Novel mobile substation power supply system frequency converter 3DR electric leakage detection protection device

Abstract

The utility model discloses a novel mobile transformer station power supply system frequency converter 3DR electric leakage detection protection device comprising an electric leakage test controller and a low voltage sampling unit. And the electric leakage test controller is connected with the low-voltage sampling unit. The low-voltage sampling unit comprises a three-phase electronic voltage transformer and an electric leakage test contactor. A 3DR electric leakage detection unit and a three-phase voltage detection unit are arranged in the three-phase electronic voltage transformer. Electric leakage detection and instantaneous protection of the frequency converter can be realized through a 3DR electric leakage technology; selective earth leakage protection is realized according to the detection of the fundamental component and the harmonic wave; through harmonic leakage current and fundamental wave detection system distributed capacitance, electric leakage protection and capacitive current accurate judgment of power supply equipment in a coal mine power supply system can be realized. Electric leakage safety protection of the frequency converter is ensured, and the electric leakage protection method of the neutral ungrounded power supply system is added.

Description

TECHNICAL FIELD

[0001] The utility model relates to a coal mine power supply system technical field especially relates to a new type mobile substation power supply system frequency converter 3DR electric leakage detection protection device. BACKGROUND

[0002] With the continuous development of coal mining technology and the extensive use of electrical equipment in coal mine, the stability and safety of power supply system play a vital role in coal mine production. Especially with the expansion of fully mechanized coal mining face and the popularity of large-capacity high-energy consumption equipment, coal mine power supply system needs to meet higher load demand and safety requirements. As a kind of efficient and energy-saving electrical technology, frequency conversion technology has been widely used in coal mine, especially through the way of frequency converter to control the speed and power of equipment, which greatly improves the efficiency and flexibility of underground equipment operation.

[0003] At present, most of the frequency converters used in coal mine adopt three-phase power input, which realizes the requirements of frequency conversion technology through mobile substation structure. The application of frequency converter not only simplifies the circuit structure, but also reduces the equipment size, making installation and maintenance more convenient. However, frequency converter will produce certain leakage current during use, especially in the humid environment of coal mine, this leakage phenomenon is more obvious, which will cause potential threat to the stability of power supply system and the safety of personnel electric shock. In order to ensure the safety of underground power system, electric leakage protection as one of the three protection measures of coal mine power supply is particularly important.

[0004] Although the existing technology can meet the requirements of coal mine electric leakage protection to some extent, with the large-scale application of frequency converter and the development of high-frequency carrier technology, it still has the following main defects:

[0005] Harmonic interference problem: frequency converter will produce high-frequency harmonic current during operation, which will affect the detection sensitivity of existing electric leakage protection device, leading to inaccurate or even failure of electric leakage protection action. Malfunction caused by parasitic capacitance: due to the existence of parasitic capacitance to ground on the output side of frequency converter, under the action of high-frequency carrier, a large leakage current will be formed. Although this leakage current may not be dangerous, it will cause the malfunction of protection device and affect the normal operation of equipment. Instability of ground insulation resistance monitoring: the environment of coal mine is humid, and the insulation resistance is easily disturbed by external factors. The existing ground insulation monitoring method is difficult to accurately distinguish between normal resistance fluctuation and real electric leakage fault. Increase of electric leakage current value: with the increase of carrier frequency of frequency converter, the parasitic capacitance current to ground increases, and the electric leakage current value also increases, further increasing the risk of electric shock to personnel.

[0006] Therefore, a new type of mobile substation power supply system frequency converter 3DR electric leakage detection protection device is urgently needed. Utility Model Content

[0007] This invention provides a novel 3DR leakage current detection and protection device for frequency converters in mobile substation power supply systems, in order to solve the aforementioned problems existing in the prior art.

[0008] To achieve the above objectives, this utility model provides the following technical solution:

[0009] A novel 3DR leakage current detection and protection device for frequency converters in a mobile substation power supply system includes: a leakage current test controller and a low-voltage sampling unit;

[0010] The leakage current test controller is connected to the low-voltage sampling unit.

[0011] The low-voltage sampling unit includes a three-phase electronic voltage transformer and a leakage current test contactor.

[0012] Three-phase electronic voltage transformers are used to collect three-phase voltage signals, and leakage current test contactors are used to perform leakage current tests.

[0013] Among them, the three-phase electronic voltage transformer has a built-in 3DR leakage current detection unit and a three-phase voltage detection unit;

[0014] The 3DR leakage current detection unit consists of a high-voltage diode and a current-limiting resistor R, forming a leakage current detection channel;

[0015] The three-phase voltage detection unit is used to realize the automatic switching between leakage current lockout and leakage current.

[0016] The high-voltage diode in the 3DR leakage current detection unit is connected through a three-phase power supply system to form a virtual common cathode and common anode star point. It is also connected to the system leakage current circuit through a current limiting resistor R to form a leakage current detection channel, which also serves as a leakage current lockout detection channel.

[0017] The current-limiting resistor R is used to detect the leakage rectangular wave flowing through the current-limiting resistor R.

