A quick differential speed-break protection method and system for a transformer

Abstract

The application discloses a kind of transformer's quick differential speed break protection method and system, comprising: obtaining current differential current sampling point and the differential current sampling value of N-1 sampling points before it;Differential speed break protection criterion is judged based on current differential current sampling point and the differential current sampling value of N-1 sampling points before it, obtain first judgment result;Differential current sampling point and the differential current sampling value of N-1 sampling points before it are judged based on current differential current, whether to meet difference flow abnormal large number lockout criterion, obtain second judgment result;When setting CT saturation lockout access, judge whether to meet CT saturation lockout, obtain third judgment result;When the first judgment result indicates to meet differential speed break protection criterion, and second judgment result indicates not to meet the difference flow abnormal large number lockout criterion, and the third judgment result indicates not to meet CT saturation lockout criterion, protection action export.

Description

Technical Field

[0001] The present invention relates to the technical field of relay protection, and more particularly to a fast differential quick-break protection method and system for a transformer. Background Art

[0002] As a key component of the power system, the safe and reliable operation of power transformers is crucial. When an internal fault occurs in a transformer, the transformer's relay protection device detects and clears the fault, ensuring both transformer safety and the stable operation of the power system.

[0003] Current differential protection, the primary protection for transformers, is widely used due to its simple principle and excellent selectivity. Conventional differential protection uses latching elements to prevent false trips due to abnormal conditions other than internal faults, such as CT saturation and magnetizing inrush current. Therefore, the operating time of conventional differential protection is closely linked to the performance of these latching elements. Furthermore, to prevent the latching elements from affecting the protection's operating speed and preventing it from clearing the fault quickly in the event of a severe internal transformer fault, transformer protection devices are often equipped with differential quick-tripping elements that do not require any latching. Relevant technical standards require differential protection to operate within 30ms and differential quick-tripping within 20ms. However, in recent years, severe faults have led to the rapid rise in fault current, resulting in rapid energy accumulation and heat dissipation, which can ultimately lead to transformer explosions and combustion. Therefore, to mitigate this, it is necessary to further improve the operating speed of protective devices for severe faults. This shortens the time it takes to clear severe faults, thereby reducing the risk of equipment explosions and combustion. Summary of the Invention

[0004] The present invention provides a fast differential quick-trip protection method and system for a transformer to solve the problem of how to prevent malfunction of the transformer.

[0005] In order to solve the above problem, according to one aspect of the present invention, a fast differential quick-trip protection method for a transformer is provided, the method comprising:

[0006] Obtain the differential current sampling values ​​of the current differential current sampling point and the N-1 sampling points before it;

[0007] Determine whether a differential quick-trip protection criterion is met based on the differential current sampling values ​​at the current differential current sampling point and the N-1 sampling points before it, and obtain a first judgment result;

[0008] Determine whether a differential current abnormally large number blocking criterion is met based on the differential current sampling values ​​at the current differential current sampling point and the N-1 sampling points before it, and obtain a second judgment result;

[0009] When CT saturation lockout access is set, determining whether CT saturation lockout is satisfied, and obtaining a third determination result;

[0010] When the first judgment result indicates that the differential quick-break protection criterion is met, and the second judgment result indicates that the abnormally large differential current blocking criterion is not met, and the third judgment result indicates that the CT saturation blocking criterion is not met, the protection action exits.

[0011] Preferably, the differential quick-trip protection criterion includes: a high sampling rate change sampling value differential quick-trip protection sub-criterion, a normal sampling rate half-wave Fourier differential quick-trip protection sub-criterion, and a normal sampling rate full-wave Fourier differential quick-trip protection sub-criterion; when any one of the high sampling rate change sampling value differential quick-trip protection sub-criterion, the normal sampling rate half-wave Fourier differential quick-trip protection sub-criterion, and the normal sampling rate full-wave Fourier differential quick-trip protection sub-criterion is met, it is determined that the differential quick-trip protection criterion is met.

