CN215646147U - Leakage current relay protection circuit - Google Patents

Abstract

The utility model relates to the technical field of leakage current protection, in particular to a leakage current relay protection circuit which comprises a leakage current detection circuit, a rectification circuit, a voltage comparison circuit and a relay control circuit, wherein the leakage current detection circuit is used for converting leakage current into a voltage signal, the rectification circuit is used for rectifying the voltage signal and outputting detection voltage, the voltage comparison circuit compares the detection voltage with preset voltage and outputs a comparison result to the relay control circuit and a controller, and the relay control circuit controls a relay to act according to the comparison result and a control signal sent by the controller. The leakage current relay protection circuit provided by the utility model can meet the action time limit requirement of the relay when the leakage current is any value, and can timely disconnect the charging circuit, thereby ensuring the personal safety and the equipment safety.

Description

Leakage current relay protection circuit

Technical Field

The utility model relates to the technical field of leakage current protection, in particular to a leakage current relay protection circuit.

Background

When electric automobile power supply equipment charges to on-vehicle charging device, if the leakage current appears, can threaten the personal and equipment safety, need the relay in time to act disconnection charging circuit. The national standard stipulates that the relay needs to act when the leakage current is larger than 30mA, and figure 1 shows the relation between the action time limit of the relay and the magnitude of the leakage current, wherein the action time limit of the relay is smaller when the leakage current is larger, and the relay needs to act and open immediately when the instantaneous value of the leakage current is larger than 300 mA. The leakage current protection scheme in the prior art cannot completely meet the action time limit requirement of the relay.

SUMMERY OF THE UTILITY MODEL

The utility model provides a leakage current relay protection circuit, aiming at solving the technical problem that a leakage current protection scheme in the prior art cannot completely meet the action time limit requirement of a relay, and the leakage current relay protection circuit can meet the action time limit requirement of the relay when the leakage current is of any value and can timely disconnect a charging circuit.

The technical scheme adopted by the utility model is as follows:

a leakage current relay protection circuit comprising:

a leakage current detection circuit for converting leakage current into a voltage signal;

the rectifying circuit is used for rectifying the voltage signal and outputting a detection voltage;

the voltage comparison circuit compares the detection voltage with a preset voltage and outputs a comparison result to the relay control circuit and the controller;

and the relay control circuit controls the action of the relay according to the comparison result and a control signal sent by the controller.

Further, the leakage current detection circuit includes a current transformer connection circuit, the current transformer connection circuit includes a zero sequence current transformer T1 and a resistor R1, the primary side of the zero sequence current transformer T1 detects the leakage current, the secondary side of the zero sequence current transformer T1 is connected to the resistor R1, one end of the resistor R1 is grounded, and the other end of the resistor R1 outputs the voltage signal.

Furthermore, the leakage current detection circuit further comprises a proportional amplification circuit, the input end of the current transformer connecting circuit detects the leakage current, the output end of the current transformer connecting circuit is connected with the input end of the proportional amplification circuit, and the output end of the proportional amplification circuit outputs the voltage signal.

Furthermore, the proportional amplifying circuit comprises an operational amplifier U1, the other end of the resistor R1 is connected with the non-inverting input end of the operational amplifier U1 through a resistor R4, the inverting input end of the operational amplifier U1 is grounded through a resistor R2, a resistor R3 is connected between the inverting input end and the output end of the operational amplifier U1, and the output end of the operational amplifier U1 outputs the voltage signal.

Further, the rectifying circuit comprises an operational amplifier U2, an operational amplifier U3 and a peripheral circuit, wherein the operational amplifier U2 and the operational amplifier U3 form a precise full-wave rectifying circuit by combining the peripheral circuit, rectify the voltage signal and output a detection voltage.

Further, the voltage comparison circuit comprises a voltage comparator U4, the detection voltage is input to a non-inverting input terminal of the voltage comparator U4, the preset voltage is input to an inverting input terminal of the voltage comparator U4, and the comparison result is output to the relay control circuit by an output terminal of the voltage comparator U4.

Further, the relay control circuit includes a first switch element and a second switch element, a first pin and a third pin of the first switch element are connected in series in a relay main loop, a second pin of the first switch element inputs the control signal, a second pin of the first switch element is connected with a first pin of the second switch element, a third pin of the second switch element is grounded, and a second pin of the second switch element inputs the comparison result.

