of the vector current AI to be compensated relative to the secondary current vector I20, and θ is the final angle compensation amount.

[0092] For the current ratio standard 2 formed by adding the ratio difference compensation module 3 and the angle difference compensation module 4 to the primary current transformer CT1, in some cases, the ratio difference or angle difference between the output current I22 after ratio difference compensation and angle difference compensation based on the secondary current of the primary current transformer CT1 and the input current I1 of the current ratio standard 2 may still not meet the ratio difference and angle difference required by the high-accuracy current ratio standard 2. In this case, only the ratio difference and angle difference of the current ratio standard 2 under the rated operating condition need to be measured and the predetermined ratio difference compensation amount or the predetermined angle difference compensation amount required to achieve a high-accuracy current ratio standard need to be calculated, and the ratio difference between the output current and the input current of the current ratio standard 2 can still be compensated by the ratio difference compensation module 3 by a predetermined ratio difference compensation amount, and the angle difference between the output current and the input current of the current ratio standard 2 can still be compensated by the angle difference compensation module 4 by a predetermined angle difference compensation amount.

[0093] Specifically, if the ratio error of the current ratio standardizer 2 exceeds the ratio error limit value range of the high accuracy requirement, the ratio error of the current ratio standardizer 2 can be compensated by adjusting the resistance value of the first precision adjustable resistor 34 until the ratio error measured by the current ratio standardizer 2 under the rated working condition is within the ratio error limit value range of the high accuracy requirement; similarly, if the angle error of the current ratio standardizer 2 exceeds the angle error limit value range of the high accuracy requirement, the angle error of the current ratio standardizer 2 can be compensated by adjusting the resistance value of the second precision adjustable resistor 44 until the angle error measured by the current ratio standardizer 2 under the rated working condition is within the angle error limit value range of the high accuracy requirement. In this way, the current ratio standardizer 2 can be ensured to maintain high accuracy after error compensation. The vector diagram of the error compensation of the current ratio standardizer 2 is similar to the description above with reference to Figure 7, only the vectors in the diagram are replaced by the corresponding vectors of the current ratio standardizer 2, for example, I20, Ix, IY are replaced by the secondary current vector, the ratio error compensation current, and the angle error compensation current of the current ratio standardizer 2 respectively, and the compensation principle is the same as described above, which will not be described here.

[0094] The significant advantages of the present application include: (1) a current ratio standardizer with an accuracy of not less than 0.02 level is conveniently realized by using a general primary current transformer with an accuracy of at least 1 level; (2) in the case that the error of the current ratio standardizer exceeds the rated limit value range, the ratio error and the angle error of the current ratio standardizer can be respectively adjusted by continuous error compensation, so that the current ratio standardizer reaches high accuracy, and the compensation process of the ratio error and the angle error is continuous, linear, and controllable, thereby ensuring that the error of the current ratio standardizer is within the error limit value range of the high accuracy requirement; (3) the angle error compensation module of the current ratio standardizer uses a hollow mutual inductor to obtain an angle error current component orthogonal to the secondary current vector, the accuracy of the angle error compensation is higher, and the high-frequency response performance is better, which can be applied to wideband error compensation of the current ratio standardizer.

[0095] The technical features of the above embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above embodiments are described, however, as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the present disclosure.

[0096] It should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; under the idea of the present application, the technical features in the above examples or different examples can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the present application as described above, which are not provided in details for simplicity; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application. For ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application.

