Single-transformer high-precision current measurement and protection device

Abstract

The utility model provides a single-transformer high-precision current measurement and protection device, and belongs to the technical field of power distribution control. The device comprises a current sampling circuit, a rectification and current sampling circuit, an auxiliary power supply and voltage sampling circuit, a mutual inductor power supply voltage stabilizing circuit, a microcontroller and protection analysis control unit, a protection current processing circuit and a high-precision current measuring unit. The current sampling circuit is used for collecting current signals of each phase line of the circuit breaker and transmitting the current signals to the rectification and current sampling circuit, and the rectification and current sampling circuit rectifies the current signals and then transmits the rectified current signals to the mutual inductor power supply voltage stabilizing circuit in parallel. The mutual inductor power supply voltage stabilizing circuit carries out voltage stabilization processing on the current signal and then transmits the current signal to the microcontroller and protection analysis control unit. The rectification and current sampling circuit is also connected with a protection current processing circuit and a high-precision current measurement unit, and the protection current processing circuit is used for carrying out the reverse processing of a current signal, and then transmitting the current signal to the microcontroller and protection analysis control unit for current fault analysis. And the high-precision current measurement unit performs current measurement on the received current signal. The device is high in sampling precision, stable and reliable; and the safety of a power supply line can be effectively guaranteed.

Description

Technical Field

[0001] The utility model belongs to the technical field of circuit control, and in particular relates to a single mutual inductor high-precision current measurement and protection device. Background Art

[0002] Existing intelligent electronic molded case circuit breakers typically use two sets of current transformers for current sampling: one set is for protection and power supply, and the other is for high-precision measurement. Due to relevant national standards, the protection transformer, in addition to providing measurement functions, also needs to measure current to provide power for the electronic controller to operate properly. Therefore, the protection current transformer cannot provide high-precision current measurement. With the development of the power Internet of Things, precise measurement of electricity consumption information at all levels is required. The measurement accuracy of various electricity parameters within the rated current range must be no less than 0.5%. To meet this requirement, independent high-precision measurement transformers are generally used to accurately measure current signals within the rated current range, providing accurate electricity consumption data for intelligent power management. In addition, as a current sampling device, the current transformer is also a power device. During normal operation, it consumes a certain amount of power and generates heat energy. This can increase the temperature of the circuit breaker during normal operation and, in severe cases, reduce its operating performance.

[0003] To this end, a current measurement and protection solution using a single transformer has been designed. For example, patent application number: 202221772552.0 discloses a measurement and protection device for an electrical switch. The device comprises at least a controller, a primary current conductive circuit, and a current transformer. The controller includes at least a rectifier and sampling circuit, a power supply circuit, a current signal processing circuit, and a microprocessor. The current transformer is composed of a secondary coil wound on a magnetic core. The secondary AC current signal of the current transformer is processed by the rectifier and sampling circuit and amplified by the current signal processing circuit to form a corresponding secondary current full-wave three-segment waveform. The three-segment current waveform signal is input to the microprocessor for high-precision current and / or power measurement, current overload protection, and fault current transient protection. The current transformer also provides the output energy of the secondary coil to the power supply circuit through the rectifier and sampling circuit, converting it into power sufficient for the controller to operate. This solution can achieve current measurement and protection using a single transformer, but it has the following problems: 1. The load linearity of the current sampling circuit in the existing solution cannot be guaranteed, which means that the current measurement accuracy cannot meet the design requirements. Utility Model Content

[0004] In view of this, the purpose of the present invention is to provide a single transformer high-precision current measurement and protection device to solve the problem of low current sampling accuracy.

