A wiring detection circuit and method for a current transformer

Abstract

The application provides a wiring detection circuit and method of a current transformer. The wiring detection circuit is connected to a primary winding or an auxiliary winding of the current transformer. During self-checking, the wiring detection circuit inputs a pulse current signal to the winding connected thereto, and then detects an output voltage signal of the current transformer. Then, whether the secondary winding of the current transformer is reversely connected can be determined according to the output voltage signal, without detecting the reverse connection problem when a certain current flows through the primary winding. Therefore, the risk of starting and running of the device to be tested is reduced.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a wiring detection circuit and method for a current transformer. Background Technology

[0002] A CT (Current Transformer) consists of a closed iron core and windings. Its primary winding is connected in series in the circuit where the current needs to be measured, and its secondary winding is connected in series in the measuring instrument and protection circuit. Based on the principle of electromagnetic induction, it converts the large primary current into a smaller secondary current through a certain transformation ratio for protection, measurement and other purposes.

[0003] Currently, conventional CT wiring detection circuits are generally located on the secondary side of the CT and can detect whether there is a broken wire in the coil on that side. However, these existing detection solutions cannot detect whether there is a reverse connection problem in the coil on that side during the equipment self-test. Instead, they can only detect the reverse connection problem when a certain current flows through the primary side of the CT. Therefore, there is a risk in the start-up and operation of the equipment. Summary of the Invention

[0004] In view of this, this application provides a wiring detection circuit and method for a current transformer to realize reverse connection detection during the equipment self-test process, thereby reducing the risks that exist during equipment startup and operation.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] The first aspect of this application provides a wiring detection method for a current transformer, wherein the primary winding or auxiliary winding of the current transformer is connected to a wiring detection circuit, and the wiring detection method includes:

[0007] During the self-test process, the control circuit inputs a pulse current signal to the winding it is connected to;

[0008] The output voltage signal of the current transformer was detected.

[0009] Based on the output voltage signal, determine whether the secondary winding of the current transformer is reversed.

[0010] Optionally, determining whether the secondary winding of the current transformer is reverse-connected based on the output voltage signal includes:

[0011] Based on the output voltage signal, the output current of the secondary winding is calculated, and it is determined whether the output current is less than a first current threshold; or, based on the output voltage signal, it is directly determined whether the output voltage of the secondary winding is less than a first voltage threshold.

[0012] If the output current is less than the first current threshold, or the output voltage is less than the first voltage threshold, then the secondary winding is determined to be reverse-connected.

[0013] Optionally, after detecting the output voltage signal of the current transformer, the method further includes:

[0014] Based on the output voltage signal, determine whether the secondary winding is disconnected or properly connected.

[0015] Optionally, based on the output voltage signal, determining whether the secondary winding is disconnected or properly connected includes:

[0016] Based on the output voltage signal, the output current of the secondary winding is calculated, and it is determined whether the output current is within the range of a first current threshold and a second current threshold; or, based on the output voltage signal, it is directly determined whether the output voltage of the secondary winding is within the range of a first voltage threshold and a second voltage threshold; the first current threshold is less than or equal to the second current threshold, and the first voltage threshold is less than or equal to the second voltage threshold.

[0017] If the output current or the output voltage is within the range of the corresponding two thresholds, then the secondary winding is determined to be disconnected.

[0018] If the output current is greater than the second current threshold, or the output voltage is greater than the second voltage threshold, then the secondary winding connection is determined to be normal.

[0019] Optional, also includes:

[0020] During normal operation and when the secondary winding is disconnected, the voltage across the winding connected to the wiring detection circuit is clamped to a preset voltage to suppress the voltage across the secondary winding.

[0021] Optional, also includes:

[0022] During normal operation, the output voltage signal and the detection voltage signal at both ends of the winding connected to the wiring detection circuit are detected.

[0023] Based on the output voltage signal and the detection voltage signal, determine whether the secondary winding of the current transformer is disconnected.

[0024] Optionally, determining whether the secondary winding of the current transformer is open-circuited based on the output voltage signal and the detected voltage signal includes:

[0025] Based on the output voltage signal, the output current of the secondary winding is calculated, and it is determined whether the output current is within the range of the first current threshold and the second current threshold; and based on the detection voltage signal, the detection current at both ends of the winding connected to the wiring detection circuit is calculated, and it is determined whether the detection current is outside the range of the first current threshold and the second current threshold; the first current threshold is less than or equal to the second current threshold.

[0026] or,

[0027] Based on the output voltage signal, it is directly determined whether the output voltage of the secondary winding is within the range of the first voltage threshold and the second voltage threshold; and based on the detection voltage signal, it is directly determined whether the detection voltage at both ends of the winding connected to the wiring detection circuit is outside the preset voltage range; the first voltage threshold is less than or equal to the second voltage threshold.

[0028] If the output current is within the range of the first current threshold and the second current threshold and the detected current is outside the range of the first current threshold and the second current threshold, or if the output voltage is within the range of the first voltage threshold and the second voltage threshold and the detected voltage is outside the preset voltage range, then the secondary winding is determined to be disconnected.

