JP2012253901A - Direct current ground fault detection device, method for detecting ground fault of direct current circuit and method for switching direct current power source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect ground fault in a plurality of direct current circuits and to switch direct current power sources uninterruptibly.SOLUTION: A direct current ground fault detection device includes: a first terminal connected to one bus bar of a positive side bus bar and a negative side bus bar of a first direct current power source; a second terminal connected to the other bus bar of the positive side bus bar and the negative side bus bar of the first direct current power source; first and second voltage detection elements connected in series between the first terminal and the second terminal; a third terminal for connecting a connection point between the first voltage detection element and the second voltage detection element to the ground; a fourth terminal connected to one bus bar of a positive side bus bar and a negative side bus bar of a second direct current power source; a capacitor for capacitively coupling the first terminal and the fourth terminal; and a determination part for determining whether or not ground fault has occurred in the first direct current circuit including the first direct current power source or the second direct current circuit including the second direct current power source on the basis of at least one of the voltage detected by the first and second voltage detection elements and the current flowing between the connection point and the third terminal.

Description

  The present invention relates to a DC ground fault detection device, a DC circuit ground fault detection method, and a DC power source switching method.

In general, a DC control circuit ground fault relay 64D (hereinafter referred to as a DC ground fault detection device) is used to detect a ground fault in a DC circuit equipped with a DC power source.
The DC ground fault detection device can detect, for example, the voltage of the positive bus and the negative bus with respect to the ground, and can detect the degree of ground fault based on how the balance of these voltages is lost. For example, in FIG. 4 of Patent Document 1, the positive side voltage and the negative side voltage are detected using voltage dividing resistors, respectively, and a DC fault is detected based on a comparison result between the differential voltage and the reference voltage. A ground fault detection device is disclosed.
The DC ground fault detection device detects, for example, a current flowing in a ground line between a connection point of two resistors connected in series between the positive bus and the negative bus and the ground, and the current The degree of ground fault can also be detected based on. For example, in FIG. 2 of Patent Document 2 and FIG. 11 of Patent Document 3, the current flowing through the grounding wire is detected using a current detection resistor or an instrument current transformer, and a ground fault is detected based on the current. A DC ground fault detection device is disclosed.
In this way, it is possible to detect a ground fault in the DC circuit based on the imbalance of the positive and negative voltages and the current flowing in the ground line.

JP-A-7-177646 JP-A-9-61484 JP 2010-187513 A

  By the way, it is necessary to renew (replace) the DC power supply in a DC circuit to which many devices such as circuit breakers installed in the power substation are connected without interruption (while maintaining the DC power supply to the device). There are many cases. In this case, in addition to a DC circuit having an existing DC power supply (hereinafter referred to as an existing circuit), a DC circuit having a new DC power supply (hereinafter referred to as a new circuit) is prepared, and once the equipment is connected. The DC power source to which the device is connected is switched while making the loop shape.

  When switching the DC power source as described above, for example, as shown in FIG. 6, when the DC ground fault detection device 1b is provided in each of the existing circuit and the new circuit, both circuits are electrically insulated (for example, several hundreds of insulation resistances). (when it is greater than or equal to kΩ), it is possible to detect ground faults in both circuits. However, if only one of the short dashed arrows AC or DF is connected in the switching process, the voltage balance between the positive side and the negative side is lost, and the DC ground fault detection device 1b of both circuits malfunctions. End up. Also, if both AC and DF are connected, the resistors 11 and 12 between the buses provided in the DC ground fault detection device 1b of both circuits are connected in parallel, and the detection sensitivity of the ground fault is reduced. There is also a possibility of malfunction.

  On the other hand, when the DC ground fault detection device 1b is not provided in the new circuit, the impedance between the new circuit and the ground becomes high, and a high ground voltage is generated by induction or the like, adversely affecting the device or causing malfunction. There is a risk that. In this case, since a ground fault in the new circuit cannot be detected, for example, a ground fault occurs in one of the positive bus and the negative bus, and the other bus is grounded. If this happens, a DC short circuit may occur, causing the wiring and equipment to burn out.

