JP2004194471A - Protector which detects ground fault inside dc machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protector detecting ground fault inside a DC machine which protector detects fault current passed through the ground wires of DC machines and is thus capable of detecting a fault on a machine-by-machine basis. <P>SOLUTION: Each DC machine is provided with a relay 5 for ground fault current detection and a signal processor 6. The relay 5 detects ground fault current passed through the ground wire of a silicon rectifier 3 and, if the detected current exceeds a preset threshold value, sends out a detection signal. Based on the detection signal from the relay 5 for ground fault current detection, the signal processor 6 opens the alternating current side and the direct current side of the silicon rectifier 3. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
INDUSTRIAL APPLICABILITY The present invention relates to a ground fault detection protection inside a DC device for detecting and protecting a ground fault inside the DC device at a minor stage in a device including a DC device and an AC device, such as a substation for a railway, for example. It concerns the device.
[0002]
[Prior art]
As a conventional ground fault detection and protection device, in order to detect a ground fault on the DC line side in a substation, the potential difference between the positive and negative poles of DC equipment (that is, between rail and ground) is collectively measured in the substation. There is a device that performs monitoring (for example, see Non-Patent Document 1).
[0003]
[Non-patent document 1]
Electric Railway Engineering (First edition, March 1995, written by Yoshifumi Mochinaga, Ace Publishing, p. 78)
[0004]
[Problems to be solved by the invention]
However, in the above-mentioned conventional ground fault detection and protection device, in order to detect a ground fault on the DC line side in the substation, the potential difference between the positive pole and the negative pole of the DC equipment (that is, between the rail and the ground) is transformed. Since monitoring is performed collectively in the office, there are the following problems.
[0005]
1. It is difficult to detect a ground fault at a minor stage.
2. It takes time to identify the location of the ground fault.
3. Even in the event of a ground fault on the AC line side, the ground fault detection and protection device may malfunction.
4. When a ground fault is detected, the DC substations are normally operated on all feeder lines, and all substations stop.
5. When a ground fault occurs, a ground fault detection and protection device operates simultaneously at a plurality of substations, and as a result, there may be a case where a feeder line fails over a wide area.
[0006]
The present invention has been made to solve the above problems, and detects an accident at a minor stage (micro ground fault) by continuously detecting a ground fault current flowing through the ground wire of the device. It is an object of the present invention to obtain a ground fault detection and protection device inside a DC device that enables the above.
[0007]
[Means for Solving the Problems]
A ground fault detection and protection device in a DC device according to the present invention detects a ground fault current flowing through a ground wire of the DC device, and sends a detection signal when the detected current exceeds a preset threshold value. A current detection relay and a signal processing device for opening an AC side and a DC side of the DC device based on a detection signal of the ground fault current detection relay are provided for each DC device unit.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
In general, a ground fault is a phenomenon in which a fault current flows from a charged portion to the ground due to a break in a high-voltage line, breakage inside a device, a decrease in the insulation level of a device, and the like. In particular, when a problem occurs inside the equipment, the fault current flows from the housing of the equipment to the ground via the ground wire. For this reason, it is possible to detect an accident at a minor stage (micro ground fault) by constantly monitoring the leakage current flowing through the ground line.
[0009]
In the present invention, at the time of a ground fault, the fault current flowing to the ground wire of each device is continuously detected by utilizing the characteristic that the fault current flows from the housing of the device to the ground via the ground wire.・ To monitor.
[0010]
Embodiment 1 FIG.
FIG. 1 is a diagram showing a ground fault detection and protection device inside a DC device according to Embodiment 1 of the present invention. As shown in FIG. 1, a silicon rectifier 3 is connected to an AC circuit breaker 1 via a rectifier transformer 2, and a DC load disconnector 4 is connected to a positive pole of the silicon rectifier 3. A ground fault current detection relay 5 is provided between the equipment housing of the silicon rectifier 3 and the ground 7. When a ground fault occurs, an AC circuit breaker is provided by a signal processing device 6 based on a detection signal of the ground fault current detection relay 5. 1 and the DC load disconnector 4 are opened.
