JPH05219643A - Ground fault detector for ac/dc mixed power supply - Google Patents

Abstract

PURPOSE:To provide a ground fault detector for AC/DC mixed power supply comprising an AC line connected with secondary terminals of a transformer and a DC line connected through a rectifier with the AC line and employed as a control power supply for switchboard, for example, wherein a decision can be made in which of the AC and DC line a ground fault has occurred. CONSTITUTION:The ground fault detector comprises a first ground fault overcurrent relay 8 connected between a secondary neutral point (o) of a transformer 1 and a ground through a current transformer 7, and a second ground fault relay 9 connected between secondary terminals (u), (v) of the transformer 1 and an AC line 3 through a zero-phase current transformer 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground fault detecting device for an AC / DC mixed power source used as a power source for controlling a switchboard.

[0002]

2. Description of the Related Art FIG. 3 is a power supply system diagram showing a conventional example of a ground fault detection device for a mixed AC / DC power supply. In FIG.
The mixed AC / DC power supply includes a transformer 1 having a neutral point terminal o on the secondary side, an AC line 3 connected to both terminals u and v of the secondary side of the transformer 1, and an AC line 3 It comprises a DC line 5 connected via a rectifier 4. The ground fault detection device is connected to the secondary side of the current transformer 7 and the current transformer 7 whose primary side is connected via the resistor 6 between the secondary side neutral point terminal o of the transformer 1 and ground. It consists of a ground fault overcurrent relay 8. The resistor 6 is for current limiting and is provided as necessary. The ground fault overcurrent relay 8 normally has an auxiliary contact 8A that is "open" when it is "non-operation" and "closed" when it is "operation", and this auxiliary contact 8A is as shown in FIG. It is connected between the control power sources Rc and Tc via 15.

When a ground fault occurs in the AC line 3 or the DC line 5, a ground fault current flows between the secondary side neutral point terminal o of the transformer 1 and the ground, and when the ground fault current exceeds a set value, the ground fault current is exceeded. The overcurrent relay 8 operates. When the ground fault overcurrent relay 8 operates, the auxiliary contact 8A switches from "open" to "closed", and the ground fault indicator lamp 15 lights up.

[0004]

Since the above-mentioned ground fault detecting device operates regardless of whether an AC line or a DC line has a ground fault, which line of AC or DC has the ground fault. There was a problem that it could not be determined.

An object of the present invention is to solve the above-mentioned problems and to provide a ground fault detecting device capable of discriminating whether a ground fault occurs in an AC line or a DC line.

[0006]

In order to achieve the above-mentioned object, a ground fault detection device for an AC / DC mixed power supply according to the present invention is a transformer having a neutral point terminal on a secondary side, and a transformer having the neutral point terminal. AC consisting of an AC line connected to both terminals on the secondary side and a DC line connected to this AC line via a rectifier
In a DC mixed power supply, a first ground fault overcurrent relay connected between a secondary side neutral point terminal of the transformer and a ground via a current transformer, both secondary side terminals of the transformer and the AC line. And a second ground fault overcurrent relay connected between the first ground fault overcurrent relay and the first ground fault overcurrent relay,
The second ground fault overcurrent relay "operation" detects the ground fault of the AC line, and the first ground fault overcurrent relay "operation" and the second ground fault overcurrent relay "non-operation" detects the ground fault of the DC line. To do it. Furthermore, the first ground fault overcurrent relay is "inoperative"
"Open", "Operate" to "Close" auxiliary contact, the second ground fault overcurrent relay is "Inactive" from "Closed" and "Open",
Each has an auxiliary switching contact that switches between "open" and "closed" in "operation", and an auxiliary contact for the second ground fault overcurrent relay is provided to one terminal of the control power supply via the auxiliary contact for the first ground fault overcurrent relay. Connect the common contact of the switching contact and connect the other terminal of the control power supply to the "closed" contact of the "non-operation" of this auxiliary switching contact through the DC line ground fault indicator lamp to the "non-operation" of this auxiliary switching contact. Connect the "open" contacts via the AC line ground fault indicator lights.

