A re-zero sequence voltage detection system for electromagnetic feeder automation terminal reconstruction

Abstract

A kind of for electromagnetic feeder automation terminal reconstruction again zero sequence voltage detection system, including input protection module, signal conversion module, isolation conversion module and output module;The input protection module is connected to the output end of zero sequence voltage sensor, for current limiting and overvoltage protection;The signal conversion module includes operational amplifier unit, for receiving the signal of the input protection module, and the positive and negative alternating voltage output by zero sequence voltage sensor is converted into positive voltage signal by reference source;The isolation conversion module includes isolated operational amplifier unit, for the electrical isolation of the output of the signal conversion module;The output module includes difference conversion single-end circuit unit, for converting the differential signal after isolation into single-ended voltage signal, to connect external acquisition device.By using electronic operational amplifier and other electronic devices instead of traditional mutual inductor device, meet isolation and impedance, without high algorithm chip software calculation, to detect zero sequence voltage.

Description

Technical Field

[0001] This utility model relates to the field of feeder automation terminal technology, specifically a re-zero sequence voltage detection system for the transformation of electromagnetic feeder automation terminals. Background Technology

[0002] Feeder Terminal Units (FTUs) are control devices for distribution automation switches. Over decades of development, distribution networks have seen the installation of numerous automated switches to isolate faults locally and quickly restore power to non-faulty areas. However, low- and medium-voltage distribution networks are often low-current grounding systems, resulting in weak and easily concealed grounding fault characteristics. Furthermore, with increasing electricity consumption and the number of users, fault diagnosis and maintenance have become inconvenient. As distribution network technology advances, FTUs in the distribution network require fault location capabilities to shorten power outage times and facilitate maintenance. Many older automated switches and their associated FTUs lack fault location capabilities and their effectiveness in monitoring grounding faults is unsatisfactory. Currently, there is a large stock of old automated switches and their associated FTUs, leading to high overall replacement costs. Therefore, local power grid companies are undertaking upgrades and renovations of existing older FTUs.

[0003] The current upgrade involves adding a fault location device next to the existing FTU equipment. Both the fault location device and the FTU need to acquire the zero-sequence voltage signal from the zero-sequence voltage sensor in the distribution automation switch. National standards require that this zero-sequence voltage sensor have a requirement for the total input impedance of the subsequent acquisition circuit, requiring an input impedance greater than 2MΩ. Older electromagnetic FTUs typically use high-impedance current transformers (10V–3.53V or 1–0.353V) for signal acquisition and isolation. Their design generally doesn't consider the subsequent need for zero-sequence voltage re-measurement. To minimize size and save costs, they are often designed with a minimum input impedance of 2.1MΩ, making it impossible for other manufacturers to directly utilize the output of the existing zero-sequence voltage sensor in the automation switch when adding this zero-sequence voltage acquisition function. When re-detecting the zero-sequence voltage, high-performance computing chips and software are typically used to measure the three-phase voltages (A, B, and C) and perform complex phasor calculations to obtain the zero-sequence voltage value. However, the high-performance computing chips incur significant costs in terms of heat dissipation, size, price, and the manual labor required for the software algorithms. Utility Model Content

[0004] The purpose of this invention is to provide a re-zero sequence voltage detection system for the retrofitting of electromagnetic feeder automation terminals, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, this utility model provides the following technical solution: A zero-sequence voltage detection system for the retrofitting of automated terminals of electromagnetic feeders includes an input protection module, a signal conversion module, an isolation conversion module, and an output module. The input protection module is connected to the output terminal of the zero-sequence voltage sensor and is used for current limiting and overvoltage protection; The signal conversion module includes an operational amplifier unit, which is used to receive the signal from the input protection module and convert the positive and negative AC voltages output by the zero-sequence voltage sensor into a positive voltage signal through a reference source. The isolation conversion module includes an isolation operational amplifier unit, which is used to electrically isolate the output of the signal conversion module; The output module includes a differential-to-single-ended circuit unit, which converts the isolated differential signal into a single-ended voltage signal for connection to an external acquisition device.

[0006] In one possible implementation, the input protection module includes a current-limiting protection resistor with a resistance of 1KΩ. The current-limiting protection resistor is directly connected to the output terminal of the zero-sequence voltage sensor to limit the input current.

[0007] In one possible implementation, the operational amplifier unit of the signal conversion module includes a first operational amplifier and a second operational amplifier; the first operational amplifier is configured as a voltage follower for converting high-impedance input to low-impedance output; the second operational amplifier is configured with gain reduction and voltage boosting circuitry.

[0008] In one possible implementation, the gain reduction and voltage boosting circuit of the second operational amplifier includes a first resistor, a second resistor, a third resistor, and a fourth resistor; wherein the first resistor and the third resistor have a resistance of 90KΩ, and the second resistor and the fourth resistor have a resistance of 10KΩ.

