Differential protection device

Abstract

The utility model provides a differential protection device, which is used for solving the problem of differential protection misoperation caused by instantaneous TA disconnection in the prior art. Comprising a data acquisition module, a microprocessor, a power supply module and a protection driving module, the data acquisition module, the power supply module and the protection driving module are all electrically connected with the microprocessor, the data acquisition module comprises a first current transformer, a second current transformer and a digital-to-analog conversion module, the first current transformer and the second current transformer are connected in parallel and then electrically connected with the digital-to-analog conversion module, and the digital-to-analog conversion module is electrically connected with the microprocessor. According to the device, the first current transformer and the second current transformer are connected in parallel and then are connected with the data acquisition module, so that when one current transformer is broken, whether differential protection is needed or not can be distinguished in time, and misoperation caused by disconnection of the current transformers is effectively avoided.

Description

Technical field:

[0001] The utility model relates to the technical field of electronic information, in particular to a differential protection device. Background technology:

[0002] In the power system, the differential protection device is an important protection device used to quickly cut off the fault line or equipment to prevent the fault from expanding. The differential protection device realizes the protection function by comparing the magnitude and phase of the current on each side of the power system. However, in practical applications, due to the characteristics of the current transformer (TA), the differential protection device may face some technical challenges. Traditional differential protection devices usually provide protection based on steady-state current. This means that they focus mainly on the long-term average value or effective value of the current, rather than the instantaneous value of the current. However, instantaneous TA disconnection (instantaneous current transformer fault) may cause the differential protection device to misjudge it as a fault state, thereby triggering unnecessary action. The traditional differential protection device has limited ability to suppress external interference signals. For example, events such as lightning and system short circuit may generate strong interference signals, which may be mistaken by the differential protection device as fault signals, resulting in incorrect protection actions. In order to solve the above problems, the purpose of the present invention is to provide a differential protection device that can overcome the shortcomings of the prior art and improve the accuracy and adaptability of differential protection. Specifically, the present invention realizes comprehensive protection and efficient management of the power system by introducing an identification mechanism for instantaneous TA disconnection, a suppression function for external interference signals, and an adaptive parameter adjustment mechanism. Utility model content:

[0003] Based on the above background, in order to overcome the problem of differential protection malfunction caused by instantaneous TA line break, the present invention provides a differential protection device, which mainly includes: a data acquisition module, a microprocessor, a power supply module and a protection drive module; the data acquisition module 3, the power supply module and the protection drive module are all electrically connected to the microprocessor, the data acquisition module includes a first current transformer, a second current transformer and a digital-to-analog conversion module, the first current transformer and the second current transformer are electrically connected to the digital-to-analog conversion module after being connected in parallel, and the digital-to-analog conversion module is electrically connected to the microprocessor.

[0004] Preferably, the protection drive module includes: a current transformer line break lockout module and a protection output relay. The current transformer line break lockout module is connected to the microprocessor module, and is used to determine the line break information of the first current transformer or the second current transformer, and issue corresponding protection instructions to the protection output relay based on the line break information. The protection output relay is connected to the circuit breaker of the protected device.

[0005] Preferably, the differential protection device further comprises: a disconnection indication module; the disconnection indication module comprises a disconnection indicator light and an alarm module; the disconnection indicator light and the alarm module are both electrically connected to the microprocessor.

[0006] Preferably, the differential protection device further comprises: an information communication module; the information communication module is electrically connected to the microprocessor, and the information communication module is communicatively connected to the wireless transmission module of the host computer.

[0007] Preferably, the differential protection device further comprises: an input module and a display module, and both the input module and the display module are electrically connected to the microprocessor.

[0008] Preferably, the data acquisition module includes a first current transformer and a secondary winding of a second current transformer, both of which are connected to two ends of a first resistor R4, one end of the first resistor R4 is grounded through a first capacitor C4, the other end of the first resistor R4 is connected to a bias voltage circuit, and is simultaneously connected to one end of the second resistor R3, the other end of the second resistor R3 and one end of the first resistor R4 are connected to a reverse amplifier circuit, and the output end of the reverse amplifier circuit is connected to a digital-to-analog conversion module.

