JP2017034731A - Ground fault detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly prevent electric shock of a human body even when a ground default accident occurs in an electrically conductive cable or the like for connecting a power source and an electric vehicle in a ground fault detector.SOLUTION: A ground fault detector 6 is connected to an electrically conductive cable 5 for connecting a power supply 4 for charging and discharging electric power while insulated from the ground and an electric vehicle 7, and detects occurrence of a ground fault. The ground fault detector 6 includes: a current sensor 6a; and a ground fault determining unit 6d that sets the current of about half of human body protection current as a threshold value, determines that a ground fault has occurred when detection current detected by the current sensor 6a exceeds the threshold value, and that controls the power supply 4 and/or the electric vehicle 7 to stop power output. This configuration allows the ground fault detector 6 to appropriately prevent an electric shock to the human body even when a ground fault accident occurs in the conductive cable 5 or the like.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a ground fault detector that detects a ground fault from a conductive cable connecting a power source and an electric vehicle.

  In recent years, a charge / discharge system (V2H :) that discharges energy stored in a storage battery mounted on an electric vehicle (EV) or a plug-in hybrid vehicle (PHEV) to supply a load other than the vehicle, for example, an electric product in a house. Vehicle-to-Home) has become widespread. In this charge / discharge system, a storage battery mounted on an electric vehicle plays a role of supplying power.

  Such a conventional charge / discharge system will be described with reference to FIG. The charging / discharging system 100 includes a power source 101 that is insulated from the ground, an electric vehicle 102, and a conductive cable 103 that connects them. The power source 101 is a charging outlet or the like provided in a house, converts AC power into DC power, charges a storage battery of the electric vehicle 102, and converts DC current discharged from the electric vehicle 102 into AC current. To power the load. The electric vehicle 102 is an automobile equipped with a storage battery.

  In the charging / discharging system 100, it is assumed that a maximum current of 20 V flows through the conductive cable 103, and the earth leakage breaker 101a is connected to the power source 101, for example, to ensure electrical safety. The earth leakage breaker 101a compares the forward current flowing through the conductive cable 103 and the return current, and determines that the earth leakage has occurred when the difference exceeds a predetermined threshold, and interrupts the circuit. .

  By the way, regarding the charging / discharging system using an automobile, for example, a ground fault detector capable of quickly detecting a ground fault in an electric vehicle charger is disclosed (see Patent Document 1). Also disclosed is a charging / discharging device for an electric vehicle that detects a ground fault occurring in a cable during power feeding and improves safety when power is supplied from a storage battery mounted on the electric vehicle to a load outside the electric vehicle. (For example, refer to Patent Document 2).

JP 2010-239837 A WO2013 / 051484

  However, when the charge / discharge system such as V2H described above is assumed, there is a problem that a portion where the human body cannot be properly protected is generated depending on the position of the leakage breaker or the relay that interrupts the electric circuit. This is because, in charge / discharge systems such as V2H, a ground fault accident to the human body via a conductive cable is mainly assumed. In this case, a ground fault taking into account the human body resistance and the insulation resistance of the electric vehicle is also considered. This is because it is necessary to detect.

  In addition, it is necessary to appropriately protect the human body even when a ground fault occurs at any of the power supply 101, the electric vehicle 102, and the conductive cable 103 constituting the charge / discharge system 100.

  The present invention has been made in view of the above problems, and even when a ground fault occurs in a conductive cable connecting a power source and an electric vehicle, a ground fault detection that appropriately prevents an electric shock to a human body. The purpose is to provide a vessel.

  In order to achieve the above-mentioned object, the present invention is connected to a conductive cable that connects between a power source that is insulated from the ground and charges and discharges electric power and an electric vehicle, and detects a ground fault. A current detector that detects a ground fault current in the conductive cable and a current that is approximately half of the human body protection current as a threshold, and a detected current detected by the current sensor exceeds the threshold A ground fault determination unit that determines that a ground fault has occurred and controls to stop outputting power to the power source and / or the electric vehicle.

  In the ground fault detector, the threshold is preferably about 10 mA.

  In the ground fault detector, it is preferable that the ground fault determination unit controls so that both the power source and the electric vehicle stop outputting power to the conductive cable substantially simultaneously.

