JP2013145157A - Dc earth fault detecting device and dc earth fault detecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC earth fault detecting device capable of easily detecting earth fault generated in a DC circuit with an AC current transformer, and a DC earth fault detecting method.SOLUTION: The DC earth fault detecting device includes a ground circuit 5, and an earth fault detecting circuit 6 for detecting an earth fault current of a cut-off section 24. The ground circuit 5 has a switching part 56 to be switchably connected to a DC circuit 2. The earth fault detecting circuit 6 has an AC current transformer accommodating to a variation per unit time of current flowing the cut-off section 24. The AC current transformer is configured to detect the variation per unit time of current flowing the cut-off section 24 when a connection relationship between the ground circuit 5 and the DC circuit 2 is switched by the switching part 56.

Description

  The present invention relates to a DC ground fault detection device and a DC ground fault detection method for detecting a DC ground fault generated in a DC circuit.

  Conventionally, among load facilities such as power generation facilities and power receiving / transforming facilities, there are facilities that require a direct current control power source such as DC 24V. This control power supply is provided from, for example, a DC power supply facility equipped with a storage battery. And DC power supply equipment is connected to each load equipment via a distribution board.

  The distribution board is provided with a DC ground fault detection device that detects a ground fault current that flows due to the ground fault when a ground fault occurs. This DC ground fault detection device includes an AC power source for applying an AC voltage to each circuit, a clamp-type current transformer for detecting an AC ground fault current flowing in each circuit, and a detection by the clamp-type current transformer. A ground fault current measuring unit for measuring a current value of the ground fault current included in the AC ground fault current.

  The clamp-type current transformer includes an arc-shaped iron core, a first winding wound around the iron core and connected to an AC power source, and a ground fault current measuring unit wound around the iron core. And a second winding connected to. The clamp-type current transformer excites the iron core by applying an AC voltage to the first winding to generate an electromotive force corresponding to the current flowing in each circuit in the second winding, thereby causing a ground fault. It can be measured by a current measuring unit (see, for example, Patent Document 1).

JP 2009-168664 A

  The DC ground fault detection device described in Patent Document 1 is expensive. Therefore, if it becomes possible to detect a ground fault using an inexpensive AC current transformer, the cost for detecting a DC ground fault can be kept low. However, since the current flowing through the DC circuit is unchanged, the AC current transformer does not excite the iron core by applying an AC voltage as in the DC ground fault detection device described in Patent Document 1, DC ground fault current cannot be detected.

  Therefore, in view of such circumstances, the present invention has an object to provide a DC ground fault detection device and a DC ground fault detection method capable of easily detecting a ground fault generated in a DC circuit with an AC current transformer. To do.

  A DC ground fault detection device according to the present invention is a DC ground fault detection device that detects a ground fault current flowing in a DC circuit due to a ground fault, and a ground circuit that grounds the DC circuit, and a ground fault A ground fault detection circuit provided in each of the cutoff sections in the DC circuit that cuts off the current when generated, and detects the ground fault current of the cutoff section, wherein the ground circuit has one end grounded and the other end A switching unit connected to the DC circuit in a switchable manner, and the ground fault detection circuit responds to an amount of change per unit time of a current flowing through a blocking section provided with the ground fault detection circuit. The AC current transformer detects the amount of change per unit time of the current flowing through the cut-off section when the connection between the ground circuit and the DC circuit is switched by the switching unit. It is characterized by.

  According to such a configuration, when the switching unit of the ground circuit is switched, the connection relationship between the ground circuit and the DC circuit is switched, and the ground fault current flowing through each cutoff section changes. Since the iron core of the AC current transformer is excited by the amount of change of the ground fault current per unit time, the AC current transformer can detect the ground fault.

  According to the present invention, it is preferable that the switching unit of the ground circuit is a circuit breaker that interrupts a current flowing through the ground circuit.

  According to this configuration, the current flowing through the ground circuit can be switched by turning on and off the circuit breaker, and the AC current transformer can detect a ground fault.

  A DC ground fault detection method according to the present invention is a DC ground fault detection method for detecting a ground fault current flowing in a DC circuit due to a ground fault, and is provided in the DC circuit and the DC circuit. The DC ground fault detection device, and when the switching unit switches the connection relationship between the ground circuit and the DC circuit, per unit time of the current flowing through the block section provided with the ground fault detection circuit Is detected by an AC current transformer provided in each block section.