[0018] Among them, the leakage current test contactor is used for leakage current testing and distributed capacitance detection.

[0019] The leakage current test controller has a built-in microprocessor, which includes an A / D conversion module, a logic judgment module, and a program analysis module.

[0020] The A / D conversion module is connected to the low-voltage sampling unit, the logic judgment module is connected to the A / D conversion module, and the program analysis module is connected to the logic judgment module.

[0021] It also includes a power module, which is connected to the leakage current test controller and the low-voltage sampling unit to provide power to the leakage current test controller and the low-voltage sampling unit.

[0022] The low-voltage sampling unit is connected with three-phase input terminals of the frequency converter, and the leakage test contactor is connected with wiring terminals of the alternating current power supply.

[0023] Compared with the prior art, the utility model has the following advantages:

[0024] Through 3DR leakage technology, leakage detection and instantaneous protection of the frequency converter can be realized, and according to the detection of fundamental component and harmonic, selective leakage protection can be realized, and through harmonic leakage current and fundamental detection system distribution capacitor, leakage protection and capacitor current accurate judgment of power supply equipment in the coal mine power supply system can be realized, and leakage safety protection of the frequency converter is ensured, and a leakage protection method of neutral point non-grounded power supply system is increased.

[0025] Other features and advantages of the utility model will be described in the subsequent description, and part of them becomes obvious from the description, or is understood by implementing the utility model.

[0026] The technical scheme of the utility model will be further described in detail below by means of the drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0027] The drawings are used to provide further understanding of the utility model, and constitute a part of the description, and are used to explain the utility model together with the embodiments of the utility model, and do not constitute the limitation of the utility model.In the drawings,

[0028] Figure 1 It is a novel mobile substation power supply system frequency converter 3DR leakage detection protection device structure diagram in the embodiment of the utility model;

[0029] Figure 2 It is a novel mobile substation power supply system frequency converter 3DR leakage detection protection device principle diagram in the embodiment of the utility model;

[0030] Figure 3 It is a novel mobile substation power supply system frequency converter 3DR leakage detection protection device structure diagram in the embodiment of the utility model; DETAILED DESCRIPTION

[0031] The preferred embodiments of the utility model are described below in combination with the drawings, and it should be understood that the preferred embodiments described here are only used to illustrate and explain the utility model, and are not used to limit the utility model.

[0032] The utility model embodiment provides a novel mobile substation power supply system frequency converter 3DR leakage detection protection device, as shown in Figure 1 Shown, including: leakage test controller and low-voltage sampling unit;

[0033] The leakage test controller is connected with the low-voltage sampling unit.

[0034] The working principle of the above technical solution is as follows: Figure 2 As shown in the figure, the mobile substation power supply system refers to the main power supply unit in the substation, which is responsible for providing power to the entire system. This module outputs a voltage of 10kV, corresponding to the conventional high-voltage power supply level. The 3DR leakage detection unit is used to monitor whether there is current leakage on the power supply line, ensuring the safe operation of the electrical system. The leakage protection unit includes one or more sensors to detect whether current is leaking from the intended circuit. The frequency converter 3DR is responsible for adjusting the voltage and frequency transmitted through the power grid to meet the power requirements of different devices. The frequency converter can effectively adjust the output power and improve the efficiency of electrical energy use. The main power supply module supplies power to the frequency converter through the cable, and the frequency converter adjusts the voltage and frequency output according to the demand. The 3DR leakage detection unit determines whether there is a leakage phenomenon by measuring the current, and if leakage is detected, the system will trigger a protection mechanism to cut off the power supply to prevent further electrical safety problems. When any abnormality (such as leakage) is detected, the protection device will immediately respond by disconnecting the power supply to protect the entire system and its users.

[0035] The leakage test controller is the core of the entire leakage detection and protection system, and its main function is to analyze the leakage characteristics of the system, including leakage harmonics, fundamental frequency and other parameters, to realize leakage detection, protection control and fault isolation.

[0036] Fourier series analysis: The leakage test controller collects the leakage signals in the power grid and uses the Fourier algorithm to perform spectral analysis on the signals. Fourier series can decompose complex signals into fundamental components (system main frequency) and harmonic components (non-normal frequency), which facilitates leakage determination.

[0037] Fundamental component detection: Extract the fundamental component of the main voltage and current signal of the system in normal operation. Harmonic analysis: Identify abnormal harmonic signals caused by equipment insulation failure or external interference. Leakage value calculation: Substitute the analyzed data into the algorithm model to obtain the leakage value of the system.

[0038] When the leakage value exceeds the safety threshold, the leakage test controller sends a signal to the protection device to trigger system tripping or alarm. The leakage lockout function is realized, that is, when serious leakage is detected, the system is prevented from continuing to operate to avoid equipment damage or personnel injury. Automatic test function: The controller has an automatic test function to verify whether the protection function of the device is effective by simulating the leakage state.

