System for measuring characteristics of current transformer and control method thereof

Abstract

A system for measuring characteristics of a current transformer according to an embodiment of the present invention comprises: a power source having a constant voltage; a current transformer to be tested to measure characteristics; a first current transformer including a core on which a primary winding and a secondary winding are wound, respectively; a voltage regulator which varies the voltage applied from the power source and applies the varied voltage to the primary winding; a power cable which is formed to pass through the core of the current transformer to be tested and through which a current corresponding to the voltage of the secondary winding induced according to the voltage applied to the primary winding flows; a shunt resistor which connects both ends of the power cable to form a circuit composed of the power cable; a detection unit for detecting the voltage of the shunt resistor and the output current of the current transformer to be tested; and a measurement unit which receives the voltage value of the shunt resistor and the output current value of the current transformer to be tested from the detection unit and compares the current value calculated from the voltage value of the shunt resistor with the output current value of the current transformer to be tested so as to measure the characteristics of the current transformer to be tested.

Description

A system for measuring the characteristics of a current transformer and a method for controlling the system

[0001] The present invention relates to a measurement system capable of measuring the characteristics of a current transformer.

[0002] Typically, current transformers (CTs) used to detect current in power systems are classified into iron-core type, which have a core formed of iron, and air-core type, which do not have an iron core, and they both have the function of converting the input current into a small, measurable current level. Representative characteristics of such current transformers include the magnitude of the output of the secondary output current relative to the primary input current (hereinafter referred to as output characteristics), the linearity of the output magnitude (hereinafter referred to as linearity characteristics), and the phase delay characteristics of the output current. When developing or mass-producing power products, it is necessary to measure the characteristics of the current transformer used in the power products being developed or mass-produced and to verify whether the measured characteristics of the current transformer fall within a pre-set standard.

[0003] Meanwhile, a method commonly used to verify the characteristics of such a current transformer is to provide a current source for applying a large current and a measuring current transformer having a precision of a certain level or higher, and to compare the detection value detected by the measuring current transformer from the current source with the detection value detected by the current transformer under test from the current source. In this case, the detection value detected by the measuring current transformer can serve as a reference value for detecting the characteristics of the current transformer under test, and the characteristics of the current transformer under test can be measured based on the difference between the reference value and the detection value of the current transformer under test.

[0004] However, when measuring the characteristics of a current transformer under test in this manner, there is a problem in that a current source capable of outputting currents ranging from small currents of a few mA to large currents of thousands of amperes is required, and the output of said current source must also be stable and precise. Consequently, a current source capable of high-precision, high-current output is required, and there is a problem in that expensive equipment is needed to generate such a current source.

[0005] Furthermore, in the case of a measuring current transformer used to detect reference values, the more precise it is, the more accurately it can output the current from the current source, thereby enabling accurate measurement of the characteristics of the current transformer under test. However, there is a problem in that higher precision in the current transformer leads to higher costs and larger volume. Moreover, no matter how high the precision of the current transformer is, the measuring current transformer also possesses linearity and delay characteristics, and there is a problem in that these characteristics of the measuring current transformer can act as errors when detecting the characteristics of the current transformer under test.

[0006] In addition, the conventional current transformer measurement method involves receiving and comparing the detection value detected from the measuring current transformer and the detection value detected from the current transformer under test, respectively. In this case, the measurement unit measuring the characteristics of the current transformer under test receives the detection values ​​detected from each current transformer through a pre-set communication method. However, there is a problem in that it is difficult to verify the data at the same time due to the time difference caused by the communication of the two detection values, which results in measurement errors and errors in the current transformer characteristic measurement system.

[0007] The present invention aims to solve the aforementioned problems and other problems, and aims to provide a current transformer characteristic measurement system and a control method said system that can detect the characteristics of a current transformer under test without expensive high-precision current sources and high-precision measuring current transformers.

[0008] Furthermore, the present invention aims to provide a characteristic measurement system for a current transformer and a control method for the system that satisfy simultaneity, capable of simultaneously detecting a detection value of an input current and a detection value of a current transformer under test for said input current.

[0009] Furthermore, the present invention aims to provide a current transformer characteristic measurement system and a control method for the system that can minimize measurement errors regarding the characteristics of the current transformer.

[0010] According to one aspect of the present invention for achieving the above or other purposes, a current transformer characteristic measurement system according to an embodiment of the present invention comprises: a power source that outputs a current having a voltage of a preset size; a current transformer (CT) to be tested whose characteristics are to be measured; a first current transformer including a core on which a primary winding and a secondary winding are each wound; a voltage regulator that varies the voltage applied from the power source to another voltage and applies the varied voltage to the primary winding; a power cable formed to penetrate the core of the current transformer to be tested and connected to the secondary winding so that a current corresponding to the voltage of the secondary winding induced according to the voltage applied to the primary winding flows; a shunt resistor that connects both ends of the power cable to form a circuit made of the power cable; a detection unit that simultaneously detects the voltage of the shunt resistor and the output current of the current transformer to be tested; and from the detection unit, the voltage value of the shunt resistor and the current transformer to be tested It is characterized by including a measuring unit that receives the output current value of a current transformer and measures the characteristics of the current transformer under test by comparing the current value calculated from the voltage value of the shunt resistor with the output current value of the current transformer under test.

