CN102761098B - Device and method for residual current protection - Google Patents
Device and method for residual current protection Download PDFInfo
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- CN102761098B CN102761098B CN201110108596.3A CN201110108596A CN102761098B CN 102761098 B CN102761098 B CN 102761098B CN 201110108596 A CN201110108596 A CN 201110108596A CN 102761098 B CN102761098 B CN 102761098B
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Abstract
The invention provides a device and a method for residual current protection. The device comprises a leakage detector, a trip device and a control circuit, wherein the control circuit is used for generating a driving signal to enable the trip device to execute tripping action when leakage current is detected by the leakage detector. The device further comprises an outside input circuit which is used for responding to outside input to generate a trigger signal, the control circuit responds to the trigger signal and sends the driving signal out, a power source of the outside input circuit and a power source obtaining electricity from a power supply circuit are electrically isolated, and signals of the outside input circuit and the control circuit are electrically isolated. By means of double isolation of power sources and signals, the outside input circuit can be partly or completely isolated from the power supply circuit. Consequently, high voltage is not applied on an outside input button even if elements short out due to faults, so that safety of operators is guaranteed.
Description
Technical Field
The present disclosure relates to a residual current protection device, and particularly to a residual current protection device with an external trigger function.
Background
In low voltage networks, leakage currents occur when an operator touches live parts of an electrical device, which leakage currents are prone to cause personal electrocution accidents. Or, when the electrical device in the low-voltage power grid is poorly insulated, leakage current also exists between the live wire and the zero line, and the leakage current easily causes a short circuit of the line, thereby causing a fire. When the two situations occur, the power supply needs to be cut off to ensure safety.
In a low-voltage power grid, equipment with a leakage protection function is installed, which is an effective protection measure for preventing personal electric shock casualties, electrical fires and electrical equipment damage. Such devices are generally referred to as Residual Current Devices (RCDs). The RCD detects whether there is leakage current in the low voltage grid. Once the RCD detects the presence of a leakage current on the power supply line, it causes a trip mechanism in the RCD to perform a trip action, which in turn causes a circuit breaker on the power supply line to break the line.
In practical applications, the RCD needs to provide an external trigger function in addition to the conventional leakage protection described above. That is, the RCD provides an external input that an operator may use to manually trigger the RCD to trip, if necessary, regardless of whether a leakage condition has occurred, and thereby manually disconnect the power supply line. For example, in the event of an electrical device failure, such as an accident, to avoid further danger, the operator may manually trigger the RCD to disconnect the power supply line immediately without any electrical leakage having occurred. In addition, the external trigger function can help a user to remotely test whether the tripping mechanism and the circuit breaker can work normally.
Such an external trigger function of the RCD is generally implemented using a simple circuit. Fig. 1 shows a simplest example by way of example. As shown in FIG. 1, the external input circuit 140 includes a resistor R0 and an external toggle button B1 connected in series between the power supply and ground. The voltage across resistor R0 is monitored by a control circuit MCU1 in the RCD, the rest of which is not shown. Here, button B1 acts as a switching element that turns off with a low voltage across resistor R0. When button B1 is pressed, the switch closes, causing the series branch in which it is located to conduct, whereby the voltage across the resistor is high, i.e. an effective external trigger signal is formed. At this time, the RCD causes the trip mechanism therein to perform a trip action in response to the active external trigger signal.
In the design shown in fig. 1, the external input circuit is powered directly from the power supply line. One potential hazard with such a design is: if the element supplying power to the external input circuit malfunctions, for example, is broken down, a large current on the power supply line will be directly applied to the trigger button B1. If the user touches such a charged button, a shock event may occur.
Therefore, the existing RCD with external triggering function cannot meet the safety requirement, so that a new type of RCD with external triggering function is needed to avoid unnecessary personal electric shock injury.
