Electric leakage and overcurrent protection device and method

Abstract

The invention relates to the technical field of power control, and provides an electric leakage and overcurrent protection device and method.The leakage current signal is monitored in real time through a current detection module, amplification, filtering and analog-to-digital conversion are conducted on the detected leakage current signal, and the leakage current signal is transmitted to a control module; the control module carries out three-phase current signal vector sum calculation on the leakage current signal, judges and displays the state of a cable, controls air switch tripping, divides the current signal into four sections, namely unbalanced current, leakage current, working current and short-circuit current, realizes insulation monitoring of the whole-interval alternating-current loop cable, and realizes insulation monitoring of the whole-interval alternating-current loop cable. Mistaken switching-on and switching-off risks of the isolating switch caused by a cable insulation problem are eliminated; and various types of alternating-current loop abnormities and faults can be sensed, and the alternating-current loop is protected. A worker can flexibly set a current threshold through an independent key, and a real-time display module is convenient for monitoring a circuit state. And the electromagnetic coil and the NPN transistor are combined, so that quick tripping is ensured when a fault occurs, and the risk is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of power control, and in particular to a leakage and overcurrent protection device and method. Background Art

[0002] An isolating switch is an electrical device used to isolate a circuit from the power supply in an electrical network. Its main function is to ensure safety, especially when servicing or maintenance is required. An isolating switch allows a circuit to be connected or disconnected without current flowing, which prevents the accidental flow of current and ensures the safety of personnel and equipment.

[0003] In actual use, in order to avoid the AC short circuit caused by aging of cable insulation and the mistaken connection of the isolation switch circuit, the isolation switch operating power supply is always in the disconnected state.

[0004] However, with the advancement of the digital transformation of China Southern Power Grid, the program operation transformation has gradually covered the production line. The main function of the program operation is to be able to remotely control the equipment to switch between operation, hot standby and cold standby states. It is inevitable to put the isolating switch operating power supply into the operation state, which makes the requirements for the insulation state of the AC cable higher. The AC cables in old substations are damaged and grounded, and short circuits are common. Because there is no real-time monitoring of the AC cable status, as long as the circuit breaker does not trip, the problem cannot be found, which further increases the risk of mis-opening and closing of the isolating switch. The following urgent problems exist on site: 1. The insulation status of the AC cable cannot be monitored and leakage is common; 2. If leakage is not handled for a long time, it will gradually develop into multi-point grounding or phase-to-phase short circuit, causing the risk of mis-opening and mis-closing of the isolating switch to increase sharply; 3. The circuit breakers in substations generally adopt the extreme difference coordination method. The extreme difference coordination method is to use multi-level circuit breakers in the substation. The capacity of each level of circuit breakers gradually decreases. When a fault occurs, the circuit breaker with the lowest capacity begins to trip until the fault interval is isolated. Normal operation requires the circuit breaker to remain stable, but when the cable insulation is abnormal, the current may not reach the tripping standard, but it is enough to cause the disconnector to operate incorrectly. However, the cable insulation abnormality at this time is acceptable within a certain limit. In this case, the disconnector should not be opened or closed, but in actual operation, it often occurs by mistake.

[0005] In summary, with the advancement of digital transformation and programmed operation of China Southern Power Grid, it is inevitable to put the isolating switch operating power supply into operation, which puts higher requirements on the monitoring and maintenance of the cable insulation status. While ensuring the timely discovery of abnormal insulation status of AC cables, reducing the risk of misoperation and maintaining the stable operation of the power system, it is urgent to improve the real-time monitoring capability of the insulation status of AC cables and improve the protection strategy of the distribution system to ensure the safe and stable operation of the power system. Based on this, the present invention proposes a leakage and overcurrent protection device and method. Summary of the invention

[0006] The purpose of the present invention is to solve the deficiencies of the prior art and to provide a leakage and overcurrent protection device and method so as to ensure timely detection of abnormal insulation status of an AC cable while reducing the risk of misoperation and maintaining stable operation of the power system.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: A leakage and overcurrent protection device, comprising: a current detection module, a control module, a trip module and a power supply module; A current detection module is used to detect three-phase line current signals, amplify the detected current signals, filter the amplified current signals, convert the filtered current signals into digital signals and transmit the digital signals to the control module; The control module is used to receive the current signal output by the current detection module, calculate the vector sum of the three-phase current signal, compare the current signal with the interval current signal, and divide the current signal into four intervals, which are an unbalanced current interval, an abnormal current interval, a working current interval, and a short-circuit current interval; When the current signal is in the abnormal current interval and the short-circuit current interval, the control module controls the trip module to trip; when the current signal is in the unbalanced current interval and the working current interval, the control module controls the trip module not to act; The tripping module is used to drive the circuit breaker to trip under the control of the control module; Display module, used to display cable status; The power module is used to supply power to the current detection module, the control module and the trip module.

