• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
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  • 优先权
    • 专利摘要:
    System and method for locating earth faults in electrical windings. Method and system for locating earth faults in electrical windings based on the analysis of the frequency response of the electrical winding feeding in the forward and reverse directions and subsequent treatment of the resonance frequencies of the system (fR1 and fR2) in a device that compares these with a database of curves from previous tests and that allows locating the fault in fault loop number (n) and fault resistance (Rf). (Machine-translation by Google Translate, not legally binding)
    公开号:ES2784533A1
    申请号:ES202030371
    申请日:2020-04-30
    公开日:2020-09-28
    发明作者:Granados Jose Manuel Guerrero；Santos Carolina Martin；Mourelo Pablo Gomez；Gaona Carlos Antonio Platero
    申请人:Universidad Politecnica de Madrid；
    IPC主号:
    专利说明:

    [0004] OBJECT OF THE INVENTION
    [0006] The present invention refers to a system and method for locating ground faults in electrical windings capable of locating this type of fault at any point in the electrical circuit, when the electrical circuit is disconnected from the electrical network.
    [0008] The system and method for locating ground faults in electrical windings according to the present invention is useful in the offline maintenance of electrical machines due to its ability to locate ground faults and determine the resistance of the fault. The present invention has application, for example and without limitation, in the electricity generation sector.
    [0010] BACKGROUND OF THE INVENTION
    [0012] The diagnosis of electrical systems is essential for the correct operation, maintenance and repair of electrical machines.
    [0014] Electrical windings are present in most electrical machines. In the field of generation, high-power machines can have two-phase or three-phase earth faults that reduce the useful life of the same to the point of disabling it.
    [0016] Synchronous, asynchronous and transformer machine protection equipment is of great importance. There are many types of protections against faults in stator, rotor, eccentricity, etc ... This is not the case in the case of detection and location of the defects discussed here.
    [0017] One of the most common faults in electrical windings of any type of machine is earth faults. Characterized by closing a circuit between a live conductor and ground. This circuit creates a bypass current or residual current that returns through a second grounded point such as a rigid grounded system (TT), an impedance grounded system (IT) or a second fault to land, if any.
    [0019] In the event that an earth fault occurs, the leakage current depends on the fault resistance. At higher fault resistance, such as slightly deteriorated insulation, the fault current will be low. However, if the fault resistance is low, a high current single-phase short circuit to ground may result.
    [0021] For electrical windings of electrical machines, in their detection systems against ground faults, it is usual to have the following means to detect and locate said faults:
    [0022] • Detection by balanced bridge of capacities and resistances grounded at the midpoint of the DC bus of the rotor. If there is a fault, the alternating current will return through the grounded point, unbalance the system and produce a voltage in the resistive zone. An overvoltage relay measuring in the resistance will trip the protection in this case.
    [0023] • Detection by injection of alternating current. Two points are established to ground with limiting impedances that make this point accessible. The system measures current in a grounded reader in series with one of these points and injects alternating current. The injection current value is known. If the current increases it means that a third point to ground is supporting the system and an overcurrent relay placed in series with the injector trips.
    [0025] As a reference, the following patents should be taken into account as a method of protecting machine rotors:
    [0026] - ES2321270-B2 entitled: "Ground fault detection system and method in direct current systems fed by rectifiers. " Where a method of detecting earth fault in direct current systems is exposed by measuring current or voltage.
    [0027] - ES2547468-B2 entitled: " Method for detecting earth faults in direct current systems fed by a rectifier." Where the frequency of the wave read in a resistance connected between a neutral point and ground is analyzed.
    [0028] - US4667262-A entitled: "Device for detecting a ground fault in the rotor winding of an electric machine." Where the leakage current is measured in the DC bus of the excitation of the machine and the machine is tripped if so.
    [0029] - US4812751-A entitled: "Apparatus for monitoring earth faults on the rotor winding of a generator." Where a grounding resistance is switched between the positive pole and the fault is detected by analyzing the recorded waves.