[0029] A second aspect of this application also provides a wiring detection circuit for a current transformer, including: a detection resistor and a switching transistor;

[0030] The detection resistor is connected between the two ends of the primary winding of the current transformer or an additional auxiliary winding.

[0031] One end of the detection resistor connected to the corresponding winding terminal is connected to the power supply.

[0032] One end of the detection resistor connected to the opposite-named terminal of the corresponding winding is connected to the reference ground through the switching transistor;

[0033] The switching transistor is controlled by the controller of the device under test of the primary winding, so that the controller performs the wiring detection method of the current transformer as described in any of the first aspects above.

[0034] Optionally, it also includes: an inductor, a current-limiting resistor, and a first diode; the current-limiting resistor is connected in series with the inductor between the power supply and the detection resistor, and the first diode is connected in parallel with the inductor to provide a freewheeling path for the inductor after the switching transistor is turned off.

[0035] Optionally, it may also include: a second diode disposed between the sensing resistor and the switching transistor;

[0036] The positive terminal of the second diode is connected to the detection resistor;

[0037] The negative terminal of the second diode is connected to the switching transistor.

[0038] Optionally, it may also include a capacitor disposed between the power supply and the reference ground.

[0039] Optionally, it also includes: a protection circuit connected between the two ends of the winding connected to the wiring detection circuit, used to clamp the voltage at both ends of the winding connected to the wiring detection circuit to a preset voltage when the device under test is operating normally and the secondary winding of the current transformer is disconnected.

[0040] Optionally, the protection circuit includes a bidirectional transient voltage suppressor diode (TVS).

[0041] Optionally, it also includes: a detection sampling conditioning circuit, used to generate and output a detection voltage signal at both ends of the winding connected to the wiring detection circuit to the controller based on the voltage across the detection resistor.

[0042] Optionally, when the detection resistor is connected between the two ends of the primary winding, it further includes: a first signal isolation circuit disposed between the detection sampling conditioning circuit and the controller, and a second signal isolation circuit disposed between the control terminal of the switching transistor and the controller;

[0043] When the detection resistor is connected between the two ends of the auxiliary winding, the reference ground is ground.

[0044] The wiring detection method for current transformers provided in this application connects a wiring detection circuit to the primary winding or auxiliary winding of the current transformer. During self-testing, the circuit inputs a pulse current signal to the connected winding, thereby detecting the output voltage signal of the current transformer. Based on this output voltage signal, it can then determine whether the secondary winding of the current transformer is reverse-connected, without needing a certain current to flow through the primary winding to detect the reverse connection problem. Therefore, the risk of starting and operating the device under test is reduced. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0046] Figure 1a and Figure 1bThese are schematic diagrams showing two different connection relationships of the wiring detection circuit for the current transformer provided in the embodiments of this application;

[0047] Figures 2 to 5 Four flowcharts are provided for the wiring detection method of current transformers according to the embodiments of this application;

[0048] Figure 6a and Figure 6b These are schematic diagrams of two specific structures of the wiring detection circuit for the current transformer provided in the embodiments of this application. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] In this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0051] This application provides a wiring detection method for current transformers to achieve reverse connection detection during equipment self-testing, thereby reducing the risks during equipment startup and operation.

[0052] See Figure 1a or Figure 1b The primary winding of the current transformer has its corresponding terminal as the P1 interface and its opposite terminal as the P2 interface. These two interfaces are used to connect to the circuit under test (DUT) in the device under test, such as a power circuit. Specifically, the current i0 in the DUT flows into the P1 interface and out through the P2 interface. Similarly, the secondary winding has its corresponding terminal as the S1 interface and its opposite terminal as the S2 interface. The output current i1 induced by the secondary winding flows out through the S1 interface and forms a voltage across the sensing resistor R1. This voltage is then processed by the CT sampling and conditioning circuit to obtain the output voltage V of the current transformer. o1 .

[0053] In this embodiment, a wiring detection circuit is connected to both ends of the primary winding of the current transformer, such as... Figure 1a As shown in the diagram; or, an additional auxiliary winding can be added, such as... Figure 1b As shown, the same-name terminal serves as the S3 interface of the current transformer, and the opposite-name terminal serves as the S4 interface. A wiring detection circuit is connected to both ends of the auxiliary winding. This wiring detection circuit can be controlled by a corresponding controller, such as the controller of the device under test, to input a pulse current signal to the winding it is connected to, so that a detection current i2 exists in the corresponding winding. Therefore, even during the self-test process of the device under test, when the current i0 in the circuit under test is zero, the secondary winding can still induce a certain output current i1, thereby enabling the current transformer to obtain a corresponding output voltage V. o1 .

[0054] See Figure 2 The wiring detection method includes:

[0055] S101. During the self-test process, the control wiring detection circuit inputs a pulse current signal to the winding it is connected to.

