WO2022151877A1

WO2022151877A1 - Disconnection detection method and apparatus for dual-core current transformer, and breaker

Info

Publication number: WO2022151877A1
Application number: PCT/CN2021/136631
Authority: WO
Inventors: 邵建国; 孙伟锋; 顾海峰
Original assignee: 常熟开关制造有限公司(原常熟开关厂）
Priority date: 2021-01-15
Filing date: 2021-12-09
Publication date: 2022-07-21
Also published as: CN112881946B; CN112881946A

Abstract

A disconnection detection method for a dual-core current transformer. A dual-core current transformer is provided with an energy supply coil (L1) that is used for extracting electric energy from a bus, and a measurement coil (L2) that is used for measuring a bus current. A voltage signal processing circuit is connected to an output end of the energy supply coil (L1), and is configured to output an indication signal S when the bus current is greater than or equal to I. A signal output condition of the voltage signal processing circuit and a bus current measurement value Irms obtained by the measurement coil (L2) are continuously monitored, and a disconnection fault of the dual-core current transformer is detected and determined according to a monitoring result. Further provided are a disconnection detection apparatus for a dual-core current transformer, and a breaker. Real-time online detection of a disconnection fault of an energy supply coil (L1) and a measurement coil (L2) of a dual-core current transformer can be realized, and a circuit is simple, and the cost is low.

Description

Two-core current transformer disconnection detection method, device and circuit breaker

technical field

The invention relates to a method for detecting disconnection of a transformer, in particular to a method for detecting disconnection of a dual-core current transformer.

Background technique

Circuit breakers are widely used as important components of low-voltage power distribution systems, and they undertake the task of protecting power distribution networks and electrical equipment from electrical faults such as overload and short circuit. Traditional intelligent circuit breakers use single-core current transformers as energy supply and current sampling components. With the improvement of users' requirements for measurement accuracy, circuit breakers using dual-core current transformers have appeared, that is, using iron-core coils as energy supply elements and Rogowski air-core coils as current sampling elements. Although the possibility of current transformer circuit disconnection is small, once the current transformer is disconnected (for two-core current transformers, whether the iron core coil is disconnected or the air-core coil is disconnected), it will cause the circuit breaker to refuse to operate. It is necessary to detect and identify the disconnection fault of the transformer of the circuit breaker.

technical problem

In the prior art, most of the intelligent circuit breakers using dual-core current transformers do not have the function of real-time monitoring of the status of the transformers, while a few circuit breakers with the status monitoring function of the current transformers only realize the Rogowski air-core coil. (measuring coil) to judge whether the wire is broken, but it is impossible to judge whether the iron core power supply coil is broken. For example, by applying a bias level to the Rogowski air-core coil and detecting the bias level, the identification of the disconnection of the Rogowski air-core coil is realized, but the disconnection of the iron-core energy supply coil is not determined.

technical solutions

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for detecting disconnection of a dual-core current transformer, which can realize real-time online detection of the disconnection fault of the power supply coil and the measuring coil of the dual-core current transformer, and The circuit is simple and the realization cost is low.

The present invention specifically adopts the following technical solutions to solve the above technical problems.

A method for detecting disconnection of a dual-core current transformer, the dual-core current transformer has an energy supply coil for extracting electrical energy from a busbar and a measurement coil for measuring the busbar current; at the output end of the energy supply coil Connect a voltage signal processing circuit and configure it to: when the bus current is greater than or equal to I, the voltage signal processing circuit outputs an indication signal S; continuously monitor the signal output of the voltage signal processing circuit and the bus current obtained by the measuring coil Measure the value Irms, and detect and judge the disconnection fault of the two-core current transformer according to the following judgment criteria: If the indication signal S is monitored while Irms<Iset1, and no Irms≥Iset1 occurs within the preset delay time T If the measurement coil of the two-core current transformer has a disconnection fault; if the indication signal S is not monitored while Irms>Iset2, and no Irms≤Iset2 occurs within the preset delay time T, then It is determined that the power supply coil of the two-core current transformer has a disconnection fault; wherein, the preset delay time T≥0, and the preset current thresholds I, Iset1, and Iset2 satisfy 0<Iset1<I<Iset2.

Preferably, the value range of the preset delay time T is between one busbar current cycle and 10s.

Preferably, Iset1=K1*I, Iset2=K2*I; the value range of K1 is [0.5, 0.95], and the value range of K2 is [1.05, 1.2].

Preferably, the value range of I is 0.1In～0.5In, Iset2<In, and In is the rated working current of the bus bar.

