Three-phase three-wire leakage current recovery circuit

Abstract

A three-phase three-wire leakage current recovery circuit according to the present invention is a circuit for recovering leakage current flowing in electrical equipment connected to the secondary side of a transformer, and comprises: a first passive element disposed between the R line of the transformer secondary side and a leakage current enclosure grounding part of the electrical equipment; a second passive element disposed between the S line of the transformer secondary side and the leakage current enclosure grounding part of the electrical equipment; and a third passive element disposed between the T line of the transformer secondary side and the leakage current enclosure grounding part of the electrical equipment, wherein the leakage current enclosure grounding part is a part of the enclosure of the electrical equipment that is not insulated, where electric leakage occurs when current flows.

Description

3-phase 3-wire leakage current recovery circuit

[0001] The present invention relates to a leakage current recovery circuit, and more particularly, to a three-phase, three-wire leakage current recovery circuit for recovering leakage current flowing in an electrical facility that does not have a three-phase, three-wire neutral line on the secondary side of a transformer to the power source side.

[0002] Electric shock is a phenomenon in which the human body reacts when the leakage current flowing from the power source through the human body to the ground exceeds a certain level.

[0003] Typically, a leakage current of 15 mA or more causes convulsions, and a current of 50 mA or more can lead to death. The most common cause of death is cardiac arrest, which occurs when the heart stops functioning due to the current flowing through the heart damaging nerves.

[0004] The risk of electric shock is related to the body's resistance when the current is applied, which is largely dependent on the condition of the skin.

[0005] When electrical equipment, such as an outlet, heater, or light, is submerged in water and a human body comes into contact with the water or the metal housing that is energized through the water, current flows from the exposed conductor of the electrical equipment through the water and the human body to the ground, which is the grounding surface.

[0006] At this time, the human body becomes very dangerous because its skin is easily wet with water and in that case, the contact resistance is extremely low.

[0007] A short circuit between power lines is a problem that occurs when the insulation between the two lines decreases, increasing electrical conductivity, causing a sudden flow of current, which can cause fire or short circuit damage to electrical equipment.

[0008] In general, the insulating properties of air are very high, so electrical insulation is maintained between two wires through air.

[0009] However, if a highly conductive fluid fills the space between the two lines due to flooding or other reasons, the current between the phases increases rapidly, causing a short circuit.

[0010] Korean Patent Publication No. 10-2023-0061805 discloses, as illustrated in FIG. 1, a three-phase, four-wire phase-to-phase current and leakage current limiting device of a submerged electrical facility is connected to a distribution line of the electrical facility, and prevents electric shock in the case of submergence of the electrical facility or other electrical facilities located nearby by being electrically connected to the electrical facility, wherein one end is provided with a three-phase line terminal (12a, 12b, 12c) electrically connected to the three-phase lines (2a, 2b, 2c) of the distribution line, and the other end is provided with an internal phase line (32a, 32b, 32c) electrically connected to the electrical facility (200) and having a phase line portion (22a, 22b, 22c) not surrounded by an insulator; One end is provided with a neutral line terminal (14a, 14b, 14c) electrically connected to the neutral line (4) of the distribution line, and the other end is provided with an internal neutral line (34a, 34b, 34c) electrically connected to an electrical facility (200) and a tubular line (26a, 26b, 26c) made of a conductive material that surrounds the phase line section (22a, 22b, 22c); One end is provided with a grounding line terminal (16a, 16b, 16c) electrically connected to a grounding line (6) of a distribution line, and the other end is electrically connected to an electrical facility (200), and is formed of an insulator and has a housing ground (28a, 28b, 28c) with a ground wire provided on the inner surface of the housing that surrounds the cylindrical line (26a, 26b, 26c) and an internal grounding line (36a, 36b, 36c) electrically connected to each other; A three-phase, four-wire interphase current and leakage current limiting device for a submerged electrical facility is disclosed, which can limit a sudden current increase of the electrical facility to prevent electric shock, and which includes an insulating tube (24a, 24b, 24c) which is respectively placed between the internal phase lines (32a, 32b, 32c) and the tubular lines (26a, 26b, 26c) and surrounds the internal phase lines (32a, 32b, 32c).

