JP2009229211A - Leakage current measuring device and its measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure a total value Igr of leakage current which passes through a distribution wire where power is supplied from a 400 V class star distribution power source and a ground insulation resistance of a load facility connected to the distribution wire. <P>SOLUTION: Signal processing is performed for any one of one-phase ground voltages of Er, Es, Et among three-phase ground voltages inputted from the star distribution power source 1 and a zero-phase current I<SB>0</SB>detected from the distribution wire 4 by a zero-phase transformer 9, and any one of the one-phase ground voltages Er, Es, Et is inputted. A signal processing part 14 performs signal processing by measuring the phase difference between the input voltage and zero-phase current I<SB>0</SB>. The phase angle of the zero-phase current I<SB>0</SB>obtained by the signal processing part 14 with respect to the input voltage is computed. With it and the value of the zero-phase current I<SB>0</SB>, an effective component A and a reactive component B with respect to the input voltage are computed. From these effective values, the total leakage current value Igr of each phase except one sound phase which passes through a ground leakage resistance 7 and its reliability are computed. The maximum value and the minimum value of the leakage current Igr computed by a computing part 15 and further the leakage current value Igr are displayed on a display part 16. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric circuit for supplying power from a power source, an electric circuit for measuring a leakage current flowing from a voltage application portion of an electric device connected to the power source to a ground portion, a leakage current measuring device in the electric device, and a measuring method thereof.

  The use of electricity is convenient, but if it is not properly managed and used, it also has very dangerous aspects, and there are many possibilities of causing serious accidents such as electric fires and electric shocks. For example, one of the causes of the serious accident is an insulation failure of an electric circuit or an electric device. As a method of examining the insulation state of the electric circuit and the electric device, a method of measuring the electric circuit and electric device to be measured with a power failure and measuring with an insulation resistance meter has been a conventional standard.

  As in recent years, there are drawbacks such as restrictions on application to distribution lines where continuous power failure is not permitted, continuous operation factories, and the like. In other words, in the current social situation, computers are used in various areas of society, and a system that operates continuously for 24 hours has been constructed by the spread of intelligent buildings and factory automation (FA). In order to investigate, it is in a situation where it cannot temporarily be brought into a power failure state.

  Therefore, at present, due to the demand for uninterruptible society due to such advanced informationization, leakage current measurement that can measure without insulation failure from the method of insulation resistance meter with electric power failure management of insulation failure of electric circuits and electrical equipment. A method is being used. And various preventive measures during energization in which the leakage current is measured by an earth leakage breaker, an earth leakage fire alarm, or the like and the insulation state is managed have been proposed.

As an example, there is a power distribution measurement method in which one of 200 V three-phase three wires is grounded. This measurement method detects a leakage current from the voltage application part to the grounding part of the electric circuit and electrical equipment, that is, a zero-phase current I ₀ , and determines a phase difference between the zero-phase current I ₀ and the line voltage. Based on this, the leakage current flowing through the insulation resistance between the voltage application portion and the grounding portion of the electric circuit and the electric equipment, which is a measure of insulation failure, is calculated.

  This method has been increasingly adopted by large-scale customers in recent years, and 400V class three-phase power is supplied from a power source in which the low-voltage three-phase winding of a transformer, which has become the standard for overseas power distribution systems, is connected in a star shape. It cannot be applied to insulation measurements on 4-wire or three-phase, three-wire distribution systems (hereinafter referred to as star distribution systems) electrical lines and equipment. Another method is to measure the leakage current by applying a low frequency low voltage to the power distribution system, but this device is heavy and expensive.

Also, in the star distribution system, the zero-phase current I ₀ is measured by a zero-phase current transformer with a ground wire or four or three distribution lines at once, and this value is taken as the value of the leakage current flowing through the insulation resistance. A method of monitoring insulation has been implemented. In this method, the value of the ground capacitance existing between the voltage application part and the grounding part of the electric circuit or electrical equipment is the same for all three phases (this state is called a balanced state), and the leakage current is limited to one phase. When present, it shows a normal value. However, when the ground capacitance value is different for each of the three phases, or when one of the three phases is different (this state is called an unbalanced state), the leakage current is two-phase or Accurate measurement cannot be performed when it occurs inside a winding or an electric circuit of an electric equipment connected between so-called lines between two phases.

  The star-type power distribution system has a line voltage between about 480V and 380V and a large distribution capacity and scale. The degree of danger to be generated is also great. In addition, it is necessary to connect a grounding wire to the instrument, and it is difficult to find the grounding location depending on the measurement site, and the measurement itself becomes impossible.

As prior art documents of this type of leakage current measuring apparatus, there are the following.
JP-A-3-179271 JP 2002-125313 A JP 2007-318840 A

  In the present invention, leakage current flowing through the ground insulation resistance of a load facility such as a power supply line adopting a star-shaped power distribution system or an electric device connected to the power supply line is safely kept in an energized state, and the value of the ground capacitance is three. It is an object of the present invention to provide a leakage current measuring device and a measuring method thereof that can detect an error even in an unbalanced state where each phase is different or one of three phases is different.

In order to solve the above-described problem, the leakage current measuring apparatus according to the present invention is configured to input a voltage to the ground voltage of one phase of each phase of the power source of the star distribution system and measure the zero-phase current. The measuring means measures the zero-phase current I ₀ , which is a ground leakage current flowing from the power source through the power supply line and the load equipment such as electric equipment connected to the power supply line, and the signal processing means measures by the zero-phase current measuring means Based on the zero-phase current I ₀ , the effective component which is the component in the same phase direction as the ground voltage input by the star distribution power source measured by the voltage measuring means, and the invalid component of the phase difference of 90 degrees are calculated. and, calculating means of the signal active ingredients and reactive components with respect to the input voltage of the zero-phase current I ₀ which is calculated by the processing means, it zero-phase current I ₀ to the value of the voltage input by the voltage measuring means or set voltage Feed from value The leakage current that flows through the ground insulation resistance to the wire and the electrical equipment connected to this feeder distribution line is calculated, and the calculation means calculates the load of the feeder line, electrical equipment, etc. from the value of the zero-phase current I ₀ and the leakage current value. This is due to the unbalanced state where the value of the ground capacitance existing between the voltage application part and the grounding part of the equipment is different in each of the three phases or one of the three phases is different. The degree of influence of the leakage current on the total value Igr of the leakage current flowing through the ground insulation resistance of each phase is calculated.

In order to solve the above problems, the leakage current measuring method according to the present invention inputs and measures one-phase ground voltage of the star-type power distribution system power supply in the voltage measuring step, and the zero-phase current measuring step above A zero-phase current I ₀ that is a ground leakage current that flows from a power source through a power supply line and a load facility such as an electric device connected to the power supply line is measured, and the zero-phase current I measured in the zero-phase current measurement step in the signal processing step. _{From 0} , the effective component which is a component in the same phase direction as the ground voltage to which the power supply of the star distribution system measured in the voltage measurement step is input, and the invalid component of the phase difference of 90 degrees are calculated. From the effective component and the ineffective component with respect to the input voltage of the zero-phase current I ₀ calculated in the signal processing step, and the value of the zero-phase current I ₀ and the voltage input in the voltage measurement step or the set voltage value The leakage current flowing through the ground insulation resistance to the power supply line and the load equipment such as electric equipment connected to the power supply line is calculated, and the value of the zero-phase current I _{0 and} the value of the leakage current are calculated in the calculation process. Unbalance in which the value of the ground capacitance existing between the voltage application part and the grounding part of load equipment such as equipment is different in each of the three phases, or one of the three phases is different. The degree of influence of the leakage current due to the state on the total value Igr of the leakage current flowing through the ground insulation resistance of each phase is calculated.

