JP2011022007A - Method of measuring nonlinear resistance of stator coil in dynamo-electric machine, and nonlinear resistance measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for estimating characteristics of a field relief layer given to a stator coil end more precisely than before. <P>SOLUTION: In a nonlinear resistance measuring device of a stator coil mounted to a dynamo-electric machine, the field relief layer 44 is disposed while being wound around an outer periphery of a conductor 41 at an edge 24 of the stator coil. The nonlinear resistance measuring device includes: a measuring means of measuring surface potential at a plurality of places (n<SB>0</SB>-n<SB>6</SB>) of the field relief layer 44 while the field relief layer 44 has been disposed at the edge 24; and an estimating means of estimating current voltage characteristics of the field relief layer 44 by surface potential measured at two prescribed places (for example, n<SB>3</SB>, n<SB>4</SB>) from among the measured surface potential. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for measuring nonlinear resistance of a stator coil of a rotating electrical machine, and a nonlinear resistance measuring apparatus.

  Some rotating electrical machines (for example, large-capacity turbine generators) that convert rotational force into electric power include a stator coil.

  The end portion of the stator coil (hereinafter referred to as “stator coil end”) is not a portion that directly contributes to power generation, so that it is required to be compact. For this reason, an involute shape is adopted for the connecting portion between the half-turn coils at the stator coil end. Here, the involute shape refers to a shape in which the half-turn coil is three-dimensionally bent (curved).

  Then, terminal processing such as insulation coating is performed on the stator coil end, and a three-layer winding coil of U, V, and W is manufactured.

  The technology related to the manufacturing process of the stator coil includes, for example, (1) a half-turn coil coated with an insulating material is pre-impregnated with resin and molded press-cured, and then placed on the stator core (iron core). (2) After placing the half-turn coil coated with an insulating material on the stator core and completing the assembly inside and outside the stator core, vacuum degassing and pressure impregnation with thermosetting resin And techniques for drying and curing.

  By the way, the stator coil is provided with an insulating layer whose main component is mica on the coil conductor. And in the part which this insulating layer faces the side surface (slot side surface) of a stator core, discharge may generate | occur | produce. In order to prevent such discharge, a low resistance layer is applied to a portion where the discharge is likely to occur (straight portion of the stator coil).

  Further, when a voltage is applied to the coil conductor, the coil conductor and the low resistance layer are each configured as an electrode. In such a case, the equipotential lines generated between the electrodes are substantially parallel to the coil conductor and the low resistance layer. On the other hand, equipotential lines are distributed through the thickness direction of the main insulating layer and the surface of the coil end at the coil end outside the low resistance layer. On the coil end surface outside the end of the low resistance layer, the equipotential lines intersecting the main insulating layer are dense depending on the relative dielectric constant between the main insulating layer and the coil peripheral space and the resistivity of the coil end surface. Therefore, the potential gradient increases on the coil end surface, and the electric field in the coil end creeping direction concentrates.

  In particular, at the end portion (end surface) of the low resistance layer, the potential gradient is remarkably increased, and partial discharge or creeping discharge is likely to occur. Therefore, in order to prevent partial discharge or creeping discharge that occurs at the end of the low-resistance layer, an electric field relaxation layer is provided on the surface of the insulating layer to moderate the potential gradient.

  In designing such an electric field relaxation layer, it is necessary to accurately grasp the characteristics (performance) of a material used for the electric field relaxation layer (for example, an electric field relaxation tape mainly composed of SiC).

  Therefore, the manufacturer (or seller) of the electric field relaxation tape measures the characteristics (for example, current-voltage characteristics) of the electric field relaxation tape before sales, and provides the purchaser with a data sheet indicating the measurement results. ing. Then, the purchaser confirms the performance of the data sheet provided by the manufacturer, obtains various amounts necessary for electric field relaxation by measurement and analysis, and designs an electric field relaxation layer to be applied to the stator coil end.

  Various methods have been proposed for analyzing electric field relaxation tapes. For example, a method for analyzing the nonlinear resistance characteristic of the electric field relaxation layer using an equivalent circuit of a stator coil end has been proposed (Non-Patent Document 1). In addition, a method has been proposed in which the surface potential is measured in a state where an electric field relaxation layer is applied to the stator coil end, and the execution length necessary for electric field relaxation is analyzed (Patent Document 1).

