CN110658368A

CN110658368A - Residual current detection device and residual current action protection system

Info

Publication number: CN110658368A
Application number: CN201910905733.2A
Authority: CN
Inventors: 艾精文; 赵宇明; 王静; 陈思磊; 谢智敏
Original assignee: Shenzhen Power Supply Bureau Co Ltd
Current assignee: Shenzhen Power Supply Bureau Co Ltd
Priority date: 2019-09-24
Filing date: 2019-09-24
Publication date: 2020-01-07
Anticipated expiration: 2039-09-24
Also published as: CN110658368B

Abstract

The application relates to a residual current detection device and a residual current action protection system. The residual current detection device comprises a mutual inductor, a pulse generator, a sampling element and a controller. The transformer includes a plurality of taps. The controller controls the pulse generator to send pulse signals with certain frequency and amplitude to the mutual inductor. The mutual inductor induces residual current on the direct current wire to be detected under the action of the pulse signal. And the controller acquires the voltage on the sampling element so as to obtain the real residual current value on the direct current wire to be detected. The controller selects the number of turns of the coil of the mutual inductor by controlling the on-off of the tap, and then the measuring range of the residual current detection device is changed. The residual current detection device can detect the residual current in a wide range by changing the range on the basis of high detection precision.

Description

Residual current detection device and residual current action protection system

Technical Field

The present application relates to the field of electrical devices, and in particular, to a residual current detection device and a residual current operation protection system.

Background

Residual current is a big cause of electrical fire and personal electric shock accidents. The remaining reasons are various, such as insulation aging of electrical equipment due to lack of effective maintenance, irregular distribution installation, overload of distribution lines, reduction of insulation level of wires affected by natural environment under humid conditions, and the like. Meanwhile, the reasons also lead to complex and various residual current forms, and challenge is brought to the design and development of the residual current operated protector.

In the field of civil construction and municipal administration, the range of direct current residual current is wider from several mA to several A due to various reasons for generating the direct current residual current. In the traditional direct current residual current detection method, after the number of turns of a coil and the magnetic core parameters are determined, the detection range is fixed. Although the range can be changed in a small range by changing the external circuit parameters, the detection accuracy is lowered. Particularly, for portable residual current detection equipment, how to ensure the high precision of direct current residual current detection while the detection range is large becomes a problem to be solved urgently.

Disclosure of Invention

Therefore, it is necessary to provide a residual current detection device and a residual current operation protection system for solving the problem of single measurement range of the conventional dc residual current detection method.

A residual current detection device comprising:

the mutual inductor comprises a plurality of coils and a plurality of voltage transformers, wherein the plurality of coils are used for inducing residual current of the direct current lead to be detected, each coil is provided with a tap, and the plurality of taps comprise a first type tap and a second type tap;

the pulse generator comprises a first end, a second end and a third end, wherein the first end is electrically connected with the first tap;

a sampling element electrically connected to the second end; and

the controller comprises a sampling end, a pulse modulation control end and a plurality of first control output ends, wherein the sampling end is electrically connected with the sampling element, the pulse modulation control end is electrically connected with the third end, and each first control output end is electrically connected with one of the second taps.

In one embodiment, the method further comprises the following steps:

a plurality of optical couplers, each of which includes a first input terminal, a second input terminal and an output terminal, the first input terminal is electrically connected to the second tap, the second input terminal is electrically connected to one of the first control output terminals, and the output terminal is electrically connected to the sampling element.

In one embodiment, the number of the plurality of taps is four, four of the taps include one tap of the first type and three taps of the second type, and the number of the plurality of optical couplers is three.

In one embodiment, the controller further comprises a first serial communication terminal, and the residual current detection device further comprises:

and the communication interface circuit is electrically connected with the first serial port communication end.

In one embodiment, the controller further includes a second serial communication port, and the residual current detection device further includes:

and the display device is electrically connected with the second serial port communication end.

In one embodiment, the controller further comprises a second control output, and the residual current detection device further comprises:

and the alarm is electrically connected with the second control output end.