[0008] Preferably, the current detection module comprises current detection submodules respectively arranged on the three phases A, B and C, and the current signals of the three phases A, B and C are respectively input into the control module.

[0009] Preferably, the current detection submodule includes a current transformer, an operational amplifier, a first resistor-a sixth resistor, a first capacitor-a third capacitor, a first diode, a second diode and an analog-to-digital converter; pin 2 of the current transformer is connected to one end of the third resistor, the idle end of the third resistor is connected to pin 3 of the operational amplifier, pin 1 of the current transformer is connected to one end of the sixth resistor, the idle end of the sixth resistor is connected to pin 4 of the operational amplifier, one end of the fourth resistor is connected between pin 2 of the current transformer and the third resistor, the other end of the fourth resistor is connected between pin 1 of the current transformer and the sixth resistor, and the first capacitor is connected in parallel at both ends of the fourth resistor; the third resistor is connected to one end of the first resistor between pin 3 of the operational amplifier, and the other end of the first resistor is connected to the bias voltage The operational amplifier pin 1 is connected to one end of the fifth resistor, and the other end of the fifth resistor is connected to the power supply and the analog-to-digital converter; one end of the second resistor is connected between the pin 4 of the operational amplifier and the sixth resistor, the other end of the second resistor is connected between the pin 1 of the operational amplifier and the fifth resistor, and the pin 5 of the operational amplifier is connected to the power supply; a first diode is provided between the fifth resistor and the power supply; the third capacitor is connected between the pin 5 of the operational amplifier and the ground to play a decoupling role; one end of the second capacitor is connected between the fifth resistor and the analog-to-digital converter, and the other end of the second capacitor is grounded to filter and reduce high-frequency noise; the operational amplifier pin 2 and the current transformer pin 1 are grounded; a second diode is connected in parallel at both ends of the second capacitor to absorb static electricity.

[0010] Preferably, the bias voltage is provided by a 1.25V voltage reference circuit, in which the reference voltage chip is REF3030; the power supply is provided by a 3V reference circuit, in which the reference voltage chip is REF3012; coupling capacitors are provided in both the 1.25V reference circuit and the 3V reference circuit to reduce interference from power supply noise.

[0011] Preferably, the control module main chip adopts an STM32 single-chip microcomputer, the STM32 single-chip microcomputer provides a clock signal through a crystal oscillator circuit, and is debugged and programmed through a joint test action group interface.

[0012] Preferably, the control module is also provided with a display module, and the display module is used to display current leakage current information.

[0013] Preferably, the control module is provided with four independent buttons, and the leakage current threshold is designed by pressing the buttons.

[0014] Preferably, the tripping module includes an electromagnetic coil, an NPN transistor, a seventh resistor, an eighth resistor, a ninth resistor, and a Coil1 interface. The electromagnetic coil is used to attract the armature to drive the circuit breaker to trip. One end of the ninth resistor is connected to a 5V power supply, and the other end of the ninth resistor is connected to the input end of the electromagnetic coil. The ground end of the electromagnetic coil is connected to the collector of the NPN transistor, the emitter of the NPN transistor is grounded, the base of the NPN transistor is connected to the Coil1 interface, and the Coil1 interface is connected to the output interface of the control module. When Coil1 receives a high level, the NPN transistor is turned on, and at the same time, the electromagnetic coil attracts the armature to drive the circuit breaker to trip. An eighth resistor is connected in series between the Coil1 interface and the output interface of the control module, one end of the seventh resistor is connected between the eighth resistor and the base of the NPN transistor, and the other end of the seventh resistor is grounded.

