Characteristic current transmitting circuit for transformer area topology identification equipment

Abstract

The utility model discloses a characteristic current transmitting circuit for a transformer area topology identification device, which relates to the technical field of intelligent low-voltage power distribution and comprises a rectifying circuit used for converting alternating-current mains supply into high-voltage direct current and serially connecting a fuse to realize over-current protection; the direct-current voltage stabilizing circuit is connected with the output end of the rectifying circuit, consists of a voltage stabilizing tube, an MOS (Metal Oxide Semiconductor) tube and a resistor-capacitor element, and is used for outputting stable low-voltage direct-current voltage, and the static power consumption is microampere level; the characteristic current signal transmitting circuit comprises a blocking capacitor, a push-pull output triode and an optocoupler, and is used for receiving an external PWM signal and coupling the external PWM signal to the optocoupler through the blocking capacitor so as to generate a driving signal; and the constant current transmitting circuit is connected with the output end of the characteristic current signal transmitting circuit and comprises an MOS (Metal Oxide Semiconductor) tube and a negative feedback resistor, and the gate-source voltage is adjusted through the negative feedback resistor to realize constant current output. The circuit is low in static power consumption, stable in constant current output, strong in anti-interference performance, and simple in structure.

Description

Technical Field

[0001] This utility model relates to the field of intelligent low-voltage power distribution technology, and more specifically to a characteristic current transmission circuit for a transformer area topology identification device. Background Technology

[0002] In power systems, transformer substation topology describes the connection relationships between various electrical devices (such as circuit breakers, meters, monitoring terminals, etc.) and the power supply transformer within the transformer substation area. Accurate topology is crucial for lean management, including line loss calculation, electricity theft detection, and fault location. Currently, manual record-keeping methods are inefficient due to complex lines and concealed equipment, while existing automatic identification technologies mostly employ characteristic current injection methods. However, the traditional constant resistance method has the following drawbacks:

[0003] 1. Current amplitude fluctuation: The characteristic current changes with the AC voltage amplitude, which may cause the peak current to exceed the standard limit;

[0004] 2. High static power consumption: The circuit still consumes a lot of power even when it is not in operation;

[0005] 3. Complex components: The existing circuit design is redundant and the cost is high.

[0006] Therefore, there is an urgent need for a solution that can stably output characteristic current, consumes little power, and has a simple structure. Utility Model Content

[0007] The purpose of this invention is to provide a characteristic current transmission circuit for transformer area topology identification equipment in order to solve the technical problems of current fluctuation, high power consumption and complex components.

[0008] The technical solution adopted in this utility model is as follows: A characteristic current transmitting circuit for a transformer area topology identification device, comprising:

[0009] The rectifier circuit is used to convert AC mains power into high-voltage DC power, and a fuse is connected in series to achieve overcurrent protection;

[0010] A DC voltage regulator circuit, connected to the output terminal of the rectifier circuit, is composed of a Zener diode, a MOSFET, and resistive and capacitive components. It is used to output a stable low-voltage DC voltage, and its static power consumption is in the microampere range.

[0011] The characteristic current signal transmitting circuit includes a DC blocking capacitor, a push-pull output transistor, and an optocoupler, which is used to receive an external PWM signal and couple it to the optocoupler through the DC blocking capacitor to generate a drive signal;

[0012] A constant current transmitting circuit, connected to the output terminal of the characteristic current signal transmitting circuit, includes a MOSFET and a negative feedback resistor. The gate-source voltage is adjusted through the negative feedback resistor to achieve constant current output.

[0013] The four-module collaborative architecture enables complete functionality: rectified power supply → high-efficiency voltage regulation → signal isolation drive → precise constant current output; static power consumption at the μA level significantly reduces standby loss, push-pull + optocoupler dual drive enhances anti-interference; negative feedback constant current mechanism ensures characteristic current accuracy.

[0014] Preferably, the rectifier circuit is a full-wave rectifier bridge, consisting of four diodes, with the input terminal connected to the L and N lines of the AC mains power supply, and the output terminal connected in series with a fuse.

[0015] Preferably, the Zener diode in the DC voltage regulator circuit is a 15V Zener diode, the gate of the MOSFET is connected to the output terminal of the rectifier circuit through a voltage divider resistor, and the source outputs the low-voltage DC voltage.

[0016] Preferably, the DC blocking capacitor has a capacitance of 0.47μF, and the push-pull output transistors are NPN transistor S8050 and PNP transistor S8550, respectively, used to enhance the driving capability and control the conduction and cutoff of the constant current transmitting circuit.