  Furthermore, in the process of sequentially switching the DC power sources to which many devices are connected, a state in which the control device and the device to be controlled are connected to different DC power sources may occur. In such a state, for example, in a state where the control device 7 is connected to the existing DC power source 3 and the control target device 8 is connected to the new DC power source 5, the control target device 8 is controlled by the control device 7. May not be possible.

  Therefore, it is not possible to switch the DC power supply without a power failure while detecting a ground fault in both the existing circuit and the new circuit.

  The main present invention that solves the above-described problems includes a first terminal connected to one of the positive bus and the negative bus of the first DC power supply, and the positive bus of the first DC power supply. Or a second terminal connected to the other of the negative buses, and first and second voltage detection elements connected in series between the first terminal and the second terminal. , A third terminal for connecting a connection point between the first voltage detection element and the second voltage detection element to the ground, and the positive bus or negative bus of the second DC power source. A fourth terminal connected to one bus, a capacitor capacitively coupling the first terminal and the fourth terminal, a voltage detected by the first and second voltage detection elements, and the Based on at least one of the currents flowing between the connection point and the third terminal A determination unit that determines whether or not a ground fault has occurred in the first DC circuit including the first DC power source or the second DC circuit including the second DC power source. This is a DC ground fault detection device.

  Another main aspect of the present invention for solving the above-described problems is that a first terminal connected to one of the positive bus and the negative bus of the first DC power source, and the first DC power source. A second terminal connected to the other of the positive bus and the negative bus, and the first and second terminals connected in series between the first terminal and the second terminal. Detected by a voltage detection element, a third terminal for connecting a connection point between the first voltage detection element and the second voltage detection element to ground, and the first and second voltage detection elements. Whether or not a ground fault has occurred in the first DC circuit including the first DC power source based on at least one of a voltage and a current flowing between the connection point and the third terminal. And a determination unit for determining, using a DC ground fault detection device having the first end Is connected to the one bus of the first DC power supply, the second terminal is connected to the other bus of the first DC power supply, and the third terminal is connected to the ground. The one of the positive bus and the negative bus of the second DC power supply is connected to the one bus of the first DC power supply via a capacitor, and the positive bus of the second DC power supply is connected. The other bus of the side bus or the negative bus is connected to the other bus of the first DC power source, and the first DC circuit or the second bus is determined based on the determination result of the determination unit. A method for detecting a ground fault in a DC circuit, comprising detecting that a ground fault has occurred in a second DC circuit including a DC power source.

  Other features of the present invention will become apparent from the accompanying drawings and the description of this specification.

  According to the present invention, it is possible to detect a ground fault in a plurality of DC circuits and switch the DC power supply without any interruption.

It is a circuit block diagram which shows the structure of the direct-current ground fault detection apparatus in one Embodiment of this invention, and the connection state of each terminal. It is a figure explaining the method of switching a DC power supply without a power failure using the DC ground-fault detection apparatus in one Embodiment of this invention. It is a figure explaining the method of switching a DC power supply without a power failure using the DC ground-fault detection apparatus in one Embodiment of this invention. It is a figure explaining the method of switching a DC power supply without a power failure using the DC ground-fault detection apparatus in one Embodiment of this invention. It is a figure explaining the method of detecting a ground fault accident in a plurality of direct current circuits using a general direct current ground fault detection device. It is a figure explaining the operation | movement of a DC ground fault detection apparatus in the case of switching a DC power supply between two DC circuits each provided with the general DC ground fault detection apparatus without a power failure.

  At least the following matters will become apparent from the description of this specification and the accompanying drawings.

=== Configuration of DC Ground Fault Detection Device ===
Hereinafter, the configuration of a DC ground fault detection apparatus according to an embodiment of the present invention will be described with reference to FIG.
The DC ground fault detection device 1a shown in FIG. 1 includes terminals 21 to 25, and includes voltage detection elements 11, 12, a resistor 13, a capacitor 14, a fuse 15, and a determination unit 16.

