Microcomputer protection device high-voltage bus over-limit detection and isolation alarm module

Abstract

The utility model discloses a kind of microcomputer protection device high-voltage bus over-limit detection and isolation alarm module, comprising: high resistance voltage division network;Filtering capacitor;Comparator, cathode end is connected with the voltage division midpoint of upper arm and lower arm, reference end is used for threshold setting, anode end ground;Hysteresis network;Photoelectric isolator, its emitting diode side is located in high-voltage area, transistor side is located in low-voltage area;LED drive network, including current-limiting resistor and shunt resistance in series in emitting diode;Output pull-up resistor, one end is connected to power supply, the other end is connected with the transistor collector of photoelectric isolator;Output shaping network, including resistance and capacitor, connected to the output end of photoelectric isolator.The utility model has the following beneficial effects: high-precision bus voltage over-limit detection is realized, a completely electrically isolated safety structure is provided, with strong anti-interference ability and low power consumption characteristics.

Description

Technical Field

[0001] This utility model relates to a high-voltage busbar over-limit detection and isolation alarm module for a microcomputer protection device, and particularly to a structure in a power system protection device used to monitor the voltage status of a high-voltage busbar and perform electrical isolation alarms. Background Technology

[0002] In power systems, microprocessor-based protection devices are crucial for ensuring power supply safety and normal equipment operation. These devices require real-time monitoring of various power system parameters, especially accurate monitoring of the voltage status of high-voltage busbars. When the voltage exceeds the safe range, they promptly issue over-limit alarms or trigger protection actions to prevent the escalation of system faults. As a critical component of the power system, the voltage status of the high-voltage busbar is vital to the safe and stable operation of the entire system.

[0003] Traditional high-voltage busbar over-limit detection devices mostly employ analog circuit technology, and the main implementation methods are as follows: The first method uses a voltage transformer (PT) to step down the voltage, and then compares it with a fixed reference voltage using a common voltage comparator chip to achieve over-limit detection. Although this method is simple in structure, it has several technical drawbacks in practical applications: First, the reference voltage source has poor stability and large temperature drift, resulting in low detection accuracy; second, it lacks a hysteresis circuit, which can easily cause oscillations during voltage fluctuations, leading to false alarms; and third, the transformer is expensive and bulky, making it unsuitable for miniaturized devices.

[0004] The second method uses an optocoupler in conjunction with a Zener diode for detection. While this method achieves isolation between the primary and secondary circuits, the Zener diode has poor temperature characteristics and low voltage regulation accuracy, typically around ±5%, which falls far short of the accuracy requirements of power protection devices. Furthermore, Zener diodes suffer from rapid aging and large parameter drift, making long-term operational reliability difficult to guarantee.

[0005] The third method involves sampling via an ADC (Analog-to-Digital Converter) and then performing digital comparison using a microprocessor. While this method offers high accuracy, it suffers from the following drawbacks: First, the sampling circuit is complex, requiring multiple components such as operational amplifiers and sample-and-hold circuits, which can easily introduce noise. Second, it relies on a microprocessor; if the microprocessor malfunctions, the entire detection function will fail, failing to meet the high reliability requirements of power protection devices. Third, the response speed is relatively slow, making it unsuitable for scenarios with rapid voltage changes.

[0006] The aforementioned existing technical solutions have the following main technical defects: Insufficient detection accuracy: Existing solutions mostly use ordinary comparators or Zener diodes as detection references, which have large temperature drift and poor stability. In the case of large temperature differences in the power system working environment, they are prone to malfunction or failure to operate.

[0007] Weak anti-interference capability: There are a lot of electromagnetic interference in the substation environment, such as high-frequency switching interference, lightning surges, etc. Existing solutions do not take into account filtering and anti-interference, and are easily affected by electromagnetic interference, leading to malfunctions.

[0008] Incomplete primary and secondary electrical isolation: Although some solutions employ isolation measures, insufficient isolation voltage levels or unreasonable isolation interface design can easily lead to coupling between primary and secondary electrical circuits in strong electromagnetic environments, causing abnormalities in the secondary system.