IEEJ Transactions A (Basic, Materials, Common Category) Vol.104, No.9, 53-60 (1984) JP 2000-134877 A

  However, even when designing using the measurement and analysis results as described above, the nonlinear resistance characteristics of the electric field relaxation layer are affected by the storage conditions of the electric field relaxation tape and coil manufacturing conditions, and the nonlinearity after the coil is manufactured. Resistance characteristics may deviate from design values.

  An object of this invention is to provide the technique which estimates the nonlinear resistance characteristic of the electric field relaxation layer given to the stator coil end more accurately than before.

  The present invention for solving the above problems is a method for measuring the nonlinear resistance of a stator coil of a rotating electrical machine, wherein the coil end outside the low resistance layer end of the stator coil is wound around the outer periphery of a conductor. The electric field relaxation layer is disposed, and the electric field relaxation layer is disposed at a plurality of points of the electric field relaxation layer in a state where the electric field relaxation layer is disposed for a predetermined length necessary for electric field relaxation based on a design value from the end portion. A measurement step of measuring, and an estimation step of estimating a current-voltage characteristic of the electric field relaxation layer using the surface potential measured at two predetermined points of the measured surface potential.

  Further, in the estimation step, the first surface potential measured at the arrival point where the surface potential substantially reaches the potential of the conductor, and the surface potential does not reach the potential of the conductor, The second surface potential measured at the point closest to the arrival point may be selected as the surface potential used for estimating the current-voltage characteristics.

  Further, in the estimation step, an electric potential difference between the two points in the electric field relaxation layer is calculated from a difference in surface potential measured at the two points, and an insulating layer interposed between the conductor and the electric field relaxation layer The current value flowing between the two points in the electric field relaxation layer is calculated from the current value flowing in the electric field relaxation layer, and the current-voltage characteristic between the two points obtained from the calculated potential difference and the calculated current value is calculated. The current-voltage characteristics of the entire electric field relaxation layer may be estimated.

It is a figure which shows the structure of the turbine generator to which one Embodiment of this invention was applied. It is an enlarged view of a stator coil end. It is a figure which shows the structure of the measurement system which measures the cross section of a stator coil end part (coil end), and its surface potential. It is a figure which shows the function structure of information processing apparatus and a surface electrometer. It is a figure which shows the equivalent circuit model of a stator coil edge part. It is a figure which shows both the measurement result of the surface potential of a stator coil end, and the equivalent circuit model of a stator coil end. It is a graph showing the time waveform of the surface potential (V ₃ , V ₄ ) measured at n ₃ , n ₄ , the potential difference V _n4-3 , and the current value I _n4-3 flowing between n ₃ and n _4. is there. (A) It is a graph which shows the current-voltage characteristic of the electric field relaxation layer obtained by the conventional method. (B) It is a graph which shows the current-voltage characteristic of the electric field relaxation layer obtained by the method of this invention.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a structure of a turbine generator 1 to which an embodiment of the present invention is applied.

  As shown in the figure, the turbine generator 1 includes a stator frame 10, a stator 20 fixed to the stator frame 10, and a rotor 30 that is disposed inside the stator 20 and rotates.

  The stator 20 includes a stator core 21 disposed at a predetermined interval on the radially outer side of the rotor 30 and slots formed at a predetermined interval along the inner peripheral edge of the stator core 21 (each slot communicates in the axial direction). A stator coil 22 housed in the stator core 22, an end plate 23 disposed at the axial end of the stator core 21, and a stator coil support ring that supports the stator coil 22 with the stator coil end 24. 25 and a ring support 26 that fixes the stator coil support ring 25 to the end plate 23.

  The rotor 30 includes a rotor core (not shown) that rotates together with a rotation shaft (not shown), and a rotor coil (not shown) wound around the rotor core.

  FIG. 2 is an enlarged view of the stator coil end 24.

  As shown in the drawing, the involute shape described above is adopted for the stator coil end 24.

