JP7013086B2 - Leakage current suppressor - Google Patents

Description

The present invention suppresses leakage current generated by the ground capacitance between a 3-phase 3-wire type electric circuit that supplies 3-phase power by grounding the secondary side of an RST 3-phase distribution transformer to class B and ground. Leakage current suppression device.

For example, the 200V system transformer of the power equipment of a general consumer adopts a transformer of Y △ connection due to cost, equipment mass, etc., and supplies three-phase power by a three-phase three-wire system. The secondary side of the Y △ connection transformer is grounded in class B on the S phase, and is provided with a leakage detection device for detecting leakage in the electric circuit (see, for example, Patent Document 1).

The leakage current of the electric circuit is generally called a zero-phase current Io, and is composed of a capacitance component leakage current Ic and a resistance component leakage current Ir. The capacitance component leakage current Ic is generated by the ground capacitance between the electric circuit and the ground, and the resistance component leakage current Ir is generated by the insulation deterioration of the electric circuit. The purpose of the earth leakage detection device is to detect the resistance component leakage current Ir that occurs when the insulation of the electric circuit deteriorates, but most of the earth leakage detection devices operate when the zero-phase current Io is equal to or higher than a predetermined value. Detects leakage.

Here, as the capacitance to ground on the secondary side of the transformer increases, the constant capacitance component leakage current Ic increases. Since the capacitance component leakage current Ic flows through the ground resistance at the B-class grounding point of the S phase, the ground potential of the S phase at the grounding point rises as the capacitance component leakage current Ic increases, but the line voltage of the RST3 phase is the capacitance. Since it is maintained constant regardless of the magnitude of the component leakage current Ic, it does not cause a great hindrance to the supply of three-phase power.

Japanese Unexamined Patent Application Publication No. 2003-232826

However, when the capacitance component leakage current Ic becomes large, the ratio of the resistance component leakage current Ir to the leakage current Io becomes small, the detection accuracy of the resistance component leakage current Ir is lowered, and the accuracy of the insulation monitoring of the electric circuit may be affected. (See, for example, FIG. 7 (b) of Patent Document 1).

In addition, there are devices in the electric circuit that operate with the potential of the grounding point as the reference voltage, and for such devices, it is necessary to stabilize the potential of the grounding point, which is the reference potential. When the capacitance component leakage current Ic flows through the ground resistance of the B-class grounding point of the S phase and the ground potential of the S phase of the grounding point rises, the reference voltage will fluctuate. It is desirable to suppress the capacitance component leakage current Ic.

Here, in the case of a 3-phase 3-wire type electric circuit in which the secondary side of the RST 3-phase distribution transformer is Y-connected and the neutral point is grounded to class B to supply 3-phase power, the 3-phase 3-wire type electric circuit is used. The leakage current generated by the capacitance to ground between the ground and the ground is 2π / 3 out of phase with the leakage current of each phase of the RST phase, so if each of the three phases is balanced, they will be mutually. As a result of canceling, the leakage current does not always flow. However, if it becomes unbalanced due to the connection of a single-phase electric circuit, leakage current may flow. Therefore, the secondary side of the RST 3-phase distribution transformer is Y-connected and grounded to class B at the neutral point for 3 phases. Even in the case of a three-phase three-wire type electric circuit that supplies power, it is desirable to suppress the capacitance component leakage current Ic.

An object of the present invention is a leakage that suppresses a capacitance component leakage current generated by a ground capacitance between an electric circuit that supplies three-phase power by grounding the secondary side of an RST 3-phase distribution transformer to class B and ground. It is to provide a current suppression device.

In the leakage current suppression device according to the first aspect of the present invention, one of the three phases in which the secondary side of the RST3 phase distribution transformer is Δ-connected or V-connected is grounded to class B to form a ground phase, and the three-phase power is generated. In a leakage current suppression device that is connected to a three-phase, three-wire type electric circuit to be supplied and suppresses a leakage current generated by the ground capacitance of the electric circuit, the two phases of the two non-grounded phases and the grounded phase are two. The line voltage of each phase is input to the primary side, the positive electrode on the secondary side is connected to the ground phase, the negative voltage on the secondary side is connected to the ground electrode to the ground, and the opposite phase of the primary side is connected to the secondary side. It is connected between the transformer that generates the voltage of the transformer, the negative electrode on the secondary side of the transformer, and the ground electrode, and simulates the ground capacitance, and together with the transformer, the leakage current generated by the ground capacitance of the electric circuit is generated. A simulated capacitor that generates a compensating current for canceling, and a protective element that is connected between the electric circuit and the transformer and cuts off the transformer from the electric circuit when the compensating current exceeding the capacity of the transformer flows. The simulated capacitor capacitance adjusting device is provided with a simulated capacitor capacitance adjusting device that automatically sets the capacitance of the simulated capacitor, and the simulated capacitor capacitance adjusting device uses the voltage of any one phase of the line voltage as a reference voltage. It is generated by the ground capacitance of the electric path based on the phase of the input unit for inputting and the potential of the grounding point of the class B grounding, and the reference voltage input by the input unit and the potential of the grounding point. An electric quantity calculation unit that calculates a compensation current for canceling the leakage current, and an adjustment operation unit that adjusts the electrostatic capacity of the simulated capacitor so that the compensation current calculated by the electric quantity calculation unit can be obtained. It is characterized by having .