[0009] High power consumption: Existing solutions mostly use low-resistance voltage divider networks. When monitoring voltages such as 400V, the resistors consume a lot of power, and long-term operation will generate significant heat, affecting the lifespan and reliability of the components.

[0010] Poor maintainability: Existing solutions mostly adopt fixed parameter design, which cannot flexibly adjust the threshold according to actual application needs, and the parameters cannot be directly verified, which brings inconvenience to on-site debugging and maintenance.

[0011] Therefore, there is an urgent need to develop a high-precision, strong anti-interference, low-power, and safe isolation high-voltage busbar over-limit detection and isolation alarm module to meet the requirements of modern microcomputer protection devices for reliability, safety and accuracy. Utility Model Content

[0012] The purpose of this invention is to provide a high-voltage busbar over-limit detection and isolation alarm module for a microcomputer-based protection device. This high-voltage busbar over-limit detection and isolation alarm module features high-precision detection, strong anti-interference performance, complete electrical isolation, and low power consumption.

[0013] The above-mentioned technical objective of this utility model is achieved through the following technical solution: A high-voltage busbar over-limit detection and isolation alarm module for a microcomputer protection device includes: The high-resistance voltage divider network includes a first resistor (R43) and a second resistor (R42) connected in series to form the upper arm, and a third resistor (R38) to form the lower arm; A filter capacitor (C27) is connected in parallel to the third resistor (R38); The comparator (U17) has its cathode connected to the midpoint of the voltage divider between the upper and lower arms, its reference terminal used for threshold setting, and its anode grounded. The hysteresis network includes a feedback resistor (R41) that feeds back from the cathode of the comparator (U17) to the reference terminal; The opto-isolator (U18) has its light-emitting diode side located in the high-voltage region and its transistor side located in the low-voltage region; The LED driving network includes a current-limiting resistor (R39) connected in series with the light-emitting diode and a parallel resistor (R40); The output pull-up resistor (R44) is connected at one end to the power supply and at the other end to the transistor collector of the opto-isolator (U18). An output shaping network, including a resistor (R45) and a capacitor (C28), is connected to the output of the opto-isolator (U18).

[0014] The present invention is further configured such that: the first resistor (R43) and the second resistor (R42) of the high-resistance voltage divider network are connected in series to form a high-resistance upper arm of 750kΩ, and the third resistor (R38) is a low-resistance lower arm of 4.7kΩ, forming a high-ratio voltage divider structure.

[0015] The present invention is further configured such that the comparator (U17) is a TL431 type adjustable precision reference source, which operates in adjustable Zener mode.

[0016] The present invention is further configured such that the hysteresis network feedback resistor (R41) and the high-resistance voltage divider network together form positive feedback, generating a specific hysteresis characteristic, so that the release voltage is lower than the action voltage.

[0017] The present invention is further configured such that: the filter capacitor (C27) and the third resistor (R38) constitute a first-stage low-pass filter network, and the output shaping network resistor (R45) and capacitor (C28) constitute a second-stage low-pass filter network, forming a dual-stage filtering structure.

[0018] The present invention is further configured such that: the opto-isolator (U18) is an EL1018 type optocoupler, which has a 4kV level insulation capability between the light-emitting diode side and the transistor side.

[0019] The present invention is further configured such that the resistance values ​​of the current-limiting resistor (R39) and the parallel resistor (R40) of the LED driving network are designed to control the current of the light-emitting diode within the range of 3-8mA.

[0020] The present invention is further configured such that the output pull-up resistor (R44) and the transistor of the opto-isolator (U18) form an open collector output structure, so that the output node remains at a high level when the opto-isolator (U18) is disconnected.

[0021] This invention is further configured such that the threshold voltage of the high-resistivity voltage divider network can be expressed by formula V. TH =V REF Calculate (1+(R43+R42) / R38), where V REF This is the reference voltage for comparator (U17).

