JP2010127860A - Device and method for measuring leak current - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and a method for measuring leak current, which can enhance reliability in measurement values of the leak current flowing through ground insulating resistance of a load system connected with power distribution line fed from 400 V class star-shaped distribution power source. <P>SOLUTION: The device includes a processing operation part 16, being equipped with a fundamental wave processor 3, which makes signal processing of voltage to ground of any one phase among three phases input from the star-shaped distribution power source 1, line voltage between any 2 lines among 3 lines, and zero phase current I<SB>0</SB>detected from the power distribution line 4 by a zero phase current transformer 9, and then measures phase difference between input voltage and the zero phase current I<SB>0</SB>to make signal processing, and an operation part 14. The operation part 14 calculates a phase angle θ to the input voltage of the zero phase current I<SB>0</SB>and computes both active and reactive elements to the input voltage from both the phase angle θ and value of the zero phase current I<SB>0</SB>. Thus the value of total leak current Igr for each phase excluding one sound phase and its reliability are calculated from the effective value of the computed elements. This value of leak current Igr and an imbalance differential current value derived from imbalance of ground capacitance are displayed on a display part 15. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a leakage current measuring apparatus and a measuring method for measuring a leakage current flowing from a voltage application portion to a ground portion of an electric circuit and an electric device.

  2. Description of the Related Art Conventionally, as a method for examining the insulation state of an electric circuit and an electrical device, a method in which a part to be measured is cut off and measured with an insulation resistance meter has been widely used. Such a method cannot be applied to distribution lines where continuous blackouts are not allowed, continuous operation factories, and the like.

In view of this, a technique for examining the insulation state of the electric circuit and the electric device while maintaining the live line without causing a power failure of the electric circuit to be measured and the electric device has been proposed and used. As this type of technology, there is a technique in which a zero-phase current transformer is used to detect a zero-phase current I ₀ , which is a current flowing from a voltage application portion of an electric circuit and electrical equipment to a ground portion. The zero-phase current I ₀ detected by the zero-phase current transformer is a leakage current Igr that flows through an insulation resistance between the voltage application portion and the ground portion of the electric circuit and electrical equipment, and between the voltage application portion and the ground portion. It consists of a vector sum with a leakage current Igc that flows through a ground capacitance that normally exists.

  By the way, a technique for measuring leakage current that is practically used in a power distribution system in which one of 200 V class three-phase three wires that are currently practically used is grounded has been increasingly adopted by large-scale customers in recent years. In addition, the low-voltage three-phase winding of the transformer, which is the standard for overseas power distribution systems, is connected in a star shape, and power is supplied from a power source grounded at the neutral point of the three-phase winding connected to this star shape. 400V class three-phase four-wire system or three-phase three-wire power distribution system (hereinafter referred to as a star-shaped power distribution system is not applicable to insulation measurement of electrical lines and equipment.

At present, in the star distribution system, there is a wide range of methods for measuring the zero-phase current I ₀ with a zero-phase current transformer in a grounded wire or four or three distribution lines and monitoring the insulation based on this value. Has been done.

At this time, if the value of the ground capacitance existing between the voltage application portion and the ground portion of the electric circuit or electrical equipment is the same for all three phases (this state is called a balanced state), the ground electrostatic capacitance of each phase The total value of the three phases of the leakage current Igc flowing through the capacity is 0, and therefore the value of the zero-phase current I ₀ is the ground fault current that flows when a ground fault occurs through the ground insulation resistance at one point in this distribution system. Indicates the value of.

  By the way, the star-shaped power distribution system has three relative ground voltages and three-phase line voltages that are equal in magnitude and have a phase difference of 120 degrees, and single-phase line voltages and single relative ground voltages are transmitted via distribution lines. Applied to three-phase and single-phase load equipment. The values of the ground capacitance of these distribution lines and load facilities are in an unbalanced state that is different for each of the three phases. In the current system, there is no clarification about the influence of this unbalanced state on the measured value of the leakage current Igr, and the reliability of the measured value of the leakage current Igr is greatly reduced.

Further, when there is a leakage current Igr flowing through the ground insulation resistance in one phase, if the degree of unbalance that makes the ground capacitance value different in each of the three phases is small, the value of the leakage current Igr is The value of the zero-phase current I ₀ can be used. For example, when the leakage current Igr having the same value is generated in two phases, the phase of the leakage current of the two phases is 120 degrees different, so that it is twice as large. No value is shown, and only the value of the leakage current Igr for one phase synthesized by the vector is shown. In addition, the load of this system is connected across 3 to 4 lines or 2 lines of the distribution line. For example, when the center point of the transformer winding connected between the 2 lines is grounded, the leakage current Igr Since the ground voltage at this center point is half the value of the ground voltage of the three-phase terminal, the value of the leakage current is also half of the value grounded at the three-phase terminal through the same ground leakage resistance, In the leakage current measuring device that determines the degree of failure based on the size, it is evaluated that the insulation state is good with respect to the ground leakage resistance. As a result, the determination of the insulation state is wrong, and failure to take measures against insulation can lead to a serious failure.

  Furthermore, in the case of a device that employs a method that measures the insulation state by connecting a grounding wire to a meter and inputting a ground voltage, if there is no effective grounding point at the measurement location, measure the insulation state. It becomes impossible.

  As another method of measuring the insulation state, there is a method of measuring the leakage current Igr by supplying a low frequency low voltage to the distribution line. Although this method can be applied to all circuits, it requires complicated grounding and grounding, and is difficult to provide at low cost.

In addition, there exist some which are described in Unexamined-Japanese-Patent No. 3-179271 (patent document 1) and Unexamined-Japanese-Patent No. 2002-125313 (patent document 2) as a prior art of this kind of leakage current measurement.
JP-A-3-179271 JP 2002-125313 A

  In the power distribution system adopting the star power distribution system, the degree of unbalance in which the value of the ground capacitance is different in each of the three phases is insulated between the voltage application part and the ground part of the electric circuit and electrical equipment. By clarifying the influence of the leakage current Igr flowing through the resistance on the measured value, the reliability of the measured value of the leakage current Igr is improved, and the measured value of the leakage current Igr generated between the two phases or between the two phases is reduced to the ground. Measured as a normal value corresponding to the value of leakage resistance, and the voltage element input at the time of measurement is one-phase ground voltage of three relative ground voltages or one line voltage of three line voltages It is an object of the present invention to provide a leakage current measuring device and a measuring method that are only available.