[0007]

The ground fault detecting device for a mixed AC / DC power supply according to the present invention includes a transformer having a neutral point terminal on the secondary side, an AC line connected to both terminals of the secondary side of the transformer, and In an AC / DC mixed power supply consisting of an AC line and a DC line connected via a rectifier, a first ground fault transient connected between a secondary side neutral point terminal of the transformer and ground via a current transformer. Since a current relay and a second ground fault overcurrent relay connected between the secondary side terminals of the transformer and the AC line via a zero-phase current transformer, the AC line is grounded. When a fault occurs, a ground fault current flows between the secondary side neutral point terminal of the transformer and the ground, and the first ground fault overcurrent relay operates, and only the ground fault phase on the primary side of the zero-phase current transformer is grounded. Since the leakage current flows, the primary side of the zero-phase current transformer becomes unbalanced, and the current is output from the secondary side. The second ground fault overcurrent relay to operate is. When a ground fault occurs in the DC line, a ground fault current flows between the secondary side neutral point of the transformer and the ground as described above, and the first ground fault overcurrent relay operates, but in this case, the ground fault current flows in the rectifier. Since the secondary side terminals of the transformer supply power to both phases through the transformer, the primary side of the zero-phase current transformer is maintained in a balanced state, and no current is output from the secondary side of the second ground fault overcurrent relay. Does not work. Therefore, the ground fault of the AC line is detected by the first ground fault overcurrent relay “operation” and the second ground fault overcurrent relay “operation”, and the first ground fault overcurrent relay “operation” and the second ground fault overcurrent relay are detected. It is possible to detect the ground fault of the DC line by "inoperative". Further, the first ground fault overcurrent relay has an auxiliary contact which is "open" when "inoperative" and "closed" when "operating", and
Ground fault overcurrent relay is "inactive", "closed" and "open"
From the "operation" to "open" and "closed" auxiliary switching contacts respectively, the first terminal on one terminal of the control power supply.
The common contact of the auxiliary switching contact of the second ground fault overcurrent relay is connected through the auxiliary contact of the ground fault overcurrent relay, and the "non-operation" and "closed" contact of this auxiliary switching contact is connected to the other terminal of the control power supply. Via the DC line ground fault indicator light, and by connecting the "open" contact of this auxiliary switching contact via the AC line ground fault indicator light respectively, the first ground fault overcurrent relay "operation" , The second ground fault overcurrent relay "operation", that is, the AC line ground fault indicator light is lit by the AC line ground fault, the first ground fault overcurrent relay "operation", the second ground fault overcurrent relay "inoperative" That is, the DC line ground fault indicator light comes on due to the DC line ground fault, and the ground fault line is directly displayed.

[0008]

1 is a power supply system diagram showing an embodiment of a ground fault detection apparatus for an AC / DC mixed power supply according to the present invention. The difference from the conventional ground fault detection apparatus shown in FIG. 3 is a transformer. 1 is connected to the secondary side of this current transformer 7 and a current transformer 7 whose primary side is connected via a current limiting resistor 6 provided as necessary between the secondary side neutral point terminal o and ground. In addition to the ground fault overcurrent relay (hereinafter referred to as the first ground fault overcurrent relay) 8, a zero phase whose primary side is connected between the secondary side both terminals u and v of the transformer 1 and the AC line 3. The current transformer 2 and the second ground fault overcurrent relay 9 connected to the secondary side of the zero-phase current transformer 2 are provided. Further, the first ground fault overcurrent relay 8 is "inoperative" and "open", and the "operation" is "closed" auxiliary contact 8A, and the second ground fault overcurrent relay 9 is "inoperative" and "closed". ] And “open” to “open” and “close” in “operation”, respectively, and have auxiliary switching contacts 9A,
As shown in FIG. 2, the common contact c of the auxiliary switching contact 9A of the second ground fault overcurrent relay 9 is connected to one terminal Rc of the control power supply via the auxiliary contact 8A of the first ground fault overcurrent relay 8. This auxiliary switching contact 9A is connected to the other terminal Tc of the control power source.
DC line ground fault indicator lamp 1
"Open" by "non-operation" of this auxiliary switching contact 9A via
Contact points a are connected via the AC line ground fault indicator lamp 12, respectively.

When a ground fault occurs in the AC line 3, a ground fault current flows between the secondary side neutral point terminal o of the transformer 1 and the ground.
The ground fault overcurrent relay 8 operates and the ground fault current flows only in the ground fault phase on the primary side of the zero phase current transformer 2, so that the primary side of the zero phase current transformer 2 is in an unbalanced state and its secondary side. A current is output from the second ground fault overcurrent relay 9 to operate. When a ground fault occurs in the DC line 5, a ground fault current flows between the secondary side neutral point o of the transformer 1 and the ground similarly to the above, but the first ground fault overcurrent relay 8 operates, but this ground fault occurs. Since current is supplied to both phases from the secondary side terminals of the transformer 1 via the rectifier 4, the primary side of the zero-phase current transformer 2 is maintained in a balanced state and no current is output from the secondary side. The second ground fault overcurrent relay 9 does not operate. Therefore, the ground fault of the AC line 3 is detected by the first ground fault overcurrent relay 8 “operation” and the second ground fault overcurrent relay 9 “operation”, and the first ground fault overcurrent relay 8 “operation” and the second ground fault overcurrent relay 8 “operation” is detected. The ground fault of the DC line 5 is detected by the ground fault overcurrent relay 9 “inoperative”.