  In the ground fault detector, the power source preferably includes a circuit breaker or a relay for turning on / off the electric circuit on the output terminal side.

  In the ground fault detector, the electric vehicle preferably includes a circuit breaker or a relay for turning on / off the electric circuit on the output terminal side.

  The ground fault detector preferably further includes communication means for transmitting a control signal for turning on / off a circuit breaker or a relay provided in the power source to the power source.

  The ground fault detector preferably further includes communication means for transmitting a control signal for turning on / off a circuit breaker or a relay provided in the electric vehicle to the electric vehicle.

  In this ground fault detector, the current sensor is an annular sensor, and the ground fault detector is further connected in series between the feeder lines of the conductive cable, and a pair of resistance elements having the same resistance value, Preferably, a ground wire connecting a neutral point of a pair of resistance elements and ground is provided, and the ground wire is penetrated through an opening of the annular sensor.

  In this ground fault detector, it is preferable that a test current line for correcting an offset of the current sensor is passed through the opening of the annular sensor.

  In the ground fault detector, it is preferable that the test current line is wound around the annular sensor a plurality of times.

  In this ground fault detector, the output value of the current sensor when a current of a certain polarity is passed through the test current line, and the output value of the current sensor when a current of the opposite polarity having the same magnitude is passed. It is preferable to set the average value of the current zero point.

  In the ground fault detector, the current sensor may be offset-corrected by opening an electric circuit for the power source and the conductive cable of the electric vehicle, and setting the output value of the current sensor at this time as a current zero point. preferable.

  In this ground fault detector, the ground fault detector is preferably provided integrally with the conductive cable.

  In this ground fault detector, the ground fault detector is preferably provided in the power source.

  In addition, the charge / discharge system according to the present invention includes a power source that is insulated from the ground to charge and discharge power, an electric vehicle, a conductive cable that connects the power source and the electric vehicle, and the ground fault. And a detector.

  According to the ground fault detector according to the present invention, it is determined that a ground fault has occurred when the detected current detected by the current sensor exceeds the threshold, with a current approximately half of the human body protection current as a threshold. Control to stop the output of power to the power source and / or the electric vehicle. With this configuration, in the present invention, even when a ground fault occurs in a conductive cable or the like that connects the power source and the electric vehicle, it is possible to appropriately prevent electric shock of the human body.

(A) The whole figure of the charging / discharging system which concerns on embodiment of this invention, (b) It is a functional block diagram of the said charging / discharging system. It is a more detailed functional block diagram of the charging / discharging system. It is an equivalent circuit diagram of the charging / discharging system when a ground fault occurs. It is a reference figure which shows the relationship between the electric current continuation time in IEC specification, and DC leakage current. It is explanatory drawing of the charging / discharging system which concerns on the modification 1 of the said embodiment. (A) Explanatory drawing of the charging / discharging system which concerns on the modification 2 of the said embodiment, (b) Explanatory drawing of the charging / discharging system which concerns on the modification 3 of the said embodiment. (A) Explanatory drawing of the test electric current in the ground fault detector with which the charging / discharging system which concerns on the modification 4 of the said embodiment is equipped, (b) The flowchart which shows the operation | movement procedure at the time of the offset correction of the said ground fault detector. . (A) Explanatory drawing of the charging / discharging system which concerns on the modification 5 of the said embodiment, (b) It is a flowchart which shows the operation | movement procedure at the time of the offset correction of the ground fault detector with which the said charging / discharging system is equipped. (A) Vertical direction sectional drawing of the electroconductive cable used for the charging / discharging system which concerns on the modification 6 of the said embodiment, (b) It is explanatory drawing of the said charging / discharging system. It is explanatory drawing of the charging / discharging system which concerns on the modification 7 of the said embodiment. It is a reference figure which shows an example of the conventional charging / discharging system.

(Embodiment)
A ground fault detector according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the charging / discharging system S includes an AC power source 1, a distribution board 2 for residential use connected to the AC power supply 1, a load 3 such as an electric device, and a power supply 4 connected to the distribution board 2. , Conductive cable 5, ground fault detector 6, and electric vehicle 7. This charging / discharging system S is called V2H, and makes the storage battery of the electric vehicle 7 play a role of adjusting a gap between supply of power and demand.