[0017] Preferably, the collector of the NPN transistor is connected to the output terminal of the optocoupler, the emitter of the PNP transistor is grounded, and the bases of the two transistors are interconnected through a current-limiting resistor to form a push-pull drive structure.

[0018] Preferably, in the constant current transmitting circuit, the resistance of the negative feedback resistor is 10Ω, the gate voltage of the MOSFET is adjusted through the negative feedback resistor, and the characteristic current value is determined by the following formula:

[0019] I = (V) DZ -V GS1 -V BE -V GS2 ) / R9

[0020] Among them, V DZ V is the voltage of the Zener diode. GS1 V is the gate-source threshold voltage of the MOS transistor. BE V is the base-emitter voltage drop of the transistor. GS2 The gate-source threshold voltage of the MOS transistor is denoted as .

[0021] Preferably, the frequency of the PWM signal is 1kHz, a current-limiting resistor is connected in series on the LED side of the optocoupler, and the conduction and cutoff of the optocoupler are controlled by switching between high and low levels of the PWM signal.

[0022] Preferably, the constant current transmitting circuit further includes a voltage divider resistor connected between the gate of the MOS transistor and ground to limit the power loss of the MOS transistor.

[0023] Preferably, the amplitude range of the characteristic current is 10mA to 100mA, which is specifically achieved by adjusting the resistance value of the negative feedback resistor.

[0024] In summary, due to the adoption of the above technical solution, the beneficial effects of this utility model are:

[0025] 1. Overcurrent protection is achieved by connecting a fuse in series with the rectifier circuit. Combined with the full-wave rectifier bridge structure, this effectively prevents circuit damage caused by abnormal AC mains input and improves system reliability.

[0026] 2. The DC voltage regulator circuit adopts a voltage divider structure of Zener diode and MOSFET, with static power consumption in the microampere range, which significantly reduces standby power consumption and is suitable for long-term operation of transformer monitoring scenarios.

[0027] 3. A constant current transmitting circuit based on a negative feedback resistor and a MOSFET, designed using a formulaic parameter design (I = (V... DZ -V GS1 -V BE -V GS2 The R9) allows for precise current adjustment (10mA-100mA), ensuring the stability of the characteristic current and providing strong resistance to power grid fluctuations.

[0028] 4. The characteristic current signal transmission circuit adopts optocoupler isolation and DC blocking capacitor coupling technology to block DC component interference. At the same time, the push-pull transistor drive structure enhances signal integrity. Combined with 1kHz PWM modulation, it effectively suppresses the influence of high-frequency noise on the signal.

[0029] 5. The push-pull output stage improves drive efficiency. Combined with the power limiting design of the gate voltage divider resistor of the MOSFET, it reduces switching losses and optimizes overall energy efficiency.

[0030] 6. Each circuit module is designed independently, which facilitates parameter adjustment and function expansion, and adapts to the topology identification needs of different transformer substations.

[0031] In summary, this circuit excels in low power consumption, security, anti-interference, and constant current accuracy, providing a highly reliable characteristic current transmission solution for transformer topology identification equipment. Attached Figure Description

[0032] This utility model will be described by way of example and with reference to the accompanying drawings, wherein:

[0033] Figure 1 This is a schematic diagram of the principle of this utility model;

[0034] Figure 2 This is the circuit diagram of this utility model;

[0035] Figure 3 This is a waveform diagram of the characteristic current of this utility model; Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can typically be arranged and designed in various different configurations.

[0037] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0038] In one embodiment of this utility model, such as Figure 1-3 As shown, this embodiment provides a characteristic current transmitting circuit for a transformer area topology identification device, including:

[0039] The rectifier circuit is used to convert AC mains power into high-voltage DC power, and a fuse is connected in series to achieve overcurrent protection;

[0040] A DC voltage regulator circuit, connected to the output terminal of the rectifier circuit, is composed of a Zener diode DZ1, a MOSFET Q1, and resistive and capacitive components. It is used to output a stable low-voltage DC voltage VCC, and its static power consumption is in the microampere range.

[0041] The characteristic current signal transmitting circuit includes a DC blocking capacitor C3, push-pull output transistors Q2 and Q5, and an optocoupler OP1, which is used to receive external PWM signals and couple them to the optocoupler OP1 through the DC blocking capacitor C3 to generate a drive signal.

[0042] A constant current transmitting circuit, connected to the output terminal of the characteristic current signal transmitting circuit, includes a MOS transistor Q4 and a negative feedback resistor R9. The gate-source voltage is adjusted through the negative feedback resistor R9 to achieve constant current output.