In one embodiment, the method further comprises the following steps:

and the filter is electrically connected with the sampling end.

In one embodiment, the transformer further comprises:

and the coil is wound on the magnetic core.

In one embodiment, the material of the magnetic core and the material of the coil are both flexible materials.

A residual current operated protection system comprising:

the residual current detection device of any one of the above embodiments; and

and the circuit breaker is electrically connected with the residual current detection device.

In one embodiment, the method further comprises the following steps:

and the test circuit is electrically connected with the residual current detection device.

The residual current detection device comprises a mutual inductor, a pulse generator, a sampling element and a controller. The transformer includes a plurality of taps. The pulse generator includes a first terminal, a second terminal, and a third terminal. The first end is electrically connected to one of the taps. The second end is electrically connected with the sampling element. The controller comprises a sampling end, a pulse modulation control end and a plurality of first control output ends. The sampling end is electrically connected with the sampling element. The pulse modulation control end is electrically connected with the third end. Each of the first control outputs is electrically connected to one of the remaining taps. The controller controls the pulse generator to send pulse signals with certain frequency and amplitude to the mutual inductor. And the mutual inductor induces the residual current on the direct current wire to be detected under the action of the pulse signal. And the controller acquires the voltage on the sampling element so as to obtain the real residual current value on the direct current wire to be detected. The controller controls the on-off of the tap, so that the number of turns of the coil of the mutual inductor is selected, and the measuring range of the residual current detection device is changed. The residual current detection device can detect the residual current in a wide range by changing the range on the basis of high detection precision.

Drawings

Fig. 1 is a diagram of a residual current detection device provided in an embodiment of the present application;

FIG. 2 is a block diagram of a transformer provided in one embodiment of the present application;

FIG. 3 is a diagram of a residual current detection device provided in an embodiment of the present application;

FIG. 4 is a graph of core current and residual current provided in an embodiment of the present application;

FIG. 5 is a graph illustrating the relationship between the detected current and the residual current provided in an embodiment of the present application;

fig. 6 is a diagram of a residual current operated protection system provided in an embodiment of the present application.

Description of the main element reference numerals

Residual current detection device 10

Mutual inductor 100

Tap 101

Tap 102 of the first kind

Tap 103 of the second kind

Magnetic core 111

Coil 112

Pulse generator 120

First end 121

Second end 122

Third terminal 123

Sampling element 130

Controller 140

Sampling terminal 141

Pulse modulation control terminal 142

First control output 143

First serial port communication port 144

Second serial port communication terminal 145

Second control output 146

Optical coupler 150

First input terminal 151

Second input terminal 152

Output terminal 153

Communication interface circuit 160

Display device 170

Alarm 180

Filter 190

DC power converter 200

Residual current operated protection system 20

Circuit breaker 210

Test circuit 220

Detailed Description

In order to make the aforementioned objects, features and advantages of the present application more comprehensible, embodiments accompanying the present application are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. This application is capable of embodiments in many different forms than those described herein and those skilled in the art will be able to make similar modifications without departing from the spirit of the application and it is therefore not intended to be limited to the embodiments disclosed below.

It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

With the popularization and application of the direct current system, the direct current residual current becomes an important factor threatening the safe and reliable operation of the direct current system. In the field of civil construction and municipal administration, the range of direct current residual current is wider from several mA to several A due to various reasons for generating the direct current residual current. Particularly, for portable residual current detection equipment, how to ensure the high precision of direct current residual current detection while the detection range is large becomes a problem to be solved urgently. Therefore, referring to fig. 1, an embodiment of the present application provides a residual current detection device 10. The residual current detection device 10 comprises a transformer 100, a pulse generator 120, a sampling element 130 and a controller 140.

The transformer 100 includes a multi-path coil 112 for inducing a residual current of the dc line to be measured. Each coil 112 has a tap 101. The plurality of taps 101 comprises a first type of taps 102 and a second type of taps 103.