[0011] In this technology, the leakage current is limited by allowing the current flowing through the cylindrical line (26a, 26b, 26c) to flow to the ground via the internal ground line (36a, 36b, 36c) through the housing ground (28a, 28b, 28c) by combining the limited phase current and the current flowing from the electric load to the internal neutral line (34a, 34b, 34c).

[0012] However, since the housing ground is grounded to the ground of the third type, there is a resistance of approximately 100 ohms between the ground and the housing ground. Therefore, if a pedestrian touches a streetlight pole that has been grounded to the housing during flooding, there is a risk of electric shock.

[0013] In the past, when there was no neutral wire on the secondary side of a transformer, only Class 3 grounding work was performed on the load electrical equipment. Therefore, when touching the electrical equipment in normal times, even if leakage current flows in the electrical equipment, the leakage current flows to the ground, so there is no risk of electric shock. However, when touching the electrical equipment during flooding, the leakage current that should flow to the ground flows to the human body, exposing one to the risk of electric shock.

[0014] The present invention, which was devised to solve these problems, has the purpose of providing a three-phase, three-wire leakage current recovery circuit capable of recovering leakage current flowing in an electrical facility by arranging a leakage current recovery unit between the secondary side of a transformer and the electrical facility when there is no neutral line of a three-phase, three-wire system on the secondary side of the transformer.

[0015] The problems solved by the present invention are not limited to those mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the description below.

[0016] A three-phase, three-line leakage current recovery circuit according to the present invention is a circuit for recovering leakage current flowing in an electric facility connected to a secondary side of a transformer, comprising: a first passive element disposed between an R-line on the secondary side of the transformer and a leakage current enclosure grounding portion of the electric facility; a second passive element disposed between an S-line on the secondary side of the transformer and a leakage current enclosure grounding portion of the electric facility; and a third passive element disposed between a T-line on the secondary side of the transformer and a leakage current enclosure grounding portion of the electric facility, wherein the leakage current enclosure grounding portion is characterized in that it is configured to be connected to a portion of an exterior case of the electric facility that is not insulated and where leakage current occurs when current is supplied.

[0017] Preferably, the first to third passive elements are characterized by being resistors or inductors.

[0018] Preferably, the impedance values ​​of the first to third passive elements are the same.

[0019] Preferably, the power display unit further includes an LED connected in a forward direction between the secondary side of the transformer and the leakage current enclosure grounding part of the electrical equipment.

[0020] Preferably, the power display unit includes at least one of an 11th resistor and a 1st LED connected in series between the secondary R line of the transformer and the leakage current enclosure grounding part of the electrical equipment; a 12th resistor and a 2nd LED connected in series between the secondary S line of the transformer and the leakage current enclosure grounding part of the electrical equipment; and a 13th resistor and a 3rd LED connected in series between the secondary T line of the transformer and the leakage current enclosure grounding part of the electrical equipment.

[0021] According to the three-phase, three-wire leakage current recovery circuit of the present invention, when there is no neutral line of a three-phase, three-wire system on the secondary side of a transformer, a leakage current recovery unit is arranged between the secondary side of the transformer and the electrical equipment, so that the leakage current flowing in the electrical equipment can be recovered to the power supply side of the secondary side of the transformer.

[0022] In addition, according to the present invention, when an electrical facility not connected to the neutral line of a three-phase, three-wire system is submerged, even if a person touches the electrical facility, no leakage current flows to the human body, so not only does no electric shock occur, but the electrical facility can also operate normally even during submersion.

[0023] The effects of the present invention are not limited to those mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the description below.

[0024] Figure 1 is a schematic diagram of a three-phase, four-wire interphase current and leakage current limiting device of an electrical facility according to the prior art.

[0025] Figure 2 is a three-phase, three-line leakage current recovery circuit diagram according to one embodiment of the present invention, and

[0026] Figure 3 is a three-phase, three-line leakage current recovery circuit diagram according to another embodiment of the present invention.