    [0031] In the detection and location of defects, tools such as the frequency response analysis of a system can also be used by means of the controlled injection of voltage at the input terminals and subsequent reading at the output terminals. With the variations in the transfer functions it is possible to detect where there are possible defects. This principle of operation is representative for the invention presented here.
    [0033] Several experiments for the detection of ground faults by frequency response analysis have been carried out on different articles, however not for localization:
    [0034] - CA Platero, F. Blázquez, P. Frías and D. Ramírez, "Influence of Rotor Position in FRA Response for Detection of Insulation Failures in Salient-Pole Synchronous Machines," in IEEE Transactions on Energy Conversion, vol. 26, no.2, pp. 671-676, June 2011.
    [0035] - SM Islam and G. Ledwich, "Locating transformer faults through sensitivity analysis of high frequency modeling using transfer function approach," Conference Record of the 1996 IEEE International Symposium on Electrical Insulation, Montreal, Quebec, Cañada, 1996, pp.
    [0036] 38-41 vol.1.
    [0038] And it is also convenient to take into consideration the patent US6417672-B1 entitled: "Detection of Bridge Tap Using Frequency Domain Analysis." In this invention, faults in the operation of equipment are located by evaluating the signal emitted and received by two devices placed in the ends of the transmission line where it is placed Depending on the type of the transfer function, different types of fault can be detected.
    [0040] Considering the prior art and the problems caused by earth faults in electrical circuits, it is convenient to develop new systems and methods for detecting earth faults, capable of detecting which fault resistance the earth fault in question has and in which turn it is produces this fault (in the event of a fault in electrical windings), since this would speed up repair and / or maintenance tasks. For this, in the invention presented here a system and a method is considered that by measuring the frequency response is capable of proceeding not only to the detection of the defect but also to the location of the same and the definition of the fault parameters. (loop where the fault is found, n, and the fault resistance between conductor and earth, Rf).
    [0042] DESCRIPTION OF THE INVENTION
    [0044] The present invention seeks to address all the limitations, disadvantages, and drawbacks of the prior art ground fault locating systems and methods described above.
    [0046] In a first aspect of the invention, a method of locating ground faults in electrical windings is disclosed. The method of the present invention comprises the following steps:
    [0047] • calculate an angle of a feedforward transfer function rt (/), as
    [0048] or applying an input voltage "U r with the angle 9Ui ( f) at variable frequency" f "in direct supply on some ends of an electrical winding;
    [0049] or measure the output voltage "U2" and the angle dU2t ( f) of the output voltage "U2" on a resistance connected between one of the ends of the electrical winding and earth;
    [0050] compute an angle of a reverse-feed transfer function r b ( f), such as t , (/) = 0u2b ( f) ~ O ^ f) . For which 0u2b ( f) YM /) are calculated with the following sub-stages:
    [0051] or apply an input voltage "Ui" with the angle 0y i (/) at variable frequency "f" in reverse supply on the ends of the electrical winding;
    [0052] or measuring the output voltage "U2" and angle 9Ü2b {f) of the output voltage "U 2" on a resistor connected between the other end of the electrical winding and ground;
    [0053] calculating a resonant frequency fR by modifying the frequency f until r t (/) is zero;
    [0054] comparing the resonant frequency fR with a resonant frequency fRh predetermined and corresponding to the electrical winding without failure; calculate a direct resonant frequency fR1 by modifying the frequency f until it (f) is zero (this implicitly involves direct feeding); and calculating a reverse resonance frequency fR2 by modifying the frequency f until zb ( f) is zero (this implicitly entails reverse feeding);
    [0055] calculate fault resistances Rf (fR1) for the direct resonance frequency fR1 for each turn "n", and fault resistances Rf (fR2) for the inverse resonance frequency fR2 for each complementary turn "N-n + 1" by matching previously calculated model curves that relate for each turn "n" with a fault in the electrical winding, a resonance frequency with a fault resistance;
    [0056] calculate the fault resistance Rf as any one of the selected fault resistances between Rf (fR1) and Rf (fR2) for which it is satisfied that:
    [0060] being:
    [0061] Rf (fR1, n): is the fault resistance calculated for the curve of the turn n of an electrical winding at a direct supply resonance frequency;