[0012] Preferably, the high sampling rate variation sampling value differential quick-trip protection sub-criterion is valid within 10ms of the start of the protection starting element, and the high sampling rate variation sampling value differential quick-trip protection sub-criterion includes:

[0013] dicd(k)>s*Ie,

[0014] dicd(k)=i cd (k)-i cd (kN),

[0015] Where, dicd(k) is the differential current sampling value i at the current differential current sampling point k. cd (k) and the differential current sampling value i at the kNth sampling point cd (kN) difference; s is a preset multiple; Ie is the rated current; N is the data window length; when the above formula is satisfied, it is determined that the high sampling rate variation sampling value differential quick-break protection sub-criterion is satisfied.

[0016] Preferably, the step of determining whether the differential current sampling values ​​based on the current differential current sampling point and the N-1 sampling points before it meet the abnormally large differential current blocking criterion and obtaining the second judgment result includes:

[0017] Step 1, initialize m=1;

[0018] Step 2: Select m sample value data with the largest absolute value among N sample value data as the first data set, and the remaining data as the second data set;

[0019] Step 3, averaging the absolute values ​​of all sampled data in the second data set, and calculating the ratio of the average value to the maximum absolute value in the sampled data;

[0020] Step 4: If the ratio is less than or equal to the preset threshold value, and the current differential current sampling point is the sampling point corresponding to the data in the first data set, it is determined that there are m abnormally large points in the data window, and the current differential current sampling point is an abnormally large point, and the second judgment result is determined to meet the abnormally large differential current blocking criterion; if the ratio is less than or equal to the preset threshold value, and the current differential current sampling point is not the sampling point corresponding to the data in the first data set, it is determined that there are m abnormally large points in the data window, and the current differential current sampling point is not an abnormally large point, and the second judgment result is determined to meet the abnormally large differential current blocking criterion.

[0021] Preferably, the method further comprises:

[0022] If the ratio is greater than a preset threshold, determine whether m<M is satisfied. If so, update m=m+1 and return to step 2 to recalculate. If not, determine that there are no abnormally large points in the data window, and determine that the second judgment result does not meet the abnormally large differential flow locking criterion; where M is the set maximum number of cycles.

[0023] According to another aspect of the present invention, a fast differential quick-trip protection system for a transformer is provided, the system comprising:

[0024] A data acquisition unit is used to obtain the differential current sampling values ​​of the current differential current sampling point and the N-1 sampling points before it;

[0025] a first judgment unit, configured to judge whether a differential quick-trip protection criterion is met based on the differential current sampling values ​​at the current differential current sampling point and the differential current sampling values ​​at the N-1 sampling points before the current differential current sampling point, and obtain a first judgment result;

[0026] A second judgment unit is used to judge whether a differential current abnormally large number locking criterion is met based on the differential current sampling values ​​of the current differential current sampling point and the N-1 sampling points before it, and obtain a second judgment result;

[0027] a third judgment unit, configured to, when CT saturation locking access is set, judge whether CT saturation locking is satisfied and obtain a third judgment result;

[0028] An action output unit is used to protect the action output when the first judgment result indicates that the differential quick-break protection criterion is met, the second judgment result indicates that the differential current abnormally large number locking criterion is not met, and the third judgment result indicates that the CT saturation locking criterion is not met.

[0029] Preferably, the differential quick-trip protection criterion includes: a high sampling rate change sampling value differential quick-trip protection sub-criterion, a normal sampling rate half-wave Fourier differential quick-trip protection sub-criterion, and a normal sampling rate full-wave Fourier differential quick-trip protection sub-criterion; when any one of the high sampling rate change sampling value differential quick-trip protection sub-criterion, the normal sampling rate half-wave Fourier differential quick-trip protection sub-criterion, and the normal sampling rate full-wave Fourier differential quick-trip protection sub-criterion is met, it is determined that the differential quick-trip protection criterion is met.

