• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    System and method of protection against internal faults in winding rotor induction machines. The present invention can detect internal faults in systems, whether the short circuit occurs in the stator or in the rotor of a winding rotor induction machine (2). The differential current wave calculated as a result of the comparison of the currents measured in the stator (9) and in the rotor (10), after the application of different correction factors (11) and the transformed one, is used as an indicator of the defects. Of park (12) and (13). The amplitude of said differential current, allows to distinguish between internal defects to the machine and external to it. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2639811A1
    申请号:ES201730202
    申请日:2017-02-20
    公开日:2017-10-30
    发明作者:Carlos Antonio Platero Gaona；Ángel MUÑOZ GARCÍA；Marta Redondo Cuevas；Rosa María DE CASTRO FERNÁNDEZ
    申请人:Universidad Politecnica de Madrid；
    IPC主号:
    专利说明:

    SYSTEM AND METHOD OF PROTECTION AGAINST INTERNAL FAULTS IN WINDING ROTOR INDUCTION MACHINES

    D E S C R I P C I Ó N
     5

    OBJECT OF THE INVENTION
    The present invention is applicable to electrical systems in which winding rotor induction machines are involved, whose stator is fed directly from a three-phase alternating current network, and the electrical circuit of the rotor is accessible through the friction rings thereof .

    Case of special application are the double fed induction machines whose stator is fed from a three-phase network and whose rotor is connected to a converter system and a transformer. fifteen

    A clear application is wind and hydroelectric power generation systems, in which the generation system consists of a winding rotor induction machine. With the system object of the present invention, short circuits of any kind can be detected in both the stator and the rotor. twenty

    BACKGROUND OF THE INVENTION
    Every generation electrical installation must be provided with protection systems that make it safe against possible short circuits and other defects that may cause damage to the facilities that make up the electrical system, as well as to people.

    In the case of generation groups, these protections must also guarantee the supply of energy to the grid in the most reliable way possible, contributing to maintaining the stability of the electrical system and trying to discriminate where the fault occurs.

    The main technology used for the production of electrical energy in wind farms and hydroelectric plants are winding rotor induction machines whose stator is connected directly to the power grid, and whose rotor is connected to the same network through an electronic converter system and A power transformer. There are different modes of operation of the double-powered induction machine: 5
    • Supersynchronous generator
    • Sub synchronous motor
    • Subsynchronous generator
    • Supersynchronous motor
     10
    The importance of this type of machine not only affects the generation of electrical energy. Its work in the regulation of the electrical system contributing to maintaining the stability of the network is essential to preserve the quality of the electricity supply.
     fifteen
    A short circuit is that electrical fault that contacts two or more active conductors that have different potential, or at a point of zero potential. There are different short circuits that can occur in every three-phase power system:
    • Three-phase short circuit 20
    • Biphasic short circuit
    • Biphasic short to ground
    • Single-phase short to ground

    When any of these short circuits occur, large electrodynamic stresses occur, which will result in vibrations and heating.

    Before short circuits inside the machine, the usual practice is to use protection relays that, depending on the parameterization used, will give alarm signals or cause the group to disconnect. 30
    There are several methods to detect short circuits in winding rotor induction machines:
    • Instantaneous or timed overcurrent protections. The codes that receive said protection systems according to the ANSI code are 50 and 51 respectively. The first one causes the instantaneous tripping of the corresponding cutting element when an overcurrent value is exceeded. The second establishes an inverse time characteristic based on the value of the overcurrent. 5

    • Directional overcurrent protections (ANSI Code 67). In this type of protection, in addition to taking into account the value of the overcurrent, the address is also taken into account. This achieves a certain selectivity of action and to be able to locate the missing point. 10

    DESCRIPTION OF THE INVENTION
    The present invention makes it possible to detect defects inside asynchronous winding rotor machines whose stator is fed directly from the mains and the rotor is accessible from the outside. The method has the advantage of rapid action and allows the distinction between faults that occur both in the stator and in the rotor.

    The principle of operation of a differential protection is based on Kirchhoff's first law according to which, "the vector sum of all currents that reach a 20 point must be zero."

    The current measurement will be carried out by installing measurement transformers in the three-phase stator input system and in the rotor inlet, before the brushes. 25

    Under normal operating conditions (without incidents internal to the machine) or with an external fault to it, the currents measured by both circuits will be equivalent, so the differential current will be zero.
     30
    However, in the event of an internal fault, the contribution to the short circuit from the circuit connected to the stator and from the one connected to the rotor is not equivalent, so a differential current that triggers the trip circuit will appear.