[0015] Another object of the present invention is to provide a method for performing leakage and overcurrent protection using the leakage and overcurrent protection device, comprising the following steps: S1, the device is started, and the staff sets the interval current signal, I1, I2, I3, through four independent buttons. The interval current signals I1, I2, I3 divide the current signal into four intervals, which are 0-I1 unbalanced current interval, I1-I2 abnormal current interval, I2-I3 working current interval, and greater than I3 short-circuit current interval; S2, obtaining current signals, respectively obtaining three-phase current signals; S3, calculating the vector sum of three-phase current signals; S4, judge and display the cable status, and control the circuit breaker operation; If the vector sum is zero, it is determined that there is no leakage and the circuit breaker does not operate. At the same time, the insulation of the output cable of the control module control display screen is normal; the actual current is compared with the interval current signals I1, I2, and I3, and the actual current is divided into four intervals; If the current signal is placed in the unbalanced current range and the working current range, the circuit breaker does not operate, and the insulation of the output cable of the control module control display screen is normal; If the current signal is placed in the abnormal current interval, the control module controls the trip module to output a high level to control the trip module to drive the circuit breaker to trip, and at the same time, the control module controls the display screen to output a cable insulation fault; If the current signal is placed in the short-circuit current range, the control module outputs a high level to the trip module to control the trip module to drive the circuit breaker to trip. At the same time, the control module controls the display screen to output a phase-to-phase short-circuit fault.

[0016] Preferably, in step S1, the constant value of I1 is relatively small to avoid malfunction of the tripping module caused by current fluctuations due to imbalance; the constant value of I2 is slightly smaller than the rated opening and closing current of the isolating switch to avoid the rated opening and closing current of the isolating switch; the constant value of I3 is slightly larger than the rated opening and closing current of the isolating switch to prevent short circuits of the live wire and the neutral wire in the vicinity, short circuits between phases and other large currents.

[0017] The present invention discloses a leakage and overcurrent protection device and method having the following beneficial effects.

[0018] The present invention monitors the leakage current signal in real time through the current detection module, and amplifies, filters, converts the detected leakage current signal into analog and digital form, and transmits it to the control module. The control module performs three-phase current signal vector sum calculation on the leakage current signal, judges and displays the cable status, controls the circuit breaker tripping, and divides the current signal into four intervals: unbalanced current, leakage current, working current, and short-circuit current, so as to realize the insulation monitoring of the AC circuit cable of the entire interval, eliminate the risk of mis-opening and closing of the isolating switch due to cable insulation problems; it can sense various types of AC circuit abnormalities and faults, and protect the AC circuit. The staff can flexibly set the current threshold through independent buttons, and the real-time display module is convenient for monitoring the circuit status. Combined with the electromagnetic coil and NPN transistor, it ensures rapid tripping in the event of a fault and reduces the risk. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of the leakage and overcurrent protection device of the present invention.

[0020] Figure 2 This is a circuit diagram of the current detection submodule of the present invention.

[0021] Figure 3 The 2.5V reference circuit and the 3V reference circuit diagram of the present invention are shown in FIG.

[0022] Figure 4 It is the circuit diagram of the control module of the present invention.

[0023] Figure 5 It is the circuit diagram of the trip module of the present invention.

[0024] Figure 6 This is a flow chart of the leakage and overcurrent protection method of the present invention.

[0025] In the attached figure: 1, current detection module; 2, control module; 3, trip module; 4, power module; U1, current transformer; U2, operational amplifier; U3, electromagnetic coil; R1, first resistor; R2, second resistor; R3, third resistor; R4, fourth resistor; R5, fifth resistor; R6, sixth resistor; R7, seventh resistor; R8, eighth resistor; R9, ninth resistor; C1, first capacitor; C2, second capacitor; C3, third capacitor; D1, first diode; D2, second diode; ADC, analog-to-digital converter; Q1, NPN transistor. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0027] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. Example 1