The present invention proposed to solve the above technical problem is that the secondary side winding of the transformer is connected in a star shape, the three-phase voltage terminals are R, S, T, and the star connection Leakage current measurement to measure leakage current Igr caused by ground insulation resistance of three-phase four-wire system or three-phase three-wire distribution system and electric equipment fed from a power supply with N as grounded neutral point In the apparatus, the line voltages E _SR , E _TS , E _RT generated between the terminals R, S, T of the secondary winding and the terminals R, S, T of the secondary winding and neutral Voltage detection means for measuring any of ground voltages E _R , E _S , E _T generated between points N, and _zero for detecting a zero-phase current I ₀ that is a vector sum of currents flowing through the three-phase distribution lines Phase current detection means, and the voltage line voltage E _SR , E _TS , E _RT detected by the voltage detection means or Any one of the ground voltages E _R , E _S , and E _T is input, and any one of the input voltage line voltages E _SR , E _TS , E _RT or the ground voltages E _R , E _S , E _T is input. a reference voltage, a phase comparator for comparing the reference voltage and the phase of the zero-phase current I _0, with respect to the reference voltage, the zero-phase current I ₀ and the active ingredient a-phase, which at right angles with A measurement value separated into an ineffective component B having a phase difference is obtained, and line voltages E _SR , E _TS , E _RT generated between the terminals R, S, T or the terminals R, S, T and neutral The effective component A of the zero-phase current I ₀ obtained when any one of the ground voltages E _R , E _S , and E _T generated between the points N is used as a reference voltage, and the reactive component B having a phase difference orthogonal to the effective component A. Based on the above, the leakage current Igr generated in two of the R phase, S phase, and T phase The value of the leakage current Igr generated in one of the total value, R phase, S phase, and T phase, within the load connected between two or three phases of the R phase, S phase, and T phase Calculating means for calculating the value of the leakage current Igr generated.

Then, when the E value at the time of the ground voltage E _R, E _S, a reference voltage of either of E _T generated between the respective terminals R, S, T and the neutral point N, each terminal R , S, T, when any of the line voltages E _SR , E _TS , E _RT is used as a reference voltage, the value of this reference voltage is set to √3E and the phase comparison with the zero phase current I ₀ is performed. The leakage current Igr is calculated.

Here, more specifically, the calculation means is expressed as follows when any one of the line voltages E _SR , E _TS , E _RT generated between the terminals R, S, T is used as a reference voltage. An electric circuit and an electric device connected to the R, S, and T terminals with the maximum value among the value of (B−√3A), the value of equation (B + √3A), and the value of equation (−2B) Calculated as the leakage current Igr caused by the overall ground insulation resistance.

Further, the arithmetic means uses the equation (A−√3B) when any one of the ground voltages E _R , E _S , E _T generated between the terminals R, S, T and the neutral point N is used as a reference voltage. ), The value of the formula (A + √3B), and the maximum value of the value of the formula (−2A) are the ground insulation resistance of the electric circuit connected to the R, S, and T terminals and the entire electrical equipment. As a leakage current Igr caused by

Further, the calculation means may be configured to detect a mismatch in ground capacitance values of the electric circuit and / or electric device connected to the R, S, and T terminals included in the leakage current Igr. The resulting current value is calculated as a value between (-2I ₀ ) and (2I ₀ ).

  The leakage current measuring apparatus according to the present invention preferably includes display means and displays the result calculated by the calculation means on the display means for notification.

  Furthermore, the leakage current measuring apparatus according to the present invention includes an alarm unit, and when the value of the leakage current Igr obtained by the calculation unit exceeds a predetermined value, an alarm is issued from the alarm unit, whereby the leakage current It can be notified that the value of Igr has exceeded a predetermined value.

  Furthermore, the leakage current measuring apparatus according to the present invention further includes a breaking means, and when the value of the leakage current Igr calculated by the computing means exceeds a predetermined value, the breaking circuit cuts off the electric circuit. Make it possible.

The present invention also provides a power supply in which the secondary winding of the transformer is connected in a star shape, the three-phase voltage terminals are R, S, T, and the neutral point of the star connection is N. In the leakage current measuring method for measuring the leakage current Igr caused by the ground insulation resistance of the three-phase four-wire system or the three-phase three-wire distribution system and the electrical equipment to be fed, Line voltages E _SR , E _TS , E _RT generated between the terminals R, S, T, and ground voltages E _R , generated between the terminals R, S, T of the secondary winding and the neutral point N, A voltage detection step for measuring either E _S or E _T , a zero-phase current detection step for detecting a zero-phase current I ₀ that is a vector sum of currents flowing through the three-phase distribution lines, and the voltage detection step It detected the line voltage _{E SR, E TS, E RT} or above ground voltages _{E R, E S,} either _{E T} Is input, the input or line voltage _{E SR,} and E _{TS, E RT} or ground voltage _{E R,} E S, the reference voltage _{E T,} the phase between the reference voltage and the zero-phase current _{I 0} A phase comparison step that compares the zero-phase current I ₀ with respect to the reference voltage, and a measurement value obtained by separating the zero-phase current I ₀ into an in-phase active component A and an ineffective component B having a phase difference perpendicular thereto, The line voltages E _SR , E _TS , E _RT generated between the terminals R, S, T, or the ground voltages E _R , E _S , E _T generated between the terminals R, S, T and the neutral point N Based on the effective component A of the zero-phase current I ₀ obtained when either one is used as a reference voltage and the reactive component B having a phase difference perpendicular thereto, two of the R phase, S phase, and T phase are used. The total value of the leakage current Igr generated in the phase, the phase generated in one of the R phase, S phase, and T phase A calculation step of calculating the value of the leakage current Igr and the value of the leakage current Igr generated in the load connected between two or three phases of the R phase, S phase, and T phase.

Then, when the E value at the time of the ground voltage E _R, E _S, a reference voltage of either of E _T generated between the respective terminals R, S, T and the neutral point N, each terminal R , S, T, when any of the line voltages E _SR , E _TS , E _RT is used as a reference voltage, the value of this reference voltage is set to √3E and the phase comparison with the zero phase current I ₀ is performed. The leakage current Igr is calculated.

Here, more specifically, the calculation means is expressed as follows when any one of the line voltages E _SR , E _TS , E _RT generated between the terminals R, S, T is used as a reference voltage. An electric circuit and an electric device connected to the R, S, and T terminals with the maximum value among the value of (B−√3A), the value of equation (B + √3A), and the value of equation (−2B) Calculated as the leakage current Igr caused by the overall ground insulation resistance.

Further, the calculation step is performed by using the formula (A−√3B) when any one of the ground voltages E _R , E _S , and E _T generated between the terminals R, S, T and the neutral point N is a reference voltage. , The value of the formula (A + √3B), and the value of the formula (−2A) are set to the ground insulation resistance of the electric circuit connected to each of the R, S, and T terminals and the entire electrical equipment. Calculated as the resulting leakage current Igr.

  As described above, in the present invention, the three terminals R, S, and T of the secondary winding of the transformer are three-relative to the neutral point N of the secondary winding connected to the ground pole G. In the star distribution system that generates earth voltage, the measured value of the ground fault current that has been measured in the case of an earth leakage failure inside the load connected between two or three phases, which was conventionally measured as an excessively small value, Since the measurement is performed as a value corresponding to the value of the leakage current Igr caused by the ground insulation resistance of the electric device, the leakage current Igr caused by the ground insulation resistance can be measured with high reliability.