[0011] In one embodiment, the primary winding and the secondary winding of the first current transformer are each wound on the core of the first current transformer such that the winding ratio is less than 1, and a voltage greater than the voltage applied from the voltage regulator is induced in the secondary winding.

[0012] In one embodiment, the voltage regulator is a variable voltage regulator capable of varying the input voltage to any one of a plurality of different set voltages, and the measuring unit controls the variable voltage regulator to vary the voltage of the power source to a specific set voltage corresponding to the input current magnitude of the current transformer under test.

[0013] In one embodiment, the measuring unit is characterized by determining the set voltage based on the resistance values ​​of the power cable and the shunt resistor, and the winding ratio of the first current transformer.

[0014] In one embodiment, the measuring unit further comprises a memory that stores information on the output voltage magnitudes of different variable voltage regulators corresponding to each of the input current magnitudes of a plurality of different current transformers under test, and is characterized by determining the output voltage magnitude of the variable voltage regulator applied to the primary winding based on the identification result of the current transformer under test or the input current information received from the current transformer under test.

[0015] In one embodiment, the variable voltage regulator has a core with a winding wound thereon and is formed to vary the voltage according to the number of windings at a position corresponding to the position of the stop bar, and the current transformer characteristic measurement system further includes a control motor that changes the position of the stop bar according to the control of the measurement unit based on the magnitude of the output voltage of the determined variable voltage regulator.

[0016] In one embodiment, the power source is characterized as being a commercial power source.

[0017] In one embodiment, the secondary winding is characterized by being formed as part of the power cable.

[0018] In one embodiment, the measuring unit calculates an input current value of the current transformer under test from the voltage of the shunt resistor based on the resistance value of the power cable circuit formed by the power cable and the shunt resistor, and compares the calculated input current value with the output current value of the current transformer under test in real time to measure the linearity characteristics of the current transformer under test and the output characteristics of the output current with respect to the input current.

[0019] In one embodiment, the measuring unit is characterized by measuring the phase delay characteristic of the current transformer under test by comparing in real time the phase change of the input current of the current transformer under test calculated from the change in the voltage value of the shunt resistor and the phase change according to the output current of the current transformer under test.

[0020] According to one aspect of the present invention for achieving the above or other purposes, a control method for a current transformer characteristic measurement system according to an embodiment of the present invention comprises: a step of determining a set voltage according to the magnitude of the input current of a current transformer under test; a step of varying the output voltage of a power source that outputs a current having a preset magnitude of voltage according to the determined set voltage; a step of applying the varied voltage to the primary winding of a first current transformer to induce a voltage according to the winding ratio of the first current transformer in the secondary winding of the first current transformer; a step of detecting the voltage of a power cable connected to the secondary winding, having both ends connected to a shunt resistor to form a circuit, and formed to penetrate the core of the current transformer under test through the shunt resistor, while simultaneously detecting the output current of the current transformer under test that detects the current of the power cable penetrating the core; a step of calculating a current according to the voltage of the shunt resistor; and the output current of the current transformer under test detected simultaneously with the voltage of the shunt resistor and the shunt It is characterized by including a step of measuring the characteristics of the current transformer under test by comparing the current calculated according to the voltage of the resistance in real time.

[0021] In one embodiment, the step of determining the set voltage comprises: a step of identifying the type of the current transformer to be tested; a step of determining the input current according to the identified type of the current transformer to be tested; and a step of detecting one of a plurality of set voltages corresponding to the determined input current among a plurality of set voltages for forming different input currents of the current transformer to be tested based on the winding ratio of the first current transformer and the resistance value of the circuit formed by the power cable.

[0022] According to at least one embodiment of the present invention, the present invention can generate a high-precision current source with constant voltage and current magnitudes by converting a current output from a commercial power source into a high current of a desired magnitude using a variable voltage regulator. Furthermore, by using a shunt resistor instead of a conventional measuring current transformer to detect changes in the output current of the current source in real time, a reference value that does not exhibit linearity or phase delay characteristics can be detected. Accordingly, there is an effect that not only can the characteristics of a current transformer under test be measured without a high-precision current source and a high-precision measuring current transformer, but the characteristics of the current transformer under test can also be measured without errors caused by the characteristics of the measuring current transformer.

[0023] Furthermore, the present invention receives the detection value of the current transformer under test and the detection value detected from the shunt resistor together, and can compare the received values ​​with each other. Accordingly, since the input value (input current) and the detection value (detection value of the current transformer under test) satisfy simultaneity, there is an effect of being able to measure the characteristics of the current transformer under test more intuitively.

[0024] FIG. 1 is a block diagram illustrating the configuration of a current transformer characteristic measurement system according to an embodiment of the present invention.

[0025] FIG. 2 is a flowchart illustrating the operation process of measuring the characteristics of a current transformer under test in a current transformer characteristic measurement system according to an embodiment of the present invention.

[0026] Figure 3 is a block diagram illustrating an example of a conventional current transformer characteristic measurement system.

[0027] It should be noted that technical terms used in this specification are used merely to describe specific embodiments and are not intended to limit the invention. Additionally, singular expressions used in this specification include plural expressions unless the context clearly indicates otherwise. The suffixes "module" and "part" for components used in the following description are assigned or used interchangeably solely for the ease of drafting the specification and do not inherently possess distinct meanings or roles.