Preferably, the voltage signal processing circuit includes resistors R1 to R3 and a triode V1, one end of the resistor R2 is connected to the output end of the power supply coil, and the other end of the resistor R2 is connected to one end of the resistor R3 and the base of the triode V1, The other end of the resistor R3 is connected to the emitter of the transistor V1 and then grounded, one end of the resistor R1 is connected to the working power supply, the other end of the resistor R1 is connected to the collector of the transistor V1 and the connection point of the two is used as the indication of the voltage signal processing circuit signal output.

Based on the same inventive concept, the following technical solutions can also be obtained.

A dual-core current transformer disconnection detection device, the dual-core current transformer has an energy supply coil for extracting electric energy from a busbar and a measurement coil for measuring the busbar current; the device includes.

A voltage signal processing circuit, which is connected to the output end of the power supply coil and is configured to: when the busbar current is greater than or equal to I, the voltage signal processing circuit outputs an indication signal S.

The disconnection judgment module is used to continuously monitor the signal output of the voltage signal processing circuit and the measured value Irms of the busbar current obtained by the measuring coil, and detect and judge the disconnection fault of the two-core current transformer according to the following judgment criteria: such as monitoring When the indication signal S arrives at the same time Irms<Iset1, and the situation of Irms≥Iset1 does not occur within the preset delay time T, it is determined that the measurement coil of the two-core current transformer has a disconnection fault; if the indication signal is not monitored At the same time when S is Irms>Iset2, and the situation that Irms≤Iset2 does not occur within the preset delay time T, it is determined that the power supply coil of the two-core current transformer has a disconnection fault; wherein, the preset delay time T ≥0, the preset current thresholds I, Iset1, and Iset2 satisfy 0<Iset1<I<Iset2.

Preferably, the value of I ranges from 0.1In to 0.5In, Iset2<In, and In is the rated working current of the bus bar.

A circuit breaker comprising a two-core current transformer having an energy supply coil for extracting electrical energy from a busbar and a measurement coil for measuring the busbar current; the circuit breaker also includes any of the above technologies The two-core current transformer disconnection detection device described in the scheme.

Further, the circuit breaker further includes an indication circuit for indicating the detection result of the two-core current transformer disconnection detection device.

beneficial effect

Compared with the prior art, the technical solution of the present invention has the following beneficial effects.

1. Through the technical solution of the present invention, it is possible to accurately identify the disconnection fault of the power supply coil and the measurement coil of the two-core current transformer.

2. Through the technical solution of the present invention, real-time disconnection monitoring can be performed during the operation of the circuit breaker, and the current measurement and protection of the original circuit breaker will not be affected.

3. The implementation circuit of the technical solution of the present invention is simple, no additional hardware is required, and the implementation cost is low.

Description of drawings

FIG. 1 is a schematic structural principle diagram of a specific embodiment of a two-core current transformer disconnection detection device according to the present invention.

FIG. 2 is a structural block diagram of an application example of the present invention in a three-phase four-wire system.

BEST MODE FOR CARRYING OUT THE INVENTION

In view of the deficiencies of the prior art, the solution of the present invention is to connect a voltage signal processing circuit at the output end of the power supply coil of the two-core current transformer and make special settings for it, and then according to the signal output of the voltage signal processing circuit and the measurement The measured value of the busbar current obtained by the coil is used for real-time online detection of the disconnection fault of the power supply coil and the measurement coil of the two-core current transformer.

Embodiments of the present invention

Specifically, the method for detecting disconnection of a two-core current transformer of the present invention is as follows.

The two-core current transformer has an energy supply coil for extracting electrical energy from the busbar and a measurement coil for measuring the busbar current; a voltage signal processing circuit is connected to the output end of the energy supply coil, and is configured as : When the busbar current is greater than or equal to 1, the voltage signal processing circuit outputs the indication signal S; continuously monitors the signal output of the voltage signal processing circuit and the busbar current measurement value Irms obtained by the measuring coil, and according to the following judgment criteria for the dual-core The disconnection fault of the current transformer is detected and judged: if the indication signal S is monitored and Irms<Iset1, and the situation of Irms≥Iset1 does not occur within the preset delay time T, it is judged that the two-core current transformer is faulty. The measurement coil has a disconnection fault; if the indication signal S is not monitored and Irms>Iset2, and the situation of Irms≤Iset2 does not occur within the preset delay time T, it is determined that the power supply coil of the two-core current transformer A disconnection fault occurs; wherein, the preset delay time T≥0, and the preset current thresholds I, Iset1, and Iset2 satisfy 0<Iset1<I<Iset2.

In order to facilitate the public's understanding, the technical solutions of the present invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings.