  In particular, the present invention is applied to a star-shaped power distribution system used in a high-voltage distribution system of 400 V class that has a high risk of causing a serious accident when a leakage failure occurs in a load facility connected to a distribution line. By applying it, it is possible to prevent a leakage accident with high reliability.

  Further, according to the present invention, the three terminals R, S, and T of the secondary winding of the transformer have three relative ground voltages with respect to the neutral point N of the secondary winding connected to the ground pole G. When measuring the leakage current Igr due to the earth insulation resistance of electric circuits and electrical equipment in the generated star distribution system, the leakage current Igr is not affected even if a line voltage that does not require a ground terminal for voltage input is input. Since measurement is possible, reliable measurement is possible even at the end of the distribution system lacking a reliable ground terminal.

Furthermore, in a conventionally used or proposed interrupting device that detects a leakage current Igr and interrupts the electric circuit, the value of the ground capacitance existing between the voltage application part and the ground part of the electric circuit or electrical equipment In anticipation of an increase in the zero-phase current I ₀ due to an imbalance that varies among the three phases, the fault operating current of the earth leakage breaker that operates by detecting the zero-phase current I ₀ was set to an excessive value However, in the present invention, it becomes possible to indicate the degree of the influence of the unbalanced state as described above on the measurement result by a numerical value, and by performing adjustment that reflects this numerical value when setting the failure operation current value, Since the earth leakage breaker can be operated without setting the fault operating current to an excessive value, the system and load can be protected more safely, and unexpected power outage accidents can be reduced.

  Furthermore, according to the present invention, since the result calculated by the calculation means is displayed on the display means, the state of the distribution system can be constantly monitored.

  Furthermore, according to the present invention, since the alarm means is provided, the fact that the leakage current Igr is in an abnormal state can be notified by an alarm such as a sound, so that an accident can be prevented.

  Hereinafter, embodiments of a leakage current measuring apparatus and a measuring method to which the present invention is applied will be described with reference to the drawings.

  FIG. 1 is a schematic system diagram showing an example in which the leakage current measuring apparatus according to the present invention is applied to a power distribution system employing a star power distribution system in which low-voltage three-phase windings of a transformer are connected in a star shape. Note that the star-shaped power distribution system is a 400V class three-phase three-wire system that is fed from a power source in which the three-phase winding on the low voltage side of the transformer is connected in a star shape, or a star-shaped winding as shown in FIG. There is a three-phase four-wire system that includes a neutral wire that is connected to a neutral point and grounded.

  The leakage current measuring apparatus according to the present invention measures the leakage current Igr caused by the electric circuit of the distribution system adopting this star-shaped three-phase three-wire or three-phase four-wire distribution system and the ground insulation resistance of the electrical equipment.

  A distribution system employing a three-phase three-wire or three-phase four-wire star distribution system to which the leakage current measuring apparatus according to the present invention is applied, as shown in FIG. 1, is a low voltage of a three-phase transformer for distribution. A winding 1 connected in a star shape is provided on the side. The star winding 1 is connected to a load facility 5 via a distribution line 4 which is a three-phase connection line.

The star winding 1 will be described more specifically. The star winding 1 has three windings 1a, 1b, and 1c connected so as to form a star shape. Three-phase distribution lines 4 _R , 4 _S , 4 _T are connected to the three-phase terminals R, S, T, which are one of the terminals 1b, 1c, and the other ends of the windings 1a, 1b, 1c are shared. The neutral point N is combined to form a neutral point N. The neutral point N is connected to the ground electrode G via the ground line 8. Incidentally, in the power distribution system of the three-phase four-wire, the neutral point N, and is further connected to the neutral wire 4 _N as the distribution line.

Between the three-phase terminals R, S, and T, which are one of the three windings 1a, 1b, and 1c constituting the star-shaped winding 1, there are three-phase line voltages as shown in FIG. _ESR , _ETS , and _ERT are generated. Between the neutral point N, which is the ground point where the other ends of the windings 1a, 1b, and 1c are coupled to the three-phase terminals R, S, and T, three-phase ground voltages E _R and E _{S are provided.} , E _T are generated. Line voltages E _SR , E _TS , E _RT generated between the three-phase terminals R, S, T, and three-phase ground voltages generated from the neutral point N to the three-phase terminals R, S, T E _R , E _S , and E _T are applied to the load facility 5 through the distribution lines 4 _R , 4 _S , 4 _T and the neutral line 4 _N. The ground voltages E _R , E _S , and E _T are applied between the neutral wire 4 _N and the distribution lines 4 _R , 4 _S , and 4 _T, and the line voltages E _SR , E _TS , and E _RT are applied. For example, when the voltage is 440 V, the ground voltages E _R , E _S , and E _T are 254V that is √ of √3, and are voltages that can be used in lighting or in the home. For this reason, the three-phase four-wire distribution system is widely spread in consumers and overseas using a distribution system in which single-phase loads such as three-phase power loads and lighting are mixed.

Further, the three-phase distribution lines 4 _R , 4 _S , 4 _T and the load equipment 5 connected thereto have ground capacitances C _R , C _S , C _T. Specifically, there is the earth capacitance C _R is the R-phase distribution line 4 _R and load equipment 5 connecting the terminal R of the three-phase and load facility 5, these electrostatic capacitance C _R , C _S , and C _T always carry ground currents IgcR, IgcS, and IgcT. Also, ground leakage resistances rR, rS, rT may occur in the three-phase distribution lines 4 _R , 4 _S , 4 _T and the load equipment 5 connected to them. Leakage currents IgrR, IgrS, and IgrT flow through these ground leakage resistances rR, rS, and rT. The neutral line 4 _N also has a ground capacitance, but the ground voltage is almost zero, so the ground leakage current is omitted.

Leakage current measuring apparatus according to the present invention for measuring the leakage current Igr caused by the insulation resistance of the electrical circuit of the power distribution system and the electric equipment adopting the star-shaped three-phase three-wire or three-phase four-wire distribution system as described above Includes a processing calculation unit 16 including a fundamental wave processing unit 3, a calculation unit 14, and a display unit 15. Then, in the case of measuring the leakage current Igr occurring distribution system employing the power distribution system of the three-phase three-wire system, the fundamental wave processing unit 3 of the processing operation unit 16, the distribution line 4 _R, 4 _S , 4 _T is input through a zero-phase current transformer 9 that detects the zero-phase current I ₀ , which is the vector sum of the currents flowing through _T. Then, in the case of measuring the leakage current Igr occurring distribution system employing the power distribution system of the three-phase four-wire system, the fundamental wave processing unit 3 of the processing operation unit 16, the distribution line 4 _R, 4 _S , 4 _T and the neutral line 4 _N are input through a zero-phase current transformer 9 that detects the zero-phase current I ₀ , which is the vector sum of the currents flowing through the neutral line 4 _N.