  The power source 4 is a charging outlet for a house, a charging station for a public facility, etc., is insulated from the ground, and receives a single-phase AC 100V, 200V, etc. from the distribution board 2 via electric wires. As shown in FIG. 2, the power source 4 converts the AC power supplied from the AC power source 1 into DC power and supplies the DC power to the electric vehicle 7 (specifically, a voltage of 100 to 450 V). The converter 4a for converting the direct-current power to be converted into alternating-current power and supplying it to the load 3 is provided.

  As shown in FIG. 2, the power supply 4 includes an electromagnetic relay 4 b (or a circuit breaker) for turning on / off the electric circuit according to a control signal from the ground fault detector 6. The relay 4b is intended for human body protection when a charging / discharging abnormality occurs, and is provided in the power source 4 in advance. With this configuration, when power output should be stopped, such as when a ground fault occurs, the power circuit 4 can be cut off by opening the relay 4b (or circuit breaker) provided on the output terminal 4c side. Therefore, it is not necessary to stop the output mode, and the power output can be stopped at high speed.

  The conductive cable 5 serves as an electrical path between the power source 4 and the electric vehicle 7, and one end is connected to the power source 4 via a power plug and the like, and the other end of the electric vehicle 7 is connected via a charging / discharging connector. . The conductive cable 5 has at least a pair of power supply lines through which a direct current for charging and discharging flows.

  The ground fault detector 6 is connected to the conductive cable 5 that connects the power source 4 and the electric vehicle 7, and detects the occurrence of a ground fault in the electric path between the power source 4 and the electric vehicle 7. As shown in FIG. 2, the ground fault detector 6 according to the present embodiment includes a current sensor 6a, a pair of ground resistors 6b and 6c, and a ground fault determination unit 6d.

  The current sensor 6a sequentially outputs a sensor output value (detection current) of a direct current flowing through the ground line 6f connected to the earth 6e. For example, an annular magnetic core made of a magnetic material and a toroidal to the magnetic core And an excitation coil wound in a shape. The current sensor 6a detects a change in the magnetic field due to a current flowing through the ground line 6f that passes through the opening formed in the magnetic core and converts it into a current value. In addition, by using the current sensor 6a as an annular sensor, it becomes easy to achieve electrical insulation between the ground wire 6f and the current sensor 6a by covering the outer shape of the current sensor 6a with an insulator.

  The pair of resistance elements 6 b and 6 c are resistance elements having the same resistance value (for example, 40 KΩ), and are connected in series between the feeder lines of the conductive cable 5. The neutral point 6g of the resistance elements 6b and 6c is grounded by the ground line 6f. That is, the ground line 6f connects the neutral point 6g and the ground 6e. Note that the resistance elements 6b and 6c are not essential constituent elements, and may be configured by a pair of a plurality of resistance elements having the same combined resistance value.

  The ground fault determination unit 6d sets the current value of approximately half of the human body protection current as a threshold value, and when the sensor output value (detected current) of the current sensor 6c exceeds the threshold value, the ground fault is detected at any point of the conductive cable 5. It is determined that the accident point has occurred. In this case, the ground fault determination unit 6d controls the power supply 4 and / or the electric vehicle 7 to stop outputting power. Specifically, the ground fault determination unit 6d transmits a control signal for stopping output of power from the power source 4 and the electric vehicle 7 to the power source 4 and / or the electric vehicle 7, and turns on at least one of the relays 4b and 7b. Control and disconnect the circuit. In the present embodiment, when the ground resistances 6b and 6c are 40 KΩ and the human body protection current is 25 mA, the threshold is set to about half of the human body protection current or about 10 mA in consideration of variations.

  The ground fault determination unit 6d can stop the output of the power outputs of both the power source 4 and the electric vehicle 7 substantially simultaneously by transmitting a control signal. For this reason, since the power supply can be stopped in any state of charging from the power source 4 side to the electric vehicle 7 side or discharging from the electric vehicle 7 to the power source 4 side, the human body Can reduce the electric shock effect.

