JP4738274B2 - Insulation monitoring apparatus and method for electrical equipment - Google Patents

Description

  The present invention relates to an insulation monitoring apparatus for an electrical facility and a method thereof for detecting an insulation failure by detecting a current flowing in a ground line of a private substation facility or the like.

  2. Description of the Related Art Conventionally, there are two types of insulation monitoring methods for a low voltage circuit of an electric workpiece such as a private power receiving / transforming facility: (i) “Io method” and (ii) “Igr method”. Hereinafter, the Io method and the Igr method will be briefly described.

(I) "Io method"
As shown in FIG. 12, the “Io method” is a zero phase flowing in the ground line 3 by a zero phase current transformer (ZCT) 4Z provided in the ground line 3 of the power receiving transformer 1 constituting the private power receiving / transforming equipment. In this method, the current Io is extracted and input to the insulation monitoring device 10A, and the insulation monitoring device 10A determines whether or not insulation failure has occurred based on the magnitude of the zero-phase current Io (see, for example, Non-Patent Document 1). .

  The zero-phase current Io includes a charging current that leaks to the ground via the ground capacitance C in the middle of the cable 2 that supplies electricity to the load equipment, and a resistive current that leaks to the ground as the ground insulation resistance R decreases. There is a minute. The zero-phase current transformer 4Z extracts a zero-phase current Io that is a combined current of the charging current and the resistive current. Among the zero-phase currents Io, it is the resistive current component that becomes a problem in terms of equipment security. However, as described above, in the “Io method”, since the measurement includes the charging current component, particularly in a facility with a large charging current, There is a problem that it is difficult to ensure the detection accuracy of insulation failure, and the installation range is limited.

(Ii) "Igr method"
On the other hand, the “Igr method” is to extract only the resistive current and determine whether there is an insulation failure so as not to include the charging current that is the problem of the “Io method” described above. (For example, refer to Patent Document 1, Patent Document 2, and Non-Patent Document 1).

  In this “Igr method”, as shown in FIG. 13, a monitoring signal having a frequency component different from the system frequency is injected from the injection transformer 5 coupled to the ground line 3 of the power receiving transformer 1 to the system side. The monitoring signal returned through the ground capacitance C or the ground insulation resistance R in the middle path of the cable 2 is extracted by the current transformer 4 installed on the ground line 3 and input to the insulation monitoring device 10B. Then, the presence or absence of insulation failure is determined by extracting only the resistive current from the input signal in the insulation monitoring device 10B.

  As described above, since the “Igr method” is configured to extract only the resistive current component from the zero-phase current Io, the detection accuracy of the occurrence of insulation failure is improved as compared with the “Io method”. Therefore, when installing or removing the insulation monitoring device 10B, it is necessary to power out the electrical equipment to ensure safety. In recent years, due to the widespread use of electrical devices such as personal computers, it has been necessary to avoid power outages of electrical equipment as much as possible, which has been an obstacle to the installation of the insulation monitoring device 10B.

  Further, since the monitoring signal injected from the injection transformer 5 is a minute signal, there is a problem that the measurement accuracy for the resistive current is limited.

  In recent years, in order to solve the problems between the “Io method” and the “Igr method” described above, the measured zero phase has been made by a device such as a calculation method while having a simple configuration that does not require the injection transformer 5. There has been proposed a method of extracting only a resistive current component resulting from a decrease in ground insulation resistance from a current (see, for example, Patent Document 3, Patent Document 4, and Patent Document 5). Here, for convenience, this method is referred to as “Ior method”.

  FIG. 14 is a diagram showing the configuration of the “Ior method”. This “Ior method” is the same as the “Io method” described above except that the insulation monitoring device 10C takes in the voltage from the electrical equipment as a reference amount for extracting the resistive current component from the zero-phase current Io. Same as the configuration. The insulation monitoring device 10C is generally adapted to always take in the voltage from the electrical equipment. However, the insulation monitoring device 10C has a built-in voltage storage means to temporarily take in the voltage only during installation, and the insulation monitoring device 10C. It can also be stored inside.

With this voltage storage means built-in, the monitoring device 10C can be operated with the same configuration as the “Io method” shown in FIG. That is, the “Ior method” can provide detection accuracy equivalent to that of the “Igr method” while being simpler than the “Io method” that does not require the installation of the injection transformer 5.
JP 9-318684 A Japanese Patent Application Laid-Open No. 2002-171662 Japanese Patent No. 3405407 JP 2001-242205 A JP 2006-71341 A 'Electricity and Construction', January 2002, Ohmsha, P85-92

  However, when the “Ior method” shown in FIG. 14 is applied to an electrical facility in which a three-phase Δ-connection or V-connection transformer is installed, in order to accurately extract the resistive current, the charging current of each phase The condition that is balanced is necessary.

  This point will be described with reference to FIGS. FIG. 15 shows the phase relationship of each quantity of electricity in a state where the charging current of each phase is balanced in the electrical equipment in which the b-phase grounded receiving transformer 1 connected in three phases Δ connection (or V connection) is installed. FIG.

  Vab and Vcb are a-phase and c-phase voltages based on the b-phase, Ica and Icc are a-phase and c-phase charging currents, and Ira is an insulation failure in the a-phase. Represents a resistive current assuming that In a state where the charging current is balanced between the a phase and the c phase (Ica = Icc), as shown in FIG. 15, the charging current Ic as the entire electrical equipment has the same phase as the voltage Vca between the non-grounded phases.

  Therefore, when an insulation failure occurs in the a phase in this state, the current transformer 4 installed on the ground line 3 of the power receiving transformer 1 in FIG. 14 is charged with the charging current Ic and the resistive current Ira as shown in FIG. The zero-phase current Io synthesized from the above is measured and input to the insulation monitoring device 10C.

  On the other hand, FIG. 16 shows an unequilibrium state between the a-phase charging current and the c-phase charging current in the electrical equipment having the b-phase grounded receiving transformer 1 that is similarly connected in three phases Δ (or V). It is a vector diagram showing the phase relationship of each quantity of electricity when (Ica ≠ Icc).