[0039] The main task of the low-voltage sampling unit is to collect voltage and current signals of the electrical system in real time as the basic data source for leakage detection. Signal acquisition: three-phase voltage signals and leakage current signals are obtained through sensors such as three-phase voltage transformers and current transformers. Three-phase voltage transformer: the three-phase voltage in the high-voltage power grid is reduced in proportion to a safe low-voltage range for processing by the sampling unit. Current transformer: detects the leakage current signal present in the circuit and outputs a voltage signal proportional to the leakage current. Signal conditioning: the sampling unit filters and amplifies the original signal to eliminate noise and interference and enhance the accuracy of the signal. Data transmission: the collected digital signals are transmitted to the leakage test controller as the basic data for further analysis. Connection with the leakage test controller: the low-voltage sampling unit is connected with the leakage test controller through a data bus or analog interface to ensure real-time signal transmission and synchronization.

[0040] System overall workflow: data acquisition: the low-voltage sampling unit collects three-phase voltage signals and leakage current signals. Signal analysis: after receiving the data, the leakage test controller uses the Fourier algorithm to decompose the signal and analyze the fundamental component, harmonic component, and carrier frequency. Leakage value calculation: the controller calculates the real-time leakage value of the system in combination with the power grid model and algorithm. Protection decision: based on the comparison of the leakage value with the preset threshold, it is determined whether to trigger the protection action. Execute protection: if the leakage value exceeds the standard, the controller controls the leakage test contactor to execute tripping to protect the system safety.

[0041] The beneficial effects of the above technical solution are: through the Fourier algorithm to analyze the fundamental component, harmonic component, and carrier frequency of the leakage signal, the complex leakage fault can be accurately identified. Especially in the frequency converter power supply system, due to the presence of many harmonic components, the traditional method is difficult to detect high-frequency leakage signals, but the system can efficiently handle it. The system can respond quickly at the moment of leakage occurrence to prevent the fault from expanding. Through the three-phase voltage detection unit, leakage locking and leakage automatic switching are realized to ensure the stability and continuity of the power supply system. Through the 3DR leakage detection technology, not only low-voltage leakage can be detected, but also different voltage levels of insulation monitoring in IT power supply systems can be applied. It can effectively analyze the distributed capacitance in the power supply system to improve the adaptability of the leakage protection device.

[0042] In another embodiment, the low-voltage sampling unit includes a three-phase electronic voltage transformer and a leakage test contactor.

[0043] The three-phase electronic voltage transformer is used to collect three-phase voltage signals, and the leakage test contactor is used for leakage test.

[0044] The working principle of the above technical solution is: the three-phase electronic voltage transformer is mainly used to collect three-phase voltage signals. The specific operation steps are as follows:

[0045] Voltage Signal Sensing: The three-phase electronic voltage transformer contains an inductive coil inside, which converts high-voltage input signals (such as 10kV or higher) into low-voltage signals (such as 100V or below) through electromagnetic induction principles for low-voltage circuit processing. In a three-phase system, L1, L2, and L3 three live wires are connected to the input terminals of the three-phase electronic voltage transformer, respectively sensing their corresponding voltage signals.

[0046] Voltage Signal Conversion: The input high voltage is reduced to a low voltage signal suitable for electrical equipment or measurement devices through the voltage reduction device of the transformer. This signal conversion not only ensures system safety, but also provides accurate input for subsequent devices. The converted low voltage signal is output in the form of current or voltage, usually as a scaled signal. For example, when the input voltage is 10kV, the output may be 100V, with a scaling ratio of 100:1.

[0047] Voltage Signal Output: The converted low voltage signal is transmitted to the leakage detection protection device or other devices for real-time monitoring of the status of three-phase voltage, including whether the voltage is normal, unbalanced, etc.

[0048] Leakage Test Contactor: The leakage test contactor is used to simulate and detect leakage phenomena in the system, ensuring that the substation system has good leakage protection function. The specific operation steps are as follows:

[0049] Contactor Closure Preparation: The contactor contains a set of closable electrical contacts and a coil device inside. When a leakage test is needed, the leakage detection protection device sends a trigger signal to the contactor. The coil of the contactor generates electromagnetic force to drive the contactor's contacts to close after receiving the control signal.

[0050] Leakage Test Process: After the contacts are closed, the contactor simulates a leakage phenomenon and conducts current to a specific leakage path (usually the ground line). At this time, the leakage detection protection device monitors the change of ground current to determine whether the leakage signal is correctly identified. For example, if the leakage current detected by the protection device exceeds the set threshold (such as 30mA), it will immediately trigger an alarm or circuit breaking action.

[0051] Automatic Recovery and Test Completion: After the leakage test is completed, the contactor contacts return to the open state. The leakage detection protection device records and analyzes the test results and enters standby state for next use.

[0052] The beneficial effects of the above technical solutions are: the three-phase electronic voltage transformer can collect three-phase voltage signals with high precision and reflect the voltage state of the system in real time. For the frequency converter 3DR leakage detection protection device, accurate voltage signal input is an important prerequisite for ensuring the reliability of leakage detection. The system can timely discover abnormalities such as excessively high or low voltage or three-phase imbalance through voltage signal monitoring, thereby ensuring the safe operation of the system. The leakage test contactor can simulate leakage conditions through manual or automatic triggering, so that the leakage detection protection device can perform function testing under the premise of no actual danger. For the power supply system of a substation, such testing can ensure the sensitivity and reliability of the leakage detection device and avoid the occurrence of leakage hazards.