  The (first) voltage detection element 11 and the (second) voltage detection element 12 are resistors having an impedance of about 12 kΩ, for example, and are connected in series between the terminals 21 and 22. A connection point O between the voltage detection elements 11 and 12 is connected to the terminal 23.

  The resistor 13 is a low impedance resistor of about 5Ω, for example, and the capacitor 14 is a nonpolar capacitor of about 100 μF, for example. The resistor 13 and the capacitor 14 are connected in series between the terminals 21 and 24. Further, the fuse 15 is connected between the terminals 22 and 25. The determination unit 16 receives at least one of the voltages V1 and V2 detected by the voltage detection elements 11 and 12 and the current I flowing between the connection point O and the terminal 23, respectively.

=== Method of detecting ground fault in DC circuit ===
Hereinafter, a ground fault detection method for a DC circuit using the DC ground fault detection apparatus according to the present embodiment will be described.
FIG. 1 shows a connection state of each terminal of the DC ground fault detection device 1a when the DC ground fault detection device 1a is used to detect that a ground fault has occurred in an existing circuit or a new circuit.

  The existing circuit (first DC circuit) includes a (first) DC power supply 3, a positive bus 4 p connected to the positive electrode of the DC power supply 3, and a negative bus 4 n connected to the negative electrode of the DC power supply 3. ing. On the other hand, the new circuit (second DC circuit) includes a (second) DC power supply 5, a positive bus 6 p connected to the positive electrode of the DC power supply 5, and a negative bus 6 n connected to the negative electrode of the DC power supply 5. It has.

  FIG. 1 also shows a development connection diagram (sequence diagram) of the control device 7 and the control target device 8. In FIG. It is connected to the. The control device 7 is, for example, a control relay of a remote monitoring control device, and the control target device 8 is, for example, an operating coil of a circuit breaker controlled by the control relay.

  As shown in FIG. 1, the (first) terminal 21 is connected to the positive bus 4p (one bus) on the existing circuit side, and the (second) terminal 22 is the negative bus 4n on the existing circuit side. Connected to the other bus. The (third) terminal 23 is connected to the ground. Further, the (fourth) terminal 24 is connected to the positive bus 6p (one bus) on the new circuit side, and the (fifth) terminal 25 is the negative bus 6n (the other bus) on the new circuit side. Connected to.

  Here, the fuse 15 causes a short circuit between the existing circuit and the new circuit between the positive side bus 4p and the negative side bus 6n, or between the positive side bus 6p and the negative side bus 4n. In this case, it is provided for the purpose of cutting off the short-circuit current by separating the negative buses of both circuits. Therefore, the fuse 15 having a slightly larger interrupting current than the control current flowing through the operation of a normal device is used. Here, since the normal control current is generally about 5 A or less, the fuse 15 having, for example, a cutoff current of about 7.5 A to 10 A can be used. If the DC ground fault detection device 1a is not provided with the terminal 15 without using the fuse 15, the terminal 22 is commonly connected to the negative bus of both circuits.

  By connecting in this way, the negative buses on the existing circuit side and the new circuit side are made common and have the same potential, and the positive buses are capacitively coupled. And in the said connection state, the determination part 16 carries out a ground fault accident with an existing circuit or a new circuit based on at least one of the voltages V1 and V2 and the electric current I similarly to the general DC ground fault detection apparatus 1b. It is determined whether or not it has occurred.

  Here, when a ground fault has not occurred in both circuits, the voltage difference between the DC power supplies 3 and 5 is applied to both ends of the capacitor 14. Accordingly, as in the case where the general DC ground fault detection device 1b is connected only between the buses on the existing circuit side, the voltages V1 and V2 are balanced, and the current I does not flow. There is no misjudgment that a ground fault has occurred.

  Further, when a ground fault occurs on the positive bus 4p or the negative bus 4n on the existing circuit side, the determination unit 16 operates in the same manner as the general DC ground fault detection device 1b. It can be normally determined that this has occurred. Furthermore, even when a ground fault occurs on the negative side bus 6n on the new circuit side that is shared with the negative side bus 4n on the existing circuit side, the determination unit 16 normally determines that a ground fault has occurred. Can do.

