Terminal external metering CT secondary side wiring state detection system

Abstract

The utility model discloses a terminal external metering CT secondary side wiring state detection system. The system comprises a test CT, a test circuit, a metering circuit and a control circuit. The primary side of the test CT is electrically connected with the secondary side of the terminal external metering CT, the secondary side of the test CT is electrically connected with the test circuit and the metering circuit, the test circuit is electrically connected with the control circuit, and the metering circuit is electrically connected with the control circuit; the control circuit is an ARM control circuit. According to the utility model, the technical problem of how to accurately and rapidly identify the wiring state of the secondary side of the metering CT outside the terminal and output the result is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of current transformers, in particular to a terminal external metering CT secondary side wiring state detection system. Background Art

[0002] Power transformers, particularly current transformers (CTs), are widely used in power grid systems. A current transformer is an instrument that converts large primary currents into smaller secondary currents for measurement based on the principle of electromagnetic induction. It consists of a closed iron core and windings. Its primary winding has very few turns and is connected in series with the current to be measured; therefore, the entire current of the line often flows through it. Its secondary winding has more turns and is connected in series with the measuring instrument and protection circuit. When the current transformer is operating, its secondary circuit is always closed, so the impedance of the series coil between the measuring instrument and the protection circuit is very low, and the current transformer's operating state is close to a short circuit. A current transformer converts large primary currents into smaller secondary currents for measurement, and the secondary side cannot be open-circuited. The current data used for metering at the power management terminal is converted by an external primary current transformer. The status of the secondary side of the external primary current transformer at the power management terminal has become an important requirement. Therefore, it is urgent to propose a terminal external metering CT secondary side wiring status detection system to solve the technical problem of how to accurately and quickly identify the terminal external metering CT secondary side wiring status and output the results. Utility Model Content

[0003] The main purpose of the utility model is to propose a terminal external metering CT secondary side wiring status detection system, aiming to solve the technical problem of how to accurately and quickly identify the terminal external metering CT secondary side wiring status and output the results.

[0004] To achieve the above-mentioned object, the present invention provides a terminal external metering CT secondary side wiring status detection system, wherein the terminal external metering CT secondary side wiring status detection system comprises:

[0005] A test CT, a test circuit, a metering circuit, and a control circuit; the primary side of the test CT is electrically connected to the secondary side of the metering CT outside the terminal, the secondary side of the test CT is electrically connected to the test circuit and the metering circuit respectively, the test circuit is electrically connected to the control circuit, and the metering circuit is electrically connected to the control circuit; the control circuit is an ARM control circuit.

[0006] In one of the preferred solutions, the test circuit includes an oscillation circuit and a waveform conversion circuit; the oscillation circuit is connected to the secondary side of the test CT and the waveform conversion circuit respectively, and the waveform conversion circuit is connected to the ARM control circuit.

[0007] In one of the preferred solutions, the oscillation circuit is a three-point oscillation circuit.

[0008] In one preferred embodiment, the oscillation circuit includes a resistor R3, a resistor R4, a resistor R8, a resistor R9, a transistor V3, a capacitor C1, a capacitor C3, a capacitor C4, a capacitor C5, and a diode V4; the base of the transistor V3 is respectively connected to the resistor R4, the resistor R9, and the capacitor C3; the collector of the transistor V3 is respectively connected to the resistor R3 and the capacitor C1; the emitter of the transistor V8 is respectively connected to the resistor R8, the capacitor C5, and the capacitor C4; the other ends of the capacitor C3, the capacitor C5, the resistor R8, and the resistor R9 are grounded; the other ends of the resistor R4 and the resistor R4 are connected to a power supply; the other end of the capacitor C1 is respectively connected to the other end of the capacitor C4, the secondary side of the test CT, the diode V4, and the waveform conversion circuit; and the other end of the diode V4 is grounded.

[0009] In one of the preferred solutions, the waveform conversion circuit is a Schmitt trigger circuit.

[0010] One of the preferred solutions, the waveform conversion circuit includes a capacitor C2, a transistor V2, a transistor V1, a resistor R1, a resistor R2, a resistor R5, a resistor R6, a resistor R7 and a resistor R10; one end of the capacitor C2 is connected to the oscillation circuit and the secondary side of the test CT, the other end of the capacitor C2 is connected to the base of the transistor V2, the collector of the transistor V2 is connected to the resistor R2 and the resistor R5 respectively, the emitter of the transistor V2 is connected to the resistor R10 and the emitter of the transistor V1 respectively, the other end of the resistor R5 is connected to the resistor R6 and the base of the transistor V1 respectively, the collector of the transistor V1 is connected to the resistor R1, the resistor R7 and the ARM control circuit respectively, the other ends of the resistor R1 and the resistor R2 are connected to the power supply end, and the other ends of the resistor R10 and the resistor R7 are grounded.

