Ground fault detector

Abstract

To provide a ground fault detector that can detect a ground fault with a certain sensitivity regardless of the potential difference between a positive electrode and a negative electrode of a DC bus while reducing wasteful consumption of current flowing when the ground fault does not occur.SOLUTION: A ground fault detector 1 according to the present invention comprises: a first rectifying element D1, a cathode of which is connected to a positive electrode line Vp; a first internal power supply V1, an anode of which is connected to the anode of the first rectifying element D1; a second internal power supply V2, an anode of which is connected to a cathode of the first internal power supply V1; and a second rectifying element D2, a cathode of which is connected to a cathode of the second internal power supply V2, and an anode of which is connected to a negative electrode line Vn. All these components are connected in series. A ground line GL is arranged extending from a connection point between the cathode of the first internal power supply V1 and the anode of the second internal power supply V2 to a ground G. A detector unit Du includes a detection resistor Rd to which a voltage of the first internal power supply V1 or the second internal power supply V2 is applied when a ground fault occurs.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a ground fault detector for detecting a ground fault in a DC circuit using a DC bus.

Background Art

[0002] Conventionally, in a DC circuit, in order to suppress the consumption current flowing in from the anode side of the DC circuit when no ground fault occurs, a ground fault detector is provided with two constant voltage elements each having a breakdown voltage of approximately half of the DC power supply voltage (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above-described conventional ground fault detector, since the magnitude of the ground fault current flowing when a ground fault occurs is based on the potential difference between the positive or negative side of the DC bus and the ground fault occurrence location, in one DC circuit, when the potential difference between the positive and negative poles of the DC bus varies for each area, since the detection resistance value is constant, the magnitude of the ground fault current changes for each area, and the sensitivity of the ground fault detector for detecting the ground fault becomes different.

[0005] An object of the present invention is to provide a ground fault detector that can detect a ground fault with a constant sensitivity without being affected by the potential difference between the positive and negative poles of the DC bus while suppressing unnecessary consumption current flowing in when no ground fault occurs.

Means for Solving the Problems

[0006] In view of such a situation, as a result of intensive studies, the inventor of the present invention has found that by providing an internal power source having a predetermined voltage in the ground fault detector, if a ground fault occurs, the ground fault detector will detect the potential difference between the internal power source in the ground fault detector and the ground fault location being applied to the detection unit. Therefore, the ground fault can be detected with a certain sensitivity without being affected by the potential difference between the positive and negative poles of the DC bus, and thus the present invention has been achieved.

[0007] The ground fault detector according to the present invention includes a first rectifying element having a cathode connected to the positive electrode line of a DC bus extending from a DC power source, a first internal power source having an anode connected to the anode of the first rectifying element, a second internal power source having an anode connected to the cathode of the first internal power source, and a second rectifying element having a cathode connected to the cathode of the second internal power source and an anode connected to the negative electrode line of the DC bus extending from the DC power source, which are connected in series. A ground wire extending from the connection point between the cathode of the first internal power source and the anode of the second internal power source to the ground is provided, and it includes a detection unit having a detection resistor to which the voltage of the first internal power source or the second internal power source is applied when a ground fault occurs.

[0008] According to such a ground fault detector, while the useless current flowing in when no ground fault occurs is suppressed by the first rectifying element and the second rectifying element, the potential difference between either the first internal power source or the second internal power source and the location where the ground fault occurs is applied to the detection unit and the detection unit detects the detection current. Therefore, the detection unit can detect the ground fault with a certain sensitivity without being affected by the potential difference between the positive electrode line and the negative electrode line of the DC bus.

[0009] Also, it is preferable that the detection unit is provided on the ground wire.

[0010] According to such a ground fault detector, since the detection current passes through the ground wire whether a ground fault occurs on the positive electrode line side or the negative electrode line side, by providing the detection unit on the ground wire, the ground fault can be detected efficiently.

[0011] Also, it is preferable that the detection unit is provided respectively between the anode of the first rectifying element and the anode of the first internal power source, and between the cathode of the second internal power source and the cathode of the second rectifying element.

