An electronic circuit breaker for transformer protection

Abstract

The electronic circuit breaker for transformer protection adopts current transformer to collect current signal, is isolated from circuit breaker loop, does not need to use bimetallic element protection, can reduce transformer low-voltage side loop resistance and reduce heat loss. At the same time, overload protection action is realized by using electronic method, the structural action error of bimetal itself is effectively avoided, the protection precision is improved, and the long-term stable and reliable operation of the transformer is beneficial.

Description

Technical Field

[0001] This invention relates to the field of power technology, and in particular to an electronic circuit breaker for transformer protection. Background Technology

[0002] A protective oil-immersed distribution transformer houses both the transformer core windings and the circuit breaker within a transformer tank. The tank is filled with insulating oil, which provides cooling and insulation for the transformer core windings and circuit breaker, and also serves as insulation and arc-extinguishing medium when the circuit breaker disconnects the low-voltage circuit. This facilitates rapid extinguishing of the opening arc. When the transformer is overloaded or exceeds normal operating conditions, the circuit breaker disconnects the low-voltage side circuit, providing overload protection. This prevents winding overheating, insulation aging, oil deterioration, and thermal breakdown faults, ensuring equipment safety and power supply reliability.

[0003] The existing overload protection of protective oil-immersed transformers mainly relies on circuit breakers installed inside the transformer. The circuit breaker has a thermocouple element. When the current flows through the thermocouple element on the low-voltage side of the transformer, the resistance of the thermocouple element causes it to bend due to heat. At the same time, due to the losses of the transformer windings themselves, the insulating oil inside the transformer heats up. The heat generated by the current passing through the thermocouple element and the temperature rise of the insulating oil cause the thermocouple element to bend and deform, thereby pushing the protection device to trip and disconnect the low-voltage circuit of the transformer, thus realizing the overload protection of the protective oil-immersed transformer.

[0004] This method has several drawbacks. First, its protection accuracy is not high, and due to the inherent characteristics of the thermal bimetallic element, its repeatability is poor, with an operating time error of up to ±50% and an operating temperature error of up to ±15℃. Second, because of the presence of the thermal bimetallic element, in order to ensure that its heat generation can enable the bimetallic bending and pushing mechanism to operate, its internal resistance is relatively high, resulting in a high circuit breaker circuit resistance and thus a high circuit breaker loss, which is detrimental to the energy conservation and environmental protection of the transformer.

[0005] Therefore, there is an urgent need for a transformer protection circuit breaker that reduces circuit breaker circuit resistance and has high-precision protection functions. Summary of the Invention

[0006] The technical problem to be solved by this application is to provide a transformer protection circuit breaker that can reduce the circuit resistance of the circuit breaker and has high-precision protection function.

[0007] This application discloses an electronic circuit breaker for transformer protection, including a current sensor, a tripping mechanism, a status detection module, a first temperature sensor, a second temperature sensor, a warning indicator light, an emergency overload detection module, and a controller.

[0008] The current sensor is used to detect the low-voltage side circuit current, the tripping mechanism is used to realize the circuit breaker tripping action, the status detection module is used to detect the circuit breaker opening and closing status, the first temperature sensor is used to detect the transformer top oil temperature, the second temperature sensor is used to detect the temperature of the circuit breaker current-carrying components, the warning indicator is used to indicate the warning status, and the emergency overload detection module is used to detect the position of the transformer's emergency overload wrench.

[0009] The controller is connected to the current sensor, the tripping mechanism, the status detection module, the first temperature sensor, the second temperature sensor, the warning indicator, and the emergency overload detection module. It is used to receive signals from the current sensor, the status detection module, the first temperature sensor, the second temperature sensor, and the emergency overload detection module, execute the transformer protection process, and output the warning indicator control signal and the tripping mechanism control signal.