As shown in FIG. 1 , the dual-core current transformer in this embodiment is used in a circuit breaker, which includes an energy supply coil L1 and a measurement coil L2 respectively arranged on the busbar. The power supply circuit composed of circuit, limiting circuit and DC/DC circuit. The output end of the measuring coil L2 is connected to the current signal processing circuit composed of the integrating circuit and the amplifying circuit. The power supply circuit is used to extract the power supply coil L1 from the bus bar. The electric energy of the circuit breaker is converted into the power supply required by each electric component in the circuit breaker. The current signal processing circuit is used to process the bus current signal collected by the measuring coil L2 and provide it to the control circuit including the microcontroller to calculate the bus current measurement. Value Irms.

As shown in FIG. 1 , a voltage signal processing circuit is connected to the output end of the power supply coil L1, and the voltage signal processing circuit is configured to: when the busbar current is greater than or equal to I, the voltage signal processing circuit outputs an indication signal S; The preferred value range of the preset threshold I is 0.1In～0.5In, where In is the rated working current of the busbar or the circuit breaker; in this embodiment, the value of I is the minimum starting current of the circuit breaker, that is, the energy supply coil can be turned to the power supply. The minimum current that powers the circuit and makes the circuit breaker work properly.

As shown in FIG. 1 , the voltage signal processing circuit in this embodiment includes resistors R1 to R3 and a triode V1. One end of the resistor R2 is connected to the output end of the power supply coil, and the other end of the resistor R2 is connected to one end of the resistor R3 and the triode. The base of V1 is connected, the other end of the resistor R3 is connected to the emitter of the transistor V1 and then grounded, one end of the resistor R1 is connected to the working power supply VCC, the other end of the resistor R1 is connected to the collector of the transistor V1 and the connection point of the two is used as the The indicator signal output end of the voltage signal processing circuit. The bus current threshold I corresponding to the output indication signal S of the voltage signal processing circuit can be adjusted by the resistance values of the resistors R1 ˜ R3 .

The control circuit continuously monitors the signal output of the voltage signal processing circuit and the bus current measurement value Irms obtained by the measuring coil, and detects and judges the disconnection fault of the two-core current transformer according to the following judgment criteria.

If it is monitored that the voltage signal processing circuit outputs the indication signal S, and at the same time Irms<Iset1, and Irms≥Iset1 does not occur within the preset delay time T, it is determined that the measurement coil of the two-core current transformer has a disconnection fault ; otherwise, continue monitoring.

If the indication signal S output by the voltage signal processing circuit is not monitored, and at the same time Irms>Iset2, and no Irms≤Iset2 occurs within the preset delay time T, it is determined that the power supply coil of the two-core current transformer is broken. line failure; otherwise, continue monitoring.

Among them, the preset current thresholds I, Iset1, and Iset2 satisfy 0<Iset1< I<Iset2<In, In is the rated working current of the bus.

The preset delay time T can be 0, that is, the disconnection determination is performed directly without delay; it can also be a preset non-zero value; its optimal value range is one bus current cycle to 10s between.

Preferably, Iset1=K1*I, Iset2=K2*I; the value range of K1 is [0.5, 0.95], the value range of K2 is [1.05, 1.2], and the values of K1 and K2 can make the actual current A certain difference threshold is allowed with the detection current.

Fig. 2 shows a specific application example of the circuit breaker of the present invention in a three-phase four-wire system. The circuit breaker includes four two-core current transformers respectively arranged on the A, B, C, and N lines, and adopts the above-mentioned The two-core current transformer disconnection detection method according to the present invention conducts disconnection detection for each of A, B, C, and N, respectively, to judge whether the power supply coil and the measuring coil in the corresponding two-core current transformer have disconnection faults. The microcontroller circuit controls the magnetic flux converter to perform the tripping action through the trip circuit according to the bus current information and disconnection detection information detected by the two-core current transformer, thereby realizing circuit protection. As shown in Figure 2, the circuit breaker also includes an indication circuit and a parameter setting circuit; the indication circuit includes a display module and a light-emitting diode, which are used for the operation status of the circuit breaker and the detection results of the two-core current transformer disconnection detection device. Indication; the setting circuit is used for the numerical setting of the above parameters K1 and K2.