[0009] In one possible implementation, the isolation operational amplifier unit of the isolation conversion module employs an isolation operational amplifier chip to achieve signal isolation through digital modulation and demodulation; the differential-to-single-ended circuit unit of the output module includes a third operational amplifier and multiple matching resistors to convert the isolated differential output into a single-ended voltage.

[0010] In one possible implementation, an overvoltage protection device is also included. The overvoltage protection device is a gas discharge tube or a varistor, connected between the output terminal of the zero-sequence voltage sensor and the input protection module, for suppressing high-voltage pulse interference.

[0011] In one possible implementation, the single-ended voltage signal output terminal of the output module is connected to the analog-to-digital converter interface of the microcontroller for subsequent data acquisition and processing.

[0012] Compared with the prior art, the present invention has the following advantages: 1. By using electronic operational amplifiers and other electronic devices to replace the traditional pure software method, the required electrical isolation requirements are met. It eliminates the need for expensive, bulky, high-heat-generating, and labor-intensive high-computing-power chips and software to calculate the zero-sequence voltage and obtain the result; that is, it replaces the traditional software method with a hardware method.

[0013] 2. Operational amplifier chips and isolation operational amplifier chips are used. Taking advantage of the high input impedance characteristics of the operational amplifier, the total impedance after being connected in parallel with the high impedance current transformer of the FTU meets the 2M ohm impedance requirement of the distribution network electromagnetic current transformer. 3. The input signal is transformed using an operational amplifier. The original positive and negative AC voltages output by the zero-sequence voltage sensor of the automatic switch are amplified by a reference source and converted into positive voltages by an operational amplifier. The positive voltage is then isolated and converted into a single-ended voltage using an isolation operational amplifier and a differential-to-single-ended circuit, which can be directly acquired and used by a data acquisition device. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall structure of this utility model; Figure 2 This is a schematic diagram of the circuit structure of this utility model; Figure 3 This is a structural diagram of the MCU microcontroller U4A connected to this utility model. Detailed Implementation

[0015] To further illustrate the technical means and effects adopted by this utility model in order to achieve the intended utility model purpose, the following detailed description of the specific implementation methods, structure, features and effects of this utility model is provided in conjunction with the accompanying drawings and preferred embodiments.

[0016] like Figure 1-3 As shown, a zero-sequence voltage detection system for the retrofitting of electromagnetic feeder automation terminals includes an input protection module 10, a signal conversion module 20, an isolation conversion module 30, and an output module 40. The input protection module 10 is connected to the output terminal of the zero-sequence voltage sensor and is used for current limiting and overvoltage protection; it includes a current limiting protection resistor R5, the current limiting protection resistor R5 has a resistance of 1KΩ and an accuracy of 1%, and the current limiting protection resistor R5 is directly connected to the output terminal of the zero-sequence voltage sensor.

[0017] The signal conversion module 20 includes an operational amplifier unit, which is used to receive the signal from the input protection module and convert the positive and negative AC voltages output by the zero-sequence voltage sensor into a positive voltage signal through a reference source. The operational amplifier unit includes a first operational amplifier U1A and a second operational amplifier U1B. The first operational amplifier U1A is configured as a voltage follower for converting high-impedance input to low-impedance output. The second operational amplifier U1B is configured with a gain reduction and voltage boosting circuit, which includes multiple precision resistors to reduce the input signal by a factor of 10 and boost it to a common-mode voltage of 1.024V through a 1.024V reference source.

[0018] Specifically, the gain reduction and voltage boost circuit includes a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4; wherein the first resistor R1 and the third resistor R3 have a resistance of 90KΩ and an accuracy of 0.1%, and the second resistor R2 and the fourth resistor R4 have a resistance of 10KΩ and an accuracy of 0.1%; the various precision resistors work together to achieve precise scaling and biasing of the input signal.

[0019] The isolation conversion module 30 includes an isolation operational amplifier unit for electrically isolating the output of the signal conversion module; the isolation operational amplifier unit uses an isolation operational amplifier chip U2 for achieving signal isolation through digital modulation and demodulation. The output module 40 includes a differential-to-single-ended circuit unit, used to convert the isolated differential signal into a single-ended voltage signal for connection to an external acquisition device. The differential-to-single-ended circuit unit includes a third operational amplifier U3 and multiple matching resistors, used to convert the isolated differential output into a single-ended voltage. The matching resistors are four resistors R6 to R9, each with a resistance of 10KΩ and an accuracy of 0.1%.

[0020] In this invention, the operational amplifier unit has an input impedance of over 100 GΩ. After being connected in parallel with the original high-impedance current transformer of the electromagnetic feeder automation terminal (FTU), the total impedance meets the 2 MΩ requirement of the distribution network. The reference source is 1.024V, which is used to raise the overall input signal by 1.024V and reduce the gain by 10 times.