[0010] According to some embodiments, the transformer protection process includes:

[0011] S10, the electronic circuit breaker is pre-loaded with the corresponding protection setting parameters;

[0012] S20, the controller detects the switch opening and closing positions through the status detection module and detects the transformer operating mode through the emergency overload detection module. The switch opening and closing positions include the switch closing position and the switch opening position. The transformer operating mode includes non-emergency overload state and emergency overload state. The controller collects the transformer low-voltage side circuit current I, transformer top oil temperature t1, and current-carrying component temperature t2 in real time through the current sensor, the first temperature sensor, and the second temperature sensor.

[0013] S30, if the transformer is in the closed position and I>Ir, where Ir is the overload current threshold, the controller outputs a warning indication signal and controls the warning indicator light to illuminate; otherwise, return to step S20.

[0014] S40, if the transformer is in the closed position and I>Ii, where Ii is the short-circuit current threshold, the controller outputs a control signal for the tripping mechanism to drive the tripping mechanism to perform protection tripping.

[0015] S50, if the transformer is in the closed position and Ii≥I>Ir, and the transformer is in a non-emergency overload state, then proceed to step S60; if the transformer is in the closed position and Ii≥I>Ir, and the transformer is in an emergency overload state, then proceed to step S70.

[0016] S60, if Δt>Δtgz, Δt=t2-t1, and Δtgz is the overload temperature difference threshold, then the controller outputs a control signal for the tripping mechanism to drive the tripping mechanism to perform protection tripping; otherwise, if t1>T1gz or t2>T2gz, and T1gz is the first overload temperature threshold and T2gz is the second overload temperature threshold, then the controller outputs a control signal for the tripping mechanism to drive the tripping mechanism to perform protection tripping.

[0017] S70, if Δt>Δtjj, Δt=t2-t1, and Δtjj is the emergency overload temperature difference threshold, then the controller outputs a control signal for the tripping mechanism to drive the tripping mechanism to perform protection tripping; otherwise, if t1>T1jj or t2>T2jj, T1jj is the first emergency overload temperature threshold, and T2jj is the second emergency overload temperature threshold, then the controller outputs a control signal for the tripping mechanism to drive the tripping mechanism to perform protection tripping.

[0018] According to some embodiments, the first overload temperature threshold is less than or equal to the first emergency overload temperature threshold, and the second overload temperature threshold is less than or equal to the second emergency overload temperature threshold.

[0019] According to some embodiments, the first overload temperature threshold ranges from 70°C to 105°C, the second overload temperature threshold ranges from 85°C to 115°C, the first emergency overload temperature threshold ranges from 85°C to 120°C, and the second emergency overload temperature threshold ranges from 100°C to 140°C.

[0020] According to some embodiments, the overload current threshold is taken as 1.2 times the rated current to 2 times the rated current, and the short-circuit current threshold is taken as 10 times the rated current to 25 times the rated current.

[0021] According to some embodiments, the overload temperature difference threshold ranges from 10°C to 25°C, and the emergency overload temperature difference threshold ranges from 15°C to 50°C.

[0022] According to some embodiments, the current sensor uses a current transformer to collect current signals, and the current sensor is isolated from the circuit breaker circuit.

[0023] According to some embodiments, the current sensor is isolated from the circuit breaker circuit through an operational amplifier circuit, wherein the operational amplifier is model GS6001.

[0024] According to some embodiments, the controller is composed of an MCU circuit, and the tripping mechanism is composed of a MOS transistor circuit.

[0025] According to some embodiments, the MCU model is ACM32F070, the MOSFET model is NCE2302, and the first temperature sensor and the second temperature sensor model are both MK1820-15.

[0026] The beneficial effects of this application are as follows:

[0027] The technical solution of this application uses a current transformer to collect current signals, which is isolated from the circuit breaker circuit. This eliminates the need for bimetallic element protection, reducing the resistance of the low-voltage side circuit of the transformer and minimizing heat loss. Simultaneously, the electronic overload protection mechanism effectively avoids the structural operational errors inherent in bimetallic elements, improving protection accuracy and contributing to the long-term stable and reliable operation of the transformer. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A block diagram of an electronic circuit breaker for transformer protection according to an example embodiment is shown.