Claims

A method for detecting disconnection of a dual-core current transformer, the dual-core current transformer has an energy supply coil for extracting electrical energy from a busbar and a measurement coil for measuring the busbar current; characterized in that, in the energy supply The output end of the coil is connected to a voltage signal processing circuit, and it is configured as follows: when the bus current is greater than or equal to I, the voltage signal processing circuit outputs the indication signal S; continuously monitors the signal output of the voltage signal processing circuit and the measurement coil. The measured value Irms of the busbar current is obtained, and the disconnection fault of the two-core current transformer is detected and judged according to the following judgment criteria: if the indication signal S is monitored while Irms<Iset1, and it does not appear within the preset delay time T If Irms≥Iset1, it is determined that the measurement coil of the two-core current transformer has a disconnection fault; if the indication signal S is not monitored while Irms>Iset2, and Irms≤Iset2 does not appear within the preset delay time T In the case of , it is determined that the power supply coil of the two-core current transformer has a disconnection fault; wherein, the preset delay time T ≥ 0, and the preset current thresholds I, Iset1, and Iset2 satisfy 0<Iset1< I<Iset2.
The method for detecting disconnection of a two-core current transformer according to claim 1, wherein the value range of the preset delay time T is between one busbar current cycle and 10s.
The method for detecting disconnection of a dual-core current transformer according to claim 1, wherein Iset1=K1*I, Iset2=K2*I; the value range of K1 is [0.5, 0.95], and the value range of K2 is [1.05, 1.2].
The method for detecting disconnection of a two-core current transformer according to claim 1, wherein the value range of I is 0.1In～0.5In, Iset2<In, and In is the rated working current of the busbar.
The method for detecting disconnection of a two-core current transformer according to claim 1, wherein the voltage signal processing circuit comprises resistors R1-R3 and a transistor V1, one end of the resistor R2 is connected to the output end of the power supply coil, and the resistor R2 is connected to the output end of the power supply coil. The other end of R2 is connected to one end of the resistor R3 and the base of the transistor V1, the other end of the resistor R3 is connected to the emitter of the transistor V1 and then grounded, one end of the resistor R1 is connected to the working power supply, and the other end of the resistor R1 is connected to the collector of the transistor V1 The electrodes are connected and the connection point of the two is used as the indication signal output end of the voltage signal processing circuit.
A dual-core current transformer disconnection detection device, the dual-core current transformer has an energy supply coil for extracting electrical energy from a busbar and a measurement coil for measuring the busbar current; it is characterized in that, the device includes:

a voltage signal processing circuit, which is connected to the output end of the power supply coil and is configured to: when the busbar current is greater than or equal to 1, the voltage signal processing circuit outputs an indication signal S;

The disconnection judgment module is used to continuously monitor the signal output of the voltage signal processing circuit and the measured value Irms of the busbar current obtained by the measuring coil, and detect and judge the disconnection fault of the two-core current transformer according to the following judgment criteria: such as monitoring When the indication signal S arrives at the same time Irms<Iset1, and the situation of Irms≥Iset1 does not occur within the preset delay time T, it is determined that the measurement coil of the two-core current transformer has a disconnection fault; if the indication signal is not monitored At the same time when S is Irms>Iset2, and the situation that Irms≤Iset2 does not occur within the preset delay time T, it is determined that the power supply coil of the two-core current transformer has a disconnection fault; wherein, the preset delay time T ≥0, the preset current thresholds I, Iset1, and Iset2 satisfy 0<Iset1< I<Iset2.
6. The disconnection detection device for a dual-core current transformer according to claim 6, wherein the preset delay time T ranges from one bus current cycle to 10 s.
The two-core current transformer disconnection detection device according to claim 6, wherein Iset1=K1*I, Iset2=K2*I; the value range of K1 is [0.5, 0.95], and the value range of K2 is [1.05, 1.2].
The disconnection detection device for a two-core current transformer according to claim 6, wherein the value range of I is 0.1In～0.5In, Iset2<In, and In is the rated working current of the busbar.
The disconnection detection device for a two-core current transformer according to claim 6, wherein the voltage signal processing circuit comprises resistors R1-R3 and a transistor V1, one end of the resistor R2 is connected to the output end of the power supply coil, and the resistor R2 is connected to the output end of the power supply coil. The other end of R2 is connected to one end of the resistor R3 and the base of the transistor V1, the other end of the resistor R3 is connected to the emitter of the transistor V1 and then grounded, one end of the resistor R1 is connected to the working power supply, and the other end of the resistor R1 is connected to the collector of the transistor V1 The electrodes are connected and the connection point of the two is used as the indication signal output end of the voltage signal processing circuit.
A circuit breaker includes a dual-core current transformer, the dual-core current transformer has an energy supply coil for extracting electrical energy from a busbar and a measurement coil for measuring the busbar current; characterized in that the circuit breaker further includes The disconnection detection device for a two-core current transformer according to any one of claims 6 to 10.
The circuit breaker according to claim 11, further comprising an indication circuit for instructing the detection result of the two-core current transformer disconnection detection device.