[0028] Please refer to Figure 1 , a leakage and overcurrent protection device, comprising: a current detection module 11, a control module 2, a trip module 3 and a power module 4; The current detection module 11 has the main function of detecting the three-phase line current signal in real time, amplifying the detected current signal to ensure that the signal strength can meet the requirements of subsequent processing and analysis, filtering the amplified current signal to remove unnecessary noise and interference to obtain a pure signal, converting the filtered current signal into a digital signal and transmitting the digital signal to the control module 2. The signal output end of the current detection module 11 is connected to the control module 2 through a signal line; The control module 2 is used to receive the current signal output by the current detection module 11, that is, the control module 2 receives the digital signal from the current detection module 11, calculates the vector sum of the three-phase current signal after receiving the signal, and then compares it with the interval current signal, and divides the current signal into four intervals, which are an unbalanced current interval, an abnormal current interval, a working current interval, and a short-circuit current interval; When the current signal is in the abnormal current interval and the short-circuit current interval, the control module 2 controls the trip module 3 to trip; when the current signal is in the unbalanced current interval and the working current interval, the control module 2 controls the trip module 3 not to act; The tripping module 3 is used to drive the circuit breaker to trip under the control of the control module 2; The display screen uses OLED display to display the cable status. If the vector sum is zero, the control module 2 controls the display screen output cable insulation to be normal; If the current signal is placed in the unbalanced current interval, the control module 2 controls the display screen output cable insulation to be normal; If the current signal is placed in the abnormal current interval, the control module 2 controls the display screen output cable insulation fault; If the current signal is placed in the short-circuit current interval, the control module 2 controls the display screen to output a phase-to-phase short-circuit fault.

[0029] The power supply module 4 is used to supply power to the current detection module 11 , the control module 2 , and the trip module 3 .

[0030] The current detection module 11 includes current detection submodules respectively arranged on the three phases A, B and C. The current signals of the three phases A, B and C are respectively input into the control module 2 .

[0031] In this embodiment, the current detection module 11 can monitor the three-phase current signal in real time, and ensure the strength and purity of the signal through amplification and filtering, providing a reliable data basis for subsequent analysis. The control module 2 calculates the vector sum of the current signal and compares it with the preset interval to intelligently identify the current state, thereby improving the response speed and accuracy of abnormal situations. The current signal is divided into unbalanced current, abnormal current, working current and short-circuit current intervals, allowing the system to take appropriate measures for different situations. When an abnormal or short-circuit current is detected, the control module 2 quickly instructs the trip module 3 to act, cut off the circuit, and protect the safety of the equipment and lines. Through the OLED display, the user can intuitively view the cable status, including normal insulation, insulation fault and phase-to-phase short-circuit fault, which is convenient for timely response. The modular design of the current detection module 11 realizes the independent detection of the three-phase current, improves the flexibility of the system, and the power module 4 provides stable power support to ensure the continuous and stable operation of each module. In general, the device effectively monitors, analyzes and responds to current anomalies, provides comprehensive circuit protection and status display, and improves the safety and reliability of the power system. Example 2

[0032] Based on Example 1, this example provides a current detection module 11 for real-time detection of three-phase line current signals, and amplification, filtering and analog-to-digital conversion of the current signals, and finally outputting the three-phase line current signals to the control module 2.

[0033] Please refer to Figure 2 , the current detection module 11 includes current detection submodules respectively arranged on the three phases A, B and C, and the current signals of the three phases A, B and C are respectively input into the control module 2; the specific current detection submodule includes a current transformer U1, an operational amplifier U2, a first resistor R1-a sixth resistor R6, a first capacitor C1-a third capacitor, a first diode C3 a third capacitor; D1, a second diode D2 and an analog-to-digital converter ADC1; the fourth resistor R4 is a sampling resistor; Pin 2 of the current transformer U1 is connected to one end of the third resistor R3, the idle end of the third resistor R3 is connected to pin 3 of the operational amplifier U2, pin 1 of the current transformer U1 is connected to one end of the sixth resistor R6, the idle end of the sixth resistor R6 is connected to pin 4 of the operational amplifier U2, one end of the fourth resistor R4 is connected between pin 2 of the current transformer U1 and the third resistor R3, the other end of the fourth resistor R4 is connected between pin 1 of the current transformer U1 and the sixth resistor R6, and a first capacitor C1 is connected in parallel at both ends of the fourth resistor R4; the third resistor R3 is connected to one end of the first resistor R1 between pin 3 of the operational amplifier U2, the other end of the first resistor R1 is connected to the bias voltage, the pin 1 of the operational amplifier U2 is connected to one end of the fifth resistor R5, and the other end of the fifth resistor R5 is connected to the power supply and the analog-to-digital converter ADC1; Bias voltage eliminates the negative half-cycle of AC power. The leakage current is AC power. The control module 2 cannot recognize negative voltage. Therefore, a bias voltage of 1.25V needs to be provided to the input of the operational amplifier U2. The bias voltage (1.25VREF) and the power supply (+3V_A) of the operational amplifier U2 need to be particularly stable; one end of the second resistor R2 is connected between pin 4 of the operational amplifier U2 and the sixth resistor R6, and the other end of the second resistor R2 is connected between pin 1 of the operational amplifier U2 and the fifth resistor R5. Pin 5 of the operational amplifier U2 is connected to the power supply; a first diode C3 and a third capacitor D1 are provided between the fifth resistor R5 and the power supply; the third capacitor is connected between pin 5 of the operational amplifier U2 and the ground to play a decoupling role; One end of the second capacitor C2 is connected between the fifth resistor R5 and the analog-to-digital converter ADC1, and the other end of the second capacitor C2 is grounded to filter and reduce high-frequency noise; the operational amplifier U2 pin 2 and the current transformer U1 pin 1 are grounded; the second diode D2 is connected in parallel at both ends of the second capacitor C2 to absorb static electricity, which damages the chip in the control module 2. Using the current transformer U1 and the operational amplifier U2, the current detection submodule can accurately detect and amplify the three-phase current signal; the use of the first capacitor C1, the second capacitor C2 and the third capacitor is helpful for decoupling and reducing high-frequency noise, ensuring the stability of the output signal.