    [0062] Rf (fR2, N-n + 1): is the fault resistance calculated for the curve of the complementary turn to n of an electrical winding at a resonance frequency with reverse supply;
    [0063] Tol: is a default tolerance value;
    [0064] • Calculate the loop with defect "n" from the previous matching of curves once the value of the fault resistance Rf is known and taking into account that the relationship Rf (fR1, n) is unique. In said matching of pairs values of resonance frequency for the same fault resistance, Rf, the matched curve corresponding to a determined fault resistance for a direct supply resonance frequency, fR1, in turn demarcates the fault loop, n as it is unique characteristic of the fault produced, Rf (fR1, n). Alternatively, the loop with defect "n" can be calculated from the previous matching of curves once the value of the defect resistance Rf is known and taking into account that the relation Rf ( fR2, N-n + 1) is also unique. That is, it can be found in reverse supply, directly obtaining N-n + 1 for a single fault resistance for forward and reverse supply, but for a cut-off point with the characteristic curve of N-n + 1 at a resonance frequency fR2. After undoing the known change the number of total turns of the winding, N.
    [0066] A non-limiting example of an embodiment of the previous stage can be seen graphically in Figure 4.
    [0068] In an embodiment of the invention, the step of comparing the resonance frequency fR with a predetermined resonance frequency fRh additionally it comprises emitting a warning signal when the resonance frequency fR is equal to the predetermined resonance frequency fRh. The warning signal is a sound electrical winding signal. Alternatively, the step of comparing the resonant frequency fR with a predetermined resonant frequency fRh further comprises emitting a warning signal when the resonant frequency fR is different from the predetermined resonant frequency fRh. In this case, the warning signal is an electrical winding failure signal.
    [0070] In another aspect of the invention, a ground fault location system in electrical windings is disclosed. The ground fault location system in electrical windings comprises:
    [0071] • a frequency response measurement equipment connectable to an electrical winding configured to supply the electrical winding with direct and reverse power; the frequency response measurement equipment in turn comprises:
    [0072] or an input voltage injection device "U1" with angle
    [0073]
    [0074]
    [0075] • a resonance frequency extraction subsystem configured to:
    [0076] or calculate an angle of a feedforward transfer function rt (/) and an angle of a reverse feed transfer function th ( f .
    [0083] where:
    [0085] T t: is the angle of the direct feed transfer function;
    [0086] Tb: is the angle of the transfer function in reverse feeding;
    [0087] 0U1: is the angle of the injection voltage;
    [0088] 0U2t: is the angle of the direct supply output voltage; 0U2b: is the angle of the reverse supply output voltage; f: is the voltage injection frequency at the input;
    [0089] or calculating a resonant frequency fR by modifying the frequency f until r t (/) is zero;
    [0090] or comparing the resonance frequency fR with a predetermined resonance frequency fRh (and corresponding to the electrical winding without failure);
    [0091] or calculating a direct resonant frequency fR1 by modifying the frequency f until it (f) is zero; and calculating an inverse resonance frequency fR2 by modifying the frequency f until t & (/) is zero;
    [0092] a comparison subsystem with fault resistance versus resonance frequency model curves configured to calculate fault resistances Rf (fR1) for the direct resonance frequency fR1 for each turn "n", and fault resistances Rf (fR2) for the inverse resonance frequency fR2 for each complementary turn "N-n + 1" by means of a matching of previously calculated model curves that relate for each turn "n" with a fault in the electrical winding, a resonance frequency with a fault resistance;
    [0093] a subsystem for calculating the fault loop and the fault resistance, which is configured to:
    [0094] or calculate the fault resistance Rf as any one of the fault resistances selected between Rf (fR1) and Rf (fR2) for which it is satisfied that:
    [0095] Rf ( ÍRi, n) - Rf ( fR2, N - n 1 ) | < Tol
    [0096] being:
    [0097] Rf (fR1, n): is the fault resistance calculated for the curve of the turn n of an electrical winding at a direct supply resonance frequency;
    [0098] Rf (fR2, N-n + 1): is the fault resistance calculated for the curve of the complementary turn to n of an electrical winding at a resonance frequency with reverse supply;
    [0099] Tol: is a default tolerance value;
    [0100] or calculate the loop with defect "n" from the matching of curves above once the value of the defect resistance Rf is known and taking into account that the relationship Rf (fR1, n) is unique.