The leakage current suppression device according to the second aspect of the present invention is a three-phase three-wire system in which the neutral point of the three-phase in which the secondary side of the RST 3-phase distribution transformer is Y-connected is grounded in class B to supply the three-phase power. In the leakage current suppression device connected to the electric circuit and suppressing the leakage current generated by the capacitance to ground of the electric circuit, the phase voltage between each phase of two phases of the RST3 phase and the neutral point is set to 1, respectively. With a transformer that inputs to the next side, connects the positive side of the secondary side to the neutral point, connects the negative side of the secondary side to the grounding electrode to the ground, and generates a voltage of the opposite phase of the primary side to the secondary side. , A compensation current that is connected between the negative electrode on the secondary side of the transformer and the ground electrode to simulate the ground capacitance and cancels the leakage current generated by the ground capacitance of the electric circuit together with the transformer. The simulated capacitor to be generated, the protective element connected between the electric circuit and the transformer and blocking the transformer from the electric circuit when the compensation current exceeding the capacity of the transformer flows, and the capacitance of the simulated capacitor. The simulated capacitor capacitance adjusting device is provided with a simulated capacitor capacitance adjusting device that automatically sets the capacitance, and the simulated capacitor capacitance adjusting device inputs the voltage of any one of the phase voltages as a reference voltage and is grounded in the class B. Compensation for canceling the leakage current generated by the ground capacitance of the electric circuit based on the phase of the input unit for inputting the potential of the grounding point, the reference voltage input at the input unit, and the potential of the grounding point. It is characterized by having an electric amount calculation unit for calculating a current and an adjustment operation unit for adjusting and operating the electrostatic capacity of the simulated capacitor so that the compensation current calculated by the electric amount calculation unit can be obtained .

According to the leakage current suppression device of the present invention, it is possible to suppress the capacitance component leakage current generated by the ground capacitance between the electric circuit and the ground. Therefore, the accuracy of the insulation monitoring of the electric circuit by the insulation monitoring device is not deteriorated. Further, since it is possible to suppress the leakage current of the capacitance component from flowing through the ground resistance of the class B grounding point, the voltage to ground of the class B grounding point can be maintained at about 0V. Therefore, it is possible to stabilize the reference voltage of the device operating with the potential of the grounding point as the reference voltage.

Explanatory drawing when the leakage current suppression device which concerns on 1st Embodiment of this invention is applied to the electric circuit which the secondary side of a distribution transformer is a Δ connection. Explanatory drawing when the leakage current suppression device which concerns on 1st Embodiment of this invention is applied to the electric circuit which the secondary side of a distribution transformer is Y connection. An explanatory diagram of the principle that the leakage current Ig can be canceled by the two windings (first winding and second winding) of the transformer by the phase of the leakage current Ig flowing through the ground resistance Rb. It is explanatory drawing of the selection criterion which selects the phase voltage of 2 phase of 3 phase voltage Vr, Vs, Vt by the phase of the leakage current Ig flowing through the earth resistance Rb. Explanatory drawing of compensation current If the phase of the leakage current Ig is located between the leakage current Igs of the S phase component and the leakage current Igt of the T phase component. Explanatory drawing of compensation current If the phase of the leakage current Ig is located between the leakage current Igt of the T phase component and the leakage current Igr of the R phase component. Explanatory drawing when the leakage current suppression device which concerns on 2nd Embodiment of this invention is applied to the electric circuit which the secondary side of a distribution transformer is a Δ connection. Explanatory drawing which shows an example of the electric circuit which the secondary side of the distribution transformer to which this invention is applied is a Δ connection. An explanatory diagram of how to obtain the actual leakage current Ib flowing through the grounding resistance Rb of the electric circuit of FIG. 8A using Thevenin's theorem.

Hereinafter, embodiments of the present invention will be described. Prior to the description of the embodiment of the present invention, the capacitance component leakage current generated by the ground capacitance between the three-phase three-wire electric circuit to which the present invention is applied and the ground will be described. FIG. 8 is an explanatory diagram showing an example of an electric circuit in which the secondary side of the distribution transformer to which the present invention is applied is a Δ-connected electric circuit, and FIG. FIG. 8B is a circuit diagram showing an example of a three-phase three-wire electric circuit for supplying three-phase power, and FIG. 8B is an electric quantity vector diagram.