  By the way, a power supply line that is a three-phase distribution line connected to a power supply of a star distribution system to which a leakage current measuring apparatus and method to which the present invention is applied is applied, and an electric device as a load facility connected to the power supply line. The ground voltage of the power supply terminal is a three-phase voltage having the same magnitude with a phase difference of 120 degrees.

  And the 400V class three-phase three-wire distribution system using a star-shaped distribution power source in which the low-voltage three-phase windings of the transformer are connected in a star shape is used to supply power to electrical equipment in large factories and plant facilities. The ground capacitance existing between the part to which the voltage is applied and the metal part or ground grounded over the part is usually almost the same value for each of the three phases, that is, in a balanced state.

  However, if the electrical equipment as the load equipment connected to the power supply of the star distribution system includes a single-phase large-capacity load such as a welding transformer, or a single-phase such as a lighting load, or a three-phase such as a power load In the case of 400V class three-phase three-wire distribution system, the value of the ground capacitance existing between the voltage application part and the ground part of the electric circuit or electrical equipment is different in each of the three phases, or three It is necessary to consider the degree of the influence of the leakage current due to the unbalanced state in which one phase is different among the phases on the total value of the leakage current of each phase flowing through the ground insulation resistance.

  By the way, when the voltage supplied from the power supply of the star distribution system is applied to the grounded electrostatic capacitance in a balanced state, the current flowing through the grounding electrostatic capacitance of each phase is the same and the phase difference is different by 120 degrees. The total current value of the phases is 0, but in the unbalanced state as described above, the current value of the ground capacitance synthesized from the three phases is large if the degree of unbalance is large.

If insulation deterioration occurs in the three-phase distribution line that is the power supply line connected to the power supply of the star distribution system and the electrical equipment as the load equipment connected to this, this leakage current flows through the ground insulation resistance. And a combined value of the current flowing through the above-described ground capacitance is measured as a leakage current. However, in the unbalanced state as described above, there is a composite value of the current flowing through the ground capacitance, and this current merges with the leakage current flowing through the ground insulation resistance to become the zero-phase current I ₀ . Therefore, this combined value current becomes a measurement error when measuring the total leakage current Igr of each phase, and furthermore, how much the combined value current leaks when measuring the total leakage current Igr of each phase. It is necessary to measure whether it is included in the measured value of the current Igr.

  In addition, the leakage current that sets the operating current value based on the leakage current value including the combined current caused by the unbalanced state without causing the insulation deterioration of the distribution line or the load equipment connected to the distribution line. In the detection device, in the unbalanced state as described above, the device malfunctions.

  In addition, the current flowing through the ground capacitance of each phase is the same in magnitude and phase difference with respect to the harmonic voltage having three times the power frequency included in the power voltage of the star distribution system and its multiple frequency. 360 degrees or a multiple thereof, the total current value for the three phases is the sum of the current values for each phase, and is added to the value of the leakage current flowing through the ground insulation resistance. Therefore, the leakage current measuring apparatus according to the present invention includes zero phase current measuring means for removing frequency components exceeding the power supply frequency, and the leakage current determining method includes a zero phase current measuring step for removing it.

By the way, in the power supply employing the star-shaped power distribution system, the neutral point of the low-voltage side star winding of the three-phase transformer for power distribution is grounded, and the three-phase terminals R, S, and T are neutral at the ground potential. Three relative ground voltages E _R , E _S , and E _T having the same magnitude and different phases by 120 degrees with respect to the point are generated.

Then, the three-phase voltage to ground E _R, E _S, to measure the ground voltage E _R of one phase in E _T, when entering the voltage on the low voltage side star windings of three-phase transformer for power distribution, this voltage Is a reference voltage E, the ground voltages E _R , E _S , and E _T of each phase are expressed by the following equations in the vector symbol method.

E _R = E (1)
E _S = −0.5E−j 0.5 / √3E (2)
E _T = −0.5E + j0.5 / √3E (3)
In addition, the ground insulation resistances r _R , r _S , r _T and the ground capacitances C _R , C _S , C _T are between the R phase, S phase, T phase and the ground portion in the star distribution system. When present, let leakage currents flowing through the ground insulation resistances r _R , r _S , and r _{T be} g _R , g _S , and g _T, and let leakage currents flowing through the ground capacitances C _R , C _S , and C _{T be} IR, IS , IT, leakage currents g _R , g _S , and g _T flowing through the ground insulation resistances r _R , r _S , and r _T are expressed by the following formulas (4) to (6), and the ground capacitance C Leakage currents IR, IS, and IT flowing through _{R 1} , C _S , and C _T are expressed by the following formulas (7) to (9).

g _R = E _R / r _R = E / r _R (4)
g _S = E _S / r _S = (− 0.5E−j0.5√3E) / r _S (5)
g _T = E _T / r _T = (− 0.5E−j0.5√3E) / r _T (6)
IR = jωC _R E _R = jωC _R E (7)
_{IS = jωC S E S = jωC} S (-0.5E-j0.5√3E) ··· (8)
_{IT = jωC T E T = jωC} T (-0.5E-j0.5√3E) ··· (9)
Then, a ground leakage current of the zero-phase current I _0, an input ground voltage E _R and the active ingredient is the same phase direction component A, disables a 90 ° phase leading direction component from the ground voltage E _R When the component is B, the zero-phase current I ₀ , the effective component A, and the reactive component B are expressed by the following equations (10) to (12) from the relationship of the equations (4) to (9). It is expressed in

_{I 0 = g R + g S} + g T + IR + IS + IT = A + jB ··· (10)
A = g _R −0.5 g _S −0.5 g _T + 0.5√3 (IS-IT) (11)
B = 0.5√3 (g _T −g _S ) + IR−0.5IS−0.5IT (12)
Also, the zero-phase current I _0, when the phase angle between the ground voltage E _R input and theta, the active ingredient A being represented by formula (13) below, the reactive component B is below formula (14 ).

A = I ₀ La cos θ (13)
B = I ₀ lasin θ (14)
The values of the effective component A and the reactive component B are measured by the one-phase, two-phase, or three-phase ground voltages measured by the voltage measuring unit and the zero-phase current measuring unit in the leakage current measuring apparatus according to the present invention. The signal processing means for calculating the phase difference between the zero-phase current and the zero-phase current is output in the signal processing step in the leakage current measuring method.

  The following calculations are performed from the above equations (11) and (12), and the results are set as U, V, and W as shown in the following equations (15) to (17).