[0012] According to such a ground fault detector, a detection unit provided between the anode of the first rectifying element and the anode of the first internal power source detects a ground fault that has occurred on the positive electrode line side, and a detection unit provided between the cathode of the second internal power source and the cathode of the second rectifying element detects a ground fault that has occurred on the negative electrode line side. Therefore, it is possible to easily know on which side of the positive electrode line and the negative electrode line the ground fault has occurred depending on which detection unit has detected the ground fault.

[0013] Further, the ground fault detector according to the present invention includes a first rectifying element having a cathode connected to the positive electrode line of a DC bus extending from a DC power source, and a second rectifying element having an anode connected to the negative electrode line of the DC bus extending from the DC power source, which are connected in series. A ground line extending from a connection point where the anode of the first rectifying element and the cathode of the second rectifying element are connected to the ground, and an internal power source having an anode connected between the anode of the first rectifying element and the connection point and a cathode connected between the connection point and the cathode of the second rectifying element are provided. A detection unit having a detection resistor to which the voltage of the internal power source is applied when a ground fault occurs is provided on the ground line.

[0014] According to such a ground fault detector, while wasteful current flowing in when no ground fault occurs is suppressed by the first rectifying element and the second rectifying element, a potential difference between either the anode or the cathode of the internal power source and the ground fault location is applied to the detection unit and the detection unit detects a detection current. Therefore, the detection unit can detect a ground fault with a certain sensitivity without being affected by the potential difference between the positive electrode line and the negative electrode line of the DC bus.

[0015] Further, it is preferable that a first resistor element is provided between the anode of the internal power source and the connection point, and a second resistor element is provided between the connection point and the cathode of the internal power source.

[0016] According to such a ground fault detector, by providing two resistor elements between the anode and the cathode of the internal power source provided in the ground fault detector, a circuit for detecting a ground fault with the internal power source can be configured.

[0017] Also, it is preferable that a first constant voltage element is provided between the anode of the internal power supply and the connection point, and a second constant voltage element is provided between the connection point and the cathode of the internal power supply.

[0018] According to such a ground fault detector, by providing two constant voltage elements between the anode and the cathode of the internal power supply provided in the ground fault detector, not only can a ground fault be detected, but also wasteful consumption current flowing in when no ground fault occurs can be suppressed.

[0019] Furthermore, the ground fault detector according to the present invention includes a first rectifying element having a cathode connected to the positive electrode line of the DC bus extending from the DC power supply, a second rectifying element having an anode connected to the negative electrode line of the DC bus extending from the DC power supply, and an internal power supply circuit having an anode connected to the anode of the first rectifying element and a cathode connected to the cathode of the second rectifying element, which are connected in series. A detection unit having a detection resistor to which the voltage of the internal power supply is applied when a ground fault occurs is provided on the ground wire extending to the ground.

[0020] According to such a ground fault detector, while wasteful consumption current flowing in when no ground fault occurs is suppressed by the first rectifying element and the second rectifying element, a potential difference between either the anode or the cathode of the internal power supply circuit and the ground fault location is applied to the detection unit and the detection unit detects a detection current. Therefore, the detection unit can detect a ground fault with a certain sensitivity without being affected by the potential difference between the positive electrode line and the negative electrode line of the DC bus.

Effect of the Invention

[0021] Thereby, it is possible to provide a ground fault detector that can suppress wasteful consumption current flowing in when no ground fault occurs and detect a ground fault current with a certain sensitivity without being affected by the potential difference between the positive electrode and the negative electrode of the DC bus.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

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Figure 7

Embodiments for Carrying Out the Invention

[0023] Hereinafter, embodiments of the ground fault detector according to the present invention will be described with reference to the drawings. In each figure, components denoted by the same reference numerals are the same components, and the description thereof will be omitted.

[0024] FIG. 1 is a circuit diagram showing the configuration of a ground fault detector 1 according to the first embodiment of the present invention. The ground fault detector 1 shown in FIG. 1 is provided between a positive electrode line Vp and a negative electrode line Vn, which are DC buses extending from a DC power supply (not shown) to a load (not shown), and one end is connected to the ground G. The DC power supply is not limited to this as long as it supplies a DC current to the load, such as a solar panel or a storage battery.