    [0102] In an embodiment of the invention, the electrical winding ground fault location system additionally comprises a device for emitting a warning of the electrical winding status. The state can be of healthy winding or of fault / failure in the turn "n" calculated by the subsystem for calculating the fault turn and the fault resistance.
    [0104] In this invention, two types of voltage measurement are available: direct supply to the electrical winding and reverse supply on a calibrated output resistance / impedance. This allows to obtain the transfer functions (output-input relationship) corresponding to U2t and U2b respectively. The angle (also called the argument) of the transfer functions gives the direct and inverse resonance frequencies of the system, fR1 and fR2.
    [0106] The resonant frequency of the system is defined as that frequency that makes the angle of the transfer functions null for a given injection voltage frequency at the input of the frequency analysis device.
    [0108] With data from previous tests, model curves of fault resistance, Rf, are obtained as a function of the resonant frequency of the system, which can be, as a non-limiting example, those shown in Figure 4. Each electrical winding will have as many curves as there are turns. winding being organized as that of the fault loop (n) and its complementary (N-n + 1).
    [0109] The curves are used once we have fR1 and fR2 to obtain the fault resistance Rf, which is characteristic of the fault. For clarification, it is added that a fault in both direct supply and reverse supply has the same fault resistance. This premise delimits a pair of curves corresponding to turn n and N-n + 1 as curves that intersect at fR1 and fR2 for the same fault resistance, being the only possible case for this fault. Once the intersection of the curves is found, the parameters Rf and n are extracted from the graphs. Finally a fault notice is issued. In case of healthy electrical winding, the resonance frequency of the system is unique and previously located; if this value is issued, the healthy winding warning is issued.
    [0111] Another way of explaining the method of the present invention is detailed below. The present invention contemplates measuring the output voltages of the electrical winding and performing a frequency response analysis obtaining the forward and inverse transfer functions. Subsequently, the resonant frequency of the system is obtained and compared with the resonant frequency of the system under healthy operating conditions (fRh). If these are the same:
    [0115] The notice on the fault or healthy warning device is declared healthy.
    [0117] In the event that two resonant frequencies different from the resonant frequency of the system are found in healthy operating conditions, both data are retained (fR1 for the direct case and fR2 for the reverse case). The pairs of curves are matched by introducing the frequencies in the model curves and obtaining as many Rf as there are curves. These values are entered in a tolerance calculation in which, as for a given defect, the defect resistance is constant:
    [0121] where:
    [0122] Rf (fR1, n): is the fault resistance calculated for the curve of the turn n of the rotor of the electric winding at a resonance frequency a direct feed;
    [0123] Rf (fR2, N-n + 1): is the fault resistance calculated for the curve of the loop complementary to n of the electrical winding at a resonance frequency with reverse supply;
    [0124] Tol: is the tolerance of the comparison system;
    [0126] Furthermore, the invention contemplates a stage of extraction of the loop with defect, n, and the defect resistance, Rf, which, once located, is sent to a fault warning transmitter.
    [0128] In the same embodiment, the invention additionally contemplates a previous step of obtaining the transfer functions of the winding, at least at an angle, both in forward and reverse feeding.
