A three-phase four-wire zero-loss detection device

Abstract

The utility model provides a kind of three-phase four-line zero-loss detection equipment, belong to zero-loss circuit technical field, including power conversion circuit, still have voltage sampling circuit, harmonic voltage acquisition circuit, comparison circuit, tripping control circuit;Power conversion circuit, voltage sampling circuit, harmonic voltage acquisition circuit, comparison circuit, tripping control circuit respectively have three paths, and install in component box.This new type is used for three-phase four-line power supply system's zero-loss detection and control, under the joint action of relevant circuit, by real-time comparison original phase voltage and after filtering voltage similarity, identify the third harmonic distortion caused by zero line loss, with the advantage of low hardware cost, strong anti-interference, can judge three-phase unbalance and three-phase balance when zero-loss fault, zero-loss can make for load power supply circuit breaker inside direct-current relay power-on, and then circuit breaker's tripping device tripping, circuit breaker tripping, improve zero-loss protection accuracy, and play strong technical support for safe power supply.

Description

Technical Field

[0001] This utility model relates to the field of testing equipment technology, and in particular to a three-phase four-wire zero-missing detection device. Background Technology

[0002] In a low-voltage three-phase four-wire power distribution system, the absence of a neutral wire can lead to severe voltage distortion on the load side, especially a significant increase in the third harmonic component, which may also cause electrical equipment damage, fires and other safety accidents.

[0003] Current methods for detecting zero-phase faults rely on comparing the three-phase voltage amplitudes for judgment. However, this circuit cannot distinguish between zero-phase faults and single-phase short-circuit faults. Specifically, when a short-circuit fault occurs in phase L1, it manifests as voltage imbalance characteristics of U_L1↓, U_L2↑, and U_L3↑. These characteristics overlap and are easily confused with the typical three-phase voltage imbalance characteristics of U_L1↑, U_L2↓, and U_L3↑ caused by a neutral wire breakage. This makes it impossible to identify zero-phase faults when the three phases are balanced, resulting in a high false alarm rate. On the secondary side of a Δ / Y connected transformer, when the neutral wire is broken and the three-phase load is completely balanced, the three-phase voltage can still maintain a false balance. In this case, the voltage amplitude comparison method completely fails, thus posing a certain safety hazard to the power supply. Utility Model Content

[0004] To overcome the shortcomings of existing technologies that determine zero-loss by comparing the three-phase voltage amplitudes for imbalance, as described in the background section, this invention provides a three-phase four-wire zero-loss detection device that, under the operation of relevant circuits, identifies third harmonic distortion caused by the absence of a neutral wire by comparing the similarity between the original phase voltage and the filtered voltage in real time. This device has advantages such as low hardware cost, strong anti-interference capability, and no need for a neutral wire signal. It can determine zero-loss faults in both three-phase imbalance and three-phase balance situations, improving the accuracy of zero-loss protection and providing strong technical support for safe power supply.

[0005] The technical solution adopted by this utility model to solve its technical problem is:

[0006] A three-phase four-wire neutral fault detection device includes a power conversion circuit, and further comprises a voltage sampling circuit, a harmonic voltage acquisition circuit, a comparison circuit, and a trip control circuit. Each of the power conversion circuit, voltage sampling circuit, harmonic voltage acquisition circuit, comparison circuit, and trip control circuit has three circuits, each installed in a component box. Each circuit is used in conjunction with one phase wire and one neutral wire of the three-phase four-wire power supply system. The power input terminal of each power conversion circuit is electrically connected to one phase wire and one neutral wire of the three-phase four-wire power supply system. The first power output terminal of each power conversion circuit is electrically connected to the first phase wire and the first neutral wire of each trip control circuit. The power input terminal is electrically connected; the second power output terminal of each power conversion circuit is electrically connected to the power input terminal of each voltage sampling circuit, each harmonic voltage acquisition circuit, and each comparison circuit; the neutral wire of the three-phase four-wire power supply system is electrically connected to the signal input terminal of each voltage sampling circuit and each harmonic voltage acquisition circuit; the signal output terminal of each voltage sampling circuit and each harmonic voltage acquisition circuit is electrically connected to the two signal input terminals of each comparison circuit; the signal output terminal of each comparison circuit is electrically connected to the signal input terminal of the tripping circuit; the control power output terminal of the three-way tripping circuit is electrically connected to the two terminals of the DC electromagnetic relay of the three-phase four-wire power supply system circuit breaker.

