Method and system for detecting open circuit of secondary circuit of current transformer without power failure

Abstract

The invention relates to the technical field of power system detection, in particular to a method and a system for detecting an open circuit of a secondary circuit of a current transformer without power outage, which comprises the following steps: when normal load current flows through the secondary circuit of the current transformer, the system for detecting the open circuit of the secondary circuit of the current transformer without power outage is not accessed; connecting the open-circuit system for detecting the secondary circuit of the current transformer without power failure into the secondary circuit of the current transformer to be detected, and if a signal is not started, determining that the voltage associated with the current of the secondary circuit is close to 0V; and starting the system for detecting the open circuit of the secondary circuit of the current transformer without power failure, and adjusting the icsa signal input according to the impedance and load conditions of the secondary circuit of the current transformer. The system and the method have the advantages that the current loop can be detected at any time under the conditions of no load, light load and heavy load of the running current transformer, no auxiliary equipment needs to be used on a secondary loop conductor of the current transformer in the detection process, and the system and the method can detect the running state of the whole current.

Description

Technical Field

[0001] The invention relates to the technical field of power system detection, in particular to a method and system for detecting an open circuit of a secondary circuit of a current transformer without power outage. Background Art

[0002] In the AC power supply system, current transformers are indispensable for converting the primary large current into the corresponding secondary small current to realize the measurement, protection and metering of the power system. The secondary circuit of the common three-phase current transformer contains four outgoing lines: phase A, phase B, phase C and neutral line (i.e. phase N). When the phase A, phase B and phase C of the secondary circuit are broken, the current of the broken phase becomes 0, and the monitoring equipment can send out an alarm signal. However, when the neutral line is broken, since the three-phase current is basically symmetrical during normal operation, the neutral line current is very small, and the relay protection device cannot detect the neutral line break. In this case, if a ground fault occurs in the primary system, it may cause the protection device to refuse to operate, causing an accident. In addition, when the electricity customer stops using electricity, or one line of the dual power system is in long-term hot standby, the line is in a no-load state, and the current in the secondary circuit of the current transformer is mostly the primary system ground capacitance current or electromagnetic induction scattered current, and its effective value is extremely small. At this time, even if the phase line of the A, B, and C phase secondary current circuit is broken, the protection device cannot sense it. Once a fault occurs, it often causes the power system to trip, causing a major accident or above. At present, the inspection work for whether the secondary circuit of the current transformer is open is mostly power outage inspection. After the inspection is completed, it is necessary to wait until the next power outage to check again, and the interval is often 3-6 years or even longer. During this period, the current circuit is often open due to various reasons. Summary of the invention

[0003] In view of the above problems or problems existing in the prior art, the present invention is proposed.

[0004] Therefore, the purpose of the present invention is to provide a method for detecting an open circuit in the secondary circuit of a current transformer without power outage, which can complete the detection of the current circuit at any time and does not require any auxiliary equipment to be used on the secondary circuit conductor of the current transformer during the detection process.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for detecting an open circuit of a secondary circuit of a current transformer without power outage, comprising: when the secondary circuit of the current transformer is in any state, the system for detecting an open circuit of the secondary circuit of the current transformer without power outage is in a waiting state;

[0006] Connect the non-stop detection current transformer secondary circuit open-circuit system to the secondary circuit of the current transformer to be detected. If no characteristic signal occurs, the characteristic voltage associated with the secondary circuit current is close to 0V.

[0007] Start the current transformer secondary circuit open circuit detection system without power outage, and adjust the ICSA signal input according to the current transformer secondary circuit impedance and load conditions.

[0008] As a preferred scheme of the method for detecting open circuit in the secondary circuit of a current transformer without power outage of the present invention, the normal load current flowing through the secondary circuit of the current transformer to be detected is that the normal load current flowing through the A phase, B phase and C phase of the secondary circuit of the current transformer is normally about 1A to 10A, and the load current is relatively balanced at this time.

