A method and device for internal fault differential protection of a converter transformer

Abstract

The application discloses a kind of converter transformer internal fault differential protection methods, by judging the relationship between YY converter transformer small difference differential current, YD converter transformer small difference differential current and corresponding threshold to identify whether converter transformer internal fault occurs, combined with differential action element rapid action export.It realizes that for the case of one converter transformer internal fault, the fault can be quickly identified, the fault clearing speed is accelerated, and the loss caused by converter transformer fault can be effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power system relay protection, in particular to a method and device for differential protection of internal faults of a converter transformer. BACKGROUND

[0002] The converter transformer is an important component of high-voltage and extra-high-voltage direct current transmission, and correct and fast operation of the converter transformer protection is crucial to the safe and stable operation of the direct current transmission system. According to the configuration of the converter transformer protection, Figure 1 A typical configuration of the converter transformer protection CT is shown in the figure. When an internal fault of the converter transformer occurs, the existing converter transformer differential protection uses the currents at the current transformers TA1, TA2, TA4 and TA6 to construct the differential criterion for the large-difference protection of the converter transformer, i.e. the currents at the current transformers TA3 and TA4 to construct the differential criterion for the small-difference protection of the YY converter transformer, and the currents at the current transformers TA5 and TA6 to construct the differential criterion for the small-difference protection of the YD converter transformer.

[0003] The current large-difference differential protection and small-difference differential protection are both provided with inrush current blocking criterion due to the excitation characteristics of the converter transformer. When an internal fault of the converter transformer occurs, the protection action time is greatly affected by the inrush current blocking criterion. In some fault conditions, even if the differential protection quickly meets the protection action condition, it still needs to wait for tens of milliseconds or even longer to open the inrush current blocking criterion, and the differential protection can only act to remove the faulty converter transformer after a long fault removal time. SUMMARY

[0004] The purpose of the present application is to provide a method for differential protection of internal faults of a converter transformer, which can quickly identify the internal fault of the converter transformer and improve the action speed of the small-difference differential protection in this case.

[0005] In order to achieve the above-mentioned purpose of the application, the present application is realized by the following technical solutions:

[0006] The first aspect of the present application provides a method for differential protection of internal faults of a converter transformer, comprising:

[0007] The acquisition step: acquiring the three-phase currents of the YY converter transformer at the grid side and the valve side, and the three-phase currents of the YD converter transformer at the grid side and the valve side;

[0008] The YY converter transformer small-difference three-phase differential current IdifyA, IdifyB, IdifyC is calculated based on the YY converter transformer grid-side winding three-phase current and the valve-side winding three-phase current, and the YD converter transformer small-difference three-phase differential current IdifdA, IdifdB, IdifdC is calculated based on the YD converter transformer grid-side winding three-phase current and the valve-side winding three-phase current;

[0009] The determination link adopts one of the following two schemes:

[0010] Scheme 1:

[0011] It is determined that the YY converter transformer is internally faulty if condition 1 is met, and the YY converter transformer small-difference differential protection is exported if it is determined that the YY converter transformer is internally faulty and the YY converter transformer small-difference differential element is actuated.

[0012] It is determined that the YD converter transformer is internally faulty if condition 2 is met, and the YD converter transformer small-difference differential protection is exported if it is determined that the YD converter transformer is internally faulty and the YD converter transformer small-difference differential element is actuated.

[0013] Scheme 2:

[0014] It is determined that the converter transformer is internally faulty if either condition 1 or condition 2 is met, the YY converter transformer small-difference differential protection is exported if it is determined that the converter transformer is internally faulty and the YY converter transformer small-difference differential element is actuated, and the YD converter transformer small-difference differential protection is exported if it is determined that the converter transformer is internally faulty and the YD converter transformer small-difference differential element is actuated.

[0015] Condition 1 includes that the YY converter transformer small-difference at least one-phase differential current is greater than the product of the YY converter transformer small-difference proportional coefficient and the YY converter transformer small-difference threshold value, and the YD converter transformer small-difference three-phase differential current is less than the product of the YD converter transformer small-difference proportional coefficient and the YD converter transformer small-difference threshold value.

[0016] Condition 2 includes that the YY converter transformer small-difference three-phase differential current is less than the product of the YY converter transformer small-difference proportional coefficient and the YY converter transformer small-difference threshold value, and the YD converter transformer small-difference at least one-phase differential current is greater than the product of the YD converter transformer small-difference proportional coefficient and the YD converter transformer small-difference threshold value.

