JP2008175696A - Insulation level monitoring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulation level monitoring device capable of accurately performing ground insulation resistance determination at the level based on an electrical facility technical reference requirement in an electrical facility operation state. <P>SOLUTION: A simulation circuit 72 having a known value between a measuring object circuit 1 and the ground is selectively connected, and insulation resistance is determined by calculation using variation in ground leakage current before and after simulation circuit connection and admittance of the simulation circuit connected to the current flowing on the ground through the simulation circuit. Thus, precise insulation resistance measurement that is not affected by phase error between voltage and current of a current transformer. By correcting the current detection deviation of a zero phase current transformer, goodness/badness is determined accurately performed based on the ground insulation resistance value (1mA in resistance part leakage current conversion, for example 0.2 MΩ in 200V circuit) defined to the electrical facility technical reference. Therefore, a sign of insulation degradation of each electrical facility can be obtained early and correctly. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an insulation monitoring device, and more particularly, to a technique for determining the quality of a ground insulation resistance value in an electric circuit operating state.

  In order to judge the quality of the ground insulation state when the electric circuit is operating, the capacitance component contained in the leakage current is removed, and only the resistance leakage current that flows through the insulation resistance is obtained. It is effective to seek

As an example of the method, ground leakage current is detected in a state where a low frequency low voltage signal having a frequency of about 20 Hz and a voltage of about 0.5 V is superimposed on the circuit to be measured, and this applied frequency component is extracted from the detected leakage current. In addition, a method has been proposed in which the resistance leakage current is obtained based on the phase of the applied voltage and the ground insulation resistance is calculated from the signal voltage value and the resistance leakage current value based on the signal voltage. (For example, see Patent Document 1)
A method that does not apply a signal voltage has also been proposed, one of which is the phase relationship between the harmonic leakage current and the harmonic ground voltage in the representative orders of the harmonic components contained in the leakage current and ground voltage of the circuit under test. Thus, a resistance leakage current is obtained, and a ground insulation voltage is obtained by dividing a harmonic voltage value of a representative order by this resistance leakage current value. (For example, see Patent Document 2)
In another method in which no signal voltage is applied, simultaneous equations are used to calculate the harmonic leakage current component and the harmonic ground voltage component in the two representative orders of the harmonic component contained in the leakage current and ground voltage of the circuit under test. The ground insulation resistance component is obtained, and the quality of the insulation state is judged based on this magnitude. (For example, see Patent Document 3)
JP-A-1-143971 Japanese Patent Laid-Open No. 6-043196 JP 2003-177154 A

  In the method of applying the signal voltage, in order to prevent malfunction and damage of the load facility due to the application signal being superimposed on the main circuit, it is necessary to consider that the applied signal voltage is kept at a low voltage of about 0.5 V or less. The leakage current component due to the applied signal is extremely small.

  For this reason, there is a drawback that the measurement accuracy of the insulation resistance cannot be increased because it is easily influenced by the input / output conversion loss of the zero-phase current transformer used for detection and the phase shift between the voltage and current.

  In the method that does not apply the signal voltage, the harmonic component of the leakage current due to the ground voltage of the circuit under test is used, so a leakage current that is several hundred times larger than the signal application method can be used. In comparison, the influence of errors such as input / output conversion loss of the zero-phase current transformer in the measurement process can be reduced.

  However, in the power supply circuit to the load equipment arranged at the end of the electric circuit, the ground insulation resistance specified value (for example, the insulation resistance value in the ground voltage 200V circuit is 0.2 MΩ or more) shown in the electrical equipment technical standards and the like. (For example, it is necessary to reduce to 1 mA or less in terms of resistance leakage current), it is necessary to measure the leakage current at a level lower than 1 mA. In other cases, such as Patent Document 2 and Patent Document 3 that do not depend on signal application, the ground to the ground shown in the electrical equipment technical standards and the like is excluded. There is a drawback that it is difficult to obtain accuracy until stable determination of the insulation resistance specified value is performed.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an insulation monitoring device capable of determining a ground insulation resistance with high accuracy in an electric circuit operating state.

In order to achieve the above object, the insulation monitoring apparatus according to claim 1 is capable of disconnecting between a leakage current measuring means for measuring a leakage current from the circuit to be measured to the ground and the circuit to be measured and the ground. A simulation circuit having a known value of admittance Y _ta to be connected, a connection state in which the simulation circuit is connected between the circuit to be measured and the ground, and the simulation circuit between the circuit to be measured and the ground. Switch means for switching between the disconnected state, the simulated current measuring means for measuring the simulated current flowing to the ground through the simulated circuit, and the simulated circuit is disconnected by the switch means, and the leakage current measuring means in the disconnected state a cutting state leakage current measuring means for measuring the leakage current I _g by, the simulating circuit and a connected state by the switching means, the leakage current measuring means in said connected state While measuring more leakage current I _ga, the simulated current and connected state leakage current / simulated current measuring means for measuring the simulated current I _ta by measuring means, the leakage current obtained by the cleavage state leakage current measurement means I _g When, with the leakage current I _ga and the simulated current I _ta acquired by the connection state leakage current / simulated current measurement means, based on the admittance Y _ta of the simulation circuit, ground insulation resistance of the circuit under test R Ground insulation resistance calculation means for calculating _e using a predetermined relational expression R _e = F (I _g , I _ga , I _ta , Y _ta ), and the ground insulation resistance calculated by the ground insulation resistance calculation means and output means for outputting information about the insulation state of the circuit under test on the basis of R _e, further comprising a are characterized.

