JP2019075898A - Leakage current suppression device - Google Patents

Abstract

To provide a leakage current suppression device which suppresses a capacity component leakage current which occurs due to a ground capacitance between electric circuit for supplying three-phase power by B type grounding a secondary side of RST three-phase distribution transformer and earth.SOLUTION: A voltage of an opposite phase of a primary side on a secondary side is generated by respectively inputting a line voltage between each phase of the two phases of a non-ground phase and a ground phase to the primary side of a transformer 14, and connecting a positive electrode of the secondary side of the transformer to the ground phase, and connecting a negative electrode of the secondary side to a ground electrode 16 to the ground, a compensation current is generated to offset a leakage current generated by the ground capacitance of the circuit by connecting a simulation capacitor 15 that simulates the ground capacitance to the negative electrode on the secondary side of the transformer, and a protection element 17 connected between the circuit and the transformer shuts the transformer out of the circuit when a compensating current exceeding the capacity of the transformer flows.SELECTED DRAWING: Figure 1

Description

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

  For example, a 200 V-system transformer of a power facility of a general customer adopts a Y △ -connection transformer from the viewpoint of cost and equipment mass, and supplies three-phase electric power by a three-phase three-wire system. The secondary side of the transformer of this Y Δ connection is B-type grounded to the S phase, and a leakage detection device for detecting leakage in the electric path is provided (for example, see Patent Document 1).

  The leakage current of the electric path is generally referred to as zero-phase current Io, and is composed of capacitance component leakage current Ic and resistance component leakage current Ir. The capacitive component leakage current Ic is generated due to the capacitance to ground between the electrical path and the ground, and the resistive component leakage current Ir is generated due to the insulation deterioration of the electrical path. The purpose of the leakage detection device is to detect the resistance component leakage current Ir that is generated when there is insulation degradation of the electrical path, but many of the leakage detection devices operate when the zero phase current Io is equal to or more than a predetermined value. Detect a short circuit.

  Here, when the capacitance to ground on the secondary side of the transformer increases, the constant capacitance component leakage current Ic increases. Since the capacitive component leakage current Ic flows through the ground resistance of the S-phase B-type grounding point, the ground potential of the S-phase at the grounding point rises when the capacitive component leakage current Ic increases, but the line voltage of the RST 3 phase has a capacitance Since the component leakage current Ic is maintained constant irrespective of the magnitude of the component leakage current Ic, the supply of the three-phase power does not have a major problem.

Japanese Patent Application Laid-Open No. 2003-232826

  However, when the capacitance component leakage current Ic increases, the ratio of the resistance component leakage current Ir of the leakage current Io decreases, the detection accuracy of the resistance component leakage current Ir decreases, and the accuracy of insulation monitoring of the electric path may be affected. (See, for example, FIG. 7 (b) of Patent Document 1).

  Further, there are devices operating on the electric path with the potential at the ground point as a reference voltage, and for such devices, it is necessary to stabilize the potential at the ground point which is the reference potential. Since the capacitive component leakage current Ic flows through the ground resistance of the S-phase B-type ground point and the S-phase ground potential at the ground point rises, the reference voltage fluctuates. Therefore, to stabilize the reference voltage, It is desirable to suppress the capacitive component leakage current Ic.

  Here, in the case of a 3-phase 3-wire electric path in which the secondary side of the RST 3-phase distribution transformer is Y-connected and the neutral point is B-type grounded to supply 3-phase power, the 3-phase 3-wire electric path The leakage current generated by the capacitance between the earth and the earth is different from each other because the phases of the leakage current of the RST phases are shifted by 2π / 3, so that the three phases are balanced. As a result of cancellation, no leakage current always flows. However, if single phase wiring is connected, etc., leakage current may flow if unbalanced, so the secondary side of distribution transformer of RST3 phase is Y-connected and B type grounded at neutral point. Even in the case of a three-phase three-wire electric path supplying power, it is desirable to suppress the capacitive component leakage current Ic.