_{g R -g S + (IR +} IS-2IT) / √3 = A + B / √3 = U ··· (15)
g _S −g _T + (IS + IT−2IR) / √3 = −2B / √3 = V (16)
g _R -g _T + (2IS-IT-IR) / √3 = A−B / √3 = W (17)
In the above equations (11) and (12), the effective component A and the ineffective component B are positive and negative values, and U, V, and W are also positive and negative values from the equations (15), (16), and (17). When the degree of imbalance is small, the values of the relational expressions of IR, IS, IT in parentheses in the equations (15), (16), (17) are small. If this value is ignored, U, V, Depending on whether the value of W is positive or negative, the magnitude relationship of the values of the leakage currents g _R , g _S , and g _T flowing through the ground insulation resistances r _R , r _S , and r _T can be known.

In the distribution system of the star distribution system, in the case of insulation failure, the leakage current Igr ₀ that is a fault current flows from the load equipment between one phase alone, two phases, or between lines, and the other phases are mostly healthy. If all three phases cause insulation failure, most are due to a short circuit accident and the overcurrent protection device operates. Even if it is not an overcurrent, the leakage currents Igr ₀ generated in the three phases cancel each other, and a normal measurement value cannot be obtained.

The nature of such power distribution system, the total value Igr leakage current Igr ₀ generated in three phases, the minimum value of the leakage current Igr ₀ 0 level, as shown in the following equation (18).

Total value Igr = maximum Igr ₀ value + intermediate Igr ₀ value (18)
From this equation (18), the following relationship is obtained.

When both U and V are positive or one is 0, g _T = 0, and the total value Igr of the leakage current Igr ₀ is expressed by the following equation (19).

Total value Igr = V + W (19)
When both U and V are negative or one is 0, g _R = 0, and the total value Igr is expressed by the following equation (20).

Total value Igr = −U−W (20)
When U is positive and V is negative or any one is 0, g _S = 0, and the total value Igr is expressed by the following equation (21).

Total value Igr = U−V (21)
When U is negative and V is positive or one of them is 0 and W is positive or 0, g _T = 0 and the total value Igr is expressed by the following equation (22).

Total value Igr = V + W (22)
When U is negative and V is positive or either one is 0 and W is negative, g _R = 0, and the total value Igr is expressed by the following equation (23).

Total value Igr value = −U−W (23)
When measuring the leakage current generated in the star-type power distribution system, it is unknown which phase of the three-phase ground voltage is input, and the phase angle θ varies in the range of 0 to 360 degrees. Since the value of the phase angle θ used in the above-described equations (13) and (14) is in the range of 0 degree to 120 degrees, when the measured phase angle θ is in the range of 0 degree to 120 degrees, it remains as it is. When the value of θ is set and the measured phase angle θ is in the range of 120 degrees to 240 degrees, the value of θ is as shown in the following equation (24).

θ = measured phase angle−120 degrees (24)
When the measured phase angle θ is in the range of 240 degrees to 360 degrees, the value of θ is as shown in the following equation (25).

θ = measured phase angle−240 degrees (25)
The above formulas (24) and (25) are equivalent to the coordinate transformation formula, that is, the input phase is switched from the R phase to the S phase and from the R phase to the T phase. The effective component A and the ineffective component B are obtained by substituting the value of θ obtained as described above into the equations (13) and (14) described above.

By substituting the value of θ obtained as described above and the value of the zero-phase current I ₀ , which is a ground leakage current, into the following equation (26), the total value Igr ₀ of the leakage current Igr ₀ generated in each phase Can be requested.

Total value Igr = 2I ₀ La cos (θ−60 degrees) (26)
In the case of an unbalanced state in which the value of the ground capacitance is different in each of the three phases or one of the three phases is different, the above-described equations (19), (20), (21) Substituting the above formulas (15), (16), and (17) for the relational expressions (27), (28), (29) of the total value Igr of the leakage current Igr ₀ generated in the following three phases: Is obtained.

g _T = 0, Igr = V + W = g _S + g _R + √3 (IS-IR) (27)
g _R = 0, Igr = −U−W = g _T + g _S + √3 (IT−IS) (28)
g _S = 0, Igr = U−V = g _R + g _T + √3 (IR−IT) (29)
Further, I ₀ ² = A ² + B ² . Equation previously described Equation (11), (12) by substituting, and ground insulation resistance _{r R,} r S, leakage currents _g R flowing _{r T, g S, g T} , capacitance to ground _C R, C _S, leakage current IR flowing in the _{C T,} iS, considering the combination of iT, relation of the zero-phase current _{I 0} as shown in the following (30), (31), (32), is (33) is obtained .

g _T = 0, I ₀ ² = (g _{R to} g _S ) ² + g _R g _S + d ² + √3 {g _R (IS−IT) + g _S (IT−IR)} (30)
g _R = 0, I ₀ ² = (g _{S to} g _T ) ² + g _S g _T + d ² + √3 {g _S (IT−IR) + g _T (IR−−IS)} (31)
g _S = 0, I ₀ ² = (g _{T to} g _R ) ² + g _T g _R + d ² + √3 {g _T (IR−IS) + g _R (IS−IT)} (32)
In this case, d is the difference in capacitance to ground _{C R,} C S, the leakage current IR flowing in the _{C T,} IS, and the maximum current value and minimum current value of IT, the ^{d 2,} the following There is a relationship as shown in Expression (33).

d ² = IR (IR−IS) + IS (IS−IT) + IT (IT−IR) (33)
The value of the ground leakage current displayed in the leakage current measuring apparatus and the measuring method according to the present invention is the total value of the two-phase ground fault currents as shown in the above-described equations (27), (28), and (29). Or, when the value of one of the two phases is 0, the value of the one-phase ground fault current is displayed, and thus a value larger than the current value of the zero-phase current I ₀ is shown.

Further, the capacitance to ground of each phase in the unbalanced state as described above C _R, C _S, the leakage current IR flowing in the C _T, IS, when the difference between the maximum current value and minimum current value IT is d, The value on the right side of the equation (33) is approximately d ² in the case of a normal power distribution system, and the value of d is an unbalanced difference current value representing the magnitude of the unbalanced state.

Therefore, ground leakage current Igr of the above relationship (27), (28), (29) and zero-phase current _{I 0} of the equation (30), from (31), (32), (33), ground It can be seen that the values of the zero-phase current I ₀ and the ground leakage current Igr, which are measured based on the phase in which the current is generated, its magnitude, the imbalance, the ground fault current distribution for each phase, etc., vary greatly.

If the distribution system is in a balanced state from the relational expressions (27), (28), (29) of the total value Igr of the leakage current Igr ₀ described above, the value of √3 or less in these expressions becomes 0, and Igr measurement The value indicates the total value of the two-phase ground leakage current Igr. If the value is unbalanced, the total value of the two-phase leakage current Igr ₀ and the ground capacitances C _R , C _S and C _T flow. A value obtained by adding a value √3 times the difference d between the maximum current value and the minimum current value of the leakage currents IR, IS, and IT is displayed. Here, when the leakage currents g _R , g _S , and g _T flowing through the ground insulation resistances r _R , r _S , and r _T are ₀ , the relational expressions (31), (32 ), (33), (from 34), the measured value of the zero-phase current _{I 0,} the capacitance to ground _{C R,} C S, the leakage current IR flowing in the _{C T,} iS, the maximum current value and minimum current value IT And the measured value of the total value Igr of the leakage current Igr ₀ from the equations (27), (28) and (29) of the total value Igr of the leakage current Igr ₀ described above. Indicates a value of √3 times the unbalance difference current value d.