[0028] In this specification, terms such as "composed of" or "comprising" should not be interpreted as necessarily including all of the various components or steps described in the specification, and should be interpreted as potentially excluding some of the components or steps, or including additional components or steps.

[0029] In addition, when describing the technology disclosed in this specification, if it is determined that a detailed description of related prior art could obscure the essence of the technology disclosed in this specification, such detailed description is omitted.

[0030] In addition, the attached drawings are intended only to facilitate understanding of the embodiments disclosed in this specification, and the technical concept disclosed in this specification is not limited by the attached drawings; it should be understood that they include all modifications, equivalents, and substitutions that fall within the concept and technical scope of the present invention. Furthermore, not only each of the embodiments described below, but also combinations of embodiments may fall within the concept and technical scope of the present invention as modifications, equivalents, and substitutions that fall within the concept and technical scope of the present invention.

[0031] Hereinafter, embodiments disclosed in this specification will be described in detail with reference to the attached drawings.

[0032] FIG. 1 is a block diagram illustrating the configuration of a current transformer characteristic measurement system according to an embodiment of the present invention.

[0033] Referring to FIG. 1, a current transformer characteristic measurement system according to an embodiment of the present invention comprises a commercial power source (100) having a constant current and voltage, a variable AC autotransformer (102), a first current transformer (106) with a primary winding connected to the variable AC autotransformer (102), a current transformer (110) to be tested for detecting characteristics, a power cable (108) connected to a secondary winding wound on the core of the first current transformer (106), penetrating the core of the current transformer (110) to be tested, and forming a circuit connected through the shunt resistor (112), a detection unit (114) connected to the shunt resistor (112) and the current transformer (110) to detect the voltage of the shunt resistor (112) and the output current of the current transformer (110) to be tested, and the current of the current transformer to be tested based on the detection result of the detection unit (114). It may be configured to include a measuring unit (116) for measuring the characteristics of the transformer (110).

[0034] Additionally, the current transformer characteristic measurement system may further include a control motor (104) capable of controlling the variable voltage regulator (102). The control motor (104) can control the variable voltage regulator (102) to vary the output voltage of the commercial power supply (100) to a specific voltage according to the control of the measurement unit (116).

[0035] The components illustrated in FIG. 1 above are not essential for implementing a current transformer characteristic measurement system, so the current transformer characteristic measurement system described herein may have more or fewer components than those listed above.

[0036] First, the commercial power supply (100) is a power supply typically provided by a power supplier and may be a power supply that outputs an alternating current having a voltage of a preset size. That is, the commercial power supply (100) may be a general power supply that supplies power to conventional power devices.

[0037] Meanwhile, a current transformer characteristic measurement system according to an embodiment of the present invention may have a variable voltage regulator (102) connected to the commercial power supply (100), and the output of the variable voltage regulator (102) may be connected to the primary winding of the first current transformer (106). Here, the variable voltage regulator (102) may be a slide-AC or sli-ac ('SLIDE-AC', or abbreviated as 'SLIDAC') in which the voltage is varied according to the position of the stop bar in a form in which the winding is wound on a core.

[0038] Meanwhile, the first current transformer (106) can vary the current connected to the secondary winding according to the winding ratio of the primary winding and the secondary winding. In this case, the power cable (108) connected to the secondary winding of the first current transformer (106) forms a circuit through the shunt resistor (112), so that the current according to the voltage induced through the secondary winding can flow through the power cable (108). For example, the secondary winding may be a part of the power cable (108).

[0039] Here, the circuit formed by the power cable (108) has a fixed resistance value (R), including the resistance value of the shunt resistor (112). Therefore, when the voltage of the primary winding, i.e., the primary voltage, is varied, the voltage of the secondary winding induced by the primary winding, i.e., the secondary voltage, can be varied. In this case, when the voltage (V) of the secondary winding is varied, the current (I) can be varied (V = I × R) according to the changed voltage. In addition, since the secondary winding of the first current transformer (106) is connected to the power cable (108) which forms a circuit with both ends connected through the shunt resistor (112), the current (I) flowing through the power cable (108) can be varied according to the variation of the voltage (V) of the secondary winding.

[0040] In this case, since the primary voltage is the voltage of the commercial power supply (100) that is varied by the variable voltage regulator (102), the current flowing through the circuit formed by the power cable (108) can be varied according to the magnitude of the secondary voltage induced by the voltage regulated by the variable voltage regulator (102). That is, the current flowing through the circuit formed by the power cable (108) can be adjusted to a magnitude corresponding to the voltage regulated by the variable voltage regulator (102), and accordingly, a circuit can be formed in which a current of a magnitude precisely adjusted by the variable voltage regulator (102) flows.

[0041] For example, when the voltage is increased by the variable voltage regulator (102), the current flowing through the circuit formed by the power cable (108) may be increased, and when the voltage is decreased by the variable voltage regulator (102), the current flowing through the circuit formed by the power cable (108) may be decreased.

[0042] Meanwhile, current transformers may be frequently used for measuring large currents with a current magnitude exceeding a certain level. Accordingly, the current transformer characteristic measurement system according to the embodiment of the present invention may be a system for measuring the characteristics of a current transformer (110) to be tested for measuring large currents. In this case, the first current transformer (106) may form a circuit through which a large current flows to detect the characteristics of the current transformer (110) to be tested by stepping up the voltage.

