• 专利附录
  • 专利说明
  • 权利要求
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  • 引用文献
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  • 优先权
    • 专利摘要:
    Invention of a method and system for locating earth faults in alternating current in electrical systems in direct current with inverters based on the statistical calculation on the voltage measurement in a device installed between a neutral point of the system and earth that allows to calculate the phase that is missing, as well as the percentage of failure on the impedance of said phase without the need to measure currents or know impedances of the system. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2736412A1
    申请号:ES201930868
    申请日:2019-10-07
    公开日:2019-12-30
    发明作者:Gaona Carlos Antonio Platero；Granados Jose Manuel Guerrero
    申请人:Universidad Politecnica de Madrid；
    IPC主号:
    专利说明:

    [0001]
    [0002] OBJECT OF THE INVENTION
    [0003]
    [0004] The present invention relates to a new system and method for the localization of earth faults in alternating current in electrical systems of direct current with inverters, which realizes the location of this type of defect by statistical methods, at any point of the electrical circuit of the part of alternating current, with the electrical circuit in operation.
    [0005]
    [0006] BACKGROUND OF THE INVENTION
    [0007]
    [0008] The diagnosis of electrical machines, as well as that of other electrical systems, is a field in which research is high and inventions are also high. One of the defects that can be sought by an invention dedicated to diagnosis are the faults to ground or against the chassis of electrical systems.
    [0009]
    [0010] These ground faults produce a leakage current through one of the phases resulting from the deterioration of the insulation in most cases. This leakage current, in case of having a second point connected to ground, can cause considerable failures, especially in the case of rigid grounding systems (TT).
    [0011]
    [0012] The most common methods for detecting faults are differential neutral relays, or differential relays. Also in the field of electric drives there are protections that cover 95% of the windings of a stator by means of a neutral overcurrent relay or of 100% of the winding, combining the previous one with a neutral undervoltage relay, which measures the third harmonic. However, these protections have no defect location at Earth.
    [0013]
    [0014] Another system and method of locating earth faults is to use measurements of two or more minimum impedance relays installed at different points of the electrical system and depending on the readings of both the fault can be located by solving a system of equations, product of the intersection of results of both relays.
    [0015]
    [0016] See the following patents and articles to consider the invention:
    [0017]
    [0018] PCT / US06 / 676747 (30.11.1984) US4766547 A (23.08.1988) Electric Power Research Institute SINGLE-ENDED TRANSMSSON LINE FAULT LOCATOR.
    [0019]
    [0020] P201331852 (18.12.2013) ES2454045 A1 (04.09.2014) UNIVERSIDAD POLITÉCNICA DE MADRID (100.00%) System and method for locating earth defects in static windings of grounded synchronous machines by means of a high value impedance.
    [0021]
    [0022] FR Blánquez, E. Rebollo and CA Platero, "Evaluation of the grounding circuit measurements for stator ground-fault location of synchronous generators," 2013 13th Intemational Conference on Environment and Eléctrica! Engineering ( EEEIC) , Wroclaw, 2013, pp. 229-233.
    [0023]
    [0024] F.R. Blánquez, C.A. Platero, E. Rebollo, F. Blázquez, “On-line stator ground-fault location method for synchronous generators based on 100% stator low-frequency injection protection”, Electric Power Systems Research, Volume 125, 2015, Pages 34-44, ISSN 0378-7796
    [0025]
    [0026] However, previous inventions require a prior characterization of the In addition to a wave with low harmonic content, such that the measurement is sharp enough to be able to record an accurate effective value.
    [0027]
    [0028] The invention provides a system and method that in the event of a ground fault in an electrical circuit (cable with lack of insulation that touches a metal sheet or other similar defect) locates exactly what cable it is in and in what percentage of cable length or impedance occurs, there may be loads between means in the circuit (percentage of equivalent impedance). This is based on the use of the high harmonic content of the voltage wave generated by the inverters to locate the defect produced without previously characterizing the equivalent impedance of the phase in question, or without the need to perform a joint voltage reading and currents, as do the minimum impedance relays, to locate the fault.