Specifically, referring to fig. 2, the transformer 100 may include a core 111 and a plurality of windings 112. The material of the magnetic core 111 is a soft magnetic material. In an alternative embodiment, the material of the magnetic core 111 is permalloy. Initial permeability mu of permalloy₀80000 (GS/Oe). In another alternative embodiment, the material of the magnetic core 111 is an amorphous alloy material. The dc conductor to be tested passes through the magnetic core 111 to form the primary winding of the transformer 100. The magnetic core 111 has good high-frequency characteristics, and when the magnetic core works normally, the magnetic core 111 can reach a magnetic saturation state only by small excitation current at high frequency, so that the power consumption of a power supply can be effectively reduced, and the circuit design is simplified. The multi-path coil 112 is wound on the magnetic core 201 to form a secondary winding of the transformer 100. The number of turns of each winding of the multi-path coil 112 is different. In one embodiment, the material of the magnetic core 111 and the material of the coil 112 are both flexible materials.

The pulse generator 120 includes a first terminal 121, a second terminal 122, and a third terminal 123. The first end 121 is electrically connected to the first type tap 102. The first terminal 121 is an excitation voltage output terminal. The pulse generator 120 provides an excitation voltage to the multiplexer 112 through the first terminal 121. The second terminal 122 is a ground terminal of the pulse generator 120. The third terminal 123 is a command receiving terminal. The sampling element 130 is electrically connected to the second end 122. The sampling element 130 may be a sampling resistor. The resistance value of the sampling resistor may be set to 100 Ω. The sampling voltage is taken across the sampling element 130. The controller 140 includes a sampling terminal 141. A pulse modulation control terminal 142 and a plurality of first control output terminals 143. The sampling terminal 141 is electrically connected to the sampling element 130, and is configured to collect a sampling voltage signal at two ends of the sampling element 130. The pulse modulation control terminal 142 is electrically connected to the third terminal 123, and is configured to send a pulse modulation signal with a certain frequency to the pulse generator 120. When the pulse generator 120 receives the pulse modulation signal, the first terminal 121 outputs a square wave with a corresponding frequency. The amplitude of the square wave may be 12V. The frequency range of the square wave output by the first end 121 is 1kHz to 10 kHz. Each of said first control outputs 143 is electrically connected to one of said second type taps 103. The controller 140 selects the tap to be switched in via the first control output 143. For example, when the output of the first control output terminal 143 is high, and the remaining two first control output terminals 143 are low, the selected tap is tap B, and the number of turns of the coil is N_BAt this time, the range is R_B＝I×N_BAnd I is the current value of the coil when the magnetic core enters a saturation state, and N is the number of turns of the coil. Similarly, when the output of the third first control output terminal 143 is at a high level and the remaining two first control output terminals 143 are at a low level, the selected tap is D, and the number of turns of the coil is N at this time_DAt this time, the range is R_D＝I×N_D. The controller 140 may be a single chip or a microprocessor.

Specifically, the pulse generator 120 may be a half-bridge voltage driver including an NPN transistor and a PNP transistor. The base electrodes of the two triodes are mutually connected. The emitters of the two transistors are connected to each other and output a square-wave pulse driving voltage to the secondary winding of the transformer 100. The collectors of the two triodes are connected with a bipolar power supply. The maximum collector current of the two transistors is related to the number of winding turns of the coil 112, the characteristics of the magnetic core 111, and the resistance of the sampling element 130. The pulse generator 120 cyclically provides voltages in positive and negative directions to the secondary windings of the transformer 100 by turning on different transistors.

As shown in the core current curve of fig. 3, when the pulse voltage is +12V, the core current changes from a negative value to a positive value and gradually increases until the pulse voltage reverses to-12V, and the core current decreases from the positive value to the negative value and then increases in the opposite direction, and in such a cycle, the value of the sampling resistor is set to 100 Ω, so that the core repeats a deep saturated and unsaturated state.