Furthermore, the leakage current relay protection circuit further comprises a voltage conditioning circuit, the input end of the voltage conditioning circuit is connected with the output end of the leakage current detection circuit, the output end of the voltage conditioning circuit is connected with the controller to perform RMS calculation, and the controller outputs a control signal to the relay control circuit according to a calculation result to control the relay to act.

Further, the voltage conditioning circuit comprises a voltage conversion circuit and a voltage follower circuit, the voltage conversion circuit is used for converting the voltage signal into unipolar voltage, the voltage follower circuit is used for signal isolation, the input end of the voltage follower circuit is connected with the output end of the voltage conversion circuit, and the output end of the voltage follower circuit is connected with the controller.

Further, the voltage conversion circuit includes resistance R16 and resistance R17, the first end of resistance R16 with the output of leakage current detection circuit is connected, the second end of resistance R16 with the first end of resistance R17 is connected, the second end of resistance R17 is connected with power VCC, the second end of resistance R16 with the input of voltage follower circuit is connected.

Compared with the prior art, the technical scheme of the utility model has the following beneficial effects:

(1) the leakage current detection circuit and the rectification circuit output detection voltages with different sizes corresponding to leakage currents with different sizes, when the detection voltages are smaller than a preset voltage, the voltage comparison circuit outputs a low level, and the relay control circuit controls the relay to keep connected and not act; when the detection voltage exceeds the preset voltage, the voltage comparison circuit outputs a high level, the relay control circuit controls the relay to act immediately, and the charging circuit is disconnected;

(2) the leakage current relay protection circuit also comprises a voltage conditioning circuit, wherein a voltage signal is input at the input end of the voltage conditioning circuit, the output end of the voltage conditioning circuit is connected with the controller to calculate the RMS, the controller controls the relay to act according to the calculation result, and the relay normally works when the leakage current is less than 30 mA; when the leakage current is large, the relay control circuit controls the relay to act according to the comparison result of the voltage comparator and the control signal of the controller, and the charging circuit is immediately disconnected; when the leakage current is in the middle value, the controller calculates through RMS, and then outputs a control signal to control the action of the relay according to the calculation result, so that the requirement of action time limit can be met under the condition of any leakage current, the circuit is switched off in time, the relay acts accurately, and misoperation is not easy to occur.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

FIG. 1 is a graph showing the relationship between the operating time limit of a relay and the magnitude of leakage current;

FIG. 2 is a schematic diagram of a leakage current relay protection circuit of the present invention;

fig. 3 is a circuit configuration diagram of a current transformer connection circuit of the present invention;

FIG. 4 is a circuit configuration diagram of the scale-up circuit of the present invention;

FIG. 5 is a circuit configuration diagram of a rectifier circuit of the present invention;

FIG. 6 is a waveform diagram of the detection voltage of the present invention;

FIG. 7 is a circuit diagram of the voltage comparison circuit of the present invention;

FIG. 8 is a waveform diagram of the comparison result of the present invention;

FIG. 9 is a circuit configuration diagram of the relay control circuit of the present invention;

FIG. 10 is a circuit diagram of the voltage conditioning circuit of the present invention.

Detailed Description

The utility model aims to provide a leakage current relay protection circuit, which can switch off a relay when the effective value of leakage current exceeds 30mA, can switch off the relay immediately when the leakage current is large, and can meet the requirement of the action time limit of the relay under the condition of any leakage current. Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

The first embodiment is as follows:

as shown in fig. 2, the leakage current relay protection circuit of this embodiment includes a leakage current detection circuit, a rectification circuit, a voltage comparison circuit, and a relay control circuit, wherein the leakage current detection circuit is configured to detect a magnitude of a leakage current and convert the leakage current into a voltage signal, the rectification circuit is configured to rectify the voltage signal and output a detection voltage, the voltage comparison circuit compares the detection voltage with a preset voltage and outputs a comparison result to the relay control circuit, and the relay control circuit controls an operation of the relay according to the comparison result.