[0053] In another embodiment, the three-phase electronic voltage transformer is internally provided with a 3DR leakage detection unit and a three-phase voltage detection unit.

[0054] The 3DR leakage detection unit is composed of a high-voltage diode and a current-limiting resistor R to form a leakage detection channel.

[0055] The three-phase voltage detection unit is used to realize leakage locking and automatic conversion of leakage.

[0056] The working principle of the above technical solutions is that the internal structure of the three-phase electronic voltage transformer includes two key units: a 3DR leakage detection unit responsible for forming a leakage detection current channel and monitoring leakage current, and a three-phase voltage detection unit used to detect three-phase voltage states and realize leakage locking (prevent continuous power supply in the case of leakage) and automatic conversion of leakage.

[0057] The 3DR leakage detection unit forms a leakage detection channel through the combination of a high-voltage diode and a current-limiting resistor R to capture leakage phenomena in the system. The construction of the leakage detection channel: the high-voltage diode is used for unidirectional conduction, allowing current to flow in only one direction. When leakage occurs in the system, the leakage current will flow through the leakage detection channel (including the high-voltage diode and the current-limiting resistor R) to the ground.

[0058] The high-voltage diode can withstand high-voltage input in the system while ensuring that the leakage current is guided into the detection loop in a controlled manner. Limitation and protection of leakage current: the role of the current-limiting resistor R is to limit the leakage current to prevent excessive current from flowing through the detection unit and protect the safety of the equipment. If the leakage current is too large, the current-limiting resistor will limit it within a safe range (such as below several tens of milliamperes) to avoid damaging the equipment.

[0059] Detection and output of leakage signals: when the current in the leakage detection channel exceeds the preset threshold (such as 30 mA), the 3DR leakage detection unit sends a signal to the protection device. The protection device starts the subsequent leakage protection functions such as alarm or power cutoff through this signal.

[0060] The three-phase voltage detection unit is responsible for collecting three-phase voltage signals and achieving the leakage lockout and automatic conversion functions through logical control. The collection and analysis of three-phase voltage signals: The three-phase voltage detection unit collects the voltage values (L1, L2, L3) of the three-phase system in real time through an electronic transformer. The unit analyzes whether the three-phase voltage is within the normal range. For example, when the voltage of a certain phase deviates from the standard value (such as 3300V ± 15%), the system will record this abnormal state.

[0061] Leakage lockout function: If the leakage detection unit detects a leakage current, and the three-phase voltage detection unit confirms that the voltage is normal, the system will activate the leakage lockout function. Leakage lockout prevents the leakage current from further expanding by cutting off the power supply, thereby protecting equipment and personnel safety.

[0062] Automatic conversion function of leakage: After detecting leakage, the three-phase voltage detection unit can also automatically switch from the leakage state to the normal operating state according to the voltage state and leakage recovery. For example, when the leakage current returns to the normal range (less than 30mA), the system can automatically release the lockout and restore power supply.

[0063] The beneficial effects of the above technical solution are: The built-in 3DR leakage detection unit uses the combination of high-voltage diodes and current-limiting resistors to capture leakage phenomena with high sensitivity and accurately limit leakage current. This effectively reduces the safety hazards such as equipment failure or fire caused by leakage. The three-phase voltage detection unit can monitor the three-phase voltage state in real time, ensuring that the system operates within a safe voltage range at all times. When the voltage is abnormal, the unit can notify the protection device in time to avoid equipment damage caused by excessively high or low voltage. The leakage lockout function can quickly cut off the power supply when leakage occurs, thereby preventing the leakage current from spreading to the entire system. In mobile substations, the leakage lockout function is particularly important, as it can prevent leakage failures caused by complex environments such as humidity or high temperature.

[0064] In another embodiment, the high-voltage diode in the 3DR leakage detection unit is connected through the three-phase power supply system to form a virtual common cathode and anode star point, and is connected to the system leakage loop through a current-limiting resistor R to form a leakage detection channel, as well as a leakage lockout detection channel.

[0065] The working principle of the above technical solution is: In the 3DR leakage detection unit, the high-voltage diode plays a key role. The high-voltage diode is usually a semiconductor component that can withstand a higher voltage difference, and its working principle is that it can only be turned on when the current flows in one direction.

[0066] Virtual common neutral and positive star point: In a three-phase power system, the neutral point of the common star connection is usually the ideal reference point of the "common neutral" or "common positive". Through the configuration of high-voltage diodes, the voltages of the three-phase power supply system are connected to each other through these diodes, forming a virtual common neutral or common positive star point.