[0043] Here, the winding ratio (a) of the first current transformer (106) can be formed such that the number of secondary windings is greater than the number of primary windings for voltage increase, considering that the winding ratio (a) is calculated as the number of primary windings relative to the number of secondary windings (a = N1 / N2 = (number of primary windings) / (number of secondary windings)).

[0044] That is, the winding ratio (a) of the first current transformer (106) can be formed to have a value less than 1. And according to the winding ratio (a), if the number of secondary windings is greater than the number of primary windings, a voltage greater than the voltage of the primary winding can be induced in the secondary winding, and accordingly, a current greater than the current flowing in the primary winding can flow in the secondary winding. And the current flowing in the secondary winding can flow along the power cable (108).

[0045] Meanwhile, the power cable (108) may be formed to penetrate the core of the current transformer (110) to be tested, the characteristics of which are to be measured. The current transformer (110) to be tested may detect the current flowing through the power cable (108) penetrating the core, i.e., the input current of the current transformer (110), and output the detection result to the detection unit (114).

[0046] Additionally, the power cable (108) can form a circuit by connecting both ends to each other through a shunt resistor (112). Accordingly, the voltage of the shunt resistor (112) can be determined (V = I × R) based on the size of the shunt resistor (112) and the current flowing through the shunt resistor (112), i.e., the current of the power cable (108). Therefore, since the voltage of the shunt resistor (112) is the current flowing in the circuit formed by the power cable (108), the magnitude of the current flowing in the circuit formed by the power cable (108) can be detected based on the voltage detected through the shunt resistor (112). That is, the input current of the current transformer (110) under test can be detected based on the magnitude of the voltage flowing through the shunt resistor (112).

[0047] In this case, the detector (114) can detect voltage from the shunt resistor (112) and current from the current transformer (110) under test. Accordingly, the detector (114) can detect the voltage of the shunt resistor (112) and the output current of the current transformer (110) under test through different terminals. Accordingly, the detector (114) can simultaneously detect the voltage of the shunt resistor (112) and the output current of the current transformer (110) under test, and transmit the simultaneously detected values ​​together to the measurement unit (116).

[0048] In this case, since the resistance value of the shunt resistor (112), that is, the resistance value of the power cable (108) circuit, is a predetermined value, the measuring unit (116) can calculate a current value corresponding to the voltage value detected from the shunt resistor (112) based on the known resistance value of the power cable (108) circuit. Then, the calculated current value can be compared with the output current value of the current transformer (110) under test detected by the detection unit (114) simultaneously with the voltage of the shunt resistor (112). In this case, the current value calculated based on the resistance value of the shunt resistor (112) is the current value flowing through the power cable (108) passing through the current transformer (110) under test, and may be the input current input to the current transformer (110) under test. That is, the current value calculated based on the resistance value of the shunt resistor (112) can serve as a reference value for the output current value of the current transformer (110) under test.

[0049] Accordingly, in the case of the current transformer characteristic measurement system according to the embodiment of the present invention illustrated in FIG. 1, the reference value of the input current of the current transformer (110) under test and the output current value (comparison value) of the current transformer (110) under test can be measured simultaneously. That is, the simultaneity of the reference value and the comparison value can be satisfied.

[0050] Meanwhile, since the simultaneity of the reference value and the comparison value is satisfied in this way, the phase of the output current of the current transformer under test (110) detected simultaneously with the current detected through the shunt resistor (112) can be compared to detect the phase of the output current of the current transformer under test (110). In this case, the shunt resistor (112) can detect the phase of the current based simply on the voltage change, so unlike conventional high-precision current transformers, no phase delay may occur. Therefore, in the present invention, the phase change of the power cable (108) circuit can be reflected in the current detected through the shunt resistor (112) in real time, and the phase delay characteristic of the output current of the current transformer under test (110) can be detected more intuitively and effectively.

[0051] In addition, regarding linearity characteristics, the current value flowing through the power cable (108) circuit can be changed by varying the voltage of the primary winding of the first current transformer (106) using the variable voltage regulator (102). In this case, the change in current of the power cable (108) circuit can be detected in real time through the voltage detected from the shunt resistor (112), and the linearity characteristics of the current transformer (110) under test according to different magnitudes of current can be detected through the change in current value (e.g., slope) according to the detected value of the current transformer (110) under test and the change in current value (e.g., slope) calculated through the shunt resistor (112).

[0052] In addition, the measuring unit (116) can detect the output characteristics of the current transformer (110) by comparing the current magnitude of the power cable (108) circuit detected through the shunt resistor (112) with the output current magnitude of the current transformer (110) under test.

[0053] Meanwhile, the current transformer characteristic measurement system according to an embodiment of the present invention can generate a large current that can be input to a current transformer (110) under test by stepping up the electricity of a commercial power source (100) using a variable voltage regulator (102) as described above. In addition, the large current may be a current of a precisely adjusted magnitude, as the magnitude of which is controlled according to the variable voltage regulator (102). Therefore, the present invention can detect the characteristics of current transformers under test that detect the magnitude of various input currents without a current source for high-precision large currents.