    [0029]
    [0030] DESCRIPTION OF THE INVENTION
    [0031]
    [0032] The invention relates to a method and system for locating earth faults on the side of alternating current in electrical systems of direct current power with inverters, regardless of in this second, the type of configuration you have, being able to be single-phase, two-phase , three-phase or successive provisions.
    [0033]
    [0034] The appearance of a residual current occurs due to the existence of a ground return between a fault that has occurred at one point in the system and another point previously connected to ground (in the case of electrical systems with grounding impedance, IT, and in rigidly grounded systems, TT) or in case of two ground faults in isolated systems (TN or neutral system isolated from earth). This residual current can cause the systems to malfunction and cause imbalances in the existing network. So it requires detectors and locators to avoid these situations.
    [0035]
    [0036] Currently many of the electrical systems are controlled by means of a Power electronics system that by opening and closing switches can control the frequency and amplitude of the waves. The location system presented here is optimal for detecting earth faults in systems with voltage waves produced by inverters that receive a continuous signal from a rectifier, where a large fundamental component is produced and notable higher order harmonics are available (an example it can be a pulse wave modulated voltage wave, PWM). In this sense, the state of the art is inefficient due to the high level of noise in the readings of the collected signals that are used for the location of the fault.
    [0037]
    [0038] The system of the invention comprises a voltage meter at a grounding impedance located at the midpoint of the direct current system, which continuously measures this voltage. It also includes a phase-neutral voltage meter on the alternating current side, by which the different phases of the alternating current system are measured. If the voltage reading at the grounding impedance is different from 0 V there is a ground fault and the phase-neutral voltage measurements of the alternating current side are taken into account.
    [0039]
    [0040] In one embodiment of the invention, the direct current system, at whose midpoint the grounding impedance is connected, is a direct current bus of an electronic converter.
    [0041]
    [0042] A voltage point value meter is then activated connected to terminals of the grounding impedance that samples the point values of the grounding impedance voltage. If the repetitions of the meter readings do not oscillate, the fault is on the DC side, but if they oscillate, the fault is on the AC side.
    [0043]
    [0044] Next, if the fault is on the alternating current side, the system of the invention locates the fault by means of a phase comparator device, which detects the offset reflected between the voltage wave on the current side. alternating, which produces the inverter in each of the phases (single-phase, two-phase, three-phase ...), and the voltage with respect to ground measured at the grounding impedance at the midpoint of the direct current system, which corresponds with the neutral point of said system. Comparisons in the phase comparator device (between waves) referenced to the neutral point of the system are made according to the following equation to identify the phase with defect:
    [0045]
    [0046] @ U gn d @ Ui.n @ Z g n d i ^ a d m
    [0047] Where:
    [0048]
    [0049] 0ugnd: is the argument of the voltage measured at terminals of the grounding impedance.
    [0050]
    [0051] 0Uin: is the argument of the voltage that carries the fault to ground or against the chassis.
    [0052]
    [0053] 0Zgnd: is the grounding impedance argument.
    [0054]
    [0055] Tadm: is the maximum tolerance of angle error produced in the calculation.
    [0056]
    [0057] The system and method of location of the fault, once the phase is known, transfers the meter readings of voltage point values to a histogram module, to calculate, by means of a statistical method, the location of the exact point of the lack in percentage of the equivalent impedance of the fault phase (already obtained by means of the phase comparator). For this, the histogram module is connected to a module for calculating the percentage of the phase of failure, which calculates its position according to the equation:
    [0058]
    [0059]
    [0060]
    [0061] Where:
    [0062]
    [0063]
    [0064]
    [0065] k: is the percentage of impedance as much as one over the impedance of the missing phase.
    [0066] Ugndfrec.max: it is the terminal voltage of the grounding impedance that is most repeated of non-zero value due to the realization of the histogram.
