WO2016047057A1 - 漏洩電流算出装置及び漏洩電流算出方法 - Google Patents
漏洩電流算出装置及び漏洩電流算出方法 Download PDFInfo
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- WO2016047057A1 WO2016047057A1 PCT/JP2015/004519 JP2015004519W WO2016047057A1 WO 2016047057 A1 WO2016047057 A1 WO 2016047057A1 JP 2015004519 W JP2015004519 W JP 2015004519W WO 2016047057 A1 WO2016047057 A1 WO 2016047057A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/52—Testing for short-circuits, leakage current or ground faults
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
- H02H3/32—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors
- H02H3/34—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors of a three-phase system
- H02H3/347—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors of a three-phase system using summation current transformers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/38—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to both voltage and current; responsive to phase angle between voltage and current
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/34—Testing dynamo-electric machines
- G01R31/346—Testing of armature or field windings
Definitions
- the present invention relates to a leakage current calculation device and a leakage current calculation method for extracting and measuring a component caused by a ground insulation resistance value in a circuit among leakage currents flowing in a circuit having a predetermined protective conductor.
- the present invention relates to a leakage current calculation apparatus and a leakage current calculation method for extracting and measuring a component caused by a ground insulation resistance value, excluding a ground capacitance component, from a flowing leakage current.
- a leakage current measuring device described in Patent Document 1 (hereinafter referred to as “device 1”) has an R phase on the secondary side of a three-phase transformer in which a secondary winding is connected in a ⁇ (delta) type.
- the line voltage V RT between the T phase and the T phase (or the line voltage V TS between the T phase and the S phase or the line voltage V SR between the S phase and the R phase) is measured, and this three-phase transformer Measure the zero-phase current I 0 flowing in the distribution line connecting the secondary side of the load and the load device, and use the line voltage V RT (or V TS or V SR ) as the reference voltage.
- the zero-phase current I 0 is calculated, and the zero-phase current I 0 is divided into an active component having the same phase as the reference voltage and an ineffective component having a phase difference of 90 ° with respect to the reference voltage.
- the effective component is calculated as the leakage current I 0 r.
- the device 1 can calculate the leakage current I 0 r even when the load device (for example, a motor) is in an operating state and the electric circuit is in a live line state.
- a device for measuring the leakage current I 0 r such as the device 1 described above, has conventionally existed. Such a measuring device is required to measure the leakage current I 0 r more accurately.
- an error may occur in the measured leakage current I 0 r due to various factors. It has been a problem in designing the measurement apparatus to eliminate the factor causing such an error as much as possible and accurately measure the leakage current I 0 r.
- the present invention has been made to solve these problems, and it is possible to accurately calculate the leakage current I 0 r which is a component resulting from the ground insulation resistance value of the electric circuit among the leakage current I 0 flowing through the electric circuit. In addition, it is possible to calculate the leakage current I 0 r with high accuracy even when the leakage current I 0 c flowing due to the ground capacitance in the electric circuit equipment installed in a large factory or the like is large. It is an object of the present invention to provide a leakage current calculation device and a leakage current calculation method.
- the leakage current calculation apparatus of the present invention extracts a leakage current flowing in an electric circuit having a predetermined protective conductor and extracts a component caused by the ground insulation resistance value in the electric circuit and measures the leakage current.
- Current measuring means for measuring the leakage current flowing in the circuit, and each phase that is a voltage between each phase of the power supply section of the circuit and the E phase when the protective conductor is an E phase ⁇ Based on the voltage between each phase and the E phase, a predetermined voltage value extracted from the voltage component applied to the ground insulation resistance, excluding the potential difference caused by the ground resistance of the protective conductor and the voltage measuring means for measuring the E phase voltage.
- a voltage value calculating means for calculating and a current value calculating means for extracting a component caused by the ground insulation resistance value excluding the ground capacitance component from the leakage current based on the predetermined voltage value. is there.
- the leakage current calculation method of the present invention is a leakage current calculation method for extracting and measuring a component due to the ground insulation resistance value in the electric circuit out of the leakage current flowing in the electric circuit having a predetermined protective conductor, Measures the leakage current flowing in the circuit, and measures the voltage between each phase and E phase, which is the voltage between each phase of the power supply section of the circuit and the E phase when the protective conductor is E phase.
- Voltage value calculation that calculates a predetermined voltage value extracted from the voltage component applied to the ground insulation resistance, excluding the potential difference caused by the voltage measurement process and the ground resistance of the protective conductor, based on the voltage between each phase and E phase
- the method includes a step and a current value calculation step of extracting a component caused by the ground insulation resistance value from the leakage current, excluding the ground capacitance component, based on a predetermined voltage value.
- the predetermined voltage value obtained by extracting the voltage component applied to the ground insulation resistance, excluding the potential difference caused by the ground resistance of the protective conductor, is obtained for each phase ⁇ E.
- the leakage current I 0 r which is a component derived from the ground insulation resistance value excluding the ground capacitance component I 0 c from the leakage current I 0 , is calculated based on the interphase voltage. Since the calculation is performed by extraction, the leakage current I 0 r can be calculated with high accuracy. Further, even when the leakage current I 0 c flowing due to the ground capacitance in the electric circuit laid in a large factory or the like is large, the leakage current I 0 r can be calculated with high accuracy.
- Phase -E interphase voltage V ER, V ES illustrates each vector of V ET.
- R-phase -E interphase voltage V ER and T-phase -E interphase voltage V ET is a diagram showing the vector of the combined voltage V ERT.
- Phase -E interphase voltage V ER, V ES is a diagram showing the vector of voltage V ERST obtained by combining the V ET.
- the vector of the combined voltage V ERST illustrates the direction of the leakage current I 0 r flowing due to ground insulation resistance, the direction of the leakage current I 0 c flowing due to the earth capacitance.
- the electric circuit A has a three-phase three-wire distribution system.
- the electric circuit A includes a three-phase transformer 1, an inverter device 2, a load device 3, and a distribution line 4.
- the three-phase transformer 1 is a power supply unit that converts an AC voltage on the primary side into an AC voltage on the secondary side and outputs the converted voltage, and a connection method of the secondary side winding is a delta connection.
- One of the R-phase, S-phase, and T-phase (the S-phase in FIG. 1), which is the secondary phase of the three-phase transformer 1, is B-type grounded.
- Class B grounding is grounding that is connected to the ground so that the grounding resistance value is equal to or less than the grounding resistance value of Class B grounding work defined in the interpretation of the technical standards for electrical equipment.
- ground phase an electrode buried in the ground in order to perform this type B grounding is defined as a grounding electrode gpb.
- a wiring connecting the ground electrode gpb and the ground phase (S phase) is defined as a ground line gcb.
- the inverter device 2 receives an AC voltage output from the secondary side of the three-phase transformer 1 and receives a voltage based on the AC voltage (for example, an AC voltage obtained by converting the frequency of the input AC voltage). Output and send to the load device 3. Note that the R phase, S phase, and T phase of the three-phase transformer 1 are connected to the input side of the inverter device 2. Further, the power input terminals U, V, W of the motor 3a are connected to the output side of the inverter device 2.
- the load device 3 is a device that inputs a voltage output from the inverter device 2 and performs a predetermined operation.
- a motor 3a is given.