[0056] During system self-testing, such as when the device under test connected to the primary winding is performing a self-test, the current i0 in the circuit under test is 0. The connection detection circuit inputs a pulse current signal to the connected winding, causing... Figure 1a The primary winding or Figure 1b A detection current i2 can exist in the auxiliary winding. For ease of subsequent calculation and judgment, this pulse current signal is preferably a pulse current signal with a fixed direction, such as the current direction shown in the figure. In this case, i2>0. For the output current i1 induced by the secondary winding, we have: i1>0. This can be verified by the output voltage V of the CT sampling conditioning circuit. o1 This is reflected; however, if the secondary winding is reverse-connected to its CT sampling conditioning circuit, it will cause the output voltage V of the CT sampling conditioning circuit to be affected. o1 This is reflected in the value when i1 < 0, therefore, step S102 needs to be executed.

[0057] S102. The output voltage signal of the current transformer is detected.

[0058] The output voltage signal can reflect the output voltage V. o1 The specific value can be used to execute step S103.

[0059] S103. Determine whether the secondary winding of the current transformer is reversed based on the output voltage signal.

[0060] In practical applications, the corresponding controller can pre-store the parameters of the CT sampling conditioning circuit, thereby obtaining the output current i1 and the output voltage V. o1 The relationship between their values ​​can be determined based on the output voltage V. o1 The output current i1 is calculated, and the secondary winding is determined to be reverse-connected when i1<0 is true; alternatively, an output voltage threshold corresponding to i1<0 can be preset, and the output voltage V can be directly determined. o1 Is it less than the output voltage threshold, and at the output voltage V? o1 When the output voltage is less than the threshold value, it is determined whether the secondary winding is reverse-connected; the specific implementation method depends on the specific application environment, and all are within the protection scope of this application.

[0061] The wiring detection method for current transformers provided in this embodiment can determine whether the secondary winding of the current transformer is reversed based on the above principle, without needing a certain current to flow through the primary winding to detect the reverse connection problem; therefore, it reduces the risk of the device under test starting and running.

[0062] It is worth noting that the direction of the pulse current signal input by the wiring detection circuit to its connected winding is preferably such that the direction of the detection current i2 is the same as the direction of the current i0 in the circuit under test, which is beneficial for the controller to perform the judgment. Of course, the two directions can also be opposite, but the controller needs to take into account the problem of the two directions being opposite during the judgment process and add a reversing step, which is also within the protection scope of this application.

[0063] Based on the previous embodiment, assuming the scaling factor of the CT sampling conditioning circuit is k1, its boost voltage is v ref1 Then V o1 =k1i1R1+v ref1 ;by Figure 1a Taking the structure shown as an example, the number of turns in its primary winding is N0, and the number of turns in its secondary winding is N1. According to the principle of electromagnetic induction, and ignoring the influence of the excitation current, if the secondary winding is properly connected to the CT sampling and conditioning circuit, then i2 × N0 = i1 × N1. At this time, V o1 =k1(N0 / N1)i2R1+v ref1 >v ref1 If the secondary winding is reverse-connected to the CT sampling conditioning circuit, then V o1 =-k1(N0 / N1)i2R1+v ref1 Since i2 > 0, V at this time o1 <v ref1 .

[0064] The two specific implementations of step S103 in this wiring detection method can be:

[0065] (1) Based on the output voltage signal, directly determine the output voltage V of the secondary winding. o1 Whether it is less than a first voltage threshold; specifically, the first voltage threshold may refer to the boost voltage v of the CT sampling conditioning circuit. ref1 If the output voltage V o1 Less than the first voltage threshold, i.e., V o1 <v ref1 This indicates that the secondary winding is reversed at this time.

[0066] (2) Based on the output voltage signal, through i1=(V o1 -v ref1 The output current i1 of the secondary winding can be calculated using k1R1 / (k1R1). Then, it is determined whether this output current i1 is less than a first current threshold. This first current threshold can be 0 or a current threshold near 0, to suit the appropriate detection accuracy; no specific limitation is made here. If the output current i1 is less than the first current threshold, it can be determined that the secondary winding is reverse-connected.

[0067] In addition, such as Figure 3 As shown, after step S102, the wiring detection method further includes:

[0068] S104. Based on the output voltage signal, determine whether the secondary winding is disconnected or the wiring is normal.

[0069] Similar to the above, this step can also include the following two specific implementation forms:

[0070] (1) Based on the output voltage signal, directly determine the output voltage V of the secondary winding. o1 Whether it is within the range of a first voltage threshold and a second voltage threshold; the first voltage threshold is less than or equal to the second voltage threshold, both of which can be the boost voltage v of the CT sampling conditioning circuit. ref1 The upper and lower limits of the floating range centered on the CT sampling conditioning circuit, or both, can be the boost voltage V of the CT sampling conditioning circuit. ref1 If the output voltage V o1 Within the scope of these two, such as V o1 =v ref1 If i1 = 0, it indicates that the secondary winding is open; however, if the output voltage V o1 Greater than the second voltage threshold, for example, V o1 >v ref1 If i1 > 0, it indicates that the secondary winding wiring is normal.