[0017] In the preferred embodiment, the method further includes collecting the converter transformer grid-side incoming line switch three-phase current.

[0018] The converter transformer large-difference three-phase differential current IdifA, IdifB, IdifC is calculated based on the converter transformer grid-side incoming line switch three-phase current, the YY converter transformer valve-side winding three-phase current, and the YD converter transformer valve-side winding three-phase current.

[0019] Condition 1 further comprises that at least one phase differential current of the transformer differential large difference is greater than the product of the transformer differential large difference proportional coefficient and the transformer differential large difference threshold value.

[0020] Condition 2 further comprises that at least one phase differential current of the transformer differential large difference is greater than the product of the transformer differential large difference proportional coefficient and the transformer differential large difference threshold value.

[0021] In the preferred embodiment, the scheme 1 further comprises:

[0022] When it is determined that the YY transformer internal fault or the YD transformer internal fault, and the transformer differential large difference element acts, the transformer differential large difference protection exits.

[0023] In the preferred embodiment, the scheme 2 further comprises:

[0024] When it is determined that the transformer internal fault and the transformer differential large difference element acts, the transformer differential large difference protection exits.

[0025] In the preferred embodiment, the YY transformer differential small difference protection and the YD transformer differential small difference protection further comprise a current transformer disconnection blocking function, when the current transformer disconnection is detected, the corresponding protection is blocked.

[0026] In the preferred embodiment, the YY transformer differential small difference protection further comprises a surge current blocking criterion, and a determination result of the surge current blocking criterion is subjected to non-logic and then subjected to or logical operation with the YY transformer internal fault signal.

[0027] The YD transformer differential small difference protection further comprises a surge current blocking criterion, and a determination result of the surge current blocking criterion is subjected to non-logic and then subjected to or logical operation with the YD transformer internal fault signal.

[0028] In the preferred embodiment, the YY transformer differential small difference protection further comprises a surge current blocking criterion, and a determination result of the surge current blocking criterion is subjected to non-logic and then subjected to or logical operation with the YY transformer internal fault signal.

[0029] The YD transformer differential small difference protection further comprises a surge current blocking criterion, and a determination result of the surge current blocking criterion is subjected to non-logic and then subjected to or logical operation with the YD transformer internal fault signal.

[0030] In the preferred embodiment, the transformer differential large difference protection further comprises a surge current blocking criterion, and a determination result of the surge current blocking criterion is subjected to non-logic and then subjected to or logical operation with the YY transformer internal fault signal and the YD transformer internal fault signal.

[0031] In the preferred embodiment, the transformer differential large difference protection further comprises a surge current blocking criterion, and a determination result of the surge current blocking criterion is subjected to non-logic and then subjected to or logical operation with the YY transformer internal fault signal and the YD transformer internal fault signal.

[0032] In the preferred embodiment, the YY converter transformer small difference proportional coefficient is in the range of 0.5-0.8, and the YD converter transformer small difference proportional coefficient is in the range of 0.5-0.8.

[0033] In the preferred embodiment, the YY converter transformer small difference threshold value is in the range of 0.3-0.8Ie, and the YD converter transformer small difference threshold value is in the range of 0.3-0.8Ie, where Ie represents the rated current.

[0034] In the preferred embodiment, the large difference proportional coefficient is in the range of 0.5-0.8, and the large difference threshold value is in the range of 0.3-0.8Ie, where Ie represents the rated current.

[0035] The second aspect of the present application provides a converter transformer internal fault differential protection device, comprising:

[0036] one or more processors;

[0037] a storage device for storing one or more programs;

[0038] When the one or more programs are executed by the one or more processors, the one or more processors implement the method as described above.

[0039] The beneficial effects of the present application are: compared with the prior art, the technical scheme of the present application can identify the converter transformer internal fault by judging the relationship between the YY converter transformer small difference differential current and the YD converter transformer small difference differential current and the corresponding threshold value, accelerate the fault clearing speed, and effectively reduce the loss caused by the converter transformer fault. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 Typical configuration diagram for converter transformer protection CT;

[0041] Figure 2 Schematic diagram of a converter transformer internal fault differential protection method according to Embodiment One of the present application;

[0042] Figure 3 Action logic diagram according to Embodiment One of the present application;

[0043] Figure 4 Schematic diagram of a converter transformer internal fault differential protection method according to Embodiment Two of the present application;