- the motor 3a inputs the AC voltage output from the inverter device 2 as a power supply voltage, and causes an AC current to flow through each winding to rotate the rotating shaft.
- the housing of the motor 3a is D-type grounded to prevent electric shock.
- Class D grounding is grounding that is connected to the ground so that the grounding resistance value is equal to or less than the grounding resistance value of class D grounding work defined in the interpretation of technical standards for electrical equipment. Let RD be the ground resistance value of this type D ground.
- the motor 3a housing is provided with a ground terminal gt which is a terminal for performing D-type grounding. Further, an electrode buried in the ground in order to perform this type D grounding is referred to as a grounding electrode gpd. A wire connecting the ground terminal gt of the motor 3a and the ground electrode gpd is referred to as a ground wire gcd. In this way, by connecting the ground terminal gt of the motor 3a and the grounding electrode gpd buried in the ground with the grounding wire gcd, the housing of the motor 3a can be subjected to D-type grounding.
- the motor 3a is described as an example of the load device 3.
- the load device 3 is not limited to the motor 3a, and may be a device that inputs a three-phase AC voltage and performs a predetermined operation. Thus, it can be used as the load device 3.
- the distribution line 4 is a power supply line for supplying a power supply voltage to the load device 3.
- the distribution line 4 includes a distribution line that connects the secondary side of the three-phase transformer 1 and the inverter device 2, and a distribution line that connects the inverter device 2 and the load device 3.
- the electric circuit A has a predetermined protective conductor.
- the protective conductor is a conductor provided for safety purposes, for example, for protection against electric shock, and refers to a conductor used in various forms of grounding.
- this protective conductor for example, conductors used for B-type grounding and D-type grounding (grounding wire gcb, grounding wire gcd, grounding electrode gpb, grounding electrode gpd), used for grounding each system of IT, TT, and TN Conductors to be used, conductors used for non-grounding (impedance grounding for medical protective grounding, server centers, etc.), grounding terminals gt provided in the load device 3, power lines serving as the distribution lines 4, and the like.
- E phase These protective conductors are referred to as E phase.
- a ground wire gcd connecting the ground terminal gt of the motor 3a and the ground electrode gpd can be given as an example of the E phase.
- the leakage current calculation apparatus 10 is an apparatus that extracts and measures a component caused by a ground insulation resistance value in the electric circuit A out of the leakage current flowing in the electric circuit A.
- the leakage current calculation device 10 includes a zero-phase current transformer (ZCT) 11, a voltage measurement unit 12, a signal processing unit 13, a calculation unit 14, and a display unit 15.
- ZCT zero-phase current transformer
- the zero-phase current transformer (ZCT) 11 operates as a current measuring unit, and measures a leakage current flowing through the electric circuit A as a zero-phase current I 0 .
- the zero-phase current I 0 includes a leakage current I 0 r that is a component resulting from the resistance value of the ground insulation resistance (Ru, Rv, Rw) of each phase in the load device 3 and a ground capacitance (Cu , Cv, Cw) and the leakage current I 0 c, which is a component resulting from the combination.
- a zero-phase current transformer 11 is shown in a one-dot chain line indicating a panel 5 such as a control panel.
- the zero-phase current I 0 flowing through the distribution line 4 is measured by, for example, sandwiching the distribution line 4 disposed inside the panel 5 between the clamps of the zero-phase current transformer 11. It is. However, when the zero-phase current I 0 can be measured outside the panel 5, for example, the distribution line 4 connected to the secondary side of the three-phase transformer 1 and the distribution line 4 connected to the power supply terminal of the motor 3a. Alternatively, a zero-phase current can be obtained by sandwiching the clamp portion of the zero-phase current transformer 11 with respect to a ground wire gcb or the like that connects the S-phase on the secondary side of the three-phase transformer 1 and the B-type grounded grounding electrode gpb. If it is possible to measure I 0 , these methods can also be used.
- the voltage measuring means 12 is used for each phase-E, which is a voltage between each of the three phases (R phase, S phase, T phase) on the secondary side (output side) of the three phase transformer 1 and the E phase. Measure the interphase voltage.
- the voltage measurement unit 12 includes a voltage acquisition unit 121 and a voltage signal processing unit 122.
- the voltage acquisition unit 121 is a component that is electrically connected to each of the R phase, the S phase, the T phase, and the E phase to acquire the voltage between each phase and the E phase.
- Four voltage acquisition units 121 are connected in the leakage current calculation apparatus 10. Assuming that the four voltage acquisition units 121 are the voltage acquisition units 121a, 121b, 121c, and 121d, the voltage acquisition unit 121a, which is one of these four, is connected to the R phase and is the other one.
- the voltage acquisition unit 121b is connected to the S phase, the other voltage acquisition unit 121c is connected to the T phase, and the remaining voltage acquisition unit 121d is connected to the E phase.
- FIG. 1 a connection portion between the three voltage acquisition units 121 a to 121 c and the distribution line 4 is shown in a dashed line indicating the panel 5.
- connection by this method can be performed.
- the connection part of the voltage acquisition part 121d and the grounding wire gcd is shown in the dashed-dotted line which shows the board 5.
- the connection can be performed by this method.
- the voltage signal processing unit 122 inputs the voltage of each phase through four voltage acquisition units 121a to 121d connected to each of the R phase, S phase, T phase, and E phase, and based on the voltage of each phase. Measure the voltage between each phase and E phase.
- the voltage of each phase includes an R-phase voltage V R , an S-phase voltage V S , a T-phase voltage V T, and an E-phase voltage V E.
- phase -E interphase voltage, S phase -E phase is the voltage between the R-phase -E interphase voltage
- V ER is the voltage between the R-phase and the E phase
- S phase and the E phase There is a voltage V ES and a T phase-E phase voltage V ET which is a voltage between the T phase and the E phase.
- the voltage signal processing unit 122 may be a voltage capturing device that measures the voltage between each phase and the E phase based on the voltage of each phase. Voltage capture device inputs the R-phase voltage V R and E-phase voltage V E, and outputs the difference between these voltages V R and a voltage V E as R phase -E interphase voltage V ER. Further, the voltage take-in device receives the S-phase voltage V S and the E-phase voltage V E and outputs the difference between the voltage V S and the voltage V E as the S-phase-E phase voltage V ES . Further, the voltage capturing device receives the T-phase voltage V T and the E-phase voltage V E and outputs the difference between the voltage V T and the voltage V E as the T-phase-E phase voltage V ET . In addition, the voltage signal processing unit 122 can have a function of removing noise (harmonic components) from the voltages input through the voltage acquisition units 121a to 121d.
- the voltage acquisition device which is the voltage signal processing unit 122 may have a circuit configuration using analog amplifiers AM1 to AM3, for example, as shown in FIG.
- the circuit configuration of the analog amplifiers AM1 to AM3 illustrated in FIG. 2 is an example of the circuit configuration of the voltage signal processing unit 122. Any circuit using an analog amplifier other than an analog amplifier and capable of acquiring the phase-E phase voltage can be used as the voltage signal processing unit 122.
- the signal processing unit 13 includes a voltage signal processing unit 122 (described above), a voltage value calculation unit 131, and a current signal processing unit 132.