[0025] The ground fault detector 1 is composed of a first rectifying element D1, a second rectifying element D2, a first internal power supply V1, a second internal power supply V2, and a detection unit Du. Further, in the ground fault detector 1, between the positive electrode line Vp and the negative electrode line Vn, the first rectifying element D1, the first internal power supply V1, the second internal power supply V2, and the second rectifying element D2 are connected in series with each other. The first rectifying element and the second rectifying element are diodes or the like, and any element that can pass only current from one direction may be used. The internal power supply may be a battery, a battery, a capacitor, or the like, as long as it is an element that supplies a DC voltage.

[0026] The first rectifying element D1 has its cathode connected to the positive electrode line Vp and its anode connected to the anode of the first internal power supply V1. The second rectifying element D2 has its cathode connected to the cathode of the second internal power supply V2 and its anode connected to the negative electrode line Vn.

[0027] The ground fault detector 1 is configured such that one end of the cathode of the first internal power supply V1 is connected to one end of the anode of the second internal power supply V2 to form a connection point P1. A ground line GL extending toward the ground G is provided at the connection point P1. A detection unit Du having a detection resistor Rd is provided on the ground line GL.

[0028] The operations of various ground fault detectors will be described. Note that since the voltage between the positive electrode line Vp and the negative electrode line Vn of the DC bus has no influence on the detection of the ground fault in the ground fault detector 1, the description thereof is omitted.

[0029] During normal times when no ground fault occurs, the ground fault detector 1 suppresses the current (not shown) flowing from the positive electrode line Vp to the negative electrode line Vn through the first rectifying element D1 and the second rectifying element D2. When a ground fault occurs on either the positive electrode line Vp side or the negative electrode line Vn side, the location where the ground fault occurs is connected to the ground G, forming a first closed-loop circuit CL1 including the first rectifying element D1, the first internal power supply V1, and the detection unit Du, or a second closed-loop circuit CL2 including the second rectifying element D2, the second internal power supply V2, and the detection unit Du. FIG. 2 is a schematic diagram showing the operation when the first detection current Id1 is detected by the ground fault detector 1 shown in FIG. 1. FIG. 3 is a schematic diagram showing the operation when the second detection current is detected by the ground fault detector shown in FIG. 1.

[0030] When the first closed-loop circuit CL1 is formed, as shown in FIG. 2, the voltage of the first internal power supply V1 is applied to the detection resistor Rd of the detection unit Du. Due to the voltage of the first internal power supply V1 applied to the detection resistor Rd, a first detection current Id1 is generated and flows in the forward direction of the first rectifying element D1. The detection unit Du detects the first detection current Id1 to detect that the ground fault detector 1 has a ground fault.

[0031] When the second closed-loop circuit CL2 is formed, as shown in FIG. 3, the voltage of the second internal power source V2 is applied to the detection resistor Rd included in the detection unit Du. Due to the voltage of the second internal power source V2 applied to the detection resistor Rd, a second detection current Id2 is generated and flows in the forward direction of the second rectifying element D2. The detection unit Du detects that the ground fault detector 1 has grounded by detecting the second detection current Id2.

[0032] Note that since the voltage of the first internal power source V1 applied to the detection resistor Rd in the first closed-loop circuit CL1 is equal to the voltage of the second internal power source V2 applied to the detection resistor Rd in the second closed-loop circuit CL2, the first detection current Id1 detected by the detection unit Du in the first closed-loop circuit CL1 and the second detection current Id2 detected by the detection unit Du in the second closed-loop circuit CL2 are also equal. Also, the first internal power source V1 and the second internal power source V2 have equal voltages to each other.

[0033] FIG. 4 is a circuit diagram showing the configuration of the ground fault detector 1A according to the second embodiment of the present invention. The ground fault detector 1A shown in FIG. 4 is different from the above-mentioned ground fault detector 1 in that the detection unit Du is included for each of the closed-loop circuits CL1 and CL2. The first detection unit Du1 included in the first closed-loop circuit CL1 is provided between the anode of the first rectifying element D1 and the anode of the first internal power source V1. The second detection unit Du2 included in the second closed-loop circuit CL2 is provided between the cathode of the second internal power source V2 and the cathode of the second rectifying element D2.