    [0130] With transfer functions, the following stages are used to locate the ground fault:
    [0131] - a stage of searching for the resonant frequency of the system where at a certain input voltage injection frequency, the transfer functions with direct and inverse power supply are null in argument;
    [0132] - a step of comparing the resonance frequency obtained with the natural resonance frequency of the healthy system. If this frequency is equal, the invention contemplates a stage of sound signal emission;
    [0133] - a step for obtaining the resonant frequency with direct feed (fR1) and inverse (fR2) if the resonant frequency seen in the above transfer functions differs from the natural resonant frequency values of the healthy system;
    [0134] - a matching stage of model curves obtained from previous tests where different fault resistances are related to their resonance frequencies for each faulty turn, n. In this stage, the possible fault resistances of all the curves that contemplate a possible positive real value for the resonance frequencies obtained in the previous stage are collected.
    [0135] - a stage of calculation of tolerances where by means of the expression:
    [0139] where:
    [0140] Rf (fR1, n): is the fault resistance calculated for the curve of the turn n of the electrical winding at a direct supply resonance frequency;
    [0141] Rf (fR2, N-n + 1): is the fault resistance calculated for the curve of the loop complementary to n electrical winding at a resonance frequency with reverse supply;
    [0142] Tol: is the tolerance of the comparison system;
    [0143] and knowing that the fault resistance, Rf, has to be unique for each fault. Then, for both fR1 and fR2 the complementary curves n and N-n + 1 will have the same fault resistance;
    [0144] - a stage of extraction of the defect loop once the previous stage of calculation of tolerances is fulfilled. It is followed by a defect resistance extraction stage associated with the pair of curves that result from the matching stage;
    [0145] - a fault emission stage that emits a signal with the data of the faulty loop, n, and the fault resistance of the fault in question.
    [0147] BRIEF DESCRIPITION OF THE FIGURES
    [0149] Next, a series of figures that help to better understand the invention are described very briefly, which are expressly related to an embodiment of said invention and are presented as non-limiting examples thereof.
    [0151] Figure 1 is a schematic view of the direct supply connection of the device for frequency scanning and subsequent analysis of resonance frequencies of the faulty system;
    [0152] Figure 2 is a schematic view of the reverse power connection of the device for frequency scanning and subsequent analysis of resonance frequencies of the faulty system;
    [0154] Fig. 3 is a schematic view of each stage of the method of the invention; Y
    [0156] FIG. 4 is a graphical representation of the model curves that are used for ground fault location of the invention.
    [0158] NUMERICAL REFERENCES OF THE FIGURES
    [0160] (1) Frequency response measurement equipment;
    [0161] (2) Winding of a rotor of a synchronous generator;
    [0162] (3) Variable frequency alternating current source;
    [0163] (4) Direct supply voltage measurement equipment on a 50 Q resistance;
    [0164] (5) Resonance frequency extraction subsystem of the system;
    [0165] (6) Subsystem for comparison with model curves of fault resistance versus resonance frequency of the system;
    [0166] (7) Subsystem for calculating the fault loop and the fault resistance of the system;
    [0167] (8) Subsystem for the issuance of a fault or healthy state notice;
    [0168] (9) Fault resistance, Rf;
    [0169] (10) Missing in turn n = 1;
    [0170] (11) Missing in turn n;
    [0171] (12) Reverse supply voltage measurement equipment on a 50 Q resistance;
    [0172] (13) Missing in turn n '= N with reverse feed (n = 1);
    [0173] (14) Missing in turn n '= N-n + 1 with reverse feed (n);
    [0174] (15) Argument of the direct feed transfer function;
    [0175] (16) Reverse-fed transfer function argument;
    [0176] (17) Stage of searching for the resonance frequency of the fR system;
    [0177] (18) Stage of comparison of fR obtained with the resonance frequency of the healthy system fRh;
    [0178] (19) Stage of sound signal emission;
    [0179] (20) Step for obtaining the resonance frequency with direct supply, fRi;
    [0180] (21) Stage for obtaining the resonant frequency with reverse feeding, fR2;
    [0181] (22) Stage of matching of model curves with fR1 and fR2;
    [0182] (23) Stage of calculation of tolerances;
    [0183] (24) Stage of extraction of the defect turn, n;
    [0184] (25) Stage fault resistance, Rf;
    [0185] (26) Stage of fault signal emission;
    [0186] (27) Resonance frequency.