- the voltage value calculation unit 131 operates as a voltage value calculation unit. When receiving the voltage between each phase and the E phase from the voltage signal processing unit 122, the voltage value calculation unit 131 synthesizes the voltage between each phase and the E phase. For this voltage value calculation unit 131, an adder that synthesizes the voltages between the respective phases and the E phases can be used. The adder inputs R-phase-E phase voltage VER , S-phase-E phase voltage V ES, and T-phase-E phase voltage V ET, which are voltages between each phase and E phase, and synthesizes them. Outputs the voltage VERST .
- the operation of this adder will be described using vectors.
- the R-phase to E-phase voltage V ER , the S-phase to E-phase voltage V ES , and the T-phase to E-phase voltage V ET which are the voltages between the phases and E phases, are represented as shown in FIG.
- the dotted line shown in FIG. 3, as for the same path A if the line voltage V TR of the T-phase and R-phase, and line voltage V RS of the R-phase and S-phase, S-phase and T when measuring the line voltage V ST between the phase, these line voltages V TR, V RS, which indicates where the vector appears in V ST.
- the T phase-E phase voltage V ET and the R phase-E phase voltage V ER are synthesized.
- the voltage obtained by this synthesis is denoted as VERT and shown in FIG.
- the combined voltage V ERT and the S phase-E phase voltage V ES are combined.
- the voltage obtained by this synthesis is denoted as VERST and is shown in FIG.
- This combined voltage V ERST is a combined voltage of each phase-E phase voltage, that is, a combined voltage of the R phase-E phase voltage VER , the S phase-E phase voltage V ES, and the T phase-E phase voltage V ET It has become.
- the voltage value calculation unit 131 sends the combined voltage VERST to the current value calculation unit 141 of the calculation unit 14.
- the adding device that is the voltage value calculation unit 131 may have a circuit configuration using an analog amplifier AM4, for example, as shown in FIG.
- the circuit configuration of the analog amplifier AM4 illustrated in FIG. 2 is an example of the circuit configuration of the voltage value calculation unit 131. If the circuit uses something other than an analog amplifier and can synthesize a voltage between each phase and the E phase, or a device capable of synthesizing the voltage between each phase and the E phase, the voltage value calculation unit 131 may be used. Can be used.
- the direction of the vector of the composite voltage VERST is the same as the phase of the leakage current I 0 r which is a component due to the ground insulation resistance value of the load device 3 in the leakage current I 0 flowing in the electric circuit A (FIG. 6).
- This is a voltage obtained by synthesizing each phase-E phase voltage V ER , V ES , V ET with the combined voltage V ERST , and each phase-E phase voltage V ER , V ES , V ET is class D ground and class B This is because the voltage is generated in the ground insulation resistance (Ru, Rv, Rw) of the load device 3 excluding the potential difference caused by the ground resistance.
- the direction 90 ° out of phase with respect to the vector direction of the composite voltage VERST is a leakage current I that is a component due to the ground capacitance of the load device 3 in the leakage current I 0 flowing through the electric circuit A. 0 c same as made with the phase (see FIG. 6).
- the current signal processing unit 132 operates as a current measurement unit, inputs the current output from the zero-phase current transformer 11 as the zero-phase current I 0 , and sends it to the current value calculation unit 141 of the calculation unit 14.
- the current signal processor 132 may comprise the like against zero-phase current I 0 which is input from the zero-phase current transformer 11, the ability to remove the function and noise amplification (harmonic component).
- the calculation unit 14 is configured by a computer including an interface such as a central processing unit (CPU), ROM, RAM, and I / O, for example, and includes a current value calculation unit 141 and a resistance value calculation unit 142. Yes.
- CPU central processing unit
- ROM read-only memory
- RAM random access memory
- I / O resistance value calculation unit
- the current value calculation unit 141 operates as a current value calculation unit, inputs the combined voltage VERST sent from the voltage value calculation unit 131, and receives the zero-phase current I 0 sent from the current signal processing unit 132. Based on these input voltages V ERST and zero-phase current I 0 , the leakage current I 0 r flowing due to the ground insulation resistance (Ru, Rv, Rw) is extracted and calculated.
- I 0 is an effective value of the zero-phase current I 0 input from the current signal processing unit 132.
- ⁇ is the phase difference between the combined voltage V ERST and the zero-phase current I 0 .
- each phase -E interphase voltage V ER, V ES, when measuring the V ET, these phases -E interphase voltage V ER, V ES, composite voltage was synthesized V ET V ERST is calculated.
- This combined voltage VERST is represented by a vector as shown in FIG.
- the combined voltage V ERS is in phase with the leakage current I 0 r.
- the phase difference between the combined voltage V ERST and the zero-phase current I 0 is ⁇ in Equation 1. For this reason, the leakage current I 0 r can be calculated by using Equation 1.
- ⁇ is a phase difference between the combined voltage V ERST and the zero-phase current I 0
- the combined voltage V ERST is a combined voltage of each phase-E phase voltage
- each phase-E phase voltage V ER , V ES , and V ET do not include a potential difference caused by the ground resistance of the protective conductor, but are measured as voltages caused by ground insulation resistance (Ru, Rv, Rw).
- the leakage current calculation apparatus 10 of this embodiment can calculate ⁇ accurately and can calculate the leakage current I 0 r with high accuracy.
- the current value calculation unit 141 calculates the leakage current I 0 r that is a component caused by the ground insulation resistance value obtained by removing the ground capacitance component I 0 c from the leakage current I 0 based on the combined voltage V ERS. It can be extracted and calculated.
- the leakage current I 0 r calculated here is the leakage current flowing due to the ground insulation resistance Ru, the leakage current flowing due to the ground insulation resistance Rv, and the leakage flowing due to the ground insulation resistance Rw. It is a combination of current and current.
- the current value calculation unit 141 stores various data (for example, zero-phase current I 0 , combined voltage V ERS , leakage current I 0 r, etc.) in a storage unit (not shown) such as a RAM. In addition, the current value calculation unit 141 sends the data to the resistance value calculation unit 142. Furthermore, the current value calculation unit 141 can send the data to the display unit 15.
- a storage unit not shown
- the current value calculation unit 141 sends the data to the resistance value calculation unit 142.
- the current value calculation unit 141 can send the data to the display unit 15.
- the resistance value calculation unit 142 calculates a combined resistance value R0 of the ground insulation resistance (Ru, Rv, Rw) in the load device 3 using the combined voltage V ERST and the leakage current I 0 r.
- the combined resistance value R0 can be calculated using the following equation 2.
- Composite resistance value R0 Composite voltage V RST / Leakage current I 0 r (Equation 2)
- the resistance value calculation unit 142 stores various data (for example, the calculated combined resistance value R0 of the ground insulation resistance) in a storage unit (not shown). In addition, the resistance value calculation unit 142 sends the data to the display unit 15.
- the display unit 15 inputs various data sent from the calculation unit 14 and displays predetermined data on the screen.
- the display unit 15 displays designated data on the screen when an input operation unit (not shown) configured by physical keys, software keys, and the like is operated by the user.
- the various data displayed by the display unit 15 includes data sent from the resistance value calculation unit 142 and the current value calculation unit 141 and data extracted from the storage unit.
- a liquid crystal display or the like can be used for the display unit 15.
- FIG. 7 is a circuit diagram showing the configurations of the leakage current measuring apparatus 100 and the electric circuit A that measure the ground voltages of the R phase, the S phase, and the T phase.