[0011] In one preferred embodiment, the resonant frequency of the test circuit is:

[0012]

[0013] Wherein, f is the resonant frequency, C1 is the capacitance value of capacitor C1, C2 is the capacitance value of capacitor C2, and L is the equivalent inductance.

[0014] In one preferred solution, the equivalent inductance is:

[0015]

[0016] Where L1 is the equivalent inductance of the secondary side of the external measurement CT, L2 is the equivalent inductance of the primary side of the test CT, and L3 is the equivalent inductance of the secondary side of the test CT.

[0017] In the above-mentioned technical solution of the present invention, the secondary-side wiring status detection system for a terminal external metering CT includes: a test CT, a test circuit, a metering circuit, and a control circuit; the primary side of the test CT is electrically connected to the secondary side of the terminal external metering CT, the secondary side of the test CT is electrically connected to the test circuit and the metering circuit, respectively, the test circuit is electrically connected to the control circuit, and the metering circuit is electrically connected to the control circuit; the control circuit is an ARM control circuit. This utility model solves the technical problem of how to accurately and quickly identify the wiring status of the secondary side of a terminal external metering CT and output the result.

[0018] In the utility model, a test CT is installed in the terminal, and the primary side of the test CT is connected to the secondary side of the external metering CT. A test circuit is connected to the secondary side of the test CT. The resonant frequency of the output waveform of the test circuit is read by the control circuit. In combination with the current data output by the metering circuit, the open circuit, short circuit and normal connection status of the secondary side circuit of the external metering CT are obtained. The utility model has a simple structure and is easy to use, and can efficiently realize the detection of the secondary side wiring status of the external metering CT. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the implementation methods or the description of the prior art. Obviously, the drawings described below are only some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0020] Figure 1 This is a schematic diagram of a terminal external metering CT secondary side wiring status detection system according to an embodiment of the present utility model;

[0021] Figure 2 A schematic diagram of a test circuit according to an embodiment of the present utility model;

[0022] Figure 3 This is a simplified structural diagram of the test CT and the terminal external metering CT according to an embodiment of the present utility model;

[0023] Figure 4 This is a simplified schematic diagram of the normal access of the external metering CT of the terminal in the embodiment of the utility model;

[0024] Figure 5 This is a simplified schematic diagram of the open circuit state of the terminal external metering CT according to an embodiment of the present utility model;

[0025] Figure 6 This is a simplified schematic diagram of the short-circuit state of the terminal external metering CT in an embodiment of the utility model.

[0026] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] In addition, in this utility model, the terms "first," "second," etc. are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include at least one of such features.

[0029] Moreover, the technical solutions between the various embodiments of the present invention can be combined with each other, but this must be based on the fact that ordinary technicians in this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0030] See also Figures 1-6 According to one aspect of the present invention, a system for detecting the secondary side wiring status of a terminal external metering CT is provided, wherein the system comprises: a test CT, a test circuit, a metering circuit, and a control circuit; the primary side of the test CT is electrically connected to the secondary side of the terminal external metering CT, the secondary side of the test CT is electrically connected to the test circuit and the metering circuit respectively, the test circuit is electrically connected to the control circuit, and the metering circuit is electrically connected to the control circuit; the control circuit is an ARM control circuit.

[0031] Specifically, in this embodiment, the test circuit is used to obtain status information of the secondary side of an external metering CT, and the metering circuit is used to obtain current data of the power line. The test circuit includes an oscillation circuit and a waveform conversion circuit. The oscillation circuit is connected to the secondary side of the test CT and the waveform conversion circuit, respectively, and the waveform conversion circuit is connected to the ARM control circuit.

[0032] Specifically, in this embodiment, the oscillation circuit is a three-point oscillation circuit.

[0033] Specifically, in this embodiment, the oscillation circuit includes a resistor R3, a resistor R4, a resistor R8, a resistor R9, a transistor V3, a capacitor C1, a capacitor C3, a capacitor C4, a capacitor C5, and a diode V4; the base of the transistor V3 is respectively connected to the resistor R4, the resistor R9, and the capacitor C3, the collector of the transistor V3 is respectively connected to the resistor R3 and the capacitor C1, the emitter of the transistor V8 is respectively connected to the resistor R8, the capacitor C5, and the capacitor C4, the other ends of the capacitor C3, the capacitor C5, the resistor R8, and the resistor R9 are grounded, the other ends of the resistor R4 and the resistor R4 are connected to the power supply terminal, the other end of the capacitor C1 is respectively connected to the other end of the capacitor C4, the secondary side of the test CT, the diode V4, and the waveform conversion circuit; the other end of the diode V4 is grounded.