Disclosure of Invention
The invention aims to provide a residual current protection device with an external trigger function. The residual current protection device can be safely and forcibly triggered from the outside without considering whether leakage current occurs or not, and does not cause any electric shock injury to protection operators.
To achieve the above object, the present invention provides a residual current protection device, comprising: a leakage detector for detecting leakage current on the power supply line; the control circuit is used for sending out a driving signal when the leakage current detector detects leakage current; a trip device which responds to the driving signal to execute a trip action; the external input circuit is used for responding to an external input to generate a trigger signal, wherein the control circuit responds to the trigger signal to send out the driving signal, a power supply of the external input circuit is electrically isolated from a power supply which is used for taking power from a power supply line, and signals of the external input circuit and the control circuit are also electrically isolated. The double isolation of the power supply and the signal can effectively prevent the large current on the power supply line from being directly applied to the trigger button of the external input circuit, thereby ensuring the safety of operators.
In a preferred embodiment, the electrical isolation between the power sources may be achieved using an isolation transformer, an isolated AC-DC conversion module, an isolated DC-DC conversion module, or a combination of isolated AC-DC and DC-DC conversion modules. The electrical isolation between the signals may be achieved using isolation transformers, relays, optocouplers, or magnetic couplings.
In another preferred embodiment, the power supply of the external input circuit is derived from and electrically isolated from the power supply of the control circuit. Therefore, the power supply of the external input circuit can be obtained from the low-voltage power supply of the control circuit, so that the independent design of a filtering, voltage-dividing and voltage-stabilizing circuit for the external circuit is omitted, and only the isolated DC-DC conversion is needed. This approach is therefore particularly suitable for low cost demanding equipment.
In a further preferred embodiment, the power supply of the external input circuit supplies power only when an enable signal issued by the control circuit is active. That is, when the enable signal is not active, the power supply of the external input circuit is also inactive, which can further prevent the occurrence of electric shock to the user.
In addition, according to another aspect of the invention, the invention also provides a residual current protection method with external input control. The method comprises the following steps: detecting leakage current on a power supply line; when detecting the leakage current, sending a driving signal to drive a tripping device to execute a tripping action; generating a trigger signal in response to an external input; and issuing the drive signal in response to the trigger signal regardless of whether a leakage current is detected, wherein the power source for generating the trigger signal is electrically isolated from a power source that draws power from a power supply line, and the trigger signal is delivered to the circuit for generating the drive signal in an electrically isolated manner.
Drawings
The drawings are only for purposes of illustrating and explaining the present invention and are not to be construed as limiting the scope of the present invention. Wherein,
FIG. 1 shows a schematic diagram of a simple external trigger capable RCD of existing;
FIG. 2 shows a schematic diagram of a more complex prior art RCD with external triggering;
FIG. 3 schematically illustrates a schematic diagram of an RCD with external trigger functionality according to one embodiment of the present invention;
FIG. 4 schematically illustrates a schematic diagram of an RCD with external trigger functionality according to another embodiment of the present invention;
fig. 5 exemplarily shows a schematic diagram of an RCD having an external trigger function according to still another embodiment of the present invention.
Detailed Description
In order to more clearly understand the technical features, objects, and effects of the present invention, embodiments of the present invention will now be described with reference to the accompanying drawings.
Fig. 2 shows a schematic diagram of an existing RCD with an external trigger function. As shown in fig. 2, the RCD 200 includes a leakage detector 210 (e.g., a zero sequence current transformer zct (zero order current transformer), a control circuit 220 (e.g., a microcontroller MCU, or a control chip such as that produced by mitsubishi, etc.), a trip device 230 including a trip coil 231 and a thyristor 235, and an external input circuit 240.
In fig. 2, leakage detector 210 detects the presence of leakage current in the line between live line L and neutral line N. The leakage detector 210 sends the detected leakage current signal to the control circuit 220 (pins 1 and 2) for determination. If the control circuit 220 determines that the leakage occurs, pin 7 of the control circuit 220 outputs a driving signal to the thyristor 235. The thyristor 235 is turned on in response to the driving signal, thereby causing the trip coil 231 to perform a trip action by suddenly getting a large current.