- FIG. 8 is an equivalent circuit of a path through which the leakage current I 0 flows in the electric circuit A shown in FIG.
- FIG. 9 is a diagram illustrating a path through which the leakage current I 0 flows in the electric circuit A illustrated in FIG. 7, and is a parallel circuit of the ground insulation resistance Ru and the ground capacitance Cu of the load device 3, and the ground insulation resistance.
- each phase-E phase voltage is added to each end of the parallel circuit of Rv and ground electrostatic capacitance Cv, and the parallel circuit of ground insulation resistance Rw and ground electrostatic capacitance Cw.
- 7 to 9 show a circuit configuration of the electric circuit A to which the inverter device 2 is not connected or an equivalent circuit of the electric circuit A in order to make the explanation of (1) to (3) simple and easy to understand. Yes. A case where the ground voltage, the line voltage, and the phase-E phase voltage are measured for the electric circuit A shown in FIGS. 7 to 9 will be described separately in (1) to (3) below.
- the measured voltage is the R-phase voltage V RG with respect to the ground (G: Ground), and the ground S-phase voltage V SG for (G) and T-phase voltage V TG for ground (G).
- this equivalent circuit includes a parallel circuit (hereinafter referred to as “the load device 3 of the load device 3) of the ground insulation resistance (Ru, Rv, Rw) of the load device 3 and the ground capacitance (Cu, Cv, Cw).
- the ground that component circuit 3b ") the ground resistance R D of the D type grounding, a series circuit of a ground resistance R B of the B type grounding, can be represented as a circuit connected in series.
- the point x is between the secondary side of the three-phase transformer 1 and the ground component circuit 3b of the load device 3, and the ground component circuit 3b of the load device 3 and the ground of class D grounding are used.
- a point y between the resistor RD and a point z between the ground resistance of the D-type ground and the ground resistance of the B-type ground is defined as a point z.
- the ground voltages V RG , V SG , and V TG of the R, S, and T phases are voltages between the point x and the point z.
- the ground voltage V RG, V SG, V TG since the voltage level is between those points x and the point z, also includes potential VeD occurring in ground resistance R D. That is, the ground voltages V RG , V SG , and V TG are more at the ground resistance R D than the voltages (voltages between the points x and y) applied to both ends of the ground insulation resistance (Ru, Rv, Rw). It is increased by the generated potential difference VeD.
- the line voltage is the voltage V RT between the R phase and the T phase on the secondary side of the three-phase transformer 1, and T
- the leakage current I 0 r is a leakage current that flows due to the ground insulation resistance (Ru, Rv, Rw).
- the leakage current I 0 r is also flows to the ground resistance R D and the ground resistance R B, to these grounding resistance R D and the ground resistance R B, the leakage current I 0 c also flows. Therefore, the leakage current I 0 r cannot be accurately calculated only by measuring the line voltages V RT , V TS , V SR .
- the voltages V ER , V ES , and V ET between each phase and the E phase are voltages (point x and point) applied to both ends of the ground component circuit 3b as shown in FIG. y). That is, the voltages V ER , V ES , and V ET between the respective phases and the E phases are, as shown in FIG. 9, the ground insulation resistance (Ru, Rv, Rw) and the ground capacitance (R, S, T) in each phase. Cu, Cv, Cw) are applied to both ends of the parallel circuit.
- the voltage V ERST that combines the phase-E phase voltages V ER , V ES , and V ET is a leakage current I 0 that combines the leakage currents flowing through the ground insulation resistances (Ru, Rv, Rw) of the load device 3. It is in phase with r.
- the current whose phase is advanced by 90 ° with respect to the combined voltage V ERST is in phase with the leakage current I 0 c obtained by combining the leakage currents flowing through the ground capacitances (Cu, Cv, Cw) (see FIG. 6). ).
- the synthesized voltage VERST is a predetermined voltage obtained by extracting the voltage component applied to the ground insulation resistance (Ru, Rv, Rw) of the load device 3 except for the potential difference caused by the ground resistances of the class D ground and the class B ground. It is a voltage value. Therefore, the leakage current I 0 r can be accurately calculated by using the voltage VERST obtained by combining the phase-E phase voltages V ER , V ES , and V ET .
- this conventional technique uses the measured value as a ground voltage.
- the leakage current I 0 r was calculated on the assumption that the voltage was a line voltage. For this reason, even in such a conventional technique, the leakage current I 0 r cannot be accurately calculated.
- the voltage V ERST obtained by combining the E phase voltages V ER , V ES , and V ET is the ground insulation resistance (Ru, Rv, Rw) of the load device 3 except for the potential difference caused by the ground resistances of the class D ground and the class B ground. )
- the leakage current I 0 r can be accurately calculated by using the composite voltage V ERS .
- FIG. 10 is a flowchart showing each step of the leakage current calculation method executed by the leakage current calculation apparatus 10.
- the distribution line 4 or the ground line gcb is sandwiched between the clamp portions of the zero-phase current transformer 11.
- the voltage acquisition unit 121 of the voltage measuring unit 12 is electrically connected to the distribution line 4 (R phase, S phase, T phase) of the electric circuit A and the ground wire gcd (E phase).
- the voltage acquisition unit 121a is connected to the R phase
- the voltage acquisition unit 121b is connected to the S phase
- the voltage acquisition unit 121c is connected to the T phase
- the voltage acquisition unit 121d is connected to the E phase.
- the zero-phase current transformer 11 is generated in the magnetic core in the clamp by the magnetic field generated around the distribution line 4 or the ground line gcb based on the zero-phase current I 0 flowing in the electric circuit A (the distribution line 4 or the ground line gcb).
- the induced current is sent to the current signal processing unit 132.
- the current signal processing unit 132 sends the induced current flowing from the zero-phase current transformer 11 to the current value calculation unit 141 of the calculation unit 14 as the zero-phase current I 0 (current measurement step, S10).
- the voltage signal processing unit 122 of the voltage measuring unit 12 inputs the voltages V R , V S , V T , and V E of the R phase, S phase, T phase, and E phase through the voltage acquisition unit 121 and inputs them.
- each phase of the voltage V R which is, V S, V T, based on V E, between the R-phase -E interphase voltage V ER is the voltage between the R-phase and the E phase
- the S phase and the E phase S-E phase voltage V ES which is the voltage between the T phase
- E phase voltage V ET which is the voltage between the T phase and the E phase
- the voltage value calculation unit 131 synthesizes the voltage between each phase and the E phase (voltage value calculation step, S12).
- the voltage value calculation unit 131 sends the combined voltage VERST to the current value calculation unit 141.
- the current value calculation unit 141 is caused by the ground insulation resistance value based on the zero-phase current I 0 sent from the current signal processing unit 132 and the composite voltage V ERS sent from the voltage value calculation unit 131.
- the flowing leakage current I 0 r is calculated (current value calculating step, S13).
- the resistance value calculation unit 142 calculates the resistance value R0 of the ground insulation resistance in the load device 3 based on the leakage current I 0 r and the combined voltage V ERS (S14). These measured or calculated zero-phase current I 0 , each phase-E phase voltage, combined voltage V ERS , leakage current I 0 r, resistance value R 0 of the ground insulation resistance, etc. are stored in a storage unit (not shown). The Further, the zero-phase current I 0 and the like can be displayed on the display unit 15.