[0005] The objectives of the utility model can be achieved through the following technical solutions: A single-transformer high-precision current measurement and protection device, arranged between a primary circuit line and a load, characterized in that it includes a current sampling circuit, a rectification and current sampling circuit, an auxiliary power supply and voltage sampling circuit, a transformer power supply voltage stabilization circuit, a microcontroller and a protection analysis and control unit, a protection current processing circuit and a high-precision current measurement unit, wherein the current sampling circuit is used to collect current signals of each phase line of the circuit breaker and transmit them to the rectification and current sampling circuit, the rectification and current sampling circuit transmits the current signals in parallel to the transformer power supply voltage stabilization circuit after rectification processing, the transformer power supply voltage stabilization circuit transmits the current signals to the microcontroller and protection analysis and control unit after voltage stabilization processing; the rectification and current sampling circuit is also connected to the protection current processing circuit and the high-precision current measurement unit respectively, the protection current processing circuit is used to transmit the current signals to the microcontroller and protection analysis and control unit after reverse processing for current fault analysis, and the high-precision current measurement unit performs current measurement on the received current signals.

[0006] Preferably, the current sampling circuit includes a first mutual inductor, a second mutual inductor and a third mutual inductor, which are respectively inserted into the three phase lines of the circuit breaker.

[0007] Preferably, the rectification and current sampling circuit includes three first rectification branches, a second rectification branch and a third rectification branch with the same circuit structure. The three rectification branches are respectively connected to three mutual inductors in a one-to-one correspondence. Each rectification branch includes a rectifier bridge and a first sampling resistor and a second sampling resistor respectively connected to the two bridge arms of the rectifier bridge.

[0008] Preferably, the auxiliary power supply and voltage sampling circuit consists of a resistance voltage divider sampling circuit and a three-phase input switching power supply. The input ends of the auxiliary power supply and voltage sampling circuit are respectively connected to the three phase lines of the circuit breaker, the voltage sampling output ends of the auxiliary power supply and voltage sampling circuit are connected to the high-precision current measurement unit, and the auxiliary power supply output ends of the auxiliary power supply and voltage sampling circuit are connected to the transformer power supply voltage stabilization circuit.

[0009] Preferably, the auxiliary power supply and voltage sampling circuit includes a resistor voltage divider sampling circuit and a three-phase input switching power supply. The resistor voltage divider sampling circuit includes three sampling sub-circuits corresponding to three phase lines respectively, and each sampling sub-circuit is composed of four resistors connected in series; the three-phase input switching power supply is composed of a rectifier unit, a filter unit, a transformer unit and a switching power supply unit.

[0010] Preferably, the mutual inductor power supply and voltage stabilization circuit includes a first diode, a second diode, a field effect transistor, a voltage stabilization chip, a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, a second capacitor, a third capacitor, a transient suppression tube and a relay. The positive electrode of the first diode, the drain of the field effect transistor, the negative electrode of the transient suppression tube and one end of the normally open contact of the relay are all connected to the positive output end of the rectification and current sampling circuit; one end of the first resistor, one end of the first capacitor, the negative electrode of the second diode and the positive electrode of the second capacitor are all connected to the negative electrode of the first diode; one end of the coil of the relay and the positive electrode of the second diode are both connected to the auxiliary power supply output end of the auxiliary power supply and voltage sampling circuit; the other end of the normally open contact of the relay, the other end of the coil of the relay, The positive electrode of the transient suppression tube, the source electrode of the field effect tube, one end of the third resistor, the ground end of the voltage stabilizing chip, one end of the fourth resistor, the other end of the first capacitor, the negative electrode of the second capacitor and one end of the third capacitor are all connected to the negative output end of the rectification and current sampling circuit; the gate of the field effect tube is respectively connected to the other end of the third resistor and one end of the second resistor; the other end of the second resistor is connected to the output end of the voltage stabilizing chip; the input end of the voltage stabilizing chip is respectively connected to the other end of the first resistor, the other end of the fourth resistor and the other end of the third capacitor; the positive electrode of the second capacitor is connected to the power input end of the microcontroller and the protection current sampling control unit as the output end, and the negative electrode of the second capacitor is connected to the ground end of the microcontroller and the protection current sampling control unit as the ground end.

[0011] Preferably, the microcontroller and protection analysis control unit are composed of a microcontroller and peripheral circuits, which perform analog-to-digital conversion on the protection current sampling signal and analyze the converted data. If fault data is analyzed, the corresponding protection action is output; at the same time, the data of the high-precision current measurement unit are interacted.

