Method, device and system for detecting tail current in a current transformer
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ABB (SCHWEIZ) AG
- Filing Date
- 2026-02-04
- Publication Date
- 2026-08-07
Smart Images
Figure CN122525472A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to electrical engineering. In particular, this invention relates to a method and apparatus for detecting tail current in current transformers (converters, CTs). Background Technology
[0002] A current transformer is a device that measures the current flowing through a conductor or power system. In a normal current transformer (i.e., a current transformer without an air gap), under short-circuit conditions, the short-circuit current can reach tens or even hundreds of times the rated current of the current transformer, leading to saturation. In this situation, the current transformer cannot correctly transmit the primary current to the secondary side, resulting in malfunctions or misoperations of protection devices and significant errors in fault location equipment. To overcome this, manufacturers create a small air gap in the core of the current transformer. Air-gap current transformers ensure that the errors are within the allowable range of relay protection in both steady-state and transient conditions.
[0003] However, in air-gap current transformers, when the core flux decays to its final value after a fault interruption, the energy stored in the magnetic circuit must be dissipated in the secondary circuit, resulting in a prolonged unidirectional discharge. Because the flux variation required to reach the residual magnetism level is large for air-gap current transformers, the discharge voltage is high, leading to a very long decay time. This causes a current tailing phenomenon in the secondary current of the current transformer, known as the current tail (tail current). Due to the very long decay time, this may not provide an indication that the circuit breaker has opened. In other words, the decaying current after a fault interruption may be delayed in indicating that the circuit breaker has opened. This can lead to maloperation of the circuit breaker fault protection. In other words, the current tail can affect the operation of the circuit breaker fault protection, potentially leading to false alarms. Therefore, it is necessary to mitigate the problems caused by the current tail. Thus, it is necessary to detect the current tail in the current transformer to avoid false alarms.
[0004] The information disclosed in this background section is intended only to enhance the understanding of the general background of the invention and should not be construed as an admission or implication in any way that the information constitutes prior art known to those skilled in the art. Summary of the Invention
[0005] This invention discloses a method for detecting the tail current in a current transformer (CT). The method includes acquiring the real-time current value of the current flowing in the secondary (secondary) side of the current transformer. Furthermore, the method includes determining the instantaneous time constant (K). t The instantaneous time constant (K) t ) is the instantaneous current value (I) at a specific time (t). t) and the current value (I) at the previous time (t-1). t-1 The proportion of ). Subsequently, the method includes determining the deviation value (ΔK) by using a pair of continuous time constants. t The continuous time constant is the instantaneous time constant (K) at a specific time (t). t ) and the time constant (K) at the previous time (t-1) t-1 Furthermore, the method includes setting the deviation value (ΔK) as... t The deviation value (ΔK) is determined by comparing it with a predetermined deviation threshold. t Whether the deviation value (ΔK) is less than the predetermined deviation threshold. Subsequently, based on the comparison result, the method includes performing one of the following: whenever the deviation value (ΔK) is less than the predetermined deviation threshold in a consecutive time instance. t When the deviation value (ΔK) is less than a predetermined deviation threshold, the counter is incremented (the value increases); and when the deviation value (ΔK) is less than a predetermined deviation threshold, the counter is incremented (the value increases). t When the counter exceeds the predetermined deviation threshold, the counter is reset to zero. Finally, the method includes detecting the presence of tail current in the current transformer when the counter exceeds the predetermined counting threshold.
[0006] Furthermore, this paper discloses a tail current detection unit for detecting tail current in a current transformer. The tail current detection unit includes a processor and a memory. The memory is communicatively coupled to the processor and stores processor-executable instructions that, upon execution, cause the processor to acquire a real-time current value of the current flowing in the secondary side of the current transformer. Additionally, the processor determines an instantaneous time constant (K). t The instantaneous time constant (K) t ) is the instantaneous current value (I) at a specific time (t). t ) and the current value (I) at the previous time (t-1). t-1 The processor then determines the deviation value (ΔK) using a pair of consecutive time constants. t The continuous time constant is the instantaneous time constant (K) at a specific time (t). t ) and the time constant (K) at the previous time (t-1) t-1 Furthermore, the processor will use the aforementioned deviation value (ΔK) t The deviation value (ΔK) is determined by comparing it with a predetermined deviation threshold. t Whether the deviation value (ΔK) is less than the predetermined deviation threshold. Thereafter, based on the comparison result, the processor performs one of the following: whenever the deviation value (ΔK) is within a consecutive time frame... t When the deviation value (ΔK) is less than a predetermined deviation threshold, the counter is incremented; and when the deviation value (ΔK) is less than a predetermined deviation threshold, the counter is incremented. tWhen the count exceeds a predetermined deviation threshold, the counter is reset to zero. Finally, when the counter exceeds a predetermined counting threshold, the processor detects the presence of tail current in the current transformer.