- the predetermined voltage obtained by extracting the voltage component applied to the ground insulation resistance, excluding the potential difference caused by the ground resistance of the protective conductor. The value is calculated based on the voltage between each phase and the E phase.
- the leakage current I 0 is a component derived from the ground insulation resistance value excluding the ground capacitance component I 0 c. Since a certain leakage current I 0 r is extracted and calculated, this leakage current I 0 r can be calculated with high accuracy. Further, even when the leakage current I 0 c flowing due to the ground capacitance in the electric circuit laid in a large factory or the like is large, the leakage current I 0 r can be calculated with high accuracy.
- the leakage current calculation device and the leakage current calculation method of the present invention have been described above, but the leakage current calculation device and the leakage current calculation method according to the present invention are not limited to the above-described embodiments, It goes without saying that various modifications can be made within the scope of the present invention.
- the distribution method of the electric circuit is a three-phase three-wire system, but it is not limited to a three-phase three-wire system, but a three-phase four-wire system, a single-phase three-wire system, or a single-phase two-wire system. May be.
- the voltage between each phase and the E phase is the voltage between the R phase and the E phase, the voltage between the T phase and the E phase, and the S phase and the E phase.
- the voltage between the phases can be a voltage between the N phase and the E phase.
- the voltage between each phase and the E phase is the voltage between the L1 phase and the E phase, the voltage between the L2 phase and the E phase, and the N phase and the E phase. It can be the voltage between the phases.
- the voltage between each phase and the E phase can be a voltage between the a phase and the E phase, and a voltage between the b phase and the E phase.
- connection system of the secondary side winding of a three-phase transformer is set as the delta connection, a V connection or a star connection may be used.
- the primary side connection method of the three-phase transformer is a star connection, but a delta connection may be used.
- the electric circuit includes a power cable connected to the load device in addition to the three-phase transformer, the load device, and the distribution line.
- the electric circuit is configured to include a three-phase transformer, an inverter device, and a load device.
- the present invention is not limited to this configuration, and as illustrated in FIG. It can also be set as the structure which is not provided.
- the load device performs a predetermined operation by inputting the AC voltage output from the secondary side of the three-phase transformer as a power supply voltage.
- the leakage current calculation apparatus of the present invention can calculate the combined voltage V ERS with the same content as described in the above-described embodiment. .
- the leakage current calculation apparatus according to the present invention calculates the leakage current I 0 r as follows.
- Equation 3 the following formula 3 is known as a known formula used when calculating the leakage current I 0 r.
- I 0 r I 0 ⁇ sin ⁇ / cos 30 ° (Expression 3)
- This Formula 3 is a well-known formula used when calculating the leakage current I 0 r in the electric circuit (electric circuit A as shown in FIG. 11) to which the inverter device is not connected.
- I 0 is an effective value of the zero-phase current I 0 .
- Equation 3 is based on the line voltage VTR between the T phase and the R phase. Therefore, the ⁇ of Equation 3, the phase difference between the combined voltage V TR and the zero-phase current I 0.
- the leakage current calculation apparatus of the present invention calculates a combined voltage V ERST that combines the phase-E phase voltages V ER , V ES , and V ET .
- the measurement method based on the combined voltage V ERS causes a phase difference of 90 ° with respect to a known measurement method based on the line voltage V TR .