  The phase of the voltage amount is the same as that in the balanced state shown in FIG. 15, but since the charging current is in an unbalanced state, the charging current Ic ′ as a whole electric equipment is different in phase from the voltage Vca between the non-grounded phases. It will be. When a resistive current Ira having the same magnitude as that shown in FIG. 15 flows due to the occurrence of an a-phase insulation failure, a zero-phase current Io ′ synthesized from the charging current Ic ′ and the resistive current Ira is converted into a current transformer. 4 is extracted and input to the insulation monitoring device 10C, but it can be seen that the phase is greatly different from the zero-phase current Io of FIG. 15 where the charging current is balanced.

  Here, how the resistive current is derived in each state of FIGS. 15 and 16 in the “Ior method” proposed in Patent Document 5, for example, will be described below.

In the “Ior method” proposed in Patent Document 5, a voltage amount of an electrical facility is introduced, and a reference amount Ivc having the same phase as the charging current of the entire electrical facility is generated based on this voltage amount. Using this reference amount Ivc and the zero-phase current Io extracted by the current transformer 4 installed on the ground line 3 of the transformer, the resistive current Ir is calculated by the equation (1).
Ir = Io / Ivc / sinθ (1)
However, (theta) is an angle which Io and Ivc make.

  In particular, in the case of a transformer having a three-phase Δ (V) connection, the final resistive current value is obtained by dividing the resistive current Ir by cos 30 °.

  If this calculation method of the resistive current Ir is applied to the state where the charging current shown in FIG. 15 is balanced (Ica = Icc), it may be considered that Ivc in the equation (1) is replaced with Vca in FIG. As a result, Ir in the formula (1) is obtained as Ir (double line) in FIG. 15, and by dividing by cos 30 °, Ira in FIG. 15 is obtained. That is, it can be seen that the resistive current Ira is accurately derived in a state where the charging current is balanced.

  On the other hand, when the charging current shown in FIG. 16 is applied to an unbalanced state (Ica ≠ Icc), the Ivc in the equation (1) may be replaced with Vca in FIG. As a result, Ir in the formula (1) is obtained as Ir ′ (double line) in FIG. 16, but it is clear that this result is clearly different from the case of FIG.

  The “Ior method” proposed in Patent Document 5 is a method of calculating the resistive current by utilizing the fact that the reference amount Ivc (charging current direction) and the resistive current Ir are orthogonal to each other. This difference is caused by the fact that this orthogonal relationship is broken in a state where the charging current is unbalanced.

  Regarding the “Ior method” proposed in Patent Document 3 and Patent Document 4, the method of extracting the resistive current component from the zero-phase current is different, but the charging current shown in FIG. 15 is balanced. When the charging current is in an unbalanced state, the phase relationship between the voltage amount and the zero-phase current measured by the current transformer changes. Is the same as the method proposed in Patent Document 5.

  Therefore, in view of the above-described problems, the present invention is resistant to the Ior method even when the charging current is in an unbalanced state when the Ior method is applied to an electrical facility in which a three-phase Δ-connection or V-connection transformer is installed. It is an object of the present invention to provide an insulation monitoring device for an electric facility and a method thereof capable of more accurately detecting the current component and accurately monitoring the insulation.

In order to achieve the above object, the electrical equipment insulation monitoring device according to claim 1 comprises: current measuring means for taking in a zero-phase current flowing in the ground wire of the transformer constituting the electrical equipment;
Voltage measuring means for taking in the voltage of the electrical equipment;
A reference vector generating means for generating a reference vector based on the voltage of the electrical equipment taken in by the voltage measuring means and storing the reference vector;
Charging current vector phase angle estimating means for obtaining the phase angle of the zero-phase current taken in by the current measuring means;
The difference between the phase angle of the reference vector generated by the reference vector generation means and the phase angle of the zero-phase current measured by the charging current vector phase angle estimation means is obtained, and the absolute value of this phase difference is predetermined. A reference vector phase correction unit that switches a correction method depending on whether or not the value is equal to or less, and corrects a phase angle of the reference vector;
Orthogonal component computing means for obtaining an orthogonal component of the zero-phase current measured by the current measuring means with respect to the reference vector phase-corrected by the reference vector phase correcting means;
Insulation monitoring determination means for detecting the presence or absence of insulation failure of the electrical equipment based on the size of the orthogonal component calculated by the orthogonal component calculation means;
Output means for outputting that when the insulation monitoring judgment means judges that there is insulation failure;
It is provided with.

According to an eighth aspect of the present invention, there is provided an electrical equipment insulation monitoring method comprising: taking a zero-phase current flowing in a ground wire of a transformer constituting the electrical equipment; obtaining a phase angle of the zero-phase current; Is generated by the voltage measuring means, a reference vector is generated and stored based on the voltage, and the difference between the phase angle of the reference vector and the phase angle of the zero-phase current is calculated from the phase angle of the reference vector and the phase angle of the zero-phase current. If the absolute value of this phase difference is less than or equal to a predetermined value, the phase angle of the reference vector is corrected so as to be in phase with the zero-phase current, and the quadrature component with respect to the phase corrected reference vector is obtained. The presence or absence of insulation failure in the electrical equipment is detected by the insulation monitoring judgment means based on the magnitude of the orthogonal component, and when it is judged that there is insulation failure, a message to that effect is output.

  According to the present invention, in an electrical facility in which a three-phase Δ (V) -connected power receiving transformer is installed, even if the charging current flowing through the grounding line is in an unbalanced state, the ground insulation resistance decreases. It is possible to provide an insulation monitoring device for electric equipment and a method thereof capable of more accurately detecting a resistive current component flowing through.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an electrical equipment insulation monitoring apparatus and method according to the present invention will be described below with reference to the drawings. In addition, the same code | symbol or a related code | symbol is attached | subjected to the part which is common throughout each figure, and the overlapping description is abbreviate | omitted suitably.

(First embodiment)
FIG. 1 is a block diagram showing the configuration of the first embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes a power receiving transformer for an electrical facility to be monitored, where the secondary side is Δ-connected so that the received high voltage is transformed into a low voltage and supplied to the load facility via the cable 2. It has become. An arbitrary phase on the secondary side of the power receiving transformer 1, for example, phase b is grounded via a ground wire 3, and a current transformer 4 is coupled to the ground wire 3, and a flowing zero-phase current Is extracted by the current transformer 4. The power receiving transformer 1 may be a three-phase V-connection instead of the three-phase Δ-connection. However, in the following description, the three-phase Δ-connection will be described as an example.

