JP7474450B1 - Earth fault detector - Google Patents

Abstract

The present invention provides a ground fault detector that can distinguish not only a ground fault on either the positive or negative side, but also a balanced ground fault from the detection result without performing any calculation. [Solution] The device is provided between a positive pole line Vp and a negative pole line Vn extending from a DC power source, and includes a first resistance element R1, a second resistance element R2, and a third resistance element R3, a first self-extinguishing element Q1, a second self-extinguishing element Q2, and a detection unit 10, and is provided with a switching unit SW having one end connected to a first connection point P1 where the first resistance element R1 and the second resistance element R2 are connected, and the other end connected to a third connection point P3 where the ground terminals TG1, TG2 of the first self-extinguishing element Q1 and the second self-extinguishing element Q2 are connected to each other, which generates a potential difference between the second connection point P2 and the third connection point P3 in either an on state or an off state, and detects whether an earth fault current Ig has flowed through the detection unit 10 in the on state or the off state, and distinguishes between a positive pole side earth fault, a negative pole side earth fault, and a balanced earth fault. [Selected Figure] Figure 1

Description

The present invention relates to a DC earth fault detector that detects balanced earth faults.

When a ground fault occurs under equal conditions at both the positive and negative poles, a ground fault detector that uses neutral grounding is unable to detect the ground fault current because no potential difference occurs between the neutral and ground.

For this reason, a ground fault detector has been proposed that provides voltage division detectors for detecting the divided voltage on both the positive and negative poles, and includes a processor that determines whether a balanced ground fault has occurred based on the results detected by each voltage division detector (Patent Document 1).

JP 2021-156673 A

However, a ground fault detector that detects such balanced ground faults cannot determine whether a balanced ground fault exists unless it uses complex circuits to calculate the change in divided voltage.

In light of this, the present invention provides a ground fault detector that can distinguish between ground faults on either the positive or negative side, as well as balanced ground faults, from the detection results without performing any calculations.

The ground fault detector according to the present invention comprises a first resistive element, a second resistive element, and a third resistive element connected in series between a positive pole line and a negative pole line extending from a DC power source, a first self-extinguishing element having an input terminal connected to a second connection point where one end of the second resistive element and one end of the third resistive element are connected and an output terminal connected to the positive pole line, a second self-extinguishing element having an input terminal connected to the second connection point and an output terminal connected to the negative pole line, and a third connection point where the ground terminals of the first self-extinguishing element and the second self-extinguishing element are connected to each other, and is provided between the ground and the ground. A detection unit is provided, the switching unit having one end connected to a first connection point where one end of the first resistive element and the other end of the second resistive element are connected, and the other end connected to the third connection point, switching between an on state and an off state at regular intervals between the first connection point and the third connection point, and generating a potential difference between the second connection point and the third connection point in either the on state or the off state, and the detection unit detects whether a ground fault current that flows when a ground fault occurs flows between the third connection point and the ground in the on state and the off state of the switching unit.

The ground fault detector according to the present invention includes a first resistive element, a second resistive element, and a third resistive element connected in series between a positive pole line Vp and a negative pole line Vn extending from a DC power source, a first self-extinguishing element having an input terminal connected to a first connection point at which one end of the first resistive element and one end of the second resistive element are connected and an output terminal connected to the positive pole line, a second self-extinguishing element having an input terminal connected to the first connection point and an output terminal connected to the negative pole line, and a third connection point at which the ground terminals of the first self-extinguishing element and the second self-extinguishing element are connected to each other and a ground. A switching unit is provided, which has one end connected to a second connection point where the other end of the second resistive element and one end of the third resistive element are connected, and the other end connected to the third connection point, and switches between an on state and an off state at regular intervals between the second connection point and the third connection point, and generates a potential difference between the first connection point and the third connection point in either the on state or the off state, and the detection unit detects whether a ground fault current that flows when a ground fault occurs flows between the third connection point and the ground in the on state and the off state of the switching unit.

With this type of ground fault detector, it is possible to determine not only ground faults on either the positive or negative side, but also balanced ground faults from the detection results without performing any calculations.

In addition, when the switching unit SW is turned on, it is preferable that the first self-extinguishing element Q1 is turned off and the second self-extinguishing element Q2 is turned on.

In addition, when the switching unit SW is turned on, it is preferable that the first self-extinguishing element Q1 is turned on and the second self-extinguishing element Q2 is turned off.

With this type of earth fault detector, even if no potential difference occurs due to a balanced earth fault, a potential difference occurs due to the switching unit, and the detection unit can detect the earth fault current.