[0009] As a preferred scheme of the method for detecting an open circuit of a secondary circuit of a current transformer without power outages of the present invention, wherein: the voltage associated with the secondary circuit current is close to 0V, that is, when the system for detecting an open circuit of a secondary circuit of a current transformer without power outages is connected and the signal is not started temporarily, the secondary windings of the caliper type current transformer CT1 and the caliper type current transformer CT2 will generate voltages UCT1 and UCT2 associated with the magnitudes of the secondary circuit current IA and the secondary circuit current IN, and the voltages UCT1 and UCT2 are close to 0V after being processed by the system for detecting an open circuit of a secondary circuit of a current transformer without power outages.

[0010] As a preferred solution of the method for detecting open circuit of secondary circuit of current transformer without power outage of the present invention, the system for detecting open circuit of secondary circuit of current transformer without power outage is connected to the secondary circuit with industrial frequency signal bypass module, wherein the industrial frequency signal bypass module has a large impedance to signals other than industrial frequency, and the industrial frequency current of the current transformer load generates industrial frequency voltages UCT1 and UCT2 through current transformer CT1 and current transformer CT2.

[0011] As a preferred solution of the method for detecting the open circuit of the secondary circuit of the current transformer without power outage of the present invention, when starting the system for detecting the open circuit of the secondary circuit of the current transformer without power outage, a characteristic signal, namely, the ICSA signal, needs to be injected back through the clamp-type current transformer CT1.

[0012] As a preferred solution of the method for detecting open circuit in the secondary circuit of a current transformer without power outage of the present invention, the effective value of the ICSA signal input needs to be from small to large, and its frequency can be from high to low according to the impedance of the secondary circuit of the current transformer and the load conditions, during which it is ensured that the effective value of the induced injection signal does not exceed 1 mA.

[0013] As a preferred solution of the method for detecting the open circuit of the secondary circuit of the current transformer without power outage of the present invention, the shunting of the icsa signal in the B-phase, C-phase circuits and the neutral line are icsb, icsc and icsn currents respectively, and the relationship formula is as follows:

[0014] icsb+icsc+icsn=icsa

[0015] Among them, since the impedance of current transformer TAb and current transformer TAc is relatively large, and the neutral line load Zn is close to a short-circuit state, the current icsn≈icsa. At this time, the clamp-type current transformer CT2 synchronously induces a voltage Usr≈4mV, which is converted by A / D through the detection system and sent to the DSP signal to complete the calculation and logic judgment processing.

[0016] In order to solve the above technical problems, the present invention also provides the following technical solutions: a system for detecting an open circuit of a secondary circuit of a current transformer without power outage, comprising a current transformer unit, including a current transformer module, and a secondary circuit of a current transformer;

[0017] The human-machine interaction unit includes a multi-band signal processing module connected to the secondary circuit of the current transformer, a multi-band signal frequency selection processing module connected to the secondary circuit of the current transformer, and an industrial frequency signal bypass module respectively connected to the multi-band signal processing module and the multi-band signal frequency selection processing module.

[0018] As a preferred solution of the current transformer secondary circuit open-circuit detection system without power outage of the present invention, the current transformer module includes a clamp-type current transformer CT1 and a clamp-type current transformer CT2; the current transformer secondary circuit includes a current transformer secondary circuit phase A, a current transformer secondary circuit phase B, a current transformer secondary circuit phase C, and a neutral line, and each outgoing line of the current transformer secondary circuit is provided with a corresponding load.

[0019] As a preferred solution of the current transformer secondary circuit opening system for detecting power outages without power outages of the present invention, the multi-band signal processing module is connected to the current transformer secondary circuit A through the clamp-type current transformer CT1; the multi-band signal frequency selection processing module is connected to the neutral line of the current transformer secondary circuit through the clamp-type current transformer CT2.

[0020] Beneficial effects of the present invention: The present invention cooperates with a multi-band signal frequency selection processing module and a multi-band signal processing module to enable a running current transformer to complete current loop detection at any time under no-load, light-load, and heavy-load conditions, and during the detection process, there is no need to use any auxiliary equipment on the secondary loop conductor of the current transformer. The system and its method can not only detect the phase line and neutral line of the current transformer, but also fully detect the operating status of the entire current. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0022] Figure 1 A schematic diagram of the current circuit in operation before system access for a method of detecting an open circuit in the secondary circuit of a current transformer without power outage.