Further, when the leakage currents g _R , g _S , and g _T flowing through the ground insulation resistances r _R , r _S , and r _T are 0 and the above-mentioned unbalance difference current value d is large, the displayed leakage The total value Igr ₀ of the current Igr ₀ is extremely larger than the value of the leakage current Igr ₀ flowing through the ground insulation resistance r, which is the fault current, and the ground relay operated by the displayed value of the total value Igr ₀ of the leakage current Igr ₀ This will cause a major malfunction. Further, even in the earth leakage breaker configured to detect the ground state by the value of the zero-phase current I ₀ , if the above-mentioned unbalance difference current value d is large, it causes a malfunction.

  Therefore, the leakage current measuring device and the measuring method according to the present invention use the relationship of the above-described formulas, and the value of the ground capacitance is different in each of the three phases, or one of the three phases is It aims to improve the reliability of measured values by clarifying the status of the power distribution system, such as the different unbalanced status and the degree of failure of the power distribution system. In the invention, a discriminant and a discriminant index M as shown in the following formula are used.

(Measured value Igr) / (Measured value I ₀ ) = M (34)
Based on the value of the discriminant index M obtained by the discriminant equation (34), it is possible to know the outline of the distribution system failure state and the measured value Igr bias state caused by the above-mentioned unbalanced state.

First, when the discriminant index M in the discriminant (34) is close to 1, the ground capacitance of each phase is close to the same, and the leakage current Igr ₀ flows through the ground insulation resistance of any one of the three phases. in which, the total value Igr of the leakage current, it is determined that there is little influence on the total value Igr leakage current Igr ₀ value leakage current of each phase of the earth capacitance is generated if not the same, The value Igr of the total value of the leakage current Igr ₀ is set to a value close to this or a value close to the total value Igr of the leakage current plus an upper limit value or a lower limit value.

Further, when the value of the discriminant index M of the discriminant (34) is close to 2, the ground capacitance of each phase is close to the same, and the ground insulation resistance of any two of the three phases is almost the same value. and leakage current Igr ₀ flow, impact on the total value Igr of the leakage current Igr _0, the sum Igr leakage current Igr ₀ value leakage current of each phase of the earth capacitance is generated if not identical Therefore, the value of the total leakage current value Igr is set to a value close to this or a value close to the total leakage current value Igr and an upper limit value or a lower limit value.

Further, when the discriminant index M of the discriminant (34) is close to √3, the ground capacitance of each phase is not the same, and the leakage current Igr ₀ hardly flows through the ground insulation resistance of each phase. The total value Igr is substantially occupied by a value of √3 times the measured value of the zero-phase current I ₀ , which is an influence value of the leakage current Igr ₀ that occurs when the ground capacitance of each phase is not the same. The total value Igr of the leakage current is determined to be a value close to 0 or a value close to 0 with an upper limit value or a lower limit value. Since the value of the zero-phase current I ₀ at this time coincides with the above-described value of the unbalance difference current value d, the degree of unbalance of the distribution system can be measured, and most of the number of measurements excluding the number of failures. In this state, however, considering the problem of displaying an Igr value much larger than the actual value, the reliability of the measurement is significantly improved.

Furthermore, when the discriminant index M of the discriminant (34) is between a value close to 2 and a value close to √3, and between a value close to √3 and a value close to 1, the ground static of each phase capacity is not the same, and since the current Igr ₀ leaks to ground insulation resistance is flowing, the total value Igr of the leakage current, the leakage current Igr ₀ which occurs when each phase of the capacitance to ground is not the same it is determined to contain a value, the total value Igr leakage current, and a value close thereto, or the value of the total value, depending on the value of the value or zero-phase current I ₀ of the discriminant equation (34) It is a value with an upper limit or lower limit added.

In the present invention, by the sum Igr leakage current Igr ₀ of each phase flowing through these values to each phase of the ground insulation resistance, it can significantly increase the reliability of the overall measurement.

By the way, when the distribution system of the star distribution system to which the leakage current measuring apparatus and measuring method according to the present invention is operating normally, the total value Igr of the leakage current is small and the normal 400V system. The degree of unbalance of the ground capacitance is small. Therefore, in order to determine this state, an ineffective component with respect to the three relative ground voltages of the zero-phase current I ₀ which is a ground leakage current is used. That is, it is calculated from the above-described equation (14) by the phase angle θ ₀ between the zero-phase current I ₀ that is the ground leakage current measured by the zero-phase current measuring means and the ground voltage of a certain phase that is input. The calculated B value is BR, the θ value in the above equation (14) is calculated as (θ ₀ +120 degrees), the B value is calculated as BS, and the θ value in the above expression (14) is calculated as (θ ₀ +120 degrees). When the value of B is BT, the BR, BS, and BT are expressed by the following equations (35), (36), and (37) with reference to the equation (12) described above.

BR = 0.5√3 (g _T −g _S ) + IR−0.5IS−0.5IT (35)
BS = 0.5√3 (g _R −g _T ) + IS−0.5IT−0.5IR (36)
BT = 0.5√3 (g _S −g _R ) + IT−0.5IR−0.5IS (37)
In the above formulas (35), (36), and (37), when the ground capacitance of each phase is balanced, the value after + on the right side of each formula is almost 0, and the right side of each formula is The value before + is also almost 0, and the values of BR, BS, and BT, which are the sum, are also almost 0. Further, in this balance state, when the phases of the ground insulation resistance _{r R,} r S, leakage current _g R flowing through the _{r T,} g S, is one phase or two phases of _{g T} exists, leakage currents _{g R} , G _S and g _T are increased by the value of B in the phase in which they exist. From this result, the balance state of the distribution system can be known from the value of B.

  According to the present invention, power supply in an unbalanced state in which distribution lines and electrical equipment fed by a star-shaped power supply remain in an operating state, is safe, requires less effort, and ground capacitance is uneven in three phases. Even in the system, the value of the leakage current of not only one phase but also the total of two phases can be measured with high accuracy, so the degree of insulation deterioration can be monitored constantly with minimum malfunction, and the place where insulation deterioration progresses It is possible to prevent a fault from occurring. Moreover, the reliability of the whole equipment can be remarkably improved. Furthermore, even in the periodic inspection work required by law, it is possible to save power and time for power disconnection, release the connection, and then perform reconnection, etc., and further reduce the cost.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a leakage current measuring device and a measuring method for measuring a leakage current in a distribution line to which the present invention is applied or an electric device as a load facility connected thereto will be described with reference to the drawings.