[0044] Figure 5 Action logic diagram according to Embodiment Two of the present application;

[0045] Figure 6 Large difference protection action logic diagram provided by the present application;

[0046] Figure 7 This application provides another differential protection action logic diagram for embodiments;

[0047] Figure 8 The differential protection action logic diagram considering the interlocking logic is provided for the embodiments of this application;

[0048] Figure 9 Another differential protection action logic diagram considering interlocking logic is provided for embodiments of this application;

[0049] Figure 10 The differential protection action logic diagram considering the interlocking logic is provided for the embodiments of this application;

[0050] Figure 11 Another differential protection action logic diagram considering interlocking logic is provided for embodiments of this application;

[0051] Figure 12 This is a schematic diagram of the differential protection device for internal faults of the converter transformer provided in an embodiment of this application. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0053] like Figure 2 The illustrated embodiment is a schematic diagram of a differential protection method for internal faults in a converter transformer, including:

[0054] In the data acquisition stage of S101: the three-phase current of the YY converter transformer side winding and the three-phase current of the valve side winding are acquired, as well as the three-phase current of the YD converter transformer side winding and the three-phase current of the valve side winding are acquired.

[0055] The protective current is collected at various points using current transformers, with the direction pointing towards the converter transformer being positive in this embodiment. The three-phase current of the YY converter transformer side winding is denoted as... The three-phase current of the YY converter transformer valve side winding is denoted as... The three-phase current of the YD converter transformer side winding is denoted as... The three-phase current of the YD converter transformer valve side winding is denoted as...

[0056] In the calculation step of S102: the three-phase differential currents IdifyA, IdifyB, and IdifyC of the YY converter transformer are calculated based on the three-phase currents of the YY converter transformer winding on the grid side and the valve winding on the valve side; the three-phase differential currents IdifdA, IdifdB, and IdifdC of the YD converter transformer are calculated based on the three-phase currents of the YD converter transformer winding on the grid side and the valve winding on the valve side.

[0057] The current collection is to sum up the currents of each side by phase when the current flowing into the converter transformer is positive, to obtain the differential current. The current of each side can be a sampling value or an effective value.

[0058] The YY converter transformer small-difference three-phase differential current is calculated by using the three-phase current of the YY converter transformer grid side winding and the three-phase current of the YY converter transformer valve side winding by phase. When the sampling value is calculated, the specific calculation formula is as follows:

[0059]

[0060]

[0061]

[0062] The YD converter transformer small-difference three-phase differential current is calculated by using the three-phase current of the YD converter transformer grid side winding and the three-phase current of the YD converter transformer valve side winding by phase. When the sampling value is calculated, the specific calculation formula is as follows:

[0063]

[0064]

[0065]

[0066] In some embodiments, the current sampling value is also used to obtain the effective value by Fourier algorithm, and then the effective value is used to calculate the differential currents IdifyA, IdifyB, IdifyC, IdifdA, IdifdB and IdifdC. In some embodiments, the current sampling value or the effective value is also used to divide the rated current to obtain the per-unit value before calculating the differential current.

[0067] In the determination link of S103: whether condition 1 is met, if condition 1 is met, it is determined that the YY converter transformer internal fault; when the YY converter transformer internal fault is determined and the YY converter transformer small-difference differential element acts, the YY converter transformer small-difference differential protection acts and exits.

[0068] whether condition 2 is met, if condition 2 is met, it is determined that the YD converter transformer internal fault; when the YD converter transformer internal fault is determined and the YD converter transformer small-difference differential element acts, the YD converter transformer small-difference differential protection acts and exits. The logic relationship is as shown in Figure 3 .

[0069] Wherein, the condition 1 includes: YY converter transformer small difference at least one phase differential current is greater than YY converter transformer small difference proportional coefficient and YY converter transformer small difference threshold value product, and YD converter transformer small difference three-phase differential current is all less than YD converter transformer small difference proportional coefficient and YD converter transformer small difference threshold value product. Can be expressed by formula as follows:

[0070]

[0071] The condition 2 includes: YY converter transformer small difference three-phase differential current is all less than YY converter transformer small difference proportional coefficient and YY converter transformer small difference threshold value product, and YD converter transformer small difference at least one phase differential current is greater than YD converter transformer small difference proportional coefficient and YD converter transformer small difference threshold value product. Can be expressed by formula as follows:

[0072]

[0073] Wherein,

[0074] K1, K2 are YY converter transformer small difference proportional coefficient and YD converter transformer small difference proportional coefficient respectively, and it is suggested to take 0.5-0.8.