[0022] In summary, this utility model has the following beneficial effects: 1. High-precision detection: By employing the TL431 precision reference source as a comparator, which boasts a reference accuracy of ±0.5% and excellent temperature drift characteristics, combined with a high-resistivity voltage divider network, high-precision voltage limit detection is achieved. This structure ensures that the threshold voltage remains stable over a wide temperature range, significantly reducing the risk of malfunctions or failures to operate due to temperature variations and improving the reliability of the protection device.

[0023] 2. Dual Filtering Anti-interference Effect: The module adopts a dual low-pass filter structure. R38 / C27 at the input forms the first-stage low-pass filter, effectively filtering out high-frequency interference; R45 / C28 at the output forms the second-stage low-pass filter, further suppressing signal jitter and glitches. This dual filtering structure enables the system to operate stably in strong electromagnetic environments such as substations and power distribution rooms, significantly improving the system's anti-interference capability.

[0024] 3. Hardware hysteresis anti-jitter effect: The positive feedback network formed by R41 generates hysteresis characteristics, preventing the system from frequently switching states during voltage fluctuations and effectively avoiding oscillations near the threshold. The release voltage is lower than the action voltage, forming an action / release range, ensuring the stability and determinism of system operation.

[0025] 4. Complete Electrical Isolation Safety: The use of EL1018 optocouplers achieves complete electrical isolation between the high-voltage and low-voltage sides, providing 4kV-level insulation capability. This disconnects the electrical connection between the high-voltage and logic sides, eliminates ground loops, and significantly improves system safety. The opto-isolation structure ensures that primary-side faults will not be conducted to the secondary system, guaranteeing the safe and reliable operation of the microprocessor-based protection device.

[0026] 5. Low power consumption and energy saving: The high-resistivity voltage divider network consumes only about 0.21W at 400V, far lower than traditional solutions. Meanwhile, precise current control on the optocoupler LED side keeps the power consumption of the entire module in the milliwatt range during operation, reducing heat generation, extending component lifespan, and lowering the burden on the system power supply.

[0027] 6. Fail-safe characteristics: The output circuit adopts a pull-up resistor design to ensure that the output is in a high-level state when the optocoupler fails, so that the system has the characteristic of being safe even when power is lost, which conforms to the safety design principle of power system and improves the inherent safety of the system. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the circuit structure of a high-voltage busbar over-limit detection and isolation alarm module of a microcomputer protection device according to this utility model. Detailed Implementation

[0029] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present utility model, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the scope of protection of the present utility model.

[0030] like Figure 1 As shown in this embodiment, a high-voltage busbar over-limit detection and isolation alarm module for a microprocessor-based protection device is mainly used to monitor the voltage status of a 400V high-voltage busbar. When the voltage exceeds a set threshold, an alarm signal is sent to the low-voltage control side of the microprocessor-based protection device through opto-isolation. The module mainly includes four parts: a high-voltage measurement area, a comparison and hysteresis area, an opto-isolation area, and an output shaping area.

[0031] The high-voltage measurement area includes a high-resistance voltage divider network. The upper arm is formed by a first resistor R43 (360kΩ) and a second resistor R42 (390kΩ) connected in series, with a total resistance of 750kΩ. This network, together with a third resistor R38 (4.7kΩ), constitutes the voltage divider network. This high-resistance voltage divider structure ensures that power consumption is controlled to approximately 0.21W at a 400V input voltage, significantly reducing heat generation.

[0032] The third resistor R38 in the lower arm of the voltage divider chain is connected in parallel with a filter capacitor C27 (0.1μF). Together, they form a low-pass filter with a cutoff frequency of approximately 339Hz, effectively filtering out high-frequency interference such as lightning strikes and switching surges. The connection point between the upper and lower arms of the high-impedance voltage divider network forms the voltage divider midpoint, and this midpoint voltage is directly connected to the cathode of the comparator.