[0007] Furthermore, this paper discloses an intelligent electronic device (IED) for detecting the tail current in a current transformer. The IED includes an analog-to-digital converter (ADC), a system measurement device, one or more protection functions (protection function devices), and a tail current detection unit. The tail current detection unit is used to acquire the real-time current value of the current flowing in the secondary side of the current transformer. This real-time current value is a measured value of the current. Furthermore, the tail current detection unit determines the instantaneous time constant (K). t The instantaneous time constant (K) t ) is the instantaneous current value (I) at a specific time (t). t ) and the current value (I) at the previous time (t-1). t-1 The ratio of ) is then determined by the tail current detection unit using a pair of continuous time constants to determine the deviation value (ΔK). t The continuous time constant is the instantaneous time constant (K) at a specific time (t). t ) and the time constant (K) at the previous time (t-1) t-1 Furthermore, the tail current detection unit will detect the deviation value (ΔK). t The deviation value (ΔK) is compared with a predetermined deviation threshold to determine the deviation value. t Whether the deviation value (ΔK) is less than the predetermined deviation threshold. Thereafter, based on the comparison, the tail current detection unit performs one of the following: whenever the deviation value (ΔK) is greater than the predetermined deviation threshold in a consecutive time interval... t When the deviation value (ΔK) is less than a predetermined deviation threshold, the counter is incremented; and when the deviation value (ΔK) is less than a predetermined deviation threshold, the counter is incremented. t When the value exceeds the predetermined deviation threshold, the counter is reset to zero. Finally, when the counter exceeds the predetermined counting threshold, the tail current detection unit detects the presence of tail current in the current transformer.
[0008] The above description of the invention is illustrative only and is not intended to limit the scope in any way. Other aspects, embodiments, and features will become apparent from the accompanying drawings and the following detailed description, in addition to the illustrative aspects, embodiments, and features described above. Attached Figure Description
[0009] The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, explain the principles of the invention. In the drawings, the leftmost numeral of the reference numeral identifies the drawing in which that numeral first appears. The same numerals are used throughout the drawings to indicate the same features and components. Some embodiments of the system and / or method according to the invention will now be described by way of example only and with reference to the accompanying drawings, in which:
[0010] Figure 1A An exemplary architecture for implementing a technique for detecting tail current in a current transformer is shown according to some embodiments of the present invention;
[0011] Figure 1B An exemplary architecture of a smart electronic device (IED) including a tail current detection unit is shown according to some embodiments of the present invention;
[0012] Figure 1C An exemplary architecture including a tail current detection unit, switch and circuit breaker fault protection, according to some embodiments of the present invention, is shown;
[0013] Figure 2 Exemplary graphs according to some embodiments of the present invention are shown, illustrating current, instantaneous time constant (K). t ), deviation value (ΔK) t ) and current tail indicator;
[0014] Figures 3A-3D Exemplary graphs are shown according to some embodiments of the present invention, which compare the issuance of reclosing / rear closing signals in existing embodiments and embodiments of the present invention;
[0015] Figure 4 A detailed block diagram of a tail current detection unit for detecting tail current in a current transformer, according to some embodiments of the present invention, is shown; and
[0016] Figure 5 A flowchart illustrating a method for detecting tail current in a current transformer is shown according to some embodiments of the present invention.
[0017] Those skilled in the art will understand that any block diagram herein represents a conceptual diagram of an illustrative system for implementing the principles of the invention. Similarly, it will be understood that any flowchart, program block diagram, state transition diagram, pseudocode, etc., represents various processes that can be presented substantially in a computer-readable medium and executed by a computer or processor, whether or not such computer or processor is explicitly shown. Detailed Implementation
[0018] In this document, the word "exemplary" is used to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the invention described herein as "exemplary" is not necessarily to be construed as being more preferred or advantageous than other embodiments.
[0019] While various modifications and substitutions can be made to the present invention, specific embodiments thereof have been shown by way of example in the accompanying drawings and will be described in detail below. However, it should be understood that this is not intended to limit the invention to the specific forms disclosed, but rather, the invention is intended to cover all modifications, equivalents, and substitutions falling within the scope of the invention.
[0020] The terms “comprising,” “including,” “containing,” or any other variations thereof are intended to cover non-exclusive inclusion, such that an apparatus, device, or method that comprises a list of components or steps includes not only those components or steps but may also include other components or steps not expressly listed or inherent to such an apparatus, device, or method. In other words, without further limitation, the presence of one or more elements preceding “comprising…a” in a system or device does not exclude the presence of other elements or additional elements in the system or method.
[0021] As outlined in the background section, the instantaneous current in the excitation branch and secondary winding of a current transformer may not be zero at the moment the primary device is disconnected. The energy stored in the inductor will be slowly released through the secondary circuit formed by the resistor and inductor. This causes a current tailing phenomenon in the current transformer secondary circuit, known as current tailing. Due to the large inductance, the damping time constant of the secondary circuit is large, typically from hundreds of milliseconds to several seconds. The tail current of the current transformer mainly consists of a damped aperiodic component. Since the decaying current after a fault interruption may be delayed when the circuit breaker is indicated to open, this may lead to erroneous operation that disrupts the entire power system. This invention proposes a method and apparatus for detecting the tail current in a current transformer to avoid false alarms.
[0022] According to the present invention, an intelligent electronic device (IED) for detecting the tail current in a current transformer is disclosed. The IED includes an analog-to-digital converter (ADC), system measurement, one or more protection functions (protection function devices), and a tail current detection unit. The tail current detection unit can acquire the real-time current value of the current flowing in the secondary side of the current transformer. This real-time current value is a measured value of the current. After acquiring the real-time current value, the tail current detection unit can determine the instantaneous time constant (K). t The instantaneous time constant (K) t ) can be the instantaneous current value (I) at a specific time (t). t ) and the current value (I) at the previous time (t-1). t-1 The ratio of ) . Afterwards, the tail current detection unit can detect the deviation value (ΔK)t The deviation value (ΔK) is compared with a predetermined deviation threshold to determine the deviation value. t Whether the deviation value (ΔK) is less than the predetermined deviation threshold. Based on the comparison, the tail current detection unit may perform one of the following: whenever the deviation value (ΔK) is less than the predetermined deviation threshold in a continuous sequence of time. t When the deviation value (ΔK) is less than a predetermined deviation threshold, the counter is incremented; and when the deviation value (ΔK) is less than a predetermined deviation threshold, the counter is incremented. t When the deviation exceeds the predetermined threshold, the counter is reset to zero. Finally, when the counter exceeds the predetermined counting threshold, the tail current detection unit can detect the presence of the tail current in the current transformer. The invention also detects the end of the tail current, which will be discussed in detail below.