Thus, the leakage current detection circuit and the rectification circuit of the embodiment output detection voltages with different magnitudes corresponding to leakage currents with different magnitudes, when the detection voltage is smaller than a preset voltage, the voltage comparison circuit outputs a low level, and the relay control circuit controls the relay to keep connected and not to act; when the detected voltage exceeds the preset voltage, the voltage comparison circuit outputs high level, the relay control circuit controls the relay to act immediately, and the charging circuit is disconnected.

Therefore, only one preset current is selected according to the action time limit requirement of the relay, the preset current corresponds to one preset voltage, the preset voltage is set to be the detection voltage when the leakage current is equal to the preset current, the relay can act immediately when the leakage current exceeds the preset current, and if the preset current is selected to be 30mA, the detection voltage is greater than the preset voltage when the leakage current is greater than 30mA, the relay acts at the moment. This embodiment can make when the leakage current is arbitrary value all can satisfy the relay action time limit requirement through setting up the value of this default voltage, in time breaks off the charging circuit.

Further, the leakage current detection circuit of this embodiment includes current transformer connecting circuit and proportional amplification circuit, and current transformer connecting circuit's input detects the leakage current, and proportional amplification circuit's input is connected to current transformer connecting circuit's output, and proportional amplification circuit's output and the linear proportional relation's of leakage current voltage signal of leakage current. Specifically, as shown in fig. 3-4, the current transformer connection circuit includes a zero sequence current transformer T1 and a resistor R1, the primary side of the zero sequence current transformer T1 detects leakage current, the zero sequence current transformer T1 is optionally but not limited to a feedthrough current transformer, a wire as a leakage current carrier may pass through the middle of the zero sequence current transformer T1, so that the wire forms a primary side coil of the zero sequence current transformer T1, the secondary side of the zero sequence current transformer T1 is connected with the resistor R1, one end of the resistor R1 is grounded, the other end of the resistor R1 outputs a secondary side voltage V1, the other end of the resistor R1 is connected with the input end of the proportional amplifying circuit, and the output end of the proportional amplifying circuit outputs the voltage signal V2. Further, as shown in fig. 4, the proportional amplifier circuit of the present embodiment includes an operational amplifier U1, the other end of the resistor R1 is connected to the non-inverting input terminal of the operational amplifier U1 through a resistor R4, the inverting input terminal of the operational amplifier U1 is grounded through a resistor R2, a resistor R3 is connected between the inverting input terminal and the output terminal of the operational amplifier U1, and the output terminal of the operational amplifier U1 outputs a voltage signal V2.

Referring to fig. 3 and 4, assuming that the secondary side current of the zero-sequence current transformer is I, V1 is R1 × I, and the amplification ratio of the proportional amplifying circuit is I

Then

Further, since the leakage current is an ac signal, the voltage signal V2 output by the leakage current detection circuit is also an ac signal, and the present embodiment converts the voltage signal V2 into a detection voltage with unidirectional ripple through the rectifier circuit, specifically, as shown in fig. 5, the rectifier circuit of the present embodiment includes an operational amplifier U2, an operational amplifier U3 and a peripheral circuit, the operational amplifier U2 and the operational amplifier U3 form a precise full-wave rectifier circuit in combination with the peripheral circuit, rectify the voltage signal V2 and output the detection voltage V3 with a period of 10ms as shown in fig. 6, and the detection voltage V3 is used for comparison with a preset voltage.

Further, as shown in fig. 7 to 8, the voltage comparison circuit of the present embodiment compares the detected voltage V3 with a preset voltage and outputs a comparison result to the relay control circuit, and specifically, the voltage comparison circuit of the present embodiment includes a voltage comparator U4, a non-inverting input terminal of the voltage comparator U4 inputs the detected voltage V3, an inverting input terminal of the voltage comparator U4 inputs the preset voltage V4, and an output terminal of the voltage comparator U4 outputs the comparison result V5 shown in fig. 8 to the relay control circuit. Further, the output terminal of the voltage comparator U4 is also provided with a pull-up resistor R11, because the comparator is open-collector output, and a high level is output through the pull-up resistor R11.