In addition, it is preferable that the detection unit distinguishes between a positive side earth fault, which is an earth fault that has occurred on the positive line side, a negative side earth fault, which is an earth fault that has occurred on the negative line side, or a balanced earth fault, which is an earth fault that has occurred under equal conditions on both the positive line side and the negative line side, based on the detection result of the earth fault current in the on and off states of the switching unit.

In addition, in the case where the detection result shows that the earth fault current is detected when the switching unit is in the on state and also when the switching unit is in the off state, the detection unit determines that the fault is the positive pole side earth fault, in the case where the detection result shows that the earth fault current is not detected when the switching unit is in the on state and the earth fault current is detected when the switching unit is in the off state, the detection unit determines that the fault is the negative pole side earth fault, and in the case where the detection result shows that the earth fault current is detected when the switching unit is in the on state and the earth fault current is not detected when the switching unit is in the off state, the detection unit preferably determines that the fault is the balanced earth fault.

In addition, in the case of a detection result in which the earth fault current is not detected in the on state of the switching unit and the earth fault current is detected in the off state of the switching unit, the detection unit determines that the fault is the positive pole side earth fault, in the case of a detection result in which the earth fault current is detected in the on state of the switching unit and the earth fault current is also detected in the off state of the switching unit, the detection unit determines that the fault is the negative pole side earth fault, and in the case of a detection result in which the earth fault current is detected in the on state of the switching unit and the earth fault current is not detected in the off state of the switching unit, the detection unit preferably determines that the fault is the balanced earth fault.

As a result, it is possible to easily determine whether a ground fault that has occurred on the circuit is a positive ground fault, a negative ground fault, or a balanced ground fault from the detection results of the detection unit when the switching unit is in the on state and the detection results of the detection unit when the switching unit is in the off state.

The present invention provides a ground fault detector that can determine not only a ground fault on either the positive or negative side, but also a balanced ground fault from the detection results without performing any calculations.

1 is a circuit diagram showing a circuit configuration of a ground fault detector according to a first embodiment of the present invention. 2A and 2B are schematic diagrams showing a ground fault current that flows in the case of a positive ground fault when the switching unit of the ground fault detector shown in FIG. 1 is in an off state (a) and an on state (b). 2A and 2B are schematic diagrams showing a ground fault current that flows in the case of a negative pole side ground fault when the switching unit of the ground fault detector shown in FIG. 1 is in an off state (a) and an on state (b). 2A and 2B are schematic diagrams showing a ground fault current that flows in the case of a balanced ground fault when the switching unit of the ground fault detector shown in FIG. 1 is in an off state (a) and an on state (b). FIG. 4 is a circuit diagram showing a circuit configuration of a ground fault detector according to a second embodiment of the present invention.

The following describes an embodiment of the present invention with reference to the drawings. Note that components with the same reference numerals in each drawing are the same, and their description will be omitted.

Figure 1 is a circuit diagram showing the circuit configuration of a ground fault detector 1 according to a first embodiment of the present invention. The ground fault detector 1 according to the first embodiment shown in Figure 1 is provided between a positive pole line Vp and a negative pole line Vn extending from a DC power source (not shown) to a load (not shown), and one end is connected to ground G. The DC power source is not limited to a solar panel, a storage battery, or any other power source that supplies DC current to the load.

The earth fault detector 1 includes a first resistor element R1, a second resistor element R2, and a third resistor element R3 connected in series with each other, a first self-extinguishing element Q1 and a second self-extinguishing element Q2, and a detection unit 10.

The first resistor element R1 and the second resistor element R2 are connected at one end to one end of the second resistor element R2 to form a first connection point P1. The second resistor element and the third resistor element R3 are connected at the other end to the third resistor element R3 to form a second connection point P2. In the first embodiment, the earth fault detector 1 has the second connection point P2 as a neutral point.

The first self-extinguishing element Q1 and the second self-extinguishing element Q2 connect the ground terminals TG1, TG2 to each other to form a third connection point P3. The first self-extinguishing element Q1 has an input terminal TI1 connected to the second connection point P2 and an output terminal TO1 connected to the positive electrode line Vp. The second self-extinguishing element Q2 has an input terminal TI2 connected to the second connection point P2 and an output terminal TO2 connected to the negative electrode line Vn. For example, the first self-extinguishing element Q1 is an N-channel metal-oxide-semiconductor field-effect transistor (MOSFET), and the second self-extinguishing element Q2 is a PNP bipolar transistor.