  On the other hand, when a ground fault occurs in the positive bus 6p on the new circuit side, the positive bus 6p and the terminal 23 of the DC ground fault detector 1a are connected via the ground fault resistor Rg and the ground. Therefore, the voltage Vg corresponding to the ground fault resistance Rg is applied to the voltage detection element 12. In addition, a voltage difference between the voltage of the DC power supply 3 and the voltage Vg is applied to the voltage detection element 11. As an example, assuming that the voltages of the DC power supplies 3 and 5 are both VDC and the ground fault resistance Rg = 0, V1 = 0 and V2 = VDC. Therefore, the determination unit 16 can normally determine that a ground fault has occurred by detecting that the balance between the voltages V1 and V2 has been lost or that the current I has flowed.

  In this way, the determination unit 16 can normally determine that a ground fault has occurred regardless of whether the ground fault has occurred on either the existing circuit side or the new circuit side. There is no misjudgment when no tie-up accident has occurred. The DC ground fault detection device 1a can detect that a ground fault has occurred in the existing circuit or the new circuit based on the determination result of the determination unit 16. The ground fault detection method can be used at the time of DC power supply renewal work, and a direct current that cannot use a general DC ground fault detection device 1b as in the case where a DC power source for a device is duplicated. It can also be used in circuits.

=== DC power supply switching method ===
Hereinafter, a method for switching a DC power source using the DC ground fault detection apparatus according to the present embodiment will be described with reference to FIGS. 2 to 4 as appropriate.

  First, in FIG. 2, when the short dashed arrows AC are connected and the negative buses of both circuits are connected, A, C, negative bus 6n, fuse 15, negative bus 4n, B, A, etc. Loop connection. Then, when the connection between the ABs is disconnected in this state, as shown in FIG. 3, the control target device 8 is connected to the negative bus 6n on the new circuit side.

  Here, when the control device 7 (for example, control relay) operates, the positive side bus 4p, the control device 7, the control target device 8 (for example, the operating coil of the circuit breaker), the negative side bus 6n, the fuse from the positive electrode of the DC power supply 3 are operated. 15. A control current flows to the negative electrode of the DC power source 3 via the negative bus 4n, and the controlled device 8 can operate normally. As described above, the breaking current of the fuse 15 is larger than the control current that flows in the normal operation of the device.

  Next, in FIG. 3, when the short dashed arrow DF is connected and the positive buses of both circuits are connected, D, F, positive bus 6p, capacitor 14, resistor 13, positive bus 4p, E, A loop-like connection like D is obtained. Here, the low-impedance resistor 13 is provided for the purpose of suppressing a surge current that flows when the capacitor 14 is discharged when connected in the loop shape. Then, when the connection between the DEs is disconnected in this state, as shown in FIG. 4, both the control device 7 and the control target device 8 are connected to the DC power supply 5 on the new circuit side. The power switch is complete.

  In this way, the DC power supply can be switched without power failure while detecting a ground fault in both circuits using the DC ground fault detection device 1a. In addition, by using this switching method, it is possible to always detect a ground fault even during a DC power supply update work, and the controlled device does not become uncontrollable. It is possible to reduce equipment and personnel for preventing a ground fault.

=== Other DC Fault Detection Methods ===
In the above embodiment, a ground fault detection or switching of a DC power source is performed using the DC ground fault detection device 1a in which a resistor 13, a capacitor 14, and a fuse 15 are added to a general DC ground fault detection device 1b. However, the present invention is not limited to this. For example, as shown in FIG. 5, a general DC ground fault detector 1b is used to connect the positive buses of both circuits via a resistor 13 and a capacitor 14, and to fuse between the negative buses of both circuits. Similarly, a ground fault in both circuits can be detected by connecting via 15.