Reference numeral 10 _-1 denotes an insulation monitoring device according to the present embodiment, which is configured to take in the zero-phase current extracted by the current transformer 4 by the current measuring means 11.

  The current measuring means 11 includes, as an example, a filter, a sample holder, an A / D converter, and the like. After the zero-phase current taken in by the current transformer 4 is converted into a size that can be easily processed, The harmonics are removed by a filter, and then the zero-phase current of the fundamental wave is sampled at a predetermined sampling frequency by a sample holder, and the sample value of the zero-phase current is subjected to subsequent digital arithmetic processing by an A / D converter. Generate and output digital data related to the zero-phase current necessary to perform. In the following description, digital data relating to zero phase current is referred to as “zero phase current data”. Note that if the sampling frequency in the sample holder is set to an electrical angle of 30 ° of the commercial frequency or an electrical angle obtained by multiplying it by a natural number, a phase shift calculation described later can be easily performed. The electrical angle is not limited.

  Similarly to the current measuring unit 11, the voltage measuring unit 12 includes a filter, a sample holder, an A / D converter, and the like. The voltage between the non-grounded phases of the power receiving transformer 1 (in the case of b-phase grounding, (c-a interphase voltage Vca) is taken in, and the interphase voltage Vca is filtered, sampled, and digitally converted to generate and output digital data relating to the voltage between the non-grounded phases (hereinafter referred to as “voltage data”).

The reason why the non-grounded phase voltage Vca is taken in the present embodiment is that it is convenient because the non-grounded phase voltage Vca can be used as a reference vector as described later. However, the present embodiment is not limited to this, and may also be used as an arbitrary phase voltage or a voltage used as a power supply voltage of the insulation monitoring device _10-1 . What is necessary is just to switch the reference | standard vector generation method in the reference | standard vector generation means 13 mentioned later by the phase to take in.

The voltage of incorporation constantly during operation uptake insulation monitoring device 10 _-1 of the electric equipment, always A configuration may be to update the reference vector, or in electrical equipment, transformers, connection, etc., including phase sequence As long as there is no change, it is considered that there is no fluctuation in the voltage phase in the steady state. Therefore, it is possible to adopt a configuration in which the insulation monitoring device _10-1 is taken in only at the first installation time in the electrical equipment. For this configuration, it is necessary to provide the storing the taken-voltage unit, completely equivalent simple construction installation state of the insulation monitoring system 10 _-1 as "Io method" shown in FIG. 12 Thus, wiring and the like at the time of installation are reduced, and it is possible to install by simple construction.

  The reference vector generation unit 13 provided at the subsequent stage of the voltage measurement unit 12 uses the “voltage data” generated by the voltage measurement unit 12 to convert the resistive current that flows along with the decrease in the ground insulation resistance to the zero-phase current. This is a means for generating a reference vector serving as a reference when extracting from. This reference vector is generated as a vector having the same phase angle as the charging current of the entire electrical equipment.

  As shown in FIG. 15 above, in the state where the charging current is balanced, the charging current of the entire electrical equipment is in the same phase as the non-ground phase voltage, so the voltage taken in by the voltage measuring means 12 is between the non-ground phases. In the case of voltage, the generated “voltage data” can be used as a reference vector as it is. However, when the voltage taken in by the voltage measuring means 12 is a voltage amount other than the non-ground phase voltage, the phase shift is performed so that the generated “voltage data” has the same phase angle as the charging current of the entire electrical equipment. A “reference vector” may be generated by performing an operation.

  On the other hand, the charging current vector phase angle estimation unit 14 provided in the subsequent stage of the current measurement unit 11 calculates the phase angle of the “zero phase current data” generated by the current measurement unit 11 and calculates the zero phase current data. Outputs the phase angle.

  The reference vector phase correction means 15 obtains the phase angle of the reference vector generated by the reference vector generation means 13, and further, the difference from the phase angle of the zero-phase current obtained by the charging current vector phase angle estimation means 14, that is, the position. Find the absolute value of the phase difference.

  If the phase difference obtained by the reference vector phase correction means 15 is within a predetermined value, the reference is set so as to be in phase with the “zero phase current data” output from the charging current vector phase angle estimation means 14. The phase of the “reference vector” generated by the vector generation unit 13 is corrected. If the phase difference is larger than a predetermined value, the reference vector phase correction unit 15 uses the reference vector phase correction unit 15 as a reference vector during the previous calculation. The adopted one is used again as a reference vector.

  That is, the reference vector phase correcting means 15 is configured to hold the previous value when the obtained phase difference is larger than a predetermined value. For example, if the predetermined value is ± 5 ° with reference to the voltage between the ungrounded phases, the effect of correction can be obtained even when there is an imbalance of more than 30% between the phases of the charging current.

  The quadrature component calculation means 16 uses the “zero-phase current data” output from the current measurement means 11 and the reference vector output from the reference vector phase correction means 15 to generate a resistive current that flows as the ground insulation resistance decreases. Is extracted from the zero-phase current.

  For example, if the zero-phase current extracted by the current transformer 4 is Io and the reference vector generated by the reference vector phase correction means 15 is Ivc, the quadrature component calculation means 16 uses the above-described equation (1) to calculate the zero-phase current. An orthogonal component of the current Io with respect to the reference vector Ivc is calculated. The result of dividing this calculation result by cos 30 ° is the resistive current Ir that flows as the ground insulation resistance decreases.

  In the case of the present embodiment, the calculation of the above-described equation (1) (Ir = Io · Ivc · sinθ) is outputted from the “zero phase current Io” outputted from the current measuring means 11 and the reference vector phase correcting means 15. The sampling data of each “reference vector Ivc” is used. This calculation can be calculated by, for example, the following equation (2) when the sampling data is data every 30 ° in electrical angle.

Ir = Io ・ Ivc ・ sinθ
_{= Io m-3 · Ivc m} -Io m · Ivc m-3 ...... (2)
However, if the subscript _m is the current sampling data,
_m-3 means the data before 3 samplings (90 °).