[0009] Preferably, the line disconnection information issues a corresponding protection instruction represented by the high and low levels of the switch output circuit, and the switch output circuit adopts an optocoupler conversion circuit, the input end of the optocoupler conversion circuit is connected to the microprocessor, and the output end is connected to the protection output relay.

[0010] The beneficial effects of the utility model include: the differential protection device adopts a data acquisition module after the first current transformer and the second current transformer are connected in parallel, and can promptly distinguish whether differential protection is needed when one current transformer is broken, effectively avoiding false operation caused by current transformer breakage, and improving the protection accuracy and reliability of the power system. Moreover, the information communication module can wirelessly communicate with the host computer to realize remote monitoring and control, enhance the system's intelligent monitoring capability and operational convenience, and provide a strong guarantee for the safe and stable operation of the power system. Description of the drawings:

[0011] Attached Figure 1 It is a structural schematic diagram of a differential protection device of a preferred embodiment;

[0012] Attached Figure 2 is a circuit diagram of a data acquisition module of a preferred embodiment;

[0013] Attached Figure 3 is a circuit diagram of a bias voltage circuit of a preferred embodiment;

[0014] Attached Figure 4 This is a circuit diagram of a switch output circuit of a preferred embodiment. Specific implementation method:

[0015] In view of this, the present invention provides a differential protection device, and the preferred embodiments of the present invention are described below in conjunction with the accompanying drawings of the specification.

[0016] In order to make the purpose, technical solution and advantages of the embodiment of the utility model clearer, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is a part of the embodiment of the utility model, not all of the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0017] In addition, it should be understood that in the description of the embodiments of the present invention, words such as "first" and "second" are only used to distinguish the description purpose, and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order.

[0018] See also Figure 1 As shown, a differential protection device includes: a data acquisition module 3, a microprocessor 1, a power module and a protection drive module 5; the data acquisition module 3, the power module and the protection drive module 5 are all electrically connected to the microprocessor 1, the data acquisition module 3 includes a first current transformer, a second current transformer and a digital-to-analog conversion module, the first current transformer and the second current transformer are electrically connected to the digital-to-analog conversion module after being connected in parallel, and the digital-to-analog conversion module is electrically connected to the microprocessor 1.

[0019] Specifically, the basic principle of the differential protection device is to monitor and compare the current signals measured by the current transformer (CT) in real time to determine whether there is a fault in the power system. The device collects the current signals entering and leaving the power equipment through two parallel current transformers. These signals are converted into digital signals by the digital-to-analog conversion module and sent to the microprocessor 1 for analysis.

[0020] The microprocessor 1 compares the two current signals according to the preset differential protection algorithm to see if there is any imbalance. If there is a significant difference between the current signals, exceeding the set threshold, this may indicate that a fault has occurred inside the power equipment. In this case, the microprocessor 1 will issue a protection instruction, triggering the circuit breaker 6 to operate through the protection output relay in the protection drive module 5, thereby cutting off the connection between the faulty part and the system and preventing the fault from spreading.

[0021] At the same time, the device also includes a current transformer disconnection locking module for monitoring the working status of the current transformer. If a CT disconnection is detected, the module will send a locking signal to prevent the protection device from malfunctioning. In addition, the device also has a disconnection indication module 2, an information communication module, an input and output module and a display module 401, which provide fault indication, remote monitoring and human-computer interaction functions, enhancing the practicality and ease of operation of the device.

[0022] See also Figure 2 and Figure 3 As shown, the data acquisition module 3 includes a first current transformer and a secondary winding of a second current transformer, both of which are connected to two ends of a first resistor R4, one end of the first resistor R4 is grounded through a first capacitor C4, the other end of the first resistor R4 is connected to a bias voltage circuit, and is simultaneously connected to one end of a second resistor R3, the other end of the second resistor R3 and one end of the first resistor R4 are connected to a reverse amplifier circuit, and the output end of the reverse amplifier circuit is connected to a digital-to-analog conversion module.