    [0067]
    [0068] Ugndpico: is the average peak voltage recorded in terminals of the grounding impedance resulting from the realization of the histogram.
    [0069]
    [0070] In addition, for the system to function properly, the high frequency harmonic content of the voltage waves must be considerably high.
    [0071]
    [0072] The voltage of the grounding impedance to be taken into account must be the most repeated in the numerator and the peak voltage in the denominator. The need to make a histogram occurs in order to collect these repetitions and thus know what the peak value is and what the maximum frequency value is.
    [0073]
    [0074] The maximum frequency voltage is due to the sum of voltages that comes from the healthy phases in the downstream area of the fault until the fault in question. This voltage wave will have a noise higher than the one introduced by the missing phase because more alternating current inverting elements are used to produce this wave than a single phase.
    [0075]
    [0076] The peak voltage can only be reached at certain times by the sum of all the stresses incident on the fault, so all phases have influence. That wave will have the same frequency as the frequency that a phase-neutral voltage of the alternating current system would have in healthy conditions.
    [0077]
    [0078] For the previous values, dividing one among the other, it is possible to obtain the point where the impedance has a ground fault. However, the phase as stated previously it has to be located primarily by the difference of arguments between waves.
    [0079]
    [0080] In addition, the invention performs the location of ground faults in systems with high noise waves, taking advantage of this characteristic that is usually against for most devices for the same purposes. All this through the use of very few measuring instruments (only measures voltage), unlike the prior art systems, which are inefficient due to the disturbances that this type of noise can introduce into the systems and also require At least the measurement of voltage and intensity. Nor does it require knowledge of phase or fault impedances.
    [0081]
    [0082] On the other hand, there is no system that uses statistical methods based on obtaining a histogram to detect ground faults.
    [0083]
    [0084] Finally, the system sends a signal outside it by means of a ground fault signal emission module.
    [0085]
    [0086] BRIEF DESCRIPTION OF THE FIGURES
    [0087]
    [0088] Next, a series of drawings that help to better understand the invention and that expressly relate to an embodiment of said invention that is presented as a non-limiting example thereof are described very briefly.
    [0089]
    [0090] A three-phase alternating current system through a six-pulse converter fed through a direct current stage, consisting of:
    [0091]
    [0092] (1): Grounding impedance.
    [0093] (2): Midpoint of the DC bus of an electronic converter.
    [0094] (3): Voltage measurement at grounding impedance.
    [0095]
    [0096] (4): Condenser in the continuous bus.
    [0097]
    [0098] (5): IGBT (Insulated Gate Bipolar Transistor) of the AC converter.
    [0099]
    [0100] (6): AC rectifier diode from the network.
    [0101]
    [0102] (7): Three-phase system of the variable frequency side of the converter.
    [0103] (8): Three-phase system from the network side to the converter.
    [0104]
    [0105] (9): Equivalent impedance of each phase.
    [0106]
    [0107] (10): Tension point values counter.
    [0108]
    [0109] (11): Phase-neutral phase voltage meter a.
    [0110]
    [0111] (12): Phase-neutral phase b voltage meter.
    [0112]
    [0113] (13): Phase-neutral phase c voltage meter.
    [0114]
    [0115] (14): Phase comparator device.
    [0116]
    [0117] (15): Histogram realization module.
    [0118]
    [0119] (16): Module for calculating the percentage of failure phase.
    [0120]
    [0121] (17): Earth fault signal emission module.
    [0122]
    [0123] The diagram shown in Figure 2 explains the method to follow:
    [0124]
    [0125] - A voltage measurement is recorded at the grounding impedance (3).
    [0126] - The phase-neutral voltages of the alternating current system are measured with the phase-neutral voltage meters of phases a (11), b (12) and c (13) and with the point voltage values counter (10) in the grounding impedance (1) it is calculated whether the fault is in direct current or alternating current.
    [0127] - If the fault is in direct current, the voltage at the grounding impedance is measured again and measured (3). If there is a current fault alternates the phase comparison is performed in the phase comparator device (14).