[0023] In the following detailed description of embodiments of the invention, reference is made to the accompanying drawings, which form a part therein, and specific embodiments in which the invention may be practiced are illustrated by way of illustration. These embodiments have been described in sufficient detail to enable those skilled in the art to practice the invention, and it should be understood that other embodiments may be utilized and changes may be made without departing from the scope of the invention. Therefore, the following description should not be construed as limiting.
[0024] Figure 1A An exemplary architecture 100 for implementing techniques for detecting tail current in a current transformer is shown according to some embodiments of the present disclosure.
[0025] The exemplary architecture 100 includes an intelligent electronic device (IED) 101, a current transformer (CT) 103, and a power system 105. In one embodiment, the IED 101 may be electrically coupled to the CT 103. In one embodiment, the CT 103 may be configured to measure the current flowing through the power system 105. In one embodiment, the power system 105 may be a network of electrical components designed to generate, transmit, and distribute electrical energy. In some embodiments, the power system 105 may be an electrical system or a combination of electrical systems. As examples, the power system 105 may be, but is not limited to, a power grid, a grid-connected solar power system, or a hybrid power system. In one embodiment, the CT 103 may be electrically coupled to the power system 105 to obtain a real-time current value of the current flowing through the power system 105.
[0026] Figure 1B An exemplary architecture of IED 101 is shown. IED 101, alternatively referred to as a relay, can detect, monitor, and control a power system. IED 101 issues a TRIP command to a circuit breaker upon detecting a fault condition. IED 101 may include, but is not limited to, a tail current detection unit 111, an analog-to-digital converter (ADC) 113, a system measurement device 115, and one or more protection functions (protection function devices) 117. NThe ADC 113 can be used to convert analog current signals from the CT 103 into digital values. The system measurement device 115 can be used for the protection of the power system 105, the monitoring and control of the power system 105, and the data logging and analysis in the IED 101. One or more protection functions 117 N This device can be used for the protection of a power system 105 associated with the IED 101. In one embodiment, the IED 101 can be configured to use a tail current detection unit 111 to detect the tail current in the CT 103. The IED 101 can be used as a stand-alone system or as an application performing the actions disclosed in this disclosure.
[0027] In one embodiment, the tail current detection unit 111 can be configured to acquire a real-time current value of the current flowing in the secondary side of the CT 103. This real-time current value is a measurement of the current. In one embodiment, the secondary side of the CT 103 provides a measurement of the real-time current flowing in the power system 105. In one embodiment, the tail current detection unit 111 can be configured within one or more protection functions 117 of the IED 101. N Real-time measurement results are acquired when the trip signal is activated. IED 101 can be electrically coupled to CT 103 (e.g., Figure 1B (As shown). In one embodiment, the one or more protection functions 117 N It can be used to protect the power system 105 associated with IED 101. As an example, the one or more protection functions 117 N This may include, but is not limited to, overcurrent protection, ground fault protection, differential protection, distance protection, voltage protection, frequency protection, and power swing protection. In one embodiment, the activation of a trip signal may indicate an abnormal condition or fault that may need to be addressed. Figure 2 An exemplary graph is shown. Figure 2 Graph 201 shows the real-time current value flowing in the secondary side of CT 103. The current tail, i.e., the decaying waveform similar to the tail, is shown in... Figure 2 The Chinese character is represented by 201A.
[0028] return Figure 1A When acquiring real-time current values, the tail current detection unit 111 can determine the instantaneous time constant (K). t The instantaneous time constant (K) t ) can be the instantaneous current value (I) at a specific time (t). t ) and the current value (I) at the previous time (t-1). t-1The ratio of the time difference between the previous time (t-1) and the current time (t). In one embodiment, the previous time (t-1) can be a time preceding the current time (t). As an example, the time difference between the current time (t) and the previous time (t-1) can range from 500 microseconds to 1.5 milliseconds. The value of this time difference should not be interpreted as a limitation, and the value of this time difference can vary. As an example, the instantaneous time constant (K) t The instantaneous time constant (K) can be the ratio of the current value at 10 milliseconds to the current value at 9 milliseconds. As an example, Equation 1 below shows the instantaneous time constant (K). t ):
[0029] K t = I t / I t-1 (1)
[0030] Equation 1 provided above is intended as an illustrative example and should not be construed as a limitation of the invention. Figure 2 Graph 203 illustrates the instantaneous time constant determined using the current value. In one embodiment, the instantaneous time constant (K) can be determined continuously. t These values can be used for further determination.
