Device and method for detecting residual current of three-phase four-wire common neutral dual power supply

Abstract

The present application provides a detection device for residual current of a three-phase four-wire common zero line dual power supply, comprising: a dual power supply switching switch, a first residual current transformer, a second residual current transformer, a first current detection unit, a second current detection unit, and a residual current main control unit for sampling data and obtaining the residual current of the three-phase four-wire common zero line dual power supply according to the sampled data analysis. The three-phase four-wire common zero line dual power supply residual current detection device provided by the present application can accurately measure its residual current, and effectively avoid the inaccurate residual current or malfunction caused by the zero line current of the power cable disconnected from the load being not zero in the shared zero line dual power supply; the method provided by the present application is applicable to the detection device of the present application, and the accurate residual current of the common zero line dual power supply is obtained by detecting the residual current of the power supply electrically connected to the load and the vector sum of the phase current of the zero-phase cable of the power supply disconnected from the load.

Description

Technical Field

[0001] The present invention relates to the technical field of low-voltage power distribution network, and in particular to a detection device and method for residual current of a three-phase four-wire common-zero dual power supply. Background Art

[0002] Residual current refers to the current whose vector sum of currents of each phase (including neutral line) in the low-voltage distribution line is not zero. In the residual current (formerly called leakage current) protection technology, in the three-phase four-wire power supply system, since the neutral point of the power transformer is directly grounded, when the insulation resistance of the phase line of the power supply system or electrical equipment decreases (or leakage occurs), the leakage current forms a loop through the neutral point of the transformer. In the existing residual current monitoring device, the neutral line at the rear end of the residual current transformer remains independent. If there is a shared neutral line at the rear end of the residual current transformer, the three-phase unbalanced current in the neutral line will cause deviations, resulting in the inability to accurately monitor the residual current. However, three-pole dual-power switching devices are currently widely used in the field of low-voltage power distribution, and there is a shared neutral line during switching.

[0003] Therefore, there is an urgent need for a detection method that can accurately measure the residual current. Summary of the invention

[0004] In view of this, the present invention provides a detection device for residual current of a three-phase four-wire common neutral line dual power supply, characterized in that it includes: a dual power supply switching switch, a first residual current transformer arranged at the main power supply incoming end of the dual power supply switching switch, a second residual current transformer arranged at the backup power supply incoming end of the dual power supply switching switch, a first current detection unit arranged at the main power supply, a second current detection unit arranged at the backup power supply, and a residual current main control unit for receiving sampling data of the dual power supply switching switch, the first residual current transformer, the second residual current transformer, the first current detection unit and the second current detection unit and obtaining the residual current of the three-phase four-wire common neutral line dual power supply according to the sampling data analysis.

[0005] Furthermore, the first current detection unit includes current transformers that pass through the A-phase, B-phase and C-phase cables of the main power supply respectively, and the output ends of the current transformers are electrically connected to the residual current main control unit.

[0006] Furthermore, the second current detection unit includes current transformers that pass through the A-phase, B-phase and C-phase cables of the backup power supply respectively, and the output ends of the current transformers are electrically connected to the residual current main control unit.

[0007] Furthermore, the residual current main control unit includes an STM32F407 chip.

[0008] Accordingly, the present application also provides a method for detecting residual current of a three-phase four-wire common neutral dual power supply, characterized in that: the method is applicable to any detection device described in claims 1-4, and the method comprises the following steps:

[0009] S1: The residual current main control unit obtains the real-time status of the dual power switch, and determines whether the main power supply is electrically connected to the load or the backup power supply is electrically connected to the load according to the real-time status;

[0010] S2: According to the real-time status of the dual power switch, collect data of the residual current transformer of the power cable electrically connected to the load and input the data into the residual current main control unit Is;

[0011] At the same time, the A-phase current IA, the B-phase current IB and the C-phase current IC of the power cable disconnected from the load are collected by the current collection unit, and the current values ​​IA, IB and IC are transmitted to the residual current main control unit;

[0012] S3: The residual current main control unit analyzes the data of steps S1 and S2, and outputs the residual current of the three-phase four-wire dual power supply with a common neutral line.