  According to such a configuration, when the switching unit of the ground circuit is switched, the connection relationship between the ground circuit and the DC circuit is switched, and the ground fault current flowing through each cutoff section changes. Since the iron core of the AC current transformer is excited by the amount of change of the ground fault current per unit time, the AC current transformer can detect the ground fault.

  As described above, according to the DC ground fault detection device and the DC ground fault detection method according to the present invention, the ground fault generated in the DC circuit can be easily detected by the AC current transformer. .

1 shows an overall circuit diagram of a DC ground fault detection apparatus according to a first embodiment of the present invention. (A) shows the block diagram of the ground fault determination circuit and circuit breaker control circuit of the DC ground fault detection apparatus which concerns on the same embodiment. (B) shows the table | surface showing the secondary detection value output from a detection value receiving part by the combination of the circuit selection switch of the detection value receiving part of the same ground fault determination circuit, and the said combination. The flowchart of the direct-current ground fault detection apparatus which concerns on the same embodiment is shown. The flowchart of the direct-current ground fault detection apparatus which concerns on the same embodiment is shown. The whole circuit diagram showing the flow of the ground fault current of the direct-current ground fault detection apparatus which concerns on the same embodiment is shown. The timing chart of the direct-current ground fault detection apparatus which concerns on the same embodiment is shown. The timing chart of the direct-current ground fault detection apparatus which concerns on 2nd Embodiment of this invention is shown. (A) shows the block diagram of the ground fault determination circuit and circuit breaker control circuit of the direct-current ground fault detection apparatus which concern on 3rd Embodiment of this invention. (B) shows the table | surface showing the secondary detection value output from a detection value receiving part by the combination of the circuit selection switch of the detection value receiving part of the same ground fault determination circuit, and the said combination. The timing chart of the direct-current ground fault detection apparatus which concerns on the same embodiment is shown. The whole circuit diagram of the direct-current ground fault detection apparatus which concerns on other embodiment is shown.

  A DC ground fault detection apparatus according to a first embodiment of the present invention will be described with reference to FIGS. A DC ground fault detection apparatus 1 according to the embodiment is installed in the DC circuit 2 in order to detect a ground fault current flowing in the DC circuit 2 due to the ground fault, as shown in FIG.

  The DC circuit 2 is a circuit that supplies a DC current from the DC power source 3 to one or a plurality of loads 4,... (41, 42,..., 4n; n = 1, 2, 3,. The DC power source 3 is one or a plurality of power sources. The DC power supply 3 is a power supply provided outside the DC circuit 2 as a DC power supply device and connected to the DC circuit 2. One or a plurality of loads 4 are connected to the DC circuit 2. Note that the DC power supply 3 may be connected to the storage battery and provided in the DC circuit 2. Also, the loads 4... May be provided in the DC circuit 2.

  The DC circuit 2 includes a main circuit 21A connected to the DC power source 3 and a plurality of branches provided for each load group that is a set of the loads 4,... Or specific loads 4,. .. (21B1, 21B2,..., 21Bn; n = 1, 2, 3,...). The DC circuit 2 according to this embodiment will be described by taking as an example a distribution board having a plurality of branch circuits 21B,... For distributing a DC current received from a DC power supply device to a plurality of loads 4,.

  The main circuit 21A and the branch circuit 21B,... Include a circuit breaker that interrupts the current flowing through the main circuit 21A and the branch circuit 21B,. The circuit breaker includes a circuit control circuit breaker 22 that interrupts an accident current such as a load current and a ground fault current that flows when the DC circuit 2 is operating in a steady state, and the flowing current is equal to or greater than a predetermined current value. Are provided with overcurrent circuit breakers 23,. Although the circuit control circuit breaker 22 according to the present embodiment will be described as an example of the circuit breaker MCB, it may be an air circuit breaker ACB, a vacuum circuit breaker VCB, or the like depending on the specifications of the circuit to be cut off.

  These circuit control circuit breakers 22,... Form a circuit block 24 that partitions the DC circuits 2. The interruption section 24 is a section that can be disconnected from the circuit to which the direct current is supplied by cutting off the circuit control breakers 22. That is, when the ground fault occurs, the shut-off section 24 can shut off only the sections 24,... Where the ground fault occurs by shutting off the circuit control circuit breaker 22.

  The circuit control circuit breakers 22,... Are provided corresponding to one or more loads 4,... Connected to the DC circuit 2 in order to select the loads 4,. Then, by interrupting the circuit control circuit breakers 22,..., The DC circuit 2 is formed with a circuit block 24 in which the loads 4,.