Furthermore, ground current IgcR flowing earth capacitance C _R generated in distribution lines 4 _R and load equipment 5, flows through the earth capacitance C _S generated in the distribution lines 4 _S and load equipment 5 ground current IgcS, distribution lines 4 _T and load equipment 5 to the resulting ground electrostatic capacitance _{C T} through the ground current IGCT, distribution lines _{4 R} and load equipment 5 to the resulting leakage current IgrR flowing to ground leakage resistance rR, distribution lines _{4 S} and load equipment 5 leakage current flows to ground leakage resistance rS generated in IGRS, distribution lines 4 _T and load equipment zero phase is the vector sum of the currents in the leakage current IgrT flowing to ground leakage resistance rT generated in 5 current I ₀ is the ground line 8 And is fed back to the neutral point N of the three-phase winding and is input to the fundamental wave processing unit 3 via the zero-phase current transformer 9.

Here, a measuring method and principle of leakage current Igr caused by ground insulation resistance generated in a distribution system adopting a star-connected three-phase three-wire or three-phase four-wire distribution system, and the above-mentioned ground insulation resistance Measuring method for measuring current value caused by mismatch of ground capacitance C _R , C _S , C _T of each phase of three phases R, S, T included in measured value of leakage current Igr caused by And the principle will be described.

As shown in FIG. 1, in a distribution system diagram using a three-phase three-wire or three-phase four-wire power distribution system in which a low-voltage three-phase winding of a transformer is connected in a star shape, between terminals R, S, and T. The generated line voltages E _SR , E _TS , E _RT and the ground voltages E _R , E _S , E generated from the terminals R, S, T to the neutral point N which is the ground point of the star winding. _T can be expressed as a vector as shown in FIG.

  Here, when measuring the leakage current Igr and the like, the reference voltage E, which is a measurement reference input to the leakage current measuring device, is expressed as a reference vector on the real axis, which is the horizontal axis, as shown in FIG. .

By the way, in the three-phase three-wire or three-phase four-wire distribution system connected in a star shape, any of the ground voltages E _R , E _S , E _T generated between the terminals R, S, T and the neutral point N When that value is E, any one of the line voltages E _SR , E _TS , and E _RT generated between the terminals R, S, and T is √3E.

Therefore, when the reference voltage line voltage E _SR generated between the terminal S and the terminal R, the value is indicated ground voltage E _R, E _S, to the value E of E _T as √3E, ground The voltages E _R , E _S , and E _T can be expressed by a vector symbol method as in the following formulas (1) to (3).

E _R = 0.5√3E−j0.5E (1)
E _S = −0.5√3E−j0.5E (2)
E _T = jE (3)
The ground current IgcR flowing earth capacitance C _R generated in distribution lines 4 _R and load equipment 5 of R-phase, flows through the earth capacitance C _S generated in the distribution lines 4 _S and load equipment 5 of the S-phase The ground current IgcT, the ground current IgcT flowing through the ground capacitance C _T generated in the T-phase distribution line 4 _T and the load facility 5 is expressed by the following formula, where 2π × commercial frequency (50 Hz or 60 Hz) is an angular frequency ω: (4) to (6).

IgcR = jωC _R E _R = 0.5ωC _R E + j0.5√3ωC _R E (4)
_{IgcS = jωC S E S = 0.5ωC} S E-j0.5√3ωC S E ··· (5)
_{IgcT = jωC T E T = -ωC} T E ··· (6)
Also, distribution lines 4 _R of the connected R-phase terminal R and the load equipment 5, S-phase distribution line 4 _S and load equipment 5, T-phase distribution line 4 _T and load equipment 5 each ground leakage resistance rR, If rS and rT exist, the leakage currents IgrR, IgrS, and IgrT flowing through the ground leakage resistances rR, rS, and rT can be expressed by the following equations (7) to (9).

IgrR = E _R /rR=0.5√3E/rR−j0.5E/rR (7)
_{IgrS = E S /rS=-0.5√3E/rS-j0.5E/rS ··· (8} )
IgrT = E _T / rT = jE / rT (9)
The zero-phase current I _{0, which} is a current flowing in the ground line 8 connecting the neutral point N of the winding 1 and the ground pole G, is distributed in the R, S, T phase distribution lines 4 _R , 4 _S , 4 _T , and in the case of a three-phase four-wire system, a vector sum of currents including the current flowing through the neutral line 4 _N connected to the neutral point N, that is, the above formulas (4) to ( 6) and formulas (7) to (9) are added, and can be represented by the following formula (10).
I ₀ = {0.5√3 (1 / rR−1 / rS) + 0.5ωC _R + 0.5ωC _S −ωC _T } E +
j {1 / rT−0.5 / rR−0.5 / rS + 0.5√3 (ωC _R −ωC _S )} E
... (10)
Here, when measuring the leakage current Igr, when any one of the line voltages E _SR , E _TS , and E _RT inputted to the leakage current measuring device is set to the reference voltage √3E, the above equation (10) The zero-phase current I ₀ represented, the effective component A of the zero-phase current I ₀ in phase with the reference voltage √3E, and the reactive component B of the zero-phase current I ₀ advanced by 90 degrees from the reference voltage √3E The relationship is represented as the vector diagram of FIG.

Here, IomegaC _R is leakage current IgcR flowing through the earth capacitance _{C R} of the R-phase, IomegaC _S and IomegaC _T is the earth capacitance _C S of the S-phase and T-phase, flowing in the _{C T} Leakage currents IgcS and IgcT, and E / rR, E / rS, and E / rT are leakage currents IgrR, IgrS, and IgrT flowing through the ground leakage resistances rR, rS, and rT, respectively, and are thus input as reference voltages. for example the active ingredient a of the line voltage E _SR in phase of the zero-phase current I _0, so is the real part of I ₀ and the equation of the vector diagram shown in FIG. 3 (10), by the following equation (11) Can show.
A = 0.5√3 (IgrR−IgrS) + 0.5IgcR + 0.5IgcS−IgcT
(11)
Since the invalid component B of the zero-phase current I ₀ whose phase is advanced by 90 degrees from the line voltage E _SR input as the reference voltage is the imaginary part of I _{0 in} FIG. 3 which is a vector diagram and Expression (10). , Can be expressed by the following formula (12).
B = IgrT−0.5IgrR−0.5IgrS + 0.5√3 (IgcR−IgcS)
(12)
Here, if the phase angle between the zero-phase current I ₀ and the reference voltage √3E is θ, the effective component A is represented by I ₀ cos θ, and the ineffective component B is I It is represented by ₀ sin θ.

Meanwhile, the active ingredient A of the zero-phase current I _0, when the determined by measuring the value of the reactive component B actually, the reference voltage √3E and the zero-phase current inputted to the basic processing unit 3 of the processing operation section 16 I ₀ 5, the phase lag between the reference voltage √3E and the zero-phase current I ₀ is measured, and the zero-phase current I ₀ is made the same as the reference voltage √3E by the calculation unit 14 as shown in FIG. The output is decomposed into an effective component A of phase and an ineffective component B whose phase is advanced by 90 degrees from the reference voltage √3E. That is, the calculation unit 14 detects the effective component A and the ineffective component B based on the phase angle θ between the reference voltage √3E and the zero-phase current I ₀ .

next,
X = B−√3A (13)
Y = B + √3A (14)
Z = -2B (15)
Then, substituting A and B in the above equations (11) and (12) into the above equations (13) to (15), the following equations (16) to (18) are obtained.