[0067] Common neutral refers to the common connection of the negative ends of the three phase lines, simulating the formation of a "cathode" point, usually connected to ground. Common positive refers to the common connection of the positive ends of the three phase lines, simulating the formation of an "anode" point, through which the high-voltage end of the power supply system is connected to the negative end. In this design, high-voltage diodes are used to connect the voltages of the three-phase power supply system to each other, forming a virtual star point. This star point is not directly connected by physical wires, but is achieved through electrical components such as diodes, thus avoiding the inconvenience and risks brought about by actual physical connections.

[0068] Current limiting resistor R and leakage circuit connection: The current limiting resistor R is connected to the virtual star point formed above and contacts the leakage circuit of the system (usually through grounding or other leakage paths), forming a leakage detection channel.

[0069] Current limiting resistor R: The current limiting resistor plays a role in controlling the flow of current in the circuit. When leakage occurs, the leakage current will flow through the resistor, and the presence of the resistor can effectively limit the current from being too large, thus avoiding damage to equipment or causing safety accidents due to excessive leakage current. For example, the resistance value is set so that the leakage current always remains within a safe value, usually tens of milliamperes (such as 30 mA), which is a safe threshold for household and industrial equipment.

[0070] Leakage circuit: The leakage circuit refers to the flow of current through non-normal paths to the ground (such as electrical equipment shell grounding) in the power system due to insulation aging, external interference or equipment failure, etc. The role of the current limiting resistor R is to sense these leakage currents and limit their amplitude, preventing them from affecting the entire power supply leakage detection channel. When leakage occurs, the leakage current flows through the above-mentioned leakage circuit to the ground and passes through the current limiting resistor R. At this time, the leakage detection unit can determine whether a leakage phenomenon has occurred by sensing the change in the leakage current. The specific steps are as follows: the leakage current flows through the current limiting resistor R, and the current size is proportional to the severity of the leakage. If the leakage current exceeds the set threshold (usually 30 mA), the detection unit will send a signal indicating that a leakage has occurred.

[0071] When leakage occurs, the detection unit can not only detect the size of the leakage current, but also process based on the current change, start the "leakage lockout" function: once the leakage current exceeds the set range (such as 30mA), the detection unit will transmit this abnormal signal to the control system. After receiving the leakage signal, the control system will cut off the power supply through the automatic mechanism to prevent the leakage phenomenon from further aggravating. The leakage lockout can protect the electrical equipment from damage due to leakage, and prevent safety hazards such as fire.

[0072] The beneficial effects of the above technical solution are: through the construction of virtual common negative and common positive star points, the system can efficiently and accurately detect the leakage phenomenon. The use of high-voltage diodes ensures that the leakage current can be accurately turned on even in a high-voltage environment, without affecting normal power supply and causing damage to the equipment. The setting of the current-limiting resistor R ensures that the leakage current is not too large, avoiding accidents such as equipment damage or electric shock caused by direct leakage current. The leakage lockout function can quickly disconnect the power supply to avoid further system failure due to leakage problems, improving the reliability and stability of the entire power supply system.

[0073] In another embodiment, the current-limiting resistor R is used to detect the leakage rectangular wave flowing through the current-limiting resistor R.

[0074] The working principle of the above technical solution is: the current-limiting resistor R detects the leakage current: the main function of the current-limiting resistor R is to detect the leakage rectangular wave signal (usually a low-frequency pulse signal or a current with a fixed waveform) flowing through it. The source of the leakage rectangular wave is usually a leakage current caused by poor insulation or external interference in the power supply system.

[0075] In the leakage loop of the frequency converter, the current-limiting resistor R is connected in series. When the system leaks, the leakage current will flow through the current-limiting resistor R. According to the voltage-current characteristic (V=IR) of the resistor, the leakage current will generate a certain voltage drop in the circuit. The change of the voltage drop is recognized and processed by the subsequent detection circuit (such as the sampling circuit or voltage comparator). If the system leakage current is 10mA and the resistance of the current-limiting resistor is 10Ω, the voltage drop on the resistor is 0.1V. This voltage signal will be transmitted to the detection device for analyzing the leakage condition.

[0076] The current-limiting resistor limits the strength of the leakage current in the system, preventing damage to subsequent equipment or circuit overload caused by excessive leakage current. After the leakage rectangular wave signal on the current-limiting resistor is sampled, it is optimized by the signal amplification circuit and the filter circuit. The amplification circuit improves the signal strength, and the filter circuit removes high-frequency interference.

[0077] The beneficial effects of the above technical solution are: the current-limiting resistor and the leakage detection protection device can monitor the leakage condition in the system in real time, avoiding electric shock or damage to equipment due to leakage failure.

[0078] In another embodiment, a leakage test contactor is used for leakage test and detection of distributed capacitance.

[0079] The working principle of the above technical solution is that the function of the leakage test contactor is to simulate the leakage behavior in the system for testing whether the leakage protection function of the system works normally.

[0080] Before starting the leakage detection test, the contactor is closed to simulate a controllable leakage loop.

[0081] The contactor introduces a leakage rectangular wave signal of a specific intensity (such as 10 mA or 30 mA) through the control system. The leakage rectangular wave passes through the current-limiting resistor R and enters the detection circuit of the protection device. The protection device identifies and judges the leakage signal and triggers an alarm or a shutdown operation according to the preset protection value (such as a leakage current threshold of 20 mA).