  Specifically, the circuit control circuit breaker 22 includes a first circuit breaker 22A provided in the main circuit 21A, and second circuit breakers 22B provided in the branch circuits 21B,. Then, by cutting off the first circuit breaker 22A, the main circuit 21A has a first cut-off section that cuts off the supply of current from the main circuit 21A to the branch circuits 21B,. 24A is formed. Further, by interrupting the second circuit breakers 22B,..., The loads 4 connected to the branch circuits 21B,... Provided with the second circuit breakers 22B,. ... (24B1, 24B2,..., 24Bn; n = 1, 2, 3,...) Are formed to block the supply of current to.

  The overcurrent circuit breaker 23 is an electromagnetic or bimetal overcurrent tripping element.

  As shown in FIGS. 1 and 2A, the DC ground fault detection device 1 includes a ground circuit 5 that grounds the DC circuit 2, and a ground fault detection circuit 6 that detects a ground fault current in each of the cutoff sections 24,. ,..., And ground fault detection circuit 7 for determining the cut-off section 24 where the ground fault has occurred based on detection from each of the ground fault detection circuits 6. A circuit breaker control circuit 8 for controlling the circuit control circuit breakers 22,...

  As shown in FIG. 1, the ground circuit 5 includes a ground unit 51 that grounds the DC circuit 2, and a variable unit 52 that varies a ground fault current flowing in the DC circuit 2 through the ground unit 51. .

  The grounding unit 51 also serves as a protective relay for detecting a DC ground fault for the purpose of detecting a ground fault occurring in any of the plurality of circuits 21, 22,. That is, the ground unit 51 includes a positive-side ground fault detection resistor 53p connected to the positive-side electric circuit of the main circuit 21, a negative-side ground fault detection resistor 53m connected to the negative-side electric circuit of the main circuit 21, and a positive electrode. A grounding circuit 54 for grounding the side ground fault detection resistor 53p and the negative side ground fault detection resistor 53m, and a positive side ground fault detection unit 55p for detecting a voltage Vgp between the positive side ground fault detection resistor 53p and the ground. And a negative-electrode-side ground fault detector 55m that detects the voltage Vgm between the negative-electrode-ground fault detection resistor 53m and the ground.

  The positive-side ground fault detection resistor 53p and the negative-side ground fault detection resistor 53m are set to substantially the same resistance value, and have a resistance of about 5 kΩ. The grounding circuit 54 has one end grounded and the other end connected to the DC circuit 2 via a positive-side ground fault detection resistor 53p and a negative-side ground fault detection resistor 53m. Therefore, when the DC circuit 2 has a ground fault, a ground fault current flows from the ground fault location of the DC circuit 2 through the ground circuit 54 into the DC circuit 2 to form a ground fault circuit. The positive-side ground fault detection unit 55p is a voltmeter that is connected in parallel with the positive-side ground fault detection resistor 53p and can measure the inter-terminal voltage Vgp of the positive-side ground fault detection resistor 53p. The negative-side ground fault detection unit 55m is also a voltmeter that is connected in parallel with the negative-side ground fault detection resistor 53m and can measure the inter-terminal voltage Vgm of the negative-side ground fault detection resistor 53m. The positive-side ground fault detection unit 55p and the negative-side ground fault detection unit 55m have external output terminals that can output the detected ground voltages Vgp and Vgm to the ground fault determination circuit 7. The positive-side ground fault detection unit 55p and the negative-side ground fault detection unit 55m are not limited to outputting measured values of the ground-to-ground voltages Vgp and Vgm, and the ground-to-ground voltages Vgp and Vgm are equal to or higher than a predetermined voltage value. May be configured to output a signal indicating that

  The variable unit 52 is a switching unit 56 that is provided in the grounding circuit 54 and connects the connection state between the grounding unit 51 and the main circuit 21 </ b> A of the DC circuit 2 so that the grounding circuit 5 is disconnected from the DC circuit 2. . The switching unit 56 is a third circuit breaker that blocks the current flowing through the ground circuit 5. The third circuit breaker has a breaking ability to cut off the ground fault current. The third circuit breaker is controlled by the ground fault determination circuit 7.