[0012] Preferably, the protection current processing circuit includes three first processing branches, a second processing branch and a third processing branch with the same circuit structure. The three processing branches are respectively connected to the three rectifier branches in a one-to-one correspondence, and each processing branch includes a first reverse circuit and a second reverse circuit; the input end of the first reverse circuit is connected to one end of the first sampling resistor, and the output end of the first reverse circuit is connected to the signal input end of the microcontroller and the protection analysis and control unit; the input end of the second reverse circuit is connected to one end of the second sampling resistor, and the output end of the second reverse circuit is connected to the signal input end of the microcontroller and the protection analysis and control unit.

[0013] Preferably, the first inverting circuit and the second inverting circuit are both inverting circuits formed by operational amplifiers.

[0014] Preferably, the high-precision current measurement unit adopts a dedicated metering chip, which has the function of measuring electrical parameters such as current, voltage, power, and electricity, and the measurement error of the chip does not exceed 0.5%.

[0015] Compared with the existing technology, this single transformer high-precision current measurement and protection device has the following advantages:

[0016] 1. The utility model adopts the purely resistive contacts of the relay to short-circuit the nonlinear device in the current sampling loop, thereby ensuring the stability of the internal resistance of the sampling loop, thereby realizing a high-precision current measurement function.

[0017] 2. For abnormal fault current, positive and negative half-cycle signals are simultaneously input into the microcontroller and protection analysis control unit for analysis and processing to achieve the purpose of rapid action and ensure the safety of the power supply line.

[0018] 3. The technical solution of using a single mutual inductor can reduce the design space of the circuit breaker, reduce the production cost of the circuit breaker, provide technical support for the miniaturization design of the circuit breaker, and have higher economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 1 is a circuit schematic diagram of a single-transformer high-precision current measurement and protection device according to an embodiment.

[0020] Figure 2 This is the schematic diagram of the auxiliary power supply and voltage sampling circuit.

[0021] Figure 3 It is the schematic diagram of the microcontroller and protection analysis control unit.

[0022] Figure 4 This is the schematic diagram of the high-precision current measurement unit.

[0023] In the figure, 1. Current sampling circuit; 2. Rectification and current sampling circuit; 3. Auxiliary power supply and voltage sampling circuit; 4. Transformer power supply and voltage stabilization circuit; 5. Microcontroller and protection analysis and control unit; 6. Protection current processing circuit; 7. High-precision current measurement unit. DETAILED DESCRIPTION

[0024] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, but are not to be construed as limiting the present invention.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0026] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0027] like Figure 1 As shown, the present invention provides a single-transformer high-precision current measurement and protection device, which is arranged between the primary circuit line and the load, and includes a current sampling circuit 1, a rectification and current sampling circuit 2, an auxiliary power supply and voltage sampling circuit 3, a transformer power supply voltage stabilization circuit 4, a microcontroller and protection analysis and control unit 5, a protection current processing circuit 6 and a high-precision current measurement unit 7. The current sampling circuit 1 is used to collect current signals of each phase line of the circuit breaker and transmit them to the rectification and current sampling circuit 2. The rectification and current sampling circuit 2 rectifies the current signal and transmits it in parallel to the transformer power supply voltage stabilization circuit 4. The transformer power supply voltage stabilization circuit 4 transmits the current signal to the microcontroller and protection analysis and control unit 5 after voltage stabilization. The rectification and current sampling circuit 2 is also connected to the protection current processing circuit 6 and the high-precision current measurement unit 7 respectively. The protection current processing circuit 6 is used to transmit the current signal to the microcontroller and protection analysis and control unit 5 after reverse processing for current fault analysis. The high-precision current measurement unit 7 measures the received current signal.

[0028] Specifically, the current sampling circuit 1 includes a transformer CT1, a transformer CT2, and a transformer CT3, all of which are current sampling transformers. The transformer CT1 is inserted into the LA phase line of the circuit breaker, the transformer CT2 is inserted into the LB phase line of the circuit breaker, and the transformer CT3 is inserted into the LC phase line of the circuit breaker.