[0071] (2) Based on the output voltage signal V o1 , through i1=(V o1 -vref1 ) / (k1R1) is used to calculate the output current i1 of the secondary winding, and it is determined whether the output current is within the range of the first current threshold and the second current threshold. The first current threshold is less than or equal to the second current threshold. Both can be upper and lower limits of a floating range centered at 0, or both can be 0. If the output current i1 is within the range of these two values, for example, i1 = 0, it can be determined that the secondary winding is disconnected. If the output current i1 is greater than the second current threshold, it means that the i1>0 condition is normal, and it can be determined that the secondary winding connection is normal.

[0072] In practical applications, regardless of whether the output voltage V is directly... o1 Whether the judgment is made by calculation or by calculating the output current i1 first, the CT reverse connection and open circuit detection in the equipment self-test process can be realized. The specific method used depends on the application environment and is within the protection scope of this application.

[0073] It should be noted that the primary winding of a current transformer has very few turns and is connected in series with the circuit containing the current being measured; therefore, it often carries the entire current of the circuit. In contrast, the secondary winding of a current transformer has more turns and is connected in series with the measuring instruments and protection circuits. During operation, the secondary circuit of a current transformer must always be closed. If an open circuit occurs at any point on the secondary side, it will generate excessively high dangerous voltage and cause severe overheating of the core. Current technology allows for protection circuitry to activate in the event of a secondary circuit break during equipment operation. However, this protection circuit has a time delay, so high voltage may still be generated in the secondary winding, potentially causing damage to equipment and personnel.

[0074] This embodiment, based on the above embodiment, adds the following to the wiring detection method: Figure 4 (in order to be in) Figure 3 As shown in the example (based on which):

[0075] S105. During normal operation and when the secondary winding is disconnected, the voltage across the winding connected to the wiring detection circuit is clamped to a preset voltage to suppress the voltage across the secondary winding.

[0076] When the device under test is operating normally, or when the current transformer is operating normally, if a break in the wire occurs at any point on the secondary side, such as the S1 and / or S2 interfaces, it can be resolved by connecting to... Figure 1a primary winding or Figure 1b The protection circuit between the two ends of the auxiliary winding clamps the voltage between the two ends of the primary winding to a predetermined level, thereby suppressing the voltage between the two ends of the secondary winding, preventing high voltage from the secondary winding from causing damage to equipment and personnel, and achieving full-range disconnection protection for the secondary side.

[0077] It is also worth noting that although existing technologies can detect disconnections during equipment operation, their detection algorithms are relatively complex, the software programming in the controller is complicated, and the implementation cost is high.

[0078] The wiring detection method provided in this embodiment, based on the above embodiments, also includes, as well as, Figure 5 (in order to be in) Figure 4 As shown in the example (based on which):

[0079] S201. During normal operation, the output voltage signal and the detection voltage signal at both ends of the winding connected to the wiring detection circuit are detected.

[0080] When the device under test, or current transformer, is operating normally, the output voltage signal is detected. The specific execution process is the same as the corresponding process in step S102, and will not be repeated here. The process of detecting this voltage signal can be similar to the process of detecting the output voltage signal. Figure 1a Taking the structure shown as an example, the voltage between the two ends of the primary winding is sampled, conditioned, and output through a corresponding detection sampling and conditioning circuit to obtain the corresponding detection voltage V. o2 The detected voltage signal is output to the controller, thereby enabling the execution of step S202.

[0081] S202. Determine whether the secondary winding of the current transformer is broken based on the output voltage signal and the detection voltage signal.

[0082] Similar to the above embodiments, step S202 may specifically include:

[0083] (1) Based on the output voltage signal, directly determine the output voltage V of the secondary winding. o1 Whether it is within the range of a first voltage threshold and a second voltage threshold; the first voltage threshold is less than or equal to the second voltage threshold, both of which can be the boost voltage v of the CT sampling conditioning circuit. ref1 The upper and lower limits of the floating range centered on the CT sampling conditioning circuit, or both, can be the boost voltage V of the CT sampling conditioning circuit. ref1 If the output voltage V o1 Within the scope of these two, such as V o1 =v ref1 If i1 = 0, then i1 = 0.

[0084] Furthermore, based on the detected voltage signal, the detection voltage V across the winding connected to the wiring detection circuit can be directly determined. o2 Is it outside the preset voltage range? Figure 1a Taking the structure shown as an example, the specific structure of its wiring detection circuit is as follows: Figure 6aAs shown, a resistor R2 is connected in parallel between the two ends of the primary winding. Assuming the proportional coefficient of the detection sampling conditioning circuit is k2, its boost voltage is v. ref2 Then, during normal wiring, there is V. o2 =k2(-i2)R2+v ref2 At this point, i1 and i2 have a certain correspondence and neither is 0. If the circuit is broken at any point on the secondary side, i1 = 0 and i2 ≠ 0. Therefore, this preset voltage range can only include V. ref2 Alternatively, the detection accuracy can be considered and it can be set to v. ref2 The floating range centered on the detected voltage V. o2 Outside of this preset voltage range, for example, V o2 ≠v ref2 If i2 ≠ 0, then it means that i2 ≠ 0 at this time.