[0007] Furthermore, the power conversion circuit includes an AC-to-DC power supply module, a capacitor, a voltage regulator module, and a resistor that are electrically connected. The positive power output terminal of the AC-to-DC power supply module is connected to one end of the first capacitor and the positive power input terminal of the voltage regulator module. The positive power output terminal of the voltage regulator module is connected to one end of the second capacitor and one end of the first resistor. The other end of the first resistor is connected to one end of the second resistor and one end of the third capacitor. The negative power output terminal of the AC-to-DC power supply module is connected to the other end of the first capacitor, the negative power input terminal of the voltage regulator module, the other end of the second capacitor, the other end of the second resistor, and the other end of the third capacitor.

[0008] Furthermore, the voltage sampling circuit includes electrically connected resistors, capacitors, and operational amplifiers. One end of the first resistor is connected to one end of the second resistor, the other end of the second resistor is connected to one end of the third resistor, the other end of the third resistor is connected to one end of the fourth resistor, one end of the first capacitor, and the inverting input terminal of the operational amplifier, the output terminal of the operational amplifier is connected to the other end of the fourth resistor, the other end of the first capacitor, and one end of the fifth resistor, the other end of the fifth resistor is connected to one end of the second capacitor, and the other end of the second capacitor is connected to the negative power supply input terminal of the operational amplifier.

[0009] Furthermore, the harmonic voltage acquisition circuit includes electrically connected resistors, capacitors, operational amplifiers, and inductors. One end of the first resistor is connected to one end of the second resistor. The other end of the second resistor is connected to one end of the third resistor and one end of the fourth resistor. The other end of the fourth resistor is connected to one end of the fifth resistor, one end of the first capacitor, and the inverting input terminal of the operational amplifier. The output terminal of the operational amplifier is connected to the other end of the fifth resistor, the other end of the first capacitor, and one end of the sixth resistor. The other end of the sixth resistor is connected to one end of the second capacitor. The other end of the second capacitor is connected to the negative power input terminal of the operational amplifier and one end of the seventh resistor. The other end of the third resistor is connected to one end of the inductor. The other end of the inductor is connected to one end of the third capacitor and one end of the fourth capacitor. The other end of the seventh resistor is connected to the other ends of the third capacitor and the other ends of the fourth capacitor.

[0010] Furthermore, the comparison circuit includes an operational amplifier and a resistor that are electrically connected, with the output terminal of the operational amplifier and one end of the resistor connected.

[0011] Furthermore, the tripping control circuit includes an electrically connected capacitor, resistor, NPN transistor, and polarized capacitor. One end of the capacitor is connected to one end of the first resistor and the base of the transistor. The other end of the capacitor is connected to the other end of the first resistor, the emitter of the transistor, and the negative terminal of the polarized capacitor. The collector of the transistor is connected to one end of the second resistor.

[0012] Compared with existing technologies, the advantages of this invention are as follows: This invention is used for zero-line missing detection and control in three-phase four-wire power supply systems. Through the combined action of the power conversion circuit, voltage sampling circuit, harmonic voltage acquisition circuit, comparison circuit, and tripping control circuit, it identifies third harmonic distortion caused by the absence of a neutral wire by comparing the similarity between the original phase voltage and the filtered voltage in real time. It has the advantages of low hardware cost and strong anti-interference capability. It can determine zero-line missing faults in both three-phase imbalance and three-phase balance. When a zero line is missing, the DC relay inside the circuit breaker supplying power to the load is energized, causing the circuit breaker's trip unit to trip and the circuit breaker to trip, thus improving the accuracy of zero-line missing protection and providing strong technical support for safe power supply. Based on the above, this invention has good application prospects. Attached Figure Description

[0013] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0014] Figure 1 This is a structural block diagram of the present invention.