[0021] Furthermore, the zero-sequence voltage detection system of this utility model also includes an overvoltage protection device, which is a gas discharge tube GDT1 or a varistor, connected between the output terminal of the zero-sequence voltage sensor and the input protection module, and is used to suppress high-voltage pulse interference.

[0022] The single-ended voltage signal output terminal of the output module is connected to the analog-to-digital converter (ADC) interface of the microcontroller U4A for subsequent data acquisition and processing; wherein, the microcontroller is configured to output to an external acquisition module through a general-purpose input / output interface (such as PA9 and PA10).

[0023] In use, the output terminal of the zero-sequence voltage sensor is electrically connected to R5. The detection system of this invention reduces the zero-sequence voltage amplitude by a factor of 10 and increases the overall voltage by 1.024V. The value is then output through the pin of the third amplifier U3 (pin number 5 in the figure) to the ADC interface of the microcontroller U4A. Then, it is output to other supporting acquisition modules through the output interfaces PA9 and PA10 on the first control chip U4A.

[0024] In this invention, the first operational amplifier U1A chip and the second operational amplifier U1B chip are the existing TI OPA2991IDR chip, the isolation operational amplifier chip U2 is the CA-IS1311BG chip from Sichuan Microelectronics, the third operational amplifier U3 chip is the TLV9061IDBVR from TI, and the control chip U4A is the STM32L431RCT6 from STMicroelectronics.

[0025] In the description of this utility model, it should be understood that the terms "coaxial", "bottom", "one end", "top", "middle", "other end", "upper", "side", "top", "inner", "front", "center", "both ends", "left and right", "front and back", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0026] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "setting," "connection," "fixing," "screw connection," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0027] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Although the present utility model has been disclosed above with reference to a preferred embodiment, it is not intended to limit the present utility model. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present utility model. Any indirect modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present utility model without departing from the scope of the present utility model shall fall within the scope of the present utility model.

Claims

1. A re-zero-sequence voltage detection system for the retrofitting of automated terminals of electromagnetic feeders, characterized in that, It includes an input protection module, a signal conversion module, an isolation conversion module, and an output module; The input protection module is connected to the output terminal of the zero-sequence voltage sensor and is used for current limiting and overvoltage protection; The signal conversion module includes an operational amplifier unit, which is used to receive the signal from the input protection module and convert the positive and negative AC voltages output by the zero-sequence voltage sensor into a positive voltage signal through a reference source. The isolation conversion module includes an isolation operational amplifier unit for electrically isolating the output of the signal conversion module; The output module includes a differential-to-single-ended circuit unit, which converts the isolated differential signal into a single-ended voltage signal for connection to an external acquisition device.

2. The zero-sequence voltage detection system for the retrofitting of electromagnetic feeder automation terminals according to claim 1, characterized in that, The input protection module includes a current-limiting protection resistor with a resistance of 1KΩ. The current-limiting protection resistor is directly connected to the output terminal of the zero-sequence voltage sensor to limit the input current.

3. The zero-sequence voltage detection system for the retrofitting of electromagnetic feeder automation terminals according to claim 1, characterized in that, The operational amplifier unit of the signal conversion module includes a first operational amplifier and a second operational amplifier; the first operational amplifier is configured as a voltage follower for converting high-impedance input to low-impedance output; the second operational amplifier is configured with gain reduction and voltage boosting circuits.

4. The zero-sequence voltage detection system for the retrofitting of electromagnetic feeder automation terminals according to claim 3, characterized in that, The gain reduction and voltage boost circuit of the second operational amplifier includes a first resistor, a second resistor, a third resistor, and a fourth resistor; wherein the resistance of the first resistor and the third resistor is 90KΩ, and the resistance of the second resistor and the fourth resistor is 10KΩ.

5. The zero-sequence voltage detection system for the retrofitting of electromagnetic feeder automation terminals according to claim 1, characterized in that, The isolation operational amplifier unit of the isolation conversion module uses an isolation operational amplifier chip to achieve signal isolation through digital modulation and demodulation; the differential-to-single-ended circuit unit of the output module includes a third operational amplifier and multiple matching resistors to convert the isolated differential output into a single-ended voltage.

6. The zero-sequence voltage detection system for the retrofitting of electromagnetic feeder automation terminals according to claim 1, characterized in that, It also includes an overvoltage protection device, which is a gas discharge tube or a varistor, connected between the output terminal of the zero-sequence voltage sensor and the input protection module, to suppress high-voltage pulse interference.

7. The zero-sequence voltage detection system for the retrofitting of electromagnetic feeder automation terminals according to claim 1, characterized in that, The single-ended voltage signal output terminal of the output module is connected to the analog-to-digital converter interface of the microcontroller for subsequent data acquisition and processing.

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