[0023] The first current transformer and the second current transformer are installed in parallel on both sides of the incoming and outgoing lines of the protected equipment to monitor the current information in real time.

[0024] The digital-to-analog conversion module is responsible for converting the analog current signal output by the transformer into a digital signal so that the microprocessor 1 can process it. Figure 3 In the bias voltage circuit, IC1A is a 2-channel integrated operational amplifier. After the 3.3V voltage is divided by two resistors R1 and R2 with the same resistance value, it is input to the same-direction end of the first operational amplifier IC1A. The purpose is to output a 1.65V voltage value without any interference through the first operational amplifier. The output end is 1V65_CT in the figure. Figure 2 CT is a current transformer, which converts the current on the primary side to the secondary side through a transformation ratio. P1 / P2 / P3 / P4 is the first current transformer; P5 / P6 / P7 / P8 is another alternative model of the second current transformer. After the secondary current value passes through resistor R4, it is converted into a voltage value. Since the voltage value has waveforms in both the positive and negative half cycles of the Y axis at this time, the waveform of the positive half cycle can be read by the MCU, but the waveform of the negative half cycle cannot be read by the MCU. Therefore, the 1.65V voltage output from the bias voltage circuit is superimposed with the voltage value of resistor R4. At this time, the secondary voltage waveform is all displayed in the positive half cycle of the Y axis, and the MCU can correctly read the value of the digital-to-analog conversion module ADC. The second operational amplifier IC1B is combined with resistors R5 / R6 to form an operational amplifier reverse amplifier circuit, which amplifies the input value and transmits it to the microprocessor 1MCU.

[0025] The protection driving module 5 includes: a current transformer disconnection locking module 501 and a protection outlet relay 502. The current transformer disconnection locking module 501 is connected to the microprocessor 1 module, and is used to determine the disconnection information of the first current transformer or the second current transformer, and send a corresponding protection instruction to the protection outlet relay 502 according to the disconnection information. The protection outlet relay 502 is connected to the circuit breaker 6 of the protected device. The disconnection information sends a corresponding protection instruction, which is represented by the high and low levels of the switch output circuit. The switch output circuit adopts an optocoupler conversion circuit. The input end of the optocoupler conversion circuit is connected to the microprocessor 1, and the output end is connected to the protection outlet relay 502. In addition, the first current transformer and the second current transformer form a main and standby system. After any one of them is disconnected, the disconnection analysis can also be performed by referring to the situation of the other current transformer.

[0026] Isolation protection of optocoupler conversion circuit: The switch output circuit adopts optocoupler conversion circuit to achieve electrical isolation between the microprocessor 1 and the protection output relay 502, thereby enhancing the safety of the system.

[0027] The current transformer disconnection locking module 501 monitors the status of the first current transformer and the second current transformer through the microprocessor 1, and once a disconnection is detected, a signal is immediately sent to the microprocessor 1. The microprocessor 1 sends a protection instruction to the protection output relay 502 through the switch output circuit according to the disconnection information and the preset protection strategy, thereby controlling the action of the circuit breaker 6.

[0028] The microprocessor 1, as the core of the entire protection device, receives digital signals from the data acquisition module 3 and runs the differential protection algorithm for processing. The microprocessor 1 is also responsible for communicating with the power module, the protection drive module 5, the disconnection indication module 2, the information communication module, and the input and display module 401 to ensure the coordinated operation of the entire system.

[0029] The TA disconnection analysis method is as follows:

[0030] When any of the following conditions is met, the judgment of instantaneous TA disconnection is skipped: 1. The maximum phase current on one side before starting is less than 0.15 times the rated current of the high-voltage side of the transformer; 2. The current on either side after starting increases compared to before starting; 3. After the differential protection is started, the maximum phase current on one side is less than 20% of the rated current of that side, then the TA on that side is not considered to be disconnected.