[0030] Figure 2 A flowchart illustrating the operation of an electronic circuit breaker for transformer protection according to an example embodiment is shown.

[0031] Figure 3 A controller circuit diagram according to an example embodiment is shown.

[0032] Figure 4 A circuit diagram of a current sensor conditioning circuit according to an example embodiment is shown.

[0033] Figure 5 A circuit diagram of a temperature sensor according to an example embodiment is shown.

[0034] Figure 6 A circuit diagram of the tripping mechanism according to an example embodiment is shown.

[0035] Figure 7 The diagram illustrates a warning indicator light, an emergency overload detection, and a status detection circuit according to an example embodiment. Detailed Implementation

[0036] The embodiments of this application will now be described in detail with reference to the accompanying drawings. It should be understood that the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0037] Those skilled in the art should understand that the following specific embodiments or implementation methods are a series of optimized configurations listed in this application to further explain the specific application content. These configuration methods can be combined or used in conjunction with each other, unless this application explicitly states that some or a specific embodiment or implementation method cannot be associated with or used in conjunction with other embodiments or implementation methods. Furthermore, the following specific embodiments or implementation methods are only considered as optimized configurations and are not intended to limit the scope of protection of this application.

[0038] Example 1:

[0039] Figure 1 A block diagram of an electronic circuit breaker for transformer protection according to an example embodiment is shown.

[0040] like Figure 1 As shown, an electronic circuit breaker for transformer protection consists of a current sensor, a tripping mechanism, a status detection module, a first temperature sensor, a second temperature sensor, a warning indicator light, an emergency overload detection module, and a controller.

[0041] The controller connects to a current sensor, a tripping mechanism, a status detection module, a first temperature sensor, a second temperature sensor, an early warning indicator, and an emergency overload detection module. It receives signals from the current sensor, the status detection module, the first temperature sensor, the second temperature sensor, and the emergency overload detection module, executes the transformer protection process, and outputs control signals for the early warning indicator and the tripping mechanism.

[0042] Figure 3 A controller circuit diagram according to an example embodiment is shown. Figure 3As shown, U6 is an MCU microcontroller chip, the MCU model can be ACM32F070. Power-on reset is achieved through pull-up resistor R14 and filter capacitor C7. An external crystal oscillator Y1 and load capacitors C8 and C9 provide a stable external clock for the system. Pin 7 connects to the warning indicator circuit, outputting a warning indication control signal. Pin 10 connects to the current sensor conditioning circuit, receiving the conditioned and isolated current sensor signal. Pin 14 receives the output signal from the first temperature sensor, and pin 15 receives the output signal from the second temperature sensor. Pin 25 receives the output signal from the emergency overload detection circuit, and pin 22 receives the output signal from the status detection circuit. Pin 21 connects to the tripping action circuit, outputting the tripping action control signal. U7 is an EEPROM memory chip, the model can be FT24C64. U7 communicates with the MCU through the I2C interface (I2C1_SCL, I2C1_SDA) to store configuration data that is not lost when power is off. The WP pin is write-protected, and pull-up resistors R15 and R16 provide pull-up for the I2C bus to ensure stable communication.

[0043] The current sensor is used to detect the low-voltage side circuit current. Its current sensing adopts the method of current transformer and collects the low-voltage side circuit current signal through the principle of electromagnetic induction.