FIG. 1 is a diagram for measuring a leakage current Igr of a three-phase distribution line connected to a star-shaped distribution power source in which a low-voltage three-phase winding of a transformer is connected in a star shape and / or an electric device connected thereto. 1 shows an embodiment when the invention is applied, and a power distribution three-phase power source 1 which is a commercial frequency connects a low-voltage three-phase winding of a transformer in a star shape, and its neutral point is As shown in the voltage vector diagram of FIG. 2, the ground is connected to the point G via the grounding wire 8, and the three relative grounds having the same magnitude and different phase angles by 120 degrees with respect to the ground phase N as the neutral point. Voltages E _R , E _S and E _T are generated, and these voltages E _R , E _S and E _T are applied to the three-phase terminals R, S and T. Three-phase load and are connected three-phase terminals R, S, a T, and the distribution lines ₄ R connected to the ground phase _{N, 4 S,} 4 _T and the distribution lines ₄ R through ground line _{4 N, 4 S, 4 T} Electric power is supplied to the load equipment 5 composed of a single-phase load connected between each of the distribution lines 4 _R , 4 _S , 4 _T and the ground line 4 _N.

The present invention can also be applied to a three-phase three-wire distribution system in which a single-phase load is connected between three-phase distribution lines 4 _R , 4 _S , 4 _T and lacks a ground wire 4 _N. The same effect as when applied to a wire-type power distribution system is realized.

In the distribution system shown in FIG. 1, a ground capacitance 6 and a ground insulation resistance 7 exist between the portion to which the voltage of the distribution line 4 and the load facility 5 is applied and the ground portion. In the unbalanced state in which the value of the ground capacitance 6 is different between the three phases, or the one of the three phases is different between the portion to which the voltage is applied and the ground portion. In addition, leakage currents IR, IS, IT flow from the respective phases R, S, T to the ground portion in the ground capacitance 6 of each phase, and leakage currents g _R , g _S , g _T each flow in the ground insulation resistance 7. The phases R, S, T flow to the grounded part.

As shown in FIG. 1, the leakage current measuring apparatus according to the present invention has a three-phase structure via an electrode 3 configured to sandwich one of the distribution lines 4 _R , 4 _S , 4 _T from the outside. Is provided with a measuring instrument 17 to which a one-phase voltage is input. In order to measure the leakage currents g _R , g _S , and g _T of the distribution lines 4 _R , 4 _S , 4 _T and the load facility 5 using this leakage current measuring device, any one of the distribution lines 4 _R , 4 _S , 4T, the voltage of one phase of the three phases is input to the measuring instrument 17 via the electrode 3 configured to sandwich the _T from the outside.

This measuring instrument 17 includes the input ground voltage E _{R of} the star distribution power source 1 and the zero phase current I detected by the zero phase current transformer 9 from the distribution lines 4 _R , 4 _S , 4 _T and the ground line 4 _{N. 0} and to the signal processing, ground voltage E _R and a signal processing unit 14 for measuring and signal processing the phase difference between the zero-phase current I _0, the zero-phase current I obtained to signal processing by the signal processing unit 14 the effective value of _0, based on the phase difference between the ground voltage _{E R} and the zero-phase current _{I 0,} each phase of the ground insulation resistance _{r R,} r S, leakage current flows through the _{r T g R, g} S, It comprises a calculation unit 15 for calculating a total value Igr and confidence range of g _T.

Furthermore, the leakage current measuring apparatus according to the present invention displays the total value Igr of the leakage currents g _R , g _S , and g _T calculated by the calculation unit 15 and its reliability range, and further displays the value of the zero-phase current I _0. A portion 16 is provided.

That is, the instrument 17 constituting the leakage current measurement apparatus according to the present invention, a signal processing section 14, the the signal processing section 14, the ground voltage E _R inputted to star distribution source 1 is input . Further, the zero-phase current I ₀ detected by the zero-phase current transformer 9 is input to the signal processing unit 14. The signal processing unit 14 performs signal processing to measure the phase difference between the ground voltage E _R and the zero-phase current I _0. Also, the instrument 17 includes an arithmetic unit 15, the arithmetic unit 15, the effective value of the zero-phase current I ₀ obtained by the signal processing from the signal processing unit 14, the ground voltage E _R and the zero-phase current I ₀ The total value Igr of the leakage currents g _R , g _S , and g _T flowing through the phases R, S, and T via the ground insulation resistance 7 described above and the reliability range thereof are calculated. The display unit 16 displays the total value Igr calculated by the calculation unit 15 and its confidence range.

  Next, an embodiment in which the leakage current measuring apparatus according to the present invention is applied to a transformer room equipped with a star-shaped distribution power supply 1 will be described with reference to FIG.

Embodiment shown in FIG. 3, the leakage current measurement device is a fixed type, as in the embodiments described above, the ground voltage E _R as measuring voltage to the measuring instrument 17 via the contactless electrode 3 Instead of inputting, the R phase and the ground wire 8 are directly connected to the signal processing unit 14 of the measuring instrument 17 and input. The zero-phase current transformer 9 detects a zero-phase current I ₀ flowing through the ground line 8.

Further, the leakage current measuring apparatus according to the present invention is installed in a distribution room provided in the middle of the distribution line 4 in which the distribution system is a three-phase four-wire system as shown in FIG. When used, the ground wire 8 is clamped using the zero-phase current transformer 9 that collectively clamps the three wires used in the example shown in FIG. 1 described above, and the zero-phase current I ₀ flowing through the ground wire 8 is To detect. The zero-phase current I ₀ detected by the zero-phase current transformer 9 is input to the signal processing unit 14 of the measuring instrument 17. In this case, for example, ground voltage E _R as the measuring voltage is input directly connected R-phase to the signal processing section 14 of the instrument 17. Also in this example, the signal processing unit 14 performs signal processing on the ground voltage E _R inputted from the directly connected R phase and the zero phase current I ₀ detected by the zero phase current transformer 9, and the ground voltage E The phase difference between _R and the zero-phase current I ₀ is measured, signal-processed, and output to the calculation unit 15. The calculation unit 15, signal processing is the effective value of the zero-phase current I ₀ obtained by the signal processing section 14, based on the phase difference between the ground voltage E _R and the zero-phase current I _0, each phase of the ground leakage The calculation of the total value Igr of the leakage currents g _R , g _S , and g _T flowing through the resistors r _R , r _S , and r _T and its reliability range is the same as in the above-described embodiment.

In the embodiment shown in FIG. 3, a circuit breaker 19 is provided in the middle of the distribution lines 4 _R , 4 _S , 4 _T , and the leakage current g _R , g greater than a predetermined value in the calculation unit 15 of the measuring instrument 17. _When the total value Igr of _S and g _T is measured, a shut-off signal for shutting off the circuit breaker 19 is output from the arithmetic unit 15, and the distribution line 4 can be shut off quickly by shutting off the circuit breaker 19. Accidents due to excessive leakage current can be prevented in advance. Furthermore, when an alarm device 18 that emits an alarm such as sound or light is connected to the calculation unit 15 and the total value Igr of the leakage currents g _R , g _S , and g _T larger than a predetermined value is measured in the calculation unit 15 Then, a signal for operating the alarm device 18 is output from the arithmetic unit 15, and the alarm device 18 is operated to promptly notify that there is an abnormality, thereby preventing an accident due to an excessive leakage current.