In FIG. 8A, the secondary side of the RST 3-phase distribution transformer 11 is connected by Δ, and the S-phase on the secondary side is grounded to class B to supply 3-phase power to the load 12. An electric circuit is formed. Since the S phase on the secondary side of the distribution transformer 11 is grounded to class B, the voltage to ground of the S phase is basically 0 [V], and the voltage to ground of the other R and T phases is linear. The voltage is V. Since the ground voltage of the S phase is basically 0 [V], the leakage current does not flow through the ground capacitance Cs with the ground in the S phase, so the leakage current Igs is 0. On the other hand, since the ground voltage of the R phase is the line voltage Vrs between the R phase and the S phase, the leakage current Igr {= Vrs / (1 / jωCr)} is present in the ground capacitance Cr of the R phase with the ground. Similarly, since the ground voltage of the T phase is the line voltage Vts between the T phase and the S phase, the leakage current Igt {= Vts / (1 / jωCt) is used for the ground capacitance Ct of the T phase with the ground. )} Flows. As a result, the leakage current Ig flowing through the ground resistance Rb becomes the combined current of the leakage current Igr of the R phase and the leakage current Igt of the T phase.

As shown in FIG. 8 (b), the leakage currents Igr and Igt are currents whose phases are π / 2 ahead of the line voltage Vrs and the line voltage Vts with respect to the S phase of class B grounding, and leakage. The phase difference between the currents Igr and Igt is π / 3. Therefore, the leakage current Ig of the entire electric circuit is a vector combination of the leakage currents Igr and Igt, and the magnitude thereof is | Igr | × cos (π / 6) + | Igt | × cos (π / 6). When the three-phase voltage is in equilibrium, | Vrs | = | Vst | = | Vtr | = V.

By the way, when the leakage current Ig of the entire electric circuit flows through the ground resistance Rb, the voltage to ground of the entire electric circuit rises by the amount of the voltage drop. Then, since the voltage to ground of each phase is not the line voltage, the leakage current Igr of the R phase and the leakage current Igt of the T phase change, and the leakage current Igs of the S phase also flows and becomes non-zero. Therefore, in FIG. 8A, the leakage current Ig (= Ib) actually flowing through the ground resistance Rb will be obtained.

FIG. 9 is an explanatory diagram of how to obtain the actual leakage current Ib flowing in the ground resistance Rb of the electric circuit of FIG. 8A using Thevenin's theorem, and FIG. 9A is a transformation of the target Y △ connection. The circuit diagram of the electric circuit of the vessel, FIG. 9 (b) is a circuit diagram when the Thevenin's theorem is applied to the circuit of FIG. 9 (a), and FIG. 9 (c) is an equivalent circuit of FIG. 9 (a). ..

The open circuit voltage between the terminals of the circuit of the electric circuit of the transformer of the Y △ connection which is the object of FIG. 9A is measured. The open circuit voltage between the terminals of the circuit is V / √3 [V]. Next, the internal impedance Z seen from the terminal is considered to be short-circuited by the transformer, which is the internal power supply. If the capacitances Cr, Cs, and Ct of the RST phase electric circuit are equal to C, then Z = Rb + (1 / j3ωC) [Ω]. The circuit current i that flows when the terminals are short-circuited can be obtained by the following equation (1) from Thevenin's theorem.

i = (V / √3) / {Rb + (1 / j3ωC)} ... (1)
The circuit current i is a leakage current Ib flowing through the ground resistance Rb, and the leakage current Ib is represented by the equation (2).

Ib = (V / √3) / {Rb + (1 / j3ωC)} ... (2)
This leakage current Ib increases as the maximum capacitance to ground increases. As described above, in the three-phase three-wire type electric circuit, the leakage current Ib always flows in the electric circuit due to the capacitance to ground.

Here, in the single-phase three-wire type electric circuit instead of the three-phase three-wire type, the power supplies of the R phase and the T phase in which the voltage to the ground is generated are in opposite phases, and a leakage current is generated with the same degree of capacitance to the ground. However, since the phase of the leakage current is different by π, the constant leakage current flowing through the class B is canceled and the constant leakage current does not flow. Further, in a three-phase four-wire electric circuit in which the secondary side is Y-connected, a leakage current is generated in each phase of the RST phase with the neutral wire as the N phase with respect to the ground capacitance with respect to the ground, but in the RST phase. Since the phase of the leakage current of each phase is shifted by 2π / 3, they cancel each other and the leakage current does not always flow.

In a three-phase three-wire type electric circuit in which the secondary side of the distribution transformer is connected with Δ, the leakage current due to the capacitance to ground is not canceled. Therefore, if the currents having the opposite phases can be generated for the R phase and the T phase, which are the main components of the leakage current, the leakage current can be canceled, so that the leakage current is always suppressed. In the embodiment of the present invention, the leakage current Ib is canceled, and as a result, the leakage current Ib is constantly stopped.
On the other hand, in the case of an electric circuit in which the secondary side is a Y-connected three-phase three-wire system and the neutral point is grounded, leakage current may flow if it becomes unbalanced due to the connection of a single-phase electric circuit. In the embodiment of the present invention, this leakage current Ib is also canceled, and as a result, the leakage current Ib is constantly stopped.

FIG. 1 is an explanatory diagram when the leakage current suppression device according to the first embodiment of the present invention is applied to an electric circuit in which the secondary side of the distribution transformer is connected to Δ, and FIG. 1A is an explanatory diagram of the leakage current suppression device in the electric circuit. 1 (b) is a configuration diagram when the above is connected, and FIG. 1 (b) is an electric quantity vector diagram of an electric circuit. In FIG. 1A, the electric circuit is the same as the electric circuit shown in FIG. 8A, the secondary side of the RST3 phase distribution transformer 11 is connected by Δ, and the S phase on the secondary side is grounded to class B. This is a three-phase three-wire electric circuit that supplies three-phase power to the load 12.