In the RCD 200 shown in fig. 2, the external input circuit 240 provides an external trigger signal Vt to the control circuit 220, so that the control circuit sends out a driving signal for driving the trip coil from the pin 7 regardless of whether a leakage phenomenon occurs. Specifically, as shown in fig. 2, the power supply portion 241 of the external input circuit 240 is supplied by the rectified and filtered line voltage V. The power supply section 241 includes a MOS field effect transistor M1, a zener diode D5, and a large resistor R1 (e.g., 1000K Ω) in series. When M1 is turned on, a stable voltage Va is obtained at the cathode of zener diode D5 (point a). The voltage Va is used as a power source applied to the input portion 243 of the external input circuit 240. As shown in fig. 2, the input section 243 is a series branch comprising two resistors R2 and R3 and an external trigger button 245. The voltage Vt across resistor R3 is monitored by pin 6 of control circuit 220. When the external trigger button 245 is off, Vt is low. Conversely, when the external trigger button 245 is pressed, the input portion 243 is turned on and the voltage Vt across R3 is high. Control circuit 220, upon detecting that Vt is high, immediately sends a drive signal from pin 7 to cause the thyristor to turn on and the trip coil to trip.
In the external input circuit 240 shown in fig. 2, an external input enable circuit is also preferably designed. Pin 5 of control circuit 220 is connected to the gate of M1 as shown. Thus, M1 is turned on only when pin 5 of control circuit 220 outputs a valid enable signal, i.e., a high level, and external input circuit 240 is powered up, otherwise the external input is disabled.
As can be seen from fig. 2, the power supply portion of the external input circuit 240 draws power directly from the power supply line L. In this case, if M1 fails, such as being broken down, M1 is equivalent to being shorted (as shown by line L1 in fig. 2). At this time, a high voltage (large current) on the power supply line is directly applied to the input portion 243 (as shown by a line L2 in fig. 1), so that it is easy to cause injury or death of a person who touches the trigger button 245 due to electric shock.
In order to avoid the danger of the circuit shown in fig. 2, the present invention proposes a new type of RCD with an external triggering function. Fig. 3 schematically shows a RCD 300 according to the present invention. The RCD 300 shown in fig. 3 is identical to fig. 2 except for the external input circuit 340, and thus the same elements and circuits are not described again for the sake of brevity. However, it should be understood by those skilled in the art that the other parts of the RCD proposed by the present invention except the external input circuit 340 may have other structures than those shown in fig. 2, for example, the trip device 130 may use other mechanisms such as a relay or a transistor to drive the trip coil.
Unlike fig. 2, the power supply portion 341 of the external input circuit 340 in fig. 3 no longer draws power directly from the power supply line, but instead draws power in an electrically isolated manner from some power source in the RCD (e.g., the power source that draws power from the power supply line). At the same time, input section 343 is also connected to control circuit 220 in signal isolation 344. By this dual isolation of power and signals, the external input circuit 340 may be completely isolated from the power supply line section. Thus, even if the elements in the RCD shown in fig. 3 are short-circuited due to a failure, a high voltage is not applied to the external input button 245, thereby ensuring safety of an operator.
The isolation of the power supply and the isolation of the signal shown in fig. 3 can be achieved in a number of ways. For example, the power isolation may be implemented by using an isolation transformer, or may be implemented by using an isolated AC-DC conversion module, a DC-DC conversion module, or a combination of AC-DC and DC-DC conversion modules. Similarly, signal isolation may also be implemented by using an isolation transformer, a relay, an optical coupler, or a magnetic coupler. Fig. 4 and 5 show examples of two specific external input circuits, respectively.