[0031] In one embodiment, when determining the instantaneous time constant (K) t When the tail current detection unit 111 is configured to determine the deviation value (ΔK) by using a pair of continuous time constants, the tail current detection unit 111 can be configured to determine the deviation value (ΔK). t The continuous time constant can be the instantaneous time constant (K) at a specific time (t). t ) and the time constant (K) at the previous time (t-1) t-1 Similar to determining the instantaneous time constant (K). t ), deviation value (ΔK) t The instantaneous time constant (K) at a specific time (t) can be used. t ) and the time constant (K) at the previous time (t-1) t-1 The difference between them is used to determine this. In one embodiment, this is determined by the instantaneous time constant (K). t The value of ) is continuously determined, and the deviation value (ΔK) t The instantaneous time constant (K) at a specific time (t) can be used. t ) and the time constant (K) of the previous time (t-1) t-1 The difference between ΔK and ΔK is used to determine the deviation value. As an example, Equation 2 below shows the deviation value (ΔK). t ):
[0032] ΔK t = | K t - K t-1 |(2)
[0033] Equation 2 provided above is intended as an illustrative example and should not be construed as a limitation of the invention. Figure 2 Figure 205 shows the deviation value (ΔK) determined using the instantaneous time constant value. t In one embodiment, the deviation value (ΔK) t The instantaneous time constant (K) can be continuously determined because these values can be used for further determination. In one embodiment, the real-time current value can be based on the variation of the power system 105, thus the instantaneous time constant (K) can be determined. t The instantaneous time constant (K) can also change. t ) can change, therefore based on the instantaneous time constant (K) t Determining the tail of the current can be difficult because the constant value indicating the tail of the current may not be defined. For example, refer to... Figure 2 The curve in Figure 203 shows the instantaneous time constant (K) at the tail of the current. t The value is "1", meaning that the straight line 203A, representing the time constant of the current tail, is constant at the value "1". In other words, the normal operation of CT 103 can be identified based on the sine wave in the figure. Since the current tail is formed by the decay of the current in the secondary side of CT 103, this can be identified based on the decay line reflecting the continuous decrease over time.
[0034] To overcome the challenges encountered when detecting the tail of the current, the tail current detection unit 111 can determine the deviation value (ΔK). t This can help indicate when the deviation value (ΔK) is reached. t It may be closer to the current tail at zero because the deviation value (ΔK) t ) is based on the instantaneous time constant (K) at a specific time (t). t ) and the time constant (K) at the previous time (t-1) t-1 The difference between these time constants is used to determine the value. These time constants may be approximately the same, resulting in a deviation value close to zero. (Reference) Figure 2 The curve in Figure 207 shows that the current tail is closer to zero, which simplifies the detection process of the current tail.
[0035] In one embodiment, when determining the deviation value (ΔK) t When the tail current detection unit 111 is configured to detect the deviation value (ΔK), the tail current detection unit 111 can be configured to detect the deviation value (ΔK). t The deviation value (ΔK) is compared with a predetermined deviation threshold to determine the deviation value. t Whether it is less than the predetermined deviation threshold. As an example, the predetermined deviation threshold could be 0.02 per unit.
[0036] In one embodiment, based on the comparison, whenever the deviation value (ΔK) occurs in consecutive moments... t If the deviation value (ΔK) is less than a predetermined deviation threshold, the tail current detection unit 111 can increment the counter. Otherwise, when the deviation value (ΔK) is less than a predetermined deviation threshold, the tail current detection unit 111 can increment the counter. t If the deviation value (ΔK) is greater than a predetermined deviation threshold, the tail current detection unit 111 can reset the counter to zero. As an example, consider an exemplary scenario where the deviation value (ΔK) is greater than a predetermined deviation threshold. t For two consecutive moments, the deviation is less than the predetermined deviation threshold; however, at the third moment, the deviation value (ΔK) is higher. t If the deviation value (ΔK) exceeds a predetermined deviation threshold, the counter is reset to zero. In other words, whenever the deviation value (ΔK) exceeds the predetermined deviation threshold, the counter is reset to zero. t When the deviation value (ΔK) exceeds a predetermined deviation threshold, the counter is reset to zero. t If the deviation is less than a predetermined threshold, the counter is reset to zero to restart the counter. This process is performed continuously based on comparisons.
[0037] In one embodiment, the tail current detection unit 111 can detect the presence of a tail current in the CT 103 when the counter exceeds a predetermined counting threshold. As an example, the predetermined counting threshold may be, but is not limited to, eight. In some embodiments, when the deviation value (ΔK) t The presence of tail current in CT 103 can be detected if the current is less than a predetermined deviation threshold within a predetermined duration. As an example, the predetermined duration can be, but is not limited to, 5 milliseconds. Figure 2 As shown in graph 207, a change from "0" to "1" indicates the detection of a current tail. In one embodiment, upon detecting a current tail, the tail current detection unit 111 can activate an output signal to indicate the presence of a tail current. This output signal enables switch 121 to provide a value of "zero" to one or more components, instead of providing information about the current flowing in the secondary side of CT 103. Providing a "zero" value avoids generating false alarms. If an actual current flowing in the secondary side of the CT is provided, a false alarm will be generated because one or more components will sense the decaying current and may generate an alarm.
[0038] refer to Figure 1CThe illustration shows an exemplary diagram of IED 101, which includes a tail current detection unit 111, a switch 121, and a circuit breaker fault protection device 123. In one embodiment, switch 121 may be a logic component of IED 101 that can be activated when a current tail is detected to provide a value of "zero" to one or more components on the secondary side of CT 103. In other words, ideally, the one or more components could use information about the current flowing in the secondary side of CT 103. When a current tail is detected, the output signal of switch 121 can be activated to provide "zero" (e.g., ...). Figure 1C (as shown), instead of the actual current flowing in the secondary side of CT103 (i.e., tail current), to avoid generating false alarms.