By the way, the total value Igr of the leakage currents g _R , g _S , and g _T flowing through the ground leakage resistances r _R , r _S , and r _T of each phase measured in the leakage current measuring device according to the present invention, and the measurement the relationship between the ground voltage E _R of the use voltage is input to the signal processing section 14 of the instrument 17 is represented by the vector diagram of FIG. Since the ground voltage input to the measuring instrument 17 corresponds to the ground voltage of any one of the three phases, the phase angle θ with respect to the input voltage of the leakage current I ₀ may vary between 0 degrees and 360 degrees. .

Figure from the vector diagram shown in 4, the aforementioned equations (13), (14) and the zero-phase current I ₀ shown in, enable a component of the input ground voltage E _R in phase with the direction of the zero-phase current I ₀ understand the relationship between the reactive component B as the component a and phase component in the direction of advanced 90 degrees from the ground voltage E _R, value of chromatic component a and reactive component B of the zero-phase current I ₀ is a positive value, 0, Negative value.

  Next, details of the signal processing unit 14 of the measuring instrument 17 constituting the leakage current measuring apparatus according to the present invention will be described with reference to FIG.

FIG. 5 is a block circuit diagram showing a specific configuration of the signal processing unit 14. As shown in FIG. 5, the signal processing unit 14 includes an I ₀ detector 20 that detects a zero-phase current I ₀ , a first amplifier 21, a first filter 22, and a first effective value converter 23. A phase difference measuring device 24, a voltage detector 31, a second amplifier 32, a second filter 33, and a second effective value converter 34.

The I ₀ detector 20 takes in a zero phase current I ₀ which is the sum of the leakage currents of the distribution line 4 and the load facility 5 through the zero phase current transformer 9. The first amplifier 21 amplifies the zero-phase current I ₀ detected by the I ₀ detector 20 to an appropriate amount. The first filter 22 attenuates the frequency exceeding the frequency of the power supply voltage of the zero-phase current I ₀ amplified by the first amplifier 21. The first effective value converter 23 rectifies the alternating current waveform of the zero-phase current I ₀ filtered by the first filter 22 to convert it into an analog value proportional to the effective value, and outputs it to the arithmetic unit 15. To do.

The phase difference measuring device 24 calculates a phase angle θ between the zero-phase current I ₀ and one of the three relative ground voltages of the star-shaped distribution power supply 1, which is an R-phase voltage E input here. measure.

The zero-phase current I ₀ is attenuated at a frequency exceeding the power source frequency by passing through the first filter 22 and the input voltage E is passed through the second filter 33, and the zero-phase current I ₀ is zero. The waveforms of the phase current I ₀ and the input voltage E are sinusoidal waveforms of the power supply frequency as shown in FIGS.

The waveforms of the zero-phase current I ₀ and the input voltage E are such that when the phase difference θ between them is 180 degrees or less, the zero-phase current I ₀ is delayed from the input voltage E as shown in FIG. Yes. However, since the voltage input to the signal processing unit 14 is input in any phase among the three phases, the input relative ground voltage and the zero-phase current I ₀ are unknown, so that the phase difference θ is 0 ° to 360 °. Change. When the waveform of the zero-phase current I ₀ and the input voltage E passes through the zero point of the so-called zero crossing, the fixed pulse waveforms I _W and E _W have a phase difference θ between 0 and 180 degrees. 6, when the phase difference θ between the two is in the range of 180 to 360 degrees, the output is as shown in FIG. 7.

In the case shown in FIG. 6 where the phase difference θ of the input voltage E is in the range of 0 to 180 degrees, the zero-phase current I ₀ is positive or negative or negative or positive immediately after the input voltage E is zero-crossed. The rising or falling edge of the half-wave pulse I _W is determined depending on whether or not the relationship is, the time period t ₁ indicating the area S ₁ or the pulse width of the phase difference pulse (E _{W to} I _W ), the half-wave pulse I _W of the area _{S 2} or timed _{t 2} input to the arithmetic unit 14 performs arithmetic processing shown in the following equation (35) or formula (36).

Phase difference θ = 180 S ₁ / S ₂ (35)
Phase difference θ = 180 t ₁ / t ₂ (36)
Further, in the case shown in FIG. 7 where the phase difference θ of the input voltage E is in the range of 180 to 360 degrees, the zero-phase current I ₀ is positive or negative when the input voltage E is zero-crossed. Therefore, the rising or falling edge of the half-wave pulse I _W is determined, the time period t ₃ indicating the area S ₃ or the pulse width of the phase difference pulse (I _{W to} E _W ), the half-wave pulse I _W The time period t ₂ indicating the area S ₂ or the pulse width is input to the calculation unit 14, and the calculation process shown in the following Expression (37) or Expression (38) is performed.

Phase difference θ = 360−180S ₃ / S ₂ (37)
Phase difference θ = 360−180t ₃ / t ₂ (38)
And the voltage detector 31 takes in the ground voltage which is a phase voltage of the star-shaped distribution power supply 1. FIG. The second amplifier 32 amplifies or attenuates the input voltage, which is the ground voltage detected by the voltage detector 31, to an appropriate amount. The second filter 33 attenuates the frequency exceeding the power supply voltage frequency of the input voltage amplified or attenuated by the second amplifier 32. The second effective value converter 34 performs both-wave rectification on the input voltage filtered by the second filter 33 to convert the input voltage into an analog value proportional to the effective value, and outputs the analog value to the calculation unit 15.

The arithmetic unit 15, the area _{S 1} of the area _{S 1} of the output from the phase difference measurement unit 24 phase difference pulse _{(E W} ~I W), the area _{S 2} of the half-wave pulses _{I W,} the phase difference pulse _(I W ~ E _w ) area S ₃ or time interval t ₁ indicating the pulse width of the phase difference pulse (E _{W to} I _W ), time interval t ₂ indicating the pulse width of the half-wave pulse I _W , and phase difference pulse (I _{W to} E _W). ) Of the time interval t ₃ indicating the pulse width of the phase difference θ calculated from the above-described equations (35) to (38) for calculating the phase difference θ, and the first and second effective value converters 23 and 34. From the output zero-phase current I ₀ , the sequentially output input voltage value or the preset voltage value, the phase difference θ between these voltage currents, etc., the ground leakage resistance r of each phase according to the above-described equations Total value of leakage currents g _R , g _S , and g _T flowing through _{R 1} , r _S , and r _T Igr is calculated and its value is calculated.

  Thus, according to the leakage current measuring apparatus configured as shown in FIG. 1 or FIG. 3 with the star-shaped power distribution system, the healthy phase and one phase flowing through the insulation resistance of the distribution line and its load equipment in the energized state. It is possible to measure the total value Igr of the leakage currents flowing through the respective phases, and to grasp the degree of the unbalanced state of the distribution system, and to display this as the maximum and minimum range of the total value Igr of the leakage current.