Fig. 4 shows an example of an RCD 400 with external triggering functionality according to one embodiment of the invention. In fig. 4, the external input circuit 440 of the RCD 400 includes a power supply portion 441, an input portion 443, and an optical coupler 444 as a signal isolation device. The power supply part 441 is an isolation transformer T1, the primary of which is connected to the rectified supply line voltage, and the secondary of which is further rectified to provide a stable low voltage, e.g. 5V, to the input part 443. The primary and secondary in the isolation transformer T1 are electrically isolated, in other words, electrically isolated. Thus, the current from the power supply line on the primary side of T1 does not flow to the external input circuit portion. Further, the optical coupler 444 is employed in the external input circuit shown in fig. 4 to achieve signal isolation between the input portion 443 and the control circuit 220. If the trigger button 245 is closed, the branch of the input part is turned on, and the electro-optical diode in the optocoupler 444 is energized to emit light, i.e. to convert the electrical signal into an optical signal. The optical signal activates the phototransistor in the optocoupler to switch on, thereby pulling the level of the monitoring pin 6 of the control circuit 220 from high to low. The control circuit 220 detects the active low trigger signal and then generates a driving signal to enable the trip device to perform a trip operation. The control circuit 220 is electrically isolated from the external input circuit 440 by optical coupling. Thus, even if a large current occurs in the other parts of the RCD due to a component failure, the large current does not flow to the button 245 through the signal path, thereby preventing the operator from receiving an electric shock.
Fig. 5 shows an example of an RCD 500 with external triggering functionality according to another embodiment of the invention. In fig. 5, the power supply portion 541 of the external input circuit 540 obtains power from the direct-current power supply Vcc (5V) of the control circuit 220 through an isolated DC-DC converter. The dc power supply Vcc may be a rectified low voltage power supply that is originally used to power the control circuitry. Here, the isolated DC-DC converter may be, for example, an addm 600 type converter provided by ADI corporation, or other similar isolated DC-DC converter. In addition, in fig. 5, a relay 544 is used as a signal isolation device between the input section 543 and the control circuit 220. If the trigger button 245 is closed, as shown in fig. 5, the branch of the input section is conductive and the relay 544 is electrically activated, causing switch K1 to conduct. Thus, the control circuit 220 sends a driving signal to trigger the trip device to perform the trip operation because the pin 6 of the control circuit obtains a high level.
Preferably, in the example shown in fig. 5, the control circuit 220 may also provide an external input enable signal, similar to fig. 2. This signal may be sent from pin 5 of control circuit 220 as shown in fig. 2. When the enable signal is active (e.g., high), the power supply of the external input circuit is powered. Conversely, if the enable signal is not asserted, the RCD cannot be triggered even if the user presses the external trigger button.
It will be appreciated by those skilled in the art that the power isolation means and signal isolation means of fig. 4 and 5 may also have a variety of other configurations. For example, the power supply part of the external input circuit can also be realized by an isolated AC-DC converter, or by AC-DC and DC-DC conversion. As will be apparent to those skilled in the art. Similarly, the signal isolation device may also employ a conversion device such as a magnetic coupling to achieve electrical isolation. In addition, although the input portions of the external input circuits shown in fig. 4 and 5 are substantially the same, it will be understood by those skilled in the art that the input portions may also be implemented by using other circuit structures known in the art, such as a branch circuit including a parallel resistor as the input portion, and so on.
As described above, with the RCD as shown in fig. 3 to 5, since the external input circuit is isolated from the other circuits of the RCD by using the dual isolation of power isolation and signal isolation, even if a component failure occurs in the RCD, a high voltage or a large current is not applied to the external trigger button, thereby ensuring that an operator is protected from electric shock.
It should be understood that although the present description has been described in terms of various embodiments, not every embodiment includes only a single embodiment, and such description is for clarity purposes only, and those skilled in the art will recognize that the embodiments described herein may be combined as suitable to form other embodiments, as will be appreciated by those skilled in the art.