  The ground fault detection circuit 6 is provided in each of the cut-off sections 24 in the DC circuit 2 that cuts off the current due to the occurrence of a ground fault. The ground fault detection circuit 6 uses, as a detection value, a value proportional to the amount of change per unit time of the current flowing through the cutoff section 24,... Where the local fault detection circuit 6 is provided according to the change of the ground fault current by the variable unit 52. Output.

  The ground fault detection circuit 6 includes a first ground fault detection circuit 61 provided on the load 4,... Side of the first circuit breaker 22A of the main circuit 21A, and a second circuit breaker 22B of the branch circuit 21B,. , And a second ground fault detection circuit 62 provided on the load 4 side. The first ground fault detection circuit 61 outputs a value proportional to the amount of change per unit time of the ground fault current flowing through the first cutoff section 24A as the first primary detection value dI1A. The second ground fault detection circuit 62 uses a value proportional to the amount of change per unit time of the ground fault current flowing through the second cutoff section 24B,... As the second primary detection value dI1B (dI1B1, dI1B2,. dI1Bn; n = 1, 2, 3,.

  The ground fault detection circuits 61, 62,... Change per unit time of the ground fault current flowing through the cutoff section 24,... When the connection between the ground circuit 5 and the DC circuit 2 by the third circuit breaker is switched. Detect with an AC current transformer that responds to the volume. That is, the AC current transformer outputs a detection value proportional to the amount of change per unit time of the input current.

  The AC current transformer responds to the amount of change per unit time in the current flowing in both the positive and negative electrode circuits, so that the current that flows equally in the positive and negative electrode circuits, such as load current, etc. Is not output, and a value proportional to the amount of change per unit time of a current that is biased to one of the electrical paths, such as a ground fault current, is output as the primary detection value dI1.

  As shown in FIG. 2A, the ground fault determination circuit 7 is detected by the detection value receiving unit 71 that receives the primary detection values dI1,... From the local fault detection circuits 6,. In addition, a ground fault section (blocking section) 24g in which a ground fault has occurred is provided as the shut-off section 24 provided with the ground fault detection circuit 6 in which the maximum detected value dIMAX that is the maximum among all the primary detection values dI1,. And a determination unit 72 that determines that

  The detection value receiving unit 71 receives a first primary detection value dI1A from the first ground fault detection circuit 61 and outputs it to the determination unit 72, and each second ground fault detection circuit .., A second processing unit 74 that receives input of second primary detection values dI1B,..., Selects the second primary detection value dI1B, and outputs the second primary detection value dI1B to the first processing unit 73. .

  When the second primary detection value dI1B is input from the second processing unit 74, the first processing unit 73 adds the first primary detection value dI1A input from the first ground fault detection circuit 61 to the first primary detection value dI1A. The two primary detection values dI1B are added and output to the determination unit 72 as a secondary detection value dI2 (= dI1A + dI1B). The first processing unit 73 connects the first ground fault detection circuit 61 and the second processing unit 74 in parallel. When the second primary detection value dI1B is not input from the second processing unit 74, the first processing unit 73 uses the first primary detection value dI1A input from the first ground fault detection circuit 61 as it is. It outputs to the determination part 72 as secondary detection value dI2.

  The second processing unit 74 is provided with a circuit selection switch 75 provided between each of the second ground fault detection circuits 62,... To which the second primary detection values dI1B,. (75-1, 75-2,..., 75-n),. Each circuit selection switch 75,... Operates independently according to the control signal from the determination unit 72 in the pattern shown in FIG. The circuit selection switches 75,... Are all OFF in the initial state. In accordance with a control signal input from the determination unit 72, each circuit selection switch 75,... Is individually turned ON.

  The determination unit 72 includes a second ground fault detection circuit 62 in which the maximum detection value dI2MAX that maximizes the second detection value dI2 obtained by adding the first detection value dI1A to each of the second primary detection values dI1B is detected. Is determined as a ground fault section 24g in which a ground fault has occurred.

  The determination unit 72 selects a ground fault occurrence detection unit 76 that detects whether or not a ground fault has occurred in the DC circuit 2 and a second primary detection value dI1B that is detected from the second ground fault detection circuit 62. Detection value selection unit 77, storage unit 78 storing primary detection values dI1, detected by detection value selection unit 77, and secondary detection value dI2 detected from ground fault detection circuits 6,. A ground fault section determination unit 79 that determines the fault section 24g.