The insulation monitoring determination means 17 is in the secondary circuit of the power receiving transformer 1 that constitutes the electrical equipment based on the magnitude of the resistive current Ir that flows along with the decrease in the ground insulation resistance calculated by the orthogonal component calculation means 16. The presence or absence of insulation failure is determined and the determination result is output. For example, when the following expression (3) is satisfied, that is, when the magnitude (absolute value) of the resistive current Ir is equal to or higher than the detection level Ik of the predetermined insulation failure determination, the determination of insulation failure “present” is made. Do.
| Ir | ≧ Ik (3)

  In determining whether or not insulation failure has occurred, the detection level Ik is not set to a single value, but a plurality of detection levels Iki (i = 2 to n) that are slightly different in size are used to determine the degree of insulation failure. ) May be set. As described above, when the insulation monitoring determination means 17 provides a plurality of detection levels for insulation failure determination, it is possible to distinguish and output the alarm output for each detection level. Since it is possible to determine the degree of insulation failure according to the type, it is possible to make a prior situation determination more accurately.

  Further, in order to obtain a more reliable detection operation, an operation time period and a return time period may be provided. This is to determine that the insulation failure is “present” on condition that the state of the expression (3) continues for a preset operation time period. With regard to the return time, it is determined that the insulation failure has been recovered once it is determined that the insulation failure is “present” and then the state in which equation (3) is not satisfied continues for the preset return time. It is.

The alarm output means 18 outputs an alarm for notifying the outside of the occurrence of an insulation failure from the insulation monitoring device _10-1 when the insulation monitoring judgment means 17 determines that the insulation failure is “present”, and is necessary. If an insulation failure is restored, an alarm return is output. Various means such as contact output, wireless communication output, wired communication output, power line conveyance, and the like can be considered as alarm output means, but the means is not limited.

Next, features of the present embodiment will be described.
As described above, in the state where the charging current is balanced, since the charging current Ic and the resistive current Ir have an orthogonal relationship, the reference vector Ivc having the same phase as the charging current Ic is generated, and the reference vector The resistive current component can be accurately extracted by deriving the orthogonal component. However, when the charging current is in an unbalanced state, the orthogonal relationship described above is lost, which results in a detection error when calculating the resistive current.

  On the other hand, when insulation failure occurs, the phase of the zero-phase current Io changes greatly. It can be considered that the phase of the zero-phase current Io immediately before this change best represents the state of the charging current. Because the charging current is unbalanced, a strict orthogonal relationship is not established between the charging current before this change and the resistive current, but it can be considered that the orthogonal relationship is approximately established. For example, the detection accuracy of the resistive current can be greatly improved by obtaining the quadrature component after correcting the phase of the reference vector so as to be in phase with the charging current before the change.

  Further, effects of the present embodiment will be described with reference to the drawings. As described above, FIG. 16 is a vector diagram showing the relationship between each quantity of electricity in a state where the charging current is unbalanced in an electrical facility using a three-phase Δ (V) connection power receiving transformer. . In this case, the charging current of the electric equipment as a whole is Ic ', but since it is in an unbalanced state, the phase is different from the non-grounded interphase voltage Vca. Further, when the resistive current Ira due to the insulation failure occurs, the zero-phase current of the entire electrical equipment becomes Io ′, and the current transformer coupled to the ground line 3 extracts this Io ′.

  When the non-grounded phase voltage is used as the reference vector Ivc in the configuration of the insulation monitoring apparatus and the orthogonal component of the zero-phase current Io ′ with respect to this reference vector is obtained, the size of the double line in FIG. 16 is obtained. The value 1 / cos 30 ° (about 1.15) obtained by further dividing this by cos 30 ° is treated as the resistive current value, and this magnitude is clearly larger than the resistive current Ira from FIG. It can be seen that a large detection error occurs.

  FIG. 2 is a graph specifically showing the above description. This is calculated on the assumption that the magnitude of the charging current is 300 mA and the phase difference between the non-ground phase voltage Vca and the charging current Ic ′ is 2 ° (Ic ′ is a phase lag). The magnitude of the resistive current is used as a parameter, and the magnitude of the detected current is represented on the vertical axis.

  The characteristic plotted with “rhombus” represents the ideal detection value (Ior), that is, the true resistance current, and the characteristic plotted with “square” (without Igr correction) represents the voltage between the ungrounded phases. This is the result when the resistive current is calculated using the direction as a reference vector. As is apparent from the graph of FIG. 2, it is apparent that a large detection error occurs when the non-ground phase voltage direction is the reference vector.

  On the other hand, FIG. 3 is a vector diagram showing a process of introducing a resistive current in the configuration of FIG. 1 of the first embodiment. The unbalanced state of the charging current and the magnitude of the resistive current are expressed together with FIG. The state of the charging current before the occurrence of the insulation failure is Ic ′, and when the insulation failure occurs and the resistive current Ira is generated, the zero-phase current measured by the current transformer becomes Io ′.

  In the first embodiment, the reference vector generated by the reference vector phase correction means 15 is phase-corrected in the same phase as the zero-phase current (Ic ′) before the phase of the zero-phase current changes due to the occurrence of insulation failure. Then, the resistive current is calculated as an orthogonal component with respect to the corrected reference vector of the zero-phase current Io ′. That is, the size of the double line in FIG. 3 is obtained. A value obtained by further dividing this by cos 30 ° (about 1.15 times) is handled as a resistive current value, but it is clearly understood that the detection error is reduced as compared with the case described in FIG.

  As described above, in the trial calculation example shown in FIG. 2, the result of calculating the resistive current in the configuration of the first embodiment is plotted with “triangle” (with Igr correction). It can be seen that the detection error is greatly improved.

  As described above, according to the present embodiment, in the electrical equipment where the three-phase Δ (V) -connected power receiving transformer is installed, even if the charging current flowing through the ground wire is unbalanced, Since the detection error corresponding to the resistive current flowing along with the decrease in the ground insulation resistance is small, it is possible to provide an insulation monitoring method and apparatus for electrical equipment that can more accurately detect an insulation failure.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.
The second embodiment is a modification of the first embodiment. In the block diagram shown in FIG. 1, the second embodiment is the same as the first embodiment except that the calculation content of the reference vector phase correction means 15 is changed. .

  In the reference vector phase correction means 15 in the second embodiment, the phase angle of the reference vector generated by the reference vector generation means 13 is obtained, and further, the phase of the zero phase current obtained by the charging current vector phase angle estimation means 14 is obtained. Find the absolute value of the difference from the corner.