The insulation monitoring device according to claim 2 is connected to a leakage current measuring means for measuring a leakage current from the circuit to be measured to the ground, and to be disconnected between the circuit to be measured and the ground and is known. different from the first admittance Y _ta and simulation circuit which is switchably set in the second admittance Y _tb values, the first admittance Y _ta of the mimic circuit between the circuit to be measured and earth of Switch means for switching between a connection state in which one of the second admittances Y _tb is connected and a disconnection state in which the simulation circuit is disconnected from between the circuit under test and the ground; and the simulation circuit by the switch means was disconnected, the disconnection state leakage current measuring means for measuring the leakage current I _g by the leakage current measuring means in said disconnected state, the first a of the mimic circuit by said switching means The Mittansu Y _ta to a connected state, while measuring the leakage current I _ga by the leakage current measuring means in said connected state, the second admittance Y _tb of the simulation circuit and a connected state by the switching means, in said connected state a connection state leakage current measuring means for measuring the leakage current I _gb by the leakage current measuring means, and the leakage current I _g obtained by the cleavage state leakage current measuring means, acquired by the connection state leakage current measuring means the leakage current and I _ga and the leakage current I _gb, based on the first admittance Y _ta and the second admittance Y _tb of the simulating circuit, the ground insulation resistance R _e, a predetermined relational expression R _e = F was _{(I g, I ga, I} gb, Y ta, Y tb) the ground insulation resistance calculated by the ground insulation resistance calculating means for calculating with the ground insulation resistance calculating means And output means for outputting information about the insulation state of the circuit under test on the basis of R _e, further comprising a are characterized.

The insulation monitoring device according to claim 3 is connected to a leakage current measuring means for measuring a leakage current from the circuit to be measured to the ground, and the circuit to be measured and the ground so as to be disconnected, and is known differently. a first admittance Y _ta and simulation circuit which is switchably set in the second admittance Y _tb values, the first admittance of the mimic circuit between the circuit to be measured and earth Y _ta and second Switch means for switching between a connection state in which any one of the admittances Y _tb is connected and a disconnection state in which the simulation circuit is disconnected from between the circuit under test and the ground, and a simulated current flowing to the ground through the simulation circuit a simulated current measurement means for measuring a first admittance Y _ta of the mimic circuit by said switch means to the connected state, leakage conductive by the leakage current measuring means in said connected state With measuring the I _ga, simulated current I _ta measured by the simulated current measurement means, the second admittance Y _tb of the mimic circuit by said switch means to a connected state by the leakage current measuring means in said connected state The leakage current I _gb is measured and the simulated current I _tb is measured by the simulated current measuring means. The connected leakage current / simulated current measuring means, and the leakage current I acquired by the connected leakage current / simulated current measuring means. _ga, simulated current I _ta, the leakage current I _gb, and a simulated current I _tb, based on the first admittance Y _ta and the second admittance Y _tb of the simulating circuit, the ground insulation resistance R _e, predetermined relationship _{R e = F (I ga,} I gb, I ta, I tb, Y ta, Y tb) and ground insulation resistance calculating means for calculating using said calculated by the ground insulation resistance calculating means It is characterized and output means for outputting information about the insulation state of the circuit under test on the basis of the ground insulation resistance R _e, further comprising a.

  According to a fourth aspect of the present invention, there is provided the insulation monitoring apparatus according to the first, second, or third aspect, wherein the harmonic component included in the leakage current from the circuit to be measured to the ground and the current flowing to the ground through the simulation circuit. It is characterized by using the representative representative harmonic component.

According to a fifth aspect of the present invention, there is provided the insulation monitoring apparatus according to the first aspect, wherein the admittance Y _{ta of the} simulation circuit is configured by _a capacitance C _a , and the ground insulation resistance calculating means is configured to calculate the predetermined relational expression. R _e = F (I _g , I _ga , I _ta , Y _ta )
R _e = (1 / ωC _a ) × (1 / (((I _g / I _ta ) + (I _ga ² −I _g ² −I _ta ² ) / (2I _ta ² )) × ((I _g / I _ta )-(I _ga ² -I _g ² -I _ta ² ) / (2I _ta ² )))) ^0.5
The ground insulation resistance _Re is calculated as
Alternatively, the admittance Y _{ta of the} simulation circuit is configured by _a resistance Ra, and the ground insulation resistance calculation means calculates the predetermined relational expression R _e = F (I _g , I _ga , I _ta , Y _ta )
R _e = 2I _ta ² R _a / (I _ga ² −I _g ² −I _ta ² )
The ground insulation resistance _Re is calculated as follows.

According to a sixth aspect of the present invention, there is provided the insulation monitoring apparatus according to the second aspect, wherein the first admittance Y _ta of the simulation circuit is configured by _a first capacitance Ca, and the second admittance Y _tb is configured by a second capacitance C _b , and the ground insulation resistance calculation means calculates the predetermined relational expression R _e = F (I _g , I _ga , I _gb , Y _ta , Y _tb ),
R _e = (1 / ω) × ((I _ga ² −I _gb ² ) / ((I _gb ² −I _ga ² ) C _e ² + 2C _e C _a I _gb ² −2C _e C _b I _{g a} ² + I _gb ² C _a ² ― I _ga ² C _b ² )) ^0.5
Here, C _e = ((I _gb ² −I _g ² ) C _a ² − (I _ga ² −I _g ² ) C _b ² ) / (2 ((I _ga ² −I _g ² ) C _b − ( I _gb ² -I _g ² ) C _a ))
The ground insulation resistance _Re is calculated as
Alternatively, the first admittance Y _ta of the simulation circuit is configured by _a first resistor Ra, the second admittance Y _tb is configured by a second resistor R _b , and the ground insulation resistance calculating unit includes: The predetermined relational expression R _e = F (I _g , I _ga , I _gb , Y _ta , Y _tb )
R _e = 2 ((I _ga ² -I _g ² ) / R _b- (I _gb ² -I _g ² ) / R _a ) / ((I _gb ² -I _g ² ) / R _a ^2- (I _{ga ^{2 - I g 2) / R}} b 2)
The ground insulation resistance _Re is calculated as follows.

According to a seventh aspect of the present invention, there is provided the insulation monitoring apparatus according to the third aspect, wherein the first admittance Y _ta of the simulation circuit is configured by _a first capacitance Ca, and the second admittance Y _tb is constituted by the second capacitance C _b, the ground insulation resistance calculation means, the predetermined relationship _{R e = F (I ga,} I gb, I ta, I tb, Y ta, Y tb) The
R _e = (I _tb / Ω) × (1 / ( I gb 2 C b 2 - (C e + C b) 2 I tb 2)) 0.5
Here, C _e = ((I _gb ² −I _ga ² ) C _b ² −I _tb ² (C _b ² −C _a ² )) / (2 ((C _b −C _a ) I _tb ² ))
Or
The first admittance Y _ta of the simulation circuit is configured by _a first resistor Ra, and the second admittance Y _tb is configured by a second resistor R _b ,
The ground insulation resistance calculating means calculates the predetermined relational expression R _e = F (I _ga , I _gb , I _ta , I _tb , Y _ta , Y _tb ),
R _e = 2 (1 / R _b −1 / R _a ) × (I _tb ² R _b ² / (I _gb ² −I _ga ² + I _tb ² R _b ² (1 / R _a ² −1 / R _b ² )))
The insulation monitoring apparatus according to claim 3, wherein the ground insulation resistance _Re is calculated.