As in the case of FIG. 8A, the leakage current due to the capacitance to ground flowing in the electric circuit is the leakage current Igr of the R phase and the leakage current Igt of the T phase, and the leakage current Ig flowing through the ground resistance Rb. Is the combined current of the leakage current Igr of the R phase and the leakage current Igt of the T phase. The leakage current Ib that actually flows through the ground resistance Rb is represented by the equation (2) as described above. Therefore, in the first embodiment of the present invention, the leakage current suppression device 13 that generates the compensation current Ifr of the R phase component and the compensation current Ift of the T phase component that cancel the leakage current Igr of the R phase and the leakage current Igt of the T phase. Is connected to the electric circuit, and the leakage current Ib that actually flows through the ground resistance Rb is suppressed.

The leakage current suppression device 13 includes a transformer 14, a simulated capacitor 15r, 15t, a grounding electrode 16, and a protective element 17. The transformer 14 has a first winding portion 18r and a second winding portion 18t, and the first winding portion 18r is a winding that generates a voltage having a phase opposite to the line voltage Vrs, and the second winding portion. 18t is a winding that generates a line voltage Vts antiphase voltage. A line voltage Vrs between the S phase of the grounded phase and the R phase of the non-grounded phase is applied to the primary side of the first winding portion 18r, and the positive electrode on the secondary side is connected to the S phase of the grounded phase. The negative electrode on the next side is connected to the grounding electrode 16 to the ground. Similarly, the line voltage Vts between the S phase of the grounded phase and the T phase of the non-grounded phase is applied to the primary side of the second winding portion 18t, and the positive electrode on the secondary side is connected to the S phase of the grounded phase. The negative electrode on the secondary side is connected to the grounding electrode 16 to the ground.

Further, a simulated capacitor 15r is connected to the negative electrode on the secondary side of the first winding portion 18r. The simulated capacitor 15r simulates the ground capacitance Cr of the electric circuit, and together with the first winding portion 18r of the transformer 14, generates a compensating current Ifr for canceling the leakage current Igr generated by the ground capacitance Cr of the electric circuit. It is something that makes you. Similarly, a simulated capacitor 15t is connected to the negative electrode on the secondary side of the second winding portion 18t. The simulated capacitor 15t simulates the ground capacitance Ct of the electric circuit, and together with the second winding portion 18t of the transformer 14, generates a compensation current Ift for canceling the leakage current Igt generated by the ground capacitance Ct of the electric circuit. It is something that makes you.

The protective element 17 is connected between the electric circuit and the transformer 14, and cuts off the transformer 14 from the electric circuit when the compensation currents Ifr and Ift exceeding the capacities of the first winding portion 18r and the second winding portion 18t of the transformer 14 flow. Such as a switch or a fuse.

Here, the simulated capacitors 15r and 15t are switching capacitors. The switching capacitor has, for example, a plurality of capacitors having different capacitances, and the plurality of capacitors are switched and selected so that a desired capacitance can be obtained. With this switching capacitor, the capacitance to ground of the electric circuit Cr and Ct are adjusted. This is done by adjusting the potential of the grounding resistance Rb at the resistance grounding point of the S phase to be 0V.

As shown in FIG. 1, as in the case of FIG. 8A, a leakage current Igr flows through the electric circuit and the ground capacitance Cr with the ground of the R phase, and similarly, the ground with the ground of the T phase. Leakage current Igt flows through the capacitance Ct. As a result, the leakage current Ig flowing through the ground resistance Rb becomes the combined current Ig (= Igr + Igt) of the leakage current Igr of the R phase and the leakage current Igt of the T phase.

On the other hand, since the leakage current suppression device 13 is connected via the protective element 17, the compensation currents Ifr and Ift flow from the secondary side of the transformer 14. That is, the compensation current Ifr of the R phase component is the positive electrode on the secondary side of the first winding portion 18r → the S phase which is the grounding phase → the grounding resistance Rb → the grounding electrode 16 → the simulated capacitor 15r → the first winding portion 18r. It flows to the negative electrode on the secondary side of. Similarly, the compensation current Ift of the T phase component is the positive electrode on the secondary side of the second winding portion 18t → the S phase which is the grounding phase → the grounding resistance Rb → the grounding electrode 16 → the simulated capacitor 15t → the second winding portion. It flows to the negative electrode on the secondary side of 18t. As a result, the compensating current If flowing through the ground resistance Rb becomes the combined current If (= Ifr + Ift) of the compensating current Ifr of the R phase component and the compensating current Ift of the T phase component.