Average value of core currentWherein

For the detected residual current value, K is a constant determined by the magnetic core material and the structure, ip is the real residual current value, N is the number of turns of the coil, and the negative sign indicates that the direction is opposite. As shown in fig. 3, when the residual current on the dc line to be measured is 10mA, the core current is also translated in the opposite direction, so that the average value of the core current is

When N is set to K,

the minus sign indicates that the direction is reversed.

In this embodiment, the controller 140 controls the pulse generator 120 to send a pulse signal with a certain frequency and a certain amplitude to the transformer 100. The mutual inductor 100 induces a residual current on the dc conductor to be measured under the action of the pulse signal. The controller 140 acquires the voltage on the sampling element 130 to obtain the real remaining current value on the dc conductor to be measured. The controller 140 controls the on/off of the tap 103 to select the number of turns of the coil of the transformer 100, so as to change the range of the residual current detection device 10. The residual current detection device 10 can detect a wide range of residual current by changing a range on the basis of high detection precision. The residual current detection device 10 is matched with a direct current circuit breaker for use, and is favorable for safe and reliable operation of a direct current system. The residual current detection device 10 is applied to portable direct current residual current detection equipment and can realize high-precision and multi-range direct current residual current detection.

Referring to fig. 4, in one embodiment, the residual current detection device 10 further includes a plurality of optocouplers 150. Each of the photo-couplers 150 includes a first input terminal 151, a second input terminal 152, an output terminal 153, and a ground terminal. The ground terminal of each of the photo-couplers 150 is connected in series and then connected to the ground terminal of the controller 140. The first input 151 is electrically connected to the second type tap 103. The second input 152 is electrically connected to one of the first control outputs 143. The output 153 is electrically connected to the sampling element 130.

Specifically, the optical coupler 150 is an electrical-to-optical-to-electrical conversion device that transmits electrical signals through the medium of light. The optical coupler 150 is composed of a light emitting source and a light receiving device. The light source and the light receiver are assembled in the same closed shell and are isolated from each other by a transparent insulator. The input of the light emitting source is the second input 152. The input end of the light receiving source is the first input end 151. The output end of the light receiving source is the output end 153. The optocoupler 150 may be used to isolate the sampling element 130 from the effects of the sensing of residual current to be measured by the transformer 100. In addition, the first control output 143 of the controller 140 is controlled to select the on-state optocoupler, thereby selecting the number of turns N connected into the coil, and the range R is changed by changing N. In one embodiment, the number of the plurality of taps 101 is four, four of the taps 101 include one tap 102 of the first type and three taps 103 of the second type, and the number of the plurality of optical couplers 150 is three. In this case, the residual current detection device 10 may have at least three different ranges.

In one embodiment, the controller 140 further comprises a first serial communication port 144, a second serial communication port 145 and a second control output port 146. The residual current detection device 10 further comprises a communication interface circuit 160, a display device 170 and an alarm 180. The communication interface circuit 160 is electrically connected to the first serial port communication port 144. The display device 170 is electrically connected to the second serial port communication terminal 145. The alarm 180 is electrically connected to the second control output 146. The communication interface circuit 160 may be an RS485 driver circuit. At this time, the communication interface circuit 160 supports RS485 communication protocol, and can communicate with an upper computer, so that the expansibility is strong. The display device 170 can display the detected value of the direct current residual current, the polarity and the system running state information in real time. When the residual current detected by the controller 140 exceeds the action threshold, a high level may be output through the second control output end 146 of the controller 140, so that the alarm 180 electrically connected to the second control output end 146 performs a state alarm. Alternatively, when the residual current detected by the controller 140 exceeds the operation threshold, a high level may be output through the second control output end 146 of the controller 140, so that the circuit breaker disconnecting circuit electrically connected to the second control output end 146 performs protection.

In one embodiment, the residual current detection device 10 further comprises a filter 190. The filter 190 is electrically connected to the sampling terminal 141. The filter 190 may be a butterworth digital filter. The voltage signal on the sampling element, which is collected by the sampling terminal 141, may be filtered by the filter 190. The low-pass filter is set as follows:

wherein, the order n of the filter is 5, and the cut-off frequency omega of the filter_c30 Hz. The result of the low-pass filtering is shown in fig. 5, and the detected current is the same as the real dc residual current and has the opposite direction.