[0034] When the first detection unit Du1 detects the first detection current Id1, it can be detected that the ground fault detector 1A has grounded on the positive electrode line Vp side. When the second detection unit Du2 detects the second detection current Id2, it can be detected that the ground fault detector 1A has grounded on the negative electrode line Vn side. Thereby, it is possible to easily know on which side of the positive electrode line Vp and the negative electrode line Vn the ground fault has occurred depending on which of the first detection unit Du1 and the second detection unit Du2 has detected the ground fault.

[0035] FIG. 5 is a circuit diagram showing the configuration of the ground fault detector 1B according to the third embodiment of the present invention. The ground fault detector 1B shown in FIG. 5 is different from the above-described ground fault detector 1 and ground fault detector 1A, and is composed of a single internal power supply V12, and the internal power supply V12 is equal to the sum of the first internal power supply V1 and the second internal power supply V2.

[0036] In the ground fault detector 1B, the first rectifying element D1 and the second rectifying element D2 are connected in series and are in the forward direction from the negative electrode line Vn side toward the positive electrode line Vp side. The anode of the first rectifying element D1 and the cathode of the second rectifying element D2 are connected to form a connection point P2. The ground fault detector 1B is provided with a ground line GL extending from the connection point P2 toward the ground G, and the detection unit Du is provided on the ground line GL.

[0037] The ground fault detector 1B further includes a first resistance element R1 and a second resistance element R2 having equal resistance values. The first resistance element R1 is provided between the anode of the internal power supply V12 and the connection point P2, and the second resistance element R2 is provided between the connection point P2 and the cathode of the internal power supply V12.

[0038] When a ground fault occurs on either the positive electrode line Vp side or the negative electrode line Vn side, the voltage of the internal power supply V12 applied to the detection resistance Rd of the detection unit Du is divided by the first resistance element R1 and the second resistance element R2, thereby forming a circuit for detecting a ground fault with the internal power supply. As a result, the detection unit Du detects the first detection current Id1 or the second detection current Id2, and the ground fault detector 1B detects that a ground fault has occurred on either the positive electrode line Vp side or the negative electrode line Vn side. Further, if the voltage applied to the first resistance element R1 and the second resistance element R2 during a ground fault is detected, it is possible to determine on which side, the positive electrode line Vp side or the negative electrode line Vn side, the ground fault has occurred.

[0039] FIG. 6 is a circuit diagram showing the configuration of the ground fault detector 1C according to the fourth embodiment of the present invention. Different from the ground fault detector 1B shown in FIG. 5, the ground fault detector 1C shown in FIG. 5 is provided with a first constant voltage element ZD1 between the anode of the internal power supply V12 and the connection point P2, and a second constant voltage element ZD2 is provided between the connection point P2 and the cathode of the internal power supply V12. The first constant voltage element ZD1 and the second constant voltage element ZD2 are connected in series in the same manner as the first rectifying element D1 and the second rectifying element D2, and are in the forward direction from the negative electrode line Vn side to the positive electrode line Vp side.

[0040] The first constant voltage element ZD1 and the second constant voltage element ZD2 can suppress the wasteful current flowing into the detection unit Du when no ground fault occurs. Thereby, when a ground fault occurs on either the positive electrode line Vp side or the negative electrode line Vn side, the ground fault detector 1C can detect the occurrence of the ground fault at the detection unit Du while suppressing the current consumption by the first constant voltage element ZD1 and the second constant voltage element ZD2.

[0041] FIG. 7 is a circuit diagram showing the configuration of the ground fault detector 1D according to the fifth embodiment of the present invention. Different from the ground fault detectors 1, 1A, 1B, 1C described above, the ground fault detector 1D shown in FIG. 7 uses an internal power supply circuit PC instead of the internal power supplies V12, V1, and V2.