The compensation current If flowing through the ground resistance Rb is opposite to the leakage current Ig flowing through the ground resistance Rb. This is because the transformer 14 generates a voltage having a phase opposite to the line voltage Vrs and Vts on the secondary side. As shown in FIG. 8B, the compensation current Ifr of the R phase component is the opposite phase (phase shifted by π) from the leakage current Igr of the R phase, and the compensation current Ift of the T phase component is the leakage current of the R phase. It is the opposite phase to Igt (phase shifted by π). Therefore, the combined current Ifr (= Ifr + Ift) of the compensation current Ifr of the R phase component and the compensation current Ift of the T phase component causes the combined current Ig (= Igr + Igt) of the leakage current Igr of the R phase and the leakage current Igt of the T phase. Is offset.

In this way, since the leakage current suppression device 13 generates the compensation current If of the opposite phase of the RT phase, which is the main component of the leakage current Ig in the three-phase three-wire system, the constant leakage current of the electric circuit is suppressed. As a result, the accuracy of the insulation monitoring of the electric circuit by the insulation monitoring device is not deteriorated. Further, since the ground voltage of the class B grounding point can be maintained at about 0V, the reference voltage of the device operating with the potential of the grounding point as the reference voltage can be stabilized. In the above description, the case where the secondary side of the distribution transformer has a Δ connection has been described, but the same can be applied to the case where the secondary side of the distribution transformer has a V connection.

Next, FIG. 2 is an explanatory diagram when the leakage current suppression device according to the first embodiment of the present invention is applied to an electric circuit in which the secondary side of the distribution transformer is connected to Y. Since the leakage current suppression device has the same configuration as that shown in FIG. 1, the same elements as those in FIG. 1 are designated by the same reference numerals, and duplicate description will be omitted.

The electric circuit of FIG. 2 is a three-phase three-wire system in which the secondary side of the RST 3-phase distribution transformer 11 is Y-connected, the neutral point on the secondary side is grounded to class B, and the three-phase power is supplied to the load 12. It is an electric circuit. Further, since the neutral point of the RST3 phase is grounded, the voltage to ground of the electric circuit of the RST3 phase is the phase voltage.

Here, the leakage current Ig flowing through the ground capacitance Cr, Cs, and Ct of the electric circuit whose secondary side of the distribution transformer shown in FIG. 2 is Y-connected is the leakage current flowing through the ground capacitance Cr with the ground of the R phase. Igr, the leakage current Igs flowing in the ground capacitance Cs with the ground of the S phase, and the leakage current Igt flowing in the ground capacitance Ct with the ground of the T phase. Therefore, the leakage current Ig flowing through the ground resistance Rb is a combined current of these, and is represented by Ig = Igr + Igs + Igt. From this, originally, in order to cancel the leakage current Igr of the R phase, the leakage current Igs of the S phase, and the leakage current Igt of the T phase, the transformer 14 generates a voltage having a phase opposite to the phase voltage Vr. The three windings of the winding portion 18r, the second winding portion 18s that generates a voltage opposite to the phase voltage Vs, and the third winding portion 18t that generates a voltage opposite to the phase voltage Vt. is necessary.

However, in the first embodiment of the present invention, the compensation current If for canceling the leakage current Ig (= Igr + Igs + Igt) is generated in the two windings (first winding 18a and first winding 18b). I have to. This is because the leakage current Ig (= Igr + Igs + Igt) can be offset by the two windings (first winding 18a and first winding 18b) depending on the phase of the leakage current Ig flowing through the ground resistance Rb.

Along with this, in FIG. 2, the phase voltage input to the two windings (first winding 18a and first winding 18b) of the transformer 14 is two of the three-phase phase voltages Vr, Vs, and Vt. Since the phase voltage of the phase is sufficient, the phase voltage of the two phases is input by selecting the phase voltage of the two phases from each phase of the RST phase and sandwiching the clamp 19 in the electric circuit. Note that FIG. 2 shows a case where two phases, a phase voltage Vr and a phase voltage Vs, are selected.

FIG. 3 is an explanatory diagram of the principle that the leakage current Ig (= Igr + Igs + Igt) can be canceled by the two windings (first winding 18a and second winding 18b) depending on the phase of the leakage current Ig flowing through the ground resistance Rb. be. FIG. 3A is a phase voltage vector diagram of the RST3 phase in which the secondary side of the distribution transformer is Y-connected. Now, as the leakage current Ig, as shown in FIG. 3B, the leakage current Igr of the R phase component is shown. It is assumed that the leakage current Igs of the S phase component and the leakage current Igt of the T phase component flow. The leakage current Igr of the R phase component advances π / 2 with respect to the phase voltage Vr, the leakage current Igs of the S phase component advances π / 2 with respect to the phase voltage Vs, and the leakage current Igt of the T phase component becomes the phase voltage Vt. On the other hand, it is π / 2 advance. As shown in FIG. 3C, the leakage current Ig is a combined current of the leakage currents Igr, Igs, and Igt of each phase component, and is a leakage current Ig flowing through the ground resistance Rb at the neutral point.

As shown in FIG. 3D, the phase of the leakage current Ig is located between the leakage current Igr of the R phase component and the leakage current Igs of the S phase component. Therefore, as shown in FIG. 3E, this leakage current Ig can be represented by the leakage current Igr of the R phase component and the leakage current Igs1 of the S phase component. In FIG. 3 (e), the leakage current Igs of the R phase component is left as it is, and the leakage current Igs of the S phase component is changed to Igs1. This is to add the leakage current Igt of the T phase component.

