Method for detecting and locating faults in an electrical system, particularly for a rotating machine on board an aircraft.

Abstract

This disclosure relates to a method (300, 600, 900) for detecting faults in a rotating electrical machine comprising a first winding phase (A1), a second winding phase (B1), and a frame (D), including steps of applying electrical potentials to the winding phases to identify partial discharge onset voltages, and of comparing the partial discharge onset voltages to deduce the presence of faults in different parts of the electrical machine. Abstract figure: Fig. 5

Description

Title of the invention: Method for detecting and locating faults in an electrical system, in particular for a rotating machine on board an aircraft. FIELD OF INVENTION

[0001] This disclosure relates to the field of fault detection in rotating electrical machine windings. It is particularly applicable to rotating machines installed in aircraft. STATE OF THE ART

[0002] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types of aircraft and those already in service, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0003] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and whose integration and use in civil aviation have moderate environmental consequences, with the aim of improving the energy efficiency of aircraft.

[0004] Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, in particular through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and, as essential complements to technological progress, aviation biofuels.

[0006] In order to increase the performance of electrical systems on board aircraft, that is to say, to increase the onboard electrical power, it is It is desirable to be able to increase the current levels flowing through the cables of an electrical system, or the voltage levels on the various components of the electrical system. However, increasing voltage levels also increases the risk of partial discharges, that is, rapid and localized discharges, occurring in the gas (typically, the air) surrounding the components and not immediately short-circuiting their electrical insulation but contributing to the degradation of this insulation and its premature failure through their mechanical, thermal and chemical action when the electrical stress exceeds a critical value.

[0007] Partial discharges can occur even at a voltage applied across the insulation that is lower than its breakdown voltage, since, locally, the voltage can exceed this breakdown voltage due to local faults in the electrical system. In particular, for an electrical machine, faults in the winding insulation system can cause such discharges. These faults can be intrinsic to the dielectric materials (varnish, impregnation resin, paper), or created during the various stages of the machine's production process (coil insertion, impregnation, shrink-fitting, etc.).

[0008] Within an electrical machine, partial discharges can occur in several separate electrical insulations. Partial discharges progressively reduce the insulation lifetime and can, in the medium to long term, lead to dielectric breakdown inducing a short circuit in the winding.

[0009] Within an electrical machine, partial discharges may occur, in particular, in: - the insulation between several phases of an electrical machine winding, - the insulation between two turns of the same phase of the winding, - the insulation between one phase of the electrical winding and ground.

[0010] During the manufacture of an electrical machine, tests are carried out at several stages to ensure the conformity of the parts and to identify any defects. These tests include: - Partial discharge inception voltage (PDIV) tests, which essentially consist of progressively increasing the voltage from a minimum value up to a level at which partial discharge pulses are recorded. The partial discharge inception voltage corresponds to the lowest applied voltage at which the amplitude of these pulses exceeds a predefined threshold value. The methods for detecting partial discharge pulses are described in the international standard IEC60270; - surge tests, which consist of applying voltage pulses, higher than the nominal voltage, at regular intervals to an electrical winding in order to detect defects between the turns of the winding; - resistance tests of the electrical phases and resistance of the winding insulation; - High potential tests, in direct current or alternating current (DC HiPot test & AC HiPot test), which consist of applying a high voltage beyond the nominal voltage to an electrical insulation and checking if the current intensity passing through the insulation is greater than a predefined threshold value.

[0011] Figures 1a, 1b, and 1e represent sequences of PDIV tests performed in the prior art to detect defects in a rotating electrical machine winding. These tests are carried out under sinusoidal voltage. The examples provided correspond to a three-phase winding, but those skilled in the art will easily be able to adapt them to a greater or lesser number of winding phases. Figures 1a and 1b represent tests carried out after the first phase of manufacturing the electrical machine, when the three phases of the three-phase winding are not yet connected to each other. Each phase comprises a first end a1, b1, c1. A second end a12, b12, c12 of each phase remains accessible. It is therefore possible to carry out tests by connecting a test device to this second end. [Fig.the] represents a configuration that can be tested at the end of a second phase of manufacturing the electrical machine, when the three phases of the three-phase winding have been connected together, so that the second ends are no longer free and together form a neutral point N which can only adopt a single value of electrical potential.

[0012] With reference to [Fig. 1a], in order to test the electrical insulation between one phase (phase A1 in the figure) and ground, a potential HV is applied to phase A1 and the frame D is connected to ground GND. Phases B1 and C1, which are not being tested, are at a floating potential. The potential applied to phase A1 is gradually increased until a charge exceeding a predefined threshold value is detected between phase A1 and the frame D. As soon as such a charge is detected, the partial discharge appearance voltage (PDIV) has been reached. If the PDIV is lower than expected, a fault in the electrical insulation between phase A1 and the frame has been identified. The same procedure is applied to identify faults in the insulation between phase B1 and the frame, or between phase C1 and the frame.

[0013] With reference to [Fig.lb], in order to test the electrical insulation between two phases (in [Fig.lb], between phases Al and Bl), phase B1 is connected to ground GND, and A high-voltage potential (HV) is applied to phase Al. Phase Cl, which is not being tested, and the frame D are at a floating potential. The potential applied to phase Al is gradually increased until a charge exceeding a predefined threshold value is detected between phases Al and Bl. As soon as such a charge is detected, the partial discharge appearance voltage (PDIV) has been reached. If the PDIV is lower than expected, a fault in the electrical insulation between phase Al and phase Bl has been identified. The same procedure is used to identify faults in the insulation between phase Al and phase Cl, or between phases Bl and Cl.

[0014] In both cases, such methods make it possible to highlight the existence of a defect in the insulation (phase / casing insulation or interphase insulation), but do not make it possible to locate where, in the insulation, the defect is located.

[0015] With reference to [Fig. 1e], once the phases are connected to the neutral point N, only the electrical insulation between, on the one hand, the three phases of the winding and, on the other hand, the frame, can be tested to identify a fault. For this purpose, the same potential HV is applied to the three phases of the winding at their respective first free ends a1, b1, cl1, and the frame is grounded GND. The potential applied to phases A1, b1, and cl1 is progressively increased until a charge exceeding a predefined threshold value is detected between these phases and the frame. As soon as such a charge is detected, the partial discharge voltage PDIV has been reached. If the PDIV is lower than expected, a fault has been identified in the electrical insulation between the phases and the frame.

[0016] This test makes it possible to detect the presence of a fault somewhere in the insulation between the phases and the casing, but does not in any way make it possible to know the location of such a fault.

[0017] Thus, although the tests mentioned here make it possible to detect the existence of defects in the electrical insulation of a rotating machine, they do not make it possible to determine precisely in which part of the machine the defects are located. It is therefore difficult to intervene locally to correct these defects and prevent premature failure of the machine. EXPOSED

[0018] One objective sought is therefore to enable the precise determination of the location of a defect in the insulation of an electrical winding of a rotating electrical machine.

[0019] To this end, a method for detecting faults in a rotating electrical machine is proposed, comprising a first winding phase, a second winding phase, and a frame, the first winding phase being equipped with a first free end and second free end, the process comprising the steps of: a. simultaneous application of an increasing electrical potential to the first free end and the second free end, the frame being maintained at zero electrical potential, so as to identify a reference partial discharge onset voltage at which partial discharges of an amplitude greater than a reference threshold appear in the electrical machine, b. application of an increasing electrical potential to the first free end, the second free end being maintained at zero electrical potential, so as to identify a first partial discharge onset voltage at which partial discharges of an amplitude greater than a first predefined threshold appear in the first winding phase, c. application of an increasing electrical potential to the second free end, the first free end being maintained at zero electrical potential, so as to identify a second partial discharge onset voltage at which partial discharges of an intensity greater than a second predefined threshold appear in the first winding phase, d. verification of a condition, the condition being: i. the first partial discharge onset voltage is lower than the reference partial discharge onset voltage, and ii. The second partial discharge onset voltage is lower than the reference partial discharge onset voltage. e. if the condition is met, determination that a fault exists in the first winding phase, f. if the condition is not met, determination that a fault exists in an insulation between the first winding phase and the frame of the rotating electrical machine.