[0029] The rectification and current sampling circuit 2 includes three rectifier branches, a first rectifier branch, a second rectifier branch, and a third rectifier branch, each having the same circuit structure. The first rectifier branch is connected to the transformer CT1, the second rectifier branch is connected to the transformer CT2, and the third rectifier branch is connected to the transformer CT3. Specifically, the first rectifier branch includes a rectifier bridge composed of diodes D3, D4, D5, and D6, and sampling resistors R5 and R6. The sampling resistors R5 and R6 are respectively used for current sampling in the positive and negative half cycles of the LA phase line. The second rectifier branch includes a rectifier bridge composed of diodes D7, D8, D9, and D10, and sampling resistors R14 and R15. The sampling resistors R14 and R15 are respectively used for current sampling in the positive and negative half cycles of the LB phase line. The third rectifier branch includes a rectifier bridge formed by diodes D11, D12, D13 and D14, and sampling resistors R25 and R26. The sampling resistors R25 and R26 are used to sample the current of the positive and negative half cycles of the LC phase line respectively.

[0030] The current signals, rectified by the three rectifier branches, are input in parallel to the transformer power supply and voltage stabilization circuit 4. After voltage stabilization by the transformer power supply and voltage stabilization circuit 4, they provide power to the microcontroller and protection analysis and control unit 55. Simultaneously, sampling resistors on both arms of each rectifier branch convert the current signals into voltage signals. One path is directly supplied to the high-precision current measurement unit 77 for current measurement, while the other path is inverted by the protection current processing circuit 66 and supplied to the microcontroller and protection analysis and control unit 55 for current fault analysis, thus providing protection against overload, short-circuit, and other faults in the circuit breaker.

[0031] The auxiliary power supply and voltage sampling circuit 3 is composed of a resistor voltage dividing sampling circuit and a three-phase input switching power supply. Figure 2 As shown, resistors R29-R32 and R43 form the phase A voltage-dividing sampling subcircuit, resistors R33-R36 and R42 form the phase B voltage-dividing sampling subcircuit, and resistors R37-R40 and R41 form the phase C voltage-dividing sampling subcircuit. Diodes D16, D18, and D19 form a three-phase half-wave rectifier circuit, which is connected to the filter circuit consisting of capacitors C14-C17, inductor T1, and resistor R47 via composite varistor RV1. Resistors R44-R56, capacitors C10-C13, capacitors C18-C24, high-frequency transformer B1, and diodes D17, D20-D22 form a step-down switching power supply. The output of the switching power supply is the auxiliary power output.

[0032] The inputs of the auxiliary power supply and voltage sampling circuit 3 are connected to the LA, LB, and LC phases of the circuit breaker, respectively. The voltage sampling output of the auxiliary power supply and voltage sampling circuit 3 is connected to a high-precision current measurement unit 7. The auxiliary power supply output of the auxiliary power supply and voltage sampling circuit 3 is connected to the transformer power supply and voltage stabilization circuit 4. This circuit divides the circuit breaker's operating voltage into the voltage range required by the metering unit, allowing the metering unit to measure electrical parameters such as voltage, power, and energy. Furthermore, the auxiliary power supply is connected to the voltage stabilization output of the transformer power supply and voltage stabilization circuit 44 via diode D15, and then to the power input of the microcontroller and protection analysis control unit 55. The auxiliary power supply output is also connected to the positive terminal of the coil of relay K1. When the circuit breaker is operating normally, the normal output of the auxiliary power supply enables the electronic control circuit to operate normally. Simultaneously, relay K1 is properly energized, closing its normally open contacts and short-circuiting the positive and negative output terminals of the rectifier and current sampling circuit 2. This isolates the nonlinear components in the transformer power supply and voltage stabilization circuit 4 from the current sampling loop, preventing the nonlinear components from affecting current sampling. Because relay K1's contacts are purely resistive and have stable contact resistance, this ensures current sampling stability during the circuit breaker's normal operating conditions, thereby ensuring the accuracy of the circuit breaker's metering and protection. When tested according to national standards without normal operating voltage, the auxiliary power supply has no output voltage, and relay K1's coil also has no operating voltage. The normally open contacts remain open, allowing the transformer's output current to be rectified and input into the voltage stabilization circuit. After voltage stabilization, it is then output to the electronic control circuit, enabling normal operation.