[0039] In one embodiment, the tail current detection unit 111 can determine the end of the current tail by determining the root mean square (RMS) value of the current flowing in the secondary side of the CT 103. Furthermore, the tail current detection unit 111 can determine the end of the tail current in the CT 103 when the RMS value of the current is substantially zero. The RMS can be determined using known methods. In one embodiment, upon detecting the end of the current tail, the tail current detection unit 111 can reset a counter value to zero. Additionally, the tail current detection unit 111 can deactivate (disable, invalidate) the output signal upon detecting the end of the tail current. Deactivation of the output signal can be achieved by stopping the supply of "zero" to one or more components that use information about the current flowing in the secondary side of the CT 103. When the output signal is deactivated, the current flowing in the secondary side of the CT 103 can be supplied to one or more components that use information about the current flowing in the secondary side of the CT 103.
[0040] refer to Figures 3A-3DThe graphs shown, such as graphs 301, 321, 341, and 361, use 301A, 321A, 341A, and 361A to represent the current tail, respectively. The current tail can also be shown in graphs 303, 323, 343, and 363. Graphs 301-305, 321-325, 341-345, and 361-365 relate to undetected tail current. Graphs 307-311, 327-331, 347-351, and 367-371 are related to the present invention. In existing implementations, since the current remains on the secondary side of CT 103 (refer to graphs 305, 325, 345, and 365) and it passes through one or more components using information about the current flowing in the secondary side of the current transformer, information about reclosing or backup closing is issued. However, when using the tail current detection unit 111, providing a "zero" value (i.e., the tail of the current is truncated (refer to curves 309, 329, 349 and 369)) to one or more components that use information about the current flowing in the secondary side of the current transformer will prevent the issuance of reclosing or backup closing that may generate false alarms (refer to curves 311, 331, 351 and 371).
[0041] Figure 4 A detailed block diagram of a tail current detection unit 111 for detecting tail current in a current transformer (CT) 103 according to some embodiments of the present invention is shown.
[0042] In some implementations, the tail current detection unit 111 may include an I / O interface 401, a processor 403, and a memory 405. In one embodiment, the memory 405 may be communicatively coupled to the processor 403. The processor 403 may be configured to use data 407 and one or more modules 409 of the tail current detection unit 111 to perform one or more functions of the tail current detection unit 111, thereby detecting the tail current in the current transformer (CT) 103. In one embodiment, the memory 405 may store the data 407.
[0043] In one embodiment, the data 407 stored in memory 405 may include, but is not limited to, current data 411, instantaneous time constant 413, deviation value 415, and other data 417. In some embodiments, data 407 may be stored in memory 405 in the form of various data structures. Additionally, data 407 may be organized using a data model, such as a relational or hierarchical data model. The other data 417 may include various temporary data and files generated by one or more modules 409.
[0044] In one embodiment, current data 411 can indicate the real-time current value of the current flowing in the secondary side of CT 103. In one embodiment, current data 411 can be obtained using a current sensor configured on the secondary side of CT 103. In some embodiments, current data 411 can be determined based on the current values, voltage values, and number of windings on the primary and secondary sides of CT 103. Current data 411 can be used to detect current tails.
[0045] In one embodiment, the instantaneous time constant 413 may be based on the instantaneous current value (I) at a specific time (t). t ) and the current value (I) at the previous time (t-1) t-1 The instantaneous time constant 413 is determined by the proportion of the current data 411. In other words, the instantaneous time constant 413 can be determined using the current data 411. The instantaneous time constant 413 can be determined continuously because successive values of the instantaneous time constant 413 can be used to determine the deviation value 415. The instantaneous time constant 413 can be determined using Equation 1.
[0046] In one embodiment, the deviation value 415 can be a value determined using a pair of continuous time constants. In one embodiment, the pair of continuous time constants can be an instantaneous time constant (K) at a specific time (t). t ) and the time constant (K) at the previous time (t-1) t-1 In other words, the deviation value 415 can be determined using the instantaneous time constant 413. The deviation value (ΔK) t The instantaneous time constant (K) at a specific time (t) can be used. t ) and the time constant (K) at the previous time (t-1) t-1 The difference between the two values is used to determine the deviation. Since the deviation value 415 can be used to detect the tail of the current, the deviation value 415 can be determined continuously. The deviation value 415 can be determined using Equation 2.
[0047] In one embodiment, data 407 may be processed by one or more modules 409 of the tail current detection unit 111. In some embodiments, the one or more modules 409 may be communicatively coupled to the processor 403 to perform one or more functions of the tail current detection unit 111. In one embodiment, the one or more modules 409 may include, but are not limited to, an acquisition module 419, a determination module 421, a comparison module 423, an execution module 425, a detection module 427, and other modules 429.
[0048] As used herein, the term "module" can refer to an application-specific integrated circuit (ASIC), electronic circuitry, a hardware processor (shared, dedicated, or grouped) and memory executing one or more software or firmware programs, combinational logic circuitry, and / or other suitable components providing the aforementioned functionality. In one embodiment, each of the one or more modules 409 may be configured as an independent hardware computing unit. In one embodiment, the other modules 429 may be used to perform a variety of functions on the tail current detection unit 111. It will be understood that such one or more modules 409 may be represented by a single module or a combination of different modules.
[0049] In one embodiment, the acquisition module 419 may be configured to acquire a real-time current value of the current flowing in the secondary side of the CT 103. This real-time current value is a measured value of the current.
[0050] In one embodiment, the determining module 421 can be configured to determine the instantaneous time constant (K). t The instantaneous time constant (K) t ) can be the instantaneous current value (I) at a specific time (t). t ) and the current value (I) at the previous time (t-1). t-1 ) proportion.