  It is an object of the present invention to suppress leakage of a capacitive component generated by ground capacitance between an electric path supplying ground and a B-type ground of the secondary side of a distribution transformer of RST 3-phase and supplying 3-phase power. It is providing a current control device.

  In the leakage current suppression device according to the invention of claim 1, the secondary side of the distribution transformer of the RST 3 phase supplies one of the three phases Δ-connected or V-connected as B-type ground to supply three-phase power 3 A leak current suppression device connected to a phase three-wire type electric path and suppressing a leakage current generated by a capacitance to ground of the electric path, wherein a two-phase line of each of two phases of an ungrounded phase and the ground phase Voltage is input to the primary side, the positive side of the secondary side is connected to the ground phase, the negative side of the secondary side is connected to the ground pole to the ground, and the voltage on the secondary side is reversed. It is connected between the transformer to be generated, the negative electrode on the secondary side of the transformer, and the ground electrode to simulate the capacitance to ground and to offset the leakage current generated by the capacitance to the ground of the electric path together with the transformer. A simulation capacitor for generating the compensation current of the It is connected between the scan, characterized in that said transformer when said compensation current flows exceeding the capacity of the transformer and a protection element for blocking the said path.

  The leakage current suppression device according to the invention of claim 2 is a three-phase three-wire system in which the neutral point of the Y-connected three-phase neutral point of the distribution transformer of the RST three-phase is B-type grounded to supply three-phase power. A leakage current suppressing device for suppressing the leakage current generated by the capacitance to ground of the electric path, wherein the phase voltage between each of two phases out of the RST3 phases and the neutral point is 1 A transformer for generating a voltage of the reverse side of the primary side on the secondary side by connecting the positive electrode on the secondary side and connecting the positive electrode on the secondary side to the neutral point and connecting the negative electrode on the secondary side to the ground electrode to the ground; A compensation current for simulating the ground capacitance connected between the negative electrode on the secondary side of the transformer and the ground electrode, and for compensating the leakage current generated by the ground capacitance of the electric path together with the transformer; Between the circuit and the transformer. It is characterized in that said transformer when said compensation current flows exceeding the capacity of the transformer and a protection element for blocking the said path.

  According to a third aspect of the present invention, there is provided a leak current suppressing device according to the first or second aspect of the present invention, wherein a voltage of any one phase of the three phases of line voltage or the phase voltage is inputted as a reference voltage. Leakage current generated by the ground capacitance of the electric path is canceled based on the input portion for inputting the potential of the grounding point of the B type ground, the phase of the reference voltage inputted at the input portion and the potential of the grounding point And an electrostatic capacity adjustment operation unit for adjusting and operating the electrostatic capacity of the simulation capacitor so as to obtain the compensation current calculated by the electric quantity operation unit. It is characterized in that it comprises the simulated capacitor electrostatic capacitance adjustment device.

  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 path and the ground. Therefore, the accuracy of insulation monitoring of the electrical circuit by the insulation monitoring device is not reduced. In addition, since the capacitive component leakage current can be suppressed from flowing through the grounding resistance at the B-type grounding point, the ground voltage at the B-type grounding point can be maintained at about 0V. Therefore, the reference voltage of the device operating with the potential at the ground point as the reference voltage can be stabilized.

Explanatory drawing at the time of the secondary side of a distribution transformer applying the leakage current suppression apparatus which concerns on 1st Embodiment of this invention to the electrical path of (DELTA) connection. Explanatory drawing at the time of applying the leakage current control apparatus which concerns on 1st Embodiment of this invention to the electrical path whose secondary side of a distribution transformer is Y connection. Explanatory drawing of the principle which can cancel | release the leakage current Ig by two winding (1st winding and 2nd winding) of a transformer by the phase of the leakage current Ig which flows into earthing resistance Rb. Explanatory drawing of the selection reference | standard which selects the phase voltage of two phases of phase voltage Vr of three phases, Vs, and Vt by the phase of leakage current Ig which flows into earthing resistance Rb. Explanatory drawing of compensation current If in case the phase of leakage current Ig is located between the leakage current Igs of S phase component, and the leakage current Igt of T phase component. Explanatory drawing of compensation current If in case the phase of leakage current Ig is located between leakage current Igt of T phase component, and leakage current Igr of R phase component. Explanatory drawing at the time of the secondary side of a distribution transformer applying the leakage current suppression apparatus which concerns on 2nd Embodiment of this invention to the electrical path of (DELTA) connection. Explanatory drawing in which the secondary side of the distribution transformer to which this invention is applied shows an example of the electric path of (DELTA) connection. Explanatory drawing of how to obtain | require actual leakage current Ib which flows into earthing | grounding resistance Rb of the electrical path of Fig.8 (a) using Thevenin's theorem.