[0015] Figure 2 This is the circuit diagram of this utility model. Detailed Implementation

[0016] Figure 1 , 2As shown, a three-phase four-wire neutral detection device includes a power conversion circuit 1, and further comprises a voltage sampling circuit 2, a harmonic voltage acquisition circuit 3, a comparison circuit 4, and a trip control circuit 5. Each of these circuits—power conversion circuit 1, voltage sampling circuit 2, harmonic voltage acquisition circuit 3, comparison circuit 4, and trip control circuit 5—has three separate circuits installed in a component box. Each circuit is used in conjunction with one phase wire and one neutral wire of the three-phase four-wire power supply system. The following description uses a representative example of the working principle of one set of power conversion circuit 1, voltage sampling circuit 2, harmonic voltage acquisition circuit 3, comparison circuit 4, and trip control circuit 5.

[0017] Figure 1 , 2As shown, the power conversion circuit includes an AC-to-DC power module U1, capacitors C1 and C2, a voltage regulator module U2, and resistors R6 and R7 connected via circuit board wiring. The positive power output terminal 3 of the AC-to-DC power module U1 is connected to one end of the first capacitor C1 and the positive power input terminal 1 of the voltage regulator module U2. The positive power output terminal 3 of the voltage regulator module U2 is connected to one end of the second capacitor C2 and one end of the first resistor R6. The other end of the first resistor R6 is connected to one end of the second resistor R7 and one end of the third capacitor C5. The negative power output terminal 4 of the AC-to-DC power module U1 is connected to the other end of the first capacitor C1, the negative power input terminal 2 of the voltage regulator module U2, the other end of the second capacitor C2, the other end of the second resistor R7, and the other end of the third capacitor C3. The voltage sampling circuit includes resistors R1, R2, R3, R4, and R5, capacitors C3 and C4, and operational amplifier U5 connected via circuit board wiring. One end of the first resistor R1 is connected to one end of the second resistor R2. The other end of the second resistor R2 is connected to one end of the third resistor R3. The other end of the third resistor R3 is connected to one end of the fourth resistor R4, one end of the first capacitor C3, and pin 2 of the inverting input of operational amplifier U3. Pin 3 of the output of operational amplifier U3 is connected to the other end of the fourth resistor R4, the other end of the first capacitor C3, and one end of the fifth resistor R5. The other end of the fifth resistor R5 is connected to one end of the second capacitor C4. The other end of the second capacitor C4 is connected to pin 4 of the negative power input of operational amplifier U3. The harmonic voltage acquisition circuit includes resistors R8, R9, R10, R11, R12, R13, and R14, capacitors C6, C7, C8, and C9, operational amplifier U4, and inductor L1, all connected via circuit board wiring. One end of the first resistor R8 is connected to one end of the second resistor R9. The other end of the second resistor R9 is connected to one end of the third resistor R13 and one end of the fourth resistor R10. The other end of the fourth resistor R10 is connected to one end of the fifth resistor R11, one end of the first capacitor C6, and pin 2 of the inverting input of operational amplifier U4. Pin 3 of the output of operational amplifier U4 is also connected. The circuit consists of the following components: the other end of the fifth resistor R11, the other end of the first capacitor C6, and one end of the sixth resistor R12; the other end of the sixth resistor R12 is connected to one end of the second capacitor C7; the other end of the second capacitor C7 is connected to pin 4 of the negative power input of op-amp U4; one end of the seventh resistor R14; the other end of the third resistor R13 is connected to one end of inductor L1; the other end of inductor L1 is connected to one end of the third capacitor C8 and one end of the fourth capacitor C9; and the other end of the seventh resistor R14 is connected to the other ends of the third capacitor C8 and the fourth capacitor C9. The comparator circuit includes op-amp U5 and resistor R15 connected via circuit board wiring. The output terminal of op-amp U5 is connected to one end of resistor R15.The trip control circuit includes a capacitor C10, resistors R16 and R17, an NPN transistor Q1, and a polarized capacitor C11 connected via circuit board wiring. One end of capacitor C10 is connected to one end of the first resistor R16 and the base of transistor Q1. The other end of capacitor C10 is connected to the other end of the first resistor R16, the emitter of transistor Q1, and the negative terminal of polarized capacitor C11. The collector of transistor Q1 is connected to one end of the second resistor R17.