[0020] In addition to the known prior art tests illustrated in Figures 1a, 1b, or 1a, the use of configurations in which a potential is applied to one end of an assembly—that is, to one phase or a plurality of phases—while maintaining another end of the assembly at zero potential, and then of identical configurations in which the potentials applied to the two ends are reversed, makes it possible to determine in which part of said assembly the defect causing the partial discharges is located. This allows, in particular, for more targeted intervention. quickly to repair the winding or insulation in which the fault is located.

[0021] According to some embodiments, the method includes, after determining that a fault exists in the first winding phase, determining a position of the fault in the first winding phase from a comparison between the first voltage of appearance of partial discharges and the second voltage of appearance of partial discharges.

[0022] According to some implementations, determining the position of the fault in the first winding phase includes one of the following: • a determination that a fault exists in a portion of the first winding phase closer to the second free end when the second partial discharge onset voltage is strictly lower than the first partial discharge onset voltage, • a determination that a fault exists in a central half of the first winding phase when the second partial discharge onset voltage is substantially equal to the first partial discharge onset voltage, and • a determination that a fault exists in a portion of the first winding phase closer to the first free end when the second partial discharge appearance voltage is strictly greater than the first partial discharge appearance voltage.

[0023] According to some embodiments, the method comprises, after determining that a defect exists in the insulation between the first winding phase and the casing: - a determination of the position of the fault in the insulation between the first winding phase of the rotating electrical machine and the electrical casing of the rotating electrical machine, or - a determination that a fault location in the insulation between the first winding phase of the rotating electrical machine and the frame of the rotating electrical machine cannot be identified,

[0024] the determination being carried out on the basis of a comparison between, on the one hand, the reference partial discharge onset voltage and, on the other hand, at least one of the first partial discharge onset voltage and the second partial discharge onset voltage.

[0025] According to some implementations, the determination includes one of: • a determination that a fault exists in a portion of the insulation between the first winding phase and the frame closer to the first free end than to the second free end when: • the first partial discharge onset voltage is approximately equal to the reference partial discharge onset voltage, and • The second partial discharge onset voltage is different from the reference partial discharge onset voltage, • a determination that a fault position in the insulation between the first winding phase and the frame cannot be identified when: • the first partial discharge onset voltage is approximately equal to the reference partial discharge onset voltage, and • the second partial discharge onset voltage is approximately equal to the reference partial discharge onset voltage, • a determination that a fault exists in a portion of the insulation between the first winding phase and the frame closer to the second free end than to the first free end when: • the second reference partial discharge onset voltage is substantially equal to the reference partial discharge onset voltage, and • the first partial discharge onset voltage is different from the reference partial discharge onset voltage.

[0026] A method for detecting faults in a rotating electrical machine is further proposed, comprising a first winding phase, a second winding phase, and a frame, the first winding phase being provided with a first free end and a second free end, the method comprising the steps of: a. simultaneous application of an increasing electrical potential to the first free end and the second free end, the second winding phase being maintained at zero electrical potential, so as to identify a reference partial discharge onset voltage at which partial discharges of an amplitude greater than a reference threshold appear in the electrical machine, b. applying an increasing electrical potential to the first free end, while the second free end and the second winding phase are maintained at zero electrical potential, so as to identify a first partial discharge onset voltage at which partial discharges of an amplitude greater than a first predefined threshold appear in the electrical machine. c. application of an increasing electrical potential to the second free end, the first free end and the second winding phase being maintained at zero electrical potential, so as to identify a second partial discharge onset voltage at which partial discharges of an intensity greater than a second predefined threshold appear in the electrical machine, d. verification of a condition, the condition being: i. the first partial discharge onset voltage is lower than the reference partial discharge onset voltage, and ii. The second partial discharge onset voltage is lower than the reference partial discharge onset voltage. e. if the condition is met, determination that a fault exists in the first winding phase, f. if the condition is not met, determination that a fault exists in an insulation between the first winding phase and the second winding phase.

[0027] According to some embodiments, the method includes, after determining that a fault exists in the first winding phase, determining a position of the fault in the first winding phase from a comparison between the first voltage of appearance of partial discharges and the second voltage of appearance of partial discharges.

[0028] According to some implementations, determining the position of the fault in the first winding phase includes one of the following: • a determination that a fault exists in a portion of the first winding phase closer to the second free end than to the first free end when the first partial discharge onset voltage is strictly greater than the second partial discharge onset voltage, • a determination that a fault exists in a central half of the first winding phase when the first partial discharge onset voltage is substantially equal to the second partial discharge onset voltage, and • a determination that a fault exists in a portion of the first winding phase closer to the first free end than to the second free end when the first partial discharge onset voltage is strictly less than the second partial discharge onset voltage.

[0029] According to certain embodiments, the method comprises, after determining that a defect exists in the insulation between the first winding phase and the second winding phase: - a determination of the position of the fault in the insulation between the first winding phase and the second winding phase, or - a determination that a fault position in the insulation between the first winding phase and the second winding phase cannot be identified,

[0030] the determination being carried out on the basis of a comparison between, on the one hand, the reference partial discharge onset voltage and, on the other hand, at least one of the first partial discharge onset voltage and the second partial discharge onset voltage.

[0031] According to some implementations, the determination includes one of: • a determination that a defect exists in a portion of the insulation between the first winding phase and the second winding phase closer to the first free end of the first winding phase than to the second free end of the first winding phase when: • the first partial discharge onset voltage is approximately equal to the reference partial discharge onset voltage, and • The second partial discharge onset voltage is different from the reference partial discharge onset voltage, • a determination that a fault position in the insulation between the first phase and the second phase cannot be identified when: • the first partial discharge onset voltage is approximately equal to the reference partial discharge onset voltage, and • the second partial discharge onset voltage is approximately equal to the reference partial discharge onset voltage, • a determination that a defect exists in a portion of the insulation between the first winding phase and the second winding phase closer to the second free end of the first winding phase than to the first free end of the first winding phase when: • the second reference partial discharge onset voltage is substantially equal to the reference partial discharge onset voltage, and • the first partial discharge onset voltage is different from the reference partial discharge onset voltage.

[0032] A method for detecting faults in a rotating electrical machine is further proposed, comprising a first winding phase, a second winding phase and a frame,

[0033] the first winding phase being provided with a free end and the second winding phase being provided with a free end,

[0034] the first winding phase and the second winding phase being further connected at a neutral point, the method comprising the steps of: a. simultaneous application of an increasing electrical potential to the free end of the first winding phase and to the free end of the second winding phase, the frame being maintained at zero electrical potential, so as to identify a reference partial discharge onset voltage at which partial discharges of an intensity greater than a reference threshold appear in the electrical machine, b. application of an increasing electrical potential to the free end of the first winding phase, the free end of the second winding phase being maintained at zero electrical potential, so as to identify a first partial discharge onset voltage at which partial discharges of an intensity greater than a first predefined threshold appear in the electrical machine, c. application of an increasing electrical potential to the free end of the second winding phase, the free end of the first winding phase being maintained at zero electrical potential, so as to identify a second partial discharge onset voltage at which partial discharges of an intensity greater than a second predefined threshold appear in the first winding phase, d. verification of a condition, the condition being: • the first partial discharge onset voltage is lower than the reference partial discharge onset voltage, and • the second partial discharge onset voltage is lower than the reference partial discharge onset voltage, e. if the condition is met, determination that a defect exists in one of the first winding phases and the second winding phases, f. If the condition is not met, determination that a defect exists: • in the insulation between, on the one hand, the first winding phase and the second winding phase and, on the other hand, the casing, and / or • in one of the first winding phase and / or the second winding phase.

[0035] According to some embodiments, the method includes, after determining that a fault exists in one of the first winding phase and the second winding phase, determining a position of the fault from a comparison between the first partial discharge appearance voltage and the second partial discharge appearance voltage.

[0036] According to some implementations, determining the position of the fault in one of the first winding phase and the second winding phase includes one of: • a determination that a fault exists in the first winding phase when the second partial discharge onset voltage is strictly greater than the first partial discharge onset voltage, • a determination that a fault exists in one of the first winding phase and the second winding phase, closer to the neutral point than to the first free end of the first winding phase or the first free end of the second winding phase, when the second partial discharge appearance voltage is substantially equal to the first partial discharge appearance voltage, and • a determination that a fault exists in the second winding phase when the second partial discharge appearance voltage is strictly less than the first partial discharge appearance voltage.