Therefore, the leakage current measuring apparatus according to the present invention is a three-phase three-wire system or a three-phase four-wire power distribution system, and a ground capacitance existing between a voltage application portion and a ground portion of an electric circuit or electrical equipment. Windings of electrical equipment in which the value of is different in each of the three phases, or one of the three phases is different, or the leakage current Igr is connected between two phases or so-called lines between two phases In addition, the present invention can be applied to the case where it occurs inside an electric circuit, and the leakage current flowing through the relative ground leakage resistances r _R , r _S , r _T can be accurately measured.

As described above, the leakage current measuring apparatus according to the present invention described with reference to FIGS. 1 and 3 executes the leakage current measuring method according to the present invention. That is, the measuring instrument 17 inputs a one-phase ground voltage of the star-type power distribution system power supply 1 and executes an input voltage measurement process. The zero-phase current transformer 9 executes a zero-phase current measuring step for measuring a zero-phase current I ₀ that is a ground leakage current flowing out from the power source 1. Then, the signal processing unit 14 of the measuring instrument 17 compares the phase of the zero-phase current I ₀ measured by the zero-phase current transformer 9 with the phase difference pulse (E _{W in the} input voltage measurement step). ˜I _W ) area S ₁ , phase difference pulse (I _W ˜E _W ) area S _3, and zero-phase current I ₀ half-cycle pulse area S ₂ are calculated.

The arithmetic unit 15, the area _{S 3} of the areas _{S 1} and the phase difference pulse signal processing unit 14 is calculated by executing the signal processing step phase difference pulse _{(E W ~I W) (I} W ~E W) When calculating the phase angle θ from the zero-phase current half-cycle pulses of the area S ₂ Metropolitan of I _0, and a ground voltage of the phase angle θ and is one phase input and zero-phase current I _0, occurs each phase The calculation step of calculating the total value Igr of the leakage current Igr ₀ flowing through the ground leakage resistances r _R , r _S , r _T and the range thereof is executed.

  Further, in the calculation step, the value obtained here is displayed as the total value Igr of the leakage current flowing through the ground insulation resistance of the electrical equipment as the distribution line 4 or the load facility 5. Furthermore, in the calculation step, when it is measured that the total value Igr of the leakage current is larger than a predetermined value, the alarm device 18 connected to the calculation unit 15 indicates that there is an abnormality such as sound or light. To announce. Moreover, in the apparatus provided with the circuit breaker 19, the distribution line 4 is interrupted | blocked. An accident caused by an excessive leakage current is prevented in advance by notifying such abnormality or cutting off the distribution line.

  In distribution systems and electrical equipment, insulation measurement is required from the viewpoint of preventing electrical disasters. Conventionally, such insulation measurement has been performed with the power supply from the power outage, but in recent years the power outage is limited, especially in large factories where power is distributed by 400V class star distribution system. Many of them are used in the production process, and their stop will lead to production stop. The present invention makes it possible to accurately measure the leakage current without causing a power failure in a load line such as a distribution line or an electric device connected to the distribution line, which could not be performed by a conventional apparatus, and continuously. It is also possible to implement preventive maintenance through monitoring.

  This 400V-class star distribution system is an international standard system, and the number of practical applications in the automobile-related industry and large-sized buildings such as large buildings is increasing year by year. The requirement for ensuring reliability is also improved, and it can be widely used in these fields.

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 the load installation connected to this distribution line. Voltage to ground of the star power supply system _{E R, E S,} is a vector diagram showing the relationship between _{E T.} It is a schematic system diagram showing a configuration when the leakage current measuring apparatus according to the present invention is installed and fixed in a substation room or the like. Zero-phase current I _0, the input voltage E _R, the phase angle theta, the active ingredient A of the zero-phase current I _0, is a vector diagram showing the relationship between the reactive component B of the zero-phase current I _0. 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 figure showing the phase relationship between the waveform of the input voltage E and the zero-phase current I ₀ shows a case where the phase difference θ is in the range of 0 to 180 degrees. The figure showing the phase relationship between the waveform of the input voltage E and the zero-phase current I ₀ shows a case where the phase difference θ is in the range of 180 to 360 degrees.

Explanation of symbols

  1 Star Distribution Power Supply, 3 Electrodes, 4 Distribution Lines, 5 Load Equipment, 6 Ground Capacitance, 7 Ground Leakage Resistance, 8 Ground Line 9 Zero Phase Current Transformer, 14 Signal Processing Unit, 15 Calculation Unit, 16 Display Unit , 17 Measuring instrument, 18 Alarm 19 Circuit breaker

Claims (10)