    A series of correction factors will be applied to compare the measured stator and rotor currents:
    • The number of turns of the stator is different from that of the rotor which implies that the voltage levels are different and therefore the currents that circulate. That is why it is necessary to apply a correction factor to correct the transformation ratio.

    • The connection group of the static and rotor windings also influences the circulating currents. In general, both windings will be connected 10 stars so it will not be necessary to apply any correction factor.

    • The frequencies of the stator and rotor currents are different due to the sliding between them.
     fifteen
    The model of the invention takes these factors into account in such a way that two equivalent currents directly comparable to each other are obtained.

    The analysis of the signal obtained will be done as follows, the signals measured by the current transformers are sent to a protection relay that performs the following treatment:
    First, a correction factor is applied to the currents measured in the rotor to achieve equivalent currents in amplitude, thus correcting the existing differences as a result of the different number of turns and connection group.
     25
    Second, the Park transform will be applied to both three-phase current systems measured in the stator and rotor. With said transform, the measured currents are referred to a rotating coordinate system by pressing the corresponding magnetic field speed, thus obtaining continuous signals comparable to each other. 30

    The Park transform matrix is shown below.


    To apply this transform, it is necessary to know the reference angle of the stator and rotor.
     5
    The stator reference angle is measured directly by analyzing the stator supply voltage

    The rotor reference angle can be obtained directly by measuring the angle of rotation of the machine's rotor shaft or by measuring the speed of rotation of the rotor shaft and by adding a step of calculating the rotor reference angle.

    The currents obtained by applying the Park transform are:

     fifteen


    Finally, the difference between these transformed signals is obtained and sent to comparators, which will be previously regulated at set values below which there will be no protection action. twenty
    Under normal operating conditions or external failure, the comparison of the transformed currents will result in a null or almost null differential current.

    When the fault is internal, the differential current resulting from one or more of the transformed currents will be of high value and the relay will send the trip signal to the corresponding cut-off element.

    BRIEF DESCRIPTION OF THE FIGURES
    To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, a set of drawings is attached as an integral part of said description, where it is shown as an illustrative and non-limiting nature. the next:

    FIGURE 1: Shows a scheme of the system in which the present invention has application, where:
    (1) Network to which it is delivered or from which power is absorbed.
    (2) Winding rotor induction machine
    (3) Rotating rotor rings
     fifteen
    FIGURE 2: Shows a scheme of a particular system in which the present invention has application, where:
    (1) Network to which it is delivered or from which power is absorbed.
    (2) Winding rotor induction machine
    (3) Rotor friction rings 20
    (4) Converter system
    (5) Machine side converter
    (6) Network side converter
    (7) Continuous bars
    (8) Rotor connection transformer 25

    FIGURE 3: Shows a scheme of the differential method, indicating the mode of operation of the relay with indirect measurement of the rotor reference angle in a winding rotor induction machine, where:
    (1) Network to which it is delivered or from which power is absorbed. 30
    (2) Winding rotor induction machine
    (3) Rotating rotor rings
    (9) Stator measurement current transformer
    (10) Rotor measurement current transformer
    (11) Correction factor by number of turns and connection group
    (12) Park transform of stator currents
    (13) Park transform of rotor currents
    (14) Calculation of the differential current component axis d 5
    (15) Calculation of the differential current component axis q
    (16) Calculation of the homopolar component differential current
    (17) Trigger threshold of the d-axis component differential current
    (18) Trigger threshold of the differential current component axis q
    (19) Trigger threshold of the homopolar component differential current 10
    (20) D-axis component differential current comparator
    (21) Q-axis component differential current comparator
    (22) Homopolar component differential current comparator
    (23) “Or” Door
    (24) Trigger signal 15
    (25) Relay
    (26) Measurement of the stator reference angle
    (27) Rotor shaft rotation speed measurement
    (28) Calculation of the rotor reference angle
     twenty
    FIGURE 4: It shows a scheme of the differential method, indicating the mode of operation of the relay with direct measurement of the rotor reference angle in a winding rotor induction machine, where:
    (29) Measurement of rotor reference angle
     25
    FIGURE 5: It shows a scheme of the differential method, indicating the mode of operation of the relay with indirect measurement of the rotor reference angle, in a doubly fed induction machine.

    FIGURE 6: It shows a scheme of the differential method, indicating the mode of operation 30 of the relay with direct measurement of the rotor reference angle, in a doubly fed induction machine.
    FIGURE 7: Shows the waves obtained in a simulation performed with the model of a winding rotor induction machine, where different defects have been made at an internal point of the machine.