[0023] Figure 2 A schematic diagram of the current circuit in operation after the system is connected to the method for detecting an open circuit in the secondary circuit of a current transformer without power outage.

[0024] Figure 3 A method for detecting an open circuit in the secondary circuit of a current transformer without power outage is provided, and after the system is started, CT1 sends a characteristic signal and CT2 receives the characteristic signal.

[0025] Figure 4 A schematic diagram of an open neutral circuit for detecting an open secondary circuit of a current transformer without power outage.

[0026] Figure 5 A schematic diagram of an open circuit of the A-phase current circuit for a method of detecting an open circuit of a secondary circuit of a current transformer without power outage.

[0027] Figure 6 This is a wiring diagram of the equivalent principle for detecting an open circuit in the secondary circuit of a current transformer without power outage.

[0028] Figure 7 This is a schematic diagram of the principle of signal generation and flow for an example of a current transformer secondary circuit open circuit detection system without power outage.

[0029] Figure 8 Schematic diagram of the neutral line open circuit of the current transformer secondary circuit open system for non-power outage detection.

[0030] Fig. 9 This is a schematic diagram of the A-phase current circuit opening system for detecting the secondary circuit opening of the current transformer without power outage. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0032] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0033] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0034] Example 1

[0035] Reference Figure 1 to Figure 5 , is an embodiment of the present invention, which provides a method for detecting an open circuit in the secondary circuit of a current transformer without power outage, which can complete the detection of the current circuit at any time, and during the detection process, there is no need to use any auxiliary equipment on the secondary circuit conductor of the current transformer.

[0036] Specifically, when the secondary circuit of the current transformer is in any state, the current transformer secondary circuit open circuit system is in a waiting state without power outage detection;

[0037] Connect the non-stop detection current transformer secondary circuit open-circuit system to the secondary circuit of the current transformer to be detected. If no characteristic signal occurs, the characteristic voltage associated with the secondary circuit current is close to 0V, wherein the secondary circuit of the current transformer to be detected is a secondary circuit of the current transformer with load in operation;

[0038] Start the current transformer secondary circuit open circuit detection system without power outage, and adjust the ICSA signal input according to the current transformer secondary circuit impedance and load conditions.

[0039] It should be noted that when the normal load current flows through the secondary circuit of the current transformer, the current transformer secondary circuit is open without power outage and the system is ready. Once operated, it can be connected to the running current transformer. Figure 1 System 102 is a current transformer system in operation to be tested.

[0040] In summary, the present invention cooperates with a multi-band signal frequency selection processing module and a multi-band signal processing module to enable the running current transformer to complete the current loop detection at any time under no-load, light-load and heavy-load conditions, and there is no need to use any auxiliary equipment on the secondary loop conductor of the current transformer during the detection process. The system and its method can not only detect the phase line and neutral line of the current transformer, but also fully detect the operating status of the entire current.

[0041] Example 2

[0042] Reference Figure 1 to Figure 5, which is the second embodiment of the present invention, provides a method for detecting an open circuit in the secondary circuit of a current transformer without power outage, which can complete the detection of the current circuit at any time, and does not require any auxiliary equipment to be used on the secondary circuit conductor of the current transformer during the detection process.

[0043] Specifically, when the secondary circuit of the current transformer is in any state, the current transformer secondary circuit open circuit system is in a waiting state without power outage detection;

[0044] Connect the non-stop detection current transformer secondary circuit open circuit system to the secondary circuit of the current transformer to be detected. If there is no start signal, the voltage associated with the secondary circuit current is close to 0V;

[0045] Start the current transformer secondary circuit open circuit detection system without power outage, and adjust the ICSA signal input according to the current transformer secondary circuit impedance and load conditions.

[0046] Furthermore, the situation where a normal load current flows through the secondary circuit of the current transformer to be detected is that the normal load current flowing through the A phase, the B phase, and the C phase of the secondary circuit of the current transformer is normally about 1A to 10A, and the load current is relatively balanced at this time.

[0047] It should be noted that at this time, the current IN in the neutral line is ≈ 0.0A, where the wiring state at this time is as follows Figure 1 shown.