Further, as shown in fig. 9, the relay control circuit of the present embodiment includes a first switching element and a second switching element, a first pin and a third pin of the first switching element are connected in series in the relay main circuit, a second pin of the first switching element is connected to a first pin of the second switching element, a third pin of the second switching element is grounded, and the second pin of the second switching element inputs the comparison result. Specifically, the first switch element is a triode Q1, the second switch element is a triode Q2, the first pins of the triode Q1 and the second switch element are collectors, the second pins are bases, and the third pins are emitters. The collector of triode Q1 is connected with one end of relay K1, and the other end of relay K1 is connected with power VCC, and the projecting pole ground of triode Q1, the base of triode Q1 is connected with switch S2A through resistance R12. Further, the base of the transistor Q1 is connected to the collector of the transistor Q2 via a resistor R15, the emitter of the transistor Q2 is grounded, the base of the transistor Q2 is connected to the first end of the resistor R13, the second end of the resistor R13 is connected to the switch S1A, and the second end of the resistor R13 is grounded via a resistor R14.

It should be noted that, here, S2A represents the control signal output by the controller, and in the initial state, the controller outputs the initial control signal at a high level, which corresponds to the switch S2A being closed and turned on; S1A represents the comparison result output by the voltage comparison circuit, and corresponds to the switch S1A being turned on when the comparison result is high, and corresponds to the switch S1A being turned off when the comparison result is low. In an actual circuit, the port of the controller outputting the control signal may be connected to the point M at the front end of the resistor R12, and the output end of the voltage comparison circuit may be connected to the point N at the front end of the resistor R13.

In the initial state, the controller outputs an initial control signal at a high level (corresponding to the switch S2A being closed) according to the charging requirement, and the transistor Q1 is turned on. When the leakage current is smaller than the preset current, the detection voltage is smaller than the preset voltage, the comparison result V5 is a low level (equivalent to the switch S1A is turned on), at the moment, the triode Q2 is turned off, the triode Q1 is kept on, the working contact of the relay K1 is attracted, the main circuit of the relay is turned on, the charging circuit works, and at the moment, the main circuit is in a normal working state; when the leakage current is larger than the preset current, the comparison result V5 is a square wave with a certain duty ratio, when the comparison result V5 is at a high level (which is equivalent to the switch S1A being closed), the triode Q2 is switched on, the base voltage of the triode Q1 is pulled down, the triode Q1 is switched off, the working contact of the relay K1 is immediately disconnected, the work is stopped, and the charging circuit is disconnected. Further, the comparison result of the embodiment is simultaneously outputted to the controller, the controller outputs the control signal to control the relay to operate according to the comparison result, specifically, when the controller detects that the comparison result is high level or rises from low level to high level, the output control signal is always low level (which is equivalent to that the switch S2A is always off), at this time, even if the comparison result is changed from high level to low level, the relay K1 is not turned on again, and the relay K1 can be prevented from being frequently turned on and off by the comparison result processing of the controller to the voltage comparison circuit.

Since the controller needs a certain time, about several hundred microseconds, to process the comparison result, the present embodiment sets the transistor Q2 and outputs the comparison result to the base of the transistor Q2, so that the relay K1 can be turned off immediately, and the turn-off is more rapid and timely.

Preferably, the preset current is set to be 30mA, when the leakage current is less than 30mA, the relay main loop is turned on, when the leakage current is greater than 30mA, the relay main loop is immediately turned off, and at this time, the action time of the relay is only about 15ms, as can be seen from fig. 1, when the leakage current is greater than 300mA, the action time limit of the relay is 20ms, so that the requirement of the action time limit of the relay at any leakage current can be met. It should be noted that, the 30mA is generally an effective value, the corresponding preset voltage should also be an effective value, and the detection voltage in the embodiment is an instantaneous value, so that the preset voltage needs to be set to a peak value corresponding to the effective value, such as a sine wave, which can be set to the effective value

And (4) doubling.

In conclusion, the leakage current relay protection circuit of the embodiment can meet the requirement of action time limit of the relay when the leakage current is any value, and can timely disconnect the charging circuit, thereby ensuring personal and equipment safety.