[0075] Ipickup1, Ipickup2 are YY converter transformer small difference threshold value and YD converter transformer small difference threshold value respectively, and the setting value can be set by dispatching department according to differential protection starting value setting principle and YY converter transformer rated parameter Ie, can be same as differential protection starting value setting or different. Generally, the setting range is 0.3-0.8 Ie, when differential current and braking current are calculated by per unit value, generally, the setting range is 0.3-0.8.

[0076] Wherein, differential element action refers to that differential current falls in the fault area of differential braking curve. Differential braking curve is the relationship curve of differential current and braking current, and generally, ratio braking differential protection curve is used. Differential current has been introduced before, and braking current generally adopts each current and half current, and in some embodiments, maximum current or half maximum current is also used, and in some embodiments, maximum current and the difference of other currents and half difference of other currents are also used.

[0077] YY converter transformer small difference three-phase braking current uses YY converter transformer grid side winding three-phase current, YY converter transformer valve side winding three-phase current and calculates by phase; when each current and half current are calculated, the specific calculation formula is as follows:

[0078]

[0079]

[0080]

[0081] YD converter differential braking current is calculated by YD converter differential current, YD converter differential current is calculated by YD converter grid side winding three-phase current and YD converter valve side winding three-phase current. The specific calculation formula is as follows:

[0082]

[0083]

[0084]

[0085] In some embodiments, the effective value is obtained by Fourier algorithm using current sampling value, and then the above braking current IryA, IryB, IryC, IrdA, IrdB and IrdC are calculated using the effective value. In some embodiments, the braking current is calculated by dividing the current sampling value or the effective value by the rated current to obtain the per-unit value.

[0086] The differential braking curve generally adopts an action curve with a ratio braking characteristic, the horizontal coordinate is the braking current, and the vertical coordinate is the differential current. In some embodiments, the differential braking curve of 2-fold line is selected; in some embodiments, the differential braking curve of 3-fold line is selected; in some embodiments, the differential braking curve of 4-fold line is selected; in some embodiments, the differential braking curve of 2-section is selected, and each section of the differential braking curve is set as the differential braking curve of 2-fold line or 3-fold line. Taking the differential braking curve of 3-fold line as an example, the specific calculation formula is as follows:

[0087] Id>Ks1*Ir+Ipkp(Ir<Knee1)

[0088] Id>Ks2*(Ir-Knee1)+Ks1*Knee1+Ipkp(Knee1<Ir<Knee2)

[0089] Id>Ks3*(Ir-Knee2)+Ks2*(Knee2-Knee1)+Ks1*Knee1+Ipkp(Knee2<Ir)

[0090] Wherein, Id is the differential current, Ir is the braking current, Ks1 is the slope of the first fold line, Ks2 is the slope of the second fold line, Ks3 is the slope of the third fold line, Knee1 is the intersection of the first fold line and the second fold line, Knee2 is the intersection of the second fold line and the third fold line, Ipkp is the differential starting constant. The slope relationship of the three fold lines is Ks1<Ks2<Ks3, and the fold line intersection is Knee1<Knee2.

[0091] Because when one of YY and YD converter transformer has internal fault, the fault converter transformer differential current will increase, and the non-fault converter transformer differential current should be zero, the embodiment of the scheme uses this principle to effectively identify the internal fault of the converter transformer, so that the differential element can not be blocked through the excitation inrush criterion when it acts, and the differential protection action speed is improved.

[0092] The scheme of the application will be described below in combination with a specific embodiment, taking a 2% turn-to-turn fault of the C-phase of the YD converter transformer grid-side winding in the no-load operation process as an example.

[0093] The differential protection adopts a three-fold line differential braking curve, Ks1=0.2, Ks2=0.5, Ks3=0.75, Knee1=0.5, Knee2=6, and the differential protection starting setting value Ipkp=0.5Ie.

[0094] According to S101, the three-phase currents of the YY converter transformer grid-side winding are collected The three-phase currents of the YY converter transformer valve-side winding The three-phase currents of the YD converter transformer grid-side winding The three-phase currents of the YD converter transformer valve-side winding The three-phase currents of the YY converter transformer grid-side winding and valve-side winding are both 0Ie; the A-phase and B-phase currents of the YD converter transformer grid-side winding and valve-side winding are both 0.1Ie, the grid-side winding C-phase current is 0.7Ie, and the valve-side winding C-phase current is 0.1Ie.