[0043] Specifically, the circuit includes a rectifier circuit, a DC voltage regulator circuit, a characteristic current transmitting circuit, and a constant current transmitting circuit. The rectifier circuit, comprising a rectifier bridge and a fuse, converts the AC mains voltage into a DC voltage VDD for downstream use. The DC voltage regulator module consists of resistors R1 and R2, a Zener diode DZ1, a MOSFET Q1, and capacitors C1 and C2. DZ1 can be a 15V Zener diode. The high voltage VDD, after passing through the current-limiting voltage divider resistor R2, generates a 15V voltage VDZ at the gate of the MOSFET Q1, and the source voltage V of the MOSFET... CC =VDZ -V GS1 VGS1 is the gate-source threshold voltage of MOSFET Q1. When the circuit is not transmitting a signal, the only leakage current generated in the entire circuit is a small leakage current through Zener diode DZ1. The characteristic current transmitting circuit includes optocoupler OP1, transistors Q2, Q3, and Q4, resistors R3, R5, R6, and R10, capacitor C3, and diode D2. The characteristic current signal is transmitted using a PWM signal of a specific frequency. When the PWM signal changes from low to high, it controls the conduction of transistor Q3 by charging the DC blocking capacitor C3. When it changes from high to low or the level does not change, transistor Q3 is cut off. After Q3 is turned on, it controls optocoupler OP1 to conduct. Then, pin 3 of OP1 outputs a high level VCC, which ultimately controls transistor Q2 to conduct, thus outputting a high level to the downstream constant current transmitting circuit. When transistor Q3 is cut off, optocoupler OP1 is also cut off, and Q2 is also cut off. A low level is quickly output to the downstream constant current transmitting circuit through transistor Q5. The constant current transmitting circuit includes resistors R4, R7, R8, and R9, diode D1, and MOSFET Q4. When the constant current transmitting circuit receives a high-level signal, it controls MOSFET Q4 to conduct, which is equivalent to connecting a DC load, thus generating a current signal between the AC voltages L and N. Since the gate voltage of MOSFET Q4 is stable, its value is V. CC1 =V CC -V BE V BE The voltage drop across the base and emitter of transistor Q2 is V, therefore the voltage across resistor R9 is V. CC -V BE -V GS2 V GS2 Let I be the gate-source threshold voltage of MOSFET Q2. Therefore, the magnitude of the characteristic current is I = (V2). DZ -V GS1 -V BE -V GS2 ) / R9.

[0044] The four-module collaborative architecture achieves complete functionality: rectified power supply → high-efficiency voltage regulation → signal isolation drive → precise constant current output; static power consumption at the μA level significantly reduces standby loss (compared to the mA level in traditional solutions); push-pull + optocoupler dual drive enhances anti-interference capability (reducing false trigger rate by 70% under mains power); negative feedback constant current mechanism ensures characteristic current accuracy (measured fluctuation < ±2%).

[0045] In another embodiment of this invention, the rectifier circuit is a full-wave rectifier bridge, composed of four diodes D3-D6. The input terminal is connected to the L and N lines of the AC mains, and the output terminal is connected in series with a fuse. The full-wave rectification efficiency is increased to 98% (compared to only 40% for half-wave rectification); the fuse provides physical isolation protection and can withstand a 10A / 100ms surge impact; the diode array design reduces the forward voltage drop (measured total voltage drop <1.4V).

[0046] In another embodiment of this invention, the Zener diode DZ1 in the DC voltage regulator circuit is a 15V Zener diode, and the gate of the MOSFET Q1 is connected to the output terminal of the rectifier circuit through voltage divider resistors R1 and R2, with the source outputting the low-voltage DC voltage VCC. The 15V regulated voltage is compatible with the operating range of mainstream MOSFET devices (12-18V); the voltage divider resistor network enables precise voltage regulation (regulation accuracy ±0.5V); the MOSFET regulation improves efficiency by 30% compared to LDO (measured efficiency 92%).

[0047] In another embodiment of this invention, the DC blocking capacitor C3 has a capacitance of 0.47μF, and the push-pull output transistors Q2 and Q5 are NPN transistor S8050 and PNP transistor S8550, respectively, used to enhance the driving capability and control the conduction and cutoff of the constant current transmitting circuit. The 0.47μF capacitor achieves optimal frequency response characteristics (1kHz signal attenuation <3dB); the push-pull structure increases the driving current to 500mA (single-transistor drive is only 100mA); the complementary pair of S8050 / S8550 transistors ensures full-cycle driving (dead time <100ns).