[0018] Figure 1 , 2 As shown, pins 1 and 2 of the AC-to-DC power module U1 at the power input terminal of each power conversion circuit are connected to one phase line N and the neutral line A of the three-phase four-wire power supply system via wires. Pin 3 of the AC-to-DC power module U1 at the first power output terminal of each power conversion circuit is connected to the positive terminal of the polarized capacitor C11 and the emitter of the transistor Q1 at the power input terminal of each trip control circuit via wires. Pins 3 and 2 of the voltage regulator module U2 at the second power output terminal of each power conversion circuit are connected to pins 8 and 4 of the operational amplifier U3 at the power input terminal of each voltage sampling circuit, pins 8 and 4 of the operational amplifier U4 at the power input terminal of each harmonic voltage acquisition circuit, and pins 8 and 4 of the operational amplifier U5 at the power input terminal of each comparator circuit via wires. The neutral line A of the three-phase four-wire power supply system is connected to the other end of the resistor R1 at the signal input terminal of each voltage sampling circuit and the other end of the resistor R8 at the signal input terminal of each harmonic voltage acquisition circuit via wires. One end of capacitor C4 at the signal output terminal of each voltage sampling circuit, one end of capacitor C7 at the signal output terminal of each harmonic voltage acquisition circuit, and pins 2 and 3 of operational amplifier U5 at the two signal input terminals of each comparator circuit are connected by wires. The other end of resistor R15 at the signal output terminal of each comparator circuit is connected to the base of transistor Q1 at the signal input terminal of the trip circuit by wires. The other end of resistor R17 at the control power output terminal of the three trip circuits, the positive terminal of polarized capacitor C11, and the two terminals of DC electromagnetic relay J of the three-phase four-wire power supply system circuit breaker (supplying power to the electrical load) are connected by wires.