[0095] According to S102, the YY converter transformer small-difference three-phase differential currents IdifyA, IdifyB and IdifyC are calculated, and the YD converter transformer small-difference three-phase differential currents IdifdA, IdifdB and IdifdC are calculated; the calculation results are IdifC=0.3Ie, IdifdC=0.6Ie, and other differential currents are less than 0.1Ie.

[0096] According to the determination link of S103, K1 is 0.5 and K2 is 0.8 in the embodiment, and Ipickup1 and Ipickup2 are both set to 0.5Ie.

[0097] The calculation results are IdifyA=0<0.5*0.5Ie, IdifyB=0<0.5*0.5Ie, IdifyC=0<0.5*0.5Ie, IdifdC=0.6Ie>0.8*0.5Ie, condition 2 is met, and it is determined that the YD converter transformer has internal fault; IdifdC=0.6Ie>0.5Ie (the differential protection starting setting value Ipkp), The differential braking curve calculation formula is brought in to obtain IdifdC=0.6Ie>Ks1*IrdC+Ipkp=0.58Ie, the differential current falls in the fault area of the differential braking curve, the YD converter differential small difference satisfies the action condition, the YD converter differential small difference protection action element acts, and the YD converter differential small difference protection action outlet is exported.

[0098] As Figure 4 shown in the second embodiment, the collection link S201 and the calculation link S202 are the same as S101 and the calculation link S102 of the foregoing embodiment, but the determination link S203 is: whether conditions 1 and 2 are satisfied, if any one condition is satisfied, the internal fault of the converter transformer is determined; when the internal fault of the converter transformer is determined and the YY converter differential small difference element acts, the YY converter differential small difference protection action outlet is exported; when the internal fault of the converter transformer is determined and the YD converter differential small difference element acts, the YD converter differential small difference protection action outlet is exported. The conditions 1 and 2 are the same as those in the first embodiment. The logic relationship diagram is shown in 5.

[0099] In the third embodiment of the present application, on the basis of the first and second embodiments, the collection link further includes: collecting the three-phase current of the line switch on the grid side of the converter transformer. The three-phase current of the line switch on the grid side of the converter transformer includes the three-phase current of the side switch and the three-phase current of the middle switch, and is respectively denoted as and

[0100] The calculation link further includes: calculating the three-phase differential current IdifA, IdifB and IdifC of the large difference of the converter transformer based on the three-phase current of the line switch on the grid side of the converter transformer, the three-phase current of the valve side winding of the YY converter transformer and the three-phase current of the valve side winding of the YD converter transformer. The differential current calculation principle is the same as that of the small difference part. Here, the specific calculation formula when the sampling value is calculated is as follows:

[0101]

[0102]

[0103]

[0104] Condition 1 in the determination link further includes that the at least one phase differential current of the large difference of the converter transformer is greater than the product of the large difference proportion coefficient of the converter transformer and the large difference threshold value of the converter transformer. It can be expressed by the formula as follows:

[0105]

[0106] Condition 2 further includes that the at least one phase differential current of the large difference of the converter transformer is greater than the product of the large difference proportion coefficient of the converter transformer and the large difference threshold value of the converter transformer. It can be expressed by the formula as follows:

[0107]

[0108] wherein,

[0109] K3 is a large-difference proportional coefficient of the converter transformer, and is recommended to be 0.5-0.8.

[0110] Ipickup3 is a large-difference threshold of the converter transformer, and can be set by the dispatching department according to the setting principle of the differential protection starting value and the rated parameter Ie of the converter transformer, and can be the same as or different from the setting of the differential protection starting value. Generally, the setting range is 0.3-0.8Ie, and when the differential current and the braking current are calculated in the per-unit value, the setting range is generally 0.3-0.8. In the embodiment, the reliability of judging the internal fault of the converter transformer is higher by increasing the large-difference differential current related criterion, but the sensitivity is slightly reduced.

[0111] In some embodiments, only YY converter transformer small differences and YD converter side small differences are modified, and the action speed of the small-difference differential protection under the condition of an internal fault of the converter transformer is improved, but the large-difference protection of the converter transformer still adopts the traditional strategy.