    [0188] DESCRIPTION OF A FORM OF EMBODIMENT OF THE INVENTION.
    [0190] A description of an embodiment of the invention is now made with the aid of Figures 1 to 4.
    [0192] Figure 1 represents a non-limiting example of the ground fault location system in the case of direct power supply for locating a fault in an electrical winding, which is a rotor of a synchronous generator. In figure 1 two earth faults have been represented, which cannot occur simultaneously, however, it is represented by way of explanation, since this can occur in any loop, either from 1 (this being the first (10 )) to N (where N is the last turn of the rotor (2)). The random loop where a ground fault (11) with or without fault resistance (9) in direct supply is called "n". In this embodiment, with a non-limiting nature of the invention, the fault location system to land consists of:
    [0193] • a frequency response measurement equipment (1) connected to a winding of a synchronous generator rotor (2). Inside the equipment there is a variable frequency alternating current source (3) and a voltage measurement equipment (4) in direct supply on a 50 Q resistance.
    [0194] • a resonance frequency extraction subsystem of the system (5);
    [0195] • a subsystem for comparison with model curves of fault resistance versus resonant frequency of the system (6);
    [0196] • a subsystem for calculating the fault loop and the fault resistance of the system (7); Y
    [0197] • finally, a subsystem for issuing a warning of fault or healthy status (8).
    [0199] Figure 2 represents a non-limiting example of the ground fault location system in the case of reverse power for locating a fault in a rotor of a synchronous generator. In figure 2 two earth faults (13,14) have been represented, which cannot occur simultaneously, however it is used for the explanation of what this can be in any loop. The random loop where a ground fault (14) can occur with or without fault resistance (9) in reverse supply is called n '= N-n + 1. In this non-limiting embodiment of the invention, the ground fault location system in electrical windings consists of:
    [0200] • a frequency response measurement equipment (1) connected to a winding of a synchronous generator rotor (2). Inside the equipment there is a variable frequency alternating current source (3) and a voltage measurement equipment in reverse supply on a 50 Q resistance (12).
    [0201] • a resonance frequency extraction subsystem of the system (5);
    [0202] • a subsystem for comparison with model curves of fault resistance versus resonant frequency of the system (6);
    [0203] • a subsystem for calculating the fault loop and the fault resistance of the system (7); Y
    [0204] • finally, a subsystem for issuing a fault or healthy state warning (8).
    [0206] Figure 3 shows the electrical winding ground fault location method of the present invention. The method as described in figure 3 comprises the following steps:
    [0207] • Insertion of the argument of the transfer function with direct feeding (15) and argument of the transfer function with reverse feeding (16) of the respective tests at variable frequency carried out for example in Figures 1 and 2;
    [0208] • a stage of searching for the resonance frequency of the system (17) where the angle of the transfer function is zero;
    [0209] • a stage of comparison of fR obtained with the resonance frequency of the system in healthy state (18) where if the resonance frequency of the system is the same as in previous sound records, a healthy system warning is issued through an emission stage sound signal (19);
    [0210] • a step for obtaining the resonant frequency with direct feeding, fR1 (20) and a step for obtaining the resonant frequency with reverse feeding, fR2 (21);
    [0211] • when both resonance frequencies are obtained, a matching stage of model curves is carried out with fR1 and fR2 (22) where the different fault resistances are calculated;
    [0212] • a tolerance calculation stage (23) where the fault resistances obtained are compared and the one that is closest to 0 is selected, since for a given fault there is only one fault resistance either with direct or reverse supply ;
    [0213] • a stage of extraction of the fault loop, n (24) and a stage of fault resistance, Rf (25); Y
    [0214] • a fault signal emission stage (26).
    [0216] Figure 4 shows a set of model curves obtained from previous tests. This comprises curves of different fault resistances (9) as a function of the resonance frequency where they occur (27) for each specific turn of an electrical winding. Introducing the resonance frequencies, fR1 and fR2, obtained from the transfer functions, a unique pair of curves is obtained between the loop with defect, n, and its complementary, N-n + 1 for the same resistance of defect, Rf.