  The stator coil 22 is manufactured by connecting a plurality of half-turn coils. Specifically, the half-turn coils housed in each slot are connected outside the stator core 21 (the end portion of the stator coil end 24). Each half-turn coil has a ground insulating tape (main insulating layer 42 to be described later), a low resistance tape (low resistance layer 43 to be described later), an electric field relaxation tape (to be described later) on the outer periphery of a coil conductor (coil conductor 41 to be described later). The electric field relaxation layer 44), etc. to be wound is wound. That is, the insulation coating of the half-turn coils themselves, the electrical connection between the half-turn coils, the insulation coating of the connecting portions, and the like are performed, and three-phase winding coils of U, V, and W (stator coil 22). ) Is produced.

  FIG. 3 is a diagram showing a cross section of the stator coil end 24 and the configuration of the measurement system 2 that measures the surface potential thereof.

  As shown in the drawing, the measurement system 2 includes a surface potential meter 200 that measures the surface potential of the stator coil end 24, and an electric field relaxation tape (electric field relaxation layer 44) using the surface potential measured by the surface potential meter 200. An information processing device (PC) 100 that estimates characteristics and a power supply device 50 that applies a high test voltage (AC voltage) to the stator coil end 24 are provided.

  A main insulating layer (ground insulating tape) 42 containing mica as a main component is applied to the outer periphery of the coil conductor 41 at the stator coil end 24 (end portion of the stator coil 22).

  In addition, a low resistance layer 43 is applied to a linear portion that reaches the stator coil end 24 in the vicinity of the stator core 21 in order to prevent partial discharge that occurs at the portion where the main insulating layer 42 faces the slot wall surface of the stator core 21. ing. Here, the low resistance layer 43 is tightly fixed inside the slot of the stator core 21 and grounded together with the stator core 21. Note that the end of the low resistance layer 43 is arranged so as to come out of the stator core 21 by about several tens of millimeters.

  Further, when a voltage (an AC voltage output from a power supply device 50 described later) is applied to the coil conductor 41, the coil conductor 41 and the low resistance layer 43 are configured as electrodes. In such a case, equipotential lines generated between the electrodes are substantially parallel to the coil conductor 41 and the low resistance layer 43. On the other hand, equipotential lines are distributed through the thickness direction of the main insulating layer 42 and the surface of the coil end 24 in the coil end 24 outside the low resistance layer 43. On the surface of the coil end 24 outside the terminal of the low resistance layer 43, the main insulating layer 42 intersects depending on the difference in relative dielectric constant between the main insulating layer 42 and the coil peripheral space, the resistivity of the surface of the coil end 24, etc. Since the potential lines are densely distributed, the potential gradient increases on the surface of the coil end 24 and the electric field in the creeping direction of the coil end 24 is concentrated.

  In particular, at the end portion (end surface) of the low resistance layer 43, the potential gradient is remarkably increased, and partial discharge or creeping discharge is likely to occur. Therefore, in order to prevent partial discharge or creeping discharge that occurs at the end of the low-resistance layer 43, the surface of the main insulating layer 42 is provided with an electric field relaxation layer 44 for reducing the potential gradient. Here, the electric field relaxation layer 44 is wound so as to wrap a part of the end of the low resistance layer 43. In the present embodiment, silicon carbide (SiC) having nonlinear electric field relaxation characteristics is used as the material of the electric field relaxation layer 44.

  The surface potential meter 200 measures the surface potential at a plurality of points on the electric field relaxation layer 44. The surface potential meter 200 generally has a method of measuring by contacting or contacting a specimen. In any case, in a state where the test voltage is applied to the stator coil end 24, the surface potentiometer 200 measures the surface potential at the point by bringing the probe 51 into contact with or close to the point to be measured.

For example, the surface electrometer 200 uses the lap portion (the wrapping portion) between the electric field relaxation layer 44 and the low resistance layer 43 as a reference point n ₀ , and sequentially increases the electric field relaxation layer 44 in the direction away from the stator core 21. Measure the surface potential. In the illustrated example, the surface potential is measured at predetermined seven points (n _{0 to} n ₆ ). In this case, the interval between the points where the surface potential is measured is determined based on a data sheet indicating the characteristics of the electric field relaxation layer 44.