As described above, when the phase of the leakage current Ig is located between the leakage current Igr of the R phase component and the leakage current Igs of the S phase component, the combined current of the leakage currents Igr, Igs, and Igt of each phase component is used. A certain leakage current Ig can be represented by Ig (= Igr + Igs1), and the leakage current suppression device 13 generates a compensation current If (= Ifr + Ifs) for offsetting this Ig (= Igr + Igs1). In that case, the phase voltage input to the two windings (first winding 18a and first winding 18b) of the transformer 14 is the two phases of the phase voltage Vr and the phase voltage Vs. As a result, the transformer 14 can cancel the leakage current Ig with two windings (first winding and second winding) without preparing three windings.

FIG. 4 is an explanatory diagram of a selection criterion for selecting the phase voltage of two phases out of the three phase phases Vr, Vs, and Vt according to the phase of the leakage current Ig flowing through the ground resistance Rb. In FIG. 4, in the region A, the phase of the leakage current Ig is located between the leakage current Igr of the R phase component and the leakage current Igs of the S phase component. In region B, the phase of the leakage current Ig is located between the leakage current Igs of the S phase component and the leakage current Igt of the T phase component. In region C, the phase of the leakage current Ig is located between the leakage current Igt of the T-phase component and the leakage current Igr of the R-phase component.

In the region A, as described above, the leakage current Ig can be represented by the leakage current Igr of the R phase component and the leakage current Igs of the S phase component, and the two windings of the transformer 14 (first winding 18a and). The phase voltage input to the first winding 18b) is two phases, a phase voltage Vr and a phase voltage Vs.

In region B, the leakage current Ig can be represented by the leakage current Igs of the S phase component and the leakage current Igt1 of the T phase component, and the two windings of the transformer 14 (first winding 18a and first winding 18b). The phase voltage input to) is two phases, a phase voltage Vs and a phase voltage Vt.
FIG. 5 is an explanatory diagram of the compensation current If where the phase of the leakage current Ig is located between the leakage current Igs of the S phase component and the leakage current Igt of the T phase component.

As shown in FIG. 5A, the phase of the leakage current Ig is located between the leakage current Igs of the S phase component and the leakage current Igt of the T phase component. Therefore, as shown in FIG. 5B, this leakage current Ig can be represented by the leakage current Igs of the S phase component and the leakage current Igt1 of the T phase component. In FIG. 5B, the leakage current Igs of the S phase component is left as it is, and the leakage current Igt of the T phase component is changed to Igt1. This is to add the leakage current Igr of the R phase component.

As described above, when the phase of the leakage current Ig is located between the leakage current Igs of the S phase component and the leakage current Igt of the T phase component, the combined current of the leakage currents Igr, Igs, and Igt of each phase component is used. A certain leakage current Ig can be represented by Ig (= Igs + Igt1), and the leakage current suppression device 13 generates a compensation current If (= Ifs + Ift) for offsetting this Ig (= Igs + Igt1). In that case, the phase voltage input to the two windings (first winding 18a and first winding 18b) of the transformer 14 is two phases of the phase voltage Vs and the phase voltage Vt. As a result, the transformer 14 can cancel the leakage current Ig with two windings (first winding and second winding) without preparing three windings.

In region C, the leakage current Ig can be represented by the leakage current Igt of the T-phase component and the leakage current Igr1 of the R-phase component, and the two windings of the transformer 14 (first winding 18a and first winding 18b). The phase voltage input to) is two phases, a phase voltage Vt and a phase voltage Vr. FIG. 6 is an explanatory diagram of the compensation current If where the phase of the leakage current Ig is located between the leakage current Igt of the T phase component and the leakage current Igr of the R phase component.

As shown in FIG. 6A, the phase of the leakage current Ig is located between the leakage current Igt of the T-phase component and the leakage current Igr of the R-phase component. Therefore, as shown in FIG. 6B, this leakage current Ig can be represented by the leakage current Igt of the T-phase component and the leakage current Igr1 of the R-phase component. In FIG. 6B, the leakage current Igt of the T-phase component is left as it is, and the leakage current Igr of the R-phase component is changed to Igr1. This is to add the leakage current Igs of the S phase component.

As described above, when the phase of the leakage current Ig is located between the leakage current Igt of the T phase component and the leakage current Igr of the R phase component, the combined current of the leakage currents Igr, Igs, and Igt of each phase component is used. A certain leakage current Ig can be represented by Ig (= Igt + Igr1), and the leakage current suppression device 13 generates a compensation current If (= Ift + Ifr) for offsetting this Ig (= Igt + Igr1). In that case, the phase voltage input to the two windings (first winding 18a and first winding 18b) of the transformer 14 is two phases of the phase voltage Vt and the phase voltage Vr. As a result, the transformer 14 can cancel the leakage current Ig with two windings (first winding and second winding) without preparing three windings.