  As described above, in the DC ground fault detection device 1a, the terminal 24 connected to the positive bus 6p on the new circuit side, and the terminal 21 and the terminal 24 are connected to the common DC ground fault detection device 1b. By further including the capacitor 14 to be coupled, the determination unit 16 can normally determine that a ground fault has occurred even when a ground fault has occurred on either the existing circuit side or the new circuit side bus. In addition, no erroneous determination is made when a ground fault has not occurred in both circuits. Therefore, the DC ground fault detection device 1a can detect a ground fault in both the existing circuit and the new circuit based on the determination result of the determination unit 16.

  Further, by further providing a low-impedance resistor 13 connected in series with the capacitor 14 between the terminals 21 and 24, a surge current that flows when the positive buses of both circuits are connected in a loop shape (of the capacitor 14). Discharge current) can be suppressed.

  Further, by further including a terminal 25 connected to the negative bus 6n on the new circuit side, and a fuse 15 connected between the terminals 22 and 25, a short-circuit accident between different poles between the existing circuit and the new circuit. When this occurs, the negative buses of both circuits can be disconnected and the short circuit current can be cut off.

  If the fuse 15 is not used and the terminal 25 is not provided in the DC ground fault detector 1a, the terminals 21 and 24 are connected to the positive buses 4p and 6p, respectively, and the terminal 22 is connected to the negative bus of both circuits. By connecting in common, it is possible to detect that a ground fault has occurred in an existing circuit or a new circuit using the DC ground fault detection device 1a.

  Further, when the DC ground fault detection device 1a is provided with the terminal 25 using the fuse 15, the terminals 21 and 24 are connected to the positive buses 4p and 6p, respectively, and the terminals 22 and 25 are connected to the negative bus 4n and By connecting to 6n, it is possible to detect that a ground fault has occurred in an existing circuit or a new circuit using the DC ground fault detection device 1a.

  In addition, as described above, by using the common DC ground fault detection device 1b by sharing the negative buses on the existing circuit side and the new circuit side with the same potential and capacitively coupling between the positive buses, It is possible to detect that a ground fault has occurred in an existing circuit or a new circuit.

  Further, by connecting the positive buses of both circuits via the resistor 13 and the capacitor 14, it is possible to suppress a surge current flowing when connecting the positive buses of both circuits in a loop.

  In addition, by connecting the negative buses of both circuits via a fuse 15, in the event of a short circuit accident between different circuits between the existing circuit and the new circuit, the negative buses of both circuits are disconnected. Short circuit current can be cut off.

  Also, the DC power supply can be renewed by using the DC ground fault detection device 1a or by using the general DC ground fault detection device 1b while capacitively coupling the positive buses on the existing circuit side and the new circuit side. By doing so, it is possible to switch the DC power supply without any interruption while detecting a ground fault in both circuits. Therefore, ground faults can always be detected even during DC power supply renewal work, and the controlled equipment will not be out of control, so the restrictions during work can be relaxed and ground faults can be prevented. Equipment and personnel can be reduced.

  In addition, the said embodiment is for making an understanding of this invention easy, and is not for limiting and interpreting this invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

  In the above embodiment, a ground fault is detected in one existing circuit and one new circuit, but the present invention is not limited to this. Similarly, ground faults in three or more DC circuits can be detected by capacitively coupling the positive buses to a plurality of new circuits (second DC circuits).

  In the above embodiment, the DC ground fault detector is connected between the buses on the existing circuit side, but the present invention is not limited to this. Contrary to the above embodiment, when a DC ground fault detection device is connected between the buses on the new circuit side, a ground fault in both circuits can be detected in the same manner.

  In the above embodiment, the positive buses on the existing circuit side and the new circuit side are capacitively coupled, but the present invention is not limited to this. Contrary to the above embodiment, when the negative buses of both circuits are connected via a resistor 13 and a capacitor 14 and the positive buses of both circuits are connected via a fuse 15, both circuits are similarly connected. It is possible to detect a ground fault in

  In the above embodiment, the connection is temporarily looped in the order of the negative bus and the positive bus, but the present invention is not limited to this. Contrary to the above-described embodiment, when the connection is once looped in the order of the positive side bus and the negative side bus, the DC power supply can be similarly switched without a power failure.