[0033] The transformer power supply voltage stabilization circuit 4 includes a diode D1, a diode D15, a field effect transistor Q1, a voltage stabilization chip U1, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a capacitor C1, a capacitor C2, a capacitor C3, a transient suppression tube D2 and a relay K1. The positive electrode of the diode D1, the drain of the field effect transistor Q1, the negative electrode of the transient suppression tube D2 and one end of the normally open contact of the relay K1 are all connected to the positive output end of the rectification and current sampling circuit 2. One end of the resistor R1, one end of the capacitor C1, the cathode of the diode D15, and the anode of the capacitor C2 are all connected to the cathode of the diode D1; one end of the coil of the relay K1 and the anode of the diode D15 are all connected to the auxiliary power output of the auxiliary power supply and voltage sampling circuit 3; the other end of the normally open contact of the relay K1, the other end of the coil of the relay K1, the anode of the transient suppressor D2, the source of the field effect transistor Q2, one end of the resistor R3, the ground terminal of the voltage stabilizing chip U1, one end of the resistor R4, the other end of the capacitor C1, the cathode of the capacitor C2, and one end of the capacitor C3 are all connected to the negative output terminal of the rectifier and current sampling circuit 2. The gate of the field effect transistor Q1 is respectively connected to the other end of the resistor R3 and one end of the resistor R2; the other end of the resistor R2 is connected to the output of the voltage stabilizing chip U1; and the input of the voltage stabilizing chip U1 is respectively connected to the other end of the resistor R1, the other end of the resistor R4, and the other end of the capacitor C3. The positive electrode of the capacitor C2 is connected to the power input terminal of the microcontroller and the protection current sampling control unit as an output terminal, and the negative electrode of the capacitor C2 is connected to the ground terminal of the microcontroller and the protection current sampling control unit as a ground terminal.

[0034] Figure 3 This is a schematic diagram of the microcontroller and protection analysis and control unit 5. The circuit consists of resistor R57, capacitors C25-C33, ferrite bead L1, and microcontroller U3. The auxiliary power supply is connected to the microcontroller U3's power supply terminal VDDA via L1. The current sampling signals are connected to the microcontroller U3's six analog-to-digital conversion channels, ADC_IN0-ADC_IN5. The microcontroller U3 performs analog-to-digital conversion and analyzes the converted data. If fault data is detected, the corresponding protection output is activated. Microcontroller U3's synchronous serial interface SPI1 is connected to the high-precision measurement unit 7, reading its measurement data and configuring the corresponding parameters.

[0035] The protection current processing circuit 6 includes three processing branches, a first processing branch, a second processing branch and a third processing branch, which have the same circuit structure. The three processing branches are connected to the three rectifying branches in a one-to-one correspondence.

[0036] The first processing branch includes an inverting circuit formed by resistor R8, resistor R7, operational amplifier IC1B, resistor R9, and capacitor C4, and an inverting circuit formed by resistor R11, resistor R10, operational amplifier IC2B, resistor R12, and capacitor C5. One end of resistor R8 is connected to one end of sampling resistor R5, the other end of resistor R8 is respectively connected to one end of resistor R7 and the inverting input terminal of operational amplifier IC1B, the non-inverting input terminal of operational amplifier IC1B is grounded, and the output of operational amplifier IC1B is respectively connected to the other end of resistor R7, one end of capacitor C4, and one end of resistor R9. The other end of capacitor C4 is grounded, and the other end of capacitor R9 is output to the microcontroller and protection analysis control unit 5. One end of the resistor R11 is connected to one end of the sampling resistor R6, the other end of the resistor R11 is respectively connected to one end of the resistor R10 and the inverting input end of the operational amplifier IC2B, the non-inverting input end of the operational amplifier IC2B is grounded, the output end of the operational amplifier IC2B is respectively connected to the other end of the resistor R10, one end of the capacitor C5 and one end of the resistor R12, the other end of the capacitor C5 is grounded, and the other end of the capacitor R12 is output to the microcontroller and the protection analysis control unit 5.