[0082] Distributed capacitance detection: Distributed capacitance refers to the parasitic capacitance formed between long cables or devices in the power supply system. In leakage detection, distributed capacitance may cause misjudgment of leakage current. The leakage test contactor can analyze and exclude system errors by switching different test conditions (such as simulating connection or disconnection of distributed capacitance).

[0083] Leakage judgment and alarm: The processed signal is input into a microcontroller or a comparison circuit to judge whether it exceeds the leakage protection threshold. Once it exceeds, the system will issue an audible and visual alarm and cut off the power supply through the leakage protection switch.

[0084] The beneficial effects of the above technical solution are that the leakage test contactor is used to test the leakage protection function regularly to ensure that the leakage detection device of the system always maintains sensitivity and accuracy.

[0085] In another embodiment, the leakage test controller is built-in with a microprocessor, which includes an A / D conversion module, a logic judgment module, and a program analysis module.

[0086] The A / D conversion module is connected with the low-voltage sampling unit, the logic judgment module is connected with the A / D conversion module, and the program analysis module is connected with the logic judgment module.

[0087] The working principle of the above technical solution is that, for example, Figure 3Leakage Test Controller ①: This section shows the complete view of the device, labeling the layout of all major components. Circuit Board Assembly in Three-Phase Electronic Voltage Transformer ② and Housing Assembly ③: This demonstrates how the circuit board is installed in its housing. The circuit board is the core of the device, responsible for processing signals and performing leakage detection. The housing provides the necessary physical protection. Drive Mechanism in Low Voltage Sampling Unit ④ and Detection Components ⑤: This section details how the drive mechanism and leakage detection sensors are assembled together. The drive mechanism is responsible for controlling the device's actions, while the sensors monitor for leakage in the current. When the frequency converter is powered, the 3DR Leakage Detection Protection Device monitors the current for leakage through its sensors. Once leakage is detected, the system processes the signal through the built-in circuit board, and the drive mechanism initiates appropriate protective measures, such as cutting off power, to protect the entire power supply system and connected equipment.

[0088] Microprocessor is a prior art, and the low voltage sampling unit is used to collect leakage signals (usually voltage signals) from the leakage current limiting resistor R or other circuits. The sampled signal is usually an analog signal that directly reflects the characteristics of the leakage current.

[0089] The current limiting resistor R generates a voltage drop when the leakage current passes through it. The low voltage sampling unit extracts this analog signal (e.g., 0.1V corresponding to 10mA leakage current) from both ends of the resistor.

[0090] The sampled signal is input to the A / D conversion module. The A / D conversion (analog-to-digital conversion) module converts the analog signal from the low voltage sampling unit into a digital signal for subsequent logical judgment and program analysis.

[0091] The A / D conversion module samples the analog signal and discretizes it into a set of digital values (e.g., 0.1V is converted to the corresponding binary value). The module quickly captures the signal according to the internal set sampling rate (e.g., 1000 samples per second), ensuring system real-time performance. The converted digital signal is passed to the logical judgment module. If the leakage current signal is a sinusoidal wave (e.g., 50Hz, amplitude corresponding to 10mA leakage current), the A / D conversion module will take multiple sampling points (e.g., 20 points) within each cycle and use digital values to represent the current variation characteristics of the waveform.

[0092] Logical Judgment: The main function of the logic judgment module is to perform preliminary processing and analysis of digital signals, identify signal characteristics, and determine whether they meet the leakage protection conditions (such as whether the current exceeds the limit or whether the signal shape is abnormal). It receives digital signals from the A / D conversion module, performs filtering and noise reduction processing to remove high-frequency interference or random noise. It judges the amplitude and frequency characteristics of the signal: if the signal amplitude exceeds a set threshold (e.g., 20mA), it is marked as a potential leakage hazard. If the signal shape is abnormal (e.g., there is non-linear distortion, possibly caused by insulation breakdown), it is determined to be an abnormal leakage. The judgment result is passed to the program analysis module. If the sampled signal is 0.12V, the logic judgment module converts it to a 12mA leakage current value and compares it with the protection threshold (e.g., 20mA). If it is below the threshold, it is marked as a safe state.

[0093] Based on the results from the logic judgment module, the program analysis module performs higher-level processing (such as action control, data recording, and alarm triggering). Based on the signal status transmitted by the logic judgment module, it analyzes whether further protective measures are needed: if the leakage current signal exceeds the limit, the program analysis module triggers an alarm or action command. If the signal is normal, the program analysis module records data for subsequent analysis. During the leakage current test, the program analysis module also records the signal characteristics and system response of the test to verify the function of the protection device. The analysis results are output to a display device or remote monitoring system. If the leakage current signal exceeds the set threshold, the program analysis module may control the contactor to disconnect the power supply and simultaneously issue an audible and visual alarm.