  According to an eighth aspect of the present invention, there is provided the insulation monitoring apparatus according to any one of the first to seventh aspects, wherein the output means uses the ground insulation resistance calculating means as information on an insulation state of the circuit under test. For at least one of the value of ground insulation resistance calculated by the above and the resistance leakage current value calculated based on the value of the ground insulation resistance, the value or the value exceeded a predetermined value Display, record, external output or report and at least one of the value of the ground insulation resistance and the resistance leakage current value, at least 2 such as a safety area, a dangerous area, etc. depending on its magnitude. It is characterized in that one or a plurality of display, recording, external output or reporting is performed by dividing into one area.

  In the present invention configured as described above, a simulation circuit is connected between the circuit to be measured and the ground, two leakage currents from the circuit to be measured to the ground before and after the connection of the simulation circuit, the admittance of the simulation circuit, and the simulation circuit The current flowing in the ground is used (invention according to claim 1), or the simulation circuit is constituted by the first and second admittances, and the circuit under test at the time of the first and second admittance connections before the simulation circuit is connected to the ground The first and second admittances (the invention according to claim 2), two leakage currents from the circuit under test to the ground when the first and second admittances are connected, The main features are the use of two currents flowing to the ground through the simulation circuit and the first and second admittances (the invention according to claim 3).

  According to the insulation monitoring device of the present invention, it is possible to measure the insulation resistance with high accuracy independent of the phase error between the voltage and current of the current transformer, and the signal voltage application device as in the prior art disclosed in Patent Document 1 Because it is unnecessary, it can be made small and inexpensive.

  Further, in the present invention, when a zero-phase current transformer is used in the measurement of leakage current, an action of correcting the current detection deviation of the zero-phase current transformer is included, so that it is defined in the technical standards for electrical equipment. The primary input current of the detection zero-phase current transformer is 1 mA, such as when judging the quality of the insulation resistance value (1 mA in terms of resistance leakage current, such as 0.2 MΩ or more in a 200 V circuit) in the operating state of the electric circuit. High-precision measurement can be performed even with a minute current level.

  Therefore, it is possible to quickly and accurately detect signs of insulation deterioration in individual electrical equipment, and by accurately detecting insulation deterioration, it is easy to perform alarms and to prevent accidents in advance. Become.

  The best mode for carrying out an insulation monitoring apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a connection between a ground leakage current detecting means of a circuit under test and a ground simulation circuit. A zero phase current transformer 4 is connected to the circuit under measurement 1. In the power supply is a transformer TR2 primary side of the circuit under test (measured circuit side) are made grounded by a ground line 3, ground leakage current flowing through the load 2 of ground admittance Y _e, the zero-phase current transformer 4 and supplied to the monitoring controller 6 of the insulation monitoring device 5. The simulation circuit connection unit 7 of the insulation monitoring device 5 has a simulation circuit 72 having a known value. The monitoring control unit 6 and the opening / closing unit SS responding to a command of the simulation circuit control unit 71 incorporated in the simulation circuit connection unit 7 Connected between the grounded line of the circuit under test 1 and the ground. The current flowing to the ground through the simulation circuit 72 is detected by the current detection unit 73 and transmitted to the simulation circuit control unit 71 and the monitoring control unit 6.

FIG. 2 shows an equivalent circuit relating to a ground leakage current passing path of the circuit under test in FIG. As shown in the figure, the ground admittance Y _e of the load 2 is represented as a parallel circuit of the insulation resistance R _e and the capacitance C _e , and a ground voltage E is applied to the ground admittance Y _e , and in parallel. The simulation circuit 72 of the simulation circuit connection unit 7, the current detection unit 73, and the open / close unit SS are connected. Further, ground admittance Y _e and simulating circuit ZCT 4 to the transmission path of the current flowing through the 72 is disposed.

Figure 3 is a switching unit SS in the example of FIG. 2 is composed of a plurality of individual switches S ₁ to S _n, a plurality of known resistance R _a to R _n or capacitance C _a -C _n the circuit under test Indicates that selective connection is possible between

4, the leakage current I _g from the measured circuit prior to closing the opening portion SS to ground, to be measured in the case where to connect the capacitance C _a by individual switch S ₂ closed during the opening and closing portion SS The relationship between the leakage current I _ga1 from the circuit to the ground and the current I _ta1 flowing to the ground through the capacitance C _a is represented by a vector diagram.

The calculation formula for _obtaining the insulation resistance R _e from the current values I _g , I _ga1 , _Ita1 and the capacitance C _a shown in FIG. 4 is derived as follows.

The relationship between the ground leakage current I _g , the ground voltage E, the insulation resistance R _e , and the ground conductance ωC _e of the circuit to be measured in the state before the capacitance C _a is connected is expressed as I _g ² = ((1 / R _e ) ² + (ωC _e ) ² ) × E ² ......... Formula (1)
It is.

Ground leakage current I _ga1 , ground voltage E, insulation resistance R _e , ground conductance ωC _e , and ground conductance C _{a of the} simulation circuit 72 when _a known capacitance C _a is connected between the circuit to be measured and the ground The relationship with
I _ga1 ² = ((1 / R _e ) ² + (ωC _e + ωC _a ) ² ) × E ² ......... Formula (2)
The relationship between the current I _ta1 flowing to the ground through the capacitance C _a , the ground voltage E, and the capacitance C _a is
E ² = I _ta1 ² / (ωC _a ) ² ……… Formula (3)
From Equation (1), Equation (2), and Equation (3),
C _e = C _a (I _ga1 ² −I _g ² −I _ta1 ² ) / (2I _ta1 ² ) Equation (4)
Is guided.