  Hereinafter, embodiments of the present invention will be described. Prior to the description of the embodiments of the present invention, the capacitive component leakage current generated by the ground capacitance between the three-phase three-wire electric path and the ground to which the present invention is applied will be described. FIG. 8 is an explanatory view showing an example of an electric path in which the secondary side of the distribution transformer to which the present invention is applied has a Δ connection, and FIG. 8 (a) employs a Y Δ connection transformer to make a three-phase three-wire system. 8 is a circuit diagram showing an example of a three-phase three-wire electric path supplying three-phase power, and FIG. 8 (b) is an electric quantity vector diagram.

  In FIG. 8A, the secondary side of the RST 3-phase distribution transformer 11 is Δ-connected, and the secondary-side S phase is B-type grounded to supply 3-phase power to the load 12 in the 3-phase 3-wire system An electrical circuit is formed. Since the S phase on the secondary side of the distribution transformer 11 is subjected to B type grounding, the ground voltage of the S phase basically becomes 0 [V], and the ground voltages of the other R phase and T phase are It becomes the voltage V between. Since the ground voltage of the S phase is basically 0 [V], no leak current flows in the S phase via the ground capacitance Cs with the ground, so the leak current Igs is zero. 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 given to the ground capacitance Cr with the ground of the R phase. Similarly, since the ground voltage of T phase is the line voltage Vts between T phase and S phase, the leakage current Igt {= Vts / (1 / jωCt) to the ground capacitance Ct with the ground of T phase ) Flows. Thus, the leakage current Ig flowing through the ground resistance Rb is a combined current of the R phase leakage current Igr and the T phase leakage current Igt.

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

  By the way, when the leak current Ig of the entire electric path flows to the ground resistance Rb, the ground voltage of the entire electric path is increased by the amount of the voltage drop. Then, since the ground voltage of each phase is not a line voltage, the leakage current Igr of the R phase and the leakage current Igt of the T phase change, the leakage current Igs of the S phase also flows, and it is not zero. Therefore, in FIG. 8A, the leakage current Ig (= Ib) actually flowing through the ground resistor Rb is determined.

  FIG. 9 is an explanatory diagram of how to obtain the actual leakage current Ib flowing through the ground resistance Rb of the electric path of FIG. 8A using the Thevenin's theorem, and FIG. 9 (b) is a circuit diagram in the case where the Thevenin 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 transformer of the Y △ connection to be the target 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 a short circuit of the transformer which is the internal power supply, so a series connection of the ground resistance Rb and the parallel connection of the capacitances Cr, Cs and Ct of the electric path of the RST phase If the capacitances Cr, Cs, and Ct of the RST phase electrical path are equal and C, then Z = Rb + (1 / j3ωC) [Ω]. The circuit current i flowing when the terminals are shorted is obtained as the following equation (1) according to Thevenin's theorem.

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

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

  Here, in the single-phase three-wire system instead of the three-phase three-wire system, the R phase and T phase power sources where the ground voltage is generated are in opposite phase, causing leakage current with the same degree of ground capacitance. However, since the phase of the leakage current differs by π, the constant leakage current flowing to the B type is canceled and the leakage current does not always flow. Also, in the 3-phase 4-wire system with Y-connected secondary side, the neutral wire is N phase, and each phase of RST phase generates a leakage current against the ground capacitance with the ground, but the RST phase Since the phases of the leakage currents of the respective phases are shifted by 2π / 3, they cancel each other and the leakage current does not always flow.