- the reason why the phase difference of 90 ° occurs is as follows. In order to make the explanation simple and easy to understand, here, as a condition, the ground resistance is 0 ⁇ , and the potential difference between the E phase and the S phase is 0V.
- the magnitude of the leakage current I 0 r-R flowing through the ground insulation resistance Ru and the ground insulation resistance Rw Assume that the magnitudes of the flowing leakage currents I 0 r ⁇ T are the same. Under such conditions, the vector of the leakage current I 0 r has a phase difference of 0 ° with respect to the composite voltage V RST when the composite voltage V RST is used as a reference, whereas the line voltage V When TR is used as a reference, the phase difference is 90 ° with respect to the line voltage VTR .
- the measurement method based on the combined voltage V ERS produces a phase difference of 90 ° with respect to the known measurement method based on the line voltage V TR . Therefore, by using the following Expression 4 in which the phase difference is added to ⁇ in Expression 3, it is possible to calculate the leakage current I 0 r when the combined voltage V ERS is used as a reference.
- I 0 r I 0 ⁇ sin ( ⁇ + 90 °) / cos30 ° (Formula 4)
- ⁇ is a phase difference between the combined voltage V ERST and the zero-phase current I 0 .
- the composite voltage V ERST is a composite voltage of each phase-E phase voltage, and each phase-E phase voltage V ER , V ES , V ET does not include the potential difference caused by the ground resistance of the protective conductor and It is measured as a voltage generated by resistance (Ru, Rv, Rw). For this reason, the leakage current calculation apparatus of the present invention can calculate ⁇ with high accuracy and can calculate the leakage current I 0 r with high accuracy even for an electric circuit to which no inverter device is connected.
- the present invention can be widely used in an apparatus for measuring a leakage current of an electric circuit.
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Abstract
Description
例えば、特許文献1に記載の漏洩電流測定装置(以下、「装置1」という)は、二次側巻線がΔ(デルタ)型に結線された三相変圧器の当該二次側におけるR相とT相との線間電圧VRT(あるいは、T相とS相との線間電圧VTS、又は、S相とR相との線間電圧VSR)を測定し、この三相変圧器の二次側と負荷装置とを接続する配電線に流れる零相電流I0を測定し、線間電圧VRT(あるいは、VTS、又は、VSR)を基準電圧としたときの当該基準電圧と零相電流I0との位相差を算出し、零相電流I0を、基準電圧と同相の有効成分と、基準電圧に対して90°の位相差を有する無効成分とに分けることにより、有効成分を漏洩電流I0rとして算出するものである。
この装置1は、負荷装置(例えばモーター)が運転状態となっており、電路が活線状態となっているときでも、漏洩電流I0rを算出できるようになっている。
そして、こうした測定装置では、漏洩電流I0rをより正確に測定することが求められる。
ただし、実際の測定装置では、種々の要因により、測定した漏洩電流I0rに誤差が生じることがある。
そうした誤差が生じる要因をできる限り排除して、漏洩電流I0rを精度よく測定することが、当該測定装置を設計する上での課題となっていた。
また、大規模な工場などに布設された電路における対地静電容量に起因して流れる漏洩電流I0cが大きい場合でも、漏洩電流I0rを精度良く算出することができる。
なお、ここでは、所定の負荷装置に交流電源電圧を供給する電路の構成について先に説明し、その後に、この電路を対象として漏洩電流を測定する漏洩電流算出装置の構成について説明する。
図1に示すように、電路Aは、配電方式が三相3線式である。
この電路Aは、三相変圧器1と、インバーター機器2と、負荷装置3と、配電線4と、を備えている。
この三相変圧器1の二次側の各相であるR相、S相、T相のうちの一つの相(図1においては、S相)には、B種接地が施されている。
B種接地は、接地抵抗値が電気設備の技術基準の解釈に定められているB種接地工事の接地抵抗値と同値又はこれ以下の値となるように大地に接続された接地である。
このB種接地の接地抵抗値をRBとする。また、三相変圧器1の二次側の各相であるR相、S相、T相のうちB種接地が施されている相(図1においては、S相)を接地相とする。さらに、このB種接地を施すために大地に埋設等される電極を接地極gpbとする。そして、接地極gpbと接地相(S相)とを接続する配線を接地線gcbとする。
なお、インバーター機器2の入力側には、三相変圧器1のR相、S相、T相が接続されている。また、インバーター機器2の出力側には、モーター3aの電源入力端子U、V、Wが接続されている。
モーター3aは、インバーター機器2から出力された交流電圧を電源電圧として入力し、交流電流を各巻線に流して、回転軸を回転させる。
モーター3aのハウジングには、感電を防止するために、D種接地が施されている。
D種接地は、接地抵抗値が電気設備の技術基準の解釈に定められているD種接地工事の接地抵抗値と同値又はこれ以下の値となるように大地に接続された接地である。
このD種接地の接地抵抗値をRDとする。また、モーター3aのハウジングには、D種接地を施すための端子である接地端子gtが設けられている。さらに、このD種接地を施すために大地に埋設等される電極を接地極gpdとする。そして、モーター3aの接地端子gtと接地極gpdとの間を接続する配線を接地線gcdとする。このように、モーター3aの接地端子gtと地中に埋設された接地極gpdとの間を接地線gcdで接続することにより、モーター3aのハウジングにD種接地を施すことができる。
保護導体とは、安全目的、例えば、感電保護のために設ける導体であって、種々の接地の形態に使用される導体をいう。
この保護導体には、例えば、B種接地やD種接地で使用される導体(接地線gcb、接地線gcd、接地極gpb、接地極gpd)、IT、TT、TNの各系統の接地に使用される導体、非接地式(医用保護接地やサーバーセンター等のインピーダンス接地)に使用される導体、負荷装置3に設けられた接地端子gt、配電線4である電源線などが含まれる。
具体的に、図1に示す電路Aにおいては、モーター3aの接地端子gtと接地極gpdとを接続している接地線gcdを、E相の例として挙げることができる。
本実施形態に係る漏洩電流算出装置10は、電路Aに流れる漏洩電流のうち、電路A内の対地絶縁抵抗値に起因する成分を抽出して測定する装置である。
この漏洩電流算出装置10は、図1に示すように、零相変流器(ZCT)11、電圧測定手段12、信号処理部13、演算部14、及び表示部15を備えている。