Therefore, the following formula arranged by substituting formula (4) into formula (1),
R _e = (1 / ωC _a ) × (1 / (((I _g / I _ta1 ) + (I _ga1 ² −I _g ² −I _ta1 ² ) / (2I _{ta 1} ² )) × ((I _g / I _ta1 )-(I _ga1 ² -I _g ² -I _ta1 ² ) / (2I _ta1 ² )))) ^0.5 ......... Formula (5)
There the first calculation formula for obtaining the insulation resistance R _e in the case of the admittance of the simulation circuit and the capacitance C _a.

5, the leakage current I _g to the ground from the measuring circuit prior to closing the opening portion SS, from the measurement circuit when the individual switch S ₁ closed in closing portion SS was connected a resistor R _a a leakage current I _ga2 to earth, the relation between the current I _ta2 flowing to ground through resistor R _a is a representation by vector diagram.

5, the current value I _g, formulas for determining the insulation resistance R _e by the resistance R _a of I _{ga 2,} I _ta2 and simulation circuit is derived as follows.

When the resistor _Ra is connected, the _relationship between the ground leakage current I _ga2 , the ground voltage E, the insulation resistance R _e and the ground conductance ωC _e , and the resistance R _{a of the} simulation circuit is
I _ga2 ² = ((1 / R _e + 1 / R _a ) ² + (ωC _e ) ² ) × E ² ......... Formula (6)
, And the current I _ta2 flowing to ground through resistor R _a, and ground voltage E, the relationship between the resistance R _a,
E ² ＝ I _ta2 ²・ R _a ² ......... Formula (7)
It is.

Therefore, the following expression derived from Expression (1), Expression (6), and Expression (7):
R _e = ^{_{2I ta2 2 R a / (I}} ga2 2I g 2I ta2 2) ......... formula (8)
There is a second calculation formula for obtaining the insulation resistance R _e in the case of the admittance of the simulation circuit and the resistance R _a.

FIG. 6 shows a case where the first admittance is the capacitance C _a and the second admittance is the capacitance C _b among the two or more known different admittances. The previous current I _g , the leakage current I _ga3 from the circuit to be measured when the capacitance C _a is connected by the individual switch S ₂ closed circuit, and the capacitance C _b by the individual switch S ₄ closed circuit FIG. 5 is a vector diagram _showing a relationship between a circuit under test and a leakage current I _gb3 from the circuit to be measured when connected.

Current value I _g shown in FIG. _6, I ga3, I _gb3, the capacitance C _a, the capacitance C _b, calculation formula for obtaining the insulation resistance R _e is derived as follows.

When the capacitance C _a is connected, the relationship between the ground leakage current I _ga3 , the ground voltage E, and the capacitance C _e is as follows:
I _ga3 = ((1 / R _e ) ² + (ωC _e + ωC _a ) ² ) × E ² ……… Formula (9)
The relationship between the ground leakage current I _{gb 3} , the ground voltage E, and the capacitance C _e when the capacitance C _b is connected is I _gb3 = ((1 / R _e ) ² + (ωC _e + ωC _b ) ² ) x E ² ……… Formula (10)
It becomes.

Equation (9), the capacitance to ground C _e of the measuring circuit from the equation (10),
C _e = ((I _gb3 ² −I _g ² ) C _a ² − (I _ga3 ² −I _g ² ) C _b ² ) / (2 (((I _ga3 ² −I _g ² ) C _b − (I _gb3 ² ― I _g ² ) C _a )) ……… Formula (11)
It becomes.

On the other hand, the formula (9), the insulation resistance R _e of the measuring circuit from the equation (10),
R _e = (1 / ω) × ((I _ga3 ² −I _gb3 ² ) / ((I _gb3 ² −I _ga3 ² ) C _e ² + 2C _e C _a I _gb3 ² _{−2C e} C _b I _ga3 ² + I _gb3 ² C _a ² —I _ga3 ² C _b ² )) ^0.5 ……… Formula (12)
Next, which gave C _e calculated in equation (11) into equation (12) becomes the third calculation formula for obtaining the insulation resistance R _e.

FIG. 7 shows another example in which the simulated circuit has two or more known different admittances. In the case where the first admittance is a resistor R _a and the second admittance is a resistor R _b , the current I _g before resistance connection is shown. , the leakage current I _GA4 to earth from the measurement circuit when to connect the resistors R _a, by a vector diagram the relationship between the leakage current I _GB4 to earth from the measurement circuit when the resistance R _b is connected It is a representation.

7, the current value _{I g, I ga4, I gb4} , resistors R _a, resistor R _b, by determining the insulation resistance R _e equation is derived as follows.

When the resistor R _a is connected, the relationship between the ground leakage current I _ga4 , the ground voltage E, and the resistor R _a is
I _ga4 = ((1 / R _e + 1 / R _a ) ² + (ωC _e ) ² ) × E ² ......... Formula (13)
When the resistance R _b is connected, the relationship between the ground leakage current I _gb4 , the ground voltage E, and the resistance R _b is
I _gb4 = ((1 / R _e + 1 / R _b ) ² + (ωC _e ) ² ) × E ² ……… Formula (14)
It becomes.

Therefore, the following expression derived from Expression (13) and Expression (14):
R _e = 2 ((I _ga4 ² −I _g ² ) / R _b − (I _gb4 ² −I _g ² ) / R _a ) / ((I _gb4 ² −I _g ² ) / R _a ² − (I _{ga4 ^{2 - I g 2) / R}} b 2) ……… Formula (15)
There the fourth calculation formula for obtaining the insulation resistance R _e.

8 of the examples and simulating circuits of two or more different known admittance, the first admittance capacitance C _a, in the case where the second admittance to the capacitance C _{b, the} capacitance C _a a leakage current I _GA5 to earth from the measurement circuit when to connect the, the current I _ta5 flowing to ground through the capacitance C _a, the earth from the measurement circuit when to connect the electrostatic capacitance C _b leakage current I _Gb5, a representation by the vector diagram the relationship between the current I _tb5 flowing to ground through the capacitance C _b.

Current value I _GA5 shown in FIG. _{8, I ta5, I gb5,} I gb5, the capacitance C _a, C _b, the calculation formula for obtaining the insulation resistance R _e is derived as follows.

The relationship between the ground leakage current I _ga5 and the ground voltage E when the capacitance C _a is connected is as follows:
I _ga5 ² = ((1 / R _e ) ² + (ωC _e + ωC _a ) ² ) × E ² ......... Formula (16)
The relationship between the ground leakage current I _gb5 and the ground voltage E when the capacitance C _b is connected is as follows:
I _gb5 ² = ((1 / R _e ) ² + (ωC _e + ωC _b ) ² ) × E ² ……… Formula (17)
It becomes.