[0051] In one embodiment, the determining module 421 can be configured to determine the deviation value (ΔK) using a pair of continuous time constants. t The continuous time constant can be the instantaneous time constant (K) at a specific time (t). t ) and the time constant (K) at the previous time (t-1) t-1 ).
[0052] In one embodiment, the comparison module 423 can be configured to compare the deviation value (ΔK) t The deviation value (ΔK) is compared with a predetermined deviation threshold to determine the deviation value. t Whether it is less than the predetermined deviation threshold.
[0053] In one embodiment, the execution module 425 may be configured to perform one of the following: in a continuous sequence of time, each time the deviation value (ΔK) is reached... t The counter increments when the deviation value (ΔK) is less than a predetermined deviation threshold; and when the deviation value (ΔK) is less than a predetermined deviation threshold, the counter increments. t When the deviation exceeds the predetermined deviation threshold, the counter is reset to zero.
[0054] In one embodiment, the detection module 427 can be configured to detect the presence of a tail current in the CT 103 when a counter exceeds a predetermined counting threshold. In one embodiment, when the presence of a tail current in the CT 103 is detected, an output signal can be activated to indicate the presence of the tail current. This output signal enables the switch 121 to provide a value of "zero" to one or more components using information about the current flowing in the secondary side of the CT 103, instead of the current flowing in the secondary side of the CT 103. In one embodiment, the determination module 421 can be configured to determine the root mean square (RMS) value of the current flowing in the secondary side of the CT 103. Furthermore, the determination module 421 can be configured to determine the end of the tail current in the CT 103 when the RMS value of the current is substantially zero. In one embodiment, upon determining the end of the tail current, the counter value can be reset to zero. Furthermore, the output signal can be deactivated to indicate the end of the tail current. When the output signal is deactivated, the current flowing in the secondary side of the CT 103 is provided to one or more components using information about the current flowing in the secondary side of the CT 103.
[0055] Consider the exemplary operation of the present invention with example values. Acquisition module 419 acquires the current values at three times t, t-1, and t-2. The corresponding current values at these times are given as follows:
[0056] I t = 3.63536
[0057] I t-1 = 3.65816
[0058] I t-2 = 3.68109
[0059] Furthermore, module 421 can determine the instantaneous time constant (K). t ). Module 421 determines the instantaneous time constant (K) at two times, namely t and t-1. t The instantaneous time constant is provided as follows:
[0060] K t = I t / I t-1 = 3.63536 / 3.65816 = 0.993769
[0061] K t-1 = I t-1 / I t-2 = 3.65816 / 3.68109 = 0.993769
[0062] In determining the instantaneous time constant (K) tAfter that, module 421 can determine the deviation value (ΔK) by using a pair of continuous time constants. t This deviation value (ΔK) t The following is provided:
[0063] ΔK t = K t – K t-1 = 0
[0064] In one embodiment, whenever the deviation value ΔK occurs in consecutive moments... t When the deviation is less than a predetermined deviation threshold, execution module 425 can increment the counter. In one embodiment, when the counter exceeds a predetermined count threshold, detection module 427 can detect the presence of a tail current in CT 103. Upon detection of the presence of a current tail, an output signal can be activated to indicate the presence of the tail current. The output signal enables switch 121 to provide a value of "zero" to one or more components using information about the current flowing in the secondary side of CT 103, instead of the current flowing in the secondary side of CT 103. Since there is no current supply from the primary side of CT 103, the current supply is stopped, and the received current may be a decaying current.
[0065] Figure 5 A flowchart illustrating a method for detecting the current tail in a current transformer (CT) 103 according to some embodiments of the present invention is shown.
[0066] like Figure 5 As shown, the method 500 may include one or more blocks (boxes) illustrating the use of Figure 4 The tail current detection unit 111 shown is used to detect the tail current in the CT 103. Method 500 can be generally described as computer-executable instructions. Typically, computer-executable instructions can include routines, programs, objects, components, data structures, procedures, modules, and functions that perform a specific function or implement a specific abstract data type.
[0067] The order in which this method 500 is described should not be construed as restrictive, and any number of blocks of the described method can be combined in any order to implement the method. Furthermore, individual blocks can be removed from these methods without departing from the scope of the subject matter described herein. Moreover, the method can be implemented using any suitable hardware, software, firmware, or a combination thereof.
[0068] At block 501, method 500 includes acquiring a real-time current value of the current flowing in the secondary side of CT 103 via a processor 403 associated with tail current detection unit 111. The real-time current value is a measurement of the current. In one embodiment, this can be achieved through one or more protection functions 117 in intelligent electronic device (IED) 101. N Real-time measurement results are acquired when the trip signal is activated. IED 101 can be electrically coupled to CT 103.
[0069] At block 503, method 500 includes determining the instantaneous time constant (K) via processor 403. t The instantaneous time constant (K) t ) can be the instantaneous current value (I) at a specific time (t). t ) and the current value (I) at the previous time (t-1). t-1 ) proportion.
[0070] At block 505, method 500 includes determining the deviation value (ΔK) via processor 403 and using a pair of continuous time constants. t The continuous time constant can be the instantaneous time constant (K) at a specific time (t). t ) and the time constant (K) at the previous time (t-1) t-1 ).
[0071] At block 507, method 500 includes passing the deviation value (ΔK) through processor 403. t The deviation value (ΔK) is determined by comparing it with a predetermined deviation threshold. t Whether it is less than the predetermined deviation threshold.