[0048] Furthermore, the voltage associated with the secondary circuit current is close to 0V, that is, when the secondary circuit open-circuit system of the non-stop power outage detection current transformer is connected and the signal is not started temporarily, the secondary windings of the caliper type current transformer CT1 and the caliper type current transformer CT2 will generate voltage UCT1 and voltage UCT2 associated with the secondary circuit current IA and the secondary circuit current IN. After the voltage UCT1 and voltage UCT2 are processed by the secondary circuit open-circuit system of the non-stop power outage detection current transformer, the voltage is close to 0V.

[0049] Furthermore, the non-power-off detection current transformer secondary circuit opening system is connected to the industrial frequency signal bypass module in the secondary circuit, wherein the industrial frequency signal bypass module has a large impedance to signals other than the industrial frequency, and the industrial frequency current of the current transformer load generates industrial frequency voltages UCT1 and UCT2 through current transformer CT1 and current transformer CT2.

[0050] It should be noted that the wiring status at this time is Figure 3As shown, the non-power-off detection current transformer secondary circuit open system is connected to the secondary circuit with an industrial frequency signal bypass module, wherein the industrial frequency signal bypass module has a large impedance to signals other than industrial frequency, and the industrial frequency current of the current transformer load generates industrial frequency voltages UCT1 and UCT2 through the clamp-type current transformer CT1 and the clamp-type current transformer CT2, which are input into the multi-band signal processing module, but the voltage is close to 0V after being processed by the industrial frequency signal bypass module, which ensures that the multi-band signal generated by the multi-band signal processing unit can be injected into the current transformer secondary circuit through the clamp-type current transformer CT1 and will not be damaged by the UCT1 and UCT2 voltages.

[0051] Furthermore, to start the current transformer secondary circuit open system without power outage detection, a characteristic signal, namely, the ICSA signal, needs to be injected back through the clamp-type current transformer CT1.

[0052] It should be noted that the characteristic signal is a sine wave signal, where the sine wave signal is less than 1mA and the frequency is 0.1~1000Hz, that is, a 1~130V, 1~1000Hz signal is input on the secondary side of CT1. At this time, the wiring status is as follows Figure 3 shown.

[0053] Furthermore, the effective value of the ICSA signal input needs to be from small to large, and its frequency can be from high to low according to the secondary circuit impedance and load conditions of the current transformer, during which it is ensured that the effective value of the inductive injection signal does not exceed 1mA.

[0054] Furthermore, the shunts of the icsa signal in the B-phase, C-phase loops and the neutral line are icsb, icsc, and icsn currents, respectively, and their relationship formulas are as follows:

[0055] icsb+icsc+icsn=icsa

[0056] Among them, since the impedance of current transformer TAb and current transformer TAc is relatively large, and the neutral line load Zn is close to a short-circuit state, the current icsn≈icsa. At this time, the clamp-type current transformer CT2 synchronously induces a voltage Usr≈4mV, which is converted by A / D through the detection system and sent to the DSP signal to complete the calculation and logic judgment processing.

[0057] It should be noted that if Figure 3As shown, the multi-band signal frequency selection processing module can sense the power frequency voltage UCT2 (the voltage value of this voltage is close to 0V after passing through the power frequency signal bypass module) generated by the secondary normal load current of the current transformer through CT2 and the multi-band voltage Usr generated by the injection signal of the current clamp CT1. The two frequencies and amplitudes are not equal. After the voltage quantities are mixed, they are input into the open circuit of the secondary circuit of the non-stop detection current transformer to complete the calculation. The non-power frequency voltage Usr is separated and calculated by the Fourier algorithm, and the frequency and amplitude are compared with the multi-band voltage quantity (1~1000Hz) Usg generated by the multi-band signal processing unit.

[0058] Specifically, if Usr≈Usg, then the neutral line is not open; if Usr cannot be found in the aliased voltage, then the neutral line may be open. Figure 4 Therefore, the system can not only detect whether the neutral line is open, but also detect whether the A phase current loop is open. Figure 5 As shown in the figure, the A-phase current loop is open. Although the frequency modulation signal generating module can generate the voltage Usg, the A-phase current loop is open, so ICSA cannot be generated. The clamp-type current transformer CT2 cannot sense the voltage Usr. Therefore, it can be determined that the A-phase current loop is open.