In the case of a three-phase three-wire circuit in which the secondary side of the distribution transformer is Δ-connected, the leakage current due to the ground capacitance is not canceled. Therefore, if the current in the opposite phase can be generated for the R phase and the T phase that 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 does not always flow.
On the other hand, in the case of an electric path where the secondary side is a three-phase three-wire system with Y connection and the neutral point is grounded, leakage current may flow if imbalance occurs due to the connection of a single-phase electric path, etc. In the embodiment of the present invention, the leakage current Ib is also canceled so that the leakage current Ib does not always flow.

  FIG. 1 is an explanatory view in the case where the leakage current suppression device according to the first embodiment of the present invention is applied to the electric path of the secondary side of the distribution transformer of Δ connection. FIG. 1 (a) is a leakage current suppression device for the electric path FIG. 1 (b) is a diagram of the quantity of electricity of the electric path when the circuit board is connected. 1 (a), the electric path is the same as the electric path shown in FIG. 8 (a), and the secondary side of the distribution transformer 11 of the RST 3 phase is Δ-connected, and the S phase of the secondary side is B type grounded Then, it is a three-phase three-wire electric path for supplying three-phase power to the load 12.

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

  The leakage current suppression device 13 includes a transformer 14, simulation capacitors 15r and 15t, a ground electrode 16, and a protection 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 for generating a voltage in reverse phase to the line voltage Vrs, and the second winding portion The reference numeral 18t denotes a winding for generating a voltage in reverse phase of the line voltage Vts. A line voltage Vrs between the ground phase S phase and the non-ground phase R phase is applied to the primary side of the first winding portion 18r, and the secondary side positive electrode is connected to the ground phase S phase, 2 The negative electrode on the next side is connected to the ground electrode 16 to the ground. Similarly, the line voltage Vts between the ground phase S phase and the non-ground phase T phase is applied to the primary side of the second winding portion 18t, and the secondary side positive electrode is connected to the ground phase S phase The negative pole on the secondary side is connected to the ground pole 16 to the ground.

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

  The protection element 17 is connected between the electric path and the transformer 14, and cuts off the transformer 14 from the electric path when the compensation current Ifr and Ift exceeding the capacity of the first winding portion 18r and the second winding portion 18t of the transformer 14 flow. These include switches, fuses, etc.

  Here, the simulation 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 to obtain a desired capacitance. The electrostatic capacitance of the ground path Cr and Ct to ground is adjusted by the switching capacitor. This is performed by adjusting the potential of the ground resistor Rb at the resistance ground point of the S phase to 0V.

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

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

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

  As described above, since the leakage current suppression device 13 generates the compensation current If of the reverse phase of the RT phase which is the main component of the leakage current Ig in the three-phase three-wire system, the leakage current at all times in the electric path is suppressed. As a result, the accuracy of insulation monitoring of the electrical path by the insulation monitoring device is not reduced. Further, since the ground voltage of the B type ground point can be maintained at about 0 V, the reference voltage of the device operating with the potential at the ground point as the reference voltage can be stabilized. In the above description, although the case where the secondary side of the distribution transformer is Δ connection has been described, the invention can be similarly applied to the case where the secondary side of the distribution transformer is V connection.

  Next, FIG. 2 is an explanatory view in the case where the secondary side of the distribution transformer is applied to an electric path with Y connection according to the first embodiment of the present invention. Since the leak current suppression device has the same configuration as that shown in FIG. 1, the same elements as those in FIG.

  In the electric path of FIG. 2, the secondary side of the distribution transformer 11 of RST 3 phase is Y-connected, and the neutral point of the secondary side is B-type grounded to supply 3-phase electric power to the load 12. It is an electric circuit. Further, since the neutral point of the RST3 phase is grounded, the ground voltage of the circuit path of the RST3 phase is the phase voltage.