[0033] The comparison and hysteresis region includes comparator U17 and the hysteresis network. Comparator U17 uses a TL431 adjustable precision reference source, with three pins: cathode (K), reference (REF), and anode (A). The cathode (K) is connected to the midpoint of the voltage divider, the reference (REF) forms a comparison circuit through an internal reference voltage source and feedback resistor R41, and the anode (A) is directly grounded. The TL431 operates in adjustable Zener mode. When the voltage at the cathode (A) is higher than the reference voltage, it conducts, exhibiting a low-impedance state between the cathode (K) and anode (A); when the voltage at the cathode (K) is lower than the reference voltage, it is cut off, exhibiting a high-impedance state. The TL431's internal reference voltage is 2.495V, and combined with the external voltage divider network, a detection threshold of 400V can be precisely set. The hysteresis network consists of a feedback resistor R41 (100kΩ), which feeds back from the cathode (K) of comparator U17 to the reference terminal (REF), forming a positive feedback loop and generating a hysteresis characteristic of about 10V. This keeps the release voltage (about 390V) lower than the operating voltage (about 400V), effectively avoiding frequent switching during voltage fluctuations.

[0034] The opto-isolation area includes opto-isolator U18 and the LED driver network. Opto-isolator U18 uses an EL1018 type optocoupler with 4kV insulation capability, ensuring complete electrical isolation between the high-voltage and low-voltage sides. The LED driver network includes a current-limiting resistor R39 (1kΩ) and a parallel resistor R40 (2kΩ), which together control the LED current within the 3-8mA range, ensuring reliable conduction and extending LED lifespan. When comparator U17 is turned on, the LED receives sufficient current to begin emitting light, driving the optocoupler transistor to conduct; when comparator U17 is turned off, there is no current to the LED, and the optocoupler transistor is turned off.

[0035] The output shaping region includes an output pull-up resistor R44 (100kΩ) and an output shaping network. One end of the output pull-up resistor R44 is connected to the VCC power supply, and the other end is connected to the collector of the optocoupler U18 transistor, forming an open-collector output structure. When the optocoupler transistor is off, the output node WY1 is pulled high through the output pull-up resistor R44, indicating a normal state; when the optocoupler transistor is on, the output node WY1 is pulled low to near ground, indicating an over-limit alarm state. The output shaping network consists of a resistor R45 (100kΩ) and a capacitor C28 (0.1μF), connected to the output terminal WY1, forming a second-stage low-pass filter network to further filter out transients and glitches caused by the optocoupler switching action, ensuring the stability of the output signal.

[0036] The threshold voltage is calculated as follows: Let the reference voltage of TL431 be V. REF (Approximately 2.495V), then the operating threshold voltage VTH can be obtained through the formula V TH =V REF Calculate using (1 + (R43 + R42) / R38). Substituting R43 = 360kΩ, R42 = 390kΩ, and R38 = 4.7kΩ, we can obtain V. TH ≈399~402V, consistent with the nominal value of 400V. Hysteresis voltage V HYS It can be obtained through formula V HYS ≈V REF Estimate using (R41 / R38)·((R43+R42) / (R43+R42+R38)).

[0037] The working principle of this invention is as follows: When the 400V high-voltage bus voltage under test is lower than the set threshold (approximately 400V), after passing through the high-resistance voltage divider network, the midpoint voltage of the voltage divider is lower than the reference voltage of TL431. TL431 is in the off state, no current flows through the LED driver network, the LED of optocoupler U18 does not light up, the optocoupler transistor is off, and the output terminal WY1 is kept at a high level through the pull-up resistor R44, indicating a normal state. When the 400V high-voltage bus voltage rises and exceeds the set threshold, the midpoint voltage of the voltage divider exceeds the reference voltage of TL431, TL431 conducts, current flows through the LED driver network, the LED of optocoupler U18 lights up, the optocoupler transistor conducts, and the output terminal WY1 is pulled low to near ground level, indicating an over-limit alarm state. When the high-voltage bus voltage drops again and falls below the release voltage (approximately 390V), due to the effect of the hysteresis network, TL431 is turned off again, and the system returns to the normal state. Throughout the process, the high-voltage side and the low-voltage side are completely electrically isolated through optocoupler U18 to ensure system safety.