  In the above configuration, the surface potential at each point is sequentially measured. However, the surface potential at each point may be measured simultaneously.

  Further, the surface electrometer 200 acquires a voltage value (voltage value that changes with time) applied (output) by the power supply device 50 to the stator coil end 24.

  The information processing apparatus 100 acquires the surface potential of the stator coil end 24 and the voltage value applied to the stator coil end 24 by the power supply device 50 from the surface potentiometer 200. Then, the information processing apparatus 100 estimates the current-voltage characteristics of the electric field relaxation layer 44 using the acquired data. In addition, the estimation method of the current-voltage characteristic here is mentioned later.

  The components of the information processing apparatus 100 include a CPU that is a main control apparatus, a ROM that stores programs and the like, a RAM that temporarily stores data and the like as a main memory, and a surface electrometer 200 and the like. A communication device that performs communication, an input device (such as a keyboard and a mouse) that receives instructions from a user, an output device (such as a display) that displays various screens, and a system bus that serves as a communication path between each component; This can be achieved by a general computer equipped.

  Further, the surface electrometer 200 and the information processing apparatus 100 are communicably connected by a cable 150, for example.

  The power supply device 50 applies a high test voltage (alternating voltage) to the coil conductor 41 of the stator coil end 24.

  FIG. 4 is a functional configuration diagram of the information processing apparatus 100 and the surface electrometer 200.

  As shown in the figure, the surface electrometer 200 includes a measurement unit 210 and a communication unit 220.

The measurement unit 210 performs control for measuring the surface potential of the electric field relaxation layer 44 in a state of being disposed at the stator coil end 24. Specifically, the measurement unit 210 instructs the power supply device 50 to apply a test voltage to the stator coil end 24. Then, the measurement unit 210 performs a predetermined time (for example, 1 s) on the surface potential at one point (for example, n ₀ ) among the points to be measured (that is, the point where the probe is in contact or approaching). taking measurement. The measurement unit 210, the other point (e.g., point _{n 1, n 2, n 3} , n 4, n 5, in the order of _{n 6)} is measured by a predetermined time also the surface potential of the. Accordingly, the measurement unit 210 can obtain a graph showing the temporal change in the surface potential in each point (n 0 _{~n 6).}

Note that the point to be measured _(n 0 ~n ₆₎ may be arbitrarily changed. For example, the number of points to be measured may be increased or decreased. Further, it is possible to arbitrarily change also interval at each point to be measured (n 0 _{~n 6).} For example, the interval between the points may be changed according to the properties (for example, thickness, approximate dielectric constant, etc.) of the electric field relaxation layer 44.

  The measurement unit 210 measures the surface potential of the electric field relaxation layer 44 and also measures the output voltage (time waveform) of the power supply device 50.

  The communication unit 220 exchanges data with the information processing apparatus 200. For example, the communication unit 220 transmits the surface potential (data) measured by the measurement unit 210, the output voltage (data) of the power supply device 50, and the like to the information processing device 200 via the cable 150.

  In addition, the information processing apparatus 100 includes a calculation unit 110, a storage unit 120, and a communication unit 130.

  The communication unit 130 exchanges data with the surface electrometer 200. For example, the communication unit 130 receives the surface potential (data) transmitted from the surface potential meter 200 and the output voltage (data) of the power supply device 50.

  The storage unit 120 stores the surface potential (data) measured by the surface potential meter 200, the output voltage (data) of the power supply device 50, the calculation result (data) of the calculation by the calculation unit 110, and the like.

  The calculation unit 110 estimates the characteristics of the electric field relaxation layer 44 using the surface potential measured by the surface potential meter 200.

Specifically, the calculation unit 110 estimates the current-voltage characteristics of the electric field relaxation layer 44 using the surface potentials measured at two predetermined points among the surface potentials measured by the surface potential meter 200. Here, as the surface potential used for estimating the current-voltage characteristics, the surface potential measured at the arrival point (for example, n ₄ ) approximately reaching the potential of the coil conductor 41 and the surface potential are applied to the coil conductor 41. A surface potential that is not reached and is measured at a point closest to the arrival point (for example, n ₃ ) is selected.