[0034] like Figure 3As shown, preferably, the bias voltage is provided by a 1.25V voltage reference circuit, in which the reference voltage chip adopts REF3030, the power supply is provided by a 3V reference circuit, in which the reference voltage chip adopts REF3012, and coupling capacitors are provided in both the 1.25V reference circuit and the 3V reference circuit to reduce the interference of power supply noise.

[0035] The current detection module 11 in this embodiment has significant beneficial effects in terms of high-precision detection and signal stability. Through the current transformer U1 and the operational amplifier U2, the three-phase current signal can be accurately detected and amplified to ensure the accuracy and reliability of the signal. The application of the first, second and third capacitors helps to decouple and reduce high-frequency noise, ensure the stability of the output signal, and improve the signal quality. In addition, the second diode D2 connected in parallel at both ends of the second capacitor C2 effectively absorbs static electricity, protects the chip in the control module 2, and enhances the durability and reliability of the system.

[0036] The bias voltage is provided by the REF3030 reference voltage chip to ensure the optimal working state of the operational amplifier U2 and improve the current measurement accuracy. The use of the REF3012 reference voltage chip to provide a 3V power supply, combined with the use of coupling capacitors, can effectively reduce power supply noise interference and further improve the stability of system performance. The modular design enables each phase to have an independent current detection submodule, realizing independent detection and processing of three-phase currents, enhancing the flexibility and adaptability of the system. Overall, the module achieves high-precision detection and stable output of three-phase currents through multiple optimization designs, providing reliable input for the control module 2 and ensuring the efficient operation of the entire protection device. Example 3

[0037] Based on embodiment 1, this embodiment provides a control module 2.

[0038] Please refer to Figure 4 The main chip of control module 2 adopts STM32 microcontroller. STM32 microcontroller provides clock signal through crystal oscillator circuit. Clock circuit is usually composed of crystal oscillator and related capacitors. The frequency of crystal oscillator determines the clock frequency of microcontroller, which in turn affects the running speed and processing capacity of microcontroller. It is debugged and programmed through the joint test action group interface. The reset circuit is responsible for resetting the microcontroller to the initial state when necessary, so as to reload the program or solve the operation abnormality. The reset circuit can be realized by power-on reset or manual reset button.

[0039] The control module 2 is also provided with a display module, and the display module is used to display the current leakage current information.

[0040] The control module 2 is provided with four independent buttons, and the leakage current threshold is designed by pressing the buttons.

[0041] This embodiment uses an STM32 single-chip microcomputer as the main chip, combined with the clock signal provided by the crystal oscillator circuit, to achieve efficient operation and powerful processing capabilities. The download circuit supports program downloading, debugging and online programming through the JTAG or SWD interface, making development and maintenance more convenient. The reset circuit provides power-on reset and manual reset functions to ensure that the system can recover quickly under abnormal conditions. The display module displays the leakage current information in real time, helping users to monitor intuitively. The design of four independent buttons makes the setting of the leakage current threshold more flexible, enhancing the user-friendliness and adjustability of the system. Example 4

[0042] Based on Embodiment 1, this embodiment provides a tripping module 3 which attracts the armature to drive the circuit breaker to trip under the control of the control module 2.