[0085] If the output voltage V o1 Within the range of the first voltage threshold and the second voltage threshold, and the detected voltage V o2 If the voltage is outside the preset range, it can be determined that the secondary winding is broken.

[0086] (2) Based on the output voltage signal, through i1=(V o1 -v ref1 ) / (k1R1), calculate the output current i1 of the secondary winding, and determine whether the output current i1 is within the range of the first current threshold and the second current threshold. The first current threshold is less than or equal to the second current threshold. Both can be the upper and lower limits of the floating range centered on 0, or both can be 0. If the output current i1 is within the range of these two, for example, i1 = 0.

[0087] Furthermore, based on the detected voltage signal, the detection current i2 across the winding connected to the wiring detection circuit is calculated. This calculation can be specifically performed using the formula i2 = (V... o2 -v ref2 If a break occurs in the secondary winding, when |i2R2|≥|V z1 At that time, due to the clamping function of the protection circuit, V o2 =k2V z1 +v ref2 Then according to i2=(V o2 -v ref2The absolute value of i2 calculated by the formula () / (-k2R2) will be less than the actual absolute value of i2, but this does not affect the detection judgment. Therefore, after calculating the detection current i2, it can be determined whether the detection current i2 is outside the range of the first current threshold and the second current threshold; the first current threshold is less than or equal to the second current threshold, and both can be upper and lower limits of a floating range centered on 0, or both can be 0.

[0088] If the output current i1 is within the range of the first current threshold and the second current threshold, and the detected current i2 is outside the range of the first current threshold and the second current threshold, then the secondary winding can be determined to be open.

[0089] If the secondary side is not disconnected, the output current i1 of the secondary winding is calculated based on the output voltage signal, and the detection current i2 at both ends of the winding connected to the wiring detection circuit is calculated based on the detection voltage signal. Ignoring the influence of the excitation current, we will have -i2=i1(N0 / N1)(R1 / R2).

[0090] This embodiment proposes a simple and reliable CT wiring detection scheme, which can not only detect reverse connection or open circuit during equipment self-test, reducing the risk of equipment startup and operation, but also detect CT open circuit during equipment operation. Moreover, it can suppress the voltage on the secondary side of the CT when the open circuit occurs, avoiding damage to the equipment and personnel. In addition, this embodiment can determine the wiring fault by sampling value, without the need for complex algorithms, making it simple, easy to implement, and easy to promote. Furthermore, due to the presence of current i0 in the circuit under test, this embodiment can immediately detect open circuits that occur during equipment operation without controlling the wiring detection circuit to generate pulse current again.

[0091] Another embodiment of this application provides a wiring detection circuit for a current transformer. Figure 6a In order to be in Figure 1a The specific exhibition is based on this. Figure 6b In order to be in Figure 1b For a more detailed demonstration based on this, please refer to [link / reference]. Figure 6a and Figure 6b As shown, it specifically includes: a sensing resistor R2 and a switching transistor Q1; wherein:

[0092] The sensing resistor R2 is connected between the two ends of the primary winding of the current transformer, such as... Figure 6a As shown; or, the sensing resistor R2 is connected between the two ends of the additional auxiliary winding of the current transformer, as shown. Figure 6b As shown.

[0093] One end of the sensing resistor R2 connected to the corresponding winding terminal is connected to the power supply (e.g., Figure 6a VCC2 or shown Figure 6bThe VCC shown in the diagram; one end of the sensing resistor R2 connected to the corresponding winding's opposite terminal is connected to the reference ground via the switching transistor Q1 (as shown in the diagram). Figure 6a (GND2 shown in the image).

[0094] The switching transistor Q1 is controlled by the controller (not shown in the figure) of the device under test connected to the primary winding, so that the controller performs the wiring detection method of the current transformer as described in any of the above embodiments.

[0095] In practical applications, the wiring detection circuit also includes a protection circuit 202, connected between the two ends of the winding connected to the wiring detection circuit, used to clamp the voltage across the winding connected to the wiring detection circuit to a preset voltage V when the device under test is operating normally and the secondary winding of the current transformer is disconnected. z1 .

[0096] The protection circuit 202 can specifically be... Figure 6a and Figure 6b The bidirectional TVS (Transient Voltage Suppressor) Z1 shown can absorb instantaneous large pulse power in both forward and reverse directions and clamp the voltage to a predetermined level. In the event of a circuit break, due to the presence of the bidirectional TVS Z1, the secondary winding voltage is ≤ |(N1 / N0)V. C |,V C This is the maximum clamping voltage of the bidirectional TVS Z1, thereby achieving voltage suppression of the secondary winding.