The relationship between I _tb5 flowing to the ground through the capacitance C _b and the ground voltage E is
E ² = I _tb5 ² / ω ² C _b ² ... (18)
Therefore, according to Equation (16), Equation (17), and Equation (18),
^{_{C e = (I gb5 2 -}} I ga5 2) C b 2 - I tb5 2 (C b 2 - C a 2) / (2 (C b - C a) I tb5 2) ......... (19)
Is obtained.

The following formula obtained by rearranging formula (17) and formula (18):
R _e = (I _tb5 / Ω) × (1 / (I _gb5 ² C _b ² − (C _e + C _b ) ^{2 It} _b5 ² )) ^0.5
……… Formula (20)
The value obtained by giving C _e obtained by the equation (19) is one of the fifth calculation equations for obtaining the insulation resistance _Re .

On the other hand, the relationship between I _ta5 flowing to the ground through the capacitance C _a and the ground voltage E is E ² = I _ta5 ² / ω ² C _a ² (Equation (21))
So, equation (16), equation (17), wherein C _e = by ^{_{(21) ((I gb5 2}} - I ga5 2) C a 2 - I ta5 2 (C b 2 - C a 2)) / (2 (C _b -C _a ) I _ta5 ² ) Equation (22)
Is obtained.

The following formula obtained by rearranging formula (16) and formula (21):
R _e = (I _ta5 / ω) × (1 / (I _ga5 ² C _a ² − (C _e + C _a ) ² I _ta5 ² )) ^0.5 Equation (23)
The value obtained by giving C _e obtained by the equation (22) is another fifth calculation equation for obtaining the insulation resistance _Re .

FIG. 9 shows an example in which the resistor R _a is connected when the first admittance is the resistor R _a and the second admittance is the resistor R _b among the two or more known different admittances. a leakage current I _GA6 to earth from the circuit under test and the current I _ta6 flowing to ground through resistor R _a, leakage current I _GB6 of the resistor R _b from the measurement circuit when is connected to ground through a resistor R _b The relationship with the current I _tb6 flowing through the ground is represented by a vector diagram.

Current value I _GA6 shown in FIG. _{9, I ta6, I gb6,} I tb6, R a, R b, the calculation formula for obtaining the insulation resistance R _e is derived as follows.

The relationship between the ground leakage current I _ga6 and the ground voltage E when the resistor _Ra is connected by the switching unit SS is as follows:
I _ga6 = ((1 / R _e + 1 / R _a ) ² + (ωC _e ) ² ) × E ² ……… Formula (24)
The relationship between the ground leakage current I _gb6 when the resistor R _b is connected and the ground voltage E _b is as follows:
I _gb6 = ((1 / R _e + 1 / R _b ) ² + (ωC _e ) ² ) × E ² ……… Formula (25)
It becomes.

The relationship between I _tb6 flowing to the ground through the resistor R _b and the ground voltage E is E ² = I _tb6 ² R _b ² ……… Formula (26)
Therefore, the following formulas obtained by formula (24), formula (25), and formula (26):
R _e = 2 (1 / R _b -1 / R _a ) × (I _tb6 ² R _b ² / (I _gb6 ² -I _ga6 ² + I _tb6 ² R _b ² (1 / R _a ² -1 / 1 / R _b ² ))) ……… Formula (27)
But it becomes one of the sixth calculation formula for obtaining the insulation resistance R _e.

On the other hand, the I _ta6 flowing to ground through resistor R _a, the relationship between the ground voltage E,
E ² = I _ta6 ² R _a ² ……… Formula (28)
Therefore, the following expression obtained by Expression (24), Expression (25), and Expression (28):
R _e = 2 (1 / R _b -1 / R _a ) × (I _ta6 ² R _a ² / (I _gb6 ² -I _ga6 ² + I _ta6 ² R _a ² (1 / R _a ² -1 / _Rb) ² ))) ……… Formula (29)
But the other sixth calculation formula for obtaining the insulation resistance R _e.

The above-described first to sixth calculation formulas for obtaining the insulation resistance _Re are all R _e = F (I _g , I _ga , I _ta , Y _ta ). ………… Formula (30)
Or R _e = F (I _g , I _ga , I _gb , Y _ta , Y _tb ) ……… Formula (31)
Or R _e = F (I _ga , I _gb , I _ta , I _tb , Y _ta , Y _tb ) ……… Formula (32)
It shows that it does not depend on the ground voltage or the phase of ground voltage and leakage current.

  When the input current of the zero-phase current transformer is very small, the phase error between the ground voltage and the leakage current becomes large. Therefore, the equations (30) to (32) that do not depend on the phase are obtained when the input current is very small. This shows that high-precision measurement can be performed.

Further, the leakage currents I _g , I _ga , and I _gb measured by the zero-phase current transformer in the equations (30) to (32) are current elements such as (I _ga ² −I _g ² ). It is constructed in the form of a square difference between each other.

When measuring the insulation resistance of a specific circuit, the measurement is performed with the primary conductor mounted on the same zero-phase current transformer under the same conditions. Therefore, the current elements I _g , I _ga , I _Since the error of the zero-phase current transformer included in the measured value of _gb is the same and the magnitude of the error is an approximate deviation, the currents I _g , I _ga , I _gb measured by the zero-phase current transformer are the same. Even if it contains a deviation, it shows that the influence of the measured current deviation of the zero-phase current transformer is canceled in the calculation process according to the equations (30) to (32).

Further, the current elements I _ta and I _tb flowing to the ground through the simulation circuit in the equations (30) and (32) are measured by a zero-phase current transformer having the same specifications as the above-described zero-phase current transformer, By giving a correction value equivalent to the deviation obtained in advance in the above-described zero-phase current transformer in the calculation process, the detected current deviation of the zero-phase current transformer is canceled as (I _ga ² −I _tg ² ) or the like. Can have an effect.

  In the case where the circuit under test is a three-phase AC circuit, the representative orders of the harmonics 3n-th order (n is an integer) that are in phase with all three phases are extracted, and the insulation resistance is calculated according to the above first to sixth calculation formulas. By calculating the above, it is possible to calculate the insulation resistance value with higher accuracy than the conventional method.