  Here, the arrival of the surface potential means that the maximum voltage (amplitude) of the surface potential substantially coincides with the maximum voltage (amplitude) of the voltage output from the power supply device 50, or the temporal change of the surface potential. (Time waveform) substantially corresponds to the temporal change (time waveform) of the voltage output from the power supply device 50.

Therefore, in order to select the surface potential of the arrival point (for example, n ₄ ) and the point closest to the arrival point (for example, n ₃ ), the calculation unit 110 uses, for example, the power supply device 50 together with the surface potential (data). reading the output voltage _{V C} (data) from the storage unit 120 by comparing. Then, (from the storage unit 120) to substantially match the surface potential to the maximum voltage of the output voltage V _C (amplitude) (data), the arrival point (for example, n ₄₎ is selected as the surface potential of the (data). The maximum voltage of the surface potential and the output voltage V _C (amplitude) lower than the surface potential (data) measured at the nearest point to the arrival point, the surface potential of the point closest to the arrival point (for example, n ₃₎ (Read from the storage unit 120).

  Next, the calculation unit 110 substitutes the surface potential measured at the two points in the equivalent circuit model of the stator coil end 24 to obtain the current-voltage characteristics of the electric field relaxation layer 44.

FIG. 5 is a diagram illustrating an example of an equivalent circuit model of the stator coil end 24 (stator coil end). As shown in the figure, the equivalent circuit model is a general RC ladder circuit as an equivalent circuit model of the stator coil end 24. Here, C _n represents a capacitance per unit volume of the main insulating layer 42. Also, C _L represents the capacitance per unit volume of the low-resistance layer 43. R _n represents the nonlinear resistance of the electric field relaxation layer 44. R _L represents the nonlinear resistance of the low resistance layer 43. The sites main insulating layer 42 that power supply 50 (capacitors C _n) are connected (wire) corresponds to a coil conductor 41.

FIG. 6 is a diagram showing an equivalent circuit model of the stator coil end 24 and a graph showing the surface potential at each point (n _{0 to} n ₆ ) of the electric field relaxation layer 44. The black dots on the graph indicate the surface potential at each point (n _{0 to} n ₆ ).

  Hereinafter, the process of estimating the current-voltage characteristics of the electric field relaxation layer 44 will be described with reference to FIG.

First, the calculation unit 110 calculates a voltage drop V _(n4-3) of the surface potential measured at two points (n ₄ , n ₃ ). Specifically, the calculation unit 110 calculates the voltage drop V _(n4-3) according to the following formula 1.

_{V (n4-3) = V n4 -V} n3 ··· ( Equation 1)
Here, V _n4 is the surface potential measured at point n ₄ , and V _n3 is the surface potential measured at point n ₃ . Further, in the equivalent circuit model shown, the voltage drop _{V (N4-3)} is a value of voltage applied to the non-linear resistance _{R n} of the electric field relaxation layer 44 between the point _{n 4} and the point _{n 3.} For reference, changes over time (time waveform) of V _n4 “solid line”, V _n3 “broken line”, V _(n4-3) “one-dot chain line” are shown in FIG.

Further, the surface potential V _n4 measured at the point n ₄ substantially converges to the potential of the coil conductor 41 as described above. Therefore, it can be considered that the following formula (Formula 2) holds.

V _n4 = V _n5 = V _n6 (Expression 2)
Here, V _n5 is the surface potential measured at point n ₅ , and V _n6 is the surface potential measured at point n ₆ .

  Further, the following equation (Equation 3) is established according to Kirchhoff's law.

I _{(n4-3) =} I _(n5-4) + I _C (Expression 3)
_{Here, I (N4-3)} is a value of a current flowing between the point _{n 4} and the point _{n 3} of the electric field relaxation layer _{44, I (n5-4)} is the point _{n 5} of the electric field relaxation layer 44 is the value of the current flowing between the point n _4. I _C is the magnitude of the charging current of the main insulating layer 42 immediately below the point n ₄ .

When the above mathematical formula 2 is established, no current flows between the point n ₅ and the point n ₄ of the electric field relaxation layer 44. Therefore, I _(n5-4) = 0, and the following formula (Formula 4) is established.