X = IgrT + IgrS−2IgrR + √3 (IgcT−IgcS) (16)
Y = IgrR + IgrT−2IgrS + √3 (IgcR−IgcT) (17)
Z = IgrS + IgrR−2IgrT + √3 (IgcS−IgcR) (18)
Here, in the three-phase power distribution system, assuming that the leakage current Igr does not flow simultaneously in each of the three phases, −2IgrR in the above equation (16), −2IgrS in the equation (17), and the equation (18). -2IgrT part of E.c. is erased, and when the values of IgcR, IgcS, and IgcT are in a balanced state, the values of X, Y, and Z are measured values of Igr when the leakage current Igr flows in one phase, Or the value of the leakage current Igr of the two phases total when the leakage current Igr flows in two phases is shown.

  Therefore, the maximum value among the values of X, Y, and Z expressed by the above formulas (13) to (15) is the measured value of the one-phase leakage current Igr or the total measured value of the two-phase leakage current Igr, Further, it is output as a measured value of the ground leakage current Igr corresponding to the ground leakage resistance generated during the line load described later.

In the above description of formula (1) portion which includes to (18), although the line voltage E _SR generated between the terminal S and the terminal R was a reference voltage, the other line voltage E _TS, E _RT The above formulas (13) to (15) can be applied in the same manner even if the reference voltage is used as the reference voltage, and only the combinations of X, Y, Z in the formulas (16) to (18) and the formulas on the right side thereof are interchanged. Since the leakage current Igr is the same value with the maximum value as the measurement value of the leakage current Igr, the same measurement result can be obtained regardless of which phase voltage of the three-phase line voltage is input. Therefore, the selection error of the input voltage at the time of measurement does not occur.

  From the above-mentioned formulas (16) to (18), the measured value of the leakage current Igr represents the measured value when one phase or two phases are grounded in the distribution line or its connection terminal. It will be described below that the same equations (16) to (18) can be applied to the measurement of the ground leakage current Igr even when it occurs in a load that straddles.

For example, between the R-phase and S-phase two wires having a ground voltage of E with respect to the grounded neutral point N of the secondary winding of the star connection transformer in which the secondary winding is connected in a star shape When the line load center point M which is the center point of the load transformer coil connected to the ground is grounded through the leakage resistance r, the magnitude of the ground voltage E _NM with respect to the ground point N of the line load center point M is As is apparent from the vector diagram of FIG. 2, the leakage current to ground is 0.5 E / r, and the conventional leakage current measuring device in which the value of the zero-phase current I ₀ is the leakage current Igr is as follows: Measure this value.

  However, if the ground fault occurs not at the line load center point M but near the terminal R or S where the ground voltage is E, the ground leakage current becomes E / r, and the line load center becomes equal to the same leakage resistance r. The measured value of the ground leakage current due to the ground fault at the point M is half of this value. Therefore, in a leakage current measuring apparatus that evaluates the degree of electric leakage failure with the ground leakage current value at the rated voltage, the degree of failure is underestimated. As a result, it is difficult to accurately find a leakage fault, and it may not be possible to find an accident due to leakage while measuring leakage current.

In the present invention, the measured value of the leakage current Igr obtained by dividing the ground voltage E by the value of the ground leakage resistance r is not the measured value of the leakage current Igr that shows an excessively small value as described above. It is verified by using the above-described equations (1) to (15) that the measured value is doubled. The value of the line voltage E _SR generated between the terminal R and the terminal S of the secondary winding becomes √3E when the value of the ground voltage is E, the three-phase distribution line 4 _R, 4 Each ground capacitance C _R , C _S , C _T existing in _{S 1} , 4 _T and the load facility 5 connected thereto is verified as being equal.

First, when the ground leakage resistance r exists only at the line load center point M, the ground voltage E _{NM with} respect to the grounding point N of the line load center point M is −j0.5E. ground leakage current _{I NM} passing through ground leakage resistance r from, -j0.5E / r, IgrR, a IGRS, IGRT all 0, all ground current IGCR, IgcS, the value of IgcT equal. If this is substituted into the above-mentioned formulas (10) to (12), A becomes 0 and B becomes -0.5 E / r. Substituting these A and B into the aforementioned equations (13) to (15), X and Y are both -0.5 E / r, Z is E / r, and the maximum value E of X, Y, and Z is E. / R is displayed as a measured value of the leakage current Igr, that is, a ground leakage current value at the rated voltage. In the leakage current measuring apparatus according to the present invention, the ground leakage current value is displayed on the display unit 15 of the processing calculation unit 16.

  Next, when the ground leakage resistance r exists in the R phase and the S phase, A is 0 and B is -E / r. When A and B are substituted into equations (13) to (15), X and Y are both -E / r, Z is 2E / r, and the maximum value 2E / r of X, Y, and Z is R It is displayed as a measured value of the total leakage current Igr of the phase and S phase. This display is also performed on the display unit 15 of the processing calculation unit 16.

Next, the value of √3 or less on the right side of X, Y, and Z in the above-described equations (16) to (18) becomes 0 because IgcR, IgcS, and IgcT are equal in the balanced state, and X, Y, The maximum value of Z is the above-mentioned Igr measurement value, but since the values of the ground currents IgcR, IgcS, and IgcT are not equal in the unbalanced state, the value of √3 times the difference between them is the unbalanced state. Is included in the measured value of leakage current Igr. Hereinafter, the value resulting from the unbalanced state is obtained from the value of the zero-phase current I ₀ .

The value of the zero phase current I ₀ can be expressed by the following equation (19) from the values of A and B in the equations (11) and (12).

I ₀ ² = A ² + B ²
= IgrR (IgrR-IgrS) + IgrS (IgrS-IgrT) + IgrT (IgrT-IgrR) + (IgcR + √3IgrT) (IgcR−IgcS) + (IgcS + √3IgrR) (IgcS + IgT) (IgC + IgT) (IgC + IgT) IgcR) (19)
In this equation (19), when the leakage currents IgrR, IgrS, and IgrT are set to 0, the value of the zero-phase current I ₀ is as shown in the following equation (20).

I ₀ ² = IgcR (IgcR−IgcS) + IgcS (IgcS−IgcT) + IgcT (IgcT−IgcR) (20)
Here, in order to obtain the minimum value of the zero-phase current I ₀ , if the IgcR in the equation (20) is differentiated as a variable and set to 0, the condition of the following equation (21) is obtained.

IgcR = 0.5 (IgcS + IgcT) (21)
Next, when the formula (21) is substituted into the formula (20), the following formula (22) is obtained as the minimum value of the zero-phase current I ₀ .