  The ground fault occurrence detection unit 76 detects the occurrence of a ground fault from the ground-to-ground voltages Vgp and Vgm input from the positive side ground fault detection unit 55p and the negative side ground fault detection unit 55m of the grounding unit 51. That is, if there is an input of the ground-to-ground voltage Vgp from the positive-side ground fault detection unit 55p, the ground fault generation detection unit 76 detects that a ground fault has occurred in the negative-side electric circuit of the DC circuit 2. Further, if there is an input of the ground-to-ground voltage Vgm from the negative side ground fault detection unit 55m, the ground fault occurrence detection unit 76 detects that a ground fault has occurred in the positive side electric circuit of the DC circuit 2. Then, when detecting that a ground fault has occurred, the ground fault occurrence detection unit 76 outputs a ground fault generation signal to the ground fault section determination unit 79.

  The detection value selection unit 77 controls the circuit selection switches 75,... Of the second processing unit 74 to cause the first processing unit 71 to output the secondary detection value dI2. The detection value selection unit 77 receives a control signal from the ground fault section determination unit 79 and receives an input from the first ground fault detection circuit 61 to the first primary detection value dI1A. Further, the detection value selection unit 77 selects a second primary detection value dI1B to be added to the first primary detection value dI1A in order to cause the second processing unit 74 to output the detection value as the secondary detection value dI2. The signal is output to the circuit selection switch 75. When the secondary detection value dI2 is input from the second processing unit 73, the detection value selection unit 77 stores the detection value selection unit 77 in the storage unit 78 and outputs it to the ground fault segment determination unit 79.

  The storage unit 78 stores the primary detection values dI1,... And the secondary detection value dI2 input from the detection value selection unit 77.

  Upon receiving an input of the ground fault occurrence signal from the ground fault occurrence detection unit 76, the ground fault section determination unit 79 outputs a switching signal to the switching unit 56 of the ground circuit 5 and corresponds to the secondary detection value dI2 to be detected. In order to select a combination of the primary detection values dI1 to be output, a detection value selection signal for selecting the corresponding second primary detection value dI1B is output to the detection value selection unit 77. The switching signal and the detection value selection signal are output in synchronization.

  The ground fault section determination unit 79 determines the ground fault section 24g from the secondary detection value dI2 from the detection value selection section 77, and outputs a circuit breaker cutoff signal to the circuit breaker control circuit 8.

  The circuit breaker control circuit 8 receives the input of the circuit breaker interruption signal from the ground fault section determination unit 79, and interrupts the circuit control circuit breakers 22A, 22B,.

  Next, a DC ground fault detection method of the DC ground fault detection apparatus 1 according to the embodiment will be described with reference to FIGS. First, as shown in FIGS. 3 to 6, when a ground fault occurs in the positive circuit of the branch circuit 21 </ b> B <b> 1, the ground fault current Ig is supplied to the negative side ground fault detection resistor via the switching unit 56 of the ground circuit 5. 53m, the DC power supply 3, the main circuit 21A, and the branch circuit 21B1. Further, in the branch circuits 21B2, ..., 21Bn, currents I2p, I2m, ..., Inp, Inm flow from the load side toward the ground fault location of the branch circuit 21B1. That is, the ground fault current Ig flows in the main circuit 21A. In the branch circuit 21B1, the ground fault current Ig, the current I1n flowing through the negative-side circuit, and the currents I2p, I2m,..., Inp, Inm flowing from the branch circuits 21B2,. The local fault detection circuits 6,... Detect these currents.

  First, the negative-side ground fault detection unit 55m detects the ground-to-ground voltage Vgm when the ground-fault current Ig flows through the negative-side ground fault detection resistor 53m of the ground circuit 5. Then, the negative-side ground fault detection unit 55m outputs the ground-to-ground voltage Vgm to the ground fault occurrence detection unit 76. The ground fault occurrence detection unit 76 receives the input of the ground-to-ground voltage Vgm and detects the occurrence of the ground fault (S1). The ground fault occurrence detection unit 76 outputs a ground fault generation signal to the ground fault segment determination unit 79 and starts the ground fault segment determination.

  The ground fault section determination unit 79 stores the secondary detection value dI2 (first primary detection value dI1A) from the first ground fault detection circuit 61 input from the first processing unit 73 in the storage unit 78 ( S2). Next, the ground fault section determination unit 79 outputs a switching signal to the switching unit 56 of the ground circuit 5 to switch the connection state with the DC circuit 2 (S3), and to the detection value selection unit 77, the detection value selection signal. Are switched, the circuit selection switches 75,... Are switched to calculate the secondary detection value dI2 output by the first processing unit 73, and the first primary detection value dI1A and the second primary detection value dI1B. Is changed (S4). The ground fault section determination unit 79 receives an input of the secondary detection value dI2 obtained by adding the second primary detection value dI1B to the first primary detection value dI1A from the first processing unit 73, and receives the secondary detection value dI1B. The detection value dI2 (first primary detection value dI1A + second primary detection value dI1B) is stored in the storage unit 78 (S5).