The earth fault detector 1 is provided with a switching unit SW having one end connected to the first connection point P1 and the other end connected to the third connection point P3. The switching unit SW switches between the on state and the off state at regular intervals between the first connection point P1 and the third connection point P3. When the switching unit SW is in the on state, a potential difference is generated between the second connection point P2 and the third connection point P3 to turn on the second self-extinguishing element Q2. For example, the switching unit SW includes an oscillator unit 2 that steadily outputs a clock signal at regular intervals, and a switching element 3 that switches between the off state and the on state between the first connection point P1 and the third connection point P3 when a clock signal is input. In the first embodiment, the switching element 3 is an N-channel MOSFET.

The detection unit 10 is provided between the third connection point P3 and the ground G, and detects whether a ground fault current Ig flows through the ground G when a ground fault occurs in the on and off states of the switching unit, and determines whether a ground fault has occurred on either the positive electrode line Vp side or the negative electrode line Vn side, or whether a ground fault of the same magnitude has occurred on both the positive electrode line Vp side and the negative electrode line Vn side, i.e., a balanced ground fault. Note that the structure of the detection unit 10 is well known, so a description thereof will be omitted.

The following describes how the ground fault detector 1 according to the first embodiment distinguishes between ground faults. FIG. 2 shows the ground fault current Ig that flows when a positive ground fault occurs when the switching unit SW of the ground fault detector 1 shown in FIG. 1 is in the off state (a) and on state (b). FIG. 3 shows the ground fault current Ig that flows when a negative ground fault occurs when the switching unit SW of the ground fault detector 1 shown in FIG. 1 is in the off state (a) and on state (b). FIG. 4 shows the ground fault current Ig that flows when a balanced ground fault occurs when the switching unit SW of the ground fault detector 1 shown in FIG. 1 is in the off state (a) and on state (b). The ground fault current Ig that flows when a ground fault occurs flows to the ground G via the ground fault resistor Rg, and the resistance value of the ground fault resistor Rg is small and equal to zero.

The earth fault detector 1 detects the earth fault current Ig in each of the on and off states switched by the switching unit SW. When an earth fault occurs on the positive pole line Vp side, when the switching unit SW is in the off state, the potential of the third connection point P3 is higher than the potential of the second connection point P2, so the second self-extinguishing element Q2 is turned on. As shown in FIG. 2(a), the earth fault current Ig flows from the ground fault location on the positive pole line Vp side to the ground G, and from the ground G to the negative pole line Vn via the second self-extinguishing element Q2. At that time, the detection unit 10 detects the passage of the earth fault current Ig. Even when the switching unit SW is in the on state, the potential of the third connection point P3 is higher than the potential of the second connection point P2, so the second self-extinguishing element Q2 is turned on. As shown in FIG. 2(b), the ground fault current Ig flows from the point where the ground fault occurred on the positive pole line Vp to the ground G, and then flows from the ground G to the negative pole line Vn via the second self-extinguishing element Q2. At that time, the detection unit 10 detects the passage of the ground fault current Ig.

When a ground fault occurs on the negative pole line Vn side, if the switching unit SW is in the off state, the potential of the third connection point P3 is lower than the potential of the first connection point P1, so the first self-extinguishing element Q1 is turned on. As shown in FIG. 3(a), the ground fault current Ig flows from the third connection point P3 to the ground G through the first self-extinguishing element Q1, and flows from the ground fault point on the negative pole line Vn side to the negative pole line Vn. The detection unit 10 detects the passage of the ground fault current Ig. When the switching unit SW is in the on state, the potential of the third connection point P3 is higher than the potential of the second connection point P2, so the second self-extinguishing element Q2 is turned on. At that time, instead of the ground fault current Ig flowing to the ground G, the through current It flowing from the positive pole line Vp to the negative pole line Vn flows into the switching element 3 as shown in FIG. 3(b), and flows to the negative pole line Vn through the second self-extinguishing element Q2. As a result, the detection unit 10 does not detect the passage of the ground fault current Ig.

When a balanced ground fault occurs, if the switching unit SW is in the off state, the same level of ground resistance Rg occurs on both the positive pole line Vp side and the negative pole line Vn side, so no potential difference occurs, and as shown in FIG. 4(a), the ground fault current Ig does not flow. Therefore, the detection unit 10 does not detect the passage of the ground fault current Ig. When the switching unit SW is in the on state, a potential difference occurs in the potential that was balanced when the potential of the first connection point P1 is applied to the potential of the third connection point P3. The potential of the third connection point P3 becomes higher than the potential of the second connection point P2, and the second self-extinguishing element Q2 turns on. As shown in FIG. 4(b), the ground fault current Ig flows from the ground fault location on the positive pole line Vp side to the ground G, and from the ground G to the negative pole line Vn via the second self-extinguishing element Q2. At that time, the detection unit 10 detects the passage of the ground fault current Ig.