[0043] Please refer to Figure 5 The tripping module 3 includes an electromagnetic coil U3, an NPN transistor Q1, a seventh resistor R7, an eighth resistor R8, a ninth resistor, and a Coil1 interface. The electromagnetic coil U3 is used to attract the armature to drive the circuit breaker to trip. One end of the ninth resistor is connected to a 5V power supply, and the other end of the ninth resistor is connected to the input end of the electromagnetic coil U3. The grounding end of the electromagnetic coil U3 is connected to the collector of the NPN transistor Q1, the emitter of the NPN transistor Q1 is grounded, and the base of the NPN transistor Q1 is connected to the Coil1 interface. The Coil1 interface is connected to the output interface of the control module 2. When Coil1 receives a high level, the NPN transistor Q1 is turned on, and at the same time, the electromagnetic coil U3 attracts the armature to drive the circuit breaker to trip. An eighth resistor R8 is connected in series between the Coil1 interface and the output interface of the control module 2. One end of the seventh resistor R7 is connected between the eighth resistor R8 and the base of the NPN transistor Q1, and the other end of the seventh resistor R7 is grounded. When the output of the control module 2 is a high level, the NPN transistor Q1 is turned on, and the electromagnetic coil U3 attracts the armature to drive the circuit breaker to trip.

[0044] Under the control of the control module 2, the tripping module 3 drives the circuit breaker to trip through the electromagnetic coil U3, thereby realizing efficient, reliable and energy-saving tripping control. The module adopts a combination of the electromagnetic coil U3 and the NPN transistor Q1, which can quickly and accurately trigger the tripping action and improve the response speed of the system. The setting of the seventh resistor R7 and the eighth resistor R8 in the circuit ensures the stability of the base current, avoids overcurrent and false triggering, and improves stability and reliability. The simplified circuit design uses the NPN transistor Q1 as a switch control, reduces additional control elements and complex circuit connections, and reduces the difficulty of design and implementation. Example 5

[0045] Based on Embodiments 1-4, this embodiment provides a method for performing leakage and overcurrent protection using a leakage and overcurrent protection device, including the following steps: S1, the device is started, and the staff sets the interval current signal, I1, I2, I3, through four independent buttons. The interval current signals I1, I2, I3 divide the current signal into four intervals, which are 0-I1 unbalanced current interval, I1-I2 abnormal current interval, I2-I3 working current interval, and greater than I3 short-circuit current interval; S2, obtaining current signals, respectively obtaining three-phase current signals; S3, calculating the vector sum of three-phase current signals; It is worth noting that in a three-phase balanced system, the current vector of each phase differs by 120 degrees in phase. Assume that the current vectors of the three-phase electricity are: Ia=A∠0∘; Ib=A∠−120∘; Ic=A∠120∘, where A is the current amplitude. The three-phase current vector sum can be added together: Itotal=Ia+Ib+Ic=A∠0∘+A∠−120∘+A∠120∘ = 0; Using the property of complex number addition, these three vectors are converted into complex numbers and added, and the final result is 0. If the result is not 0, the extra value is the leakage current; S4, judge and display the cable status, and control the circuit breaker operation; If the vector sum is zero, it is determined that there is no leakage and the circuit breaker does not operate, and the insulation of the output cable of the control display screen by the control module 2 is normal; Compare the actual current with the interval current signals I1, I2, and I3, and divide the actual current into four intervals; If the current signal is placed in the unbalanced current range and the working current range, the circuit breaker does not operate, and the insulation of the output cable of the control display screen by the control module 2 is normal; If the current signal is in the abnormal current interval, the control module 2 controls the trip module 3 to output a high level to control the trip module 3 to drive the circuit breaker to trip, and at the same time, the control module 2 controls the display screen to output a cable insulation fault; If the current signal is in the short-circuit current interval, the control module 2 outputs a high level to the trip module 3 to control the trip module 3 to drive the circuit breaker to trip. At the same time, the control module 2 controls the display screen to output a phase-to-phase short-circuit fault.