  If this phase difference is within a predetermined value, the phase of the reference vector generated by the reference vector generation unit 13 is corrected so as to be in phase with the zero-phase current data output from the charging current vector phase angle estimation unit 14. When the phase difference is larger than a predetermined value, the reference vector generated by the reference vector generation unit 13 is used as it is as a reference vector.

  FIG. 4 is a vector diagram showing a process of deriving a resistive current based on selection of a reference vector and the reference vector in the second embodiment.

  The charging current of the entire electrical equipment is Ic, but the phase is different from the non-grounded interphase voltage Vca because it is in an unbalanced state. Further, when a resistive current Ira is generated due to an insulation failure, the zero-phase current of the entire electrical equipment becomes Io ′, and this Io ′ is measured by a current transformer installed on the ground line.

  In FIG. 4, the predetermined value is represented by a shaded triangle. However, when the resistive current Ira is generated due to the occurrence of insulation failure, the zero-phase current Io ′ deviates from this region. The reference vector Ivc = Vca (thick line in FIG. 4) generated by the reference vector generation means 13 is selected as a vector, and the resistive current is calculated as an orthogonal component to this reference vector, that is, a double line in FIG.

  In the second embodiment, the reference vector phase correction means 15 is configured as described above, thereby reducing detection errors caused by unbalanced charging currents when the resistive current is relatively small. It is possible to provide an insulation monitoring method and apparatus for electrical equipment capable of improving the detection of a resistive current when the insulation failure gradually progresses.

(Third embodiment)
Next, a third embodiment of the present invention will be described.
The third embodiment is a modification of the first embodiment. In the block diagram shown in FIG. 1, the third embodiment is the same as the first embodiment except that the calculation content of the reference vector phase correction means 15 is changed.

  In the reference vector phase correction means 15 in the third embodiment, the phase angle of the reference vector generated by the reference vector generation means 13 is obtained, and further, the phase of the zero phase current obtained by the charging current vector phase angle estimation means 14 is obtained. Find the absolute value of the difference from the corner. If this phase difference is within a predetermined value, the phase of the reference vector generated by the reference vector generation unit 13 is corrected so as to be in phase with the zero-phase current data output from the charging current vector phase angle estimation unit 14. When the phase difference is larger than a predetermined value, the upper limit value direction (leading phase side) of the predetermined value is used as a reference vector.

  FIG. 5 shows a vector diagram showing the selection of the reference vector and the process of deriving the resistive current based on the reference vector in the third embodiment. The content of the calculation is the same as in the case of the second embodiment. So I will omit it and explain only the effect.

  According to the third embodiment, since the insulation vector failure is detected with higher sensitivity by configuring the reference vector phase correction means 15 in this way, the insulation monitoring of the electrical equipment capable of a reliable alarm operation is performed. Methods and apparatus can be provided.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described.
The fourth embodiment is a modification of the first embodiment. In the block diagram shown in FIG. 1, the fourth embodiment is the same as the first embodiment except that the implementation content of the reference vector phase correction means 15 is changed.

  In the reference vector phase correction means 15 in the fourth embodiment, the phase angle of the reference vector generated by the reference vector generation means 13 is obtained, and the phase of the zero-phase current obtained by the charging current vector phase angle estimation means 14 is obtained. Find the absolute value of the difference from the corner.

  If this phase difference is within a predetermined value, the phase of the reference vector generated by the reference vector generation unit 13 is corrected so as to be in phase with the zero-phase current data output from the charging current vector phase angle estimation unit 14. When the phase difference is larger than a predetermined value, the lower limit value direction (delayed phase side) of the predetermined value is used as a reference vector.

  FIG. 6 shows a vector diagram showing the selection of the reference vector and the process of deriving the resistive current based on the reference vector in the fourth embodiment, but the content is the same as in the case of the second embodiment, and is omitted. Only the effect will be described.

  By providing the reference vector phase correction means 15 as described above, an insulation failure can be detected with lower sensitivity, and therefore, an insulation monitoring method and apparatus for electrical equipment capable of preventing false alarms are provided. Can do.

(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described.
The fifth embodiment is a modification of the first embodiment. In the block diagram shown in FIG. 1, the fifth embodiment is the same as the first embodiment except that the calculation content of the reference vector phase correction means 15 is changed.

  In the reference vector phase correction means 15 in the fifth embodiment, the phase angle of the reference vector generated by the reference vector generation means 13 is obtained, and further, the phase of the zero phase current obtained by the charging current vector phase angle estimation means 14 is obtained. Find the absolute value of the difference from the corner.

  If this phase difference is within a predetermined value, the phase of the reference vector generated by the reference vector generation unit 13 is corrected so as to be in phase with the zero-phase current data output from the charging current vector phase angle estimation unit 14. If the phase difference is larger than a predetermined value, the phase of the zero-phase current output from the charging current vector phase angle estimating means 14 before the deviation from the predetermined value is the same as the most advanced phase. The phase of the reference vector generated by the reference vector generation means 13 is corrected so as to be in phase.

  This is because when the resistive current is generated due to the occurrence of insulation failure, the phase of the zero-phase current always changes in the lagging direction, so that the most advanced phase will be the state of only the charging current not including the resistive current. This is based on the idea.

  FIG. 7 shows a vector diagram showing the selection of the reference vector and the process of deriving the resistive current based on the reference vector in the fifth embodiment, but the calculation content is the same as in the case of the second embodiment. Omit.

  By providing the reference vector phase correction means 15 as described above, it is possible to provide an insulation monitoring method and apparatus for electrical equipment that can detect a resistive current more accurately, as in the first embodiment. Can do.

(Sixth embodiment)
Next, a sixth embodiment of the present invention will be described with reference to FIG.
The insulation monitoring device _10-2 shown in FIG. 8 is obtained by adding valid / invalid setting means 19 to the insulation monitoring device _10-1 shown in FIG. This is for switching whether or not to perform the reference vector correction operation in the reference vector phase correction means 15. Except for this point, the second embodiment is the same as the first to fifth embodiments already described.

  The valid / invalid setting means 19 is a means for setting whether the reference vector correction operation is performed (valid) or not (invalid), and whether the correction is valid for the reference vector phase correction means 15. It functions to pass the setting information of invalid or invalid.