  Here, the leakage current Ig flowing to the ground capacitance Cr, Cs, Ct to the ground of the electric path of the Y connection on the secondary side of the distribution transformer shown in FIG. 2 is a leakage current flowing to the ground capacitance Cr to the ground of the R phase. These are a leakage current Igs flowing to the ground capacitance Cs with respect to the ground of the S phase and a leakage current Igt flowing to the ground capacitance Ct with the ground of the T phase. Therefore, the leakage current Ig flowing to the ground resistor Rb is a combined current of these, and is expressed by Ig = Igr + Igs + Igt. From this, originally, the transformer 14 generates a voltage of the phase reverse to the phase voltage Vr 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. Three windings of a winding portion 18r, a second winding portion 18s generating a voltage in reverse phase to the phase voltage Vs, and a third winding portion 18t generating a voltage in reverse phase to the phase voltage Vt is necessary.

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

  Accordingly, in FIG. 2, the phase voltages input to the two windings (the first winding 18a and the first winding 18b) of the transformer 14 are two of the three phase voltages Vr, Vs, Vt. Since the phase voltages of the phases are sufficient, the phase voltages of the two phases are selected from the respective phases of the RST phase, and the clamp 19 is held in the electric path to input the phase voltages of the two phases. FIG. 2 shows the case where two phases of the phase voltage Vr and the phase voltage Vs are selected.

  FIG. 3 is an explanatory view of the principle that the leakage current Ig (= Igr + Igs + Igt) can be canceled by the two windings (the first winding 18a and the second winding 18b) by the phase of the leakage current Ig flowing through the grounding resistor Rb. is there. FIG. 3 (a) is a phase voltage vector diagram of a RST three phase of Y connection in the secondary side of the distribution transformer. Now, as the leakage current Ig, as shown in FIG. 3 (b), the leakage current Igr of the R phase component It is assumed that the leakage current Igs of the S phase component and the leakage current Igt of the T phase component flow. Leakage current Igr of R phase component leads π / 2 to phase voltage Vr, leakage current Igs of S phase component leads π / 2 to phase voltage Vs, and leakage current Igt of T phase component to phase voltage Vt In contrast, it is π / 2 lead. As shown in FIG. 3C, the leakage current Ig is a combined current of the leakage currents Igr, Igs and Igt of the respective phase components, and is the leakage current Ig flowing to 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, the 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 as shown in FIG. 3 (e). In FIG. 3E, the leakage current Igr of the R phase component is left unchanged, and the leakage current Igs of the S phase component is changed to Igs1. This is to take into account the leakage current Igt of the T phase component.

  Thus, 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 A certain leakage current Ig can be represented by Ig (= Igr + Igs1), and the leakage current suppressor 13 generates a compensation current If (= Ifr + Ifs) for offsetting this Ig (= Igr + Igs1). In that case, the phase voltages input to the two windings (the first winding 18a and the first winding 18b) of the transformer 14 are two phases of the phase voltage Vr and the phase voltage Vs. As a result, the transformer 14 can offset the leakage current Ig with two windings (first and second windings) without preparing three windings.

  FIG. 4 is an explanatory view of a selection criterion for selecting the phase voltage of two phases among the phase voltages Vr, Vs and Vt of three phases according to the phase of the leakage current Ig flowing to 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 the 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 the 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 voltages input to the first winding 18b) are two phases of the phase voltage Vr and the phase voltage Vs.

In the 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 (the first winding 18 a and the first winding 18 b The phase voltage input to is the two phases of the phase voltage Vs and the phase voltage Vt.
FIG. 5 is an explanatory diagram of the compensation current If in the case where the phase of the leakage current Ig is 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, 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. In FIG. 5B, the leakage current Igs of the S phase component is left unchanged, 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.

  Thus, 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 A certain leakage current Ig can be represented by Ig (= Igs + Igt1), and the leakage current suppressor 13 generates a compensation current If (= Ifs + Ift) for canceling out this Ig (= Igs + Igt1). In that case, the phase voltages input to the two windings (the first winding 18a and the first winding 18b) of the transformer 14 are two phases of the phase voltage Vs and the phase voltage Vt. As a result, the transformer 14 can offset the leakage current Ig with two windings (first and second windings) without preparing three windings.