Example two:

as shown in fig. 10, the leakage current relay protection circuit of this embodiment is different from the first embodiment in that the leakage current relay protection circuit of this embodiment further includes a voltage conditioning circuit, the input end of the voltage conditioning circuit inputs the voltage signal V2, the output end of the voltage conditioning circuit is used as an AD input to be connected to a controller for RMS calculation, and the controller outputs a control signal according to the RMS calculation result to control the relay to operate, that is, output to the point M in fig. 9. Furthermore, the voltage conditioning circuit comprises a voltage conversion circuit, a voltage follower circuit, a filter circuit and a clamping circuit, wherein the input end of the voltage follower circuit is connected with the output end of the voltage conversion circuit, the output end of the voltage follower circuit is connected with the controller through the filter circuit and the clamping circuit, and the controller outputs a control signal according to the RMS calculation result to control the relay to act.

Specifically, the voltage conversion circuit comprises a resistor R16 and a resistor R17, a first end of the resistor R16 is connected with an output end of the proportional amplifying circuit, a second end of the resistor R16 is connected with a first end of the resistor R17, a second end of the resistor R17 is connected with a power supply VCC, and a second end of the resistor R16 is connected with an input end of the voltage follower circuit. The voltage follower circuit comprises a voltage follower U5, the output end of the voltage follower U5 is connected with a filter circuit, the filter circuit is composed of a resistor R18 and a capacitor C2, the first end of the resistor R18 is connected with the output end of the voltage follower U5, the second end of the resistor R18 is grounded through the capacitor C2, and the second end of the resistor R18 is connected with a clamping circuit. The clamp circuit includes a diode D3 and a diode D4, the cathode of the diode D3 is connected to the power supply VCC, the anode of the diode D3 is connected to the cathode of the diode D4, the anode of the diode D4 is connected to ground, and the cathode of the diode D4 is connected as an AD input to the controller.

The voltage conversion circuit is used for converting the voltage signal V2 into a unipolar voltage V2' of 0-3.3V. The voltage following circuit has the characteristics of high input impedance and low output impedance, so that the voltage following circuit presents a high-impedance state for a previous-stage circuit and presents a low-impedance state for a next-stage circuit, the previous-stage circuit and the next-stage circuit are isolated, the mutual influence between the previous-stage circuit and the next-stage circuit is eliminated, impedance matching is performed conveniently, and the sampling error is reduced. The filter circuit is used for filtering, the clamping circuit is used for ensuring that the voltage of the AD input is kept at 0-3.3V and preventing the voltage of the AD input from exceeding the limit, the AD input voltage is input into the controller for RMS calculation, and when the calculated effective value is more than 30mA, the controller outputs a control signal with low level, namely, the switch S2A in the graph 9 is disconnected, and the relay K1 is disconnected.

After the voltage conditioning circuit is arranged, the preset current can be set to be other values such as 200mA, so that when the leakage current is 0-30mA, the detection voltage is smaller than the preset voltage, the comparison result is low level, the leakage current obtained by RMS calculation is smaller than 30mA, the controller outputs a control signal of high level, and at the moment, the K1 working contact is closed and works normally; when the leakage current is 30-200mA, the detection voltage is smaller than the preset voltage, the comparison result is low level, but the controller calculates the RMS to obtain that the effective value of the leakage current exceeds 30mA, the output control signal is low level, the working contact of the relay K1 is disconnected, the disconnection time is about 35ms which is the sum of the time 20ms calculated by the RMS and the time 15ms of the self action of the relay, and as can be seen from FIG. 1, when the leakage current is smaller than 200mA, the action time limit requirement of the relay is smaller than 38ms, and the requirement can be met at the moment, so the preset current is preferably 200 mA; when the leakage current is larger than 200mA, the detection voltage is larger than the preset voltage, the comparison result is high level, the working contact of the relay K1 is immediately disconnected, the disconnection time is the action time of the relay per se and is only 15ms, and when the leakage current is larger than 300mA, the action time limit of the relay is 20ms, and the action time limit requirement can be met. Therefore, the leakage current relay protection circuit of the embodiment can also meet the action time limit requirement of the relay when any leakage current is large or small, and the effective value is calculated by adopting the controller within 30-200mA, so that the action of the relay is more accurate.