[0027] Additional objects, features and advantages of the present invention can be more clearly understood from the following detailed description and accompanying drawings.

[0028] Before going into a detailed description of the present invention, it should be understood that the present invention can be modified in various ways and can have various embodiments, and that the examples described below and illustrated in the drawings are not intended to limit the present invention to specific embodiments, but include all modifications, equivalents, and substitutes included in the spirit and technical scope of the present invention.

[0029] In addition, when describing with reference to the attached drawings, identical components will be assigned the same reference numerals regardless of the drawing numbers, and redundant descriptions thereof will be omitted. When describing the present invention, if a detailed description of a related known technology is judged to unnecessarily obscure the gist of the present invention, such detailed description will be omitted.

[0030] The electrical equipment applied to the present invention means an electrical device or apparatus that uses a three-phase power source, and a three-phase motor will be described as an example.

[0031] FIG. 2 is a three-phase, three-line leakage current recovery circuit diagram according to one embodiment of the present invention, and FIG. 3 is a three-phase, three-line leakage current recovery circuit diagram according to another embodiment of the present invention.

[0032] A three-phase, three-line leakage current recovery circuit according to one embodiment of the present invention includes a transformer (210), a power display unit (220), a leakage current recovery unit (230), a leakage current enclosure grounding unit (240, LCG), and a motor (250).

[0033] The transformer according to the present invention is sufficient as a three-phase, three-wire transformer without a neutral wire on the secondary side. The transformer (210) according to one embodiment of the present invention is a Y-△ transformer in which the three phases on the primary side are Y-connected and the three phases on the secondary side are △-connected. In addition, as illustrated in FIG. 3, the transformer (310) according to another embodiment of the present invention is a YY transformer in which the three phases on the primary side are Y-connected and the three phases on the secondary side are Y-connected. In addition, although not illustrated, the transformer according to another embodiment of the present invention is a △-△ transformer in which the three phases on the primary side are △-connected and the three phases on the secondary side are △-connected, or a △-Y transformer in which the three phases on the primary side are △-connected and the three phases on the secondary side are Y-connected. Here, three-phase means that the voltages of each phase are vr=sinwt, vs=sin(wt-120°), and vt=sin(wt-240°).

[0034] The power display unit (220) is arranged including LEDs that are forward-connected in parallel between the three wires (RST) of the secondary side of the transformer and the leakage current enclosure grounding unit (240) of the electrical equipment (250, e.g., motor). Specifically, an eleventh resistor (R11), a first LED (LED1), and a first diode (D1) in series connection are arranged between the R line of the secondary side of the transformer and the leakage current enclosure grounding unit (240) of the motor (250). A twelfth resistor (R12), a second LED (LED2), and a second diode (D2) in series connection are arranged between the S line of the secondary side of the transformer and the leakage current enclosure grounding unit (240) of the motor (250). And, a 13th resistor (R13), a third LED (LED3), and a third diode (D3) in series connection are arranged between the secondary T line of the transformer and the leakage current enclosure grounding part (240) of the motor (250). That is, one side of the power display unit (220) is connected to the R line, the S line, and the T line, respectively, and the other side of the power display unit (220) is commonly connected to the first common node (CN1). Accordingly, when power is applied to the secondary side of the transformer, the first to third LEDs (LED1, LED2, LED3) light up. Here, the 11th to 13th resistors (R11, R12, R13) and the first to third diodes (D1, D2, D3) are responsible for protecting the first to third LEDs (LED1, LED2, LED3), respectively.