The ground fault detector 1 according to the first embodiment distinguishes a ground fault from the detection result of the detection unit 10 in the off state and on state of the switching unit SW as follows. If the detection result of the detection unit 10 shows that a ground fault current is detected in both the off state and on state of the switching unit SW, the detection unit 10 distinguishes that the ground fault is a positive side ground fault occurring on the positive pole line Vp side. If the detection result of the detection unit 10 shows that a ground fault current is detected in the off state of the switching unit SW and that a ground fault current is not detected in the on state of the switching unit SW, the detection unit 10 distinguishes that the ground fault is a negative side ground fault occurring on the negative pole line Vn side. If the detection result of the detection unit 10 shows that a ground fault current is not detected in the off state of the switching unit SW and that a ground fault current is detected in the on state of the switching unit SW, the detection unit 10 distinguishes that the ground fault is a balanced ground fault. Therefore, the ground fault detector 1 according to the first embodiment of the present invention can distinguish a positive side ground fault, a negative side ground fault, and a balanced ground fault from the detection result of the detection unit 10 without performing any calculations.

The earth fault detector 1 according to the second embodiment will be described. FIG. 5 is a circuit diagram showing the circuit configuration of the earth fault detector according to the second embodiment of the present invention. The earth fault detector 1 shown in FIG. 5 has a first connection point P1 as a neutral point. The switching unit SW switches between the second connection point P2 and the third connection point P3 between an on state and an off state at regular intervals. When the switching unit SW is in the on state, a potential difference is generated between the first connection point P1 and the third connection point P3 to turn on the first self-extinguishing element Q1. The switching element 3 according to the second embodiment is a relay switch.

The earth fault detector 1 according to the second embodiment distinguishes between ground faults as follows, based on the detection results of the detection unit 10 when the switching unit SW is in the off state and on state. If the detection result of the detection unit 10 shows that a ground fault current is detected when the switching unit SW is in the off state and that a ground fault current is not detected when the switching unit SW is in the on state, the detection unit 10 distinguishes between a positive pole side ground fault and a negative pole side ground fault. If the detection result of the detection unit 10 shows that a ground fault current is not detected when the switching unit SW is in the off state and that a ground fault current is detected when the switching unit SW is in the on state, the detection unit 10 distinguishes between a balanced ground fault and a positive pole side ground fault. Therefore, the earth fault detector 1 according to the second embodiment of the present invention can also distinguish between a positive pole side ground fault, a negative pole side ground fault, and a balanced ground fault from the detection result of the detection unit 10 without performing any calculations.

In the ground fault detector 1 according to the first and second embodiments, when the switching unit SW is in the on state, a potential difference occurs between the second connection point P2 and the third connection point P3, or between the first connection point P1 and the third connection point P3. However, when the switching unit SW is in the off state, a potential difference may also occur between the second connection point P2 and the third connection point P3, or between the first connection point P1 and the third connection point P3, but this is not limited to this.

In the first and second embodiments, the first self-extinguishing element Q1 is an N-channel MOSFET and the second self-extinguishing element Q2 is a PNP bipolar transistor, but the first self-extinguishing element Q1 may be either an NPN bipolar transistor or an insulated gate bipolar transistor (IGBT), and the second self-extinguishing element Q2 may be a P-channel MOSFET. Apart from the potential difference caused by a ground fault, it is sufficient that a potential difference occurs between the second connection point P2 and the third connection point P3, or between the first connection point P1 and the third connection point P3, when the switching unit SW is switched between the on state and the off state, and this is not limited to this.

In addition, the switching element 3 in the first embodiment is an N-channel MOSFET, and the switching element 3 in the second embodiment is a relay switch, but any switching element that can switch between the second connection point P2 and the third connection point P3, or between the first connection point P1 and the third connection point P3, between an off state and an on state may be used, and other transistors such as IGBTs may also be used.

As a result, the earth fault detector 1 according to the present invention can distinguish between a positive earth fault, a negative earth fault, and a balanced earth fault based on the detection results of the earth fault current Ig in the on and off states.