Claims

1. A high-accuracy current ratio standardizer characterized by, The current ratio standardizer comprises a primary current transformer with an accuracy of at least 1st grade, a ratio difference compensation module and an angle difference compensation module coupled with the primary current transformer, wherein the ratio difference compensation module is coupled with a compensation current transformer, a first standard resistor and a first precision adjustable resistor to form a four-terminal network, the angle difference compensation module is coupled with a hollow mutual inductance coil, a second standard resistor and a second precision adjustable resistor to form a four-terminal network, two terminals of the input side of the ratio difference compensation module are coupled with a terminal of the primary current transformer and one terminal of the input side of the angle difference compensation module respectively, the other terminal of the primary current transformer and the other terminal of the input side of the angle difference compensation module form an input terminal of the current ratio standardizer, and two terminals of the output side of the ratio difference compensation module and two terminals of the output side of the angle difference compensation module are both connected in parallel between terminals of the secondary side of the primary current transformer to form an output terminal of the current ratio standardizer, wherein the ratio difference compensation module is configured to compensate the ratio difference of the current ratio standardizer by adjusting the first precision adjustable resistor to achieve a predetermined ratio difference compensation amount based on the predetermined ratio difference compensation amount, so that the ratio difference of the current ratio standardizer is within a range of ratio difference limit values required by high accuracy, and the angle difference compensation module is configured to compensate the angle difference of the current ratio standardizer by adjusting the second precision adjustable resistor to achieve a predetermined angle difference compensation amount based on the predetermined angle difference compensation amount, so that the angle difference of the current ratio standardizer is within a range of angle difference limit values required by high accuracy.

2. The high-accuracy current ratio standarder of claim 1, wherein, The transformation ratio of the compensation current transformer of the ratio difference compensation module, the resistance value of the first standard resistor and the resistance value and adjustment range of the first precision adjustable resistor are configured according to the ratio difference, the rated transformation ratio and the rated secondary load of the primary current transformer under the rated working condition, and the number of turns and the coil size of the hollow mutual inductance coil of the angle difference compensation module, the resistance value of the second standard resistor and the resistance value and adjustment range of the second precision adjustable resistor are configured according to the angle difference, the rated transformation ratio, the rated secondary load and the AC frequency of the rated working condition of the primary current transformer under the rated working condition.

3. The high-accuracy current ratio standarder of claim 1, wherein, The first precision adjustable resistor and the second precision adjustable resistor are both multi-turn adjustable resistors, and the maximum resistance value of the first precision adjustable resistor and the second precision adjustable resistor is configured to be at least 10000 times the impedance of the rated secondary load of the primary current transformer.

4. A high-accuracy current ratio standardizer characterized by, The current ratio standardizer comprises a primary current transformer and a secondary current transformer which are series-connected at a primary side and have an accuracy of at least 1 level, and a ratio difference compensation module and an angle difference compensation module coupled with the primary current transformer and the secondary current transformer, wherein the ratio difference compensation module is formed into a four-terminal network by a compensation current transformer, a first standard resistor and a first precision adjustable resistor, the angle difference compensation module is formed into a four-terminal network by a hollow mutual inductance coil, a second standard resistor and a second precision adjustable resistor, terminals of the primary current transformer and the secondary current transformer which are not series-connected at the primary side form an input end of the current ratio standardizer, terminals of an input side of the ratio difference compensation module and terminals of an input side of the angle difference compensation module are series-connected and then connected in parallel between terminals of a secondary side of the secondary current transformer, two terminals of an output side of the ratio difference compensation module and two terminals of an output side of the angle difference compensation module are both connected in parallel between terminals of a secondary side of the primary current transformer, forming an output end of the current ratio standardizer, wherein the ratio difference compensation module is configured to compensate a predetermined ratio difference compensation amount by adjusting the first precision adjustable resistor to achieve the predetermined ratio difference compensation amount for the ratio difference of the current ratio standardizer, so that the ratio difference of the current ratio standardizer is within a ratio difference limit value range of a high accuracy requirement, and the angle difference compensation module is configured to compensate a predetermined angle difference compensation amount by adjusting the second precision adjustable resistor to achieve the predetermined angle difference compensation amount for the angle difference of the current ratio standardizer, so that the angle difference of the current ratio standardizer is within an angle difference limit value range of a high accuracy requirement.

5. The high-accuracy current ratio standarder of claim 4, wherein, The transformation ratio of the compensation current transformer of the ratio difference compensation module, the resistance value of the first standard resistor, and the resistance value and adjustment range of the first precision adjustable resistor are configured according to the ratio difference, the rated transformation ratio, the rated secondary load of the primary current transformer under a rated operating condition, and the current transformation ratio of the secondary current transformer, and the number of turns and the coil size of the hollow mutual inductance coil of the angle difference compensation module, the resistance value of the second standard resistor, and the resistance value and adjustment range of the second precision adjustable resistor are configured according to the angle difference, the rated transformation ratio, the rated secondary load of the primary current transformer under the rated operating condition, the alternating current frequency of the rated operating condition, and the current transformation ratio of the secondary current transformer.