[0044] Figure 4 For current sensor conditioning circuits, such as Figure 4 As shown, J2, R5, R6, R7, Z1, and Z2 form the front-end input and protection circuit. J2 is the differential signal input interface; the current signal output from the current transformer is converted into a voltage signal by the sampling resistor and sent to J2. Z1 and Z2 are bidirectional Zener diodes used for overvoltage protection, clamping the input voltage within a safe range to prevent high voltage from damaging subsequent circuits. R5, R6, and R7 are current-limiting resistors, working with Z1 and Z2 to limit transient current and simultaneously forming the impedance matching network for the differential input. U3, R6, R7, R8, and R9 form the differential amplifier circuit. The non-inverting terminal is connected to the input signal through R7 and to the reference voltage VREF through R8. The inverting terminal is connected to the input signal through R6. R9 and C5 are connected in parallel to form a feedback network. Simultaneously, R9 and C5 in parallel form a low-pass filter and phase compensation, filtering out high-frequency noise and preventing operational amplifier self-oscillation. C4 and R8 in parallel filter out noise on VREF, ensuring a stable reference voltage. Operational amplifier U3 amplifies / attenuates the differential input signal and converts it to a single-ended signal. Simultaneously, it raises the DC bias via VREF, ensuring the signal falls entirely within the ADC input range of the controller circuit's MCU, and also isolates the current sensor from the circuit breaker circuit. The GS6001 operational amplifier can be selected. R10 and C6 form a first-order low-pass filter to remove high-frequency noise from the op-amp output, smooth the signal, and avoid ADC sampling errors. The output ADC_I is connected... Figure 3 Pin 10 of U6 in the controller circuit.

[0045] The first temperature sensor is used to detect the temperature of the top oil layer of the transformer. The second temperature sensor is used to detect the temperature of the current-carrying components of the circuit breaker. Figure 5 A circuit diagram of a temperature sensor according to an example embodiment is shown. Figure 5 As shown, U4 and R11 constitute the first temperature sensor circuit, and U5 and R12 constitute the second temperature sensor circuit. Both U4 and U5 are model MK1820-15.

[0046] The tripping mechanism is activated by the controller outputting a tripping signal to trip the circuit breaker. Figure 6 The circuit diagram of the tripping mechanism according to an example embodiment is shown, as follows: Figure 6 As shown, J1, D1, V1, R1, and C1 constitute the circuit for the tripping mechanism, and the MOSFET V1 can be an NCE2302.

[0047] Warning indicator lights are used to indicate the warning status. The status detection module is used to detect the circuit breaker's opening and closing status. The emergency overload detection module is used to detect the position of the transformer's emergency overload lever. When the emergency overload lever position is detected to be in the normal operating position, the circuit breaker operates according to the normal operating protection parameters; when the emergency overload lever position is detected to be in the emergency overload operating position, the circuit breaker operates according to the emergency overload operating protection parameters. Figure 7 This diagram illustrates a warning indicator light, an emergency overload detection circuit, and a status detection circuit according to an example embodiment. Figure 7 As shown, LED D2 and resistor R13 form a warning indicator circuit, sensor U1, resistor R3 and capacitor C2 form an emergency overload detection circuit, and sensor U2, resistor R4 and capacitor C3 form a status detection circuit.

[0048] Figure 2 A flowchart illustrating the operation of an electronic circuit breaker for transformer protection according to an example embodiment is shown. Figure 2 As shown, the circuit breaker's operating procedure is as follows:

[0049] S201, the circuit breaker has been pre-loaded with the corresponding protection settings parameters.

[0050] S202, the circuit breaker controller detects the switch's open and closed positions (including open and closed positions, normally it should be in the closed position) through a status detection module, and detects the transformer's operating mode (including emergency overload and non-emergency overload conditions) through an emergency overload detection module. The circuit breaker controller collects the transformer's low-voltage circuit current I, transformer top oil temperature t1, and current-carrying component temperature t2 in real time through a current sensor, a first temperature sensor, and a second temperature sensor.

[0051] S203. If the transformer is in the closed position and I>Ir, proceed to step S204; otherwise, return to step S202. Ir is the overload current threshold, and its typical value is 1.2-2 times the rated current.

[0052] S204, the controller controls the warning indicator light to light up and outputs a warning indication signal.

[0053] S205. If the transformer is in the closed position and I>Ii, then proceed to step S211; otherwise, proceed to step S206. Ii is the short-circuit current threshold, which is generally 10-25 times the rated current.

[0054] S206, The transformer's operating status is detected by the emergency overload detection module. If the transformer is in an emergency overload state, proceed to step S209; otherwise, proceed to step S207.