I ₀ = (√3 / 2) (IgcT−IgcS) (22)
Then, substituting the result of equation (22) into equation (16) yields the following equation (23).

X = IgrT + IgrS−2IgrR + 2I ₀ (23)
Leakage current Igr is no current flows three phases at the same time, it deletes the formula (23) in its (-2IgrR), IgcS, calculates the minimum value of the zero-phase current _{I 0} to IgcT as a variable, as a result Is substituted into the equations (16) to (18), the following equations (24) to (26) are obtained.

X = IgrT + IgrS ± 2I ₀ (24)
Y = IgrR + IgrT ± 2I ₀ (25)
Z = IgrS + IgrR ± 2I ₀ (26)
From the equations (24) to (26), the static electricity generated in each of the three-phase R, S, and T phases as described above in the measured value of the leakage current Igr that is the maximum value of X, Y, and Z. When the values of the capacitances C _R , C _S , and C _T are in different unbalanced states, ± 2I ₀ that is a value that affects the measured value of the leakage current Igr is included.

Note that the value of 2I _{0 in} the above formulas (24) to (26) is a value that the zero-phase current I ₀ is obtained under the minimum condition, but under other conditions, a value that is smaller than twice, for example, the ground current IgcS , IgcT is 0, it indicates √3 times, so twice the maximum value is the limit value.

Since the value of the zero-phase current I ₀ is a basic measurement value, the measurement value of the leakage current Igr can be corrected with a value of ± 2I ₀ , but the value of the zero-phase current I ₀ is excessive. In such a case, the degree of imbalance is excessive, and the reliability of the measured value of the leakage current Igr is lowered.

In the explanation using the above-mentioned formulas (1) to (26), any one of the line voltages E _SR , E _TS , E _RT generated between the terminals R, S, T of the secondary winding is used as the reference voltage. However, when the ground voltages E _R , E _S , and E _T generated with respect to the neutral point N that is the grounding point are input as reference voltages, the same results can be obtained with the same theory. Can do. For example, ground voltage E _R and the zero-phase current I ₀ active ingredients A _S of the same phase input as a reference voltage E can show by the following equation (27).

A _S = IgrR−0.5IgrS−0.5IgrT + 0.5√3 (IgcS−IgcT)
... (27)
The reactive component B _S of the zero-phase current I ₀ whose phase has advanced by 90 degrees from the reference voltage E can be expressed by the following equation (28).
B _S = 0.5√3 (IgrT−IgrS) + IgcR−0.5IgcS−0.5IgcT
... (28)
Also,
X _S = A _S −√3B _S (29)
Y _S = A _S + √3B _S (30)
Z _S = -2A _S (31)
Then, the following formulas (32) to (34) are obtained by substituting A _S and B _S of the formulas (27) and (28) into the formulas (29) to (31).

X _S = IgrR + IgrS−2IgrT + √3 (IgcS−IgcR) (32)
Y _S = IgrR + IgrT−2IgrS + √3 (IgcR−IgcT) (33)
Z _S = IgrS + IgrT−2IgrR + √3 (IgcT−IgcS) (34)
The maximum value among the values of X _S , Y _S , and Z _{S represented by} the above formulas (32) to (34) is generated during the sum of one phase or two phases, or during line load, resulting in ground leakage resistance. The corresponding measured value of the ground leakage current Igr is equal to one of the right sides of the equations (16) to (18) representing X, Y, and Z. Since the maximum value among them is the value of the leakage current Igr, the value of the leakage current Igr is the same.

Next, a specific configuration of the fundamental wave processing unit 3 configuring the processing calculation unit 16 illustrated in FIG. 1 will be described with reference to FIG. The fundamental wave processing unit 3 includes a voltage detector 21, a first amplifier 22, a first low-pass filter (LPF) 23, a first effective value converter 28, and a zero-phase current (I ₀ ) detection. 24, a second amplifier 25, a second low-pass filter (LPF) 26, a second effective value converter 29, and a phase difference measuring device 27.

In FIG. 4, the voltage detector 21 includes any of line voltages E _SR , E _TS , E _RT generated between the terminals R, S, T of each phase of R, S, T, or a transformer winding. Any of the ground voltages E _R , E _S and E _T generated between the terminals R, S and T of the line and the neutral point N is input as a reference voltage. Here, when a value when any one of the ground voltages E _R , E _S , and E _T is used as a reference voltage is E, the line voltages E _SR and E _TS generated between the terminals R, S, and T are described above. , the value when the reference voltage of either of the E _RT is a √3E.

In the system diagram shown in FIG. 1, a line voltage _ESR is input. Then, the first amplifier 22 amplifies the reference voltage output from the voltage detector 21 according to the detection sensitivity of the voltage detector 21 until it reaches an appropriate value. The first low-pass filter 23 attenuates a frequency component that exceeds the fundamental frequency, which is the frequency of the voltage input as the reference voltage, and extracts a reference voltage fundamental frequency waveform.

The zero-phase current detector 24 is a vector sum of currents flowing through the distribution lines 4 _R , 4 _S , and 4 _T of the R, S, and T phases in the three-phase three-wire distribution system. A certain zero-phase current I ₀ is input. In addition, in the three-phase four-wire distribution system, four wires of R, S, T and N-phase distribution wires 4 _R , 4 _S , 4 _T and neutral wire 4 _N are grounded phases. A zero-phase current I _0, which is a vector sum of currents flowing through, is input. The second amplifier 25 amplifies the zero phase current I ₀ output from the zero phase current detector 24 according to the detection sensitivity of the zero phase current detector 24 until it reaches an appropriate value. The second low-pass filter 26 extracts a fundamental frequency waveform by attenuating frequency components exceeding the fundamental frequency of the zero-phase current I ₀ .

Then, the phase difference measuring device 27 is one of the line voltages E _SR , E _TS , E _RT generated between the terminals R, S, T inputted as the reference voltage, the winding 1a of the three-phase transformer, The phase difference between any one of the ground voltages E _R , E _S and E _T generated with respect to the neutral point N which is the ground point of 1b and 1c and the zero-phase current I ₀ is measured. Here, any of the line voltages E _SR , E _TS , E _RT generated between the terminals R, S, T inputted as the reference voltage E, and the ground point of the windings 1a, 1b, 1c of the three-phase transformer FIG. 5 shows the phase difference between any one of the ground voltages E _R , E _S , E _T generated with respect to the neutral point N and the zero-phase current I ₀ . In the fundamental wave processing unit 3, the first low-pass filter 23 inputs the waveform of the output reference voltage E and the waveform of the zero-phase current I ₀ output from the second low-pass filter 26 to, for example, an operational amplifier zero crossing circuit. Then, their output waveform, as shown in FIG. 5, is as shown in E _Z is the reference voltage E, is shown in I _Z for zero-phase current I _0. The peak values of the output waveforms of the reference voltage E and the zero-phase current I ₀ are matched to obtain the difference between the output waveforms E _Z and I _Z. The absolute waveform of the difference is the | E _Z -I _Z | waveform shown in FIG. If the areas of the protruding portions of the | E _Z −I _Z | waveform and the I _Z waveform shown in FIG. 5 are respectively S ₁ and S ₂ , S ₁ is the phase difference angle θ between the reference voltage E and the zero-phase current I _0. proportional to, _{S 2} is proportional to the phase difference of 180 degrees. The voltage proportional to S ₁ and S ₂ is output to the calculation unit 14.