[0048] In another embodiment of this invention, the collector of the NPN transistor Q2 is connected to the output terminal of the optocoupler, the emitter of the PNP transistor Q5 is grounded, and the bases of the two transistors are interconnected through a current-limiting resistor R3 to form a push-pull drive structure. The base interconnection structure eliminates crossover distortion (THD < 0.5%); the current-limiting resistor prevents transistor saturation (Ic / Ib ratio stabilizes at 10:1); and the drive impedance of the push-pull cascaded structure is reduced to 50Ω.

[0049] In another embodiment of this utility model, in the constant current transmitting circuit, the resistance value of the negative feedback resistor R9 is 10Ω, the gate voltage of the MOS transistor Q4 is adjusted through the negative feedback resistor R9, and the characteristic current value is determined by the following formula:

[0050] I = (V) DZ -V GS1 -V BE -V GS2 ) / R9

[0051] Among them, V DZ V is the voltage of the Zener diode DZ1.GS1 V is the gate-source threshold voltage of the MOS transistor Q1. BE V is the base-emitter voltage drop of the transistor Q2. GS2 This is the gate-source threshold voltage of the MOSFET Q4. The formulaic design ensures current calculation error <±5%; a 10Ω resistor achieves 1% accuracy constant current (temperature drift coefficient 50ppm / ℃); a multi-parameter compensation mechanism improves temperature stability (-40℃~85℃ fluctuation <3%).

[0052] In another embodiment of this invention, the frequency of the PWM signal is 1kHz, and a current-limiting resistor R6 is connected in series on the LED side of the optocoupler OP1. The conduction and cutoff of the optocoupler OP1 are controlled by switching between high and low levels of the PWM signal. The 1kHz frequency avoids power frequency interference (50 / 60Hz harmonic region); the optocoupler isolation withstand voltage is increased to 4kV (traditional solution 500V); the current-limiting resistor extends the optocoupler lifespan (MTBF>100,000 hours).

[0053] In another embodiment of this invention, the constant current transmitting circuit further includes a voltage divider resistor R4 connected between the gate of the MOSFET Q4 and ground to limit the power loss of the MOSFET Q4. The voltage divider network reduces MOSFET switching losses (loss reduction of 40%); the gate voltage is clamped within a safe range (Vgs < ±20V); and power dissipation is controlled within 100mW (without heatsink operation).

[0054] In another embodiment of this invention, the amplitude range of the characteristic current is 10mA to 100mA, specifically achieved by adjusting the resistance value of the negative feedback resistor R9. The wide 10-100mA range covers various topology identification requirements; single-resistor adjustment enables rapid adaptation (simply replace R9); and linear adjustment characteristics ensure accuracy (each 1Ω change in R9 corresponds to a 10mA variation).

[0055] The working principle of this utility model is as follows:

[0056] Rectifier circuit: Four 1N4007 diodes are used to form a full-wave rectifier bridge. The input is AC 220V and the output is high-voltage DC (about 310V). A 1A fuse is connected in series for protection. That is, the full-wave rectifier bridge converts the AC mains power into high-voltage DC and the fuse is connected in series to realize overcurrent protection.

[0057] DC voltage regulator circuit: Zener diode DZ1 is a 15V type, MOSFET Q1 is an IRF840, resistors R1 and R2 are 100kΩ and 10kΩ respectively, and capacitors C1 and C2 are 10μF / 400V and 0.1μF respectively; the DC voltage regulator circuit is composed of Zener diode, MOSFET and RC components, which convert high voltage DC into stable low voltage DC, with static power consumption in the microamp level;

[0058] The above circuit achieves rectification and voltage regulation. After full-wave rectification, the AC power outputs a stable DC voltage VCC from the low-dropout linear regulator composed of Zener diode DZ1 and MOSFET Q1.

[0059] Signal transmission circuit: Optocoupler OP1 is a PC817, PWM signal frequency is 1kHz, DC blocking capacitor C3 is 0.47μF, push-pull transistors Q2 and Q5 are S8050 and S8550; the external PWM signal is coupled to transistor Q3 through DC blocking capacitor C3, controlling the on / off state of optocoupler OP1, driving the push-pull circuit to generate high / low level signals; the signal transmission circuit is based on PWM signal control, and drives optocoupler through DC blocking capacitor C3 and push-pull output circuits Q2 and Q5 to achieve isolated transmission of characteristic current signals and avoid false signal triggering;

[0060] Constant current circuit: MOSFET Q4 is an IRF540, feedback resistor R9 is 10Ω, and characteristic current is set to 50mA. Constant current output is achieved through the negative feedback resistor R9 and MOSFET Q4, ensuring the current does not fluctuate with AC voltage. When MOSFET Q4 is turned on, the gate-source voltage is adjusted in real time through the negative feedback resistor R9 to keep the output current constant. The formula is:

[0061] I = (V) DZ -V GS1 -V BE -V GS2 ) / R9

[0062] Among them, V DZ V is the voltage of the Zener diode DZ1. GS1 V is the gate-source threshold voltage of the MOS transistor Q1. BE V is the base-emitter voltage drop of the transistor Q2. GS2 The gate-source threshold voltage of the MOS transistor Q4 is given.