[0013] Further, step S3 includes:

[0014] S31: vector adding the A-phase current IA, the B-phase current IB and the C-phase current IC of the power cable disconnected from the load to obtain the zero-phase current of the power supply disconnected from the load;

[0015] S32: vectorially add the current of the residual current transformer and the zero-phase current of the power supply disconnected from the load, wherein the vectorial sum is the residual current of the three-phase four-wire common-neutral dual power supply.

[0016] The beneficial technical effects of the present invention are as follows: the three-phase four-wire common neutral line dual power supply residual current detection device provided by the present application can accurately measure its residual current, and effectively avoid the inaccurate residual current or malfunction caused by the zero line current of the power cable disconnected from the load being not zero in the common neutral line dual power supply; the method provided by the present application is applicable to the detection device of the present application, and the accurate residual current of the common neutral line dual power supply is obtained by detecting the vector sum of the residual current of the power supply electrically connected to the load and the phase current of the zero-phase cable of the power supply disconnected from the load. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0018] Figure 1 This is a schematic diagram of the structure of the detection device of the present application. DETAILED DESCRIPTION

[0019] The present invention is further described below with reference to the accompanying drawings:

[0020] The present invention provides a detection device for residual current of a three-phase four-wire common-zero dual power supply, characterized in that it comprises: a dual power supply switching switch, a first residual current transformer arranged at the main power supply incoming line end of the dual power supply switching switch, a second residual current transformer arranged at the backup power supply incoming line end of the dual power supply switching switch, a first current detection unit arranged at the main power supply, a second current detection unit arranged at the backup power supply, and a residual current main control unit for receiving sampling data of the dual power supply switching switch, the first residual current transformer, the second residual current transformer, the first current detection unit and the second current detection unit and obtaining the residual current of the three-phase four-wire common-zero dual power supply according to the analysis of the sampling data. In this embodiment, the lower residual current transformer and the second residual current transformer are arranged at the incoming end of the dual power switch in order to accurately detect the residual current of the power cable electrically connected to the load, that is, there is no need to detect the residual current of the power cable disconnected from the load, the phase current of the power cable is detected by the first current detection unit and the second current detection unit, and the real-time state of the dual power switch is obtained by the residual current main control unit to collect the phase current of the power cable disconnected from the load, and the zero-phase current of the power cable disconnected from the load is determined according to the phase current. In a three-phase four-wire power distribution network, if the neutral line is shared, the current on the neutral line is the sum of the zero-line current of the main power supply and the zero-line current of the backup power supply. If it is necessary to obtain the accurate residual current of the power cable electrically connected to the load to avoid electric shock, electrical fire accidents and malfunction of the dual power switch, it is necessary to accurately obtain the residual current of the power cable electrically connected to the load, and it is necessary to subtract the zero-phase current of the power cable disconnected from the load from the residual current.

[0021] In this embodiment, the first current detection unit includes current transformers passing through the A-phase, B-phase and C-phase cables of the main power supply, respectively, and the output ends of the current transformers are electrically connected to the residual current main control unit. The residual current main control unit collects the phase current of the main power cable in real time to provide data support for the subsequent calculation of the zero-phase current of the main power supply.

[0022] In this embodiment, the second current detection unit includes current transformers passing through the A-phase, B-phase and C-phase cables of the backup power supply respectively, and the output ends of the current transformers are electrically connected to the residual current main control unit. The phase current of the backup power supply cable is collected in real time by the residual current main control unit to provide data support for the subsequent calculation of the zero-phase current of the main power supply.

[0023] In this embodiment, the residual current main control unit includes an STM32F407 chip. The STM32F407 chip is internally provided with a 12-bit dual-synchronous AD analog-to-digital converter, and 12 channels of AD signals are synchronously collected, of which 6 channels of AD simultaneously collect analog signals of three-phase currents of the main power supply and the backup power supply, 2 channels collect the values ​​of the first residual current transformer and the second residual current transformer, and 1 channel collects the real-time status of the dual power supply switch, and converts the analog signal into a digital signal for the subsequent main control chip to calculate the residual current.