  FIG. 10 is a circuit diagram showing an example in which the circuit connection phase can be switched when the circuit under test is a single-phase three-wire AC circuit. Components having the same or similar functions as those in the circuit diagram shown in FIG. In FIG. 10, the simulation circuit 72 is connected in advance to each of the two ungrounded phases of the circuit under test by the connection phase switching unit SF, and the phase having a large increase in leakage current from the circuit under test to the ground is selected. By calculating the insulation resistance according to the first to sixth calculation formulas, it is possible to calculate the insulation resistance value with higher accuracy than the conventional method.

FIG. 11 is a block diagram showing an embodiment of the insulation monitoring apparatus of the present invention. 4 _j1 to 4 _k2 are zero-phase current transformers for detecting leakage current, and the secondary output thereof is input to the ground leakage current input unit 62 in the monitoring control unit 6 which is one block constituting the monitoring device 5. Is done. Reference numeral 61 denotes a power supply unit that supplies an operation voltage to the inside of the monitoring control device 6, and 63 denotes an analog signal converted into an internal signal by the input unit 62 in response to an instruction from the arithmetic processing unit 64 to be described later. An A / D converter 64 for sampling the output and converting it into a digital value, 64 is a sampling and digital conversion instruction for the A / D converter 63, and the obtained digital value is stored in the storage unit 65 and insulated by the method described above. It is an arithmetic processing unit for calculating resistance and resistance leakage current. The arithmetic processing unit 64 also outputs an insulation resistance value and a resistance leakage current value, which are calculation results, to an output unit 68 described later. In response to an instruction from the arithmetic processing unit 64, the control unit 66 instructs the simulation circuit control unit 7 (to be described later) to select a circuit to be measured and to instruct connection to the simulation circuit. introduce. The output unit 68 performs remote output of the result obtained by the arithmetic processing unit 64 to the monitoring device 5 and the host device 10. The setting unit 67 gives a judgment value for alarm output and the like, and outputs the output value to the output unit 68 or the host device 10 when the calculated values of insulation resistance and resistance leakage current reach the judgment value. The output means in the insulation monitoring device 5 and the host device 10 is a visual display by a display device, a sound notification such as a buzzer, and a notification and recording of a calculation result and an abnormality occurrence time. Note that the above-described alarm judgment value can be set and the alarm holding state can be canceled from the host device 10. The storage unit 65 or the host device 10 can continuously store the calculation results periodically, and can be used for continuous recording of the insulation state, continuous monitoring of the progress of insulation deterioration, and retroactive checking.

  The simulation circuit connection unit 7, which is the other block constituting the monitoring device 5, includes a simulation circuit control unit 71, an opening / closing unit SS that responds to a command from the simulation circuit control unit 71, and a simulation circuit in which admittance is selectively connected by the opening / closing unit SS 72, a current measuring unit 73 for measuring the current flowing to the ground through the simulation circuit, and a measuring circuit switching device CC for selectively connecting the circuit under measurement. The simulated circuit control unit 71 is connected to the control unit 66 in the monitoring control unit 6, and in response to an instruction from the control unit 66, performs an opening / closing operation instruction to the above-described measurement circuit switching device CC and the opening / closing unit SS. The measurement value of the measurement unit 73 is transmitted to the arithmetic processing unit of the monitoring control unit via the simulation circuit control unit 71 and the control unit 66.

  FIG. 12 is a connection diagram showing a case where the insulation monitoring device of the present invention is applied to a load facility group. The monitoring control unit 6 is installed in the vicinity of the zero-phase current transformer, the simulation circuit connection unit 7 is installed in the vicinity of the load, and the two are connected by wired or wireless communication to select the circuit to be measured and the simulation circuit. Reply with switching and simulated circuit current.

FIG. 13 shows an example of determining the insulation resistance value defined in the electrical equipment technical standards. The ground voltage E = 200 V, the ground insulation resistance R _e = 0.2 MΩ, and the ground capacitance C _e = 0 of the circuit to be measured. It is explanatory drawing which compared magnitude | size of the ground insulation resistance quality determination error about the influence part of the detection electric current deviation of a zero phase current transformer by comparing with the prior art and this invention supposing 0.05 micro F.

  In order to compare only the influence of the detected current deviation of the zero-phase current transformer in the minute current region, the calculation comparison contents assuming that there is no error factor other than the detected deviation of the zero-phase current transformer are shown below.

The leakage current true value I _g = ((1 / 0.2 ² ) + ω ² 0.05 ² ) ^0.5 × 200 × 10 ⁻³ = 3.30 (mA), and the detection deviation value of the zero-phase current transformer Assuming that −0.5 (mA), the leakage current detection value I _g ^′ is I _g ^′ = I _g −0.5 = 2.80 (mA).

Since the influence on the resistance leakage current calculation is assumed to be only the detected current deviation of the zero-phase current transformer, the ground insulation resistance calculation value R _e (conventional technology), the calculation error, and the error ratio in the conventional technology are respectively
R _e (prior art) = 0.2 × (I _g ^′ / I _g ) = 0.236 (MΩ)
Insulation resistance calculation error = 0.236-0.2 = 0.036 (MΩ)
Insulation resistance calculation error rate = 0.036 / 0.2 x 100 = 18.0%
It becomes.

In the example using the equation (15) shown in the present embodiment, zero-phase current transformation when the first resistance of the simulation circuit is 0.7 (MΩ) and the second resistance is 0.35 (MΩ) The ground insulation resistance calculated value R _e , the calculation error, and the error calculated by assuming that the detected current deviation value includes −0.5 (mA) in all measured values of the detected currents I _g , I _ga , and I _gb. Each ratio is
Ground insulation resistance calculation value R _e = 0.206 (MΩ)
Insulation resistance calculation error = 0.206-0.2 = 0.006 (MΩ)
Insulation resistance calculation error rate = 0.006 / 0.2 x 100 = 3.0%
It becomes.