Next, a case where the phase of the leakage current Ig is located between the leakage current Igr of the R phase component and the leakage current Igs of the S phase component will be described with reference to FIG. The phase voltage Vr of the R phase is applied to the primary side of the first winding portion 18a of the transformer 14, the positive electrode on the secondary side is connected to the neutral point to which the ground resistance Rb is connected, and the negative electrode on the secondary side. Is connected to the grounding electrode 16 to the ground. As a result, the first winding portion 18a generates a voltage having a phase opposite to the phase voltage Vr. Further, the phase voltage Vs of the S phase is applied to the primary side of the second winding portion 18b, the positive electrode on the secondary side is connected to the neutral point to which the ground resistance Rb is connected, and the negative electrode on the secondary side is It is connected to the grounding electrode 16 to the ground. As a result, the second winding portion 18b generates a voltage having a phase opposite to the line voltage Vs.

Further, a simulated capacitor 15a is connected to the negative electrode on the secondary side of the first winding portion 18a. The simulated capacitor 15a simulates the ground capacitance Cr of the electric circuit, and generates the R phase component Ifr of the compensation current If together with the first winding portion 18a of the transformer 14. Similarly, a simulated capacitor 15b is connected to the negative electrode on the secondary side of the second winding portion 18b. The simulated capacitor 15b simulates the ground capacitance Cs of the electric circuit, and generates the S-phase component Ifs of the compensation current If together with the second winding portion 18b of the transformer 14.

The protective element 17 is connected between the electric circuit and the transformer 14, and cuts off the transformer 14 from the electric circuit when the compensation currents Ifr and Ifs exceeding the capacities of the first winding portion 18a and the second winding portion 18b of the transformer 14 flow. Such as a switch or a fuse.

As shown in FIG. 2, a leakage current Igr flows through the ground capacitance Cr of the R phase with the ground, and a leakage current Igs flows through the ground capacitance Cs of the S phase with the ground, and the T phase. A leakage current Igt flows through the ground capacitance Ct with the ground. As a result, the leakage current Ig flowing through the ground resistance Rb becomes the combined current Ig (= Igr + Igs + Igt).

On the other hand, since the leakage current suppression device 13 is connected via the protective element 17, the compensation currents Ifr and Ifs flow from the secondary side of the transformer 14. That is, the compensation current Ifr of the R phase component is the positive electrode on the secondary side of the first winding portion 18a → ground resistance Rb → neutral point → ground electrode 16 → simulation capacitor 15a → secondary of the first winding portion 18a. It flows to the negative electrode on the side. Similarly, the compensation current Ifs of the S phase component is 2 of the positive electrode on the secondary side of the second winding portion 18b → ground resistance Rb → neutral point → ground electrode 16 → simulation capacitor 15b → second winding portion 18b. It flows to the negative electrode on the next side. As a result, the compensating current If flowing through the ground resistance Rb becomes the combined current If (= Ifr + Ifs) of the compensating current Ifr of the R phase component and the compensating current Ifs of the S phase component.

Next, the leakage current suppression device according to the second embodiment of the present invention will be described. FIG. 7 is an explanatory diagram when the leakage current suppression device according to the second embodiment of the present invention is applied to an electric circuit in which the secondary side of the distribution transformer is connected with Δ.

This second embodiment is provided with a simulated capacitor capacitance adjusting device that automatically sets the capacitance of the simulated capacitor with respect to the first embodiment shown in FIG. 1. The same elements as those in FIG. 1 are designated by the same reference numerals, and duplicate description will be omitted. As described above, the simulation capacitor 15 uses a switching capacitor. The simulated capacitor 15 is composed of, for example, a plurality of capacitors of 0.01 μF, 0.1 μF, and 1 μF, and these plurality of capacitors are selected so that a desired capacitance can be obtained.

As shown in FIG. 7, the simulated capacitor capacitance adjusting device 20 has an input unit 21, an electric energy calculation unit 22, and an adjusting operation unit 23. The input unit 21 inputs a one-phase voltage, which is a three-phase line voltage, as a reference voltage. In FIG. 7, the line voltage Vrs is input as a reference voltage. Further, the potential Vb of the grounding point of the class B grounding is input. In FIG. 7, since the negative electrode on the primary side of the first winding portion 18r and the second winding portion 18t of the transformer 14 is connected to the ground phase (S phase), the first winding portion 18r of the transformer 14 and the negative electrode are connected to the ground phase (S phase). The potential Vb at the grounding point is input from the negative electrode on the primary side of the second winding portion 18t. Further, since the potential Vb at the grounding point is based on the ground potential, the potential of the grounding electrode 16 is input as the ground potential.

The electric energy calculation unit 22 calculates a compensation current If for canceling the leakage current generated by the ground capacitance of the electric circuit based on the phase of the reference voltage Vrs input by the input unit 21 and the potential Vb at the grounding point. ..