  The ground fault section determination unit 79 detects the second primary detection values dI1B,... From all the second ground fault detection circuits 62,..., And detects the second primary detection value dI1A as the second primary detection value dI1A. The process is repeated until the secondary detection value dI2 added with the detection value dI1B is stored in the storage unit 78 (S6).

  When the detection of all the secondary detection values dI2 is completed (YES in S6), the ground fault section determination unit 79 determines the maximum detection value dIMAX that is the maximum from the secondary detection values dI2 stored in the storage unit 78. Search is performed (S7-1 to S7-4). The maximum detection value dIMAX is the secondary detection value dI2 detected for the first time, as shown in FIG. 6 (j). Therefore, the ground fault section determination unit 79 includes the second ground fault detection circuit 62B1 in which the second primary detection value dI1B, which is the basis for calculating the secondary detection value dI2 corresponding to the maximum detection value dIMAX, is detected. The provided block section 24B1 is determined as a ground fault section 24g (S8-1 to S8-4). The ground fault section determination unit 79 outputs a circuit breaker cutoff signal that shuts off the circuit control circuit breaker 22, and blocks the ground fault section 24g (S9-1 to S9-4).

  As described above, when the switching unit 56 of the ground circuit 5 is switched, the connection relationship between the ground circuit 5 and the DC circuit 2 is switched, and the ground fault current flowing through each of the cutoff sections 24,. Since the iron core of the AC current transformer is excited by the change of the ground fault current per unit time, the AC current transformer can detect the ground fault. Further, the current flowing through the ground circuit 5 can be switched by turning on and off the circuit control circuit breakers 22..., And the AC current transformer can detect a ground fault.

  Moreover, the determination part 72 can determine the interruption | blocking division 24g where the ground fault generate | occur | produced from the secondary detection value dI2 which becomes the largest among the secondary detection values dI2 which the 1st determination part output. The determination unit 72 automatically detects a circuit in which a ground fault has occurred in order to make a determination based on the primary detection value dI1 output from each of the ground fault detection circuits 6,. be able to.

  Further, when the variable portion 56 of the ground circuit 5 is varied, the ground fault current flowing through the ground circuit 5 and the DC circuit 2 is varied, and flows through the cutoff sections 24... That can be detected by the local fault detection circuits 6. The ground fault current changes. Therefore, the local fault detection circuits 6,... Can detect a change in the current flowing through each blocking section 24,.

  Further, it is possible to determine the second cutoff section 24B where the ground fault has occurred from the second primary detection value dI1B detected by the second ground fault detection circuit 62, and detect the ground fault corresponding to each load. can do. Since the determination unit 72 determines the cut-off section 24 in which the ground fault is caused by the addition detection value obtained by adding the first primary detection value dI1A to each second primary detection value dI1B, the determination sensitivity can be increased. it can.

  Next, a DC ground fault detection apparatus according to a second embodiment of the present invention will be described with reference to FIG. The DC ground fault detection device 1 according to the present embodiment is a modification of the determination unit 72 of the DC ground fault detection device according to the first embodiment. About the structure same as the structure of the direct-current ground fault detection apparatus 1 which concerns on a form, while attaching | subjecting the same code | symbol, description is abbreviate | omitted.

  The determination unit 72 is provided in the first cutoff section 24A for each of the second primary detection values dI1B detected from the second ground fault detection circuit 62 provided in each of the second cutoff sections 24B,. The second detection value dI1B in which the secondary detection value (addition detection value) dI2 obtained by adding the first detection value dI1A detected from the first ground fault detection circuit 61 is larger than the first primary detection value dI1A is detected. The cut-off section 24B provided with the second ground fault detection circuit 62 thus determined is determined as the ground fault section 24g in which the ground fault has occurred.