  In the reference vector phase correction unit 15, when the setting information passed from the valid / invalid setting unit 19 is “valid”, the reference vector correction operation shown in the first to fifth embodiments is performed, and the corrected reference vector is obtained. The output is made to the orthogonal component calculation means 16. On the other hand, when the “invalid” setting information is passed, the reference vector phase correction unit 15 does not perform any correction on the reference vector generated by the reference vector generation unit 13 and directly supplies the orthogonal component calculation unit 16 with it. On the other hand, the reference vector is output to the orthogonal component calculation means 16.

As a specific method of setting valid / invalid in the valid / invalid setting means 19, for example, a switching switch is provided, a PC (personal computer) is connected to the insulation monitoring device, settings are performed, or wireless or wired from a remote location. Methods such as setting via communication are conceivable, but the present embodiment is not limited to these setting methods. Further, instead of performing setting switching from the outside, either a valid or invalid setting may be set as a default setting in the insulation monitoring device _10-2 in advance.

  The magnitude of the detected value error due to the unbalanced charging current depends on the magnitude of the charging current or the degree of unbalanced. That is, in an electrical installation with a small charging current or almost no unbalance, the first to first cases may be used in some cases rather than calculating the resistive current without correcting the reference vector in the reference vector phase correction means 15. The detection error of the resistive current may be larger when the phase correction shown in the fifth embodiment is performed. Accordingly, the valid / invalid setting means 19 is provided so that the validity / invalidity of the correction operation of the reference vector in the reference vector phase correction means 15 can be switched, so that the electric equipment to which the insulation monitoring device is applied more appropriately. It is possible to provide an insulation monitoring method and apparatus for electrical equipment capable of performing insulation monitoring.

(Seventh embodiment)
Next, a seventh embodiment of the present invention will be described.
The configuration of the seventh embodiment is equivalent to the block diagram shown in FIG. 1 or FIG. 8, and will be described here using the block diagram of FIG.

  The seventh embodiment relates to the calculation of the phase angle of the zero-phase current Io in the charging current vector phase angle estimating means 14, and the other points are the same as those in the first to sixth embodiments, so that the description thereof is omitted. Only the calculation of the phase angle of the zero-phase current Io will be described.

  The charging current vector phase angle estimating means 14 calculates the phase angle of the zero-phase current Io passed from the current measuring means 11, but calculates the magnitude of the zero-phase current Io before calculating the phase angle. When the phase angle is larger than a predetermined value, the phase angle is calculated.When the phase angle is smaller than the predetermined value, the latest phase angle calculated in the past is selected. It is configured to output to the reference vector phase correcting means 15 together with the zero phase current Io data.

  In the case of the voltage amount, the magnitude is almost constant in the steady state. Therefore, the calculation of the phase angle may be performed using the data taken in as it is, but the magnitude of the zero-phase current is Depends on the electrical equipment and its condition. The phase angle calculated by the charging current vector phase angle estimating means 14 is one data when the reference vector phase correcting means 15 finally generates the reference vector, and accuracy is required for the result.

  When the magnitude of the zero-phase current Io is small, the result of the phase angle calculation includes a relatively large error and the accuracy cannot be ensured. An accurate phase angle result can be output by calculating the phase angle only when the magnitude of Io is sufficiently large to ensure the accuracy of phase angle calculation.

  By configuring the charging current vector phase angle estimating means 14 as described above, the phase angle of the zero phase current Io can be accurately calculated without depending on the magnitude of the zero phase current Io. As a result, the reference vector It is possible to provide an insulation monitoring method and apparatus for electrical equipment that can generate an accurate reference vector by the phase correction means 15 and improve the detection accuracy of the resistive current by the orthogonal component calculation means 16.

(Eighth embodiment)
Next, an eighth embodiment of the present invention will be described.
The configuration of the eighth embodiment is equivalent to the block diagram shown in FIG. 1 or FIG. 8, and will be described here with reference to FIG. 1 and FIG.

  In the eighth embodiment, the reference vector generation method in the reference vector generation means 13 will be described. Except for this point, the reference vector generation means 13 is the same as the first to seventh embodiments. A generation method will be described. The reference vector generation unit 13 generates a reference vector having the same phase as the charging current of the entire electrical equipment based on the voltage taken in by the voltage measurement unit 12. The case where the voltage taken in by the voltage measuring means 12 is a non-ground phase voltage will be described as an example with reference to FIG.

  FIG. 9 shows the power supply voltage of the insulation monitoring device on the coordinate space as 0 ° direction (i) and the non-grounded interphase voltage Vca taken by the voltage measuring means 12 as 150 ° direction (vi). Actually, the power supply voltage is acquired from a single-phase circuit, and since it is arbitrary from which phase it is acquired, the vector relationship in FIG. 9 is an example.

  In FIG. 9, Vca is an actual non-ground phase voltage, and Vca ′ is a voltage measured by the voltage measuring means 12. Originally, since these are the same amount of electricity, the vectors should match, but in reality, due to the measurement unit error of the voltage measuring means 12, it is measured in a different form as shown in FIG. . As described above, the phase relationship between the power supply voltage of the insulation monitoring device and the non-grounded interphase voltage Vca is arbitrary, but since this phase relationship is determined by the connection and phase arrangement of the transformer, the power supply voltage of the insulation monitoring device is used as a reference. It corresponds to any one of the phases in increments of 30 °. That is, when the power supply voltage of the insulation monitoring device is considered to be in the 0 ° direction, the non-grounded interphase voltage Vca is a vector in any one of the directions (i) to (xii) in increments of 30 ° shown in FIG. The reference vector generation means 13 utilizes this point, and when it is the voltage Vca ′ measured by the voltage measurement means 12, this Vca ′ is the most in phase with (i) to (xii) in 30 ° increments. In the case of FIG. 9, the direction of (vi) is set as the reference vector.

  By configuring the reference vector generation unit 13 in this way, it is possible to generate an accurate reference vector without being affected by the measurement unit error of the voltage measurement unit 12, and thus improve the detection accuracy of the resistive current. It is possible to provide an insulation monitoring method and apparatus for electrical equipment that can be used.

  In particular, when an insulation monitoring device is installed, a non-contact measurement method in which voltage measurement by the voltage measurement means 12 is performed without directly touching a live part may be taken to ensure work safety. In the contact measurement method, safety is ensured, but measurement accuracy is poor. Therefore, the accuracy can be greatly improved by adopting the above-described reference vector generation method.