[0072] At block 509, based on the comparison result, method 500 includes executing one of the following via processor 403: each time the deviation value (ΔK) is calculated in a consecutive time interval. t The counter increments when the deviation value (ΔK) is less than the predetermined deviation threshold, and when the deviation value (ΔK) is less than the predetermined deviation threshold, the counter increments. t If the deviation exceeds the predetermined deviation threshold, the counter will be reset to zero.
[0073] At block 511, method 500 includes detecting the presence of a tail current in CT 103 by processor 403 when a counter exceeds a predetermined counting threshold. In one embodiment, processor 403 may activate an output signal to indicate the presence of a tail current. This output signal enables switch 121 to provide a value of "zero" to one or more components using information about the current flowing in the secondary side of CT 103, rather than the current flowing in the secondary side of CT 103. In one embodiment, processor 403 may determine the root mean square (RMS) value of the current flowing in the secondary side of CT 103. Furthermore, when the RMS value of the current is substantially zero, processor 403 may determine the end of the tail current in CT 103. Thereafter, processor 403 may reset the counter value to zero when the end of the tail current is determined. Finally, processor 403 may disable the output signal to indicate the end of the tail current. When the output signal is disabled, the current flowing in the secondary side of CT 103 may be provided to one or more components using information about the current flowing in the secondary side of CT 103. The processor 403 can detect tail current in a timely manner to avoid false alarms and erroneous operations caused by tail current.
[0074] Given the technological advancements provided by the disclosed method, the claimed steps are not typical, conventional, or well-known in the art, as they provide a solution to technical problems present in conventional techniques. Furthermore, the claimed steps clearly lead to improvements in the functionality of the system itself, as they provide a technical solution to the technical problem.
[0075] The terms “embodiment,” “implementation,” “multiple embodiments,” “this embodiment,” “these embodiments,” “one or more embodiments,” “some embodiments,” and “an embodiment” refer to “one or more (but not all) embodiments of the invention” unless otherwise expressly stated.
[0076] The terms “including,” “comprising,” “having,” and their variations mean “including but not limited to,” unless otherwise expressly stated.
[0077] Unless otherwise expressly stated, the list of items does not imply that any or all items are mutually exclusive. The terms “a,” “an,” and “the” mean “one or more” unless otherwise expressly stated.
[0078] The description of embodiments having several components that communicate with each other does not imply that all such components are required. Rather, various optional components are described to illustrate various possible embodiments of the invention.
[0079] When a single device or product is described herein, it will be apparent that more than one device / product (whether or not they collaborate) can be used in place of a single device / product. Similarly, when more than one device / product (whether or not they collaborate) is described herein, it will be clear that a single device / product can be used in place of more than one device / product, or a different number of devices / products can be used in place of the number of devices or programs shown. The functionality and / or features of a device can alternatively be embodied by one or more other devices not explicitly described as having such functionality / features. Therefore, other embodiments of the invention do not necessarily need to include the device itself.
[0080] Finally, the language used in this specification has been chosen primarily for readability and instruction purposes, and it may not have been chosen to depict or limit the subject matter of the invention. Therefore, the scope of the invention is not limited by this detailed description, but is defined by any claim of the application based thereon. Thus, the embodiments of the invention are intended to illustrate, rather than limit, the scope of the invention, which is set forth in the appended claims.
[0081] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be conceived by those skilled in the art. The various aspects and embodiments disclosed herein are for illustrative purposes and not for limitation, and the true scope and spirit are indicated by the appended claims.
[0082] List of reference numerals
[0083] 100 architecture
[0084] 101 Intelligent Electronic Devices (IEDs)
[0085] 103 Current Transformer (CT)
[0086] 105 Power System
[0087] 111 Tail Current Detection Unit
[0088] 113 Analog-to-Digital Converter (ADC)
[0089] 115 System Measurement Device
[0090] 121 switch
[0091] 123 Circuit Breaker Fault Protection
[0092] 401I / O interface
[0093] 403 processor
[0094] 405 memory
[0095] 407 data
[0096] Module 409
[0097] 411 Current Data
[0098] 413 Instantaneous Time Constant
[0099] 415 deviation value
[0100] 417 Other Data
[0101] 419 Acquisition Module
[0102] 421 Determine Module
[0103] 423 Comparison Module
[0104] 425 Execution Module
[0105] 427 Detection Module
[0106] 429 Other modules.
Claims
1. A method for detecting the tail current in a current transformer, the method comprising: Obtain the real-time current value of the current flowing in the secondary side of the current transformer; Determine the instantaneous time constant (K) t ), where the instantaneous time constant (K) t ) is the instantaneous current value (I) at a specific time (t). t ) and the current value (I) at the previous time (t-1). t-1 The ratio of ) The deviation value (ΔK) is determined by using a pair of continuous time constants. t ), wherein the pair of continuous time constants is the instantaneous time constant (K) at the specific time (t). t ) and the time constant (K) at the previous time (t-1) t-1 ); The deviation value (ΔK) t The deviation value (ΔK) is compared with a predetermined deviation threshold to determine the deviation value. t Whether it is less than the predetermined deviation threshold; Based on the comparison, perform one of the following: Whenever the deviation value (ΔK) is mentioned in consecutive moments t When the deviation is less than the predetermined deviation threshold, the counter is incremented; and When the deviation value (ΔK) t When the deviation exceeds the predetermined threshold, the counter is reset to zero; and When the counter exceeds a predetermined counting threshold, the presence of tail current in the current transformer is detected.
2. The method according to claim 1, further comprising: An output signal is activated to indicate the presence of a tail current, wherein the output signal enables a switch to provide a value of "zero" to one or more components that use information about the current flowing in the secondary side of the current transformer, rather than the current flowing in the secondary side of the current transformer.