  Therefore, the determination unit 72 searches for the second detection value dI1B that is larger than the first primary detection value dI1A stored in the storage unit 78, and similarly to the first embodiment, the ground fault section 24g. Can be determined. Then, as shown in FIG. 7J, the second detection value dI1B becomes the secondary detection value dI2 detected for the first time. Therefore, the ground fault section determination unit 79 detects the second primary detection value dI1B that is the basis for calculating the secondary detection value dI2 corresponding to the secondary detection value dI2 detected for the first time. The interruption section 24B provided with the ground fault detection circuit is determined as the ground fault section 24g. Note that the determination unit 72 may make a determination based on a first detection value obtained by multiplying the first primary detection value dI1A by a predetermined setting value (for example, 0.5 to 2.0). In this way, the determination sensitivity can be adjusted.

  Next, a DC ground fault detection apparatus according to a third embodiment of the present invention will be described with reference to FIGS. The DC ground fault detection device according to the present embodiment is a modification of the first processing unit 73 and the second processing unit 74 of the determination unit of the DC ground fault detection device according to the first embodiment. The first processing unit and the second processing unit will be mainly described, and the same configuration as the configuration of the DC ground fault detection device according to the first embodiment will be denoted by the same reference numeral and the description thereof will be omitted.

  When the first primary detection value dI1B is input from the second processing unit 174, the first processing unit 173 adds the first primary detection value dI1A input from the first ground fault detection circuit 61 to the first primary detection value dI1A. The primary detection value dI1B of 2 is subtracted and output to the determination unit 72 as a secondary detection value dI2 (= dI1A−dI1B).

  The second processing unit 174 is provided with a circuit selection switch 175 provided between each of the second ground fault detection circuits 62 to which the second primary detection values dI1B,... Are input and the first processing unit 173. , ... are provided. Each circuit selection switch 175,... Operates independently in accordance with a control signal from the determination unit 72.

  The determination unit 72 is provided in the first cutoff section 24A for each of the second primary detection values dI1B detected from the second ground fault detection circuit 62 provided in each of the second cutoff sections 24B,. There is provided a second ground fault detection circuit 62 in which a second detection value dI1B having a minimum second detection value dI2 obtained by subtracting the first detection value dI1A detected from the first ground fault detection circuit 61 is detected. The cut-off section 24B is determined as the ground fault section 24g in which a ground fault has occurred.

  Therefore, the determination unit 72 can determine the ground fault interval 24g as in the first embodiment by searching for the minimum detection value dIMIN that is the minimum from the secondary detection values dI2 stored in the storage unit 78. . That is, the minimum detection value dIMIN is the secondary detection value dI2 detected for the first time as shown in FIG. 9 (j). Therefore, the ground fault section determination unit 79 includes the second ground fault detection circuit 62 in which the second primary detection value dI1B, which is the basis for calculating the secondary detection value dI2 corresponding to the minimum detection value dIMIN, is detected. The provided block section 24B is determined as the ground fault section 24g.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of this invention.

  As shown in FIG. 10, the DC ground fault detection device 1 according to the first to third embodiments of the present invention is connected in parallel with a positive side ground fault detection resistor 353p and a negative side ground fault detection resistor 353m in a ground circuit. You may be comprised so that the positive electrode side capacitor | condenser 357p and the negative electrode side capacitor | condenser 357m may be provided. The positive side ground fault detection resistor 353p and the negative side ground fault detection resistor 353m, and the positive side capacitor 357p and the negative side capacitor 357m include ground circuit selection switches 358p, 358m, 359p, and 359m, respectively. 5 is configured to be separable from 5. The combination of the ground circuit selection switches 358p and 359m is selected at the same time, and the combination of the ground circuit selection switches 358m and 359p is selected at the same time. The combination of the ground circuit selection switches 358p and 359m and the combination of the ground circuit selection switches 358m and 359p are not simultaneously connected.

  The determination unit 72 determines that a ground fault has occurred when the ground-to-ground voltages Vgp and Vgm are input from either of the ground fault detection units 55p and 55m. And the determination part 72 memorize | stores the 1st primary detection value dI1A detected from the 1st ground fault detection circuit 61, when the voltage Vgp between grounds is input from the positive electrode side ground fault detection part 55p, In order to connect the positive side capacitor 357p to the DC circuit 2, the ground circuit selection switches 358m and 359p are closed and the ground circuit selection switches 358p and 359m are opened. The determination unit 72 determines that the circuit in which the ground fault has occurred and disconnects the circuit control circuit breakers 22,..., And then opens the ground circuit selection switches 358 m and 359 p to disconnect the positive-side capacitor 357 p from the DC circuit 2. To do.