この零相電流I0は、負荷装置3における各相の対地絶縁抵抗(Ru,Rv,Rw)の抵抗値に起因する成分である漏洩電流I0rと、各相の対地静電容量(Cu,Cv,Cw)に起因する成分である漏洩電流I0cとを合成したものである。
なお、図1においては、制御盤などの盤5を示す一点鎖線の中に零相変流器11を示している。これは、盤5の内部に配設された配電線4を、零相変流器11のクランプ部で挟み込むなどして、配電線4に流れる零相電流I0を測定することを想定したものである。ただし、盤5の外部において零相電流I0の測定が可能な場合、例えば、三相変圧器1の二次側に接続された配電線4、モーター3aの電源端子に接続された配電線4、あるいは、三相変圧器1の二次側のS相とB種接地の接地極gpbとを接続する接地線gcbなどに対して、零相変流器11のクランプ部を挟み込んで零相電流I0を測定することが可能な場合は、これらの方法を用いることもできる。
この電圧測定手段12は、電圧取得部121と、電圧信号処理部122とを有している。
電圧取得部121は、漏洩電流算出装置10において四本接続されている。四本の電圧取得部121をそれぞれ電圧取得部121a、121b、121c、121dとすると、これら四本のうちの一本である電圧取得部121aは、R相に接続され、他の一本である電圧取得部121bは、S相に接続され、他の一本である電圧取得部121cは、T相に接続され、残りの一本である電圧取得部121dは、E相に接続される。
さらに、図1においては、盤5を示す一点鎖線の中に、電圧取得部121dと接地線gcdとの接続部分を示している。ただし、盤5の外部において電圧取得部121dと接地線gcdとを接続することが可能な場合には、この方法での接続を行うことができる。
各相の電圧には、R相の電圧VRと、S相の電圧VSと、T相の電圧VTと、E相の電圧VEがある。
また、各相-E相間電圧には、R相とE相との間の電圧であるR相-E相間電圧VERと、S相とE相との間の電圧であるS相-E相間電圧VESと、T相とE相との間の電圧であるT相-E相間電圧VETがある。
電圧取込装置は、R相電圧VRとE相電圧VEとを入力し、これら電圧VRと電圧VEとの差をR相-E相間電圧VERとして出力する。また、電圧取込装置は、S相電圧VSとE相電圧VEとを入力し、これら電圧VSと電圧VEとの差をS相-E相間電圧VESとして出力する。さらに、電圧取込装置は、T相電圧VTとE相電圧VEとを入力し、これら電圧VTと電圧VEとの差をT相-E相間電圧VETとして出力する。
また、電圧信号処理部122は、電圧取得部121a~121dを通して入力した電圧に対してノイズ(高調波成分)を除去する機能などを備えることができる。
ただし、図2に示したアナログアンプAM1~AM3の回路構成は、電圧信号処理部122の回路構成の一例である。アナログアンプ以外のものを用いた回路であって、各相-E相間電圧を取得可能な回路であれば、電圧信号処理部122として用いることができる。
この電圧値算出部131には、各相-E相間電圧を合成する加算装置を用いることができる。
加算装置は、各相-E相間電圧であるR相-E相間電圧VERとS相-E相間電圧VESとT相-E相間電圧VETとを入力し、これらを合成し、この合成電圧VERSTを出力する。
各相-E相間電圧である、R相-E相間電圧VER、S相-E相間電圧VES、T相-E相間電圧VETは、ベクトルで表すと、図3に示すようになる。
なお、図3に示す点線は、同じ電路Aを対象として、仮に、T相とR相との線間電圧VTRと、R相とS相との線間電圧VRSと、S相とT相との線間電圧VSTとを測定したときに、これら線間電圧VTR、VRS、VSTのベクトルが表れる位置を示している。
次いで、合成電圧VERTとS相-E相間電圧VESとを合成する。この合成により得られた電圧をVERSTとし、図5に示す。
この合成電圧VERSTは、各相-E相間電圧の合成電圧、すなわち、R相-E相間電圧VERとS相-E相間電圧VESとT相-E相間電圧VETとの合成電圧となっている。
電圧値算出部131は、合成電圧VERSTを、演算部14の電流値算出部141へ送る。
また、電圧値算出部131である加算装置は、例えば、図2に示すように、アナログアンプAM4を用いた回路構成とすることができる。
ただし、図2に示したアナログアンプAM4の回路構成は、電圧値算出部131の回路構成の一例である。アナログアンプ以外のものを用いた回路であって、各相-E相間電圧の合成が可能な回路、あるいは、各相-E相間電圧の合成が可能な装置であれば、電圧値算出部131として用いることができる。
これは、合成電圧VERSTが各相-E相間電圧VER、VES、VETを合成した電圧であり、各相-E相間電圧VER、VES、VETがD種接地及びB種接地の接地抵抗によって生じる電位差を除いた、負荷装置3の対地絶縁抵抗(Ru、Rv、Rw)に生じる電圧だからである。
そして、合成電圧VERSTのベクトルの向きに対して90°位相がずれた向きは、電路Aに流れる漏洩電流I0のうち、負荷装置3の対地静電容量に起因する成分である漏洩電流I0cの位相と同じとなる(図6参照)。
また、電流信号処理部132は、零相変流器11から入力した零相電流I0に対して、増幅する機能やノイズ(高調波成分)を除去する機能などを備えることができる。
I0r=I0・cosθ ・・・(式1)
この式1において、I0は、電流信号処理部132から入力した零相電流I0の実効値である。また、θは、合成電圧VERSTと零相電流I0との位相差である。
本実施形態の漏洩電流算出装置10は、各相-E相間電圧VER、VES、VETを測定すると、これら各相-E相間電圧VER、VES、VETを合成した合成電圧VERSTを算出する。この合成電圧VERSTをベクトルで表すと、図6に示すようになる。
図6に示すように、合成電圧VERSTは、漏洩電流I0rと同相である。そして、この合成電圧VERSTと零相電流I0との位相差が、式1のθとなっている。
このため、式1を使用することで、漏洩電流I0rを算出することができる。
なお、ここで算出される漏洩電流I0rは、対地絶縁抵抗Ruに起因して流れる漏洩電流と、対地絶縁抵抗Rvに起因して流れる漏洩電流と、対地絶縁抵抗Rwに起因して流れる漏洩電流とを合成したものである。
合成抵抗値R0は、次の式2を用いて算出することができる。
合成抵抗値R0=合成電圧VERST÷漏洩電流I0r ・・・(式2)
次に、各相-E相間電圧を測定する理由について説明する。
比較のため、ここでは、次の測定方法について、順に説明する。
(1)R相、S相、T相の対地電圧を測定する場合
(2)R相、S相、T相の線間電圧を測定する場合
(3)各相-E相間電圧を測定する場合
この場合、測定される電圧は、図7に示すように、大地(G:Ground)に対するR相の電圧VRGと、大地(G)に対するS相の電圧VSGと、大地(G)に対するT相の電圧VTGである。
また、図8に示す等価回路において、三相変圧器1の二次側と負荷装置3の対地成分回路3bとの間を点xとし、負荷装置3の対地成分回路3bとD種接地の接地抵抗RDとの間を点yとし、D種接地の接地抵抗とB種接地の接地抵抗との間を点zとする。
ところが、この対地電圧VRG、VSG、VTGは、それら点xと点zとの間の電圧であるので、接地抵抗RDにおいて発生する電位差VeDも含まれる。つまり、対地電圧VRG、VSG、VTGは、対地絶縁抵抗(Ru、Rv、Rw)の両端にかかる電圧(点xと点yとの間の電圧)よりも、さらに接地抵抗RDにおいて発生する電位差VeDの分だけ多くなっている。
また、その接地抵抗RDには、漏洩電流I0rだけでなく漏洩電流I0cも流れる。
このため、この対地電圧VRG、VSG、VTGを用いても、対地絶縁抵抗値に起因して流れる漏洩電流I0rを精度よく算出することができない。
線間電圧は、三相変圧器1の二次側における、R相とT相との間の電圧VRTと、T相とS相との間の電圧VTSと、S相とR相との間の電圧VSRである。
この線間電圧は、図8に示す等価回路においては、対地成分回路3bだけでなく、接地抵抗RDや接地抵抗RBにも加わる電圧となる(図8において線間電圧は図示せず)。
これに対し、漏洩電流I0rは、対地絶縁抵抗(Ru、Rv、Rw)に起因して流れる漏洩電流である。そして、この漏洩電流I0rは、接地抵抗RDや接地抵抗RBにも流れるが、これら接地抵抗RDや接地抵抗RBには、漏洩電流I0cも流れる。
よって、線間電圧VRT、VTS、VSRを測定しただけでは、漏洩電流I0rを精度よく算出することはできない。
各相-E相間電圧VER、VES、VETは、図8に示すように、対地成分回路3bの両端にかかる電圧(点xと点yとの間の電圧)となる。つまり、各相-E相間電圧VER、VES、VETは、図9に示すように、R,S,T各相における、対地絶縁抵抗(Ru、Rv、Rw)と対地静電容量(Cu、Cv、Cw)との並列回路の両端にかかる電圧となっている。
さらに、各相-E相間電圧VER、VES、VETを合成した電圧VERSTは、負荷装置3の対地絶縁抵抗(Ru、Rv、Rw)にそれぞれ流れる漏洩電流を合成した漏洩電流I0rと同相となる。しかも、合成電圧VERSTに対して90°位相が進んだ電流は、対地静電容量(Cu、Cv、Cw)にそれぞれ流れる漏洩電流を合成した漏洩電流I0cと同相となる(図6参照)。
よって、各相-E相間電圧VER、VES、VETを合成した電圧VERSTを用いることにより、漏洩電流I0rを精度よく算出することができる。
次に、本実施形態における漏洩電流算出方法について、図1及び図10を参照して説明する。
図10は、漏洩電流算出装置10が実行する漏洩電流算出方法の各工程を示すフローチャートである。