    权利要求:
    Claims (5)
    [1]
    1. Ground fault location method in electrical windings, characterized in that it comprises the following stages:
    • calculate (15) an angle of a direct feed transfer function rt (/), such as rt (/) = 0y2t (/) - 0y i (/), for which 0Ü2t ( f) AND OuiiD are calculated with the following sub-stages:
    • apply an input voltage "Ui" with the angle 0y i (/) at variable frequency T in direct supply on some ends of an electrical winding;
    • measure the output voltage "U2" and the angle 0y2t (/) of the output voltage "U2" on a resistance connected between one of the ends of the electrical winding and ground;
    • calculate (16) an angle of a reverse feed transfer function tb ( f), such as t & (/) = 0Ü2b ( f ) - ^ (Z), for which dÜ2b (/) and 0y i (/) are calculated with the following sub-stages:
    • apply an input voltage "Ui" with the angle 0y i (/) at variable frequency "f" in reverse supply on the ends of the electrical winding;
    • measure the output voltage "U2" and the angle dÜ2b ( f ) of the output voltage "U 2 " over a resistance connected between the other end of the electrical winding and earth;
    • calculating (17) a resonance frequency fR by modifying the frequency f until zt ( f) is zero;
    • comparing (18) the resonant frequency fR with a predetermined resonant frequency fRh (and corresponding to the electrical winding without failure);
    • calculate (20) a direct resonance frequency fR1 by modifying the frequency f until quert (/) is zero; and calculating (21) an inverse resonance frequency fR2 by modifying the frequency f until zb ( f) is zero;
    • calculate (22) some fault resistances Rf (fR1) for the frequency of direct resonance fR1 for each turn "n", and fault resistances Rf (fR2) for the frequency of inverse resonance fR2 for each complementary turn "N-n + 1" by means of a matching of previously calculated model curves that relate for each turn "n" with a fault in the electrical winding, a resonance frequency with a fault resistance;
    • calculate (23) the fault resistance Rf as any one of the fault resistances selected between Rf (fR1) and Rf (fR2) for which it is satisfied that:

    [2]
    2. Method for locating ground faults in electrical windings, according to claim 1, characterized in that the step of comparing the resonance frequency fR with a predetermined resonance frequency fRh additionally comprises emitting (19) a warning signal when the frequency resonance frequency fR is equal to the predetermined resonance frequency fRh.
    [3]
    3. Method for locating earth faults in electrical windings, according to claim 1, characterized in that the step of comparing the resonance frequency fR with a predetermined resonance frequency fRh additionally comprises emitting (26) a warning signal when the resonant frequency fR is different from the default resonant frequency fRh.
    [4]
    4. System for locating earth faults in electrical windings, characterized in that it comprises:
    • a frequency response measurement equipment (1) connectable to an electrical winding (2) configured to supply the electrical winding with direct and reverse power; the frequency response measurement equipment (1) in turn comprises:
    or a device (3) for injection of input voltage "U1" with angle 0y i (/) at variable frequency "f" configured to carry out a supply on the ends of an electrical winding (2); and,
    or a measuring device (4, 12) of an output voltage "U2" with angle 0Uzt ( f) on a resistance of predetermined value, where the resistance is connected between one end of the electrical winding and ground;
    • a resonance frequency extraction subsystem (5) configured to:
    or calculate an angle of a feedforward transfer function rt (/) and an angle of a reverse feed transfer function zh ( f)

    [5]
    5. System for locating earth faults in electrical windings, according to claim 1, characterized in that it comprises a device for issuing a warning (8) of the electrical winding fault / sound.
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    ES2784533B2|2021-03-03|
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    ES2848598A1|2020-12-30|2021-08-10|Univ Madrid Politecnica|SYSTEM AND METHOD OF LOCATION OF EARTH FAULTS IN WINDINGS OF ELECTRICAL MACHINES |
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