[0112] In some embodiments, in addition to the modification of YY converter transformer small differences and YD converter side small differences, the large-difference of the converter transformer is also modified. The method is that the determination link further includes:

[0113] When it is determined that the YY converter transformer is internally faulty or the YD converter transformer is internally faulty, and the large-difference differential element of the converter transformer acts, the large-difference differential protection of the converter transformer acts and exits, and the logic diagram is as shown in Figure 6 ;

[0114] Or,

[0115] When it is determined that the internal fault of the converter transformer and the large-difference differential element of the converter transformer act, the large-difference differential protection of the converter transformer acts and exits, and the logic diagram is as shown in Figure 7 .

[0116] In some embodiments, the YY converter transformer small-difference protection and the YD converter transformer small-difference protection further include a current transformer disconnection blocking function, and when the disconnection of the current transformer is detected, the corresponding protection is blocked.

[0117] In some embodiments, the large-difference protection of the converter transformer further includes a current transformer disconnection blocking function, and when the disconnection of the current transformer constituting the large-difference of the converter transformer is detected, the large-difference protection of the converter transformer is blocked.

[0118] In some embodiments, the YY converter transformer small differential protection further comprises a inrush blocking criterion, and a result of the inrush blocking criterion is subjected to a non-logic operation and then subjected to an or operation with the signal of the YY converter transformer internal fault; the YD converter transformer small differential protection further comprises a inrush blocking criterion, and a result of the inrush blocking criterion is subjected to a non-logic operation and then subjected to an or operation with the signal of the YD converter transformer internal fault. A logic diagram is shown in Figure 8 When the YY converter transformer internal fault or the YD converter transformer internal fault is determined, the or gate is opened, so that the protection action speed is not affected by the inrush blocking criterion.

[0119] In some embodiments, the YY converter transformer small differential protection further comprises a inrush blocking criterion, and a result of the inrush blocking criterion is subjected to a non-logic operation and then subjected to an or operation with the signal of the YY converter transformer internal fault; the YD converter transformer small differential protection further comprises a inrush blocking criterion, and a result of the inrush blocking criterion is subjected to a non-logic operation and then subjected to an or operation with the signal of the YD converter transformer internal fault. A logic diagram is shown in

[0120] The YD converter transformer small differential protection further comprises a inrush blocking criterion, and a result of the inrush blocking criterion is subjected to a non-logic operation and then subjected to an or operation with the signal of the YD converter transformer internal fault. A logic diagram is shown in Figure 9 .

[0121] In some embodiments, the converter transformer large differential protection further comprises a inrush blocking criterion, and a result of the inrush blocking criterion is subjected to a non-logic operation and then subjected to an or operation with the signals of the YY converter transformer internal fault and the YD converter transformer internal fault. A logic diagram is shown in Figure 10 .

[0122] In some embodiments, the converter transformer large differential protection further comprises a inrush blocking criterion, and a result of the inrush blocking criterion is subjected to a non-logic operation and then subjected to an or operation with the signals of the YY converter transformer internal fault and the YD converter transformer internal fault. A logic diagram is shown in Figure 11 .

[0123] The converter transformer differential protection, including the converter transformer large differential protection, the YY converter transformer small differential protection, and the YD converter transformer small differential protection, has a braking characteristic and a current transformer broken wire blocking function, and is not blocked by a inrush blocking criterion. A protection logic diagram is shown in Figure 2 .

[0124] The converter transformer internal fault differential protection device 200 according to the embodiment of the present application will be described below with reference to Figure 12 . Figure 12 The converter transformer internal fault differential protection device 200 shown is only an example, and should not bring any limitation to the function and use range of the embodiments of the present application.

[0125] As Figure 12As shown, the converter internal fault differential protection device 200 is manifested in the form of a general computing device. The components of the converter internal fault differential protection device 200 can include, but are not limited to: at least one processing unit 210, at least one storage unit 220, a bus 230 connecting different system components (including the storage unit 220 and the processing unit 210), a display unit 240, and the like.

[0126] The storage unit stores program codes which can be executed by the processing unit 210, so that the processing unit 210 executes the methods according to various exemplary embodiments of the present application described in the present specification. For example, the processing unit 210 can execute the methods as shown in FIG. Figure 2

[0127] The storage unit 220 can include a readable medium in the form of a volatile storage unit, such as a random access memory (RAM) 2201 and / or a cache memory unit 2202, and can further include a read-only memory (ROM) 2203.

[0128] The storage unit 220 can further include a program / utility 2204 having a set of (at least one) program modules 2205, such as an operating system, one or more application programs, other program modules, and program data, and each of these examples, or some combination thereof, can include implementation of a network environment.