1a, 1b DC ground fault detector 3, 5 DC power supply 4p, 6p Positive bus 4n, 6n Negative bus 7 Control device 8 Control target device 11, 12 Voltage detection element (resistance)
13 Resistance 14 Capacitor 15 Fuse 16 Judgment part 21-25 Terminal

Claims (9)

A first terminal connected to one of the positive bus and the negative bus of the first DC power supply;
A second terminal connected to the other of the positive and negative buses of the first DC power supply;
First and second voltage detecting elements connected in series between the first terminal and the second terminal;
A third terminal for connecting a connection point between the first voltage detection element and the second voltage detection element to the ground;
A fourth terminal connected to the one of the positive bus and the negative bus of the second DC power supply;
A capacitor that capacitively couples the first terminal and the fourth terminal;
A first DC power source including the first DC power source based on at least one of a voltage detected by the first and second voltage detection elements and a current flowing between the connection point and the third terminal; A determination unit for determining whether a ground fault has occurred in a DC circuit or a second DC circuit including the second DC power supply;
A direct-current ground fault detection device comprising:   The DC ground fault detection device according to claim 1, further comprising a resistor connected in series with the capacitor between the first terminal and the fourth terminal. A fifth terminal connected to the other bus of the positive bus and the negative bus of the second DC power supply;
A fuse connected between the second terminal and the fifth terminal;
The DC ground fault detection device according to claim 1, further comprising: Using the DC ground fault detection device according to claim 1 or 2,
Connecting the first terminal to the one bus of the first DC power supply;
Connecting the second terminal to the other bus of the first DC power source and the other bus of the second DC power source;
Connecting the third terminal to ground;
Connecting the fourth terminal to the one bus of the second DC power supply;
A DC circuit ground fault detection method for detecting that a ground fault has occurred in the first DC circuit or the second DC circuit based on a determination result of the determination unit. Using the DC ground fault detection device according to claim 3,
Connecting the first terminal to the one bus of the first DC power supply;
Connecting the second terminal to the other bus of the first DC power supply;
Connecting the third terminal to ground;
Connecting the fourth terminal to the one bus of the second DC power supply;
Connecting the fifth terminal to the other bus of the second DC power supply;
A DC circuit ground fault detection method for detecting that a ground fault has occurred in the first DC circuit or the second DC circuit based on a determination result of the determination unit. A first terminal connected to one of the positive bus and the negative bus of the first DC power supply;
A second terminal connected to the other of the positive and negative buses of the first DC power supply;
First and second voltage detecting elements connected in series between the first terminal and the second terminal;
A third terminal for connecting a connection point between the first voltage detection element and the second voltage detection element to the ground;
A first DC power source including the first DC power source based on at least one of a voltage detected by the first and second voltage detection elements and a current flowing between the connection point and the third terminal; A determination unit for determining whether a ground fault has occurred in the DC circuit;
Using a DC ground fault detection device having
Connecting the first terminal to the one bus of the first DC power supply;
Connecting the second terminal to the other bus of the first DC power supply;
Connecting the third terminal to ground;
Connecting one of the positive buses or the negative buses of the second DC power supply to the one bus of the first DC power supply via a capacitor;
Connecting the other bus of the positive and negative buses of the second DC power supply to the other bus of the first DC power supply;
A ground of a direct current circuit, wherein a ground fault is detected in the first direct current circuit or the second direct current circuit including the second direct current power source based on a determination result of the determination unit. Fault detection method.   7. The one bus of the second DC power supply is connected to the one bus of the first DC power supply via the capacitor and a resistor connected in series with the capacitor. The ground fault detection method of the DC circuit as described in 2.   8. The DC circuit ground according to claim 6, wherein the other bus of the second DC power source is connected to the other bus of the first DC power source via a fuse. Fault detection method. While detecting the occurrence of a ground fault in the first DC circuit or the second DC circuit using the ground fault detection method for a DC circuit according to any one of claims 4 to 8,
A method of switching a DC power source, wherein a connection destination of a device connected to the first DC power source is switched to the second DC power source while maintaining the supply of DC power to the device.

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