[0037] According to certain embodiments, the method comprises, after determining that a fault exists in the insulation between, on the one hand, one of the first winding phase and the second winding phase and, on the other hand, the casing, and / or that a fault exists in one of the first winding phase and the second winding phase, a determination of a position of the fault on the basis of a comparison between, on the one hand, the reference partial discharge onset voltage and, on the other hand, one of the first partial discharge onset voltage and the second partial discharge onset voltage.

[0038] According to some implementations, the determination includes one of the following: • a determination that a defect exists: • in a portion of the insulation between, on the one hand, the first winding phase and the second winding phase and, on the other hand, the frame, said portion being located closer to the first free end of the first winding phase than to the first free end of the second winding phase, and / or • between turns of the Al or Bl phases,

[0039] when the first partial discharge onset voltage is substantially equal to the reference partial discharge onset voltage, • a determination that a defect exists: • in a portion of the insulation between, on the one hand, the first winding phase and the second winding phase and, on the other hand, the frame, said portion being located closer to the first free end of the second winding phase than to the first free end of the first winding phase, and / or • between turns of the Al or Bl phases,

[0040] when the second partial discharge onset voltage is substantially equal to the reference partial discharge onset voltage, • a determination that a defect exists in one of the first winding phase and the second winding phase and, on the other hand, the casing, when: • the first partial discharge onset voltage is strictly greater than the reference partial discharge onset voltage, and / or • the second partial discharge onset voltage is strictly greater than the reference partial discharge onset voltage.

[0041] This disclosure further relates to a fault detection system configured to implement one of the processes defined above.

[0042] This disclosure further relates to a computer program product comprising instructions which, when the program is executed by a computer, lead to the implementation of the verification and determination steps of one of the processes defined above. DESCRIPTION OF THE FIGURES

[0043] Figs [Fig.la], [Fig.lb] and [Fig.le] schematically represent three prior art configurations allowing tests on a three-phase electrical machine, so as to identify faults in the machine.

[0044] Figures [Fig. 2a] and [Fig. 2b] schematically represent test configurations proposed to locate faults, according to an initial configuration of the electrical machine.

[0045] Fig. 3 schematically represents a test sequence for the first configuration, in order to locate a fault within a winding phase.

[0046] Fig. 4 schematically represents a test sequence for the first configuration, in order to locate a fault in insulation between a winding phase and the frame of the electrical machine.

[0047] Fig. 5 schematically represents a test sequence for the first configuration, in order to locate a fault in the electrical machine.

[0048] Figures [Fig. 6a] and [Fig. 6b] schematically represent test configurations proposed to locate faults, according to a second configuration of the electrical machine.

[0049] Fig. 7 schematically represents a test sequence for the second configuration, in order to locate a fault in a winding phase.

[0050] Fig. 8 schematically represents a test sequence for the second configuration, in order to locate a fault in an insulation between two winding phases.

[0051] Fig. 9 schematically represents a test sequence for the second configuration, in order to locate a fault in the electrical machine.

[0052] Fig. 10a and Fig. 10b schematically represent proposed test configurations for locating faults, according to a third configuration of the electrical machine.

[0053] Fig. 11 schematically represents a test sequence for the third configuration, in order to locate a fault in a set of two winding phases.

[0054] Fig. 12 schematically represents a test sequence for the third configuration, in order to locate a fault in an insulation between the two-phase assembly and the frame, and / or in one of the two winding phases of the assembly.

[0055] Fig. 13 schematically represents a test sequence for the third configuration, in order to locate a fault in the electrical machine.

[0056] Throughout the figures, the same reference symbols represent identical or similar elements. DETAILED DESCRIPTION OF IMPLEMENTATION METHODS

[0057] The present disclosure proposes a plurality of test sequences performed on a rotating electrical machine so as not only to identify the presence of defects in winding phases of the machine, or in different parts of the insulation provided for this machine, but also to determine the most precisely where these defects are located, so as to allow for the implementation of maintenance operations on the electrical machine. By convention, the term "test" hereafter refers to the application of a "surge test" or "PDIV" type test to a given configuration of the electrical machine, these tests being shown in Figures 1a-1e, 2a-2b, 6a-6b and 10a-10b. Furthermore, the term "test sequence" refers to a procedure, comprising some of the aforementioned tests, such as the procedures illustrated in Figures 3-5, 7-9 and 11-13.

[0058] The test sequences used differ depending on the area of ​​the electrical machine where the fault is located and on the machine's configuration—in particular, on the manufacturing stage of the machine. If there is no information whatsoever on the location of such faults, several of the proposed test sequences can be implemented to locate the fault(s) as accurately as possible.

[0059] The proposed test sequences can be applied to electrical machines powered by electronic converters and controlled by pulse-width modulation (PWM). However, they can also be applied to any other type of rotating electrical machine, including those intended to be directly powered by a grid, as well as to any other electrical component with a winding, for example, a transformer. Depending on the topology, several types of winding can be used: toothed, distributed, concentric, arranged, loose, etc. The proposed test sequences are of particular interest in the case of a loose winding, because the random distribution of conductors in the stator increases the probability of having areas of high electric field concentration, and consequently the risk of partial discharges.

[0060] Commercially available measuring devices widely used in industry can be used to perform all the tests described below. These include devices specifically designed for testing rotating electrical machine stators, which incorporate multi-phase connections with automatic switching, making it easier to perform all the measurements in an automated and sequential manner.

[0061] Regarding PDIV type tests, the devices which enable them to be carried out are equipped with partial discharge sensors which meet the requirements of the IEC60270 standard for measurements under sinusoidal voltage at the network frequency, and the IEC / TS 61934 and IEC60034-18-41 standards for measurements under pulsed voltage.

[0062] The test configurations illustrated in the figures and described below relate to a three-phase wound electric machine. However, as will be understood Easily, this disclosure applies to any electrical machine comprising at least two winding phases.

[0063] Test sequences 100 to 300 - neutral point accessible and single phase. First test sequence 100

[0064] With reference to [Fig. 1a], the configuration 1a, which is known per se and is used in some of the test sequences proposed below, is a PDIV-type test. This test is performed on a rotating electrical machine after the first stage of its manufacture, when the different phases Al, Bl, Cl of the winding have not yet been connected together. This test aims to obtain a partial discharge onset voltage PDIVia, which corresponds to a voltage at which partial discharges of an intensity greater than a predefined threshold are observed in the tested winding phase Al. The test comprises applying the same potential (denoted "HV" in the figures) to a first free end al1 and to a second free end al2 of the winding phase Al.As shown, the second free end al2 is intended to be connected to the second free ends b12, cl2 of the other winding phases Bl, Cl during the second phase of manufacturing the electrical machine. The frame D of the rotating machine is grounded (marked "GND" in the figures), while the untested winding phases (here, Bl and Cl) are floating, that is to say they are not connected to phase Al, nor to the equipment used to apply a potential to the free ends ail, al2 of phase Al, nor to ground.

[0065] The applied potential is increased gradually as long as no partial discharge observed in the tested winding phase Al shows a charge greater than the predefined threshold.

[0066] With reference to [Fig. 2a], configuration lia is another test implemented in the proposed test sequences. It is similar to a surge test. Pulses at a high potential, i.e., at least higher than the nominal voltage at which phase Al normally operates, are applied to the first free end a1 of the first winding phase Al, while keeping the second free end a12 of the first winding phase Al grounded. The value of the potential applied to the first free end a1 is gradually increased until partial discharges with an amplitude exceeding a predefined threshold are observed in the tested winding phase Al. When this threshold is reached, the potential applied to the first end a1 is the partial discharge onset voltage PDIVlla.

[0067] Figure 2b illustrates a configuration IIb, which is identical to the configuration lia except that the first free end al1 is held to ground, while the increasing potential pulses are applied to the second free end al2. potential applied to the second free end al2 when partial discharges of amplitude greater than the predefined threshold appear in the phase Al of the tested winding is the partial discharge appearance voltage PDIVllb.

[0068] The first proposed test sequence 100, shown in [Fig. 3], comprises obtaining 101 the partial discharge onset voltages PDIVua and PDIVub by testing the configurations lia and Ilb mentioned above, which include applying pulses of increasing voltage until the voltages PDIVlla and PDIVllb are determined. Then, a comparison 102 of these two voltages is performed. This comparison will subsequently be used to determine the position of a fault in the winding phase Al.