    [0128] - The histogram is performed in the histogram module (15). - The location of the fault in the error phase percentage calculation module (16) is calculated, according to the equation discussed in the previous section.
    [0129] - A signal is emitted with the corresponding information (phase and percentage of failure) with the earth fault signal emission module (17).
    [0130]
    [0131] Figure 3 shows a laboratory record of the voltage measurement at the grounding impedance (3) in a three-phase inverter, similar to that presented in Figure 1, with a ground fault and the phase voltage measurement. phase neutral a, b and c (11), (12), (13) on the AC side of the inverter.
    [0132]
    [0133] Figure 4 shows the histogram corresponding to the record of Figure 3. The example shown for these figures is in the section "Preferred embodiments", where the voltage wave is recorded in the grounding impedance (1), and Performs the histogram in the histogram realization module (15) to obtain the location of the percentage fault in the error phase percentage calculation module (16).
    [0134]
    [0135] PREFERRED EMBODIMENTS
    [0136]
    [0137] The description of preferred embodiments is then carried out.
    [0138]
    [0139] Preferred embodiment for alternating current systems with conversion of direct to alternating current in a power train of an electric vehicle.
    [0140]
    [0141] A non-limiting example of said application, of the system and method described, can be observed in the electric power train of an electric vehicle, where the voltage signal sent to the electric drive carries an SVM (Support Vector Machines) control based on the generation of a PWM wave (pulsewidth modulation) in stator terminals.
    [0142]
    [0143] In this case there are voltage waves with frequencies of the order of 10kHz ~ 20kHz that influence the control of the electric drive upstream of the converter to alternating current (5). These pulse width frequencies, which achieve a high content in the first harmonic and cancel the successive ones until some relevant harmonics are found from the 25 onwards, can be used to perform the histogram.
    [0144]
    [0145] Example of the complete operation in an alternating current system with conversion of direct current to alternating current.
    [0146]
    [0147] Be an alternating current systems with direct current to alternating current conversion with a grounding impedance (1) at the neutral point of the direct current bus of an electronic converter (2) where the voltage measurement is recorded at the impedance of grounding (3) (in this case pure resistive), located as shown in Figure 1, where there is a ground fault in phase "c" of the three-phase system of the variable frequency side of the converter.
    [0148]
    [0149] The protocol described above in Figure 2 is then activated:
    [0150]
    [0151] In the case of a three-phase 6-pulse inverter (see Figure 1) the voltage wave that would affect the equivalent phase impedance (9) in alternating current of phase c would have an upstream voltage produced by 2 IGBTs upstream converter to alternating current (5) and on the right side a voltage produced by the sum of two voltages out of 120 ° to each other produced by 4 IGBTs of the converter to alternating current (5).
    [0152]
    [0153] On the one hand, a voltage measurement is detected at the grounding impedance (3) (between the midpoint of the DC bus and ground), so that the phase-neutral voltage measurement of the phases a, b and c (11), (12), (13) of the alternating current system.
    [0154]
    [0155] In the phase carried out by the voltage point value counter (10), shown in Figure 4, it can be seen that since the fault occurs in phase "c" the sampling does not give a constant value so proceed to the phase comparison in the phase comparator device (14) from which the following results are obtained:
    [0156]
    [0157]
    [0158]
    [0159]
    [0160] According to the phase comparison equation, as the argument of the impedance of a grounding impedance is null because it is pure resistive, the fault occurs in phase "c" to be the one that best meets the equation:
    [0161]
    [0162] @ U gn d @ Ui.n @ Z g n d i T a d m
    [0163]
    [0164] A histogram of the values recorded in the point voltage values counter (10) of the voltage measurement at the grounding impedance (3) is then performed once the phase is located. The point values of the counter are transformed into an absolute value of all of them, they are classified in the histogram realization module (15) and finally the peak and average values 2.8 V and 1.4 V measured from the histogram are obtained (see the Figure 4), which implies that the fault is in:
    [0165]
    [0166]
    [0167]
    [0168]
    [0169] Therefore, the invention makes it possible to obtain the missing phase, as well as its location, without the need to use phase currents or phase impedance values, since it only depends on the relative difference between values of tension.