[0038] In implementing this utility model, the high-voltage side components should be selected with a rated withstand voltage ≥250V / piece, resistance to humidity and heat, and low drift. The PCB layout should ensure sufficient creepage distance (≥6-8mm) between the high-voltage and low-voltage areas and be coated with anti-fouling varnish. Kelvin routing should be used for the peripheral circuits of comparator U17 to reduce sampling errors, and the LED-side circuit area of ​​optocoupler U18 should be minimized to reduce interference coupling. During debugging, the 400V terminal can be scanned using an adjustable power supply, and the operating voltage and release voltage can be recorded and compared with theoretical values ​​to verify whether the hysteresis characteristics and response time meet the requirements.

[0039] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A high-voltage busbar over-limit detection and isolation alarm module for a microcomputer protection device, characterized in that, include: The high-resistance voltage divider network includes a first resistor (R43) and a second resistor (R42) connected in series to form the upper arm, and a third resistor (R38) to form the lower arm; A filter capacitor (C27) is connected in parallel to the third resistor (R38); The comparator (U17) has its cathode connected to the midpoint of the voltage divider between the upper and lower arms, its reference terminal used for threshold setting, and its anode grounded. The hysteresis network includes a feedback resistor (R41) that feeds back from the cathode of the comparator (U17) to the reference terminal; and an opto-isolator (U18) with its LED side located in the high-voltage region and its transistor side located in the low-voltage region. The LED driving network includes a current-limiting resistor (R39) connected in series with the light-emitting diode and a parallel resistor (R40); The output pull-up resistor (R44) is connected at one end to the power supply and at the other end to the transistor collector of the opto-isolator (U18). An output shaping network, including a resistor (R45) and a capacitor (C28), is connected to the output of the opto-isolator (U18).

2. The high-voltage busbar over-limit detection and isolation alarm module according to claim 1, characterized in that, The high-resistance voltage divider network consists of a first resistor (R43) and a second resistor (R42) connected in series to form a high-resistance upper arm in the range of 750kΩ, and a third resistor (R38) is a low-resistance lower arm in the range of 4.7kΩ, forming a high-ratio voltage divider structure.

3. The high-voltage busbar over-limit detection and isolation alarm module according to claim 1, characterized in that, The comparator (U17) is a TL431 adjustable precision reference source, operating in adjustable Zener mode.

4. The high-voltage busbar over-limit detection and isolation alarm module according to claim 1, characterized in that, The hysteresis network feedback resistor (R41) together with the high-resistance voltage divider network forms a positive feedback, generating a specific hysteresis characteristic that makes the release voltage lower than the operating voltage.

5. The high-voltage busbar over-limit detection and isolation alarm module according to claim 1, characterized in that, The filter capacitor (C27) and the third resistor (R38) constitute the first-stage low-pass filter network, and the output shaping network resistor (R45) and capacitor (C28) constitute the second-stage low-pass filter network, forming a dual-stage filtering structure.

6. The high-voltage busbar over-limit detection and isolation alarm module according to claim 1, characterized in that, The optocoupler (U18) is an EL1018 type optocoupler, which has a 4kV insulation capability between the light-emitting diode side and the transistor side.

7. The high-voltage busbar over-limit detection and isolation alarm module according to claim 1, characterized in that, The resistance values ​​of the current-limiting resistor (R39) and parallel resistor (R40) in the LED driver network are designed to control the LED current within the range of 3-8mA.

8. The high-voltage busbar over-limit detection and isolation alarm module according to claim 1, characterized in that, The output pull-up resistor (R44) and the transistor of the opto-isolator (U18) form an open-collector output structure, so that the output node remains at a high level when the opto-isolator (U18) is disconnected.

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