[0069] The first test sequence 100 is implemented when a fault is known to exist in at least one turn of the AL winding phase. It aims to locate the fault(s) between turns within the AL phase.

[0070] In the simplest embodiment of the first test sequence 100, the comparison step 102 is followed: - if PDIVua > PDIViii, then a fault is located in one or more turns situated in the half of the winding phase Al closest to the second free end al2. Indeed, when pulses are applied for configuration Ilb, within phase Al, the second free end a12 has a maximum potential while the first free end ail has zero potential. Conversely, when pulses are applied for configuration lia, the second free end al2 has zero potential while the first free end ail has a maximum potential. Thus, if a fault exists near the second end a12, partial discharges of a given amplitude will appear at a lower voltage for configuration Ilb than for configuration lia. - if PDIVlla and PDIVllb are substantially equal, from a determination 103 that a fault is located in a central portion of the phase Al, such a zone having a similar potential for the configuration lia and for the configuration Ilb. By "central portion", or alternatively "central half", is meant, here and in the rest of this application, a portion of the winding phase Al extending over 50% of a length of the winding phase Al and being centered on a midpoint of the winding phase, such that the respective ends of the central portion are respectively at the same distance from the two free ends ail, al2 of the phase Al, - if PDIVlla < PDIVllb, from a determination 103 that a fault is located in one or more turns situated in the half of the winding phase Al the most close to the first free end al 1, the reasoning being the same as for the case PDIVlla > PDIVllb.

[0071] Naturally, the first test sequence 100 can be applied to phase B1 and / or Cl, or successively to the three phases Al, B1, Cl, in order to identify and locate defects in these winding phases. Second test sequence 200

[0072] A second test sequence 200, illustrated in [Fig. 4], performs tests on configuration 1a and at least one, possibly both, configurations 1a and 11b. This second test sequence 200 is performed when it is known that at least one fault exists in the insulation between the winding phase 1a and the frame D of the rotating machine. Its purpose is to locate the fault(s) in this insulation.

[0073] The second test sequence 200 includes a first test step 201 of configuration 1a, which is a PDIV-type test with the application of an increasing and identical potential to the two free ends 1a1, 1a2 of phase 1a1, while the frame D is held to ground, allowing the partial discharge onset voltage 1a to be obtained. The second test sequence 200 also includes a second surge test step 202 of configuration 1a1 and / or configuration 11b, allowing the partial discharge onset voltage PDIV11a and / or partial discharge onset voltage PDIV11b to be obtained. The order of execution of the first step 201 and the second step 202 is not important.

[0074] The second test sequence then includes a comparison step 203 of the voltage PDIVia with the voltage PDIVua and / or with the voltage PDIVub.

[0075] In the simplest embodiment of the second test sequence 200, the comparison step 203 is followed: - if the voltages PDIVia and PDIVua are substantially equal, but the voltages PDIVla and PDIVllb differ, according to a predefined criterion, by a determination 204 that a fault is located in one half of the insulation between the phase Al and the carcass D located closest to the first free end al 1. Indeed, when a fault is located in this area, it is more likely to initiate partial discharges for both configurations la and lia, the maximum potential being in both cases assigned to the first free end ail, - if the voltages PDIVia and PDIVub are substantially equal, but the voltages PDIVla and PDIVlla differ, according to a predefined criterion, by a determination of 204, a fault is located in one half of the insulation between the phase A1 and the carbide D located closest to the second free end al2. Indeed, when a fault is located in this area, it is more likely to initiate partial discharges for both configurations a and Ilb, the maximum potential being in both cases assigned to the second free end a 12, - if the voltages PDIVlla and PDIVllb are both substantially equal to the voltage PDIVia, from a determination 204 that a fault between the phase Al and the frame cannot be located precisely: it may be near either of the ends ail, al2 or at the center of the phase Al.

[0076] The predefined criterion for evaluating whether two voltages differ (or, conversely, whether two voltages are substantially equal, as denoted by the symbol "") can take any form conceivable by a person skilled in the art. For example, it can be defined that PDIV11a must, in order to characterize that PDIV11a and PDIV1a differ, be less than a minimum percentage of PDIV1a or greater than a maximum percentage of PDIV1a; for example, less than 85% of PDIV1a or greater than 115% of PDIV1a; or again, less than 90% of PDIV1a or greater than 110% of PDIV1a. Otherwise, these two voltages are considered to be substantially equal.

[0077] Naturally, the second test sequence 200 can be applied to the insulation between phase B1 and the casing, and / or to the insulation between phase Cl and casing D, or even to each of the insulations between a respective phase Al, B1, Cl and the casing, so as to identify and locate defects in these insulations. Third test sequence 300

[0078] A third test sequence 300, illustrated in [Fig. 5], combines steps from the first and second sequences 100, 200 to define a more general test for locating a fault, based on the configurations la, lia and Ilb. The third test sequence 300 has the advantage of not requiring knowledge of the general location of the fault (i.e., whether it is located in the winding phase Al or in the insulation between this phase Al and the frame D of the rotating machine).

[0079] The third test sequence 300 includes a step 301 for testing configuration 1a, by applying an increasing potential to the two free ends 1ail, 1a1 of the winding phase 1a1 until the partial discharge voltage PDIV1 is identified. The third test sequence 300 also includes a test step 302 for configurations 1a1, 1b1, in the same manner as for test sequences 100, 200. The order in which the three configurations 1a, 1a1, and 1b1 are tested is not important.

[0080] Subsequent to test steps 301, 302, the third test sequence 300 includes a step 303 for comparing the discharge onset voltages partial measurements were obtained, including a comparison of the PDIVla voltage with the PDIVua voltage, and a comparison of the PDIVia voltage with the PDIVub voltage. The order in which these two comparisons are performed is not important.

[0081] Once the comparisons 303 have been performed, the third test sequence 300 includes a step 304 for determining the overall location of a fault, making it possible to determine whether the fault is located within the winding phase Al (i.e., between turns of the Al phase) or in the insulation between the Al phase and the frame D. The determination step 304 may determine that PDIVlla < PDIVla and PDIVub < PDIVia. In this case, the application of high-potential pulses for testing the configurations lia, Ilb resulted in partial discharges at lower voltages than in the case 1a, which highlights the existence of inter-turn faults within the winding phase Al itself. Conversely, the determination step 304 may determine that one of the voltages PDIVlla and PDIVllb is greater than the voltage PDIVla.In this case, the Al phase, when it is stressed alone (configurations lia, Ilb) only sees the appearance of partial discharges for higher voltages compared with the case where the insulation between the Al phase and the frame D is also electrically stressed (configuration la), which highlights the existence of defects in the insulation between the winding phase Al and the frame D.

[0082] The third test sequence 300, in its simplest embodiment, only includes the configuration test steps 301, 302, comparison of partial discharge onset voltages 303 and determination 304. It then makes it possible to determine whether a fault is located in the winding phase Al or in the insulation between this phase Al and the frame D.

[0083] According to other embodiments, the third test sequence includes steps subsequent to comparison 303, so as to determine the location of the defect more precisely. Thus, in the third test sequence 300 and at the end of the determination step 304, two scenarios are distinguished.

[0084] First, when PDIVua < PDIVia and PDIVub < PDIVia, which indicates an inter-turn fault in phase A1, the test sequence 300 includes a step 305 comparing the voltages PDIVlla and PDIVllb, followed by a step 306 determining the location of the fault. Identical to the first test sequence 100: - when PDIVua < PDIVub, the determination step 306 determines that the defect is located in the half of the phase Al closest to the first free end al 1; - when PDIVlla ~ PDIVllb the determination step 306 determines that the defect is located in the central portion of phase Al; - when PDIVua > PDIVub, the determination step 306 determines that the defect is located in the half of the Al phase closest to the second free end a 12.

[0085] Secondly, when either PDIVlla or PDIVllb is equal to or greater than PDIVla, indicating a fault in the insulation between the winding phase A1 and the frame D, the test sequence does not include steps 305 and 306, but does include a step 307 for determining the location of the fault. This is identical to the second test sequence 200: - when PDIVia ~ PDIVuamais than PDIVia PDIVub according to a predefined criterion (for example, a minimum and maximum percentage), the determination step 307 determines that the defect is located in half of the insulation between the phase Al and the frame D located closest to the first free end ail, - when PDIVla ~ PDIVllb but that PDIVla PDIVlla according to a predefined criterion (for example, a minimum and maximum percentage), the determination step 307 determines that the defect is located in one half of the insulation between the phase Al and the carcass D located closest to the second free end a 12, - when the voltages PDIVlla and PDIVllb are both substantially equal to the voltage PDIVia, the determination step 307 determines that the fault between phase Al and the frame cannot be located precisely.