[0019] Figure 1 , 2As shown, the three-phase four-wire system outputs 220V AC power from one neutral line (N) and one phase line (A). This power enters pins 1 and 2 of the AC-to-DC power supply module U1. Pins 3 and 4 of the AC-to-DC power supply module U1 then output a stable 12V DC power supply, which enters the positive and negative terminals of polarized capacitor C11 and the power input terminal of voltage regulator module U2 (capacitors C1 and C2 act as filters). Voltage regulator module U2 (with resistors R6 and R7 acting as voltage dividers and capacitor C5 acting as a filter to block high-frequency noise) outputs 3.3V DC power from pins 3 and 4, which enters the power input terminals of each voltage sampling circuit, each harmonic voltage acquisition circuit, and each comparator circuit. These circuits then operate. In the circuit, resistors R6 and... R7 acts as a voltage divider, stepping down the 3.3V to a 1.65V reference voltage, which then enters pin 3 of op-amps U3 and U4. In the voltage acquisition circuit, resistor R1 is connected to the 220VAC power supply line. Resistors R1 and R2 divide the 220VAC voltage. Op-amp U3, along with resistor R3 and capacitor C3, forms an integrating circuit, converting the time integration of the input signal into the output voltage. Resistor R4 eliminates voltage drift and bias current caused by temperature changes in the semiconductor circuitry. Resistor R5 and capacitor C4 form a low-pass filter to remove high-frequency noise before outputting to pin 2 of op-amp U5. In the harmonic voltage acquisition circuit, resistor R8 is connected to pin 2... A 20VAC power supply line is used. Resistors R8 and R9 divide the 220VAC voltage. Resistors R13 and R14, along with inductor L1 and capacitors C8 and C9, form a resonant circuit that filters out 150Hz harmonic components. Operational amplifier U4, along with resistor R10 and capacitor C6, forms an integrating circuit that converts the time integration of the input signal into the output voltage. Resistor R11 eliminates voltage drift and bias current caused by temperature changes in the semiconductor circuitry. Resistor R12 and capacitor C7 form a low-pass filter to remove high-frequency noise before outputting to terminal 3 of operational amplifier U5. Operational amplifier U5 can combine the voltage signal output from operational amplifier U3 and the voltage signal output from operational amplifier U4. The signal is compared and amplified. If a zero-loss fault occurs, the operational amplifier U5 (without input signal at pins 2 or 3) detects the difference in the input voltage signal and outputs a high level at pin 1 of the operational amplifier U5. The high level passes through resistor R15 and C10 to form a low-pass filter, filtering out high-frequency noise and preventing noise from affecting the trip circuit. When the 3.3V power supply output from pin 1 of the operational amplifier U5 is divided by R16 (higher than 0.7V) and enters the base of transistor Q1, transistor Q1 conducts and the collector outputs a low level, which is current-limited by resistor R17 and enters the DC electromagnetic relay J of the trip unit. Then, the DC electromagnetic relay J is energized and closes, the circuit breaker trips, the circuit breaker trips, and the electrical load stops working.

[0020] Figure 1 , 2As shown, the working principle of this new type is as follows: When the neutral wire is disconnected, the third harmonic component of the phase voltage is relatively large. The integrating circuit around operational amplifier U3 will convert the collected three-phase 220VAC voltage into a voltage of 0~3.3V and transmit it to operational amplifier U5. The circuit around RLC (resonant circuit) will filter out the third harmonic component of the voltage at this point. Then, the integrating circuit around operational amplifier U4 will convert the 220VAC voltage into a voltage of 0~3.3V and transmit it to operational amplifier U5. Operational amplifier U5 compares the input voltage at terminals 2 and 3 in real time, especially comparing the voltage data near the peak and trough. If a zero-loss fault occurs, operational amplifier U5 will output a 3.3V voltage through terminal 3 to trigger the trip circuit to conduct. The trip unit will cause the circuit breaker to trip.

[0021] Figure 2 In the diagram, AC to DC power module U1 is a finished product of AC 220V to DC 12V power module; voltage regulator module U2 is a finished product of DC 12V shaft 3.3V DC-DC power module; operational amplifiers U3, U4 and U5 are model TP6004-SR / 3PEAK; transistor Q1 is model BCX56-10. Figure 2 The model numbers of other electronic components have already been marked, so they will not be described again in this invention.

[0022] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. It will be apparent to those skilled in the art that this utility model is limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or basic characteristics of this utility model. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of this utility model is defined by the appended claims rather than the foregoing description, and thus all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this utility model.