[0097] Furthermore, in order to achieve CT output and its wiring detection output, a corresponding resistor R1 is set between the S1 and S2 interfaces at both ends of its secondary winding, and the output voltage V is obtained through the CT sampling conditioning circuit 101. o1 ;That Figure 6a At the P1 and P2 interfaces at both ends of the primary winding, or, Figure 6b The detection voltage V at the S3 and S4 interfaces at both ends of the auxiliary winding is obtained through the detection sampling and conditioning circuit 201. o2 The detection sampling conditioning circuit 201 can generate and output the detection voltage signal across the winding connected to the wiring detection circuit to the controller based on the voltage across the detection resistor R2.

[0098] The controller implements the above-mentioned wiring detection method by controlling the operation of the wiring detection circuit. Figure 6a Taking the structure shown as an example, its specific principle is as follows:

[0099] (1) Self-inspection process

[0100] During self-test, i0 = 0, the control switch Q1 is turned on, and the circuit generates a pulse current signal in a fixed direction, causing the detection current i2 to flow through the primary side of the CT. At this time, i2 > 0, and the influence of the excitation current is ignored.

[0101] If the CT wiring is correct, then V o1 =k1(N0 / N1)i2R1+v ref1 >v ref1 If CT is disconnected, then V o1 =v ref1 If CT is reversed, then V o1 =-k1(N0 / N1)i2R1+v ref1 <v ref1 .

[0102] Therefore, by detecting the output voltage V o1 This can be used to determine if the CT wiring is correct. Alternatively, it can be checked by the output voltage V. o1 Calculate the output current i1. If i1>0, the wiring is correct; if i1=0, the wire is broken; if i1<0, the connection is reversed.

[0103] (2) Operation process

[0104] After the self-test passes, there is no reverse connection during operation; only broken wires need to be checked.

[0105] V o1 =k1i1R1+v ref1 According to i1=(V o1 -v ref1 ) / (k1R1) to calculate the output current i1; when |i2R2|<|V z1 |Time,V o2 =k2(-i2)R2+v ref2 When |i2R2|≥|V z1 |Time,V o2 =k2V z1 +v ref2 This may only occur when the connection is lost.

[0106] According to the formula i2=(V o2 -v ref2 ) / (-k2R2) is used to derive i2, when |i2R2|≥|V z1 The absolute value of i2 calculated based on this formula will be less than the actual absolute value of i2, but this does not affect the detection judgment.

[0107] If the wire is not disconnected, the effect of the excitation current can be ignored, and -i2 = i1(N0 / N1)(R1 / R2); if the wire is disconnected, i1 = 0 and i2 ≠ 0.

[0108] Therefore, by detecting the output voltage Vo1 and detection voltage V o2 By calculating and comparing the output current i1 and the detection current i2, it can be determined whether the CT is disconnected.

[0109] The wiring detection circuit proposed in this embodiment can detect reverse connection or open circuit during equipment self-test, and can detect CT open circuit and suppress the secondary coil voltage when the open circuit occurs during equipment operation.

[0110] In practical applications, when selecting the parameters of the detection resistor R2 and the bidirectional TVS Z1, consideration should be given to minimizing the impact on CT sampling accuracy. Specifically:

[0111] In selecting the parameters of the bidirectional TVS Z1, it is assumed that the absolute value of the maximum clamping voltage of the selected bidirectional TVS Z1 is |V C |=|k z1 (N0 / N1)i max R1|,i max This represents the maximum current value of the circuit under test, such as the main power circuit of the equipment. k z1 The preset coefficient is selected based on actual needs, since the secondary winding voltage at the time of wire breakage is |k z1 i max R1|, therefore k z1 The reverse withstand voltage of the bidirectional TVS Z1 should be greater than 1. RWM |Should be set to|V RWM |>|(N0 / N1)i max R1| is set, and a certain margin is taken to reduce the impact on sampling accuracy.

[0112] When selecting the parameters for the sensing resistor R2, if a wired sensing circuit is included, and the influence of the bidirectional TVS Z1 is ignored, then:

[0113] N0(i0+i2)=N1i1;

[0114] N0[i0-(N0 / N1)i1(R1 / R2)]=N1i1;

[0115] N0i0=N1i1[1+(N0 / N1) 2 (R1 / R2)];

[0116] i0=(N1 / N0)i1[1+(N0 / N1) 2 (R1 / R2)];

[0117] The actual calculation formula is: i0=(N1 / N0)i1;

[0118] Therefore, the presence of the sensing resistor R2 will introduce sampling error. If the relative error caused by the sensing resistor R2 is to be controlled within the preset error Δ%, then its resistance value R2 should be set to > (N0 / N1). 2 R1[(100-|Δ|) / |Δ|].