[0011]
FIG. 2 is a diagram showing a detailed configuration of the ground fault current detection relay 5 shown in FIG. As shown in FIG. 2, the ground fault current detection relay 5 includes a DCCT 5 a for detecting a current flowing through a ground line 8 provided between the device housing 3 a and the ground 7, and a predetermined threshold value for the detected current. A current detection circuit 5b for sending a contact closing command when the current exceeds the threshold value, and a contact closing command based on the contact closing command from the current detecting circuit 5b to open the AC circuit breaker 1 and the DC load disconnecting switch 4. And a contact 5c for outputting to the signal processing device 6.
[0012]
Next, the operation of the ground fault detection and protection device inside the DC device shown in FIG. 1 will be described. When a ground fault occurs inside the silicon rectifier 3, the fault current first propagates through the equipment housing 3a in FIG. 2 and concentrates on the lowest impedance location, that is, the ground line 8, and finally the ground current. That is, it flows into the earth mat buried underground. At this time, if the fault current is detected by the DCCT 5a inside the ground fault current detection relay 5 and exceeds a threshold value (set range: several tens mA to several A) preset in the current detection circuit 5b, By closing the contact 5c, it is possible to output a signal to the outside.
[0013]
The contact signal of the contact 5c is received by the signal processing device 6 in FIG. 1 as a command to open the AC circuit breaker 1 and the DC load disconnector 4, and the signal processing device 6 determines that a ground fault has occurred. In order to disconnect the corresponding device from the system, an open command is output to the switching devices at both ends of the device, that is, the AC circuit breaker 1 and the DC load disconnector 4. As a result, the silicon rectifier 3 in which the internal ground fault has occurred can be stopped immediately without affecting other normal equipment. In this case, if the threshold value in the current detection circuit 5b shown in FIG. 2 is set to a value low enough to detect a leakage current that may occur at the time of a micro-ground fault, a value before a serious accident occurs. It is also possible to detect phenomena at a minor stage.
[0014]
The conventional ground fault detection and protection device detects the potential difference between the negative pole of the entire substation and the ground, so there is a possibility that a malfunction may occur even if a ground fault occurs on the AC equipment side. , It is possible to detect only the ground fault of the DC device where the fault has occurred without being affected by the ground fault of the AC device. In addition, with the conventional ground fault detection and protection device, it is difficult to identify the location where the accident occurred, so it was necessary to stop all of the feeder lines by opening the DC circuit breakers. In addition, it is possible to selectively disconnect a DC device or line in which a ground fault has occurred. Furthermore, in the conventional method of detecting the potential difference between the negative pole and the ground, the potential difference at the ground is the same at a plurality of adjacent substations, and the negative pole is connected by a rail. It is expected to be level. As a result, since the ground fault detection and protection device operates simultaneously in the substation where the ground fault occurred and in a plurality of adjacent substations, there was a problem that the power supply line would fail over a wide area. It is possible to prevent unnecessary unnecessary power outages.
[0015]
Embodiment 2 FIG.
FIG. 3 is a diagram showing a ground fault detection and protection device inside a DC device according to Embodiment 2 of the present invention. As shown in FIG. 3, in the second embodiment, the ground fault detection protection of the inverter 9 is performed in place of the silicon rectifier 3 of the first embodiment shown in FIG. Is the same as that of the first embodiment shown in FIG.
[0016]
That is, the ground fault current generated inside the inverter 9 is detected by the ground fault current detection relay 5, and the contact output signal from the ground fault current detection relay 5 is received by the signal processing device 6, and then the two ends of the inverter 9. The open command is output to the AC circuit breaker 1 and the DC load disconnecting switch 4 located at. As a result, the inverter 9 in which an internal accident has occurred can be stopped immediately without affecting other normal equipment.
[0017]
Embodiment 3 FIG.
FIG. 4 is a diagram showing a ground fault detection and protection device inside a DC device according to Embodiment 3 of the present invention. As shown in FIG. 4, the third embodiment is directed to a cubicle type DC circuit breaker 12 in which a plurality of circuit breakers are connected in parallel to a DC bus 11 as a DC device. The circuit breakers 12 are electrically separated by an insulating material 13 for each circuit breaker unit whose housing is connected in parallel, and ground wires 16 are individually laid. It has a separate ground fault current detection relay 14 that detects a ground fault current flowing through the wire and sends a detection signal when the detected current exceeds a preset threshold.