It is a circuit diagram which shows the path | route of the electric current which flows through the earth from a load installation and a simulation circuit, and the input to an insulation monitoring apparatus. It is an equivalent circuit diagram of the leakage current which flows through the ground from a circuit to be measured. It is an internal circuit diagram of a simulation circuit connection part. It is a vector diagram showing the relationship between the leakage current before connection of the simulation circuit of the circuit to be measured, the leakage current after connection of the capacitor of the simulation circuit, and the current flowing to the ground through the capacitor of the simulation circuit. It is a vector diagram showing the relationship between the leakage current before connection of the simulation circuit of the circuit to be measured, the leakage current after connection of the resistance of the simulation circuit, and the current flowing to the ground through the resistance of the simulation circuit. It is a vector diagram showing the relationship between the leakage current before connection of the simulation circuit of the circuit under test, the leakage current after connection of the first capacitor constituting the simulation circuit, and the leakage current after connection of the second capacitor. It is a vector diagram showing the relationship between the leakage current before connection of the simulation circuit of the circuit to be measured, the leakage current after connection of the first resistor constituting the simulation circuit, and the leakage current after connection of the second resistor. A leakage current when the first capacitor constituting the simulation circuit is connected to the circuit to be measured, a current flowing to the ground through the first capacitor, a leakage current when the second capacitor is connected, and the second capacitor It is a vector diagram which shows the relationship with the electric current which flows into the earth through. A leakage current when the first resistor constituting the simulation circuit is connected to the circuit to be measured, a current flowing to the ground through the first resistor, a leakage current when the second resistor is connected, and the second resistance It is a vector diagram which shows the relationship with the electric current which flows into the earth through. It is a circuit diagram in the case of applying the present invention to a single-phase three-wire AC circuit. It is a block diagram which shows the structure of the insulation monitoring apparatus by the Example of this invention. It is a circuit diagram which shows the example which applied the insulation monitoring apparatus of this invention to several to-be-measured circuits. It is explanatory drawing which described the zero phase current transformer measurement deviation suppression effect of this invention compared with the calculation result by a prior art.

Explanation of symbols

Ground voltage E · · · the circuit under test, I _g · · · ground leakage current of the circuit under test, I _ga · · · first ground leakage current of the circuit to be measured when connecting the admittance of the simulating circuit, I _gb : ground leakage current of the circuit under test when the second admittance of the simulation circuit is connected, I _ta: current flowing from the circuit under test to the ground through the first admittance of the simulation circuit, I _tb. Current flowing from the circuit under test to the ground through the second admittance of the simulation circuit, R _e ... insulation resistance of the circuit under measurement, R _a ... first resistance of the simulation circuit, R _b ... simulation circuit Second resistance, C _e ... capacitance of the circuit under measurement, C _a ... first capacitance of the simulation circuit, C _b ... second capacitance of the simulation circuit , SS · · · closing unit, S ₁ ~S _n ··· individual switches, SF · · · connected phase switching unit, CC Measuring circuit switching device, 1 ... circuit under test, 2 ... load, 3 ... transformer secondary side ground line, 4, 4 _j to 4 _k ... zero-phase current unit, 5 ... insulation monitoring Device: 6 ... Monitoring control unit, 7 ... Simulated circuit connection unit, 8 ... Measured circuit connection unit, 9 ... Communication means with host device, 10 ... Host device, 61 ... -Power supply unit, 62 ... Ground leakage current input unit, 63 ... A / D conversion unit, 64 ... arithmetic processing unit, 65 ... storage unit, 66 ... control unit, 67 ... Setting unit 68 ... Output unit 71 ... Simulated circuit control unit 72 ... Simulated circuit 73 ... Current measuring unit 81 ... One of the ungrounded wires of the circuit under test 82 ..Other one of the ungrounded wires of the circuit under test

Claims (8)