  The electric vehicle 7 is an electric vehicle (EV) or a plug-in hybrid vehicle (PHEV) equipped with a storage battery 7a such as a lithium ion battery. As shown in FIG. 2, the electric vehicle 7 includes an electromagnetic relay 7 b (or a circuit breaker) for turning on and off the electric circuit according to a control signal from the ground fault detector 6. The relay 7b is intended to protect a human body when a charging / discharging abnormality occurs, and is provided in the electric vehicle 7 in advance. With this configuration, when power output should be stopped, such as when a ground fault occurs, the electric circuit can be interrupted by opening the relay 7b (or circuit breaker) provided on the output terminal 7c side, and the control unit provided in the electric vehicle 7 Therefore, it is not necessary to stop the output mode, and the power output can be stopped at high speed.

  Next, see FIG. 3 for the flow of the ground fault current when a ground fault from the human body and a ground fault from the electric vehicle 7 are generated in different power supply lines on the positive and negative sides of the conductive cable 5 during charging and discharging. To explain.

  In this figure, the voltage Vd supplied from the power source 4 is 100 to 450V. The grounding resistors 6b and 6c are 40 KΩ each. The human resistance 8 is in the range of 0.5 to 2.5 KΩ. Further, when a voltage from the power source 4 is applied to the electric vehicle 7, a slight current flows through the surface and the insulator. At this time, it is assumed that the insulation resistance 7d of the electric vehicle 7 is 100Ω / V. For example, when the voltage of the power supply 4 is 450V, the insulation resistance 7d of the vehicle is 45KΩ. In addition, in the electric vehicle 7 in which the insulation deterioration has occurred, the insulation resistance 7d decreases and the leakage current increases.

  In the circuit shown in this figure, when the ground fault current flowing to the human body reaches the human body protection current of 25 mA, the current detected by the current sensor 6a of the ground fault detector 6 becomes approximately 10 mA. That is, when the current sensor 6a of the ground fault detector 6 detects a current that is approximately half of the human body protection current (about 25 mA) or about 10 mA, the ground fault determination unit 6d starts control for cutting off the electric circuit.

  Here, the human body protection current necessary for human body protection at the time of ground fault will be described with reference to FIG. The “human body protection current” in the present embodiment is based on the IEC standard, and the DC leakage current on the horizontal axis does not have a physiologically harmful effect regardless of the current duration on the vertical axis in FIG. The current is set to 25 mA (dotted line Y in the figure) that does not exceed the region −2.

  As described above, the ground fault detector 6 uses the current of approximately half the human body protection level (or approximately 10 mA) as a threshold value, and the sensor output value detected by the current sensor 6a exceeds the threshold value, the power supply 4 and the electric vehicle. 7, at least one of the relays 4b and 7b is disconnected. As a result, the current flowing to the human body at the time of occurrence of a ground fault through the conductive cable 5 is kept to 25 mA or less, and a ground fault point occurs at any of the power source 4, the conductive cable 5 and the electric vehicle 7. Can protect the human body properly. In addition, since the human body can be protected by opening at least one of the relays 4b and 7b of the power supply 4 and the electric vehicle 7, the configuration can be simplified and the cost can be reduced.

  In the present embodiment, the ground fault determination unit 6d of the ground fault detector 6 can transmit a control signal to stop the power outputs of both the power supply 4 and the electric vehicle 7 at substantially the same time. In this case, the power supply can be stopped regardless of whether charging is performed from the power source 4 side to the electric vehicle 7 side or discharging from the electric vehicle 7 to the power source 4 side. Can reduce the electric shock effect.

(First modification)
A first modification of the present embodiment will be described with reference to FIG. In the first modification, the ground fault detector 6 includes a communication unit 10 that turns on / off the relay 4b (or the circuit breaker) on the output terminal 4c side of the power supply 4. With this configuration, when the ground fault detector 6 detects a ground fault current of approximately half of the human body protection current or approximately 10 mA or more, the relay 4 b is directly OFF-controlled from the ground fault detector 6. For this reason, the electric circuit can be disconnected independently of the control state of the power supply 4, so that high-speed operation can be realized and safety for the human body is ensured. Although not shown, it is also conceivable that the communication unit 10 is provided between the ground fault detector 6 and the electric vehicle 7 and the relay 7b of the electric vehicle 7 is directly OFF-controlled from the ground fault detector 6. obtain. The communication unit 10 can be realized in various forms such as wired, wireless, and power line communication (PLC).