[0031] Alternatively, when the following conditions are met at the same time, the CT line break will be locked for differential protection. The specific criteria are as follows: 1. When the differential current of any phase is greater than 0.15 times the rated current of the transformer high-voltage side; 2. Only one phase's protection current is zero, and the difference between the current of the other two phases and the current before the differential protection is started should be less than 0.05 times the rated current of the transformer high-voltage side.

[0032] The disconnection indicator module 2 includes a disconnection indicator light and an alarm module; the disconnection indicator light and the alarm module are both electrically connected to the microprocessor 1. When the disconnection indicator light and the alarm module detect disconnection or other abnormal conditions, they send visual and auditory alarms to the operator so that the operator can take corresponding measures in time, which can be controlled remotely or manually operated locally.

[0033] Information communication module 7; the information communication module 7 is electrically connected to the microprocessor 1, and the information communication module 7 is communicatively connected to the wireless transmission module 8 of the host computer 9 to realize remote monitoring and control functions and improve the intelligence level of the power system.

[0034] Input module 402 and display module 401, both of which are electrically connected to microprocessor 1. Input module 402 allows operators to set protection parameters and view system status, while display module 401 intuitively displays system information and fault records, making it convenient for operators to monitor and maintain.

[0035] In summary, the design of the entire differential protection device takes into account reliability, real-time and easy operation, which can effectively prevent overcurrent, short circuit and other faults in the power system and ensure the safe and stable operation of the power system. Through these advanced designs and functions, the device can meet the increasingly high requirements of modern power systems for protection equipment.

Claims

1. A differential protection device, characterized in that: include: Data acquisition module, microprocessor, power module and protection drive module; The data acquisition module, the power supply module and the protection drive module are all electrically connected to the microprocessor. The data acquisition module includes a first current transformer, a second current transformer and a digital-to-analog conversion module. The first current transformer and the second current transformer are electrically connected to the digital-to-analog conversion module after being connected in parallel. The digital-to-analog conversion module is electrically connected to the microprocessor.

2. The differential protection device according to claim 1, characterized in that: The protection drive module includes: a current transformer disconnection locking module and a protection output relay. The current transformer disconnection locking module is connected to the microprocessor module, and is used to determine the disconnection information of the first current transformer or the second current transformer, and issue corresponding protection instructions to the protection output relay according to the disconnection information. The protection output relay is connected to the circuit breaker of the protected device.

3. The differential protection device according to claim 1, characterized in that: Also includes: A disconnection indication module; the disconnection indication module includes a disconnection indicator light and an alarm module; the disconnection indicator light and the alarm module are both electrically connected to the microprocessor.

4. The differential protection device according to claim 1, characterized in that: Also includes: Information communication module; the information communication module is electrically connected to the microprocessor, and the information communication module is communicatively connected to the wireless communication module of the host computer.

5. The differential protection device according to claim 1, characterized in that: Also includes: An input module and a display module, wherein both the input module and the display module are electrically connected to the microprocessor.

6. The differential protection device according to claim 1, characterized in that: The data acquisition module comprises a first current transformer and a second current transformer, both of which have secondary windings connected to two ends of a first resistor (R4); one end of the first resistor (R4) is grounded via a first capacitor (C4); the other end of the first resistor (R4) is connected to a bias voltage circuit and is simultaneously connected to one end of a second resistor (R3); the other end of the second resistor (R3) and one end of the first resistor (R4) are connected to a reverse amplifier circuit; and the output end of the reverse amplifier circuit is connected to the digital-to-analog conversion module.

7. The differential protection device according to claim 2, characterized in that: The corresponding protection instructions issued by the disconnection information are represented by the high and low levels of the switch output circuit. The switch output circuit adopts an optocoupler conversion circuit. The input end of the optocoupler conversion circuit is connected to the microprocessor, and the output end is connected to the protection output relay.

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