If the preset current is set to be 30mA directly, although the action time limit requirement of the relay can be met, because the preset current of 30mA is an effective value, when the preset voltage is set, the alternating current with the effective value of 30mA needs to be converted, the alternating current is converted into a peak value corresponding to the effective value, the waveform of the general leakage current is interfered by other modules in the circuit and has certain fluctuation, therefore, the converted preset voltage has certain deviation with the actual state, if the preset voltage is set to be lower, the malfunction is easy to occur, and if the preset voltage is set to be higher, the action requirement when the specified leakage current is 30mA cannot be met. In the embodiment, when the leakage current exceeds 30mA, an accurate effective value can be obtained through RMS calculation, so that the relay acts accurately. Although a certain error exists in the converted preset voltage value when the preset current is set to be 200mA, the preset voltage can be set to be lower, false operation is avoided, and meanwhile the requirement of the action time limit can be met.

If the scheme of calculating the effective value by using only the RMS and turning off the relay when it is greater than 30mA is adopted, the operation time limit requirement of the relay cannot be completely met because one cycle is required to sample the AD input voltage in order to obtain an accurate effective value, that is, one cycle is required to sample the AD input voltage, that is, the RMS and the relay are turned off when the AD input voltage is greater than 30mA

Because the relay has the contract15ms of operation time, so it takes around 35ms to completely disconnect. When the leakage current is small, the action time limit is long, and the action time of the relay can meet the requirement of the action time limit, but when the leakage current is large, such as when the leakage current reaches 300mA, the action time limit of the relay is less than 20ms, obviously, the action time of the relay is too long, the relay cannot be timely disconnected, the requirement of a protection circuit cannot be met, and potential safety hazards exist.

Therefore, the leakage current relay protection circuit of the embodiment adopts a scheme of controlling the relay to operate according to the calculation result of the RMS of the controller when the leakage current is 30-200mA, and adopts a scheme of controlling the relay to operate according to the comparison result of the voltage comparator when the leakage current is more than 200mA, so that the requirement of the relay on operation time limit when the leakage current is any magnitude can be met, the relay operates accurately, and the misoperation is not easy to occur. Of course, the interval value 200mA here may be set to other values according to actual conditions, such as setting according to the relay with different self-action time or setting according to different relay action time limit requirement graphs, so as to meet the action time limit requirement.

Example three:

as shown in fig. 3, the model of the zero-sequence current transformer in the leakage current detection circuit of this embodiment is HCT2018-LF, the transformation ratio is 1000/1, i.e., 1A/1mA, the secondary-side voltage is V1 ═ R1 × I, and if R1 ═ 200 Ω, V1 ═ 200 × I.

As shown in fig. 4, if R3 is 900 Ω, R2 is 100 Ω, and the balance resistor R4 is R2// R3 is 90 Ω, the amplification factor of the proportional amplifier circuit is 1+ R3/R2 is 10, and the voltage signal V2 is 10 × V1.

As shown in fig. 10, in the voltage conversion circuit, when both the resistor R16 and the resistor R17 take 1k Ω, V2' is 0.5V2+ 1.65. The translated voltage signal V2' is isolated by a voltage follower circuit, and the AD input voltage is enabled not to exceed 3.3V by a clamping circuit after passing through an RC filter circuit. The AD input voltage is input into the controller to be subjected to RMS calculation, the RMS calculation is root mean square calculation, and the calculation result is actually an effective value and is the square root of the average value of the squares of a group of data. The RMS calculation is divided into three parts, the first part being a multiplier to which the input voltage Ub is fedThe voltage Ua ═ Ub is obtained by line square calculation²(ii) a The second part is an integrator which averages the calculated voltages Ua to obtain a voltage

The third part is a square-open circuit, which squares the voltage Uc to obtain the effective value

Here, Ua, Ub and Uc are illustrated. When the effective value of the leakage current is larger than 30mA, the controller outputs a control signal to control the triode Q1 to be turned off, the relay K1 stops attracting, and the charging circuit is disconnected.

As shown in fig. 1, when the leakage current is 200mA, the action time limit of the relay is about 38ms, the time for completely opening the relay is about 35ms, and the requirement is satisfied, that is, when the leakage current is less than 200mA, the action time of the relay is 35ms, the action time limit requirement of 38ms is satisfied, and when the leakage current is more than 200mA, the action time of the relay is 15ms, and the action time limit requirement of 20ms is satisfied. Therefore, in this embodiment, it is preferable that 200mA is used as the preset current, and when the leakage current is greater than 200mA, the relay directly operates to immediately disconnect the charging line.