  In the 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 (the first winding 18a and the first winding 18b The phase voltage input to is two phases of the phase voltage Vt and the phase voltage Vr. FIG. 6 is an explanatory diagram of the compensation current If in the case where the phase of the leakage current Ig is 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, 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 as shown in FIG. 6 (b). In FIG. 6B, the leakage current Igt of the T phase component is left unchanged, 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.

  Thus, 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 A certain leakage current Ig can be represented by Ig (= Igt + Igr1), and the leakage current suppressor 13 generates a compensation current If (= Ift + Ifr) for offsetting this Ig (= Igt + Igr1). In that case, the phase voltages input to the two windings (the first winding 18a and the first winding 18b) of the transformer 14 are two phases of the phase voltage Vt and the phase voltage Vr. As a result, the transformer 14 can offset the leakage current Ig with two windings (first and second windings) without preparing three windings.

  Next, the 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 R phase is applied to the primary side of the first winding portion 18a of the transformer 14, and the positive electrode on the secondary side is connected to the neutral point to which the grounding resistor Rb is connected. Are connected to the ground electrode 16 to the ground. Thus, the first winding portion 18a generates a voltage in reverse phase to the phase voltage Vr. The phase voltage Vs of 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 grounding resistor Rb is connected, and the negative electrode on the secondary side is It is connected to a ground electrode 16 to the ground. As a result, the second winding portion 18b generates a voltage in reverse phase to the line voltage Vs.

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

  The protection element 17 is connected between the electric path and the transformer 14, and cuts off the transformer 14 from the electric path when the compensation current Ifr, Ifs exceeding the capacity of the first winding portion 18a or the second winding portion 18b of the transformer 14 flows. These include switches, fuses, etc.

  As shown in FIG. 2, the leakage current Igr flows in the electric path along the capacitance R to ground of the R phase, and the leakage current Igs flows in the ground capacitance Cs to the ground of the S phase. A leakage current Igt flows in the ground capacitance Ct with respect to the ground. Thus, the leakage current Ig flowing through the ground resistor Rb becomes the combined current Ig (= Igr + Igs + Igt).

  On the other hand, since the leakage current suppression device 13 is connected via the protection 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 a positive electrode on the secondary side of the first winding portion 18a → grounding resistance Rb → neutral point → grounding 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 a positive electrode of the secondary side of the second winding portion 18b → grounding resistance Rb → neutral point → grounding electrode 16 → simulation capacitor 15b → second winding portion 18b It flows to the negative electrode on the next side. As a result, the compensation current If flowing through the grounding resistor Rb becomes a combined current If (= Ifr + Ifs) of the compensation current Ifr of the R phase component and the compensation current Ifs of the S phase component.

  Next, a leakage current suppression device according to a second embodiment of the present invention will be described. FIG. 7 is an explanatory view in the case where the leakage current suppressing device according to the second embodiment of the present invention is applied to an electric path of the Δ connection on the secondary side of the distribution transformer.

  The second embodiment is different from the first embodiment shown in FIG. 1 in that a simulation capacitor electrostatic capacitance adjustment device for automatically setting the capacitance of the simulation capacitor is provided. The same elements as those in FIG. As described above, the simulation capacitor 15 uses a switching capacitor. The simulation capacitor 15 is formed of, for example, a plurality of capacitors of 0.01 μF, 0.1 μF, and 1 μF, and these capacitors are selected to obtain desired capacitance.

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

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

  Since the leakage current Ig is a current flowing through the ground resistor Rb, the potential Vb at the ground point is in phase with the leakage current Ig. Therefore, the electric quantity computation unit 22 sets the phase of the reference voltage Vrs and the potential Vb of the ground point as the phase of 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 can be obtained as a phase shifted by π from the leakage current Ig. Also, the magnitude of the compensation current If is the same as the magnitude of the leakage current Ig.