Then, the first effective value converter 28 rectifies the fundamental frequency waveform of the reference voltage E into both waves, converts it to an analog value proportional to the effective value, and inputs it to the calculation unit 14. The second effective value converter 29 rectifies the fundamental frequency waveform of the zero-phase current I ₀ into both waves, converts it to an analog value proportional to the effective value, and inputs the analog value to the computing unit 14.

Then, the calculation unit 14 uses the phase difference angle θ between the reference voltage E measured by the phase difference measuring instrument 27 and the zero-phase current I ₀ to convert the zero-phase current I ₀ into an active component A having the same phase as the reference voltage E. And the ineffective component B whose phase is advanced by 90 degrees from the reference voltage E.

The phase difference angle θ between the reference voltage E detected by the phase difference measuring instrument 27 and the zero-phase current I ₀ is calculated from the following equation (35).

θ = (180S ₁ ) / S ₂ (35)
Here, the calculation unit 14 calculates and outputs the value of I ₀ cos θ as the value of the effective component A of the zero-phase current I ₀ and the value of I ₀ sin θ as the value of the invalid component B of the zero-phase current I ₀ . These zero-phase current I _0, the relationship of the active ingredient A and reactive component B of the zero-phase current I _0, as described above, is expressed as shown in the vector diagram of FIG.

Then, the arithmetic processing unit 14 performs the arithmetic processing as described above, and the ground leakage resistances rR, rS, rT of the R, S, and T phases are present in a load that spans one phase, two phases, or two phases. The current value flowing in them or the total current value for two phases is measured as the value of the leakage current Igr, and the value is displayed on the display unit 15 as necessary. Further, the calculation unit 14 is caused by the unbalance of the ground capacitances C _R , C _S , and C _T included in the current values flowing in the ground leakage resistances rR, rS, and rT of the R, S, and T phases. An unbalance difference current value is calculated and measured, and this value is displayed on the display unit 15 as necessary.

In the leakage current measuring apparatus and the measuring method using this measuring apparatus according to the present invention, the effective component A and the ineffective component B of the above-described zero-phase current I ₀ are expressed by the above-described equations (13) to (15) or (29 ) To (31) are performed by the calculation unit 14 so that the ground leakage resistances rR, rS, rT of each phase of R, S, T are 1 phase, 2 phases, or a load that spans between 2 phases. When present, measurement of the value of the current flowing through them or the total current value for two phases is realized. In addition, the value of ± 2 times the value of the above-described zero-phase current I ₀ is set to the value of the ground capacitance C _R , C _S , C _T included in the current value flowing through the ground leakage resistances rR, rS, rT. Measurement of the unbalance difference current value due to the balance is realized.

  In addition, as shown in FIG. 6, the leakage current measuring apparatus according to the present invention is provided with a circuit breaker 19 in the middle of the distribution line 4 and controls the circuit breaker operation according to the calculation result of the calculation unit 14. Also good. The leakage current measuring apparatus according to the present invention uses, as a control signal, the measurement result of the leakage current Igr flowing through the ground leakage resistances rR, rS, rT calculated and measured by the calculation unit 14, and is distributed based on this control signal. By operating the circuit breaker 19 provided in the middle of the electric wire 4, the distribution line 4 and the load facility 5 are interrupted from the power supply unit.

  In the leakage current measuring apparatus according to the present invention, by providing the circuit breaker 19 as described above, the distribution line 4 and the load facility 5 are connected together with detection of the leakage current Igr when the leakage current Igr exceeds a predetermined value. Since the power supply unit can be cut off, the three-phase three-wire or three-phase four-wire power distribution circuit and the load equipment connected to the power distribution circuit can be protected from a serious accident due to poor insulation.

  Furthermore, in the leakage current measuring apparatus according to the present invention, when it is determined that the value of the leakage current Igr caused by the ground insulation resistance is larger than a predetermined value based on the calculation result of the calculation unit 14, The alarm device 18 such as sound or light emission may be operated using the determination signal as a control signal, and an alarm may be issued using sound or light emission. By providing such an alarm device 18, it is possible to reliably prevent an accident due to electric leakage. As shown in FIG. 6, the alarm device 18 is operated using the determination signal of the calculation unit 14 as a control signal. Therefore, the calculation unit 14 is input so that the determination signal from the calculation unit 14 is input. 14.

  The leakage current measuring apparatus and measuring method according to the present invention are used for insulation measurement in distribution systems and electrical equipment adopting the 400 V class star distribution system widely adopted in the world distribution system as an international standard system.

It is a schematic system diagram which shows the structural example which applied the leakage current measuring apparatus which concerns on this invention to the measurement of the leakage current Igr of the distribution line distributed by a three-phase star-shaped power supply, and this load distribution line. FIG. 5 is a vector diagram showing the relationship of the ground voltage E _NM to the ground point N of the ground voltage N _R , E _S , E _T , line voltages E _SR , E _TS , E _RT and the load center point M of the star power system is there. Shows zero-phase current I _0, ground voltages E _R or the line voltage is input as a reference voltage E _SR, phase angle theta, the active ingredient A of the zero-phase current I _0, the zero-phase current I ₀ the relation reactive component B It is a vector diagram. It is a block diagram which shows the detail of the signal processing part which comprises the leakage current measuring apparatus which concerns on this invention. The relationship between the waveform of the input voltage E and the zero-phase current I _{0 having} a phase difference of θ and the output waveform of the zero-crossing circuit for phase determination is shown. It is a block circuit diagram which shows an example of the arrangement configuration which has arrange | positioned the circuit breaker and the alarm device in the leakage current measuring apparatus which concerns on this invention.