[0129] The bus 230 can be one or more of several types of bus structures, including a storage unit bus or storage unit controller, a peripheral bus, a graphics acceleration port, a processing unit bus, or a local bus using any of a variety of bus architectures.

[0130] ​The converter transformer internal fault differential protection device 200 can also communicate with one or more external devices 300 (such as a keyboard, a pointing device, a Bluetooth device, etc.), with one or more devices that enable a user to interact with the converter transformer internal fault differential protection device 200, and / or with any devices (such as routers, modems, etc.) that enable the converter transformer internal fault differential protection device 200 to communicate with one or more other computing devices. Such communication can occur via the input / output (I / O) interface 250. Also, the converter transformer internal fault differential protection device 200 can communicate with one or more networks (such as a local area network (LAN), a wide area network (WAN), and / or the public network, such as the Internet) through a network adapter 260. The network adapter 260 can communicate with the other components of the converter transformer internal fault differential protection device 200 through the bus 230. It should be appreciated that although not shown, other hardware and / or software modules could be used in connection with the converter transformer internal fault differential protection device 200 including, but not limited to, microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data archival storage systems, etc.

[0131] It should be clearly understood that the present application describes how specific examples can be made and used, but that the application is not limited to any specifics of these examples. Rather, these principles are capable of application generally to numerous other embodiments based on the teachings of the present application.

[0132] Furthermore, it is noted that the aforementioned figures are merely schematic illustrations of the processes included in the method according to the exemplary embodiments of the present application, and are not intended for limiting purposes. It is readily understood that the processes shown in the aforementioned figures do not indicate or limit the time sequence of these processes. In addition, it is readily understood that these processes can be executed, for example, synchronously or asynchronously in a plurality of modules.

[0133] The exemplary embodiments of the present application are specifically shown and described above. It should be understood that the present application is not limited to the detailed structure, arrangement, or implementation method described herein; rather, the present application is intended to encompass various modifications and equivalent arrangements within the spirit and scope of the appended claims.

[0134] The basic principles and main features of the present application and the advantages of the present application have been shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above-described embodiments, and the above-described embodiments and descriptions in the specification are merely illustrative of the principles of the present application. Various changes and modifications can be made to the present application without departing from the spirit and scope of the present application, and such changes and modifications fall within the scope of the claimed present application. The scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for internal fault differential protection of a converter transformer, characterized in that, Comprise: Collecting link: collecting YY converter transformer net side winding three-phase current and valve side winding three-phase current, YD converter transformer net side winding three-phase current and valve side winding three-phase current; Calculation link: calculating YY converter transformer small difference three-phase differential current IdifyA, IdifyB, IdifyC based on the YY converter transformer net side winding three-phase current and valve side winding three-phase current, calculating YD converter transformer small difference three-phase differential current IdifdA, IdifdB, IdifdC based on the YD converter transformer net side winding three-phase current and valve side winding three-phase current; Determination link: using one of the following two schemes: Scheme 1: Judge whether condition 1 is met, if condition 1 is met, determine that YY converter transformer internal fault; When YY converter transformer small difference differential element acts, YY converter transformer small difference differential protection action export is determined as YY converter transformer internal fault; Judge whether condition 2 is met, if condition 2 is met, determine that YD converter transformer internal fault; When YD converter transformer small difference differential element acts, YD converter transformer small difference differential protection action export is determined as YD converter transformer internal fault; Scheme 2: Judge whether condition 1 and condition 2 are met, if any one condition is met, determine that converter transformer internal fault; When YY converter transformer small difference differential element acts, YY converter transformer small difference differential protection action export is determined as YY converter transformer internal fault; When YD converter transformer small difference differential element acts, YD converter transformer small difference differential protection action export is determined as YD converter transformer internal fault; Condition 1 comprises: YY converter transformer small difference at least one phase differential current is greater than the product of YY converter transformer small difference proportion coefficient and YY converter transformer small difference threshold, and YD converter transformer small difference three-phase differential current is less than the product of YD converter transformer small difference proportion coefficient and YD converter transformer small difference threshold; Condition 2 comprises: YY converter transformer small difference three-phase differential current is less than the product of YY converter transformer small difference proportion coefficient and YY converter transformer small difference threshold, and YD converter transformer small difference at least one phase differential current is greater than the product of YD converter transformer small difference proportion coefficient and YD converter transformer small difference threshold.