(Second modification)
A second modification of the present embodiment will be described with reference to FIG. In the second modification, as shown in FIG. 6A, the current sensor 6a is an annular sensor, and the test current line 11 is passed through the opening of the annular sensor. This test current line 11 is a test line for correcting an offset of the current sensor 6 a provided in the ground fault detector 6. With this configuration, in the second modification, the operation of the ground fault detector 6 can be confirmed using the test current line 11, and the sensitivity of the current sensor 6a can be maintained with high accuracy. Further, since the test current line 11 is independent of the ground line 6f, the electromagnetic influence on the ground line 6f can be reduced.

(Third Modification)
A third modification of the present embodiment will be described with reference to FIG. In the third modification, the current sensor 6a of the ground fault detector 6 is an annular sensor, and the test current wire 11 is wound around the current sensor 6a a plurality of times. For this reason, if the number of windings is N with respect to the number of windings 1, the test current for obtaining the same sensor output can be reduced to 1 / N. it can.

(Fourth modification)
A fourth modification of the present embodiment will be described with reference to FIG. In the fourth modification, offset correction of the current sensor 6a of the ground fault detector 6 is performed, and as shown in FIG. A current of the opposite polarity is sent.

  Hereinafter, an operation procedure of offset correction of the ground fault detector 6 according to Modification 4 will be described with reference to the flowchart of FIG. First, in a state where it is ensured that no current flows through the grounding wire 6f, a DC current having a polarity on the test current wire 11 is supplied (S71), and the sensor output of the current sensor 6a of the ground fault detector 6 is supplied. A value of 1 is obtained (S72). Next, a DC current having a reverse polarity is passed through the test current line 11 (S73), and a sensor output value 2 in the current sensor 6a of the ground fault detector 6 is obtained (S74). Finally, correction is performed with the average value of (sensor output value 1 + sensor output value 2) as the current zero point (S75).

  With this configuration, in the fourth modification, the offset of the current sensor 6a can be corrected by flowing the test current using the test current line 11. Moreover, the ground fault detection by the direct current of the ground fault detector 6 can be accurately performed by the correction. In addition, since the current of a certain polarity is equal to the current of the opposite polarity, the offset of the current sensor 6a can be accurately corrected even if the absolute value of the current changes due to a temperature change.

(Fifth modification)
A fifth modification of the present embodiment will be described with reference to FIG. In the fifth modification, as shown in FIG. 8A, at the time of offset correction of the current sensor 6a, the relay 4b (or circuit breaker) on the power source 4 side and the relay 7b (or circuit breaker) on the electric vehicle 7 side. Are open on either side.

  An operation procedure of offset correction of the ground fault detector 6 according to the fifth modification will be described with reference to the flowchart of FIG. First, in a state where it is ensured that no current flows through the grounding wire 6f, the relays 4b and 7b on either side are opened (S81). Next, offset correction is performed using the sensor output value from the current sensor 6a at this time as the power supply zero point (S82).

  Thus, in the present modification 5, the main circuit of the ground fault detector 6 is electrically insulated on either side, and at this time, since the power source 4 is not connected to the ground line 6f, Of course, no current flows through the ground line 6f. By setting the output value of the current sensor 6a in this case as the current zero point, the current sensor 6 can be offset-corrected, and a low-consumption configuration that does not allow the test current to flow can be achieved.

(Sixth Modification)
A sixth modification of the present embodiment will be described with reference to FIG. In the sixth modification, as shown in FIG. 9A, the conductive cable 5 is connected to the neutral point of a pair of feeders 5a and resistance elements 6b and 6c through which a direct current flows during charging and discharging. It consists of a sheath 5c of insulating resin that covers the wire 5b and the ground wire 5b. Moreover, as shown in FIG.9 (b), the conductive cable 5 accommodates the ground fault detector 6 integrally in the inside of a control unit. With this configuration, the ground line 5 b is connected to the ground provided on the power supply 4 side, and the ground line 5 b is integrated with the conductive cable 5. Moreover, since the ground wire 5b can be arrange | positioned so that the cable outer sheath 5c may be followed, the possibility of the electric shock of a human body can be reduced.