[0024] Accordingly, the present application also provides a method for detecting residual current of a three-phase four-wire common neutral dual power supply, characterized in that: the method is applicable to any detection device described in claims 1-4, and the method comprises the following steps:

[0025] S1: The residual current main control unit obtains the real-time status of the dual power switch, and determines whether the main power supply is electrically connected to the load or the backup power supply is electrically connected to the load according to the real-time status;

[0026] S2: According to the real-time status of the dual power switch, collect data of the residual current transformer of the power cable electrically connected to the load and input the data into the residual current main control unit Is;

[0027] At the same time, the A-phase current IA, the B-phase current IB and the C-phase current IC of the power cable disconnected from the load are collected by the current collection unit, and the current values ​​IA, IB and IC are transmitted to the residual current main control unit;

[0028] S3: The residual current main control unit analyzes the data of steps S1 and S2, and outputs the residual current of the three-phase four-wire dual power supply with a common neutral line.

[0029] Wherein, step S3 comprises:

[0030] S31: vector adding the A-phase current IA, the B-phase current IB and the C-phase current IC of the power cable disconnected from the load to obtain the zero-phase current of the power supply disconnected from the load;

[0031] S32: vectorially add the current of the residual current transformer and the zero-phase current of the power supply disconnected from the load, wherein the vectorial sum is the residual current of the three-phase four-wire common-neutral dual power supply.

[0032] It is worth mentioning that the specific selection of the residual current transformer involved in the patent application of this invention should be regarded as the prior art. The specific structure, working principle and possible control method and spatial layout method of these technical features can be selected according to the conventional selection in the field, and should not be regarded as the inventive point of the patent of this invention. The patent of this invention will not be further elaborated.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A three-phase four-wire common neutral dual power supply residual current detection device, characterized in that: include: A dual power switch, a first residual current transformer arranged at the main power supply inlet end of the dual power switch, a second residual current transformer arranged at the backup power supply inlet end of the dual power switch, a first current detection unit arranged at the main power supply, a second current detection unit arranged at the backup power supply, and a residual current main control unit for receiving sampling data of the dual power switch, the first residual current transformer, the second residual current transformer, the first current detection unit and the second current detection unit and obtaining the residual current of the three-phase four-wire common zero line dual power supply according to the sampling data analysis; A detection method using the detection device comprises the following steps: S1: The residual current main control unit obtains the real-time status of the dual power switch, and determines whether the main power supply is electrically connected to the load or the backup power supply is electrically connected to the load according to the real-time status; S2: According to the real-time status of the dual power switch, collect data of the residual current transformer of the power cable electrically connected to the load and input the data into the residual current main control unit Is; At the same time, the A-phase current IA, the B-phase current IB and the C-phase current IC of the power cable disconnected from the load are collected by the current detection unit, and the current values ​​IA, IB and IC are transmitted to the residual current main control unit; S3: the residual current main control unit analyzes the data of steps S1 and S2, and outputs the residual current of the three-phase four-wire dual power supply with a common neutral line; Step S3 includes: S31: vector adding the A-phase current IA, the B-phase current IB and the C-phase current IC of the power cable disconnected from the load to obtain the zero-phase current of the power supply disconnected from the load; S32: vectorially add the current of the residual current transformer and the zero-phase current of the power supply disconnected from the load, wherein the vectorial sum is the residual current of the three-phase four-wire common-neutral dual power supply.

2. According to the device for detecting residual current of three-phase four-wire common neutral dual power supply of claim 1, it is characterized in that: The first current detection unit includes current transformers that pass through the A-phase, B-phase and C-phase cables of the main power supply respectively, and the output ends of the current transformers are electrically connected to the residual current main control unit.

3. The detection device for residual current of three-phase four-wire common neutral dual power supply according to claim 1 is characterized in that: The second current detection unit includes current transformers that pass through the A-phase, B-phase and C-phase cables of the backup power supply respectively, and the output ends of the current transformers are electrically connected to the residual current main control unit.

4. The device for detecting residual current of a three-phase four-wire common neutral dual power supply according to claim 1, characterized in that: The residual current main control unit includes an STM32F407 chip.

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