One-phase or two-phase of the three-phase four-wire system or the three-phase three-wire power distribution system that is fed from the power source that connects the transformer's low-voltage three-phase windings in a star shape, or the three-phase ground Voltage measuring means for measuring the voltage;
Zero-phase current measuring means for measuring a zero-phase current that is a ground leakage current flowing through the feeder line and / or load facility fed from the star-shaped power source, or any one of them,
Signal processing means for calculating a phase difference between the one-phase or two-phase or three-phase ground voltage measured by the voltage measuring means and the zero-phase current measured by the zero-phase current measuring means;
From the values of the phase difference calculated by the signal processing means, the voltage measured by the voltage measuring means, and the zero phase current measured by the zero phase current measuring means, the feed line and / or the load equipment Means for calculating a total value of leakage currents of the respective phases flowing through one ground insulation resistance;
When the ground capacitance of each phase of the feed line and / or the load facility is not the same, the ground static of each phase is added to the total leakage current of each phase flowing through the ground insulation resistance. A leakage current measuring device comprising: means for calculating a degree of influence of a leakage current value generated when the electric capacities are not the same on the total value. The positive or negative measured value of the component in the same phase direction as the input voltage of one phase of the three relative ground voltages of the zero phase current which is the ground leakage current is A, and the measured value A of the three relative ground voltages is A When the positive or negative measured value of the component in the direction perpendicular to the measured input voltage of the same phase is B, the measured values are substituted into the following formulas (1) to (3), and the values U, Find V, W,
U = A + B / √3 (1)
V = -2B / √3 (2)
W = A−B / √3 (3)
When the value U of the above formula (1) and the value V of the above formula (2) are both positive or one of them is positive and the other is 0, the total value of the leakage current of each phase is calculated as the value of the above formula (2). V and the total value of the value W of the above formula (3),
When the value U of the above equation (1) and the value V of the above equation (2) are both negative or one of them is negative and the other is 0, the total value of the leakage currents of the respective phases is calculated as the value of the above equation (1). The sum of a value U ′ obtained by reversing the sign of U and a value W ′ obtained by reversing the sign of the value W in the above formula (3),
When the value U of the above equation (1) is positive and the value V of the above equation (2) is negative, the total leakage current of each phase is expressed by the value U of the above equation (1) and the above equation (2). The total value with the value V ′ obtained by reversing the sign of the value V,
When the value U of the above equation (1) is negative, the value V of the above equation (2) is positive, and the value W of the above equation (3) is positive, the total value of the leakage current of each phase is expressed by the above equation (2 ) Value V and the value W of equation (3) above,
When the value U of the above equation (1) is negative, the value V of the above equation (2) is positive, and the value W of the above equation (3) is negative, the total leakage current value of each phase is expressed by the above equation (1). ) And the value U ′ obtained by reversing the sign of the value U and the value W ′ obtained by reversing the sign W of the value W in the above formula (3),
2. The leakage current measuring apparatus according to claim 1, wherein each of the total values is a total value of leakage currents flowing through the ground insulation resistance of each phase. The phase angle measured between the zero-phase current, which is the ground leakage current measured by the zero-phase current measuring means, and the input voltage of one phase of the three relative ground voltages is 0 degree or more and less than 120 degrees In this case, the value of the measured phase angle is used as it is as the value of the phase angle θ, and when the measured phase angle is 120 degrees or more and less than 240 degrees, 120 degrees is subtracted from the measured phase angle value. When the measured phase angle is not less than 240 degrees and less than 360 degrees, the value obtained by subtracting 240 degrees from the measured phase angle value is the value of the phase angle θ. When the value of the zero-phase current, which is the current, is I ₀ , the value D is obtained by substituting into the following equation (4),
D = 2I ₀ × cos (θ−60 degrees) (4)
2. The leakage current measuring apparatus according to claim 1, wherein the value D obtained by the equation (4) is a total value of leakage currents flowing through the ground insulation resistance of each phase. When the measured phase angle between the zero-phase current that is the ground leakage current and the input voltage of one phase of the three relative ground voltages is θ ₀ , the reactive components BR, BS, BT of each phase Is represented by the following equations (5), (6), (7), and all the values of the invalid components BR, BS, BT calculated by the following equations (5), (6), (7) are: When it is close to 0, the value of the ground capacitance of each phase is substantially equal, the value of the leakage current flowing through the ground insulation resistance is determined to be close to 0, and the absolute values of the values of the ineffective components BR, BS, BT are 2. The leakage current measuring apparatus according to claim 1, wherein the maximum value is an approximate value of the value of the leakage current flowing through the ground insulation resistance.
BR = I ₀ lasin θ ₀ (5)
BS = I ₀ lasin (θ ₀ +120 degrees) (6)
BT = I ₀ rasin (θ ₀ +240 degrees) (7) The positive or negative measured value of the component in the same phase direction as the input voltage of one phase of the three relative ground voltages of the zero phase current which is the ground leakage current is A, and the measured value A of the three relative ground voltages is A When the positive or negative measured value of the component in the direction perpendicular to the measured input voltage of the same phase is B, the measured values are substituted into the following formulas (8) to (10), and the values U, Find V, W,
U = A + B / √3 (8)
V = -2B / √3 (9)
W = A−B / √3 (10)
When the value U of the above equation (8) and the value V of the above equation (9) are both positive or one of them is positive and the other is 0, the total value of the leakage current of each phase is calculated as the value of the above equation (9). V and the total value of the value W of the above formula (10),
When the value U of the above equation (8) and the value V of the above equation (9) are both negative or one of them is negative and the other is 0, the total value of the leakage currents of the respective phases is calculated as the value of the above equation (8). The sum of a value U ′ obtained by reversing the sign of U and a value W ′ obtained by reversing the sign of the value W in the above formula (10),
When the value U of the above equation (8) is positive and the value V of the above equation (9) is negative, the total leakage current of each phase is expressed by the value U of the above equation (8) and the above equation (9). The total value with the value V ′ obtained by reversing the sign of the value V,
When the value U of the above equation (8) is negative, the value V of the above equation (9) is positive, and the value W of the above equation (10) is positive, the total value of the leakage current of each phase is expressed by the above equation (9 ) Value V and the value W of equation (10) above,
When the value U of the above equation (8) is negative, the value V of the above equation (9) is positive, and the value W of the above equation (10) is negative, the total value of the leakage current of each phase is expressed by the above equation (8). ) And the value U ′ obtained by reversing the sign of the value U and the value W ′ obtained by reversing the sign W of the value W in the above formula (10),
When the total value of the leakage current flowing through the ground insulation resistance of each phase is Igr and the measured value of the zero-phase current that is the ground leakage current is I ₀ , To obtain a value M M = Igr / I ₀ (11)
When the value M in the equation (11) is close to 1, the value is close to the total value Igr of the leakage current, or the value close to the total value Igr of the leakage current is added with an upper limit value or a lower limit value.
When the value M in the above formula (11) is close to 2, the value is close to the total value Igr of the leakage current, or the value close to the total value Igr of the leakage current is added with an upper limit value or a lower limit value.
When the value M of the formula (11) is close to √3, the total value Igr of the leakage current is a value close to 0, or a value close to 0 with an upper limit value or a lower limit value,
When the value M in the above equation (11) is between a value close to 2 and a value close to √3, and between a value close to √3 and a value close to 1, it is close to the total value Igr of the leakage current. The value or the total value Igr of the leakage current is a value obtained by attaching an upper limit value or a lower limit value according to the value M of the above formula (11) or the measured value I ₀ of the zero-phase current,
2. The leakage current measuring apparatus according to claim 1, wherein each value is a total value Igr of leakage currents flowing through the ground insulation resistance of each phase.   6. The alarm unit according to claim 1, further comprising an alarm unit that issues an alarm when a total value Igr of leakage currents flowing through the ground insulation resistance of each phase calculated by the arithmetic unit exceeds a predetermined value. The leakage current measuring device according to claim 1.   The circuit according to any one of claims 1 to 6, further comprising a blocking means for cutting off the electric circuit when the total value Igr of the leakage current flowing through the ground insulation resistance of each phase calculated by the calculation means exceeds a predetermined value. The leakage current measuring device according to any one of the above.   2. The leakage current measuring apparatus according to claim 1, wherein the signal processing means calculates the phase difference and converts the ground voltage value and the zero-phase current value of the star-shaped power source into effective values.   2. The voltage measuring means comprises voltage measuring means for inputting the voltage to a measuring device through an electrode brought into contact with the surface of an insulator to which a voltage to be measured is applied. Leakage current measuring device. One-phase or two-phase of the three-phase four-wire system or the three-phase three-wire power distribution system that is fed from the power source that connects the transformer's low-voltage three-phase windings in a star shape, or the three-phase ground A voltage measurement process for measuring voltage;
A zero-phase current measurement step of measuring a zero-phase current that is a ground leakage current flowing through the power supply line and / or load facility fed from the star-shaped power source, or any one of them;
A signal processing step for calculating a phase difference between the one-phase or two-phase or three-phase ground voltage measured by the voltage measurement step and the zero-phase current measured by the zero-phase current measurement unit;
From the values of the phase difference calculated by the signal processing step, the voltage measured by the voltage measuring means, and the zero phase current measured by the zero phase current measuring means, the feeder line and / or the load equipment are either A step of calculating a total value of leakage currents of respective phases flowing through one ground insulation resistance;
When the ground capacitance of each phase of the feed line and / or the load facility is not the same, the ground static of each phase is added to the total leakage current of each phase flowing through the ground insulation resistance. A leakage current measuring method comprising: a calculation step of calculating a degree of influence of a leakage current value generated when the electric capacities are not the same on the total value.