[0046] Preferably, in step S1, the constant value of I1 is relatively small to avoid the current fluctuation caused by imbalance that may lead to malfunction of the trip module 3; the constant value of I2 is slightly smaller than the rated opening and closing current of the disconnector to avoid the rated opening and closing current of the disconnector; the constant value of I3 is slightly larger than the rated opening and closing current of the disconnector to prevent short circuits of the live wire and the neutral wire in the vicinity, short circuits between phases and other large currents.

[0047] It should be noted that due to voltage fluctuations, the opening and closing currents of the disconnector will also fluctuate. I2 is the minimum closing value of the disconnector, and I3 is the maximum closing current of the disconnector. Closing the disconnector requires at least a current value of I2. Therefore, the current value in the range of I1 to I2 may be the current generated by the cable insulation failure.

[0048] The current signal range can be flexibly set through four independent buttons to achieve accurate division of unbalanced, abnormal, working and short-circuit currents.

[0049] The process of obtaining and calculating the vector sum of the three-phase current signal utilizes the properties of the three-phase balanced system and can quickly determine the leakage situation. When the vector sum is zero, the system determines that there is no leakage and displays that the cable insulation is normal.

[0050] By comparing the actual current with the set interval signals I1, I2, and I3, the system can accurately determine the current state: if the current signal is in the unbalanced or working current interval, the circuit breaker will not operate and the cable insulation will be displayed as normal; if the current signal is in the abnormal current interval, the system will trigger a trip and display an insulation fault; if it is in the short-circuit current interval, it will also trigger a trip and display a short-circuit fault. This method effectively avoids false operations through precise interval settings and judgment mechanisms, ensuring the safety and reliability of the system.

[0051] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. The substitution may be a substitution of a part of the structure, device, method step, or a complete technical solution. The equivalent replacement or change according to the technical solution and the inventive concept of the present invention shall be covered within the protection scope of the present invention.

Claims

1. A leakage and overcurrent protection device, characterized in that: include: Current detection module, control module, trip module and power supply module; A current detection module is used to detect three-phase line current signals, amplify the detected current signals, filter the amplified current signals, convert the filtered current signals into digital signals and transmit the digital signals to the control module; The control module is used to receive the current signal output by the current detection module, calculate the vector sum of the three-phase current signal, compare the current signal with the interval current signal, and divide the current signal into four intervals, which are an unbalanced current interval, an abnormal current interval, a working current interval, and a short-circuit current interval; When the current signal is in the abnormal current interval and the short-circuit current interval, the control module controls the trip module to trip; when the current signal is in the unbalanced current interval and the working current interval, the control module controls the trip module not to act; The tripping module is used to drive the circuit breaker to trip under the control of the control module; Display module, used to display cable status; The power module is used to supply power to the current detection module, the control module and the trip module.

2. The leakage and overcurrent protection device according to claim 1, characterized in that: The current detection module includes current detection submodules respectively arranged on the three phases A, B and C, and the current signals of the three phases A, B and C are respectively input into the control module.

3. The leakage and overcurrent protection device according to claim 2, characterized in that: The current detection submodule includes a current transformer, an operational amplifier, a first resistor-a sixth resistor, a first capacitor-a third capacitor, a first diode, a second diode and an analog-to-digital converter; the pin 2 of the current transformer is connected to one end of the third resistor, the idle end of the third resistor is connected to the pin 3 of the operational amplifier, the pin 1 of the current transformer is connected to one end of the sixth resistor, the idle end of the sixth resistor is connected to the pin 4 of the operational amplifier, one end of the fourth resistor is connected between the pin 2 of the current transformer and the third resistor, the other end of the fourth resistor is connected between the pin 1 of the current transformer and the sixth resistor, and the first capacitor; one end of the first resistor is connected between the third resistor and the operational amplifier pin 3, the other end of the first resistor is connected to the bias voltage, the operational amplifier pin 1 is connected to one end of the fifth resistor, and the other end of the fifth resistor is connected to the power supply and the analog-to-digital converter; one end of the second resistor is connected between the pin 4 of the operational amplifier and the sixth resistor, the other end of the second resistor is connected between the pin 1 of the operational amplifier and the fifth resistor, and the pin 5 of the operational amplifier is connected to the power supply; a first diode is provided between the fifth resistor and the power supply; the third capacitor is connected between the operational amplifier pin 5 and the ground to play a decoupling role; One end of the second capacitor is connected between the fifth resistor and the analog-to-digital converter, and the other end of the second capacitor is grounded to filter and reduce high-frequency noise; The operational amplifier pin 2 and the current transformer pin 1 are grounded; and a second diode is connected in parallel at both ends of the second capacitor to absorb static electricity.