[0042] The ground fault detector 1D includes a first rectifying element D1 having its cathode connected to the positive electrode line Vp, a second rectifying element D2 having its anode connected to the negative electrode line Vn, and an internal power supply circuit PC having its anode connected to the anode of the first rectifying element D1 and its cathode connected to the cathode of the second rectifying element D2, which are connected in series. The internal power supply circuit PC is provided with a ground line GL extending from the inside toward the ground G, and the detection unit Du is provided on the ground line GL. The internal power supply circuit PC provides an internal voltage Vc applied to the detection resistor Rd included in the detection unit Du. The value of the internal voltage Vc is equal to the first internal power supply V1 and the second internal power supply V2 described above.

[0043] When a ground fault occurs on either the positive electrode line Vp side or the negative electrode line Vn side, the voltage of the internal power supply circuit PC is applied to the detection resistor Rd, and the first detection current Id1 or the second detection current Id2 flows. The detection unit Du detects the first detection current Id1 or the second detection current Id2, whereby the ground fault detector 1D detects that a ground fault has occurred on either the positive electrode line Vp side or the negative electrode line Vn side. Note that the internal power supply circuit PC only needs to be able to supply the DC voltage necessary for the ground fault detector 1D, and is not limited to this as long as it is a circuit that can supply the DC voltage necessary for the detection unit Du to detect a ground fault.

[0044] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to such examples, and it goes without saying that the present invention can be implemented in various forms without departing from the gist of the present invention.

Explanation of Reference Numerals

[0045] 1, 1A, 1B, 1C, 1D Ground fault detector CL1 First closed-loop circuit CL2 Second closed-loop circuit Du Detection unit Du1 First detection unit Du2 Second detection unit G Ground GL Ground wire Id1 First detection current Id2 Second detection current P1 Connection point P2 Connection point PC Internal power supply circuit Rd Detection resistor V12, V1, V2, Vc Internal power supply Vn Negative electrode line Vp Positive electrode line

Claims

1. A first rectifying element having a cathode connected to the positive electrode line of a DC bus extending from a DC power source, a first internal power source having an anode connected to the anode of the first rectifying element, a second internal power source having an anode connected to the cathode of the first internal power source, a second rectifying element having a cathode connected to the cathode of the second internal power source and an anode connected to the negative electrode line of a DC bus extending from a DC power source, wherein the first rectifying element, the first internal power source, the second internal power source, and the second rectifying element are connected in series, a grounding line extending from the connection point between the cathode of the first internal power source and the anode of the second internal power source to the ground is provided, A ground fault detector including a detection unit having a detection resistor to which the voltage of the first internal power source or the second internal power source is applied when a ground fault occurs.

2. The detection unit is provided on the grounding line, and the ground fault detector according to Claim 1.

3. The detection unit is provided between the anode of the first rectifying element and the anode of the first internal power source and between the cathode of the second internal power source and the cathode of the second rectifying element, respectively, and the ground fault detector according to Claim 1.

4. A first rectifying element having a cathode connected to the positive electrode line of a DC bus extending from a DC power source and a second rectifying element having an anode connected to the negative electrode line of a DC bus extending from a DC power source are connected in series, a grounding line extending from the connection point where the anode of the first rectifying element and the cathode of the second rectifying element are connected to the ground, an internal power source having an anode connected between the anode of the first rectifying element and the connection point and a cathode connected between the connection point and the cathode of the second rectifying element is provided, A ground fault detector in which a detection unit having a detection resistor to which the voltage of the internal power source is applied when a ground fault occurs is provided on the grounding line.

5. A first resistance element is provided between the anode of the internal power source and the connection point, and a second resistance element is provided between the connection point and the cathode of the internal power source, and the ground fault detector according to Claim 4.

6. A first constant voltage element is provided between the anode of the internal power source and the connection point, and a second constant voltage element is provided between the connection point and the cathode of the internal power source, and the ground fault detector according to Claim 4.

7. A first rectifying element having a cathode connected to the positive electrode line of a DC bus extending from a DC power source, a second rectifying element having an anode connected to the negative electrode line of a DC bus extending from a DC power source, and an internal power source circuit having an anode connected to the anode of the first rectifying element and a cathode connected to the cathode of the second rectifying element are connected in series, The internal power supply circuit is provided with a ground wire extending to the ground, A ground fault detector in which a detection unit having a detection resistor to which the voltage of the internal power supply is applied when a ground fault occurs is provided on the ground wire.

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