    The induced defects of duration 0.1s are: 5
    • Three phase short circuit t = 1s
    • Biphasic short circuit t = 1.5s
    • Biphasic short circuit to earth t = 2s
    • Single-phase short to ground t = 2.5s
     10
    The following current systems are shown:
    • Static currents
    • Rotary currents
    • D-axis differential current
    • Differential current axis q 15
    • Axis differential current or

    FIGURE 8: Shows the wave obtained in a simulation performed with the model of a winding rotor induction machine, where different defects have been made at an external point of the machine. twenty

    The induced defects of duration 0.1s are:
    • Three phase short circuit t = 1s
    • Biphasic short circuit t = 1.5s
    • Biphasic short circuit to earth t = 2s 25
    • Single-phase short to ground t = 2.5s

    The following current systems are shown:
    • Static currents
    • Rotary currents 30
    • D-axis differential current
    • Differential current axis q
    • Axis differential current or
    PREFERRED EMBODIMENT OF THE INVENTION

    1.- Differential protection applied to a winding rotor induction machine.
     5
    Next, a preferred embodiment of the object of the invention is described, applied to the particular case of a winding rotor induction machine, whose rotor is connected to any other equipment or short-circuited:

    Figure 1 shows the scheme of a winding rotor induction machine (2) 10 whose stator is fed directly from a three-phase network (1) and whose rotor is accessible through the friction rings (3).

    Figures 3 and 4 show the scheme of the model of the invention applied to an asynchronous winding rotor machine. fifteen

    For defect detection, current must be measured at stator terminals (9) and rotor rings (10). Said measured currents are carried to a relay (25).

    To reference the currents measured by the equipment (9) and (10) to a system 20 equivalent in amplitude, a correction factor (11) will be applied that will take into account the different number of turns of the stator and the rotor and its group of Connection.

     To eliminate the effect of slippage on the frequencies of the stator and rotor currents, the Park transform (12) and (13) will be applied to both systems of 25 currents. This will require obtaining the reference angles of the stator and rotor.

    The stator reference angle is measured directly by analyzing the stator supply voltage (26). 30

    The rotor reference angle can be obtained directly by measuring the angle of rotation of the machine's rotor shaft (Figure 4 - (29)) or by measuring the speed of rotation of the rotor shaft (Figure 3 - (27)) and by adding a calculation stage of the rotor reference angle (Figure 3 - (28)).
    The differences between the continuous currents of the stator and the rotor calculated in (14), (15) and (16) will be taken to the comparators (20), (21) and (22).
     5
    If any of the differential signals exceed a certain preset threshold value (17), (18) and (19), the trip signal (24) will be given to the corresponding cut-off element.

    In the event of a short circuit of any kind inside the induction machine, the calculated differential currents (14), (15) and (16) will have a very high value, so that the established threshold values will be exceeded ( 17), (18) and (19) and the trip signal (24) will be sent.

    If the defect occurs external to the machine, the differential currents calculated 15 in (14), (15) and (16) will be almost null and much lower than the threshold values (17), (18) and (19) so that trigger signal will not be sent (24).

    In figure 7 you can see the wave obtained in a simulation performed with the model of a winding rotor induction machine, where 20 different defects have been made at an internal point of the machine.

    The induced defects of duration 0.1s are:
    • Three phase short circuit t = 1s
    • Biphasic short circuit t = 1.5s 25
    • Biphasic short circuit to earth t = 2s
    • Single-phase short to ground t = 2x5s

    The following current systems are shown:
    • Static currents 30
    • Rotary currents
    • D-axis differential current
    • Differential current axis q
    • Axis differential current or
    In figure 8 you can see the wave obtained in the same simulation, when the defect occurs external to the machine.

    The induced defects of duration 0.1s are: 5
    • Three phase short circuit t = 1s
    • Biphasic short circuit t = 1.5s
    • Biphasic short circuit to earth t = 2s
    • Single-phase short to ground t = 2x5s
     10
    The following current systems are shown
    • Static currents
    • Rotary currents
    • D-axis differential current
    • Differential current axis q 15
    • Axis differential current or

    2.- Differential protection applied to a double fed induction machine.
     twenty
    Next, a preferred embodiment of the object of the invention is described, applied to the particular case of a doubly fed induction machine, whose rotor is connected to a converter system:

    Figure 2 shows the scheme of a double fed induction machine 25 whose stator is fed directly from a three-phase network (1) and whose rotor is connected to a converter system (4) and a transformer (8)

    Figures 5 and 6 show the scheme of the model of the invention applied to a double fed asynchronous machine. 30

    For defect detection, current must be measured at stator terminals (9) and rotor rings (10). Said measured currents are carried to a relay (25).