Further, when the preset current is 200mA, the secondary-side voltage V1 output by the zero-sequence current transformer T1 is 200 × I, 200 × 0.2/1000, and 0.04V, and a proportional amplifier circuit is used to obtain a voltage signal V2, 10 × V1, and 0.4V, and a detection voltage V3, 0.4V, where the detection voltage is an effective value and a corresponding peak value is greater than 0.4V, the preset voltage is theoretically set to be the same as the peak value, in this embodiment, the preset voltage is preferably set to be low, and if the preset voltage V4 is set to be 0.4V directly, it is equivalent to that when the leakage current is 200mA or less, the relay operates to disconnect the line, and the time limit requirement can be completely met.

In other embodiments, other types of zero sequence current transformers may be selected, for example, a zero sequence current transformer with a transformation ratio of 100/1, the output voltage is 0.4V, the output voltage may be directly used as a voltage signal, and a proportional amplifying circuit may be omitted.

In the present invention, unless otherwise expressly stated or limited, the terms "connected" and "connected" are to be construed broadly, e.g., as meaning either a fixed connection or a removable connection, or an integral part; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the utility model. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The above examples are only for describing the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention, and various modifications and improvements made to the technical solution of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims (7)

1. A leakage current relay protection circuit, comprising:

a leakage current detection circuit for converting leakage current into a voltage signal;

the rectifying circuit is used for rectifying the voltage signal and outputting a detection voltage;

the voltage comparison circuit compares the detection voltage with a preset voltage and outputs a comparison result to the relay control circuit and the controller;

and the relay control circuit controls the action of the relay according to the comparison result and a control signal sent by the controller.

2. The leakage current relay protection circuit according to claim 1, wherein the leakage current detection circuit comprises a current transformer connection circuit, the current transformer connection circuit comprises a zero sequence current transformer T1 and a resistor R1, the primary side of the zero sequence current transformer T1 detects the leakage current, the secondary side of the zero sequence current transformer T1 is connected with the resistor R1, one end of the resistor R1 is grounded, and the other end of the resistor R1 outputs the voltage signal.

3. The leakage current relay protection circuit according to claim 2, wherein the leakage current detection circuit further comprises a proportional amplifier circuit, an input terminal of the current transformer connection circuit detects the leakage current, an output terminal of the current transformer connection circuit is connected to an input terminal of the proportional amplifier circuit, and an output terminal of the proportional amplifier circuit outputs the voltage signal.

4. The leakage current relay protection circuit according to claim 3, wherein the proportional amplifying circuit comprises an operational amplifier U1, the other end of the resistor R1 is connected to the non-inverting input terminal of the operational amplifier U1 through a resistor R4, the inverting input terminal of the operational amplifier U1 is grounded through a resistor R2, a resistor R3 is connected between the inverting input terminal and the output terminal of the operational amplifier U1, and the output terminal of the operational amplifier U1 outputs the voltage signal.

5. The leakage current relay protection circuit according to claim 1, wherein the rectifying circuit comprises an operational amplifier U2, an operational amplifier U3 and peripheral circuits, and the operational amplifier U2 and the operational amplifier U3 form a precision full-wave rectifying circuit in combination with the peripheral circuits, rectify the voltage signal and output the detection voltage.

6. The leakage current relay protection circuit of claim 1, wherein the voltage comparator circuit comprises a voltage comparator U4, a non-inverting input terminal of the voltage comparator U4 inputs the detection voltage, an inverting input terminal of the voltage comparator U4 inputs the preset voltage, and an output terminal of the voltage comparator U4 outputs a comparison result to the relay control circuit and the controller.

7. The leakage current relay protection circuit according to claim 1, wherein the relay control circuit includes a first switching element and a second switching element, a first pin and a third pin of the first switching element are connected in series in a main relay loop, a second pin of the first switching element inputs the control signal, a second pin of the first switching element is connected to a first pin of the second switching element, a third pin of the second switching element is grounded, and a second pin of the second switching element inputs the comparison result.

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