Leakage current measuring means for measuring the leakage current from the circuit under test to the ground,
A simulation circuit having a known value of admittance Y _ta severably connected between the circuit under test and the ground;
Switch means for switching between a connection state in which the simulation circuit is connected between the circuit to be measured and the ground, and a disconnection state in which the simulation circuit is disconnected from between the circuit to be measured and the ground;
Simulated current measuring means for measuring a simulated current flowing to the ground through the simulated circuit;
A cutting state leakage current measuring means for measuring the leakage current I _g by the simulated circuit is disconnected, the leakage current measuring means in said disconnected state by the switching means,
The simulation circuit and a connected state by the switching means, the measured leakage current I _ga by the leakage current measuring means in said connected state, the simulated current connection state leakage current / simulated to measure a simulated current I _ta by measuring means Current measuring means;
Wherein a cutting state leakage current measuring means and the leakage current I obtained by _g, and the leakage current I _ga and the simulated current I _ta, which is acquired by the connection state leakage current / simulated current measurement means, admittance of the simulation circuit based on the Y _ta, the ground insulation resistance R _e of the circuit under test, the predetermined relationship _{R e = F (I g,} I ga, I ta, Y ta) ground insulation resistance calculating means for calculating with When,
And output means for outputting information about the insulation state of the circuit under test on the basis of the ground insulation resistance R _e calculated by the ground insulation resistance calculating means,
An insulation monitoring device comprising: Leakage current measuring means for measuring the leakage current from the circuit under test to the ground,
A simulation circuit which is severably connected between the circuit to be measured and the ground and is set to be switchable between a first admittance Y _ta and a second admittance Y _tb having different known values;
The connection state in which one of the first admittance Y _ta and the second admittance Y _tb of the simulation circuit is connected between the circuit to be measured and the ground, and between the circuit to be measured and the ground from the ground. Switch means for switching between the cut state when the simulated circuit is cut,
The simulated circuit is disconnected, and a cutting state leakage current measuring means for measuring the leakage current I _g by the leakage current measuring means in said disconnected state by the switching means,
A first admittance Y _ta of the simulation circuit is set in a connected state by the switch means, and a leakage current _Iga is measured by the leakage current measurement means in the connected state, and a second admittance of the simulation circuit is measured by the switch means. Y _{tb is set} to a connected state, and in the connected state, the leakage current measuring unit at the time of measuring the leakage current I _gb by the leakage current measuring unit;
Wherein a cutting state leakage current measuring means and the current leakage is obtained by I _g, and the leakage current I _ga and the leakage-current I _gb acquired by the connection state leakage current measuring means, the first admittance of the simulation circuit Based on Y _ta and the second admittance Y _tb , the ground insulation resistance R _e is calculated using a predetermined relational expression R _e = F (I _g , I _ga , I _gb , Y _ta , Y _tb ) Insulation resistance calculation means;
And output means for outputting information about the insulation state of the circuit under test on the basis of the ground insulation resistance R _e calculated by the ground insulation resistance calculating means,
An insulation monitoring device comprising: Leakage current measuring means for measuring the leakage current from the circuit under test to the ground,
A simulation circuit which is severably connected between the circuit to be measured and the ground and is set to be switchable between a first admittance Y _ta and a second admittance Y _tb having different known values;
The connection state in which one of the first admittance Y _ta and the second admittance Y _tb of the simulation circuit is connected between the circuit to be measured and the ground, and between the circuit to be measured and the ground from the ground. Switch means for switching between the cut state when the simulated circuit is cut,
Simulated current measuring means for measuring a simulated current flowing to the ground through the simulated circuit;
The switch means puts the first admittance Y _ta of the simulation circuit into a connected state, and in the connected state, the leakage current _Iga is measured by the leakage current measuring means, and the simulated current _Ita is measured by the simulated current measuring means. Then, the second admittance Y _tb of the simulation circuit is set in the connected state by the switch means, and the leakage current _Igb is measured by the leakage current measuring means in the connected state, and the simulated current I _{tb is} measured by the simulated current measuring means. Leakage current / simulated current measuring means for measuring
The acquired by the connection state leakage current / simulated current measurement means the leakage current I _ga, simulated current I _ta, the leakage current I _gb, and the simulated current I _tb and the first admittance of the simulation circuit Y _ta and the second Based on the admittance Y _tb , the ground insulation resistance R _e is calculated using a predetermined relational expression R _e = F (I _ga , I _gb , I _ta , I _tb , Y _ta , Y _tb ) A calculation means;
And output means for outputting information about the insulation state of the circuit under test on the basis of the ground insulation resistance R _e calculated by the ground insulation resistance calculating means,
An insulation monitoring device comprising:   4. Insulation according to claim 1, 2 or 3, wherein a leakage current from the circuit to be measured to the ground and a representative order harmonic component among the harmonic components contained in the current flowing to the ground through the simulation circuit are used. Monitoring device. The admittance Y _{ta of the} simulation circuit is constituted by _a capacitance C _a ,
The ground insulation resistance calculating means calculates the predetermined relational expression R _e = F (I _g , I _ga , I _ta , Y _ta ),
R _e = (1 / ωC _a ) × (1 / (((I _g / I _ta ) + (I _ga ² −I _g ² −I _ta ² ) / (2I _ta ² )) × ((I _g / I _ta )-(I _ga ² -I _g ² -I _ta ² ) / (2I _ta ² )))) ^0.5
The ground insulation resistance _Re is calculated as
Or
The admittance Y _{ta of the} simulation circuit is constituted by _a resistor Ra,
The ground insulation resistance calculating means calculates the predetermined relational expression R _e = F (I _g , I _ga , I _ta , Y _ta ),
R _e = 2I _ta ² R _a / (I _ga ² −I _g ² −I _ta ² )
The insulation monitoring apparatus according to claim 1, wherein the ground insulation resistance _Re is calculated. The first admittance Y _ta of the simulation circuit is configured by _a first capacitance C _a , and the second admittance Y _tb is configured by a second capacitance C _b ,
The ground insulation resistance calculating means calculates the predetermined relational expression R _e = F (I _g , I _ga , I _gb , Y _ta , Y _tb ),
R _e = (1 / ω) × ((I _ga ² −I _gb ² ) / ((I _gb ² −I _ga ² ) C _e ² + 2C _e C _a I _gb ^{2 _{- 2C e C b I ga 2}} + I gb 2 C a 2 - I ga 2 C b 2)) 0.5
Here, C _e = ((I _gb ² −I _g ² ) C _a ² − (I _ga ² −I _g ² ) C _b ² ) / (2 (((I _ga ² −I _g ² ) C _b − ( I _gb ² -I _g ² ) C _a ))
The ground insulation resistance _Re is calculated as
Or
The first admittance Y _ta of the simulation circuit is configured by _a first resistor Ra, and the second admittance Y _tb is configured by a second resistor R _b ,
The ground insulation resistance calculating means calculates the predetermined relational expression R _e = F (I _g , I _ga , I _gb , Y _ta , Y _tb ),
R _e = 2 ((I _ga ² −I _g ² ) / R _b − (I _gb ² −I _g ² ) / R _a ) / ((I _gb ² −I _g ² ) / R _a ² −I _ga ² ― I _g ² ) / R _b ² )
The insulation monitoring apparatus according to claim 2, wherein the ground insulation resistance _Re is calculated. The first admittance Y _ta of the simulation circuit is configured by _a first capacitance C _a , and the second admittance Y _tb is configured by a second capacitance C _b ,
The ground insulation resistance calculating means calculates the predetermined relational expression R _e = F (I _ga , I _gb , I _ta , I _tb , Y _ta , Y _tb ),
R _e = (I _tb / Ω) × (1 / ( I gb 2 C b 2 - (C e + C b) 2 I tb 2)) 0.5
Here, C _e = ((I _gb ² −I _ga ² ) C _b ² −I _tb ² (C _b ² −C _a ² )) / (2 ((C _b −C _a ) I _tb ² ))
Or
The first admittance Y _ta of the simulation circuit is configured by _a first resistor Ra, and the second admittance Y _tb is configured by a second resistor R _b ,
The ground insulation resistance calculating means calculates the predetermined relational expression R _e = F (I _ga , I _gb , I _ta , I _tb , Y _ta , Y _tb ),
_{R e = 2 (1 / R} b - 1 / R a) × (I tb 2 R b 2 / (I gb 2 - I ga 2 + I tb 2 R b 2 (1 / R a 2 - 1 / R b ² )))
The insulation monitoring apparatus according to claim 3, wherein the ground insulation resistance _Re is calculated.   The output means includes, as information on the insulation state of the circuit under test, a value of the ground insulation resistance calculated by the ground insulation resistance calculation means, and a resistance leakage current value calculated based on the value of the ground insulation resistance Display, record, external output or report that the value or the value has exceeded a predetermined value, and the value of the ground insulation resistance and the resistance leakage current value. At least one of them is classified into at least two areas such as a safety area and a dangerous area according to its size, and one or more of display, recording, external output, or reporting is performed. The insulation monitoring apparatus according to any one of claims 1 to 7.

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