[0037] The second processing branch includes an inverting circuit formed by resistor R16, resistor R13, operational amplifier IC1D, resistor R17, and capacitor C6, and an inverting circuit formed by resistor R19, resistor R18, operational amplifier IC2D, resistor R20, and capacitor C7. One end of resistor R16 is connected to one end of sampling resistor R14, the other end of resistor R16 is respectively connected to one end of resistor R13 and the inverting input terminal of operational amplifier IC1D, the non-inverting input terminal of operational amplifier IC1D is grounded, the output end of operational amplifier IC1D is respectively connected to the other end of resistor R13, one end of capacitor C6, and one end of resistor R17, the other end of capacitor C6 is grounded, and the other end of capacitor R17 is output to the microcontroller and protection analysis control unit 5. One end of the resistor R19 is connected to one end of the sampling resistor R15, and the other end of the resistor R19 is respectively connected to one end of the resistor R18 and the inverting input end of the operational amplifier IC2D. The non-inverting input end of the operational amplifier IC2D is grounded. The output end of the operational amplifier IC2D is respectively connected to the other end of the resistor R18, one end of the capacitor C7 and one end of the resistor R20. The other end of the capacitor C7 is grounded, and the other end of the capacitor R20 is output to the microcontroller and the protection analysis control unit 5.

[0038] The third processing branch includes an inverting circuit consisting of resistor R22, resistor R21, operational amplifier IC1C, resistor R23, and capacitor C8, and an inverting circuit consisting of resistor R27, resistor R24, operational amplifier IC2C, resistor R28, and capacitor C9. One end of resistor R22 is connected to one end of sampling resistor R25, the other end of resistor R22 is respectively connected to one end of resistor R21 and the inverting input terminal of operational amplifier IC1C, the non-inverting input terminal of operational amplifier IC1C is grounded, the output end of operational amplifier IC1C is respectively connected to the other end of resistor R21, one end of capacitor C8, and one end of resistor R23, the other end of capacitor C8 is grounded, and the other end of capacitor R23 is output to the microcontroller and protection analysis control unit 5. One end of the resistor R27 is connected to one end of the sampling resistor R26, the other end of the resistor R27 is respectively connected to one end of the resistor R24 ​​and the inverting input end of the operational amplifier IC2C, the non-inverting input end of the operational amplifier IC2C is grounded, the output end of the operational amplifier IC2C is respectively connected to the other end of the resistor R24, one end of the capacitor C9 and one end of the resistor R28, the other end of the capacitor C9 is grounded, and the other end of the capacitor R28 is output to the microcontroller and the protection analysis control unit 5.

[0039] Because the current sampling resistors are connected to the two arms of the negative terminal of the rectifier bridge, the sampled current signal is a negative level signal. This negative level signal cannot be used for digital analysis in the microcontroller. A level conversion circuit is required to convert the negative level signal into a positive level signal, which can be used for digital analysis in the microcontroller. Taking the LA phase current sampling channel as an example, the load current output by transformer CT1 is sampled through sampling resistors R5 and R6 on the two arms of the negative terminal of the rectifier bridge, respectively, to obtain the level signals of the positive and negative half-cycles of the load current. This negative level current signal is converted to a positive level current signal by the inverter circuits composed of IC1B, R7-R9, C4, and IC2B, R10-R12, C5, respectively. It is then connected to the two analog-to-digital conversion channels of the microcontroller and protection analysis control unit 5 for digital analysis. The current signal processing circuits for the LB and LC phases are based on the same principle as the current signal processing circuit for the LA phase. Although the overload short-circuit protection of a circuit breaker requires low current measurement accuracy, with a measurement error of no more than 10%, the protection action must respond quickly to abnormal short-circuit faults. Therefore, this embodiment inverts the positive and negative half-cycle fault current signals and simultaneously connects them to the analog-to-digital conversion channel of the microcontroller. The positive and negative half-cycle current signals are analyzed simultaneously to achieve rapid action.