[0094] The leakage current signal is converted into a voltage signal through the current-limiting resistor R. The low-voltage sampling unit acquires the signal and transmits it to the A / D conversion module. The A / D conversion module converts the analog signal into a digital signal. The logic judgment module performs preliminary analysis of the digital signal to identify leakage characteristics. The program analysis module further processes the signal, triggering protection measures or recording data.

[0095] The beneficial effects of the above technical solution are as follows: The A / D conversion module in the microprocessor has high-precision signal capture capabilities, enabling real-time monitoring of subtle leakage current changes and ensuring the system's detection sensitivity and accuracy. The logic judgment module and program analysis module can intelligently identify the characteristics of leakage current signals, avoiding malfunctions (such as false signals caused by distributed capacitance) and quickly triggering protection measures. The microprocessor can record and analyze leakage current data in real time, providing a basis for subsequent maintenance and ensuring the stable operation of the mobile substation frequency converter in complex environments. The program analysis module can upload leakage current signals and system status to a remote monitoring platform, facilitating rapid fault diagnosis by maintenance personnel and improving work efficiency.

[0096] In another embodiment, a power module is also included, which is connected with the leakage test controller and the low-voltage sampling unit, and is used to provide power supply for the leakage test controller and the low-voltage sampling unit.

[0097] The working principle of the above technical solution is that in the leakage test controller, the power module plays a crucial role in providing stable power supply for the entire system (including the leakage test controller and the low-voltage sampling unit). The power module receives external power supply (usually AC power supply, such as 220V or 380V AC), and then converts it into DC power (such as 5V, 12V or 24V DC) suitable for use by each module. The external power supply (AC power supply) is input through the input end of the power module. The rectifier circuit inside the power module converts AC power into DC power. The rectification process converts the positive and negative half cycles of AC power into a single direction current. The rectified DC power is smoothed by a filter to remove voltage fluctuations (such as frequency changes and pulsations in AC power supply), ensuring stable output voltage. The output voltage is adjusted to the voltage level suitable for use by microprocessors and low-voltage sampling units (such as 5V, 12V DC) through step-down conversion (if necessary). The stable DC power output is supplied to the leakage test controller and the low-voltage sampling unit through the connection lines respectively. If the external power supply is 220V AC, the power module will convert it into 12V DC to drive the controller and the sampling unit. The key task of the power module is to maintain voltage stability, unaffected by external grid fluctuations.

[0098] The power module provides necessary power support to ensure that the leakage test controller (including various modules of the microprocessor) can work normally. The leakage test controller includes A / D conversion modules, logic judgment modules, program analysis modules, etc., and all these modules need stable power support. The power module transmits the converted DC power to the power input end of the leakage test controller through the power supply line. Each functional module (such as A / D conversion module, logic judgment module, program analysis module) in the leakage test controller obtains the required current and voltage from the power module to process signals and make decisions. The stability of the power supply directly affects the response speed and accuracy of the entire controller, ensuring that each module works normally during the leakage detection process. Assuming that the power module provides 12V DC to the microprocessor and A / D conversion module in the leakage test controller, it enables real-time sampling and processing of leakage signals. If the power supply is unstable, it may cause the microprocessor to calculate incorrectly, affecting the accuracy of the detection results.

[0099] The power module not only provides power for the leakage test controller, but also provides power support for the low-voltage sampling unit. The low-voltage sampling unit is responsible for collecting leakage signals from the circuit, so it also needs a stable power supply for signal acquisition and conversion. The power module supplies DC power to the low-voltage sampling unit through the power supply line. The low-voltage sampling unit provides the required voltage and current for its sampling circuit through the power supply, ensuring that it can effectively sample the leakage current. The stability of the power supply is also important, voltage fluctuations can affect the sampling accuracy of the low-voltage sampling unit, thereby affecting the measurement results of the leakage current. Assuming that the low-voltage sampling unit needs 5V DC power to drive its sampling circuit, and the power module provides stable DC output of 5V. The power module ensures that the sampling unit can accurately capture the current signal without being affected by voltage fluctuations.

[0100] The beneficial effects of the above technical solution are: the power module converts AC power into stable DC power, ensuring that the leakage test controller and the low-voltage sampling unit work without being affected by external power fluctuations. In power facilities such as substations, external grid fluctuations and disturbances may affect the normal operation of the equipment, and the power module ensures the high reliability of the equipment through smooth voltage output. The power module provides stable power for each module, ensuring that the A / D conversion module, logic judgment module, and program analysis module in the leakage test controller can accurately sample and process signals. The stability of the low-voltage sampling unit directly affects the sampling accuracy of the leakage signal, and the power module provides stable voltage and current to ensure that the system can accurately detect and respond to leakage conditions.

[0101] In another embodiment, the low-voltage sampling unit is connected to the three-phase input of the frequency converter, and the leakage test contactor is connected to the connection terminal of the AC power supply.

[0102] The working principle of the above technical solution is: the sampling port of the low-voltage sampling unit is connected to the three-phase input (A, B, C) of the frequency converter through a dedicated cable. The three-phase input refers to the connection terminal of the frequency converter connected to the three-phase AC power supply, used to receive external power. The low-voltage sampling unit collects real-time signals of three-phase current and voltage, and converts analog signals into digital signals through the built-in sampling module. The sampling unit is integrated with a leakage current monitoring module, which can capture signals in time when the current is abnormal (such as ground fault or excessive leakage current).