[0086] Thus, in comparison with the prior art tests, which only allow the existence of a defect to be determined in the rotating machine, the proposed third test sequence 300, in embodiments comprising steps 305, 306 or 307, allows the existence of a defect and the precise location of this defect to be determined in the rotating machine.

[0087] Test sequences 400 to 600 - neutral point reachable and two phases. Fourth test sequence 400

[0088] With reference to [Fig. 1b], the configuration Ib, which is known in itself but is used in some of the test sequences proposed below, is a PDIV-type test. This test is performed on a rotating electrical machine at the end of an initial phase of its manufacture, when the different phases Al, B1, Cl of the winding have not yet been connected together. This test aims to obtain a partial discharge onset voltage PDIVib, which corresponds to a voltage at which partial discharges of an amplitude are observed in the electrical machine. above a predefined threshold. The test involves applying the same potential to the first free end ail and the second free end al2 of the winding phase Al. The frame D of the rotating machine is floating, meaning it is not connected to phase Al or to the equipment used to apply a potential to the free ends al1, al2 of the winding phase AL. A second phase (here, phase Bl) is connected to ground. The last phase (here, phase Cl) is also floating.

[0089] The applied potential is increased gradually as long as no partial discharge observed in the tested winding phase Al shows a charge greater than the predefined threshold.

[0090] With reference to [Fig. 6a], configuration Ilia is another test implemented in the proposed test sequences. It is similar to a surge test. Pulses at a high potential, i.e., at least higher than the nominal voltage at which phase Al normally operates, are applied to the first free end al2 of the first winding phase Al, while keeping the second free end al2 of the first winding phase Al and the two ends b11, b12 of the second winding phase Bl grounded. The value of the potential applied to the first free end al1 is gradually increased until partial discharges occur with a current intensity exceeding a predefined threshold. When this threshold is reached, the potential applied to the first end al1 is the partial discharge onset voltage PDIVlla.

[0091] Figure 6b illustrates the configuration IIlb, which is identical to the configuration Ilia except that the first free end al1 is held to ground, while pulses of increasing potential are applied to the second free end al2. The potential applied to the second free end al2 when partial discharges of charge above the predefined threshold appear in the tested winding phase Al is the partial discharge onset voltage PDIVmb.

[0092] The proposed fourth test sequence 400, illustrated in [Fig. 7], comprises obtaining 401 the partial discharge onset voltages PDIV11a and PDIV11b by testing the configurations IIa and IIb mentioned above, which include applying pulses of increasing voltage until the voltages PDIV11a and PDIV1b are determined. Then, a comparison 402 of these two voltages is performed so as to determine the position of a fault in the winding phase AL

[0093] The first test sequence 400 is implemented when a fault is known to exist in at least one turn of the AL winding phase. It aims to locate the fault(s) within the AL phase.

[0094] In the simplest embodiment of the first test sequence 400, the comparison step 402 is followed: - if PDIVllla > PDIVlllb, a determination of 403 indicates that a fault is located in one or more turns situated in the half of the winding phase Al closest to the second free end al2. Indeed, when pulses are applied for the configuration Illb, within the phase Al, the second free end a12 has a maximum potential while the first free end ail has zero potential. Conversely, when pulses are applied for the configuration Ilia, the second free end al2 has zero potential while the first free end ail has a maximum potential. Thus, if a fault exists near the second end a12, partial discharges of a given amplitude will appear at a lower voltage for the configuration Illb than for the configuration Ilia. - if PDIVma and PDIVia are substantially equal, with a determination of 403 that a defect is located in a central portion of the Al phase, such a zone having a similar potential for the Ilia configuration and for the Illb configuration, - if PDIVllla < PDIVlllb, from a determination 403 that a fault is located in one or more turns located in the half of the winding phase Al closest to the first free end al 1, the reasoning being the same as for the case PDIVma > PDIVmb.

[0095] Naturally, the fourth test sequence 400 can be applied by defining any one of the winding phases Al, B1, or Cl as the phase to which a potential is applied, and any other phase can be the grounded phase. The fourth test sequence 400 can also be applied successively to the three phases Al, B1, and Cl in order to identify and locate faults in these winding phases. Fifth sequence of tests 500

[0096] A proposed fifth test sequence 500, illustrated in [Fig. 8], performs tests on configuration Ib and at least one, or possibly both, configurations Ilia and Illb. This fifth test sequence 500 is performed when at least one fault is known to exist in the insulation between a first winding phase (phase Al in Figures 6a-6b) and a second winding phase (phase B1 in Figures 6a-6b). Its purpose is to locate the fault(s) in this insulation.

[0097] The fifth test sequence 500 includes a first step 501 of testing the configuration Ib, which is a PDIV-type test with the application of a potential The voltage is increasing and identical at both free ends ail, al2 of phase A1, while phase B1 is held to ground and frame D is floating, allowing the partial discharge onset voltage Ib to be obtained. The fifth test sequence 500 also includes a second "surge test" step 502 of the configuration Ilia and / or the configuration Illb, allowing the partial discharge onset voltage PDIVlla and / or the partial discharge onset voltage PDIVmb to be obtained. The order of execution of the first step 501 and the second step 502 is not important.

[0098] The fifth test sequence 500 then includes a comparison step 503 of the voltage PDIVlb with the voltage PDIVllla and / or with the voltage PDIVlllb.

[0099] In the simplest embodiment of the fifth test sequence 500, the comparison step 503 is followed: - if the voltages PDIVib and PDIVma are substantially equal, but the voltages PDIVlb and PDIVlllb differ, according to a predefined criterion, by a determination of 504, a fault is located in one half of the insulation between phase A1 and phase B1 located closest to the first free end ail. Indeed, when a fault is located in this area, it is more likely to initiate partial discharges for both configurations Ib and Ilia, the maximum potential being in both cases allocated to the first free end ail, - if the voltages PDIVlb and PDIVlllb are substantially equal, but the voltages PDIVib and PDIVma differ, according to a predefined criterion, a determination 504 that a fault is located in one half of the insulation between phase A1 and phase B1 located closest to the second free end A12. Indeed, when a fault is located in this area, it is more likely to initiate partial discharges for both configurations Ib and IIlb, the maximum potential being in both cases assigned to the second free end A12, - if the voltages PDIVllla and PDIVlllb are both substantially equal to the voltage PDIVib, a determination 504 that a fault is located between phases Al and Bl, but without the possibility of precisely locating the fault - in a manner analogous to the comparison step 203 of the second test sequence 200.

[0100] Naturally, the fifth test sequence 500 can be applied to the insulation between phase B1 and phase Al, and / or to the insulation between phase Bl and phase Cl, or to each of the insulations between two phases Al, B1, Cl so as to identify and locate defects in these insulations. Sixth test sequence 600

[0101] A sixth test sequence 600, illustrated in [Fig. 9], combines steps from the fourth and fifth sequences 400, 500 so as to define a more general test for locating a fault, based on the configurations Ib, Ilia and Illb. The sixth test sequence 600 has the advantage of not requiring knowledge of the general location of the fault (i.e., whether it is located in the winding phase Al or in the insulation between this phase Al and another winding phase Bl).

[0102] The sixth test sequence 600 includes a test step 601 of configuration Ib, by applying an increasing potential to the two free ends ail, al2 of the winding phase Al until the partial discharge onset voltage PDIVib is identified. The sixth test sequence 600 also includes a test step 602 of configurations Ilia, Illb, in the same manner as for test sequences 400, 500. The order in which the three configurations Ib, Ilia, and Illb are tested is not important.

[0103] Subsequent to test steps 601, 602, the sixth test sequence 600 includes a step 603 for comparing the partial discharge onset voltages obtained, comprising a comparison of the voltage PDIVlb with the voltage PDIVma, and a comparison of the voltage PDIVia with the voltage PDIVmb. The order in which these two comparisons are performed is not important.