[0034] Specifically, in this embodiment, the waveform conversion circuit is a Schmitt trigger circuit.

[0035] Specifically, in this embodiment, the waveform conversion circuit includes a capacitor C2, a transistor V2, a transistor V1, a resistor R1, a resistor R2, a resistor R5, a resistor R6, a resistor R7 and a resistor R10; one end of the capacitor C2 is connected to the secondary side of the oscillation circuit and the test CT, the other end of the capacitor C2 is connected to the base of the transistor V2, the collector of the transistor V2 is connected to the resistor R2 and the resistor R5 respectively, the emitter of the transistor V2 is connected to the resistor R10 and the emitter of the transistor V1 respectively, the other end of the resistor R5 is connected to the resistor R6 and the base of the transistor V1 respectively, the collector of the transistor V1 is connected to the resistor R1, the resistor R7 and the ARM control circuit respectively, the other ends of the resistor R1 and the resistor R2 are connected to the power supply end, and the other ends of the resistor R10 and the resistor R7 are grounded; the resistors R3, R4, R8 and R9 provide power for the transistor V3. A static operating point is provided. The capacitor C3 is used to stabilize the frequency of the oscillation circuit. The capacitor C1 provides energy replenishment for the oscillation circuit. The capacitors C4 and C5 form a capacitor-inductor resonant circuit with the secondary side of the test CT. The waveform at the CTIAP point is a sine wave, that is, the waveform at the secondary side output end of the test CT is a sine wave. The waveform is coupled to the base of the transistor V2 via the capacitor C2. The waveform conversion circuit converts the received sine wave output from the secondary side of the test CT into a square wave. The output end of the waveform conversion circuit outputs a three-phase status signal, where CTA is the resonant frequency of phase A, CTB is the resonant frequency of phase B, and CTC is the resonant frequency of phase C. After obtaining the resonant frequency, the ARM control circuit can obtain the status information of the secondary side of the external metering CT. When any condition that causes a change in inductance L occurs, such as a short circuit or open circuit of the terminal external metering CT, the circuit resonant frequency changes, thereby determining the connection status of the secondary side of the external metering CT.

[0036] Specifically, in this embodiment, the resonant frequency of the test circuit is:

[0037]

[0038] Wherein, f is the resonant frequency, C1 is the capacitance value of capacitor C1, C2 is the capacitance value of capacitor C2, and L is the equivalent inductance.

[0039] Specifically, in this embodiment, the equivalent inductance is:

[0040]

[0041] Where L1 is the equivalent inductance of the secondary side of the external measurement CT, L2 is the equivalent inductance of the primary side of the test CT, and L3 is the equivalent inductance of the secondary side of the test CT.

[0042] Specifically, in this embodiment, the method of the terminal external metering CT secondary side wiring status detection system is as follows: the primary side of the terminal built-in test CT is connected to the secondary side of the terminal external metering CT, and the secondary side of the test CT is connected to the test circuit and the metering circuit respectively; the metering circuit obtains power line current data on the secondary side of the test CT; the test circuit performs waveform conversion on the status signal output by the secondary side of the test CT, converts the sinusoidal wave status signal output by the secondary side of the test CT into a square wave status signal, and transmits the waveform-converted status signal to the control circuit; the control circuit determines the wiring status of the secondary side of the terminal external metering CT based on the current data and the status signal.

[0043] Specifically, in this embodiment, see Figure 3 , simplify the processing of the external measurement CT and the test CT of the terminal, wherein the equivalent inductance L2 of the primary side of the test CT, the equivalent inductance L3 of the secondary side of the test CT, the equivalent inductance L1 of the secondary side of the external measurement CT, and calculate the mutual inductance coefficient of the test CT; the mutual inductance coefficient of the test CT is:

[0044]

[0045] Where M is the mutual inductance coefficient of the test CT;

[0046] The equivalent inductance of the test CT self-oscillation circuit is obtained according to the mutual inductance coefficient; the equivalent inductance is:

[0047]

[0048] Calculating the resonant frequency of the test CT output state signal based on the equivalent inductance;

[0049] The resonant frequency is:

[0050]

[0051] Specifically, in this embodiment, the control circuit reads and stores the current data, and performs a primary detection of the connection status of the secondary side of the terminal external metering CT based on the current data; specifically:

[0052] The control circuit reads and saves the power line current data on the secondary side of the CT;

[0053] Determine whether the secondary side of the terminal external metering CT is in an open circuit state based on the three-phase current of the current data; if the three-phase current of the current data is zero, the secondary side of the terminal external metering CT is in an open circuit state; otherwise, it is in a short circuit or normal state, and execute step S42;

[0054] The control circuit reads the resonant frequency of the status signal output by the test CT and performs secondary detection on the wiring status of the secondary side of the terminal external metering CT based on the resonant frequency; specifically:

[0055] Set the resonant frequency threshold range;

[0056] The threshold range includes a first threshold range, a second threshold range and a third threshold range;

[0057] The control circuit reads the resonant frequency of the status signal output by the test CT and determines whether the resonant frequency is within a threshold range;

[0058] If the resonant frequency is within the first threshold range, the secondary side of the terminal external metering CT is in an open circuit state; if the resonant frequency is within the second threshold range, the secondary side of the terminal external metering CT is in a short circuit state; if the resonant frequency is within the third threshold range, the secondary side of the terminal external metering CT is in a normal state.