[0103] Low-voltage sampling unit: a special circuit module used to collect operating parameters of electrical systems such as voltage and leakage current. Three-phase input: three wires corresponding to A, B, C three phases of three-phase AC, which is the main input interface for power supply.

[0104] The leakage test contactor is connected between the AC power supply and the load (such as a frequency converter). The contactor is used for on-off control of the circuit, and the contact is driven by the electromagnetic coil to complete the operation. The input end of the contactor is connected to the output connection terminal (L1, L2, L3 three-phase) of the AC power supply, and the output end is connected to the load end (such as the input end of the frequency converter). In the leakage detection mode, when the low-voltage sampling unit detects that the leakage current exceeds the safety threshold, it sends a disconnect instruction to the contactor to cut off the electrical connection between the AC power supply and the load, thereby protecting the equipment and personal safety. If you need to test the working performance of the leakage protection device, you can simulate the leakage current by manually triggering the test button to verify whether the system can quickly respond and cut off the power supply.

[0105] Leakage test contactor: an electromagnetic control switch device that can quickly disconnect the circuit when leakage detects an anomaly to protect the system safety. AC power supply connection terminal: refers to the connection interface of the three-phase AC power supply (L1, L2, L3) and the device.

[0106] The overall system is monitored by the low-voltage sampling unit in real time for three-phase current, voltage and leakage current. After the sampling data is processed by a digital signal processor, it is determined whether there is a leakage fault. The leakage test contactor quickly disconnects the power supply when the leakage detection device sends a signal, avoiding damage to equipment or personnel caused by leakage. The system also supports test functions to verify the response performance of the protection device by simulating leakage conditions.

[0107] The above technical solution has the beneficial effects that: by the low-voltage sampling unit, the three-phase input current, voltage, and possible leakage current are collected and monitored in real time, which can accurately determine whether there is a leakage situation. When the leakage current exceeds the safety threshold (for example, 30mA), the system can quickly send a disconnect command to the contactor, thereby cutting off the power supply to prevent electric shock or fire accidents caused by leakage. The safety of the mobile substation power supply system is effectively improved, and it is particularly suitable for power supply scenarios in the wild or complex environments. When an electrical fault (such as insulation aging, short circuit or ground fault) occurs, the leakage protection device can quickly isolate the faulty power supply to prevent damage to the frequency converter and other electrical equipment due to leakage.

[0108] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application also intends to include these modifications and variations.

Claims

1. A novel 3DR leakage current detection and protection device for frequency converters in a mobile substation power supply system, characterized in that, include: Leakage current test controller and low-voltage sampling unit; The leakage current test controller is connected to the low-voltage sampling unit; The low-voltage sampling unit includes a three-phase electronic voltage transformer and a leakage current test contactor; The three-phase electronic voltage transformer has a built-in 3DR leakage current detection unit and a three-phase voltage detection unit. The 3DR leakage current detection unit consists of a high-voltage diode and a current-limiting resistor R, forming a leakage current detection channel; The high-voltage diodes in the 3DR leakage current detection unit are connected through a three-phase power supply system to form a virtual common cathode and common anode star point, and are connected to the system leakage current circuit through a current limiting resistor R to form a leakage current detection channel, which also serves as a leakage current lockout detection channel. The leakage current test controller has a built-in microprocessor, which includes an A / D conversion module, a logic judgment module, and a program analysis module. The low-voltage sampling unit is connected to the three-phase input terminal of the frequency converter, and the leakage current test contactor is connected to the terminal of the AC power supply.

2. The novel mobile substation power supply system inverter 3DR leakage current detection and protection device according to claim 1, characterized in that, Three-phase electronic voltage transformers are used to collect three-phase voltage signals, and leakage current test contactors are used to perform leakage current tests.

3. The novel mobile substation power supply system inverter 3DR leakage current detection and protection device according to claim 1, characterized in that, The three-phase voltage detection unit is used to realize the automatic switching between leakage current lockout and leakage current.

4. The novel mobile substation power supply system inverter 3DR leakage current detection and protection device according to claim 1, characterized in that, The current-limiting resistor R is used to detect the leakage rectangular wave flowing through the current-limiting resistor R.

5. The novel mobile substation power supply system inverter 3DR leakage current detection and protection device according to claim 1, characterized in that, Leakage test contactor, used for leakage testing and detection of distributed capacitance.

6. The novel mobile substation power supply system inverter 3DR leakage current detection and protection device according to claim 1, characterized in that, The A / D conversion module is connected to the low-voltage sampling unit, the logic judgment module is connected to the A / D conversion module, and the program analysis module is connected to the logic judgment module.

7. The novel mobile substation power supply system inverter 3DR leakage current detection and protection device according to claim 1, characterized in that, It also includes a power module, which is connected to the leakage current test controller and the low-voltage sampling unit to provide power to the leakage current test controller and the low-voltage sampling unit.

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