[0055] S207, determine whether the temperature difference Δt is greater than the overload temperature difference threshold Δtgz. If Δt > Δtgz, proceed to step S211; otherwise, proceed to step S208. Wherein, Δt = t2 - t1. The overload temperature difference threshold Δtgz is generally set within the range of 10℃ to 25℃. (This state occurs when a large fault current occurs in the low-voltage circuit. Due to the large current, the current-carrying components generate a large amount of heat, which cannot be quickly dissipated through the insulating oil, causing the temperature of the current-carrying components to rise rapidly. Consequently, the temperature of the current-carrying components is much higher than the temperature of the insulating oil. Therefore, to protect the low-voltage side circuit and prevent the current-carrying components from burning out due to excessive temperature, a rapid tripping action is required.)

[0056] S208, if t1>T1gz or t2>T2gz, then execute S211. Where T1gz is the first overload temperature threshold and T2gz is the second overload temperature threshold.

[0057] S209, if the temperature difference Δt is greater than the overload temperature difference threshold Δtjj, i.e., Δt>Δtjj, then proceed to step S211; otherwise, proceed to step S210. Generally, the emergency overload temperature difference threshold Δtjj is set within the range of 15℃ to 50℃.

[0058] S210, if t1>T1jj or t2>T2jj, then proceed to step S211. Here, T1jj is the first emergency overload temperature threshold, and T2jj is the second emergency overload temperature threshold. (This state occurs when a small overload current occurs in the low-voltage circuit. Due to the relatively small overload current, the heat generated by the current-carrying components is small, and the heat can be quickly dissipated into the transformer through the insulating oil. This causes the oil temperature inside the entire transformer to rise slowly, resulting in a small or even close temperature difference between the current-carrying components and the insulating oil. Under these circumstances, as long as the transformer oil temperature does not exceed the allowable value, the transformer can operate under overload. Only when the transformer temperature or the current-carrying components exceed the allowable value is a tripping action required to avoid transformer damage.)

[0059] S211, the circuit breaker immediately drives the tripping mechanism to achieve protection tripping.

[0060] Furthermore, the first overload temperature threshold setting should be less than or equal to the first emergency overload temperature threshold setting, i.e., T1gz≤T1jj, and the second overload temperature threshold setting should be less than or equal to the second emergency overload temperature threshold setting, i.e., T2gz≤T2jj.

[0061] Furthermore, the first overload temperature threshold setting is generally 70℃ to 105℃, the second overload temperature threshold setting is generally 85℃ to 115℃, the first emergency overload temperature threshold setting is generally 85℃ to 120℃, and the second emergency overload temperature threshold setting is generally 100℃ to 140℃.

[0062] In this embodiment, the current sensor uses a current transformer to collect current signals, isolating it from the circuit breaker circuit. This eliminates the need for the internal resistance heating of bimetallic components, reducing the resistance of the low-voltage side circuit of the transformer and minimizing heat loss. Simultaneously, overload protection is implemented electronically, effectively avoiding the structural operational errors inherent in bimetallic components and improving protection accuracy. This contributes to the long-term stable and reliable operation of the transformer.

[0063] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An electronic circuit breaker for transformer protection, characterized in that, It includes a current sensor, a tripping mechanism, a status detection module, a first temperature sensor, a second temperature sensor, a warning indicator, an emergency overload detection module, and a controller; The current sensor is used to detect the low-voltage side circuit current, the tripping mechanism is used to realize the circuit breaker tripping action, the status detection module is used to detect the circuit breaker opening and closing status, the first temperature sensor is used to detect the transformer top oil temperature, the second temperature sensor is used to detect the temperature of the circuit breaker current-carrying components, the warning indicator is used to indicate the warning status, and the emergency overload detection module is used to detect the position of the transformer's emergency overload wrench. The controller is connected to the current sensor, the tripping mechanism, the status detection module, the first temperature sensor, the second temperature sensor, the warning indicator, and the emergency overload detection module. It is used to receive signals from the current sensor, the status detection module, the first temperature sensor, the second temperature sensor, and the emergency overload detection module, execute the transformer protection process, and output the warning indicator control signal and the tripping mechanism control signal.