6. The high-accuracy current ratio standarder of claim 4, wherein, The first precision adjustable resistor and the second precision adjustable resistor are both multi-coil adjustable resistors, and the maximum resistance value of the first precision adjustable resistor and the second precision adjustable resistor is configured to be at least 10000 times of the impedance of the rated secondary load of the primary current transformer.

7. A method of implementing a high-accuracy current ratio standardizer, characterized by, The method comprises the following steps: S1, obtaining an electromagnetic current transformer with an accuracy of at least 1 level and measuring the ratio difference and the angle difference thereof under a rated operating condition, wherein the electromagnetic current transformer is configured as a single primary current transformer or a primary current transformer and a secondary current transformer which are series-connected at a primary side; S2, calculating a ratio difference compensation amount and an angle difference compensation amount which need to be applied to the primary current transformer to realize the high-accuracy current ratio standardizer based on the ratio difference and the angle difference of the current transformer; S3, configuring parameters of the ratio difference compensation module according to a rated transformation ratio, a rated secondary load of the main current transformer and the ratio difference compensation amount, and configuring parameters of the angle difference compensation module according to the rated transformation ratio, the rated secondary load of the main current transformer, an AC frequency of the rated operating condition and the angle difference compensation amount, wherein the ratio difference compensation module is formed into a four-terminal network by a compensation current transformer, a first standard resistor and a first precision adjustable resistor, the angle difference compensation module is formed into a four-terminal network by a hollow mutual inductance coil, a second standard resistor and a second precision adjustable resistor, the parameters of the ratio difference compensation module include a transformation ratio of the compensation current transformer, a resistance value of the first standard resistor and a resistance value and an adjusting range of the first precision adjustable resistor, and the parameters of the angle difference compensation module include a number of turns and a coil size of the hollow mutual inductance coil, a resistance value of the second standard resistor and a resistance value and an adjusting range of the second precision adjustable resistor; S4, connecting the ratio difference compensation module and the angle difference compensation module to the current transformer, thereby forming the current ratio standardizer; S5, measuring ratio difference and angle difference of the current ratio standardizer under a rated operating condition, and checking grades of the ratio difference and the angle difference of the current ratio standardizer; S6, judging whether the ratio difference or the angle difference of the current ratio standardizer exceeds an error limit value range required by high accuracy, and if not, then passing the check and going to step S8, otherwise, going to step S7; S7, if the ratio difference of the current ratio standardizer exceeds a ratio difference limit value range required by high accuracy, then compensating the ratio difference of the current ratio standardizer by adjusting the resistance value of the first precision adjustable resistor, if the angle difference of the current ratio standardizer exceeds an angle difference limit value range required by high accuracy, then compensating the angle difference of the current ratio standardizer by adjusting the resistance value of the second precision adjustable resistor, and then going to step S5; S8, completing the high accuracy current ratio standardizer.