[0040] The high-precision current measuring unit 7 is as follows Figure 4As shown, a dedicated metering chip is used as a high-precision current measurement unit. In this example, the Juquan HT7036 dedicated metering chip is used. It measures electrical parameters such as current, voltage, power, and energy, with a measurement error of no more than 0.5%. This circuit is a typical application circuit of the HT7036, and the specific circuit components are not described in detail here. It should be noted that in other embodiments of the present invention, the high-precision current measurement unit can also use dedicated metering chips from other companies and models.

[0041] The utility model utilizes the fact that when the circuit breaker is operating normally within the rated current range, the circuit breaker power supply side has a normal operating voltage. This operating voltage is used to provide an auxiliary working power supply for the circuit breaker's electronic control circuit. At the same time, this auxiliary power supply is used to control the operation of the shorting relay, short-circuiting the nonlinear components in the transformer power supply stabilizing circuit 4, thereby ensuring the internal resistance stability of the sampling circuit and thus ensuring the high precision requirements of current measurement. The regulated power supply composed of the nonlinear components in the transformer power supply stabilizing circuit 4 is only used to provide working power to the electronic control circuit when there is no normal operating voltage during testing according to national standards. Therefore, under normal operating conditions, the transformer power supply stabilizing circuit 4 can be short-circuited and isolated. Due to the nonlinear characteristics of the regulated power supply, in order to ensure the accuracy of full-range current sampling, the nonlinear components in the sampling circuit must be short-circuited and isolated. This ensures the accuracy of sampling within the entire measurement and protection current range, achieving high-precision electrical parameter measurement and accurate overload and short-circuit protection functions.

[0042] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope defined by the appended claims.

Claims

1. A single transformer high-precision current measurement and protection device, arranged between a primary circuit line and a load, characterized in that: The invention comprises a current sampling circuit (1), a rectification and current sampling circuit (2), an auxiliary power supply and voltage sampling circuit (3), a transformer power supply voltage stabilization circuit (4), a microcontroller and a protection analysis control unit (5), a protection current processing circuit (6) and a high-precision current measurement unit (7). The current sampling circuit (1) is used to collect current signals of each phase line of the circuit breaker and transmit them to the rectification and current sampling circuit (2). The rectification and current sampling circuit (2) transmits the current signals in parallel to the transformer power supply voltage stabilization circuit (4) after rectification processing. The transformer power supply voltage stabilization circuit (4) transmits the current signals to the microcontroller and the protection analysis control unit (5) after voltage stabilization processing. The rectification and current sampling circuit (2) is also connected to the protection current processing circuit (6) and the high-precision current measurement unit (7) respectively. The protection current processing circuit (6) is used to transmit the current signals to the microcontroller and the protection analysis control unit (5) after reverse processing for current fault analysis. The high-precision current measurement unit (7) performs current measurement on the received current signals.