(Ninth embodiment)
Next, a ninth embodiment of the present invention will be described.
The configuration of the ninth embodiment is equivalent to the block diagram shown in FIG. 1 or FIG. 8, and will be described here using the block diagram of FIG. 1 and the vector diagram of FIG.

  The ninth embodiment relates to the phase angle correction of the reference vector in the reference vector phase correction means 15, and since this is the same as the first to eighth embodiments except for this point, the description is omitted. The phase angle correction method will be described. However, the phase correction method for the reference vector will be described with reference to the contents of the first embodiment.

The reference vector phase correction means 15 calculates the magnitude of the change in the zero phase current Io ′ passed from the charging current vector phase angle estimation means 14 and the zero phase current Io passed a predetermined time ago. When the magnitude is larger than a predetermined value, that is, when the formula (4) is satisfied, the reference vector corrected based on the zero-phase current Io passed before a predetermined time is used as it is, and the formula (4) is used. Is not established, the phase of the reference vector generated by the reference vector generation unit 13 is corrected so as to be in phase with the latest zero-phase current Io ′ passed from the charging current vector phase angle estimation unit 14. To do.
| ΔIo | = | Io′−Io | ≧ ΔIk1 (4)
However, ΔIk1 is a determination constant for detecting a change in Io.

This will be described with reference to FIG.
FIG. 10 is a vector diagram showing the amount of electricity before and after the occurrence of insulation failure, particularly the state of the zero-phase current, when applied to electrical equipment using a three-phase Δ (V) -connected power receiving transformer. .

  In FIG. 10, the zero-phase current in a state where no insulation failure has occurred is defined as Io. This is a state of only charging current. Here, when insulation failure occurs and the resistive current Ira is generated, this amount is added in a vector manner, and the zero-phase current becomes Io ′. At this time, the double line shown in FIG. 10 is ΔIo calculated by the equation (4).

  Generally, the charging current depends on the configuration and operating state of the electrical equipment, so it does not fluctuate so much in the steady state, but as can be seen from FIG. 10, the zero-phase current changes greatly when insulation failure occurs. Will do. Therefore, the reference vector phase correction means 15 detects the occurrence of insulation failure based on the change in the zero-phase current, and when insulation failure occurs, the zero-phase in the state of only the charging current immediately before the insulation failure occurs. By using the direction in phase with the current as the reference vector, it is possible to obtain the same effect as that of the first embodiment, and, moreover, the insulation monitoring method and apparatus for electrical equipment capable of more accurately detecting the resistive current component. Can be provided.

(Tenth embodiment)
Next, a tenth embodiment of the present invention will be described.
The configuration of this embodiment is the same as the block diagram shown in FIG. 1 or FIG. 8, and will be described here using the block diagram of FIG. 1 and the vector diagram of FIG.

  The tenth embodiment is related to the phase angle correction of the reference vector in the reference vector phase correction means 15, and other than this point is the same as the first to eighth embodiments, so the description is omitted, and the reference vector The phase angle correction method will be described. However, the phase correction method for the reference vector will be described with reference to the contents of the first embodiment.

In the reference vector phase correction means 15, the zero-phase current Io ′ passed from the charging current vector phase angle estimation means 14 is expressed by the formula (5), and the zero-phase current Io passed a certain predetermined time is expressed by the formula (6). In this case, the change in Io ′ and Io is calculated as shown in equation (7).
Io ′ = (Iox ′, Ioy ′) (5)
Io = (Iox, Ioy) (6)
△ Io = (△ Iox, △ Ioy)
= (Iox'-Iox, Ioy'-Ioy) (7)

  The ratio of the magnitudes of the X component and the Y component of the change in the zero-phase current calculated by the equation (7) is obtained by the following equation (8), and this equation (8) may be satisfied in some predetermined case. The reference vector corrected based on the zero-phase current Io passed before time is used as it is, and when the equation (8) is not satisfied, the latest zero-phase current Io ′ passed from the charging current vector phase angle estimation means 14 is used. The phase of the reference vector generated by the reference vector generation means 13 is corrected so as to have the same phase as.

但し、△Iｋ２はIｏの変化の比率を検出する判定定数である。

However, ΔIk2 is a determination constant for detecting the rate of change of Io.

This will be described with reference to FIG.
FIG. 11 is a vector diagram showing the amount of electricity before and after the occurrence of insulation failure, especially the state of zero-phase current, when applied to electrical equipment using a three-phase Δ (V) -connected power receiving transformer. 10 represents the same state as in FIG. 10, but each vector in FIG. 10 is represented with the phase advanced by 30 °. That is, the non-grounded phase voltage Vca of the electrical equipment is expressed in the form of matching the negative direction of the X coordinate axis, and in this embodiment, the coordinate space expressed in this way is considered.

  When the vector of each quantity of electricity is expressed in the coordinate space shown in FIG. 11, the resistive current is in the direction of 60 ° when insulation failure occurs in the a phase, and in the direction of 120 ° when insulation failure occurs in the c phase, that is, the Y axis. This is a vector in the direction of ± 30 ° about the (+ direction).

  On the other hand, the charging current is a vector in the direction of 150 ° for the a phase and 210 ° for the c phase, that is, a direction of ± 30 ° about the X axis (− direction).

  From the above, when insulation failure occurs, the change vector of the zero-phase current obtained by the equation (7) shows a large change in the Y component compared to the X component, and vice versa when the charging current fluctuates. Compared with the Y component, the X component has a characteristic that changes greatly.

  In this embodiment, this feature is utilized, and the reference vector phase correction means 15 obtains the change in the zero-phase current and detects the occurrence of insulation failure by performing the determination of equation (8). When an insulation failure occurs, the same effect as that of the first embodiment can be obtained by using the zero-phase current in the state of only the charging current immediately before the insulation failure occurs as a reference vector. It is possible to provide an insulation monitoring method and apparatus for electrical equipment that can detect the minute more accurately.

  For example, if a resistive current is generated due to the occurrence of insulation failure, the ratio of the left side of equation (8) is about 1.73, so it is considered that ΔIk2 is preferably set to this value.