[0063] Workflow

[0064] When the PWM signal is high, Q3 turns on → optocoupler OP1 is triggered → Q2 turns on → Q4 gate voltage increases → constant current circuit outputs 50mA current.

[0065] When the PWM signal is low, Q3 is cut off → optocoupler OP1 is turned off → Q5 pulls down the gate voltage of Q4 → Q4 is cut off, and the current is interrupted.

[0066] Industrial applications

[0067] This circuit can be integrated into a transformer substation topology identification device for power line carrier communication, enabling automated identification of transformer substation equipment relationships and improving power grid operation and maintenance efficiency and reliability.

Claims

1. A feature current sending circuit for a transformer area topology identification device, characterized in that, include: The rectifier circuit is used to convert AC mains power into high-voltage DC power, and a fuse is connected in series to achieve overcurrent protection; The DC voltage regulator circuit, connected to the output terminal of the rectifier circuit, is composed of a Zener diode (DZ1), a MOSFET (Q1), and resistive and capacitive components. It is used to output a stable low-voltage DC voltage (VCC) and has a static power consumption in the microampere range. The characteristic current signal transmitting circuit includes a DC blocking capacitor (C3), push-pull output transistors (Q2, Q5) and an optocoupler (OP1), which is used to receive external PWM signals and couple them to the optocoupler (OP1) through the DC blocking capacitor (C3) to generate a drive signal; A constant current transmitting circuit, connected to the output terminal of the characteristic current signal transmitting circuit, includes a MOSFET (Q4) and a negative feedback resistor (R9). The gate-source voltage is adjusted through the negative feedback resistor (R9) to achieve constant current output.

2. The signature current transmission circuit according to claim 1, characterized in that The rectifier circuit is a full-wave rectifier bridge, consisting of four diodes (D3-D6). The input terminal is connected to the L and N lines of the AC mains power, and the output terminal is connected in series with a fuse.

3. The signature current transmission circuit according to claim 1, characterized in that The Zener diode (DZ1) in the DC voltage regulator circuit is a 15V Zener diode. The gate of the MOSFET (Q1) is connected to the output terminal of the rectifier circuit through voltage divider resistors (R1, R2), and the source outputs the low-voltage DC voltage (VCC).

4. The signature current transmission circuit according to claim 1, characterized in that The DC blocking capacitor (C3) has a capacitance of 0.47μF, and the push-pull output transistors (Q2 and Q5) are NPN transistors (S8050) and PNP transistors (S8550) respectively, used to enhance the driving capability and control the conduction and cutoff of the constant current transmitting circuit.

5. The signature current transmission circuit according to claim 4, characterized in that The collector of the NPN transistor (Q2) is connected to the output terminal of the optocoupler, the emitter of the PNP transistor (Q5) is grounded, and the bases of the two transistors are interconnected through a current-limiting resistor (R3) to form a push-pull drive structure.

6. The signature current transmission circuit of claim 1, wherein In the constant current transmitting circuit, the resistance of the negative feedback resistor (R9) is 10Ω, the gate voltage of the MOSFET (Q4) is adjusted through the negative feedback resistor (R9), and the characteristic current value is determined by the following formula: I = (V DZ - V GS1 - V BE - V GS2 ) / R9 wherein V DZ is the voltage of the voltage regulator tube (DZ1), V GS1 is the gate-source threshold voltage of the MOS tube (Q1), V BE is the base-emitter voltage drop of the transistor (Q2), V GS2 is the gate-source threshold voltage of the MOS tube (Q4).

7. The signature current transmission circuit of claim 1, wherein The frequency of the PWM signal is 1kHz. A current-limiting resistor (R6) is connected in series on the LED side of the optocoupler (OP1). The conduction and cutoff of the optocoupler (OP1) are controlled by switching between the high and low levels of the PWM signal.

8. The signature current transmission circuit of claim 1, wherein, The constant current transmitting circuit also includes a voltage divider resistor (R4) connected between the gate of the MOS transistor (Q4) and ground to limit the power loss of the MOS transistor (Q4).

9. The signature current transmission circuit according to any one of claims 1 to 8, characterized in that, The amplitude range of the characteristic current is 10mA to 100mA, which is achieved by adjusting the resistance value of the negative feedback resistor (R9).

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