_{I (n4-3) = I C ···} ( Equation 4)
The magnitude I _C of the charging current of the main insulating layer 42 immediately below the point n ₄ can be expressed by the following formula (Formula 5) (generally from the relational expression “Q = CV” between the charge Q and the voltage V of the capacitor). ).

I _C = C _n × {d (V _C −V _n4 ) / dt} (Formula 5)
Here, V _C is the output voltage of the power supply device 50 (test voltage), t represents time. For reference, the time change (time waveform) of I _(n4-3) “dotted line” is shown in FIG.

As described above, the value I _(n4-3) of the current flowing between the point n ₄ and the point n ₃ of the electric field relaxation layer 44 can be calculated by substituting the calculation result of Equation 5 into Equation 4.

That is, the arithmetic unit 110, based on the above equivalent circuit model, the output voltage Vc of the power supply device 50, the surface potential _{V n4} measured at point _{n 4,} reading a predetermined _{C n,} from the storage unit 120, Substituting into Equation 5 to calculate I _(n4-3) .

And the calculating part 110 produces _| generates a correspondence table about V _(n4-3) and I _(n4-3) of the same time t (for example, memorize _| stores in the memory _| storage part 120). Thereby, the calculating part 110 can graph I _(n4-3) which changes according to V _(n4-3), and can display it on display apparatuses, such as a display.

  As described above, the calculation unit 110 can estimate the current-voltage characteristics of the entire electric field relaxation layer 44 in the state of being arranged in the stator coil end 24.

  FIGS. 8A and 8B are graphs showing current-voltage characteristics of the electric field relaxation layer 44 estimated by the calculation unit 110. FIG. 8A is a graph showing current-voltage characteristics estimated by a conventional method. FIG. 8B is a graph showing current-voltage characteristics estimated by the method of the above embodiment of the present application.

  In FIG. 8A, the solid line shown is a graph showing the current-voltage characteristic (estimated value) estimated before the electric field relaxation layer 44 is disposed on the stator coil end 24 (before manufacture). Further, the dotted line shown in the figure is a graph showing current-voltage characteristics (actual measurement values) measured in a state (after fabrication) in which the electric field relaxation layer 44 is disposed on the stator coil end 24. Here, in order to give a significant difference between the current-voltage characteristics before and after manufacture, the storage state of the electric field relaxation tape, the manufacturing conditions, etc. are drastically changed from the conventional management conditions. As shown in the figure, in the conventional method, the actual measurement value and the estimated value may deviate.

  On the other hand, in FIG. 8B, the solid line shown in the figure is estimated after the electric field relaxation layer 44 is disposed on the stator coil end 24 (after fabrication) using the above-described Equations 1 and 5 (Equation 4). It is a graph which shows an electric current-voltage characteristic (estimated value). Further, the dotted line shown in the figure is a graph showing current-voltage characteristics (actual measurement values) measured in a state (after fabrication) in which the electric field relaxation layer 44 is disposed on the stator coil end 24. As illustrated, according to the method of the present embodiment, the current-voltage characteristics of the electric field relaxation layer 44 can be estimated with high accuracy.

  As described above, by accurately estimating the current-voltage characteristics of the electric field relaxation layer 44 after the stator coil is manufactured, the design of the electric field relaxation layer 44 to be disposed on the stator coil end 24 (for example, the electric field relaxation layer 44 The length d) etc. can be optimized. As a result, a highly reliable rotating electrical machine can be manufactured.

  In addition, in order to make an understanding of the structure of the information processing apparatus 100 and the surface electrometer 200 easy, each component mentioned above is classified according to the main processing content. The invention of the present application is not limited by the way of classifying the components or their names. The configurations of the information processing apparatus 100 and the surface electrometer 200 can be classified into more components depending on the processing content. Moreover, it can also classify | categorize so that one component may perform more processes.

  Each functional unit may be constructed by hardware (such as an ASIC). In addition, the processing of each functional unit may be executed by one hardware, or may be executed by a plurality of hardware.

  In addition, said embodiment intends to illustrate the summary of this invention, and does not limit this invention. Many alternatives, modifications, and variations will be apparent to those skilled in the art.