In the tenth embodiment, the reference vector phase correction means 15 detects the occurrence of insulation failure in the electrical equipment by the equation (8) and switches the reference vector phase correction. By adding the expression (4) as an AND condition, a more reliable determination operation can be performed.
Further, the determination of equation (8) may be performed by a simple method as shown in equation (9).

| △ Ioy | ≧ △ Ik3 (9)
However, ΔIk3 is a determination constant for detecting an increase in the X component of the change in Io.

The block diagram which shows the structure of the insulation monitoring apparatus of the electrical installation which concerns on the 1st Embodiment of this invention. The figure which shows the graph explaining the effect by reference | standard vector correction implementation presence / absence at the time of charging current imbalance. The figure explaining the correction method at the time of charging current imbalance. The vector diagram explaining operation | movement of the 2nd Embodiment of this invention. The vector diagram explaining operation | movement of the 3rd Embodiment of this invention. The vector diagram explaining operation | movement of the 4th Embodiment of this invention. The vector diagram explaining operation | movement of the 5th Embodiment of this invention. The block diagram which shows the structure of the insulation monitoring apparatus of the electrical installation which concerns on the 6th Embodiment of this invention. The vector diagram explaining operation | movement of the 7th Embodiment of this invention. The vector diagram explaining operation | movement of the 8th Embodiment of this invention. The vector diagram explaining operation | movement of the 9th Embodiment of this invention. The block diagram explaining the structure of the conventional Io system. The block diagram explaining the structure of the conventional Igr system. The block diagram explaining the structure of the conventional Ior system. The vector figure showing the relationship of each electric quantity in the case of a three-phase (DELTA) (V) connection power receiving transformer when charging current is balanced. The vector figure showing the relationship of each electric quantity in the state where charging current is unbalanced in a three-phase Δ (V) -connected power receiving transformer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Power receiving transformer, 2 ... Cable, 3 ... Ground line, 4 ... Current transformer, 10 _{< -1} >, 10 _<-2> ... Insulation monitoring apparatus, 11 ... Current measuring means, 12 ... Voltage measuring means, 13 ... Reference vector Generation means 14... Charging current vector phase angle estimation means 15. Reference vector phase correction means 16. Orthogonal component calculation means 17. Insulation monitoring determination means 18. Alarm output means 19. Valid / invalid setting means.

Claims (8)

Current measuring means for capturing a zero-phase current flowing in the ground wire of the transformer constituting the electrical facility;
Voltage measuring means for taking in the voltage of the electrical equipment;
A reference vector generating means for generating a reference vector based on the voltage of the electrical equipment taken in by the voltage measuring means and storing the reference vector;
Charging current vector phase angle estimating means for obtaining the phase angle of the zero-phase current taken in by the current measuring means;
The difference between the phase angle of the reference vector generated by the reference vector generation means and the phase angle of the zero-phase current measured by the charging current vector phase angle estimation means is obtained, and the absolute value of this phase difference is predetermined. A reference vector phase correction unit that switches a correction method depending on whether or not the value is equal to or less, and corrects the phase angle of the reference vector
Orthogonal component computing means for obtaining an orthogonal component of the zero-phase current measured by the current measuring means with respect to the reference vector phase-corrected by the reference vector phase correcting means;
Insulation monitoring determination means for detecting the presence or absence of insulation failure of the electrical equipment based on the size of the orthogonal component calculated by the orthogonal component calculation means;
Output means for outputting that when the insulation monitoring judgment means judges that there is insulation failure;
An insulation monitoring device for electrical equipment, comprising:   The reference vector phase correction means has a predetermined value in which the phase difference between the phase angle of the reference vector generated by the reference vector generation means and the phase angle of the zero-phase current measured by the charging current vector phase angle estimation means is predetermined. The phase of the reference vector is corrected so as to be in phase with the zero-phase current when the phase difference is within the range, and when the phase difference exceeds a predetermined value, the previously obtained reference vector is adopted. The insulation monitoring apparatus of the electrical installation of description.   Validity / invalidity setting means for setting whether the execution of the reference vector phase correction by the reference vector phase correction means is valid or invalid is provided, and the reference vector phase correction means sets the reference vector only when it is set to valid. The insulation monitoring device for electrical equipment according to claim 1 or 2, characterized in that phase correction is performed.   In the charging current vector phase angle estimation means, when obtaining the phase angle of the zero-phase current, the phase angle is obtained only when the zero-phase current is greater than or equal to a predetermined magnitude, and when the zero-phase current is smaller than the prescribed magnitude, it is obtained last time. 4. The electrical equipment insulation monitoring apparatus according to claim 1, wherein the phase angle is used as it is.   When generating the reference vector based on the voltage taken from the electrical equipment by the voltage measuring means by the reference vector generating means, the reference vector is taken from the electrical equipment from the phase of 30 ° with reference to the power supply voltage of the monitoring device. The insulation monitoring method and apparatus for electrical equipment according to any one of claims 1 to 4, wherein the one closest to the phase of the input voltage is selected and used as a reference vector.   The phase angle correction of the reference vector by the reference vector phase correction unit is switched according to whether or not the change in the magnitude of the zero-phase current measured by the current measurement unit at a predetermined time interval is equal to or less than a predetermined value, 6. The electrical equipment insulation monitoring apparatus according to claim 1, wherein a phase angle of the reference vector is corrected.   The phase angle correction of the reference vector by the reference vector phase correction means is switched according to the variation direction of the zero-phase current vector measured by the current measurement means, and the phase angle of the reference vector is corrected. The insulation monitoring apparatus for electrical equipment according to any one of claims 1 to 5.   The zero-phase current flowing in the ground wire of the transformer constituting the electrical equipment is taken, the phase angle of the zero-phase current is obtained, the voltage of the electrical equipment is taken in by the voltage measuring means, and the reference vector is generated based on the voltage. The difference between the phase angle of the reference vector and the phase angle of the zero-phase current is obtained from the phase angle of the reference vector and the phase angle of the zero-phase current, and the absolute value of this phase difference is equal to or smaller than a predetermined value. In this case, the phase angle of the reference vector is corrected so as to be in phase with the zero-phase current, an orthogonal component with respect to the reference vector whose phase has been corrected is obtained, and the electrical equipment is installed by the insulation monitoring determination means based on the magnitude of the orthogonal component An insulation monitoring method for electrical equipment, wherein the presence or absence of insulation failure is detected, and when it is determined that there is insulation failure, the fact is output.

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