[0104] Once the comparisons 603 have been performed, the sixth test sequence 600 includes a step 604 for determining the overall location of a fault, making it possible to determine whether the fault is located within the winding phase Al (i.e., in turns of the Al phase) or in the insulation between the Al phase and the BL phase. The determination step 604 can determine that PDIVma < PDIVib and PDIVmb < PDIVib. In this case, the application of high-potential pulses for testing configurations Ilia and Illb resulted in partial discharges at lower voltages than in the Ib case, highlighting the existence of inter-turn faults within the winding phase Al itself. Conversely, the determination step 604 can determine that one of the voltages PDIVlla and PDIVlllb is greater than the voltage PDIVib.In this case, the Al phase, when it is stressed alone (configurations Ilia, Illb) only sees the appearance of partial discharges for higher voltages than when the insulation between the Al phase and the Bl phase is also electrically stressed (configuration Ib), which highlights the existence of faults in the insulation between the winding phase Al and the winding phase BL.

[0105] The sixth test sequence 600, in its simplest embodiment, comprises only the configuration test steps 601, 602, and the voltage comparison steps of the appearance of partial discharges 603 and of determination 604. It then allows to determine if a fault is in the winding phase Al or in the insulation between this phase Al and the phase B1.

[0106] According to other embodiments, the sixth test sequence 600 includes steps subsequent to the comparison 603, so as to determine the location of the defect more precisely. Thus, in the sixth test sequence 600 and at the end of the determination step 604, two scenarios are distinguished.

[0107] First, when PDIVlla < PDIVlb and PDIVlllb < PDIVlb, which indicates an inter-turn fault in phase A1, test sequence 600 includes a step 605 comparing the voltages PDIVma and PDIVmb, followed by a step 606 determining the location of the fault. Identical to the fourth test sequence 400: - when PDIVllla < PDIVlllb, the determination step 606 determines that the defect is located in the half of phase Al closest to the first free end al 1; - when PDIVma ~ PDIVmb the determination step 606 determines that the defect is located in the central portion of the Al phase; - when PDIVllla > PDIVlllb, the determination step 606 determines that the defect is located in the half of phase Al closest to the second free end a 12.

[0108] Secondly, when either PDIVlla or PDIVlllb is equal to or greater than PDIVlb, indicating a fault in the insulation between the winding phase A1 and the phase B1, the test sequence does not include steps 605 and 606, but does include a step 607 for determining the location of the fault. This is identical to the fifth test sequence 500: - when PDIVib ~ PDIVma but that PDIVib PDIVmb according to a predefined criterion (for example a minimum and maximum percentage), the determination step 607 determines that the defect is located in the half of the insulation between the Al phase and the Bl phase located closest to the first free end ail, - when PDIVlb ~ PDIVlllb but that PDIVlb PDIVllla according to a predefined criterion (for example, a minimum and maximum percentage), the determination step 607 determines that the defect is located in one half of the insulation between the Al phase and the Bl phase located closest to the second free end a 12, - when the voltages PDIVma and PDIVmb are both substantially equal to the voltage PDIVlb, the determination step 607 determines that the The fault is located between phases Al and Bl, but it is not possible to precisely locate the fault.

[0109] Thus, in comparison with prior art tests, which only allow the existence of a defect to be determined in the rotating machine, the proposed sixth test sequence 600, in embodiments comprising steps 605, 606 or 607, allows the existence of a defect and the precise location of this defect to be determined in the rotating machine.

[0110] It is also possible to implement successively the third test sequence 300 and the sixth test sequence 600, so as to test both the insulation between phases Al, Bl, Cl and the frame D and the insulation between two respective phases Al, B1, Cl.

[0111] Test sequences 700 to 900 - neutral point not accessible

[0112] This disclosure also proposes several test sequences that can be performed, also with the aim of identifying the presence of a defect that could lead to the generation of partial discharges in a rotating electrical machine, at the end of a second phase of manufacturing the machine, when the phases Al, B1, Cl of the machine winding have been connected to their respective second ends al2, b12, cl2.

[0113] At the end of the second manufacturing phase, it is impossible to carry out tests by applying a potential to the two free ends of a single phase Al, B1, Cl, or to apply a voltage to these two ends - indeed, the second ends al2, b12, cl2 are no longer free but connected to each other so as to form the neutral point N. However, it remains possible to carry out tests by applying a potential to the first ends al1, bl1 and cl1 of two separate phases.

[0114] With reference to [Fig. 1e], the test of configuration 1e is known from the prior art, but is also implemented in some test sequences proposed here. Each phase Al, B1, Cl has a respective first free end ail, b1ll, cil. The phases Al, B1, and Cl are connected to each other at a neutral point N, opposite the first ends ail, b1ll, and cil. In the first configuration 1e, the same potential is applied to the first three free ends ail, b1ll, cil while the frame D is held to ground. This test is of the PDIV type, that is, it consists of applying an increasing potential to the first free ends ail, b1ll, cl1 until partial discharges of charge exceeding a predefined threshold are observed. When such partial discharges are observed, the applied potential is the partial discharge onset voltage PDIV1C.

[0115] With reference to [Fig. 10a], configuration IVa is another test implemented in the proposed test sequences. This test is a "surge test" and consists of Apply pulses at a high potential—that is, at least higher than the rated voltage of the rotating machine—increasingly to the first free end ail of phase A1, while keeping the first free end of another phase (here, the first free end bl1 of phase B1) grounded. The pulse potential is increased until partial discharges with a current exceeding a predefined threshold are observed. The potential value at the onset of the first partial discharges with a current exceeding the predefined threshold is the partial discharge onset voltage PDIVlva.

[0116] Figure 10b illustrates configuration IVb, which is identical to configuration IVa except that the high potential is applied to the first free end bl1 of phase Bl, while the first free end ail of phase Al is held to ground. The potential applied to the first free end bl1 of phase Bl when partial discharges of intensity greater than the predefined threshold appear in the electrical machine is the partial discharge onset voltage PDIVivb-Seventh Test Sequence 700

[0117] The proposed seventh test sequence 700, illustrated in [Fig. 11], includes obtaining 701 the partial discharge onset voltages PDIViva and PDIVivb by testing the configurations IVa and IVb mentioned above, which include applying pulses of increasing voltage until the voltages PDIViva and PDIVivb are determined. Then, a comparison 702 of these two voltages is carried out so as to determine the position of a fault in one of the winding phases Al, BL.

[0118] The seventh test sequence 700 is implemented when it is known that a fault exists in at least one turn of the winding phase Al and / or in at least one turn of the winding phase BL. It aims to locate the fault(s) within these phases.

[0119] In the simplest embodiment of the seventh test sequence 700, the comparison step 702 is followed: - if PDIV1Va > PDIVIvb, a determination of 703 indicates that a fault is located in one or more turns situated in the BL winding phase. Indeed, when pulses are applied for configuration IVb, the first free end bl1 of phase B1 has a maximum potential, while the first free end a1 of phase A1 has a zero potential. Conversely, when pulses are applied for configuration IVa, the first free end bl1 of phase B1 has a zero potential, while the first free end a1 of phase A1 has a maximum potential. Thus, if there is a fault near the first free end bl1 of phase B1—in other words, in phase B1—partial discharges of a given intensity will occur. will appear at a lower voltage for configuration IVb than for configuration IVa. - if PDIV1Va ~ PDIV1Vb, from a determination 703 that a fault is located in one or more turns located in one or the other of the phases Al, Bl, and necessarily in a zone of these phases close to the neutral point N, such a zone having a potential close for the configuration IVa and for the configuration IVb. - if PDIViva < PDIVivb, from a determination 703 that a fault is located in one or more turns situated in the winding phase Al, the reasoning being the same as for the case PDIVlva > PDIV1Vb-

[0120] Naturally, the seventh test sequence 700 can be applied to both phases B1 and Cl, or to both phases Al and Cl, or successively to all possible combinations of two winding phases Al, Bl, Cl so as to identify and locate defects in these winding phases. Eighth test sequence 800

[0121] An eighth test sequence 800, illustrated in [Fig. 12], performs tests on configuration i and at least one, possibly both, configurations IVa and IVb. The eighth test sequence 800 is performed when it is known that at least one fault exists in the insulation between one of the two winding phases (in the example below, in one of the phases A1 and B1) and the frame D of the rotating machine – although it may possibly be a fault located in turns of one of the phases A1, B1. It aims to locate the fault(s) in this insulation.