  By controlling the ground circuit 5 by the determination unit 72 in this way, the value of the detection value detected by the local fault detection circuits 61, 62,... Can be amplified about twice, and the detection sensitivity can be increased. it can.

  In the DC ground fault detection device 1 according to the first to third embodiments of the present invention, the example in which the switching unit 56 of the ground circuit 5 is a circuit breaker has been described. However, the present invention is not limited to this. For example, the ground circuit may include a variable unit that applies an AC voltage to vary the ground current. By providing this variable part, the AC current transformer can detect the amount of change per unit time of the ground fault current.

  Although the DC ground fault detection apparatus 1 according to the first to third embodiments of the present invention has been described as being applied to a DC control circuit that is connected to a control power source and supplied with DC power, it is not limited thereto. It is not something. At present, in place of power feeding by AC power used in data centers, factories, general households, etc., introduction of DC power feeding has been attempted, in which DC power is fed to each electric product and operated. The DC circuit of the present invention is intended to be used for this DC power supply, and may be applied to a DC circuit constituting this DC power supply.

  DESCRIPTION OF SYMBOLS 1 ... DC ground fault detection apparatus, 2 ... DC circuit, 21A ... Main circuit, 21B ... Branch circuit, 22 ... Circuit breaker for circuit control, 22A ... First circuit breaker, 22B ... Second circuit breaker, 23 ... Overload Current breaker, 24 ... Breaking section, 24A ... First breaking section, 24B ... Second breaking section, 24g ... Ground fault section, 3 ... DC power supply, 4 ... Load, 5 ... Ground circuit, 51 ... Grounding section, 52 ... Variable portion, 53p ... Positive side ground fault detection resistor, 53m ... Negative side ground fault detection resistor, 54 ... Ground circuit, 55p ... Positive side ground fault detection unit, 55m ... Negative side ground fault detection unit, 56 ... Switching unit, 6 ... Ground fault detection circuit, 61 ... First ground fault detection circuit, 62 ... Second ground fault detection circuit, 7 ... Ground fault determination circuit, 71 ... Detection value receiving unit, 72 ... Determination unit, 73 ... 1st process part, 74 ... 2nd process part, 75 ... Circuit selection switch, 76 ... Ground fault generation | occurrence | production detection part, 77 ... Detection value selection , 78 ... Storage unit, 79 ... Ground fault section determination unit, 8 ... Circuit breaker control circuit, 173 ... First processing unit, 174 ... Second processing unit, 175 ... Circuit selection switch, 353p ... For positive side ground fault detection Resistance, 353m ... Negative side ground fault detection resistor, 357p ... Positive side capacitor, 357m ... Negative side capacitor, 358p ... Ground circuit selection switch, 358m ... Ground circuit selection switch, 359p ... Ground circuit selection switch, 359m ... Ground circuit selection Switch, dI1 ... primary detection value, dI1A ... first primary detection value, dI1B ... second primary detection value, dIMAX ... maximum detection value, dI2 ... secondary detection value, Vgp ... ground voltage, Vgm ... ground Voltage, Ig ... Ground fault current

Claims (3)

A DC ground fault detection device that detects a ground fault current flowing in a DC circuit due to a ground fault,
A grounding circuit for grounding the DC circuit, and a ground fault detection circuit that is provided in each of the shut-off sections in the DC circuit that shuts off current due to the occurrence of a ground fault, and detects the ground fault current in the shut-off section Prepared,
The ground circuit includes a switching unit that is grounded at one end and is connected to the other DC circuit so that the other end can be switched.
The ground fault detection circuit includes an alternating current transformer that responds to a change amount per unit time of a current flowing through a cutoff section provided with the ground fault detection circuit, and the alternating current transformer includes the switching unit. A DC ground fault detection device that detects the amount of change per unit time of the current flowing through the cut-off section when the connection relationship between the ground circuit and the DC circuit is switched.   The DC ground fault detection device according to claim 1, wherein the switching unit of the ground circuit is a circuit breaker that interrupts a current flowing through the ground circuit. A DC ground fault detection method for detecting a ground fault current flowing in a DC circuit due to a ground fault,
The DC circuit and the DC ground fault detection device according to claim 1 or 2 provided in the DC circuit,
When the switching unit switches the connection relationship between the ground circuit and the DC circuit, the amount of change per unit time of the current flowing through the block section provided with the ground fault detection circuit is provided in each block section. A DC ground fault detection method comprising detecting with an AC current transformer.

Images