2. The electronic circuit breaker for transformer protection according to claim 1, characterized in that, The transformer protection process includes: S10, the electronic circuit breaker is pre-loaded with the corresponding protection setting parameters; S20, the controller detects the switch opening and closing positions through the status detection module and detects the transformer operating mode through the emergency overload detection module. The switch opening and closing positions include the switch closing position and the switch opening position. The transformer operating mode includes non-emergency overload state and emergency overload state. The controller collects the transformer low-voltage side circuit current I, transformer top oil temperature t1, and current-carrying component temperature t2 in real time through the current sensor, the first temperature sensor, and the second temperature sensor. S30, if the transformer is in the closed position and I>Ir, where Ir is the overload current threshold, the controller outputs a warning indication signal and controls the warning indicator light to illuminate; otherwise, return to step S20. S40, if the transformer is in the closed position and I>Ii, where Ii is the short-circuit current threshold, the controller outputs a control signal for the tripping mechanism to drive the tripping mechanism to perform protection tripping. S50, if the transformer is in the closed position and Ii≥I>Ir, and the transformer is in a non-emergency overload state, then proceed to step S60; if the transformer is in the closed position and Ii≥I>Ir, and the transformer is in an emergency overload state, then proceed to step S70. S60, if Δt>Δtgz, Δt=t2-t1, and Δtgz is the overload temperature difference threshold, then the controller outputs a control signal for the tripping mechanism to drive the tripping mechanism to perform protection tripping; otherwise, if t1>T1gz or t2>T2gz, and T1gz is the first overload temperature threshold and T2gz is the second overload temperature threshold, then the controller outputs a control signal for the tripping mechanism to drive the tripping mechanism to perform protection tripping. S70, if Δt>Δtjj, Δt=t2-t1, and Δtjj is the emergency overload temperature difference threshold, then the controller outputs a control signal for the tripping mechanism to drive the tripping mechanism to perform protection tripping; otherwise, if t1>T1jj or t2>T2jj, T1jj is the first emergency overload temperature threshold, and T2jj is the second emergency overload temperature threshold, then the controller outputs a control signal for the tripping mechanism to drive the tripping mechanism to perform protection tripping.

3. The electronic circuit breaker for transformer protection according to claim 2, characterized in that, The first overload temperature threshold is less than or equal to the first emergency overload temperature threshold, and the second overload temperature threshold is less than or equal to the second emergency overload temperature threshold.

4. The electronic circuit breaker for transformer protection according to claim 3, characterized in that, The first overload temperature threshold ranges from 70°C to 105°C, the second overload temperature threshold ranges from 85°C to 115°C, the first emergency overload temperature threshold ranges from 85°C to 120°C, and the second emergency overload temperature threshold ranges from 100°C to 140°C.

5. The electronic circuit breaker for transformer protection according to claim 2, characterized in that, The overload current threshold is set at 1.2 times to 2 times the rated current, and the short-circuit current threshold is set at 10 times to 25 times the rated current.

6. The electronic circuit breaker for transformer protection according to claim 2, characterized in that, The overload temperature difference threshold ranges from 10℃ to 25℃, and the emergency overload temperature difference threshold ranges from 15℃ to 50℃.

7. The electronic circuit breaker for transformer protection according to claim 1, characterized in that, The current sensor uses a current transformer to collect current signals, and the current sensor is isolated from the circuit breaker circuit.

8. The electronic circuit breaker for transformer protection according to claim 7, characterized in that, The current sensor is isolated from the circuit breaker circuit through an operational amplifier circuit, and the operational amplifier model is GS6001.

9. The electronic circuit breaker for transformer protection according to claim 1, characterized in that, The controller is composed of an MCU circuit, and the tripping mechanism is composed of a MOS transistor circuit.

10. The electronic circuit breaker for transformer protection according to claim 9, characterized in that, The MCU model is ACM32F070, the MOSFET model is NCE2302, and the first temperature sensor and the second temperature sensor model are both MK1820-15.

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