Since the leakage current Ig is the current flowing through the ground resistance Rb, the potential Vb at the ground point is in phase with the leakage current Ig. Therefore, the electric energy calculation unit 22 sets the phase between the reference voltage Vrs and the potential Vb at the grounding point as the phase between the leakage current Ig and the reference voltage Vrs. Further, the magnitude of the leakage current Ig can be obtained by Ig = Vr / Rb. Since the compensation current If is in the opposite direction to the leakage current Ig, it is obtained as a phase deviated by π from the leakage current Ig. Further, the magnitude of the compensation current If is the same as the magnitude of the leakage current Ig.

The adjustment operation unit 23 adjusts the capacitance of the simulated capacitor so that the compensation current If calculated by the electric energy calculation unit 22 can be obtained. In this case, the capacitor of the simulation capacitor composed of a plurality of capacitors is selected so that the potential Vb at the grounding point becomes 0V. A capacitor is used when the potential Vb at the grounding point is minimized. In the second embodiment, since the simulated capacitor capacitance adjusting device 20 is provided, the capacitance of the simulated capacitor can be easily set so that the potential Vb at the grounding point becomes 0 V.

In the above explanation, the case where the secondary side of the distribution transformer is applied to the electric circuit of the Δ connection has been described, but the secondary side of the distribution transformer can also be applied to the electric circuit of the V connection, and the distribution transformer shown in FIG. The secondary side of the vessel can also be applied to a Y-connected electric circuit. When the secondary side is applied to the Y-connected electric circuit, the phase voltage is input instead of the line voltage.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

11 ... Distribution transformer, 12 ... Load, 13 ... Leakage current suppression device, 14 ... Transformer, 15 ... Simulation capacitor, 16 ... Ground electrode, 17 ... Protective element, 18r, 18a ... First winding part, 18t, 18b ... second winding unit, 19 ... clamp, 20 ... simulated capacitor capacitance adjusting device, 21 ... input unit, 22 ... electric amount calculation unit, 23 ... adjustment operation unit

Claims (2)

The secondary side of the RST 3-phase distribution transformer is connected to a 3-phase 3-wire type electric circuit that supplies 3-phase power by grounding one of the 3 phases that are Δ-connected or V-connected to the grounding phase. In a leakage current suppression device that suppresses leakage current generated by the capacitance to ground of an electric circuit
Input the line voltage of each of the two phases of the ungrounded phase and the two phases of the grounded phase to the primary side, connect the positive electrode on the secondary side to the grounded phase, and connect the negative electrode on the secondary side to the ground. A transformer that is connected to the grounding electrode of the above and generates a voltage of the opposite phase of the primary side on the secondary side.
It is connected between the negative electrode on the secondary side of the transformer and the grounding electrode, and generates a compensating current for simulating the ground capacitance and canceling the leakage current generated by the ground capacitance of the electric circuit together with the transformer. With a simulated capacitor to make
A protective element that is connected between the electric circuit and the transformer and shuts off the transformer from the electric circuit when the compensating current exceeding the capacity of the transformer flows.
It is equipped with a simulated capacitor capacitance adjusting device that automatically sets the capacitance of the simulated capacitor.
The simulated capacitor capacitance adjusting device inputs the voltage of any one phase of the line voltage as a reference voltage, and inputs the potential of the grounding point of the class B grounding point and the input unit. The electricity amount calculation unit calculates the compensation current for canceling the leakage current generated by the ground capacitance of the electric path based on the phase of the reference voltage and the potential of the grounding point, and the electricity amount calculation unit. A leakage current suppression device comprising an adjustment operation unit for adjusting and operating the capacitance of the simulated capacitor so that the calculated compensation current can be obtained . The secondary side of the RST 3-phase distribution transformer is connected to a 3-phase 3-wire electric circuit that supplies 3-phase power by grounding the neutral point of the Y-connected 3-phase to class B, and depends on the ground capacitance of the electric circuit. In the leakage current suppression device that suppresses the leakage current that occurs
The phase voltage between each of the two phases of the RST3 phase and the neutral point is input to the primary side, the positive electrode on the secondary side is connected to the neutral point, and the negative electrode on the secondary side is connected to the ground. A transformer that is connected to the ground electrode of the above and generates a voltage of the opposite phase of the primary side on the secondary side,
It is connected between the negative electrode on the secondary side of the transformer and the grounding electrode, and generates a compensating current for simulating the ground capacitance and canceling the leakage current generated by the ground capacitance of the electric circuit together with the transformer. With a simulated capacitor to make
A protective element that is connected between the electric circuit and the transformer and shuts off the transformer from the electric circuit when the compensating current exceeding the capacity of the transformer flows.
It is equipped with a simulated capacitor capacitance adjusting device that automatically sets the capacitance of the simulated capacitor.
In the simulated capacitor capacitance adjusting device, the voltage of any one of the phase voltages is input as a reference voltage, and the potential of the grounding point of the class B grounding is input, and the input unit is used for input. Calculated by the electricity amount calculation unit and the electricity amount calculation unit that calculates the compensation current for canceling the leakage current generated by the ground capacitance of the electric path based on the phase of the reference voltage and the potential of the grounding point. A leakage current suppression device comprising an adjustment operation unit for adjusting and operating the capacitance of the simulated capacitor so that the compensated current can be obtained .

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