  For example, in the above embodiment, the information processing apparatus 200 estimates the current-voltage characteristics of the electric field relaxation layer 44. However, the present invention is not limited to this. For example, the functions of the calculation unit 110 and the storage unit 120 of the above embodiment may be realized by the surface electrometer 200.

  In this case, the surface electrometer 200 includes a measuring device, a storage device, a comparator, and an arithmetic device.

The measuring device has at least two probes for simultaneously measuring the surface potential (time waveform) of the electric field relaxation layer 44 and the output voltage (time waveform) of the power supply device 50. The measuring device, as in the above embodiment, in a direction away from the stator core 21 (from n ₀ to n _6), sequentially measuring the surface potential of the electric field relaxation layer 44. Further, the measuring device digitizes the measured surface potential and output voltage at a predetermined sampling frequency and stores them in the storage device. Therefore, the storage device stores the surface potential measured by the measuring device and the output voltage of the power supply device 50 as digitized data.

  When the measured surface potential and the output voltage of the power supply device 50 are input from the storage device, the comparator determines whether both data (for example, the maximum voltage) match and calculates the determination result. Output to the device. The order in which the surface potential (data) is input to the comparator is input in the order measured by the measuring device.

When the comparator determines that both data match for the first time, the arithmetic unit selects the surface potential (data) as the surface potential (data) measured at the arrival point. Similarly to the above-described embodiment, the arithmetic device selects the surface potential (data) measured at the point closest to the arrival point as the surface potential at the point closest to the arrival point (for example, n ₃ ).

  After that, the arithmetic device estimates the current-voltage specification of the electric field relaxation layer 44 using the surface potentials at the two selected points, as in the above embodiment.

  With the configuration as described above, the current-voltage characteristics of the electric field relaxation layer 44 in the state of being arranged at the stator coil end 24 can be estimated at a higher speed than in the above embodiment.

In addition, as described above, when the measured surface potential is simply digitized at a predetermined sampling frequency, a phase shift occurs in the time waveform of the surface potential measured at each measurement point (n _{0 to} n ₆ ). There is. Therefore, the measuring apparatus may be provided with a function for correcting this phase shift. In this case, the measurement device reads the numerical data of the surface potential measured at each measurement point (n _{0 to} n ₆ ), and specifies the reference point of the accurate phase of the surface potential. The measuring device, based on the reference point specified to correct the phase shift of the surface potential of each measurement point (n 0 _{~n 6).}

Further, instead of correcting the phase shift as described above, the surface potential of the electric field relaxation layer 44 may be measured (acquired) so that the phase shift does not occur in advance. In this case, the measuring device monitors the test voltage (AC voltage) output from the power supply device 50 and specifies the zero-cross point of the test voltage waveform as a trigger signal (trigger signal function). Then, the measuring device measures the surface potential of the electric field relaxation layer 44 for a certain period of time at the timing at which the zero cross point is specified (digitized at a predetermined sampling frequency), and stores it in the storage device. Thereby, a phase shift does not occur in the time waveform of the surface potential measured at each measurement point (n _{0 to} n ₆ ).

  In addition, when the output voltage of the power supply device 50 is a high voltage, it is necessary to consider safety with respect to the high voltage test. Therefore, it is preferable that the measurement unit 210 that measures the surface potential of the electric field relaxation layer 44 and the calculation unit 110 that estimates the current-voltage characteristics of the electric field relaxation layer 44 be electrically separated. Therefore, for the cable 150 of the above-described embodiment, for example, it is preferable to use an optical fiber cable that hardly generates heat. In this case, the communication unit 130 of the information processing apparatus 100 and the communication unit 220 of the surface electrometer 200 include an IO port (light voltage converter) that enables communication using an optical fiber cable.

  DESCRIPTION OF SYMBOLS 1 ... Turbine generator, 2 ... Measurement system, 10 ... Stator frame, 20 ... Stator, 21 ... Stator core, 22 ... Stator coil, 23 ... End plate, 24 ... Stator coil end, 25 ... Stator coil support ring, 26 ... Ring support, 30 ... Rotor, 41 ... Coil conductor, 42 ... Main insulation layer , 43 ... low resistance layer, 44 ... electric field relaxation layer, 50 ... power supply device, 51 ... probe, 100 ... information processing device (PC), 110 ... arithmetic unit, 120 · ..Storage unit, 130... Communication unit, 150 .. cable, 200... Surface electrometer, 210.