[0059] Specifically, in this embodiment, a test CT is installed in the terminal, and the primary side of the test CT is connected to the secondary side of an external metering CT. A test circuit is connected to the secondary side of the test CT. The resonant frequency of the test circuit output waveform is read by a control circuit. Combined with the current data output by the metering circuit, the open circuit, short circuit, and normal connection status of the secondary side circuit of the external metering CT are obtained.

[0060] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. All equivalent structural transformations made based on the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, within the scope of the present invention are included in the patent protection scope of the present invention.

Claims

1. A terminal external metering CT secondary side connection status detection system, characterized in that: include: Test CT, test circuits, metering circuits and control circuits; The primary side of the test CT is electrically connected to the secondary side of the terminal external metering CT, the secondary side of the test CT is electrically connected to the test circuit and the metering circuit respectively, the test circuit is electrically connected to the control circuit, and the metering circuit is electrically connected to the control circuit; the control circuit is an ARM control circuit.

2. A terminal external metering CT secondary side connection status detection system according to claim 1, characterized in that: The test circuit includes an oscillation circuit and a waveform conversion circuit; the oscillation circuit is connected to the secondary side of the test CT and the waveform conversion circuit respectively, and the waveform conversion circuit is connected to the ARM control circuit.

3. A terminal external metering CT secondary side connection status detection system according to claim 2, characterized in that: The oscillation circuit is a three-point oscillation circuit.

4. A terminal external metering CT secondary side connection status detection system according to claim 2, characterized in that: The oscillation circuit includes a resistor R3, a resistor R4, a resistor R8, a resistor R9, a transistor V3, a capacitor C1, a capacitor C3, a capacitor C4, a capacitor C5 and a diode V4; the base of the transistor V3 is respectively connected to the resistor R4, the resistor R9 and the capacitor C3, the collector of the transistor V3 is respectively connected to the resistor R3 and the capacitor C1, the emitter of the transistor V8 is respectively connected to the resistor R8, the capacitor C5 and the capacitor C4, the other ends of the capacitor C3, the capacitor C5, the resistor R8 and the resistor R9 are grounded, the other ends of the resistor R4 and the resistor R4 are connected to the power supply terminal, the other end of the capacitor C1 is respectively connected to the other end of the capacitor C4, the secondary side of the test CT, the diode V4 and the waveform conversion circuit; the other end of the diode V4 is grounded.

5. A terminal external metering CT secondary side connection status detection system according to claim 2, characterized in that: The waveform conversion circuit is a Schmitt trigger circuit.

6. A terminal external metering CT secondary side connection status detection system according to claim 4, characterized in that: The waveform conversion circuit includes a capacitor C2, a transistor V2, a transistor V1, a resistor R1, a resistor R2, a resistor R5, a resistor R6, a resistor R7 and a resistor R10; one end of the capacitor C2 is connected to the oscillation circuit and the secondary side of the test CT, the other end of the capacitor C2 is connected to the base of the transistor V2, the collector of the transistor V2 is connected to the resistor R2 and the resistor R5 respectively, the emitter of the transistor V2 is connected to the resistor R10 and the emitter of the transistor V1 respectively, the other end of the resistor R5 is connected to the resistor R6 and the base of the transistor V1 respectively, the collector of the transistor V1 is connected to the resistor R1, the resistor R7 and the ARM control circuit respectively, the other ends of the resistor R1 and the resistor R2 are connected to the power supply end, and the other ends of the resistor R10 and the resistor R7 are grounded.

7. A terminal external metering CT secondary side connection status detection system according to claim 6, characterized in that: The resonant frequency of the test circuit is: Wherein, f is the resonant frequency, C1 is the capacitance value of capacitor C1, C2 is the capacitance value of capacitor C2, and L is the equivalent inductance.

8. A terminal external metering CT secondary side connection status detection system according to claim 7, characterized in that: The equivalent inductance is: Where L1 is the equivalent inductance of the secondary side of the external measurement CT, L2 is the equivalent inductance of the primary side of the test CT, and L3 is the equivalent inductance of the secondary side of the test CT.

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