2. The method of claim 1, wherein the internal fault differential protection of the converter transformer is based on a comparison of the first and second phase currents. Also comprise: Collecting converter transformer net side incoming line switch three-phase current; Based on the converter transformer net side incoming line switch three-phase current, YY converter transformer valve side winding three-phase current and YD converter transformer valve side winding three-phase current, calculating converter transformer large difference three-phase differential current IdifA, IdifB, IdifC; Condition 1 also comprises that the converter transformer large difference at least one phase differential current is greater than the product of the converter transformer large difference proportion coefficient and the converter transformer large difference threshold; Condition 2 also comprises that the converter transformer large difference at least one phase differential current is greater than the product of the converter transformer large difference proportion coefficient and the converter transformer large difference threshold.

3. The method of claim 1, wherein the method further comprises: Also comprise: Collecting converter transformer net side incoming line switch three-phase current; Based on the converter transformer net side incoming line switch three-phase current, YY converter transformer valve side winding three-phase current and YD converter transformer valve side winding three-phase current, calculating converter transformer large difference three-phase differential current IdifA, IdifB, IdifC; The scheme 1 also comprises: When it is determined that the YY converter transformer internal fault or the YD converter transformer internal fault, and the converter transformer large difference differential element acts, the converter transformer large difference differential protection acts export.

4. The method of claim 1, wherein the internal fault differential protection of the converter transformer is based on a comparison of the first and second phase currents. Also comprising: Collecting the three-phase current of the converter transformer grid-side incoming line switch; Based on the three-phase current of the converter transformer grid-side incoming line switch, the three-phase current of the YY converter transformer valve-side winding and the three-phase current of the YD converter transformer valve-side winding, calculating the converter transformer large difference three-phase differential current IdifA, IdifB, IdifC; The scheme 2 also comprises: When it is determined that the converter transformer internal fault, and the converter transformer large difference differential element acts, the converter transformer large difference differential protection acts export.

5. The method of claim 1, wherein the method further comprises: The YY converter transformer small difference protection and the YD converter transformer small difference protection also comprise a current transformer broken line blocking function, when detecting the current transformer broken line, the corresponding protection is blocked.

6. The method of claim 1, wherein the method further comprises: The YY converter transformer small difference differential protection also comprises a inrush current blocking criterion, the determination result of the inrush current blocking criterion is subjected to non-logic, and then subjected to or operation with the signal of the YY converter transformer internal fault; The YD converter transformer small difference differential protection also comprises a inrush current blocking criterion, the determination result of the inrush current blocking criterion is subjected to non-logic, and then subjected to or operation with the signal of the YD converter transformer internal fault.

7. The method of claim 1, wherein the method further comprises: The YY converter transformer small difference differential protection also comprises a inrush current blocking criterion, the determination result of the inrush current blocking criterion is subjected to non-logic, and then subjected to or operation with the signal of the converter transformer internal fault; The YD converter transformer small difference differential protection also comprises a inrush current blocking criterion, the determination result of the inrush current blocking criterion is subjected to non-logic, and then subjected to or operation with the signal of the converter transformer internal fault.

8. The method of claim 3, wherein the method further comprises: The converter transformer large difference differential protection also comprises a inrush current blocking criterion, the determination result of the inrush current blocking criterion is subjected to non-logic, and then subjected to or operation with the signal of the YY converter transformer internal fault and the signal of the YD converter transformer internal fault.

9. The method of claim 4, wherein the method further comprises: The converter transformer large difference differential protection also comprises a inrush current blocking criterion, the determination result of the inrush current blocking criterion is subjected to non-logic, and then subjected to or operation with the signal of the converter transformer internal fault.

10. The method of claim 1, wherein the method further comprises: The YY converter transformer small difference proportional coefficient value range is 0.5-0.8, and the YD converter transformer small difference proportional coefficient value range is 0.5-0.

8.

11. The method of claim 1, wherein the method further comprises: The YY converter transformer small difference threshold value range is 0.3-0.8Ie, and the YD converter transformer small difference threshold value range is 0.3-0.8Ie, wherein Ie represents the rated current.

12. The method of claim 2, wherein the method further comprises: The large difference proportional coefficient value range is 0.5-0.8, and the large difference threshold value range is 0.3-0.8Ie, wherein Ie represents the rated current.

13. A converter transformer internal fault differential protection device, characterized by, Comprising: One or more processors; Storage means for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method as claimed in any one of claims 1-11.

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