    To reference the currents measured by the equipment (9) and (10) to an equivalent system in amplitude, a correction factor (11) will be applied that will take into account the different number of turns of the stator and the rotor and its connection group .
     5
    To eliminate the effect of slippage on the frequencies of the stator and rotor currents, the Park transform (12) and (13) will be applied to both current systems. This will require obtaining the reference angles of the stator and rotor.
     10
    The stator reference angle is measured directly by analyzing the stator supply voltage (26).

    The rotor reference angle can be obtained directly by measuring the angle of rotation of the machine's rotor shaft (Figure 6 - (29)) or by measuring the rotation speed 15 of the rotor shaft (Figure 5 - (27)) and adding a step of calculating the rotor reference angle (Figure 5 - (28)).
    The differences between the continuous currents of the stator and the rotor calculated in (14), (15) and (16) will be taken to the comparators (20), (21) and (22).
     twenty
    If any of the differential signals exceed a certain preset threshold value (17), (18) and (19) the corresponding cut-off element (24) will be triggered.

    In the event of a short circuit of any kind inside the induction machine, the calculated differential currents (14), (15) and (16) will have a very high value, so the established threshold values will be exceeded ( 17), (18) and (19) and the trip signal (24) will be sent.

    If the defect occurs external to the machine, the differential currents calculated 30 in (14), (15) and (16) will be almost null and much lower than the threshold values (17), (18) and (19) so that trigger signal will not be sent (24).
    权利要求:
    Claims (4)
    [1]

    1.- Differential protection method for winding rotor induction machines, comprising:
    a) stage of measurement of stator currents 5
    b) measurement stage of rotor currents
    c) machine shaft speed measurement stage
    d) calculation stage of the rotor reference angle
    e) stator reference angle calculation stage
    f) calculation stage that applies the Park transform to the rotor and 10 stator currents
    g) stage of comparison of the homopolar components, d and q of the rotor and stator currents
    characterized in that it performs the firing of the machine depending on the difference of the homopolar components, d and q of the rotor and the stator. fifteen

    [2]
    2.- Method of differential protection for winding rotor induction machines, comprising:
    a) stage of measurement of the stator currents
    b) measurement stage of rotor current 20
    c) machine axis rotation angle measurement stage
    d) stator reference angle calculation stage
    e) calculation stage that applies the Park transform to the rotor and stator currents
    f) stage of comparison of the homopolar components, d and q of the rotor and stator currents 25
    characterized in that it performs the firing of the machine depending on the difference of the homopolar components, d and q of the rotor and the stator.

    [3]
    3.- Differential protection system for winding rotor induction machines, 30 comprising:
    a) measuring system of the stator currents
    b) rotor current measurement subsystem
    c) machine shaft speed measurement subsystem
    d) rotor reference angle calculation subsystem
    e) Stator reference angle calculation subsystem
    f) calculation subsystem that applies the Park transform to rotor and stator currents 5
    g) comparison subsystem of homopolar components, d and q of rotor and stator currents
    characterized in that the trigger signal is activated based on the difference of the homopolar, d and q components of the rotor and stator.
     10
    [4]
    4.- Differential protection system for winding rotor induction machines, comprising:
    a) measuring system of the stator currents
    b) rotor current measurement subsystem
    c) machine axis rotation angle measuring subsystem 15
    d) Stator reference angle calculation subsystem
    e) calculation subsystem that applies the Park transform to the rotor and stator currents
    f) comparison subsystem of homopolar components, d and q of rotor and stator currents 20
    characterized in that the trigger signal is activated based on the difference of the homopolar, d and q components of the rotor and stator.
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    同族专利:
    公开号 | 公开日
    WO2018150072A1|2018-08-23|
    ES2639811B2|2018-05-18|
    引用文献:
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    优先权:
    申请号 | 申请日 | 专利标题
    ES201730202A|ES2639811B2|2017-02-20|2017-02-20|SYSTEM AND METHOD OF PROTECTION AGAINST INTERNAL FAULTS IN WINDING ROTOR INDUCTION MACHINES|ES201730202A| ES2639811B2|2017-02-20|2017-02-20|SYSTEM AND METHOD OF PROTECTION AGAINST INTERNAL FAULTS IN WINDING ROTOR INDUCTION MACHINES|
    PCT/ES2018/070119| WO2018150072A1|2017-02-20|2018-02-20|System and method for protecting against internal faults in wound rotor induction machines|
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