[0122] The eighth test sequence 800 includes a first test step 801 of configuration le, which is a PDIV-type test with the application of an increasing and identical potential to the first free ends al1, bl1, and cl1 of each of the phases Al, Bl, and Cl, while the frame D is held to ground, allowing the partial discharge onset voltage le to be obtained. The eighth test sequence 800 also includes a second surge test step 802 of configuration IVa and / or configuration IVb, allowing the partial discharge onset voltage PDIViVa and / or partial discharge onset voltage PDIV1Vb to be obtained. The order of implementation of the first step 801 and the second step 802 is not important.

[0123] The second test sequence then includes a comparison step 803 of the voltage PDIVic with the voltage PDIViVa and / or with the voltage PDIVivb-

[0124] In the simplest embodiment of the eighth test sequence 800, the comparison step 803 is followed: - if the voltages PDIV1C and PDIV1Va are substantially equal, from a determination of 804 that the fault is located in the insulation between phases A1 and B1 and the frame D, at a point closer to the first end A1 than to the first end B1. In other words, the fault is located in the insulation between phase A1 and the frame D. Indeed, the voltage PDIVic corresponds to a fault in the insulation between one of the phases A1, B1, or B1 and the frame D, with no potential difference present between or within the phases, while a potential difference does exist between the phases and the frame D. When the voltage PDIV1Va is substantially equal to PDIVic, the same fault has resulted in the generation of partial discharges at the same potential applied to the first free end A1, - if the voltages PDIV1C and PDIV1Vb are substantially equal, from a determination of 804 that the fault is located in the insulation between phases Al and Bl and the frame D, at a point closer to the first end bl 1 than to the first end al 1. In other words, the fault is located in the insulation between phase B1 and the frame D. Indeed, the voltage PDIV1C corresponds to a fault in the insulation between one of the phases Al, Bl, Cl and the frame D, with no potential difference present between or within the phases, while a potential difference does exist between the phases and the frame D. When the voltage PDIVivb is substantially equal to PDIV1C, the same fault has resulted in the generation of partial discharges at the same potential applied to the first free end bl 1, - if the voltage PDIViVa is greater than the voltage PDIVic or if the voltage PDIV1Vb is greater than the voltage PDIV1C a determination 804 that a fault is located in the insulation between the phase Al and the frame D or in the insulation between the phase B1 and the frame D, but without the possibility of precisely locating this fault, and in particular of determining which of the phases Al, Bl is concerned.

[0125] Naturally, the eighth test sequence 800 can be applied to the insulation between the phases Bl, Cl and the frame D, and / or to the insulation between the phases Al, Cl and the frame D, or successively to the insulation between the frame D on the one hand and any conceivable combination of two phases Al, Bl, Cl, so as to identify and locate defects in these insulations. Ninth test sequence 900

[0126] A proposed ninth test sequence 900, illustrated in [Fig. 13], combines steps from the seventh and eighth sequences 700, 800 so as to define a more general test for locating a fault, based on configurations i, IVa and IVb. The ninth test sequence 900 has the advantage of not requiring knowledge of the general location of the fault (i.e., whether it is located in one of the phases Al, Bl, Cl or in the insulation between one of these phases and the frame D of the rotating machine).

[0127] The ninth test sequence 900 includes a test step 901 of configuration i1, by applying an increasing potential to the first free ends a1, bl1, c11 of the winding phases A1, B1, C1 until the partial discharge onset voltage PDIV1C is identified. The ninth test sequence 900 also includes a test step 902 of configurations IVa, IVb, in the same manner as for test sequences 700, 800. The order in which the three configurations i1, IVa and IVb are tested is not important.

[0128] Subsequent to test steps 901, 902, the ninth test sequence 900 includes a step 903 of comparison of the partial discharge onset voltages obtained, including a comparison of the voltage PDIVic with the voltage PDIV1Va, and a comparison of the voltage PDIV1C with the voltage PDIV1Vb- The order in which these two comparisons are carried out is not important.

[0129] Once the comparisons 903 have been performed, the third test sequence 900 includes a step 904 for determining the overall location of a fault, making it possible to determine whether the fault is located within one of the two winding phases Al, Bl (i.e., between the turns of one of these phases) or in the insulation between these phases Al, B1 and the frame D. The determination step 904 can establish that PDIViVa < PDIVic and PDIViVb < PDIVic. In this case, the application of high-potential pulses for the tests of configurations IVa, IVb resulted in partial discharges at lower voltages than in case i, which highlights the existence of between-turn faults in one of the winding phases Al, BL

[0130] The determination step 904 can also determine that one of the voltages PDIV1Va and PDIV1Vb is strictly greater than the voltage PDIV1C. In this case, the fault is determined to be located in the insulation between phase Al and frame D and / or in the insulation between phase Bl and frame D. Indeed, the fact that partial discharges occur, for one of the configurations IVa, IVb, only at higher voltages than for configuration i highlights the fact that no fault is present in the phases Al, Bl themselves.

[0131] Finally, the determination step 904 may determine that one of the voltages PDIV1Va and PDIVivb is equal to the voltage PDIVic, in which case it is impossible to deduce with certainty a location of the fault(s).

[0132] The ninth test sequence 900, in its simplest embodiment, only includes the configuration test steps 901, 902 and the comparison of partial discharge onset voltages 903. It then makes it possible to determine whether a fault is located in one of the winding phases Al, Bl or in the insulation between these phases Al, B1 and the frame D.

[0133] According to other embodiments, the ninth test sequence 900 includes steps subsequent to the comparison 903, so as to determine the location of the defect more precisely. Thus, in the ninth test sequence 900 and at the end of the determination step 904, two scenarios are distinguished.

[0134] First, when PDIV1Va < PDIV1C and PDIV1Vb < PDIV1C, which indicates a fault between turns in one of the phases A1, B1, the test sequence 900 includes a step 905 comparing the voltages PDIV1Va and PDIV1Vb, followed by a step 906 determining the location of the fault. Identical to the seventh test sequence 700: - when PDIV1Va < PDIV1Vb, the determination step 906 determines that the fault is located in the Al phase; - when PDIViVa ~ PDIVivb the determination step 906 determines that the fault is located in the central portion of the set formed by the phases Al, Bl, that is to say near the neutral point N, in one or the other of the phases Al, Bl; - when PDIV1Va > PDIV1Vb, the determination step 906 determines that the fault is located in the Bl phase.

[0135] Secondly, when either PDIV1Va or PDIV1Vb is equal to or greater than PDIV1C, the test sequence does not include steps 905 and 906, but does include a step 907 for determining the location of the fault. This is identical to the eighth test sequence 800: - when PDIVic ~ PDIViVa, the determination step 907 determines that the fault is either located in the insulation between the phase Al and the frame D, or located between turns in one of the phases Al, Bl. Unlike the eighth sequence, which is initiated when it is already known that the fault is located in the insulation between the phase Al and the frame D, here it is impossible to clearly deduce that the fault is located in the insulation between the phase Al and the frame D, and not between turns of the phases Al or Bl, since the partial discharge onset voltages PDIVlcet PDIV1Va can be identical even though the fault is located between turns of the phases Al or Bl. - when PDIVic ~ PDIVivb, the determination step 907 determines that the fault is either located in the insulation between phase Bl and the casing D, or located in one of the phases Al, Bl. Unlike the eighth sequence, which is initiated when it is already known that the fault is located in the insulation between the phase Al and the frame D, here it is impossible to deduce clearly that the fault is located in the insulation between the phase Bl and the frame D, and not between turns of the phases Al or Bl, since the partial discharge appearance voltages PDIVlcet PDIV1Vb can be identical even though the fault is located between turns of the phases Al or Bl. - When PDIViVa > PDIVicou when PDIVivb > PDIV1C, the determination step 907 determines that the fault is located in the insulation between phase Al and the casing D, or in the insulation between phase B1 and the casing D, without however being able to locate the fault more precisely, and in particular which of the two phases Al, B1 is concerned.

[0136] Thus, in comparison with prior art tests, which only allow the existence of a defect to be determined in the rotating machine, the proposed ninth test sequence 900, in embodiments including steps 905, 906 or 907, allows the existence of a defect and the precise location of this defect to be determined in the rotating machine.

[0137] This application further relates to a fault detection system in a rotating electrical machine, the system being configured to implement the test sequences defined above.