[0054] In addition, the present invention has a configuration for measuring the current flowing through the power cable (108) circuit through the shunt resistor (112), that is, the input current of the current transformer (110) under test, as described above. Therefore, in the present invention, since a high-precision current transformer is not used to measure the input current of the current transformer (110) under test to generate a reference value, the characteristics of the current transformer (110) under test can be detected without distortion due to the characteristics of the current transformer.

[0055] Meanwhile, the variable voltage regulator (102) used in the present invention may be formed to vary the voltage of the commercial power supply (100) as described above. In this case, the current transformer characteristic measurement system according to the embodiment of the present invention may be equipped with a control motor (104) capable of controlling the variable voltage regulator (102) to vary the voltage of the commercial power supply (100) to a specific voltage.

[0056] Here, the measuring unit (116) can control the control motor (104) so ​​that a voltage is applied to the primary winding to induce a current in the secondary winding of the first current transformer (106) according to the magnitude of the input current of the current transformer (110) to be measured, based on the winding ratio of the first current transformer (106) and the resistance value of the power cable (108) circuit (e.g., the resistance value of the power cable (108) and the shunt resistor (112). In this case, information on the voltages of the primary windings of the first current transformer (106), each of which is of a different magnitude, to induce the required input current according to the input currents of the current transformer to be tested of different magnitudes can be stored in the memory (not shown) of the measuring unit (116). And when the input current of the current transformer (110) to be tested is determined, the measuring unit (116) detects a voltage corresponding to the determined input current from the memory of the measuring unit (116), and can control the control motor (104) so ​​that the variable voltage regulator (102) varies the voltage of the commercial power supply (100) according to the detected voltage.

[0057] In this case, according to the different input current magnitudes of the current transformers (110) for testing, the information on the voltage of the primary winding of the first current transformer (106), i.e., the output voltage of the variable voltage regulator (102), for forming the input current magnitude of the first current transformer (110) for testing based on the winding ratio of the first current transformer (106), may be obtained in advance through multiple experiments conducted in connection with the present invention.

[0058] Meanwhile, the variable voltage regulator (102) used in the present invention may be a slide-AC or sli-doc that has a core with a winding and is formed to vary the voltage according to the number of windings at a position corresponding to the position of the stop bar. In this case, the control motor (104) can be varied so that the position of the stop bar of the variable voltage regulator (102) changes.

[0059] In this case, the measuring unit (116) can control the control motor (104) to change the position of the stop bar of the variable voltage regulator (102) according to the input current magnitude of the current transformer (110) to be measured. To this end, the information on the voltages of the primary winding of the first current transformer (106) stored in the memory (not shown) of the measuring unit (116) may be information on the position of the stop bar (e.g., the rotation angle of the stop bar) for each different input current magnitude of the current transformer (110) to be tested. The measuring unit (116) can detect specific stop bar position information from the memory of the measuring unit (116) according to the input current magnitude of the current transformer (110) to be tested, and control the control motor (104) so ​​that the position of the stop bar is varied according to the detected stop bar position information.

[0060] In this case, the position information of the stop bar for forming an input current size of a current transformer (110) of a suitable size according to the input current sizes of the different current transformers (110) of the test, may be information obtained in advance through multiple experiments conducted in connection with the present invention.

[0061] Meanwhile, the measuring unit (116) can detect the magnitude of the input current of the current transformer (110) before detecting the characteristics of the current transformer (110) to be tested. For example, the magnitude of the input current of the current transformer (110) to be tested may be determined by a user of the current transformer characteristic measurement system according to an embodiment of the present invention, or may be detected through the result of the measuring unit (116) identifying the type of the current transformer (110) to be tested. In this case, the measuring unit (116) may establish a wired or wireless communication connection with the current transformer (110) to be tested, and may identify the type of the current transformer (110) to be tested through the unique information of the current transformer (110) received through the communication connection. Then, the magnitude of the input current of the current transformer (110) to be tested can be determined according to the identified type. Alternatively, the input current size of the current transformer (110) to be tested may be determined according to input current size information received directly from the current transformer (110) to be tested through the communication connection.

[0062] Meanwhile, FIG. 2 is a flowchart illustrating the operation process of detecting the characteristics of a current transformer (110) to be tested in a current transformer characteristic measurement system according to the embodiment of the present invention described above.

[0063] Referring to FIG. 2, the measuring unit (116) of the current transformer characteristic measuring system according to the embodiment of the present invention can first determine the input current of the current transformer (110) to be tested (S200). For example, the measuring unit (116) can establish a communication connection with the current transformer (110) to be tested and determine the magnitude of the input current of the current transformer (110) to be tested based on the result of identifying the type of the current transformer (110) to be tested according to the unique information of the current transformer (110) to be tested received from the current transformer (110), or based on the input current information received from the current transformer (110). Alternatively, the input current may be determined according to the magnitude of the current directly set by the user of the current transformer characteristic measuring system.

[0064] When the input current magnitude of the current transformer (110) under test is determined, the measuring unit (116) can determine an adjustment voltage corresponding to the determined input current from the memory (not shown) of the measuring unit (116) in which information on adjustment voltages corresponding to each of a plurality of input currents of different magnitudes is stored (S202). Here, the adjustment voltage may be an induced voltage that induces the voltage of the secondary winding of the first current transformer (106) to form the input current magnitude of the current transformer (110) based on the winding ratio of the first current transformer (106), that is, a voltage applied to the primary winding of the first current transformer (106).