REFERENCE SIGNS LIST 1 Earth fault detector 2 Oscillator section 3 Switching element 10 Detector section G Ground Ig Earth fault current It Through current P1 First connection point P2 Second connection point P3 Third connection point Q1 First self-extinguishing element Q2 Second self-extinguishing element R1 First resistance element R2 Second resistance element R3 Third resistance element SW Switching section TG1 Ground terminal TG2 Ground terminal TI1 Input terminal TI2 Input terminal TO1 Output terminal TO2 Output terminal Vn Negative wire Vp Positive wire

Claims (7)

a first resistor R1, a second resistor R2, and a third resistor R3 connected in series between a positive electrode line Vp and a negative electrode line Vn extending from a DC power supply;
a first self-extinguishing element Q1 having an input terminal TI1 connected to a second connection point P2 at which one end of the second resistor element R2 and one end of the third resistor element R3 are connected, and an output terminal TO1 connected to the positive pole line Vp;
a second self-extinguishing element Q2 having an input terminal TI2 connected to the second connection point P2 and an output terminal TO2 connected to the negative pole line Vn;
a detection unit 10 provided between a third connection point P3 at which the ground terminals TG1, TG2 of the first self-extinguishing element Q1 and the second self-extinguishing element Q2 are connected to each other and a ground G;
a switching unit SW is provided, the switching unit SW having one end connected to a first connection point P1 at which one end of the first resistor element R1 and the other end of the second resistor element R2 are connected, the other end connected to the third connection point P3, and switching between an on state and an off state at regular intervals between the first connection point P1 and the third connection point P3, and generating a potential difference between the second connection point P2 and the third connection point P3 in either the on state or the off state;
The detection unit 10 detects whether a ground fault current Ig, which flows when a ground fault occurs, flows between the third connection point P3 and the ground G when the switching unit SW is in the on state and the off state. The earth fault detector of claim 1, wherein when the switching unit SW is turned on, the first self-extinguishing element Q1 is turned off and the second self-extinguishing element Q2 is turned on. a first resistor R1, a second resistor R2, and a third resistor R3 connected in series between a positive electrode line Vp and a negative electrode line Vn extending from a DC power supply;
a first self-extinguishing element Q1 having an input terminal TI1 connected to a first connection point P1 at which one end of the first resistor element R1 and one end of the second resistor element R2 are connected, and an output terminal TO1 connected to the positive pole line Vp;
a second self-extinguishing element Q2 having an input terminal TI2 connected to the first connection point P1 and an output terminal TO2 connected to the negative pole line Vn;
a detection unit 10 provided between a third connection point P3 at which the ground terminals TG1, TG2 of the first self-extinguishing element Q1 and the second self-extinguishing element Q2 are connected to each other and a ground G;
a switching unit SW is provided, the switching unit SW having one end connected to a second connection point P2 to which the other end of the second resistor element R2 and one end of the third resistor element R3 are connected, the other end connected to the third connection point P3, and switching between an on state and an off state at regular intervals between the second connection point P2 and the third connection point P3, and generating a potential difference between the first connection point P1 and the third connection point P3 in either the on state or the off state;
The detection unit 10 detects whether a ground fault current Ig, which flows when a ground fault occurs, flows between the third connection point P3 and the ground G when the switching unit SW is in the on state and the off state. The earth fault detector of claim 1, wherein when the switching unit SW is turned on, the first self-extinguishing element Q1 is turned on and the second self-extinguishing element Q2 is turned off. The earth fault detector according to claim 2 or 4, wherein the detection unit determines whether the earth fault is a positive earth fault that occurs on the positive line side, a negative earth fault that occurs on the negative line side, or a balanced earth fault that occurs under equal conditions on both the positive line side and the negative line side, based on the detection result of the earth fault current in the on and off states of the switching unit. When the detection result indicates that the ground fault current is detected when the switching unit is in an on state and also when the ground fault current is detected when the switching unit is in an off state, the detection unit determines that the ground fault is the positive electrode side ground fault,
When the detection result indicates that the ground fault current is not detected when the switching unit is in an on state and the ground fault current is detected when the switching unit is in an off state, the detection unit determines that the ground fault is a negative electrode side ground fault,
6. The ground fault detector according to claim 5, wherein, when the detection result shows that the ground fault current is detected when the switching unit is in an on state and the ground fault current is not detected when the switching unit is in an off state, the detection unit determines that the ground fault is a balanced ground fault. In a detection result in which the ground fault current is not detected when the switching unit is in an on state and the ground fault current is detected when the switching unit is in an off state, the detection unit determines that the ground fault is on the positive electrode side;
In a case where the ground fault current is detected when the switching unit is in an on state and the ground fault current is also detected when the switching unit is in an off state, the detection unit determines that the ground fault is a negative electrode side ground fault,
6. The ground fault detector according to claim 5, wherein, when the detection result shows that the ground fault current is detected when the switching unit is in an on state and the ground fault current is not detected when the switching unit is in an off state, the detection unit determines that the ground fault is a balanced ground fault.

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