    [0170] Once the location of the fault is estimated, it is emitted, by means of the earth fault signal emission module (17), to an external device to inform the corresponding agent.
    权利要求:
    Claims (7)
    [1]
    1. Ground fault location system in alternating current in direct current systems with inverters, characterized in that it comprises:
    - a meter of the phase voltages of the alternating current system (11), (12), (13), which each inverter produces in each of the phases.
    - a grounding impedance (1) arranged between the midpoint (2) of the direct current and ground system.
    - a voltage meter (3) at the grounding impedance (1).
    - a voltage point value counter (10) at the grounding impedance (1).
    - a phase comparator device (14) for detecting the fault phase by comparing arguments between the voltage measurement at the grounding impedance (3) and the phase-neutral voltage measurements of the alternating current side (11) , (12), (13).
    - a histogram realization module (15) and a fault phase percentage calculation module (16) configured to locate earth faults in the alternating current system according to the equation:

    [2]
    2. Ground fault location system in alternating current in direct current systems with inverters based on claim 1, characterized in that the direct current system is a direct current bus of an electronic converter.
    [3]
    3. Ground fault location system in alternating current in DC systems with inverters based on claim 1, characterized in that it comprises a ground fault signal emission module (17) once the fault is located.
    [4]
    4. Method of locating earth faults in alternating current in DC systems with inverters characterized in that it comprises the following stages:
    - Phase of measurement of phase voltages of each phase of alternating current (11), (12), (13) produced by each inverter.
    - Voltage measurement stage (3) in a grounding impedance (1).
    - Stage of sampling of specific values of the voltage at the grounding impedance (10).
    - Stage of calculation of the phase where the earth fault occurs (14) according to the difference in argument that occurs between the voltage measurement in the grounding impedance (3) and the phase-neutral voltage measurements of the AC side (11), (12), (13) according to the equation:
    @Ugnd @ Ui.n @Zgnd i T adm
    Where:
    Ougnd is the argument of the voltage measured at terminals of the grounding impedance.
    0Uin: is the argument of the voltage that carries the ground fault or against the chassis.
    0Zgnd: is the grounding impedance argument.
    Tadm: is the maximum tolerance of angle error produced in the calculation.
    - Stage of statistical calculation of earth fault location by performing a histogram (15) comprising obtaining Ugndfrecmax and Ugndpico values from the absolute values of the point values of the voltage at the grounding impedance (10 ), and obtain the percentage of the impedance where the earth fault is located according to the equation:

    [5]
    5. Method of locating earth faults in alternating current in DC systems with inverters based on claim 4, characterized in that after the calculation of the phase in which the earth fault occurs, by argument comparison, then it comprises locating the percentage of impedance where the fault is in said phase.
    [6]
    6. Method of locating ground faults in alternating current in DC systems with inverters based on claim 4, characterized in that the voltage measurement stage in the grounding impedance (3) is carried out on the side of the DC system
    [7]
    7. Method of locating ground faults in alternating current in DC systems with inverters based on claim 4 characterized in that it comprises a step of issuing information about the fault location.
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    同族专利:
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    ES2736412B2|2020-06-10|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US4766549A|1984-11-30|1988-08-23|Electric Power Research Institute, Inc.|Single-ended transmission line fault locator|
    US20170131341A1|2013-10-08|2017-05-11|Rockwell Automation Technologies, Inc.|System and method for ground fault detection|
    ES2454045A1|2013-12-18|2014-04-09|Universidad Politécnica de Madrid|System and method of locating earth faults in stator windings of synchronous machines grounded by a high-value impedance. |
    法律状态:
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    申请号 | 申请日 | 专利标题
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