  The capacitance adjustment operation unit 23 adjusts and operates the capacitance of the simulation capacitor so as to obtain the compensation current If calculated by the electricity amount calculation unit. In this case, the capacitor of the simulation capacitor consisting of a plurality of capacitors is selected so that the potential Vb of the ground point becomes 0V. The capacitor is adopted when the potential Vb at the grounding point becomes minimum. In the second embodiment, since the simulation capacitor electrostatic capacitance adjustment device 20 is provided, the capacitance of the simulation capacitor can be easily set so that the potential Vb of the ground point becomes 0V.

  Although the above description has described the case where the secondary side of the distribution transformer is applied to the electric path of the Δ connection, the secondary side of the distribution transformer can also be applied to the electric path of the V connection. The secondary side of the device can also be applied to a Y-connected circuit. When the secondary side is applied to a Y-connected circuit, a phase voltage is input instead of the line voltage.

  While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and the gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

11: Distribution transformer, 12: Load, 13: Leakage current suppressor, 14: Transformer, 15: Capacitor for simulation, 16: Ground electrode, 17: Protective element, 18r, 18a: First winding portion, 18t, 18b ... 2nd winding part, 19 ... clamp, 20 ... capacitor capacitance adjustment device for simulation, 21 ... input part, 22 ... electric quantity operation part, 23 ... adjustment operation part

Claims (3)

The secondary side of the RST three-phase distribution transformer is connected to a three-phase three-wire electric path supplying three-phase power by grounding one of the three phases in which Δ connection or V connection is performed, and the other side of the electric path In a leakage current suppression device that suppresses leakage current generated by electrostatic capacitance,
Input the line voltage of the two phases of each of the two phases of the ungrounded phase and the ground phase to the primary side, connect the positive electrode of the secondary side to the ground phase, and connect the negative electrode of the secondary side to the ground A transformer connected to the ground pole of the switch to generate a voltage of the reverse phase of the primary side on the secondary side,
Connected between the negative electrode on the secondary side of the transformer and the ground electrode to simulate the capacitance to ground and generate a compensation current for canceling the leakage current generated by the capacitance to ground of the electric path together with the transformer And a capacitor for simulation
A leakage current suppressing device, comprising: a protection element connected between the electric path and the transformer and configured to cut off the transformer from the electric path when the compensation current exceeding the capacity of the transformer flows. The secondary side of the RST 3-phase distribution transformer is connected to a 3-phase 3-wire electric path that supplies 3-phase power by grounding the Y-connected 3-phase neutral point of the 3-phase 3-wire system, and the ground capacitance of the electric path In the leakage current suppressor for suppressing the leakage current generated,
Input the phase voltage between each of the two phases out of the RST3 phase and the neutral point to the primary side, connect the positive side of the secondary side to the neutral point, and connect the negative side of the secondary side to the ground A transformer connected to the ground pole of the switch to generate a voltage of the reverse phase of the primary side on the secondary side,
Connected between the negative electrode on the secondary side of the transformer and the ground electrode to simulate the capacitance to ground and generate a compensation current for canceling the leakage current generated by the capacitance to ground of the electric path together with the transformer And a capacitor for simulation
A leakage current suppressing device, comprising: a protection element connected between the electric path and the transformer and configured to cut off the transformer from the electric path when the compensation current exceeding the capacity of the transformer flows.   An input unit for inputting a voltage of any one phase of the line voltage of the three phases or the phase voltage as a reference voltage and inputting the potential of the ground point of the B type ground, and the reference voltage input at the input unit An electric quantity calculation unit for calculating a compensation current for offsetting a leakage current generated by the ground capacitance of the electric path based on a phase of the electric field and the potential of the ground point, and a compensation current calculated in the electric quantity calculation unit 3. A simulation capacitor electrostatic capacity adjustment device comprising: a capacitance adjustment operation unit for adjusting and operating the capacitance of the simulation capacitor so as to obtain the above. Leakage current suppression device as described.

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