8. The method of claim 7, wherein, In the case that the electromagnetic current transformer is configured as a single main current transformer, connecting the ratio difference compensation module and the angle difference compensation module to the current transformer includes: connecting two terminals of an input side of the compensation current transformer to a terminal of a primary side of the main current transformer and one terminal of an input side of the angle difference compensation module respectively, so that another terminal of the primary side of the main current transformer and another terminal of the input side of the angle difference compensation module form an input terminal of the current ratio standardizer, and connecting two terminals of an output side of the ratio difference compensation module and two terminals of an output side of the angle difference compensation module to terminals of a secondary side of the main current transformer in parallel, forming an output terminal of the current ratio standardizer, thereby the parameters of the ratio difference compensation module are configured to satisfy the following formula: Rx=R1*K0 / (K1*ΔIf)-R1-Rb Formula (1.1), Wherein, Rx represents the resistance of the first precision adjustable resistor, R1 represents the resistance of the first standard resistor, K0 represents the rated transformation ratio of the main current transformer, K1 represents the current transformation ratio of the compensation current transformer, ΔIf represents the ratio difference compensation amount, and Rb represents the impedance value of the rated secondary load of the main current transformer; The parameter configuration of the angle difference compensation module satisfies the following formula: RY=U40*K0 / (ΔIδ*I1)-R2-Rb Formula (2.1), RY=U40*K0 / (ΔIδ*I1)-R2-Rb Formula (2.1), Wherein, RY represents the resistance of the second precision adjustable resistor, K0 represents the rated transformation ratio of the main current transformer, ΔIδ represents the angle difference compensation amount, I1 represents the rated primary current value of the main current transformer, R2 represents the resistance of the second standard resistor, Rb represents the impedance value of the rated secondary load of the main current transformer, and U40 represents the induced voltage value generated on the secondary side of the air-core mutual inductor. The induced voltage on the secondary side of the air-core mutual inductor is obtained by the following formula: Formula (3.1), 9. The method of claim 7, wherein, Wherein, U40 represents the induced voltage value generated on the secondary side of the air-core mutual inductor, μ0 represents the magnetic permeability of air, π is the circular constant, N1 and N2 respectively represent the number of turns of the primary side and the secondary side of the air-core mutual inductor, L represents the axial length of the primary side coil of the air-core mutual inductor, D represents the diameter of the circular cross section surrounded by the air-core mutual inductor, f represents the alternating current frequency of the rated working condition, and I1 represents the rated primary current value of the main current transformer. In the case that the electromagnetic current transformer is configured as a primary side series connection of a main current transformer and a secondary current transformer, the connection of the ratio difference compensation module and the angle difference compensation module to the current transformer comprises: connecting the terminals on the input side of the ratio difference compensation module and the terminals on the input side of the angle difference compensation module in series and connecting them between the terminals on the secondary side of the secondary current transformer; connecting the two terminals on the output side of the ratio difference compensation module and the two terminals on the output side of the angle difference compensation module between the terminals on the secondary side of the main current transformer to form the output end of the current ratio standardizer; and the terminals not connected in series on the primary side of the main current transformer and the secondary current transformer form the input end of the current ratio standardizer, so that the parameter configuration of the ratio difference compensation module satisfies the following formula: Rx=R1*K0 / (K1*K2*ΔIf)-R1-Rb Formula (1.2), Wherein, Rx represents the resistance of the first precision adjustable resistor, R1 represents the resistance of the first standard resistor, K0 represents the rated transformation ratio of the main current transformer, K1 represents the current transformation ratio of the compensation current transformer, K2 represents the current transformation ratio of the secondary current transformer, ΔIf represents the ratio difference compensation amount, and Rb represents the impedance value of the rated secondary load of the main current transformer; The parameter configuration of the angle difference compensation module satisfies the following formula: RY=U40*K0 / (ΔIδ*I1)-R2-Rb Formula (2.2), RY=U40*K0 / (ΔIδ*I1)-R2-Rb Formula (2.1), RY / K0*ΔIδ=I1*(R2+Rb) / R2, The induced voltage of the secondary side of the air-core mutual inductor is obtained by the following formula: Formula (3.2), Wherein, U40 represents the induced voltage value generated by the secondary side of the air-core mutual inductor, μ0 represents the magnetic permeability of air, π is the circular constant, N1 and N2 respectively represent the number of turns of the primary side and the secondary side of the air-core mutual inductor, L represents the axial length of the primary side coil of the air-core mutual inductor, D represents the diameter of the circular cross section surrounded by the air-core mutual inductor, f represents the AC frequency of the rated operating condition, I1 represents the rated primary current value of the main current transformer, and K2 represents the current transformation ratio of the auxiliary current transformer.

10. The method according to any one of claims 7 to 9, characterized in that, The first precision adjustable resistor and the second precision adjustable resistor are both multi-turn adjustable resistors, and the maximum resistance value of the first precision adjustable resistor and the second precision adjustable resistor is configured to be at least 10000 times the impedance of the rated secondary load of the main current transformer.

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