4. The leakage and overcurrent protection device according to claim 3, characterized in that: The bias voltage is provided by a 1.25V voltage reference circuit, in which the reference voltage chip is REF3030. The power supply is provided by a 3V reference circuit, in which the reference voltage chip is REF3012. Both the 1.25V reference circuit and the 3V reference circuit are provided with coupling capacitors to reduce interference from power supply noise.

5. The leakage and overcurrent protection device according to claim 1, characterized in that: The control module main chip adopts an STM32 single-chip microcomputer, which provides a clock signal through a crystal oscillator circuit and is debugged and programmed through a joint test action group interface.

6. The leakage and overcurrent protection device according to claim 1 or 5, characterized in that: The control module is also provided with a display module, and the display module is used to display current leakage current information.

7. The leakage and overcurrent protection device according to claim 6, characterized in that: The control module is provided with four independent buttons, and the leakage current threshold is designed by pressing the buttons.

8. The leakage and overcurrent protection device according to claim 1, characterized in that: The tripping module includes an electromagnetic coil, an NPN transistor, a seventh resistor, an eighth resistor, a ninth resistor, and a Coil1 interface. The electromagnetic coil is used to attract the armature to drive the circuit breaker to trip. One end of the ninth resistor is connected to a 5V power supply, and the other end of the ninth resistor is connected to the input end of the electromagnetic coil. The ground end of the electromagnetic coil is connected to the collector of the NPN transistor, the emitter of the NPN transistor is grounded, the base of the NPN transistor is connected to the Coil1 interface, and the Coil1 interface is connected to the output interface of the control module. When Coil1 receives a high level, the NPN transistor is turned on, and at the same time, the electromagnetic coil attracts the armature to drive the circuit breaker to trip. An eighth resistor is connected in series between the Coil1 interface and the output interface of the control module, one end of the seventh resistor is connected between the eighth resistor and the base of the NPN transistor, and the other end of the seventh resistor is grounded.

9. A leakage and overcurrent protection method, using the leakage and overcurrent protection device according to any one of claims 1 to 8, characterized in that: The steps include: S1, the device is started, and the staff sets the interval current signal, I1, I2, I3, through four independent buttons. The interval current signals I1, I2, I3 divide the current signal into four intervals, which are 0-I1 unbalanced current interval, I1-I2 abnormal current interval, I2-I3 working current interval, and greater than I3 short-circuit current interval; S2, obtaining current signals, respectively obtaining three-phase current signals; S3, calculating the vector sum of three-phase current signals; S4, judge and display the cable status, and control the circuit breaker operation; If the vector sum is zero, it is determined that there is no leakage and the circuit breaker does not operate. At the same time, the insulation of the output cable of the control module control display screen is normal; Compare the actual current with the interval current signals I1, I2, and I3, and divide the actual current into four intervals; If the current signal is placed in the unbalanced current range and the working current range, the circuit breaker does not operate, and the insulation of the output cable of the control module control display screen is normal; If the current signal is placed in the abnormal current interval, the control module controls the trip module to output a high level to control the trip module to drive the circuit breaker to trip, and at the same time, the control module controls the display screen to output a cable insulation fault; If the current signal is placed in the short-circuit current range, the control module outputs a high level to the trip module to control the trip module to drive the circuit breaker to trip. At the same time, the control module controls the display screen to output a phase-to-phase short-circuit fault.

10. The leakage and overcurrent protection device according to claim 9, characterized in that: In the step S1, the I1 setting is relatively small to avoid the current fluctuation caused by imbalance that may lead to malfunction of the trip module; the I2 setting is slightly smaller than the rated disconnector opening and closing current to avoid the rated disconnector opening and closing current; the I3 setting is slightly larger than the rated disconnector opening and closing current to prevent short circuits between the live wire and the neutral wire in the vicinity, short circuits between phases and other large current short circuits.

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