[0119] It should be noted that, for Figure 6a The structure shown requires isolated power supply because the wiring detection circuit is connected to the primary side; its power supply is drawn from a separate power source, V. CC2 Its reference ground GND2 and the secondary side ground GND are connected at different locations; moreover, the received control signal and the output detection signal both require corresponding isolation, that is, it also requires: a first signal isolation circuit 203 set between the detection sampling conditioning circuit 201 and the controller, and a second signal isolation circuit 204 set between the control terminal of the switching transistor Q1 and the controller. When this wiring detection circuit is applied to a through-heart CT, that is, for Figure 6b In the structure shown, since insulation is considered during the winding of the auxiliary coil, the power supply and signal of the wiring detection circuit do not need to be isolated. The aforementioned power supply is directly V. CC Furthermore, the aforementioned reference location can be directly GND.

[0120] In addition, since the auxiliary winding is an extra winding, its number of turns N2 can be adjusted according to actual needs, and the circuit design can be more flexible. For example, when the value of N2 is large, the self-test current that the circuit needs to provide is also relatively small, which can reduce the current requirements of the devices.

[0121] and, Figure 6b The parameter selection for the detection resistor R2 and the bidirectional TVS Z1 in the through-hole CT wiring detection circuit shown is similar to... Figure 6a The general CT wiring detection circuit shown is slightly different. Specifically:

[0122] In the parameter selection of bidirectional TVS Z1, the absolute value of its maximum clamping voltage |V C |=|k z1 (N2 / N1)i max R1|. Its reverse withstand voltage|V RWM |Should be set to|V RWM |>|(N2 / N1)i max R1|, with a certain margin.

[0123] When selecting the parameters for the sensing resistor R2, if a wired sensing circuit is included, and the influence of the bidirectional TVS Z1 is ignored, then:

[0124] N0i0 = -N2i2 + N1i1;

[0125] N0i0=(N2 / N1)i1(R1 / R2)+N1i1;

[0126] N0i0=N1i1[1+(N2 / N1) 2 (R1 / R2)];

[0127] i0=(N1 / N0)i1[1+(N2 / N1) 2 (R1 / R2)];

[0128] The actual calculation formula is: i0 = (N1 / N0)i1;

[0129] Therefore, the presence of the sensing resistor R2 will introduce sampling error. If the relative error caused by the sensing resistor R2 is to be controlled within the preset error Δ%, then its resistance value R2 should be set to > (N2 / N1). 2 R1[(100-|Δ|) / |Δ|].

[0130] In practical applications, this wiring detection circuit may further include Figure 6a and Figure 6b The diagram shows: inductor L1, current-limiting resistor R3, and first diode D1; wherein: inductor L1 is used to suppress the rate of current rise; current-limiting resistor R3 is connected in series with inductor L1 to the power supply (e.g., Figure 6a VCC2 or shown Figure 6b The VCC shown is connected between the sensing resistor R2 and the current peak to limit the oscillation in the circuit; the first diode D1 is connected in parallel with the inductor L1 to provide a freewheeling path for the inductor L1 after the switch Q1 is turned off.

[0131] Optionally, the wiring detection circuit may also include Figure 6a and Figure 6b As shown: the second diode D2, which is placed between the detection resistor R2 and the switching transistor Q1, is used to block the influence of the wiring detection circuit on the CT sampling conditioning circuit 101; the positive terminal of the second diode D2 is connected to the detection resistor R2; the negative terminal of the second diode D2 is connected to the switching transistor Q1.

[0132] Optionally, the wiring detection circuit may further include: a setting on the power supply (e.g., Figure 6a The V shown CC2 or Figure 6b The V shown CC ) and reference location (e.g. Figure 6a GND2 or shown Figure 6b The capacitor C1 between GND (as shown) serves as an energy storage capacitor, ensuring a stable power supply to the wiring detection circuit.

[0133] Similar or identical parts between the various embodiments in this specification can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the description of the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment solution according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0134] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0135] The features described above regarding the disclosed embodiments can be substituted for or combined with each other to enable those skilled in the art to implement or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for testing the wiring of a current transformer, characterized in that, The primary winding or auxiliary winding of the current transformer is connected to a wiring detection circuit, and the wiring detection method includes: During the self-test, the control circuit inputs a pulse current signal to the winding it is connected to; during the self-test, the current in the test circuit connected to the primary winding is zero. The output voltage signal of the current transformer was detected. Based on the output voltage signal, determine whether the secondary winding of the current transformer is reversed.

2. The wiring detection method for a current transformer according to claim 1, characterized in that, Determining whether the secondary winding of the current transformer is reverse-connected based on the output voltage signal includes: Based on the output voltage signal, the output current of the secondary winding is calculated, and it is determined whether the output current is less than a first current threshold; or, based on the output voltage signal, it is directly determined whether the output voltage of the secondary winding is less than a first voltage threshold. If the output current is less than the first current threshold, or the output voltage is less than the first voltage threshold, then the secondary winding is determined to be reverse-connected.

3. The wiring detection method for a current transformer according to claim 1, characterized in that, After detecting the output voltage signal of the current transformer, the process further includes: Based on the output voltage signal, determine whether the secondary winding is disconnected or properly connected.