[0035] The leakage current recovery unit (230) includes passive elements (e.g., resistors or inductors) connected in parallel between the three wires (RST) of the secondary side of the transformer and the leakage current enclosure grounding unit (240) of the electrical equipment (e.g., motor). Specifically, the 21st resistor (R21) is arranged between the R line of the secondary side of the transformer and the leakage current enclosure grounding unit (240) of the motor (250). The 22nd resistor (R22) is arranged between the S line of the secondary side of the transformer and the leakage current enclosure grounding unit (240) of the motor (250). In addition, the 23rd resistor (R23) is arranged between the T line of the secondary side of the transformer and the leakage current enclosure grounding unit (240) of the motor (250). That is, one side of the 21st resistor (R21), the 22nd resistor (R22), and the 23rd resistor (R23) is connected to the R line, the S line, and the T line, respectively, and the other sides of the 21st resistor (R21), the 22nd resistor (R22), and the 23rd resistor (R23) are commonly connected to the second common node (CN2). Here, the resistance values ​​(e.g., 100 ohms) of the 21st to 23rd resistors (R21, R22, R23) must be the same. When the three-phase voltage is in a balanced state, no current flows in the second common node (CN2) toward the load (three-phase motor) or toward the power source (transformer secondary side).

[0036] According to another embodiment of the present invention, when the 21st to 23rd inductors (L21, L22, L23) are used as passive components, the inductance values ​​of the 21st to 23rd inductors (L21, L22, L23) must be the same.

[0037] The leakage current enclosure grounding part (240) is sufficiently configured to be connected to a part of the electrical equipment's enclosure that is not insulated and may cause electric shock or leakage when current is applied.

[0038] Although not shown, the three-phase motor has a third-class ground, so there is a grounding resistance of less than 100 ohms between the ground wire and the ground.

[0039] According to the present invention, by directly connecting the other side of the leakage current enclosure grounding part (240) and the leakage current recovery part (230) with a wire, the resistance value between the second common node (CN2) of the leakage current enclosure grounding part (240) and the leakage current recovery part (230) can be maintained at 0.1 ohm or less. Accordingly, when leakage current occurs in the casing of an electrical equipment, most of the leakage current flowing in the casing of the electrical equipment flows toward the leakage current recovery part (230).

[0040]

[0041] The embodiments described in this specification and the attached drawings are merely illustrative of some of the technical concepts encompassed by the present invention. Therefore, the embodiments disclosed in this specification are intended to illustrate, rather than limit, the technical concepts of the present invention. Therefore, it is self-evident that the scope of the technical concepts of the present invention is not limited by these embodiments. All modifications and specific embodiments that can be easily inferred by those skilled in the art within the scope of the technical concepts contained in the specification and drawings of the present invention should be construed as being included within the scope of the rights of the present invention.

Claims

1. In a circuit for recovering leakage current flowing in electrical equipment connected to the secondary side of a transformer, A first passive element placed between the secondary R line of the transformer and the leakage current enclosure grounding part of the electrical equipment; A second passive element placed between the secondary S line of the transformer and the leakage current enclosure grounding part of the electrical equipment; and Including a third passive element placed between the secondary T-line of the above transformer and the leakage current enclosure grounding part of the above electrical equipment, The above leakage current enclosure grounding part is configured to be connected to a part of the electrical equipment's enclosure that is not insulated and where leakage occurs when current is supplied. A three-phase, three-wire leakage current recovery circuit characterized by:

2. In claim 1, A three-phase, three-line leakage current recovery circuit, characterized in that the first to third passive components are resistors or inductors.

3. In claim 2, A three-phase, three-line leakage current recovery circuit characterized in that the impedance values ​​of the first to third passive elements are the same.

4. In claim 3, A power display unit including an LED connected in the forward direction between the secondary side of the above transformer and the leakage current enclosure grounding part of the above electrical equipment. A three-phase, three-wire leakage current recovery circuit including:

5. In claim 4, the power display unit, An 11th resistor and a 1st LED connected in series between the secondary R line of the above transformer and the leakage current enclosure grounding part of the above electrical equipment; A 12th resistor and a second LED connected in series between the secondary S line of the above transformer and the leakage current enclosure grounding part of the above electrical equipment; and A three-phase, three-line leakage current recovery circuit including at least one series-connected resistor and LED among the 13th resistor and the third LED connected in series between the secondary T-line of the transformer and the leakage current enclosure grounding part of the electrical equipment.

6. In any one of claims 1 to 5, A three-phase, three-wire leakage current recovery circuit characterized in that the secondary side of the above transformer is a three-phase, three-wire circuit without a neutral line.

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