[0059] The above takes the A-phase current loop injection signal as an example to illustrate how to detect whether the A-phase current loop and the neutral line current loop are open. Similarly, if signals are injected into the B-phase current loop and the C-phase current loop respectively, it can also be detected whether the B-phase or C-phase or neutral line current loop is open. The method and principle are the same as injecting signals from the A-phase.

[0060] In summary, the present invention cooperates with a multi-band signal frequency selection processing module and a multi-band signal processing module to enable the running current transformer to complete the current loop detection at any time under no-load, light-load and heavy-load conditions, and there is no need to use any auxiliary equipment on the secondary loop conductor of the current transformer during the detection process. The system and its method can not only detect the phase line and neutral line of the current transformer, but also fully detect the operating status of the entire current.

[0061] Example 3

[0062] Reference Figure 6 to Figure 9 , which is the third embodiment of the present invention, provides a system for detecting an open circuit of a secondary circuit of a current transformer without power outage, which can complete the detection of the current circuit at any time, and does not require any auxiliary equipment to be used on the secondary circuit conductor of the current transformer during the detection process.

[0063] Specifically, the current transformer unit 100 includes a current transformer module 101 and a current transformer secondary circuit 102;

[0064] The human-computer interaction unit 200 includes a multi-band signal processing module 201 connected to the current transformer secondary circuit 102, a multi-band signal frequency selection processing module 202 connected to the current transformer secondary circuit 102, and an industrial frequency signal bypass module 203 respectively connected to the multi-band signal processing module 201 and the multi-band signal frequency selection processing module 202.

[0065] Furthermore, the current transformer module 101 includes a clamp-type current transformer CT1101a and a clamp-type current transformer CT2101b; the current transformer secondary circuit 102 includes a current transformer secondary circuit A phase 102a, a current transformer secondary circuit B phase 102b, a current transformer secondary circuit C phase 102c, and a neutral line 102d, and each outgoing line of the current transformer secondary circuit 102 is provided with a corresponding load.

[0066] Furthermore, the multi-band signal processing module 201 is connected to the current transformer secondary circuit A phase 102a through the clamp-type current transformer CT1101a; the multi-band signal frequency selection processing module 202 is connected to the neutral line of the current transformer secondary circuit 102 through the clamp-type current transformer CT2101b.

[0067] It should be noted that the multi-band signal processing module 201 can emit an alternating sinusoidal signal with a frequency of 1 to 1000 Hz and a voltage of 0.1 to 130 V. A sinusoidal signal of less than 1 mA is injected in opposite directions at phases A, B, and C through the clamp-type current transformer CT1. At the same time, the clamp-type current transformer CT2 in the multi-band signal frequency selection processing module 202 uses a frequency selection algorithm in the neutral line and other related circuits to measure the effective value of the signal. The judgment of whether the current circuit is open can be completed by whether the characteristic signal emitted by the multi-band signal processing module 201 can be detected. Since the effective value of the induced signal current is limited to within 1 mA and the frequency is different from the fundamental wave 50 Hz, it will not affect the normal operation of the protection, measurement, and billing systems.

[0068] It should be noted that if Figure 6 The following is a wiring diagram of the detection example. The current transformer under test is wired and running normally. The current transformer ratio is 300 / 5. During the detection process, the secondary circuit power frequency current is IA=3.24A, IB=3.24A, IC=3.24, and the neutral line current IN=0.000A. The secondary winding of the clamp-type current transformer is pressurized with Usg=115.15V, 900Hz. After measurement, CT1 generates UCT1=43.317mV in the secondary circuit. Among them, the power frequency voltage and current have been filtered out by hardware circuit and software algorithm, such as Figure 7As shown in the figure, according to the equivalent diagram of the superposition principle, the power frequency current has been stripped off, and only the characteristic signal generated by the measured frequency modulation signal generating module is described, that is, icsa = 0.19∠-89.387mA, icsb = 0.000mA, icsc = 0.000mA, icsn = 0.195mA, at this time, the non-power-off detection current transformer secondary circuit open system Usr = 5.67mV.