Further, the first ground fault overcurrent relay 8 is "inoperative" and "open", and the "operation" is "closed" auxiliary contact 8A, and the second ground fault overcurrent relay 9 is "inoperative". It has auxiliary switching contacts 9A for switching from "closed" and "open" to "open" and "closed" in "operation", respectively. As shown in FIG. The common contact c of the auxiliary switching contact 9A of the second ground fault overcurrent relay 9 is connected through the auxiliary contact 8A of the ground fault overcurrent relay 8, and the "non-operation" of the auxiliary switching contact 9A is connected to the other terminal Tc of the control power supply. Then, the "closed" contact b is connected via the DC line ground fault indicator lamp 13, and the "inactive""open" contact a of the auxiliary switching contact 9A is connected via the AC line ground fault indicator lamp 12, respectively.

In this way, the first ground fault overcurrent relay 8 "operation" and the second ground fault overcurrent relay 9 "operation", that is, the ground fault of the AC line 3 causes the auxiliary contact 8A to be "closed" and the auxiliary switching. Since the contact 9A between points c and a is "closed", the AC line ground fault indicator lamp 12 lights up, and the first ground fault overcurrent relay 8
"Operation", the second ground fault overcurrent relay 9 "inoperative", that is, due to the ground fault of the DC line 5, the auxiliary contact 8A is "closed" and the auxiliary switching contact 9A between c and b is "closed". The DC line ground fault indicator lamp 13 comes on, and the DC or AC line with a ground fault is directly displayed.

[0012]

With the ground fault detecting device for the AC / DC mixed power supply of the present invention, it is possible to discriminate whether the ground fault occurs in the AC line or in the DC line. Treatment can be carried out urgently.

[Brief description of drawings]

FIG. 1 is a power supply system diagram showing an embodiment of a ground fault detection device of the present invention.

FIG. 2 is a circuit diagram of an indicator light of the ground fault detection device of the present invention shown in FIG.

FIG. 3 is a power supply system diagram showing an example of a conventional ground fault detection device.

FIG. 4 is an indicator light circuit diagram of the conventional ground fault detection device shown in FIG.

[Explanation of symbols] 1 transformer 2 zero-phase current transformer 3 AC line 4 rectifier 5 DC line 7 current transformer 8 first ground fault overcurrent relay 9 second ground fault overcurrent relay u secondary side terminal (transformer 1) v Secondary terminal (of transformer 1) o Neutral point terminal (of transformer 1)

Claims (3)

[Claims] 1. A transformer having a neutral point terminal on the secondary side, an AC line connected to both terminals of the secondary side of the transformer, and a DC line connected to the AC line via a rectifier. In the AC / DC mixed power source, the first side is connected between the secondary side neutral point terminal of the transformer and the ground through a current transformer.
Ground fault overcurrent relay, and a second ground fault overcurrent relay connected between both terminals of the secondary side of the transformer and the AC line via a zero-phase current transformer. The ground fault of the AC line is detected by the fault overcurrent relay “operation” and the second ground fault overcurrent relay “operation”, and the first ground fault overcurrent relay “operation” and the second ground fault overcurrent relay “non-operation” are detected. A ground fault detection device for a mixed AC / DC power supply, characterized in that a ground fault of a DC line is detected. 2. The device according to claim 1, wherein the first ground fault overcurrent relay is "inactive", "open", and "operating" is "closed".
The second ground fault overcurrent relay has auxiliary switching contacts for switching from "closed" and "open" in "non-operation" to "open" and "closed" in "operation". The common contact of the auxiliary switching contact of the second ground fault overcurrent relay is connected to one terminal of the power supply via the auxiliary contact of the first ground fault overcurrent relay, and the "non-contact" of this auxiliary switching contact is connected to the other terminal of the control power supply. It is characterized in that the "closed" contact for "operation" is connected via the DC line ground fault indicator light, and the "open" contact for this auxiliary switching contact is connected via the AC line ground fault indicator light. Ground fault detection device for AC / DC mixed power supply. 3. A transformer having a neutral point terminal on the secondary side, an AC line connected to both terminals of the secondary side of the transformer, and a DC line connected to the AC line via a rectifier. 3. The ground fault detection device for an AC / DC mixed power supply according to claim 1, which is used for an AC / DC mixed power supply for controlling a switchboard.