[0138] This application further relates to a computer program product. The program includes code instructions enabling the execution of all verification steps 303, 603, 903 of a condition of the third, sixth and ninth test sequences 300, 600 and 900, as well as the execution of determination steps 304, 604 and 904 of these same sequences.

Claims

1. Demands A method (300) for detecting faults in a rotating electrical machine comprising a first winding phase (Al), a second winding phase (Bl) and a frame (D), the first winding phase (Al) being provided with a first free end (al1) and a second free end (al2), the method comprising the steps of: a. simultaneous application (301) of an increasing electrical potential to the first free end (al 1) and to the second free end (al2), the frame (D) being maintained at a zero electrical potential, so as to identify a reference partial discharge onset voltage (PDIVla) at which partial discharges of an amplitude greater than a reference threshold appear in the electrical machine, b. application (302) of an increasing electrical potential to the first free end (al 1), the second free end (a 12) being maintained at zero electrical potential, so as to identify a first partial discharge appearance voltage (PDIVlla) at which partial discharges of an amplitude greater than a first predefined threshold appear in the first winding phase (Al), c. application (302) of an increasing electrical potential to the second free end (a 12), the first free end (ail) being maintained at zero electrical potential, so as to identify a second partial discharge appearance voltage (PDIVub) at which partial discharges of an intensity greater than a second predefined threshold appear in the first winding phase (Al), d. verification (303) of a condition, the condition being: i. the first partial discharge onset voltage (PDIVlla) is less than the reference partial discharge onset voltage (PDIVIa), and ii. The second partial discharge onset voltage (PDIVllb) is lower than the voltage of occurrence of reference partial discharges (PDIVla), e. if the condition is satisfied, determination (304) that a fault exists in the first winding phase (Al), f. if the condition is not satisfied, determination (304) that a fault exists in an insulation between the first winding phase (Al) and the frame (D) of the rotating electrical machine.

2. Method (300) according to claim 1 comprising, after determining (304) that a defect exists in the first winding phase (Al), determining (306) a position of the defect in the first winding phase (Al) from a comparison (305) between the first partial discharge onset voltage (PDIVlla) and the second partial discharge onset voltage (PDIVllb).

3. A method (300) according to claim 1 comprising, after determining that a defect exists in the insulation between the first winding phase (Al) and the frame (D): - a determination (307) of a position of the defect in the insulation between the first winding phase (Al) of the rotating electrical machine and the electrical frame (D) of the rotating electrical machine, or - a determination (307) that a position of the defect in the insulation between the first winding phase (Al) of the rotating electrical machine and the frame (D) of the rotating electrical machine cannot be identified, the determination (307) being carried out on the basis of a comparison between, on the one hand, the reference partial discharge onset voltage (PDIVla) and, on the other hand, at least one of the first partial discharge onset voltage (PDIVua) and the second partial discharge onset voltage (PDIVub).

4. A method (600) for detecting faults in a rotating electrical machine comprising a first winding phase (Al), a second winding phase (Bl) and a frame (D), the first winding phase (Al) being provided with a first free end (al1) and a second free end (al2), the method comprising steps of: a. simultaneous application (601) of an increasing electrical potential to the first free end (al 1) and to the second free end (al2), the second winding phase (Bl) being maintained at zero electrical potential, so as to identify a reference partial discharge appearance voltage (PDIVib) at which partial discharges of an amplitude greater than a reference threshold appear in the electrical machine, b. application (602) of an increasing electrical potential to the first free end (al 1), the second free end (a 12) and the second phase (Bl) of the winding being maintained at zero electrical potential, so as to identify a first partial discharge appearance voltage (PDIVlla) at which partial discharges of an amplitude greater than a first predefined threshold appear in the electrical machine, c. application (602) of an increasing electrical potential to the second free end (a 12), the first free end (al 1) and the second phase (B 1) of the winding being maintained at zero electrical potential, so as to identify a second partial discharge appearance voltage (PDIVmb) at which partial discharges of an intensity greater than a second predefined threshold appear in the electrical machine, d. verification (603) of a condition, the condition being: i. the first partial discharge onset voltage (PDIV11a) is less than the reference partial discharge onset voltage (PDIVIb), and ii. The second partial discharge onset voltage (PDIVmb) is lower than the reference partial discharge onset voltage (PDIVIb), e. If the condition is met, determination (604) that a fault exists in the first winding phase (A1), f. If the condition is not met, determination (604) that a fault exists in an insulation between the first phase (Al) of winding and the second phase (Bl) of winding.

5. Method (600) according to claim 4 comprising, after determination (604) that a defect exists in the first winding phase (Al), a determination (606) of a position of the defect in the first winding phase (Al) from a comparison (605) between the first partial discharge onset voltage (PDIVuia) and the second partial discharge onset voltage (PDIVlub).

6. A method (600) according to claim 4 comprising, after determining that a fault exists in the insulation between the first winding phase (Al) and the second winding phase (Bl): - a determination (607) of a position of the fault in the insulation between the first winding phase (Al) and the second winding phase (Bl), or - a determination (607) that a position of the fault in the insulation between the first winding phase (Al) and the second winding phase (Bl) cannot be identified, the determination (607) being carried out on the basis of a comparison between, on the one hand, the reference partial discharge onset voltage (PDIVib) and, on the other hand, at least one of the first partial discharge onset voltage (PDIVlla) and the second partial discharge onset voltage (PDIVmb).

7. A method (900) for detecting faults in a rotating electrical machine comprising a first winding phase (Al), a second winding phase (Bl), and a frame (D), the first winding phase (Al) having a free end (Al1) and the second winding phase (Bl) having a free end (Bl1), the first winding phase (Al) and the second winding phase (Bl) further being connected at a neutral point (N), the method comprising steps of: a. simultaneous application (901) of an increasing electrical potential to the free end (Al1) of the first winding phase (Al) and to the free end (Bl1) of the second winding phase (Bl), the frame (D) being held at zero electrical potential, so as to identify a reference partial discharge onset voltage (PDIV1C) at which partial discharges of an intensity greater than a reference threshold appear in the electrical machine, b. application (902) of an increasing electrical potential to the free end (al 1) of the first winding phase (Al), the free end (b 11) of the second winding phase (Bl) being maintained at zero electrical potential, so as to identify a first partial discharge appearance voltage (PDIViVa) at which partial discharges of an intensity greater than a first predefined threshold appear in the electrical machine, c. application (902) of an increasing electrical potential to the free end (b 11) of the second winding phase (Bl), the free end (al 1) of the first winding phase (Al) being maintained at zero electrical potential, so as to identify a second partial discharge appearance voltage (PDIV1Vb) at which partial discharges of an intensity greater than a second predefined threshold appear in the first winding phase (Al), d. verification (903) of a condition, the condition being: • the first partial discharge onset voltage (PDIViVa) is less than the reference partial discharge onset voltage (PDIVIc), and • the second partial discharge onset voltage (PDIV1Vb) is lower than the reference partial discharge onset voltage (PDIVIc), e. if the condition is satisfied, determination (904) that a defect exists in one of the first winding phase (Al) and the second winding phase (Bl), f. if the condition is not met, determination (904) that a defect exists:

8.

9.

10. • in the insulation between, on the one hand, the first winding phase (Al) and the second winding phase (Bl) and, on the other hand, the frame (D), and / or • in one of the first winding phase (Al) and / or the second winding phase (Bl). Method (900) according to claim 7 comprising, after determining (904) that a fault exists in one of the first winding phase (A1) and the second winding phase (B1), determining (906) a position of the fault from a comparison (905) between the first partial discharge onset voltage (PDIViVa) and the second partial discharge onset voltage (PDIV1Vb)- Method (900) according to claim 7 comprising, after determining (904) that a defect exists in the insulation between, on the one hand, one of the first winding phase (Al) and the second winding phase (Bl) and, on the other hand, the casing (D), and / or that a defect exists in one of the first winding phase (Al) and the second winding phase (Bl), a determination (907) of a position of the defect based on a comparison between, on the one hand, the reference partial discharge onset voltage (PDIVic) and, on the other hand, one of the first partial discharge onset voltage (PDIV1Va) and the second partial discharge onset voltage (PDIV1Vb)- Product computer program comprising instructions which, when the program is executed by a computer, lead to the implementation of the verification (303, 603, 903) and determination (304, 604, 904) steps of the process according to any one of claims 1 to 9.

Images