[0069] Since this voltage increases from 0.021mV when no test voltage is applied to 5.67mV, it can be determined that there is no open circuit fault in the neutral line loop. Since the applied signal source is in phase A, it can also be determined that there is no open circuit in the phase A current loop.

[0070] Since the power frequency current in the neutral line is close to 0A at this time, the neutral line circuit can be disconnected for a short time, such as Figure 8 As shown, the neutral line is disconnected to complete the test. At this time, the UCT1 voltage rises to 45.425mV, and the measured currents of each circuit are icsa = 0.1411∠-89.326mA, icsb = 70.556∠-89.326μA, icsc = 70.556∠-89.326μA, icsn = 0.00mA, and the current transformer secondary circuit open circuit system is displayed without power outage. The measured induced voltage is Usr = 0.031mV. Since this voltage is close to 0mV, it can be judged that there is an open circuit fault in the neutral line circuit.

[0071] Further, such as Fig. 9 As shown, in order to safely simulate the open circuit of the A-phase current loop, the test frequency current of the secondary loop test is reduced to 0.01A to avoid excessive open circuit voltage, and the A-phase load loop is disconnected to complete the test. At this time, the UCT1 voltage rises to 45.925mV, and the measured currents of each loop are icsa=0.00mA, icsb=0.00mA, icsc=0.00mA, icsn=0.00mA. The current transformer secondary loop open circuit system without power outage detection shows that the measured induced voltage is Usr=0.037mV at this time. Since this voltage is close to 0mV, it can be judged that there is an open circuit fault in the A-phase current loop. The judgment method of the B and C-phase current loops is similar.

[0072] It can be seen from the above examples that the use of this system can measure and determine whether the current circuit of the secondary circuit of the current transformer is open without power outage.

[0073] In summary, the present invention cooperates with a multi-band signal frequency selection processing module and a multi-band signal processing module to enable the running current transformer to complete the current loop detection at any time under no-load, light-load and heavy-load conditions, and there is no need to use any auxiliary equipment on the secondary loop conductor of the current transformer during the detection process. The system and its method can not only detect the phase line and neutral line of the current transformer, but also fully detect the operating status of the entire current.

[0074] Importantly, it should be noted that the construction and arrangement of the present application shown in a plurality of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible without substantially departing from the novel teachings and advantages of the subject matter described in the application (e.g., mounting arrangements, use of materials, color, changes in orientation, etc.). For example, the element shown as integrally formed may be composed of a plurality of parts or elements, the position of the element may be inverted or otherwise changed, and the nature or number or position of the discrete element may be altered or changed. Therefore, all such modifications are intended to be included within the scope of the present invention. The order or sequence of any process or method steps may be changed or reordered according to an alternative embodiment. In the claims, any "bracket plus function" clause is intended to cover the structure of the execution function described herein, and is not only structurally equivalent but also equivalent structure. Without departing from the scope of the present invention, other replacements, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments. Therefore, the present invention is not limited to a specific embodiment, but extends to a variety of modifications that still fall within the scope of the appended claims.

[0075] Additionally, in an effort to provide a concise description of example embodiments, all features of an actual implementation may not be described.

[0076] It should be understood that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but for those of ordinary skill having the benefit of this disclosure, the development effort will be a routine task of design, fabrication, and production without undue experimentation.

[0077] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for detecting an open circuit in a secondary circuit of a current transformer without power outage, characterized in that: include, When the secondary circuit of the current transformer is in any state, the current transformer secondary circuit open circuit system is in the waiting state without power outage detection; Connect the non-stop detection current transformer secondary circuit open-circuit system to the secondary circuit of the current transformer to be detected. If no characteristic signal occurs, the characteristic voltage associated with the secondary circuit current is close to 0V. Start the current transformer secondary circuit open circuit detection system without power outage, and adjust the ICSA signal input according to the current transformer secondary circuit impedance and load conditions.