3. The method according to claim 1, further comprising: Determine the root mean square value of the current flowing in the secondary side of the current transformer; as well as The end of the tail current in the current transformer is determined when the root mean square value of the current is essentially zero.
4. The method according to claim 3, further comprising: The counter value is reset to zero when the tail current is determined to be at its end; as well as The output signal is deactivated to indicate the end of the tail current, wherein, when the output signal is deactivated, the current flowing in the secondary side of the current transformer is provided to one or more components that use information about the current flowing in the secondary side of the current transformer.
5. The method according to claim 1, wherein, Real-time measurement results are obtained when a trip signal is activated by one or more protection functions in a relay electrically coupled to the current transformer.
6. A tail current detection unit for detecting the tail current in a current transformer, the tail current detection unit comprising: processor; as well as A memory communicatively coupled to the processor, wherein the memory stores processor instructions that, when executed, cause the processor to: Obtain the real-time current value of the current flowing in the secondary side of the current transformer; Determine the instantaneous time constant (K) t ), where the instantaneous time constant (K) t ) is the instantaneous current value (I) at a specific time (t). t ) and the current value (I) at the previous time (t-1). t-1 The ratio of ) The deviation value (ΔK) is determined by using a pair of continuous time constants. t ), wherein the pair of continuous time constants is the instantaneous time constant (K) at the specific time (t). t ) and the time constant (K) at the previous time (t-1) t-1 ); The deviation value (ΔK) t The deviation value (ΔK) is compared with a predetermined deviation threshold to determine the deviation value. t Whether it is less than the predetermined deviation threshold; Based on the comparison, perform one of the following: Whenever the deviation value (ΔK) is mentioned in consecutive moments t When the deviation is less than the predetermined deviation threshold, the counter is incremented; and When the deviation value (ΔK) t When the deviation exceeds the predetermined threshold, the counter is reset to zero; and When the counter exceeds a predetermined counting threshold, the presence of tail current in the current transformer is detected.
7. The tail current detection unit according to claim 6, wherein, The processor is also configured to: An output signal is activated to indicate the presence of a tail current, wherein the output signal enables a switch to provide a value of "zero" to one or more components that use information about the current flowing in the secondary side of the current transformer, rather than the current flowing in the secondary side of the current transformer.
8. The tail current detection unit according to claim 6, wherein, The processor is also configured to: Determine the root mean square value of the current flowing in the secondary side of the current transformer; and The end of the tail current in the current transformer is determined when the root mean square value of the current is essentially zero.
9. The tail current detection unit according to claim 8, wherein, The processor is also configured to: The counter value is reset to zero when the tail current is determined to be at its end; and The output signal is deactivated to indicate the end of the tail current, wherein, when the output signal is deactivated, the current flowing in the secondary side of the current transformer is provided to one or more components that use information about the current flowing in the secondary side of the current transformer.
10. The tail current detection unit according to claim 6, wherein, The processor acquires real-time measurement results when a trip signal is activated by one or more protection functions in a relay electrically coupled to the current transformer.
11. An intelligent electronic device for detecting the tail current in a current transformer, the intelligent electronic device comprising: Analog-to-digital converter; System measuring device; One or more protection functions; as well as Tail current detection unit, wherein the tail current detection unit is configured as follows: Obtain the real-time current value of the current flowing in the secondary side of the current transformer; Determine the instantaneous time constant (K) t ), where the instantaneous time constant (K) t ) is the instantaneous current value (I) at a specific time (t). t ) and the current value (I) at the previous time (t-1). t-1 The ratio of ) The deviation value (ΔK) is determined by using a pair of continuous time constants. t ), wherein the pair of continuous time constants is the instantaneous time constant (K) at the specific time (t). t ) and the time constant (K) at the previous time (t-1) t-1 ); The deviation value (ΔK) t The deviation value (ΔK) is compared with a predetermined deviation threshold to determine the deviation value. t Whether it is less than the predetermined deviation threshold; Based on the comparison, perform one of the following: Whenever the deviation value (ΔK) is mentioned in consecutive moments t When the deviation is less than the predetermined deviation threshold, the counter is incremented; and When the deviation value (ΔK) t When the deviation exceeds the predetermined threshold, the counter is reset to zero; and When the counter exceeds a predetermined counting threshold, the presence of tail current in the current transformer is detected.
12. The intelligent electronic device according to claim 11, wherein, The tail current detection unit is also configured to: An output signal is activated to indicate the presence of a tail current, wherein the output signal enables a switch to provide a value of "zero" to one or more components that use information about the current flowing in the secondary side of the current transformer, rather than the current flowing in the secondary side of the current transformer.
13. The intelligent electronic device according to claim 11, wherein, The tail current detection unit is also configured to: Determine the root mean square value of the current flowing in the secondary side of the current transformer; and The end of the tail current in the current transformer is determined when the root mean square value of the current is essentially zero.
14. The intelligent electronic device according to claim 13, wherein, The tail current detection unit is also configured to: The counter value is reset to zero when the tail current is determined to be at its end; and The output signal is deactivated to indicate the end of the tail current, wherein, when the output signal is deactivated, the current flowing in the secondary side of the current transformer is provided to one or more components that use information about the current flowing in the secondary side of the current transformer.
15. The intelligent electronic device according to claim 11, wherein, The tail current detection unit acquires real-time measurement results when one or more protection functions in the relay electrically coupled to the current transformer activate a trip signal.