4. The wiring detection method for a current transformer according to claim 3, characterized in that, Based on the output voltage signal, determine whether the secondary winding is disconnected or properly connected, including: Based on the output voltage signal, the output current of the secondary winding is calculated, and it is determined whether the output current is within the range of a first current threshold and a second current threshold; or, based on the output voltage signal, it is directly determined whether the output voltage of the secondary winding is within the range of a first voltage threshold and a second voltage threshold; the first current threshold is less than or equal to the second current threshold, and the first voltage threshold is less than or equal to the second voltage threshold. If the output current or the output voltage is within the range of the corresponding two thresholds, then the secondary winding is determined to be disconnected. If the output current is greater than the second current threshold, or the output voltage is greater than the second voltage threshold, then the secondary winding connection is determined to be normal.

5. The wiring detection method for a current transformer according to any one of claims 1 to 4, characterized in that, Also includes: During normal operation and when the secondary winding is disconnected, the voltage across the winding connected to the wiring detection circuit is clamped to a preset voltage to suppress the voltage across the secondary winding.

6. The wiring detection method for a current transformer according to any one of claims 1 to 4, characterized in that, Also includes: During normal operation, the output voltage signal and the detection voltage signal at both ends of the winding connected to the wiring detection circuit are detected. Based on the output voltage signal and the detection voltage signal, determine whether the secondary winding of the current transformer is disconnected.

7. The wiring detection method for a current transformer according to claim 6, characterized in that, Determining whether the secondary winding of the current transformer is open-circuited based on the output voltage signal and the detected voltage signal includes: Based on the output voltage signal, the output current of the secondary winding is calculated, and it is determined whether the output current is within the range of the first current threshold and the second current threshold; and based on the detection voltage signal, the detection current at both ends of the winding connected to the wiring detection circuit is calculated, and it is determined whether the detection current is outside the range of the first current threshold and the second current threshold; the first current threshold is less than or equal to the second current threshold. or, Based on the output voltage signal, it is directly determined whether the output voltage of the secondary winding is within the range of the first voltage threshold and the second voltage threshold; and based on the detection voltage signal, it is directly determined whether the detection voltage at both ends of the winding connected to the wiring detection circuit is outside the preset voltage range; the first voltage threshold is less than or equal to the second voltage threshold. If the output current is within the range of the first current threshold and the second current threshold and the detected current is outside the range of the first current threshold and the second current threshold, or if the output voltage is within the range of the first voltage threshold and the second voltage threshold and the detected voltage is outside the preset voltage range, then the secondary winding is determined to be disconnected.

8. A wiring detection circuit for a current transformer, characterized in that, include: Detecting resistors and switching transistors; The detection resistor is connected between the two ends of the primary winding of the current transformer or an additional auxiliary winding. One end of the detection resistor connected to the corresponding winding terminal is connected to the power supply. One end of the detection resistor connected to the opposite-named terminal of the corresponding winding is connected to the reference ground through the switching transistor; The switching transistor is controlled by the controller of the device under test of the primary winding, so that the controller performs the wiring detection method of the current transformer as described in any one of claims 1 to 7.

9. The wiring detection circuit for a current transformer according to claim 8, characterized in that, Also includes: Inductor, current-limiting resistor and first diode; The current-limiting resistor and the inductor are connected in series between the power supply and the detection resistor; The first diode is connected in parallel with the inductor to provide a freewheeling path for the inductor after the switch is turned off.

10. The wiring detection circuit for a current transformer according to claim 8, characterized in that, Also includes: A second diode is disposed between the sensing resistor and the switching transistor; the positive terminal of the second diode is connected to the sensing resistor, and the negative terminal of the second diode is connected to the switching transistor.

11. The wiring detection circuit for a current transformer according to claim 8, characterized in that, Also includes: A capacitor is disposed between the power supply and the reference ground.

12. The wiring detection circuit for a current transformer according to any one of claims 8 to 11, characterized in that, Also includes: A protection circuit is connected between the two ends of the winding connected to the wiring detection circuit. It is used to clamp the voltage at both ends of the winding connected to the wiring detection circuit to a preset voltage when the device under test is operating normally and the secondary winding of the current transformer is disconnected.

13. The wiring detection circuit for the current transformer according to claim 12, characterized in that, The protection circuit includes a bidirectional transient voltage suppressor diode (TVS).

14. The wiring detection circuit for a current transformer according to any one of claims 8 to 11, characterized in that, Also includes: The detection sampling and conditioning circuit is used to generate and output the detection voltage signal across the winding connected to the wiring detection circuit to the controller based on the voltage across the detection resistor.

15. The wiring detection circuit for a current transformer according to claim 14, characterized in that, When the detection resistor is connected between the two ends of the primary winding, it further includes: a first signal isolation circuit disposed between the detection sampling conditioning circuit and the controller, and a second signal isolation circuit disposed between the control terminal of the switching transistor and the controller; When the detection resistor is connected between the two ends of the auxiliary winding, the reference ground is ground.

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