2. The method for detecting an open circuit in a secondary circuit of a current transformer without power outage as claimed in claim 1, characterized in that: The situation where the normal load current flows through the secondary circuit of the current transformer to be detected is that the normal load current flowing through the A phase, B phase and C phase of the secondary circuit of the current transformer is normally about 1A to 10A, and the load current is relatively balanced at this time.

3. The method for detecting an open circuit in a secondary circuit of a current transformer without power outage as claimed in claim 2, characterized in that: The voltage associated with the secondary circuit current is close to 0V, that is, when the non-stop power outage detection current transformer secondary circuit open system is connected and the signal is not started temporarily, the secondary windings of the caliper type current transformer CT1 and the caliper type current transformer CT2 will generate voltages UCT1 and UCT2 associated with the secondary circuit current IA and the secondary circuit current IN. After the voltages UCT1 and UCT2 are processed by the non-stop power outage detection current transformer secondary circuit open system, the voltages are close to 0V.

4. The method for detecting an open circuit in a secondary circuit of a current transformer without power outage as claimed in claim 3, characterized in that: The non-power-off detection current transformer secondary circuit opening system is connected to the industrial frequency signal bypass module in the secondary circuit, wherein the industrial frequency signal bypass module has a large impedance to signals other than industrial frequency, and the industrial frequency current of the current transformer load generates industrial frequency voltages UCT1 and UCT2 through current transformers CT1 and CT2.

5. The method for detecting an open circuit in a secondary circuit of a current transformer without power outage as claimed in claim 4, characterized in that: The system for starting the current transformer secondary circuit open detection without power outage needs to inject a characteristic signal, namely, an ICSA signal, back through the clamp-type current transformer CT1.

6. The method for detecting an open circuit in a secondary circuit of a current transformer without power outage as claimed in any one of claims 3 to 5, characterized in that: The effective value of the ICSA signal input needs to be from small to large, and its frequency can be from high to low according to the secondary loop impedance and load conditions of the current transformer, during which it is ensured that the effective value of the inductive injection signal does not exceed 1mA.

7. The method for detecting an open circuit in a secondary circuit of a current transformer without power outage as claimed in claim 6, characterized in that: The shunts of the icsa signal in the B-phase, C-phase loops and the neutral line are icsb, icsc, and icsn currents, respectively, and the relationship formulas are as follows: icsb+icsc+icsn=icsa Among them, since the impedance of current transformer TAb and current transformer TAc is relatively large, and the neutral line load Zn is close to a short-circuit state, the current icsn≈icsa. At this time, the clamp-type current transformer CT2 synchronously induces a voltage Usr≈4mV, which is converted by A / D through the detection system and sent to the DSP signal to complete the calculation and logic judgment processing.

8. A system for detecting an open circuit in the secondary circuit of a current transformer without power outage, applicable to a method for detecting an open circuit in the secondary circuit of a current transformer without power outage, characterized in that: include, A current transformer unit (100) comprises a current transformer module (101) and a current transformer secondary circuit (102); The human-machine interaction unit (200) comprises a multi-band signal processing module (201) connected to the current transformer secondary circuit (102), a multi-band signal frequency selection processing module (202) connected to the current transformer secondary circuit (102), and an industrial frequency signal bypass module (203) respectively connected to the multi-band signal processing module (201) and the multi-band signal frequency selection processing module (202).

9. The current transformer secondary circuit opening system for non-stop power detection as claimed in claim 8, characterized in that: The current transformer module (101) comprises a clamp-type current transformer CT1 (101a) and a clamp-type current transformer CT2 (101b); the current transformer secondary circuit (102) comprises a current transformer secondary circuit A phase (102a), a current transformer secondary circuit B phase (102b), a current transformer secondary circuit C phase (102c), and a neutral line (102d); each outgoing line of the current transformer secondary circuit (102) is provided with a corresponding load.

10. The current transformer secondary circuit opening system for non-stop power detection as claimed in claim 9, characterized in that: The multi-band signal processing module (201) is connected to the current transformer secondary circuit A phase (102a) via the clamp-type current transformer CT1 (101a); the multi-band signal frequency selection processing module (202) is connected to the neutral line of the current transformer secondary circuit (102) via the clamp-type current transformer CT2 (101b).

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