[0018]
In the case of a cubicle type DC circuit breaker, first, it is necessary to individually set the route of the fault current in order to realize the detection of the ground fault in each bus / DC circuit breaker. For this reason, the respective housings are electrically separated by the insulating material 13 and the ground wires 16 are separately laid. By these measures, at the time of a ground fault inside the device, the route of the fault current differs depending on the location of the fault, so that the ground fault current detection relay 14 corresponding to each fault point operates. The contact output signal of the activated ground fault current detection relay 14 is received by the signal processing device 15, and the signal processing device 15 is required to separate the relevant portion determined to have a ground fault accident from the system. An open command is output to the breaker.
[0019]
The basic release sequence is as follows.
1) An accident has occurred in the feeder line → The corresponding DC breaker is opened and protection is linked to the facing breaker.
2) An accident has occurred in the DC bus → The DC breakers of all power lines are opened.
[0020]
Therefore, according to the above-described embodiments, the following effects can be obtained.
1) An internal ground fault in a DC device (rectifier, inverter, DC breaker, etc.) covered by a metal housing can be detected for each device.
2) An internal ground fault in a DC device (rectifier, inverter, DC breaker, etc.) covered by a metal housing can be detected at a slight stage.
3) Only the ground fault of the DC device can be detected without being affected by the ground fault of the AC device.
4) DC equipment and lines in which a ground fault has occurred can be selectively disconnected without stopping all substations.
5) It is possible to prevent a wide-area power failure due to the operation of the ground fault detection relay at a plurality of substations when a ground fault accident occurs.
[0021]
【The invention's effect】
As described above, according to the present invention, a ground fault current detection relay that detects a ground fault current flowing through a ground wire of a DC device and sends a detection signal when the detected current exceeds a preset threshold value And a signal processing device for opening the AC side and the DC side of the DC device based on the detection signal of the ground fault current detection relay, provided for each DC device unit, By continuously detecting the ground fault current flowing through the ground wire, an accident can be detected at a minor stage (micro ground fault).
[Brief description of the drawings]
FIG. 1 is a diagram showing a ground fault detection and protection device inside a DC device according to Embodiment 1 of the present invention.
FIG. 2 is a diagram showing a detailed configuration of a ground fault current detection relay 5 shown in FIG.
FIG. 3 is a diagram showing a ground fault detection and protection device inside a DC device according to Embodiment 2 of the present invention.
FIG. 4 is a diagram showing a ground fault detection and protection device inside a DC device according to Embodiment 4 of the present invention.
[Explanation of symbols]
1 AC circuit breaker, 2 rectifier transformer, 3 silicon rectifier, 3a equipment housing, 4 DC load disconnector, 5 ground fault current detection relay, 5a DCCT, 5b current detection circuit, 5c contact, 6 signal processing device, 7 Ground, 8 Ground wire, 9 Inverter, 11 DC bus, 12 DC circuit breaker, 13 Insulation material, 14 Ground fault current detection relay, 15 Signal processing device.

Claims (3)

A ground fault current detection relay that detects a ground fault current flowing through the ground wire of the DC device and sends a detection signal when the detected current exceeds a preset threshold value,
A ground fault detection and protection device inside the DC equipment, wherein a signal processing device for opening the AC side and the DC side of the DC equipment based on a detection signal of the ground fault current detection relay is provided for each DC equipment unit. The ground fault detection and protection device inside a DC device according to claim 1, wherein the DC device is a silicon rectifier or an inverter. The ground fault detection and protection device inside the DC device according to claim 1,
The DC device is a cubicle-type DC circuit breaker in which a plurality of circuit breakers are connected in parallel to a DC bus,
The ground fault current detection relay detects a ground fault current in the DC bus,
The cubicle-type DC circuit breaker is electrically separated by an insulating material in units of the circuit breakers connected in parallel to the housing, and a ground wire is separately laid, and for each of the electrically separated circuit breakers. Has an individual current detection relay that detects a ground fault current flowing through a ground wire and sends a detection signal when the detected current exceeds a preset threshold value,
The signal processing device detects a ground fault in each bus and each breaker based on detection signals of the ground fault current detection relay and the individual current detection relay, and determines a corresponding portion where the ground fault has occurred. A ground fault detection and protection device inside a DC device, which is separated from a system.

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