The above description is only an exemplary embodiment of the present invention, and is not intended to limit the scope of the present invention. Any equivalent alterations, modifications and combinations can be made by those skilled in the art without departing from the spirit and principles of the invention.
Claims (6)
1. A residual current protection device (300) comprising:
a leakage detector (210) for detecting leakage current on the power supply line;
a control circuit (220) for generating a driving signal when the leakage current detector (210) detects a leakage current;
a trip device (230) responsive to the drive signal from the control circuit (220) to perform a trip action;
an external input circuit (340, 440, 540) for generating a trigger signal in response to an external input;
wherein the control circuit (220) further issues the driving signal in response to the trigger signal from the external input circuit, and
the power supply of the external input circuit (340, 440, 540) is electrically isolated from the power supply which is powered from the power supply line, and the signals of the external input circuit (340, 440, 540) and the control circuit (220) are also electrically isolated.
2. A residual current protection device as claimed in claim 1, wherein electrical isolation between the power sources is achieved using a combination of isolated AC-DC and DC-DC conversion modules, an isolation transformer, an isolated AC-DC conversion module, or an isolated DC-DC conversion module.
3. The residual current protection device of claim 2, wherein the power supply of the external input circuit (540) is derived from and electrically isolated from the power supply of the control circuit (220).
4. A residual current protection device as claimed in any one of claims 1 to 3, wherein electrical isolation between said signals is achieved using an isolation transformer, relay, optocoupler, or magnetic coupling.
5. The residual current protection device of claim 4, wherein the external input circuit (440) further comprises an opto-coupler, and the trigger signal is communicated to the control circuit (220) via the opto-coupler.
6. A residual current protection device as claimed in claim 5, wherein the power supply of said external input circuit (540) supplies power only when an enable signal issued by said control circuit is active.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201110108596.3A CN102761098B (en) | 2011-04-28 | 2011-04-28 | Device and method for residual current protection |
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| CN201110108596.3A CN102761098B (en) | 2011-04-28 | 2011-04-28 | Device and method for residual current protection |
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| CN102761098B true CN102761098B (en) | 2015-04-01 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103852676A (en) * | 2012-11-30 | 2014-06-11 | 西门子公司 | Passive contact detection device and method |
| DE102014201501A1 (en) * | 2014-01-28 | 2015-07-30 | Siemens Aktiengesellschaft | External control of an electromagnetic release |
| CN109644117B (en) | 2018-06-22 | 2020-08-11 | Oppo广东移动通信有限公司 | Method, apparatus and storage medium for determining size of demodulation reference signal indication information |
| CN111879987B (en) * | 2020-07-16 | 2023-10-20 | 北京瑞赛长城航空测控技术有限公司 | High-voltage-resistant isolated contact detection circuit |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5510945A (en) * | 1994-01-31 | 1996-04-23 | Siemens Energy & Automation | Power supply for ground fault circuit interrupter |
| CN201003356Y (en) * | 2006-04-29 | 2008-01-09 | 上海松下电工池田有限公司 | Platform door system with charging and discharging function and passive operation system |
| CN201294366Y (en) * | 2008-08-21 | 2009-08-19 | 佛山市顺德区信辉达电子有限公司 | Creepage protector combining with power-supply plug |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB0226111D0 (en) * | 2002-11-08 | 2002-12-18 | Delta Electrical Ltd | Residual current devices |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5510945A (en) * | 1994-01-31 | 1996-04-23 | Siemens Energy & Automation | Power supply for ground fault circuit interrupter |
| CN201003356Y (en) * | 2006-04-29 | 2008-01-09 | 上海松下电工池田有限公司 | Platform door system with charging and discharging function and passive operation system |
| CN201294366Y (en) * | 2008-08-21 | 2009-08-19 | 佛山市顺德区信辉达电子有限公司 | Creepage protector combining with power-supply plug |
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