[0065] To this end, information regarding the voltages of the primary winding of the first current transformer (106) for forming different input currents of the current transformer (110) to be tested, based on the winding ratio of the first current transformer (106) and the resistance value of the power cable (108) circuit, as described above, may be stored in the memory of the measurement unit (116). In this case, the voltage of the primary winding of the first current transformer (106) may be the output voltage of the variable voltage regulator (102) as a voltage applied from the variable voltage regulator (102), and information regarding the output voltages of a plurality of variable voltage regulators (102) for forming different input currents of the current transformer (110) to be tested may be calculated in advance or obtained in advance through a plurality of experiments performed in connection with the present invention and stored in the memory of the measurement unit (116).

[0066] And the measuring unit (116) can control the control motor (104) so ​​that the variable voltage regulator (102) varies the voltage of the commercial power supply (100) according to the adjustment voltage. Accordingly, the output voltage of the commercial power supply (100) can be varied to the adjustment voltage determined by the variable voltage regulator (102) (S204).

[0067] Here, the variable voltage regulator (102) can be connected to the primary winding of the first current transformer (106) core as described above. Accordingly, a voltage according to the adjustment voltage can be formed in the primary winding of the first current transformer (106) core.

[0068] Then, a voltage of a magnitude corresponding to the winding ratio of the first current transformer (106) can be induced in the secondary winding of the first current transformer (106). In this case, if the winding ratio is less than 1, a voltage greater than the adjustment voltage can be induced in the secondary winding. And, depending on the increased voltage, a current greater than the current of the commercial power supply (100) can be induced in the secondary winding. In this case, since a circuit formed by a power cable (108) is connected to the secondary winding, a current greater than the current of the commercial power supply (100) can flow in the circuit formed by the power cable (108).

[0069] Meanwhile, as described above, the adjustment voltage may be a voltage according to the information of the variable voltage regulator (102) output voltage stored in the memory of the measurement unit (116) in order to induce a secondary voltage that causes a current of a specific magnitude to be formed in the secondary winding of the first current transformer (106). In this case, the current of the specific magnitude may be an input current according to the type of the identified current transformer (110) to be tested, or an input current of the current transformer (110) to be tested that is received directly from the current transformer (110) to be tested or input by a user. Accordingly, the current transformer characteristic measurement system according to the embodiment of the present invention can form a circuit in which an accurately regulated current corresponding to the input current of the current transformer (110) to be tested flows using a commercial power supply (100).

[0070] Meanwhile, as described in FIG. 1 above, the power cable (108) can have both ends connected to a shunt resistor (112), and a circuit can be formed through the shunt resistor (112). Accordingly, a voltage corresponding to the current flowing through the power cable (108) can be formed in the shunt resistor (112). In addition, a detection unit (114) according to an embodiment of the present invention is connected to the shunt resistor (112) to detect the voltage formed in the shunt resistor (112).

[0071] In addition, as described above, the circuit formed by the power cable (108) (hereinafter referred to as the power cable (108) circuit) can be formed to penetrate the core of the current transformer (110) under test. Accordingly, the current transformer (110) under test can detect the current value flowing through the power cable (108) circuit. Furthermore, the detection unit (114) according to the embodiment of the present invention is connected to the current transformer (110) under test and can detect the current detection result of the current transformer (110) under test.

[0072] Here, the detection unit (114) can detect voltage from the shunt resistor (112) and detect current from the current transformer (110) under test. Accordingly, the detection unit (114) can simultaneously detect the voltage of the shunt resistor (112) and the current of the current transformer (110) under test, and can transmit the detected voltage and current together to the measurement unit (116).

[0073] Then, the measuring unit (116) can calculate the current of the power cable (108) circuit from the voltage of the shunt resistor (112). Accordingly, the measuring unit (116) can simultaneously measure the current of the power cable (108) circuit detected through the shunt resistor (112) and the output current of the current transformer (110) under test (S206). Then, the measuring unit (116) can measure the characteristics of the current transformer (110) under test by comparing the current of the power cable (108) circuit detected through the shunt resistor (112) with the output current of the current transformer (110) under test. In this case, the characteristics of the current transformer (110) under test that are measured may include the magnitude ratio characteristic of the output current relative to the input current, the linearity characteristic, and the phase delay characteristic (S208).

[0074] Here, the current of the power cable (108) circuit calculated through the shunt resistor (112) can be a reference value, and the output current value of the current transformer (110) under test can be a comparison value. That is, the reference value and the comparison value can be measured simultaneously.

[0075] As the reference value and the comparison value are measured simultaneously in this manner, the measuring unit (116) can compare the phase of the output current of the current transformer under test (110), which is detected simultaneously with the current detected through the shunt resistor (112) in step S208, in real time. Based on the comparison result, the phase delay characteristic of the output current of the current transformer under test (110) can be detected. In this case, since the reference value is calculated according to the voltage change calculated through the shunt resistor (112), a phase delay due to the characteristics of the current transformer may not occur during current measurement.