(Seventh Modification)
A seventh modification of the present embodiment will be described with reference to FIG. In the seventh modification, the power source 4 includes a ground fault detector 6. In this configuration, since it is not necessary for the conductive cable 5 to include the ground fault detector 6, the conductive cable 5 can be reduced in size and weight, and the charge / discharge work can be facilitated while preventing electric shock to the human body. it can. The present invention is not limited to the configuration of the embodiment described above, and various modifications can be made without departing from the spirit of the invention.

S Charging / Discharging System 1 AC Power Supply 2 Distribution Panel 3 Load 4 Power Supply 4a Conversion Unit 4b Relay (or Blocking Unit)
4c Output terminal 5 Conductive cable 5b Ground wire 5c Outer skin 6 Ground fault detector 6a Current sensor (annular sensor)
6b, 6c Grounding resistance 6d Ground fault judgment unit 6e Grounding 6f Grounding wire 6g Neutral point 7 Electric vehicle 7b Relay (or blocking unit)
7c Output terminal 8 Human resistance 10 Communication unit (communication means)
11 Test current line

Claims (15)

A ground fault detector for detecting the occurrence of a ground fault, connected to a power cable for charging and discharging electric power insulated from the ground, and a conductive cable connecting between the electric vehicle,
A current sensor for detecting a ground fault current in the conductive cable;
A current value that is approximately half of the human body protection current is set as a threshold value, and it is determined that a ground fault has occurred when a detected current detected by the current sensor exceeds the threshold value, and the power source and / or the electric vehicle is A ground fault detector, comprising: a ground fault determination unit that controls to stop the output of electric power.   The ground fault detector according to claim 1, wherein the threshold is approximately 10 mA.   3. The ground fault detection according to claim 1, wherein the ground fault determination unit controls both the power source and the electric vehicle to stop outputting power to the conductive cable substantially simultaneously. vessel.   The ground fault detector according to any one of claims 1 to 3, wherein the power source includes a circuit breaker or a relay for turning on and off the electric circuit on an output terminal side thereof.   The ground fault detector according to any one of claims 1 to 3, wherein the electric vehicle includes a circuit breaker or a relay for turning on / off the electric circuit on an output terminal side thereof.   The ground fault detector according to claim 4, further comprising a communication unit that transmits a control signal for turning on / off a circuit breaker or a relay included in the power source to the power source.   6. The ground fault detector according to claim 5, further comprising communication means for transmitting a control signal for turning on / off a circuit breaker or a relay provided in the electric vehicle to the electric vehicle. The current sensor is an annular sensor;
The ground fault detector further includes:
A pair of resistance elements connected in series between the feeder lines of the conductive cable and having the same resistance value;
A ground wire connecting the neutral point of the pair of resistance elements and the ground, and
The ground fault detector according to any one of claims 1 to 7, wherein the grounding wire is penetrated through an opening of the annular sensor.   The ground fault detector according to claim 8, wherein a test current line for correcting an offset of the current sensor is passed through the opening of the annular sensor.   The ground fault detector according to claim 9, wherein the test current line is wound around the annular sensor a plurality of times.   The current zero point is the average value of the output value of the current sensor when a current of a certain polarity is passed through the test current line and the output value of the current sensor when a current of opposite polarity of the same magnitude is passed. The ground fault detector according to claim 9 or 10, wherein:   The current sensor is offset-corrected by opening an electric circuit for the conductive cable of the power source and the electric vehicle, and setting an output value of the current sensor at this time as a current zero point. Or the ground fault detector of 10.   The ground fault detector according to any one of claims 1 to 12, wherein the ground fault detector is provided integrally with the conductive cable.   The ground fault detector according to any one of claims 1 to 12, wherein the ground fault detector is provided in the power source.   The power supply for charging / discharging electric power insulated from the ground, an electric vehicle, a conductive cable connecting the power source and the electric vehicle, and the ground fault according to any one of claims 1 to 14. A charge / discharge system comprising: a detector;