Claims (10)

A method for measuring nonlinear resistance of a stator coil of a rotating electrical machine,
At the end of the stator coil, an electric field relaxation layer is disposed around the outer periphery of the conductor,
A measurement step of measuring a surface potential at a plurality of points of the electric field relaxation layer in a state where the electric field relaxation layer is disposed at the end;
Estimating the current-voltage characteristics of the electric field relaxation layer using the surface potential measured at two predetermined points of the measured surface potential,
A non-linear resistance measuring method. A nonlinear resistance measuring method according to claim 1,
In the estimation step,
A first surface potential measured at an arrival point where the surface potential substantially reaches the potential of the conductor;
A second surface potential measured at a point closest to the arrival point among the plurality of points, the surface potential not reaching the potential of the conductor;
Is selected as the surface potential used to estimate the current-voltage characteristics,
A non-linear resistance measuring method. A nonlinear resistance measuring method according to claim 1 or 2,
In the estimation step,
From the difference between the surface potentials measured at the two points, calculate the potential difference between the two points in the electric field relaxation layer,
From the current value flowing in the insulating layer interposed between the conductor and the electric field relaxation layer, the current value flowing between the two points in the electric field relaxation layer is calculated,
Estimating the current-voltage characteristics between the two points obtained from the calculated potential difference and the calculated current value as the current-voltage characteristics of the entire electric field relaxation layer,
A non-linear resistance measuring method. A non-linear resistance measuring device for a stator coil attached to a rotating electrical machine,
At the end of the stator coil, an electric field relaxation layer is disposed around the outer periphery of the conductor,
Measuring means for measuring a surface potential at a plurality of points of the electric field relaxation layer in a state where the electric field relaxation layer is disposed at the end,
An estimation means for estimating a current-voltage characteristic of the electric field relaxation layer using surface potentials measured at two predetermined points among the measured surface potentials,
A non-linear resistance measuring apparatus. The nonlinear resistance measuring device according to claim 4,
The estimation means includes
A first surface potential measured at an arrival point where the surface potential substantially reaches the potential of the conductor;
A second surface potential measured at a point closest to the arrival point among the plurality of points, the surface potential not reaching the potential of the conductor;
Is selected as the surface potential used to estimate the current-voltage characteristics,
A non-linear resistance measuring apparatus. The nonlinear resistance measuring device according to claim 5,
The measuring means includes
When a test AC voltage is applied from the power supply device to the end of the stator coil, the surface potential of the electric field relaxation layer is measured,
The estimation means includes
The time waveform of the surface potential measured in the electric field relaxation layer is compared with the time waveform of the AC voltage output from the power supply device, and a point where both time waveforms are substantially equivalent is defined as the arrival point. select,
A non-linear resistance measuring apparatus. The nonlinear resistance measuring device according to claim 6,
The estimation means includes
By calculating the difference between the time waveform of the first surface potential and the time waveform of the second surface potential, the potential difference between the two points in the electric field relaxation layer is calculated.
A non-linear resistance measuring apparatus. The nonlinear resistance measuring apparatus according to claim 7,
The estimation means includes
Obtain the difference between the time waveform of the alternating voltage output from the power supply device and the time waveform of the surface potential measured at the arrival point,
Differentiating the obtained difference value with respect to time, and multiplying the capacitance between the two points of the insulating layer interposed between the conductor and the electric field relaxation layer, the two points in the electric field relaxation layer The value of the current flowing through
A non-linear resistance measuring apparatus. The nonlinear resistance measuring device according to any one of claims 6 to 8,
The measuring means includes
Using the AC voltage output from the power supply device as a trigger signal, the surface potential of the electric field relaxation layer is measured for a certain period of time.
A non-linear resistance measuring apparatus. The nonlinear resistance measuring apparatus according to any one of claims 4 to 9,
An optical voltage converter for electrically disconnecting the measuring means and the estimating means;
A non-linear resistance measuring apparatus.

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