[0076] In addition, the measuring unit (116) can change the current flowing through the power cable (108) circuit by varying the voltage of the primary winding of the first current transformer (106) using the variable voltage regulator (102) in step S208. Then, the change in current of the power cable (108) circuit can be detected in real time through the voltage detected from the shunt resistor (112), and the output current value of the current transformer (110) under test can also change. Then, the measuring unit (116) can detect the linearity characteristics of the current transformer (110) under test by comparing the change in current value (e.g., slope) according to the detected value of the current transformer (110) under test with the change in current value (e.g., slope) calculated through the shunt resistor (112).

[0077] In addition, the current magnitude calculated according to the voltage magnitude calculated through the shunt resistor (112) may be the magnitude of the input current of the current transformer (110) under test. Accordingly, in step S208, the measuring unit (116) can detect the output characteristics of the current transformer (110) under test by comparing in real time the current magnitude of the power cable (108) circuit detected through the shunt resistor (112) and the magnitude of the output current of the current transformer (110) under test.

[0078] Meanwhile, Figure 3 is a block diagram illustrating an example of a conventional current transformer characteristic measurement system.

[0079] Referring to FIG. 3, a conventional current transformer characteristic measurement system may be configured to include a current (high current) output from a high-precision high-current source (300) capable of outputting an input current of a current transformer (110) to be tested, a current transformer (110) to be tested, and a high-precision current transformer (302) capable of detecting the high current. The system may also be configured to include a first current detection unit (310) for detecting the output value of the current transformer (110) to be tested, a second current detection unit (320) for detecting the output value of the high-precision current transformer (302), and a measurement unit (330) for measuring the characteristics of the current transformer (110) to be tested from the detection value of the first current detection unit (310) and the detection value of the second current detection unit (320).

[0080] In this case, the high-precision current transformer (302) can detect the current output from the high-precision high-current current source (300) as a reference value for comparing the output value of the current transformer (110) under test. The measuring unit (330) can measure the output magnitude characteristics, phase delay characteristics, and linearity characteristics of the current transformer (110) under test by analyzing the detection value of the current transformer (110) under test based on the detection value of the high-current detected by the high-precision current transformer (302), that is, the input current of the current transformer (110) under test.

[0081] However, as described above, a conventional current transformer characteristic measurement system uses the detection value of another current transformer, namely a high-precision current transformer (302), to detect a reference value for comparing the output value of the current transformer (110) to be tested. However, in the case of a current transformer, no matter how high the precision, it has inherent output magnitude characteristics, phase delay characteristics, or linearity characteristics, so there is a problem that an error due to the characteristics of the high-precision current transformer (302) is included in the reference value.

[0082] In addition, as shown in FIG. 3, a conventional current transformer characteristic measurement system is configured to receive detection values ​​from each of the current transformer (110) to be tested and the high-precision current transformer (302), and has a configuration in which a plurality of current detection units (first and second current detection units (310, 312)) each receive detection values ​​from the current transformer to which they are connected and transmit them to the measurement unit (116). Accordingly, the measurement unit (116) is formed to receive detection values ​​from each of the plurality of separate current detection units, and there is a problem in that it is difficult to guarantee the simultaneity of the detection values ​​received from the plurality of detection units due to differences in communication protocols, performance differences of each current detection unit (114), or communication environments.

[0083] In addition, the aforementioned conventional current transformer characteristic measurement system requires a high-precision current source capable of outputting a large current, but there is a problem in that such a large current source is very expensive.

[0084] In contrast, the present invention has the advantage of being able to form the input current of the current transformer (110) under test, which is a required high current, by using a commercial power source (100) as described above. Accordingly, there is an advantage of being able to measure the characteristics of the current transformer (110) under test at a relatively low cost compared to the conventional current transformer characteristic measurement system.

[0085] In addition, the present invention can detect the input current of the current transformer (110) under test through a shunt resistor (112) that forms a power cable (108) circuit as shown in FIG. 1, instead of the high-precision current transformer (302) having unique characteristics, thereby detecting the reference value, i.e., the input current of the current transformer (110) under test, without the high-precision current transformer (302). Therefore, the input current of the current transformer (110) under test can be detected without reflecting the current characteristics of the high-precision current transformer (302).

[0086] In addition, since the present invention detects the input current of the current transformer (11) under test using the voltage detected through the shunt resistor (112), the input current (voltage of the shunt resistor (112)) of the current transformer (110) under test and the output current of the current transformer (110) under test can be simultaneously detected through a single detection unit (114). That is, the simultaneity of detection of the input current and output current of the current transformer (110) under test can be satisfied.

[0087] Meanwhile, although specific embodiments have been described in the above description of the present invention, various modifications may be made without departing from the scope of the present invention. In particular, in the embodiments of the present invention, a slide-AC or sli-dac is used as an example of a variable voltage regulator (102), but it is obvious that the present invention is not limited thereto. That is, it is obvious that any other type of variable voltage regulator may be used.

[0088] Furthermore, the above description used the example of forming the input current of the current transformer under test using the current output from a commercial power source. However, the commercial power source is a power source that outputs a current having a preset voltage, and it goes without saying that it can be replaced with any other power source that outputs a current having a fixed voltage.

[0089] The present invention described above can be implemented as computer-readable code on a medium on which a program is recorded. A computer-readable medium includes all types of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable media include HDD (Hard Disk Drive), SSD (Solid State Disk), SSD (Silicon Disk Drive), ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage device, etc., and also include implementation in the form of a carrier wave (e.g., transmission over the Internet).