Explanation of symbols

1 Star Distribution Power Supply, 3 Fundamental Wave Processing Unit, 4 _R , 4 _S , 4 _T Distribution Line, 4 _N Neutral Line, 5 Load Equipment, 8 Grounding Line 9 Zero Phase Current Transformer, 14 Arithmetic Unit, 15 Display Unit , 16 processing computation section, 18 alarm device, 19 _{breaker, C R, C S, C} T capacitance to ground, rR, rS, rT ground leakage resistance

Claims (12)

Three-phase 4 fed from a power source with the secondary winding of the transformer connected in a star shape, the three-phase voltage terminals R, S, T, and the neutral point grounded in the star connection N In the leakage current measuring device for measuring the leakage current Igr caused by the ground insulation resistance of the electric circuit and the electrical equipment of the wire type or the three-phase three-wire type distribution system,
The line voltages E _SR , E _TS , E _RT generated between the terminals R, S, T of the secondary winding and between the terminals R, S, T of the secondary winding and the neutral point N Voltage detecting means for measuring any of ground voltages E _R , E _S , E _T generated in
Zero-phase current detection means for detecting a zero-phase current I ₀ that is a vector sum of currents flowing through the three-phase distribution lines;
Any of the voltage line voltages E _SR , E _TS , E _RT or the ground voltages E _R , E _S , E _T detected by the voltage detection means is input, and any of the input voltage lines Phase comparison means for comparing voltages E _SR , E _TS , E _RT or ground voltages E _R , E _S , E _T with a reference voltage and comparing the phase of this reference voltage with the zero phase current I ₀ ;
With respect to the reference voltage, a measurement value obtained by separating the zero-phase current I ₀ into an in-phase active component A and an ineffective component B having a phase difference perpendicular to the same is obtained, and between the terminals R, S, T line voltage _E SR _{generated, E TS,} E _RT or above the terminals R, S, ground voltages _E R generated between T and the neutral point _N, E S, when a reference voltage of either of the _{E T} The leakage current Igr generated in two phases of the R phase, the S phase, and the T phase based on the effective component A of the zero phase current I ₀ obtained in FIG. Of the leakage current Igr generated in one of R phase, S phase, and T phase, the load connected between two or three phases of R phase, S phase, and T phase A leakage current measuring apparatus comprising: a calculation means for calculating the value of the leakage current Igr generated in When the E value at the time of the ground voltage E _R, E _S, a reference voltage of either of E _T generated between each terminal R, S, T and the neutral point N, each terminal R , S, T, when any of the line voltages E _SR , E _TS , E _RT is used as a reference voltage, the value of this reference voltage is set to √3E and the phase comparison with the zero phase current I ₀ is performed. 2. The leakage current measuring apparatus according to claim 1, wherein the leakage current Igr is calculated. The arithmetic means has the value of the equation (B−√3A) when any of the line voltages E _SR , E _TS , E _RT generated between the terminals R, S, T is used as a reference voltage, The maximum value among the values of the formula (B + √3A) and the formula (−2B) is the leakage caused by the ground insulation resistance of the electric circuit connected to each terminal of the R, S, and T and the entire electrical equipment. The leakage current measuring device according to claim 1, wherein the leakage current measuring device is calculated as a current Igr. The calculating means, when the respective terminals R, S, ground voltages _E R generated between T and the neutral point _N, E S, one of _{E T} as a reference voltage, wherein the (A-√3B) Value, the value of the formula (A + √3B), and the maximum value of the value of the formula (−2A) are caused by the ground insulation resistance of the electric circuit connected to the R, S, and T terminals and the entire electrical equipment. The leakage current measuring apparatus according to claim 1, wherein the leakage current is calculated as a leakage current Igr. The arithmetic means is caused by a mismatch in the value of the ground capacitance of the electric circuit and / or electric device connected to each terminal of the R, S, T included in the leakage current Igr, or each phase of one of them. The leakage current measuring device according to claim 3 or 4, wherein the current value is calculated as a value between (-2I ₀ ) and (2I ₀ ).   The leakage current measuring device according to claim 1, further comprising a display unit, wherein a result calculated by the calculating unit is displayed on the display unit. .   The leakage current measuring device further comprises an alarm means, and issues an alarm from the alarm means when the value of the leakage current Igr required by the arithmetic means exceeds a predetermined value. 5. The leakage current measuring device according to any one of 5 above.   2. The leakage current measuring apparatus further comprises a breaking means, and the electric circuit is cut off by the breaking means when a value of the leakage current Igr obtained by the computing means exceeds a predetermined value. The leakage current measuring device according to any one of? 7. Three-phase 4 fed from a power source with the secondary winding of the transformer connected in a star shape, the three-phase voltage terminals R, S, T, and the neutral point grounded in the star connection N In the leakage current measuring method for measuring the leakage current Igr caused by the ground insulation resistance of the electric circuit and the electrical equipment of the wire type or the three-phase three-wire type distribution system,
The line voltages E _SR , E _TS , E _RT generated between the terminals R, S, T of the secondary winding and between the terminals R, S, T of the secondary winding and the neutral point N A voltage detection step of measuring any of ground voltages E _R , E _S , E _T generated in
A zero-phase current detection step of detecting a zero-phase current I ₀ which is a vector sum of currents flowing through the three-phase distribution lines;
Any of the line voltages E _SR , E _TS , E _RT or the ground voltages E _R , E _S , E _T detected by the voltage detection step is input, and any of the input line voltages E A phase comparison step of comparing _SR , E _TS , E _RT or ground voltages E _R , E _S , E _T with a reference voltage and comparing the phase of this reference voltage with the zero phase current I ₀ ;
With respect to the reference voltage, a measurement value obtained by separating the zero-phase current I ₀ into an in-phase active component A and an ineffective component B having a phase difference perpendicular to the same is obtained, and between the terminals R, S, T line voltage _E SR _{generated, E TS,} E _RT or above the terminals R, S, ground voltages _E R generated between T and the neutral point _N, E S, when a reference voltage of either of the _{E T} The leakage current Igr generated in two phases of the R phase, the S phase, and the T phase based on the effective component A of the zero phase current I ₀ obtained in FIG. Of the leakage current Igr generated in one of R phase, S phase, and T phase, the load connected between two or three phases of R phase, S phase, and T phase A method for measuring leakage current, comprising: a calculation step of calculating a value of the leakage current Igr generated in . When the E value at the time of the ground voltage E _R, E _S, a reference voltage of either of E _T generated between each terminal R, S, T and the neutral point N, each terminal R , S, T, when any of the line voltages E _SR , E _TS , E _RT is used as a reference voltage, the value of this reference voltage is set to √3E and the phase comparison with the zero phase current I ₀ is performed. 10. The method for measuring leakage current according to claim 9, wherein the leakage current Igr is calculated. In the calculation step, when any one of the line voltages E _SR , E _TS , and E _RT generated between the terminals R, S, and T is used as a reference voltage, the value of the formula (B−√3A), The maximum value among the values of the formula (B + √3A) and the formula (−2B) is the leakage caused by the ground insulation resistance of the electric circuit connected to each terminal of the R, S, and T and the entire electrical equipment. The leakage current measuring method according to claim 9 or 10, wherein the leakage current is calculated as a current Igr. In the calculation step, when any one of the line voltages E _SR , E _TS , and E _RT generated between the terminals R, S, and T is used as a reference voltage, the value of the formula (B−√3A), The maximum value among the values of the formula (B + √3A) and the formula (−2B) is the leakage caused by the ground insulation resistance of the electric circuit connected to each terminal of the R, S, and T and the entire electrical equipment. The leakage current measuring method according to claim 9 or 10, wherein the leakage current is calculated as a current Igr.

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