Referring to fig. 6, an embodiment of the present application provides a residual current operated protection system 20. The residual current operated protection system 20 comprises a residual current detection device 10 and a circuit breaker 210 as described in any one of the above embodiments. The circuit breaker 210 is electrically connected to the residual current detection device 10. The particular circuit breaker 210 is electrically connected to the second control output 146 of the controller 140. When the residual current detected by the controller 140 exceeds the action threshold, a high level can be output through the second control output end 146 of the controller 140, so that the circuit breaker 210 breaks the loop for protection.

In one embodiment, the residual current operated protection system 20 further comprises a test circuit 220. The test circuit 220 is electrically connected to the residual current detection device 10. The test circuit 220 may be used to simulate the generation of a residual current. When the current generated by the test circuit 220 is detected by the residual current detection device 10, the circuit breaker 210 can be protected by breaking the circuit. When the residual current operated protection system 20 detects whether the circuit breaker 210 can work normally or the circuit breaker 210 is required to break the circuit, the circuit breaker 210 can break the circuit by matching the test circuit 220 with the residual current detection device 10.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the claims. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A residual current detection device, comprising:

the transformer (100) comprises a plurality of coils (112) for sensing residual current of a direct current wire to be tested, each coil (112) is provided with a tap (101), and the plurality of taps (101) comprise a first type tap (102) and a second type tap (103);

a pulse generator (120) comprising a first terminal (121), a second terminal (122) and a third terminal (123), the first terminal (121) being electrically connected to the first type tap (102);

a sampling element (130) electrically connected to the second end (122); and

a controller (140) comprising a sampling terminal (141), a pulse modulation control terminal (142) and a plurality of first control output terminals (143), wherein the sampling terminal (141) is electrically connected with the sampling element (130), the pulse modulation control terminal (142) is electrically connected with the third terminal (123), and each of the first control output terminals (143) is electrically connected with one of the second type taps (103).

2. The residual current detection device according to claim 1, characterized by further comprising:

a plurality of optical couplers (150), each of said optical couplers (150) comprising a first input (151), a second input (152) and an output (153), said first input (151) being electrically connected to said second type tap (103), said second input (152) being electrically connected to one of said first control outputs (143), said output (153) being electrically connected to said sampling element (130).

3. The residual current detection device according to claim 2, wherein the number of the plurality of taps (101) is four, the four taps (101) comprise one tap (102) of the first type and three taps (103) of the second type, and the number of the plurality of optocouplers (150) is three.

4. The residual current detection device according to claim 1, characterized in that said controller (140) further comprises a first serial communication terminal (144), said residual current detection device (10) further comprising:

a communication interface circuit (160) electrically connected to the first serial port communication terminal (144).

5. The residual current detection device according to claim 4, characterized in that said controller (140) further comprises a second serial communication terminal (145), said residual current detection device (10) further comprising:

and the display device (170) is electrically connected with the second serial port communication terminal (145).

6. The residual current detection device according to claim 5, characterized in that said controller (140) further comprises a second control output (146), said residual current detection device (10) further comprising:

and the alarm (180) is electrically connected with the second control output end (146).

7. The residual current detection device according to claim 1, characterized by further comprising:

and the filter (190) is electrically connected with the sampling end (141).

8. The residual current detection device according to claim 1, characterized in that said mutual inductor (100) further comprises:

and the coil (112) is wound on the magnetic core (111).

9. The residual current detection device according to claim 8, characterized in that the material of the magnetic core (111) and the material of the coil (112) are both flexible materials.

10. A residual current operated protection system, comprising:

the residual current detection device (10) of any one of claims 1 to 9; and

a circuit breaker (210) electrically connected to the residual current detection device (10).

11. The residual current operated protection system according to claim 10, further comprising:

and the test circuit (220) is electrically connected with the residual current detection device (10).