[0090] Additionally, the computer may include a measurement unit (116) of a current transformer characteristic system. Accordingly, the above detailed description should not be interpreted restrictively in all respects and should be considered exemplary. The scope of the invention should be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the invention are included within the scope of the invention.

Claims

1. A power source that outputs a current having a voltage of a preset size; Current transformer (CT) to be tested for measuring characteristics; A first current transformer comprising a core on which a primary winding and a secondary winding are wound, respectively; A voltage regulator that varies the voltage applied from the above power source to another voltage and applies the varied voltage to the primary winding; A power cable formed to penetrate the core of the current transformer under test and connected to the secondary winding, so as to allow a current corresponding to the voltage of the secondary winding induced according to the voltage applied to the primary winding to flow; A shunt resistor that connects both ends of the power cable to form a circuit made of the power cable; A detection unit that simultaneously detects the voltage of the shunt resistor and the output current of the current transformer under test; and, A current transformer characteristic measurement system characterized by including a measurement unit that receives together the voltage value of the shunt resistor and the output current value of the current transformer under test from the detection unit, and measures the characteristics of the current transformer under test by comparing the current value calculated from the voltage value of the shunt resistor with the output current value of the current transformer under test.

2. In paragraph 1, the primary winding and the secondary winding of the first current transformer are, A current transformer characteristic measurement system characterized by being wound on the core of the first current transformer such that the winding ratio becomes less than 1, and a voltage greater than the voltage applied from the voltage regulator is induced in the secondary winding.

3. In Paragraph 1, The above voltage regulator is, It is a variable voltage regulator capable of varying the input voltage to any one of a plurality of different set voltages, and The above measuring unit is, A current transformer characteristic measurement system characterized by controlling the variable voltage regulator to vary the voltage of the power source to a specific size set voltage corresponding to the input current size of the current transformer under test.

4. In paragraph 3, the above measuring unit is, A current transformer characteristic measurement system characterized by determining the set voltage based on the resistance values ​​of the power cable and shunt resistor and the winding ratio of the first current transformer.

5. In paragraph 3, the above measuring unit is, The device further comprises a memory for storing output voltage magnitude information of different variable voltage regulators corresponding to each of the input current magnitudes of multiple different current transformers under test, and A current transformer characteristic measurement system characterized by determining the magnitude of the output voltage of the variable voltage regulator applied to the primary winding based on the identification result of the current transformer under test or input current information received from the current transformer under test.

6. In Paragraph 3, The above variable voltage regulator is, It has a core with wound coils and is formed to vary the voltage according to the number of windings at a position corresponding to the position of the stop bar, and The above current transformer characteristic measurement system is, A current transformer characteristic measurement system characterized by further including a control motor that changes the position of the stop bar according to the control of the measurement unit based on the magnitude of the output voltage of the variable voltage regulator determined above.

7. In paragraph 1, the above power source is, A current transformer characteristic measurement system characterized by being a commercial power source.

8. In paragraph 1, the secondary winding is, A current transformer characteristic measurement system characterized by being formed as part of the above power cable.

9. In paragraph 1, the measuring unit is, Based on the resistance value of the power cable circuit formed by the power cable and the shunt resistor, the input current value of the current transformer under test is calculated from the voltage of the shunt resistor, and A current transformer characteristic measurement system characterized by comparing the calculated input current value and the output current value of the current transformer under test in real time to measure the linearity characteristics of the current transformer under test and the output characteristics of the output current with respect to the input current.

10. In paragraph 1, the measuring unit is, A current transformer characteristic measurement system characterized by measuring the phase delay characteristic of the current transformer under test by comparing in real time the phase change of the input current of the current transformer under test calculated from the change in the voltage value of the shunt resistor and the phase change according to the output current of the current transformer under test.

11. A step of determining a set voltage according to the magnitude of the input current of the current transformer under test; A step of varying the output voltage of a power supply that outputs a current having a preset voltage according to a determined set voltage; A step of applying a variable voltage to the primary winding of a first current transformer to induce a voltage in the secondary winding of the first current transformer according to the winding ratio of the first current transformer; A step of connecting to the secondary winding and forming a circuit by connecting both ends to a shunt resistor, and simultaneously detecting the voltage of a power cable formed to penetrate the core of the current transformer under test through the shunt resistor, and detecting the output current of the current transformer under test by detecting the current of the power cable penetrating the core; A step of calculating a current according to the voltage of the above shunt resistor; and, A control method for a current transformer characteristic measurement system, characterized by including the step of measuring the characteristics of the current transformer under test by comparing in real time the output current of the current transformer under test detected simultaneously with the voltage of the shunt resistor and the current calculated according to the voltage of the shunt resistor.

12. In paragraph 11, the step of determining the set voltage is, A step of identifying the type of the current transformer to be tested above; A step of determining an input current according to the type of identified current transformer under test; and, A control method for a current transformer characteristic measurement system, characterized by including the step of detecting one of a plurality of set voltages corresponding to the determined input current among a plurality of set voltages for forming different input currents of a current transformer under test based on the winding ratio of the first current transformer and the resistance value of the circuit formed by the power cable.

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