また、電圧測定手段12の電圧取得部121が、電路Aの配電線4(R相、S相、T相)と接地線gcd(E相)に電気的に接続される。具体的には、電圧取得部121aがR相に接続され、電圧取得部121bがS相に接続され、電圧取得部121cがT相に接続され、電圧取得部121dがE相に接続される。
電流信号処理部132は、零相変流器11から流れてきた誘導電流を零相電流I0として、演算部14の電流値算出部141へ送る(電流測定工程、S10)。
電流値算出部141は、電流信号処理部132から送られてきた零相電流I0と電圧値算出部131から送られてきた合成電圧VERSTとにもとづいて、対地絶縁抵抗値に起因して流れる漏洩電流I0rを算出する(電流値算出工程、S13)。
これら測定又は算出された零相電流I0、各相-E相間電圧、合成電圧VERST、漏洩電流I0r、対地絶縁抵抗の抵抗値R0等は、記憶部(図示せず)に記憶される。また、零相電流I0等は、表示部15に表示させることができる。
また、大規模な工場などに布設された電路における対地静電容量に起因して流れる漏洩電流I0cが大きい場合でも、漏洩電流I0rを精度良く算出することができる。
例えば、図1では、電路の配電方式を三相3線式としたが、三相3線式に限るものではなく、三相4線式、単相3線式、単相2線式であってもよい。そして、電路の配電方式が三相4線式である場合、各相-E相間電圧は、R相とE相との間の電圧、T相とE相との間の電圧、S相とE相との間の電圧、N相とE相との間の電圧とすることができる。また、電路の配電方式が単相3線式である場合、各相-E相間電圧は、L1相とE相との間の電圧、L2相とE相との間の電圧、N相とE相との間の電圧とすることができる。さらに、電路の配電方式が単相2線式である場合、各相-E相間電圧は、a相とE相との間の電圧、b相とE相との間の電圧とすることができる。
さらに、図1においては、三相変圧器の一次側の結線方式をスター結線としてあるが、デルタ結線であってもよい。
また、電路には、三相変圧器、負荷装置、配電線の他に、負荷装置につながる電源ケーブルも含まれる。
また、電路の構成が図11に示す構成となっている場合でも、本発明の漏洩電流算出装置は、上述した実施形態において説明した内容と同様の内容で合成電圧VERSTを算出することができる。
ただし、本発明の漏洩電流算出装置は、漏洩電流I0rの算出については、次のように行う。
例えば、漏洩電流I0rを算出するときに使用される公知の式として、次の式3がある。
I0r=I0・sinθ/cos30° ・・・(式3)
この式3は、インバーター機器が接続されていない電路(図11に示すような電路A)において、漏洩電流I0rを算出するときに使用される公知の式である。
この式3において、I0は、零相電流I0の実効値である。
また、式3は、T相とR相との間の線間電圧VTRを基準としている。このため、式3のθは、合成電圧VTRと零相電流I0との位相差である。
このように、90°の位相差が生じる理由は、次の通りである。説明を簡潔かつ理解容易とするために、ここでは、条件として、接地抵抗を0Ωとし、E相とS相との電位差を0Vとする。また、R相の対地絶縁抵抗Ruの抵抗値とT相の対地絶縁抵抗Rwの抵抗値が同じであるとし、対地絶縁抵抗Ruに流れる漏洩電流I0r-Rの大きさと対地絶縁抵抗Rwに流れる漏洩電流I0r-Tの大きさが同じであるとする。このような条件において、漏洩電流I0rのベクトルは、合成電圧VERSTを基準とした場合には、この合成電圧VERSTに対して位相差が0°となるのに対し、線間電圧VTRを基準とした場合には、この線間電圧VTRに対して位相差が90°となる。よって、合成電圧VERSTを基準とした測定方法は、線間電圧VTRを基準とする公知の測定方法に対して90°の位相差が生じることとなる。
そこで、式3のθにその位相差を加えた次の式4を使用することで、合成電圧VERSTを基準としたときの漏洩電流I0rの算出が可能となる。
I0r=I0・sin(θ+90°)/cos30° ・・・(式4)
この式4において、θは、合成電圧VERSTと零相電流I0との位相差である。また、合成電圧VERSTは、各相-E相間電圧の合成電圧であり、各相-E相間電圧VER、VES、VETは、保護導体の接地抵抗によって生じる電位差を含まず、対地絶縁抵抗(Ru、Rv、Rw)によって生じる電圧として測定される。このため、本発明の漏洩電流算出装置は、インバーター機器が接続されていない電路に対しても、θを精度よく算出することができ、漏洩電流I0rを精度よく算出することができる。
11 零相変流器(ZCT、電流測定手段)
12 電圧測定手段
121 電圧取得部
122 電圧信号処理部
13 信号処理部
131 電圧値算出部(電圧値算出手段)
132 電流信号処理部(電流測定手段)
14 演算部
141 電流値算出部(電流値算出手段)
142 抵抗値算出部
15 表示部
A 電路
1 三相変圧器
2 インバーター機器
3 負荷装置
3a モーター
4 配電線
5 盤
Claims (6)
- 所定の保護導体を有する電路に流れる漏洩電流のうち、前記電路内の対地絶縁抵抗値に起因する成分を抽出して測定する漏洩電流算出装置であって、
前記電路に流れる漏洩電流を測定する電流測定手段と、
前記保護導体をE相としたときに、前記電路の電源部の各相のそれぞれと前記E相との間の電圧である各相-E相間電圧を測定する電圧測定手段と、
前記保護導体の接地抵抗によって生じる電位差を除いて、前記対地絶縁抵抗に印加される電圧成分を抽出した所定の電圧値を、前記各相-E相間電圧にもとづいて算出する電圧値算出手段と、
前記所定の電圧値にもとづいて、前記漏洩電流のうち、対地容量成分を除いた、前記対地絶縁抵抗値に起因する成分を抽出する電流値算出手段と、を備えた
ことを特徴とする漏洩電流算出装置。 - 前記電圧値算出手段は、前記各相-E相間電圧を合成した電圧である合成電圧を前記所定の電圧値として算出し、
前記電流値算出手段は、前記合成電圧を用いて、前記漏洩電流のうち、対地容量成分を除いた、前記対地絶縁抵抗値に起因する成分を抽出する
ことを特徴とする請求項1記載の漏洩電流算出装置。 - 前記電圧値算出手段は、前記各相-E相間電圧を合成した電圧である合成電圧を前記所定の電圧値として算出し、
前記電流値算出手段は、
前記漏洩電流のうち前記合成電圧の位相と同じ位相の成分を、前記漏洩電流のうち、対地容量成分を除いた、前記対地絶縁抵抗値に起因する成分として抽出する
ことを特徴とする請求項1又は2記載の漏洩電流算出装置。 - 前記電源部の各相が、R相と、S相と、T相であり、
前記各相-E相間電圧が、前記R相と前記E相との間の電圧であるR相-E相間電圧と、前記S相と前記E相との間の電圧であるS相-E相間電圧と、前記T相と前記E相との間の電圧であるT相-E相間電圧であり、
前記電圧値算出手段が、前記R相-E相間電圧と前記S相-E相間電圧と前記T相-E相間電圧とを合成した電圧を、合成電圧として算出し、
前記電流値算出手段は、前記漏洩電流のうち、対地容量成分を除いた、前記対地絶縁抵抗値に起因する成分を、前記合成電圧にもとづいて抽出する
ことを特徴とする請求項1~3のいずれか一項に記載の漏洩電流算出装置。 - 前記電路は、
前記電源部から出力された交流電圧を所定の電圧に変換して出力するインバーターと、
このインバーターから出力された所定の電圧を入力して動作する負荷装置と、を備えた
ことを特徴とする請求項1~4のいずれか一項に記載の漏洩電流算出装置。 - 所定の保護導体を有する電路に流れる漏洩電流のうち、前記電路内の対地絶縁抵抗値に起因する成分を抽出して測定する漏洩電流算出方法であって、
前記電路に流れる漏洩電流を測定する電流測定工程と、
前記保護導体をE相としたときに、前記電路の電源部の各相のそれぞれと前記E相との間の電圧である各相-E相間電圧を測定する電圧測定工程と、
前記保護導体の接地抵抗によって生じる電位差を除いて、前記対地絶縁抵抗に印加される電圧成分を抽出した所定の電圧値を、前記各相-E相間電圧にもとづいて算出する電圧値算出工程と、
前記所定の電圧値にもとづいて、前記漏洩電流のうち、対地容量成分を除いた、前記対地絶縁抵抗値に起因する成分を抽出する電流値算出工程と、を有した
ことを特徴とする漏洩電流算出方法。
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CN106483381B (zh) * | 2016-10-10 | 2019-03-19 | 东南大学 | 超高绝缘电阻测量仪用附加误差电流非对称补偿装置及方法 |
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JP6722928B1 (ja) * | 2019-03-20 | 2020-07-15 | マルチ計測器株式会社 | 零相電流計測方法及び装置 |
CN112327209B (zh) * | 2020-11-03 | 2022-09-13 | 中车青岛四方机车车辆股份有限公司 | 轨道车辆牵引系统漏电流检测方法、装置及轨道车辆 |
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KR101748554B1 (ko) | 2017-06-27 |
EP3199959A1 (en) | 2017-08-02 |
TW201621331A (zh) | 2016-06-16 |
US10145886B2 (en) | 2018-12-04 |
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