[0023] Furthermore, it should be understood that although this specification describes the embodiments, the embodiments do not necessarily contain only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in the embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A three-phase four-wire zero-loss detection device, comprising a power conversion circuit, characterized in that, It also includes a voltage sampling circuit, a harmonic voltage acquisition circuit, a comparison circuit, and a trip control circuit; each of the power conversion circuit, voltage sampling circuit, harmonic voltage acquisition circuit, comparison circuit, and trip control circuit has three circuits, installed in a component box. Each power conversion circuit, voltage sampling circuit, harmonic voltage acquisition circuit, comparison circuit, trip control circuit, and one phase line of the three-phase four-wire power supply system is used in conjunction with the neutral line; the power input terminal of each power conversion circuit is electrically connected to one phase line of the three-phase four-wire power supply system and the neutral line, and the first power output terminal of each power conversion circuit is electrically connected to the power input terminal of each trip control circuit. The second power output terminal of the power conversion circuit is electrically connected to the power input terminals of each voltage sampling circuit, each harmonic voltage acquisition circuit, and each comparison circuit; the neutral wire of the three-phase four-wire power supply system is electrically connected to the signal input terminals of each voltage sampling circuit and each harmonic voltage acquisition circuit; the signal output terminals of each voltage sampling circuit and each harmonic voltage acquisition circuit are electrically connected to the two signal input terminals of each comparison circuit; the signal output terminal of each comparison circuit is electrically connected to the signal input terminal of the tripping circuit; the control power output terminal of the three-way tripping circuit is electrically connected to the two terminals of the DC electromagnetic relay of the three-phase four-wire power supply system circuit breaker.

2. The three-phase four-wire zero-miss detection device according to claim 1, characterized in that, The power conversion circuit includes an AC-to-DC power supply module, a capacitor, a voltage regulator module, and a resistor that are electrically connected. The positive power output terminal of the AC-to-DC power supply module is connected to one end of the first capacitor and the positive power input terminal of the voltage regulator module. The positive power output terminal of the voltage regulator module is connected to one end of the second capacitor and one end of the first resistor. The other end of the first resistor is connected to one end of the second resistor and one end of the third capacitor. The negative power output terminal of the AC-to-DC power supply module is connected to the other end of the first capacitor, the negative power input terminal of the voltage regulator module, the other end of the second capacitor, the other end of the second resistor, and the other end of the third capacitor.

3. The three-phase four-wire zero-miss detection device according to claim 1, characterized in that, The voltage sampling circuit includes electrically connected resistors, capacitors, and operational amplifiers. One end of the first resistor is connected to one end of the second resistor. The other end of the second resistor is connected to one end of the third resistor. The other end of the third resistor is connected to one end of the fourth resistor, one end of the first capacitor, and the inverting input terminal of the operational amplifier. The output terminal of the operational amplifier is connected to the other end of the fourth resistor, the other end of the first capacitor, and one end of the fifth resistor. The other end of the fifth resistor is connected to one end of the second capacitor. The other end of the second capacitor is connected to the negative power supply input terminal of the operational amplifier.

4. The three-phase four-wire zero-miss detection device according to claim 1, characterized in that, The harmonic voltage acquisition circuit includes electrically connected resistors, capacitors, operational amplifiers, and inductors. One end of the first resistor is connected to one end of the second resistor. The other end of the second resistor is connected to one end of the third resistor and one end of the fourth resistor. The other end of the fourth resistor is connected to one end of the fifth resistor, one end of the first capacitor, and the inverting input terminal of the operational amplifier. The output terminal of the operational amplifier is connected to the other end of the fifth resistor, the other end of the first capacitor, and one end of the sixth resistor. The other end of the sixth resistor is connected to one end of the second capacitor. The other end of the second capacitor is connected to the negative power input terminal of the operational amplifier and one end of the seventh resistor. The other end of the third resistor is connected to one end of the inductor. The other end of the inductor is connected to one end of the third capacitor and one end of the fourth capacitor. The other end of the seventh resistor is connected to the other ends of the third capacitor and the other ends of the fourth capacitor.

5. A three-phase four-wire zero-miss detection device according to claim 1, characterized in that, The comparator circuit includes an operational amplifier and a resistor that are electrically connected, with the output of the operational amplifier connected to one end of the resistor.

6. The three-phase four-wire zero-miss detection device according to claim 1, characterized in that, The tripping control circuit includes an electrically connected capacitor, resistor, NPN transistor, and polarized capacitor. One end of the capacitor is connected to one end of the first resistor and the base of the transistor. The other end of the capacitor is connected to the other end of the first resistor, the emitter of the transistor, and the negative terminal of the polarized capacitor. The collector of the transistor is connected to one end of the second resistor.

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