2. A single transformer high-precision current measurement and protection device according to claim 1, characterized in that: The mutual inductor power supply voltage stabilization circuit (4) comprises a first diode, a second diode, a field effect transistor, a voltage stabilization chip, a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, a second capacitor, a third capacitor, a transient suppression tube and a relay, wherein the positive electrode of the first diode, the drain electrode of the field effect transistor, the negative electrode of the transient suppression tube and one end of the normally open contact of the relay are all connected to the positive output end of the rectification and current sampling circuit (2); one end of the first resistor, one end of the first capacitor, the negative electrode of the second diode and the positive electrode of the second capacitor are all connected to the negative electrode of the first diode; one end of the coil of the relay and the positive electrode of the second diode are all connected to the auxiliary power output end of the auxiliary power supply and voltage sampling circuit (3); the other end of the normally open contact of the relay and the other end of the coil of the relay are all connected to the auxiliary power output end of the auxiliary power supply and voltage sampling circuit (3); The positive electrode of the transient suppression tube, the source electrode of the field effect tube, one end of the third resistor, the ground end of the voltage stabilizing chip, one end of the fourth resistor, the other end of the first capacitor, the negative electrode of the second capacitor and one end of the third capacitor are all connected to the negative output end of the rectification and current sampling circuit (2); the gate electrode of the field effect tube is respectively connected to the other end of the third resistor and one end of the second resistor; the other end of the second resistor is connected to the output end of the voltage stabilizing chip; the input end of the voltage stabilizing chip is respectively connected to the other end of the first resistor, the other end of the fourth resistor and the other end of the third capacitor; the positive electrode of the second capacitor is connected as an output end to the power input end of the microcontroller and the protection current sampling control unit, and the negative electrode of the second capacitor is connected as a ground end to the ground end of the microcontroller and the protection current sampling control unit.

3. A single transformer high-precision current measurement and protection device according to claim 1 or 2, characterized in that: The input end of the auxiliary power supply and voltage sampling circuit (3) is respectively connected to the three phase lines of the circuit breaker, the voltage sampling output end of the auxiliary power supply and voltage sampling circuit (3) is connected to the high-precision current measurement unit (7), and the auxiliary power output end of the auxiliary power supply and voltage sampling circuit (3) is connected to the transformer power supply voltage stabilization circuit (4).

4. A single transformer high-precision current measurement and protection device according to claim 3, characterized in that: The auxiliary power supply and voltage sampling circuit (3) includes a resistor voltage-dividing sampling circuit and a three-phase input switching power supply. The resistor voltage-dividing sampling circuit includes three sampling subcircuits corresponding to three phase lines respectively, and each sampling subcircuit is composed of four resistors connected in series. The three-phase input switching power supply is composed of a rectifier unit, a filter unit, a transformer unit and a switching power supply unit.

5. A single transformer high-precision current measurement and protection device according to claim 1 or 2, characterized in that: The current sampling circuit (1) comprises a first mutual inductor, a second mutual inductor and a third mutual inductor, which are respectively inserted into three phase lines of the circuit breaker.

6. A single transformer high-precision current measurement and protection device according to claim 5, characterized in that: The rectification and current sampling circuit (2) comprises three first rectification branches, a second rectification branch and a third rectification branch with the same circuit structure, the three rectification branches are respectively connected to three mutual inductors in a one-to-one correspondence, and each rectification branch comprises a rectification bridge and a first sampling resistor and a second sampling resistor respectively connected to two bridge arms of the rectification bridge.

7. A single transformer high-precision current measurement and protection device according to claim 6, characterized in that: The protection current processing circuit (6) includes three first processing branches, a second processing branch, and a third processing branch with the same circuit structure, the three processing branches are connected to the three rectifier branches in a one-to-one correspondence, and each processing branch includes a first reverse circuit and a second reverse circuit; The first reverse circuit input end is connected to one end of the first sampling resistor, and the output end of the first reverse circuit is connected to the signal input end of the microcontroller and the protection analysis control unit (5); The second reverse circuit input end is connected to one end of the second sampling resistor, and the output end of the second reverse circuit is connected to the signal input end of the microcontroller and the protection analysis control unit (5).

8. The single transformer high-precision current measurement and protection device according to claim 7, characterized in that: The first inverting circuit and the second inverting circuit are both inverting circuits formed by operational amplifiers.

9. A single transformer high-precision current measurement and protection device according to claim 1 or 2, characterized in that: The microcontroller and the protection analysis control unit (5) are composed of a microcontroller and its peripheral circuits.

10. A single transformer high-precision current measurement and protection device according to claim 1 or 2, characterized in that: The high-precision current measurement unit (7) is a dedicated measurement chip.

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