[0030] Preferably, the high sampling rate variation sampling value differential quick-trip protection sub-criterion is valid within 10ms of the start of the protection starting element, and the high sampling rate variation sampling value differential quick-trip protection sub-criterion includes:

[0031] dicd(k)>s*Ie,

[0032] dicd(k)=i cd (k)-i cd (kN),

[0033] Where, dicd(k) is the differential current sampling value i at the current differential current sampling point k. cd (k) and the differential current sampling value i at the kNth sampling point cd (kN) difference; s is a preset multiple; Ie is the rated current; N is the data window length; when the above formula is satisfied, it is determined that the high sampling rate variation sampling value differential quick-break protection sub-criterion is satisfied.

[0034] Preferably, the second judgment unit determines whether the differential current abnormally large number locking criterion is met based on the differential current sampling values ​​of the current differential current sampling point and the N-1 sampling points before it, and obtains the second judgment result, including:

[0035] Step 1, initialize m=1;

[0036] Step 2: Select m sample value data with the largest absolute value among N sample value data as the first data set, and the remaining data as the second data set;

[0037] Step 3, averaging the absolute values ​​of all sampled data in the second data set, and calculating the ratio of the average value to the maximum absolute value in the sampled data;

[0038] Step 4: If the ratio is less than or equal to the preset threshold value, and the current differential current sampling point is the sampling point corresponding to the data in the first data set, it is determined that there are m abnormally large points in the data window, and the current differential current sampling point is an abnormally large point, and the second judgment result is determined to meet the abnormally large differential current blocking criterion; if the ratio is less than or equal to the preset threshold value, and the current differential current sampling point is not the sampling point corresponding to the data in the first data set, it is determined that there are m abnormally large points in the data window, and the current differential current sampling point is not an abnormally large point, and the second judgment result is determined to meet the abnormally large differential current blocking criterion.

[0039] Preferably, the second judgment unit is further configured to:

[0040] If the ratio is greater than a preset threshold, determine whether m<M is satisfied. If so, update m=m+1 and return to step 2 to recalculate. If not, determine that there are no abnormally large points in the data window, and determine that the second judgment result does not meet the abnormally large differential flow locking criterion; where M is the set maximum number of cycles.

[0041] The present invention provides a fast differential quick-trip protection method and system for a transformer, comprising: obtaining differential current sampling values ​​of a current differential current sampling point and N-1 sampling points before it; judging whether a differential quick-trip protection criterion is met based on the differential current sampling values ​​of the current differential current sampling point and N-1 sampling points before it, and obtaining a first judgment result; judging whether a differential current abnormally large number lockout criterion is met based on the differential current sampling values ​​of the current differential current sampling point and N-1 sampling points before it, and obtaining a second judgment result; when CT saturation lockout access is set, judging whether the CT saturation lockout is met, and obtaining a third judgment result; when the first judgment result indicates that the differential quick-trip protection criterion is met, and the second judgment result indicates that the differential current abnormally large number lockout criterion is not met, and the third judgment result indicates that the CT saturation lockout criterion is not met, a protection action exit is performed. The present invention can achieve rapid protection action in the event of a serious internal fault in the transformer (i.e., when the differential current is greater than the differential fast-break value), with an action time of less than 5ms (excluding the action time of the device outlet relay); the device will not malfunction in the event of an out-of-zone fault that causes CT saturation; the protection device will not malfunction in the event of any other out-of-zone fault or disturbance; and it will not malfunction when abnormal points appear in the differential current due to abnormal sampling. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

[0043] Figure 1 Flowchart of a fast differential quick-trip protection method 100 for a transformer according to an embodiment of the present invention;

[0044] Figure 2 This is a logic diagram of the overall output of the fast differential quick-trip protection according to an embodiment of the present invention;

[0045] Figure 3 A diagram for determining whether there are abnormally large points according to an embodiment of the present invention;

[0046] Figure 4 (a) and (b) are schematic diagrams of the three-phase current waveforms on the grid side and the three-phase current waveforms on the valve side under an intra-zone fault according to an embodiment of the present invention;

[0047] Figure 5 Schematic diagram of three-phase small differential current under intra-zone fault according to an embodiment of the present invention;

[0048] Figure 6 (a) and (b) are respectively a waveform diagram of the A-phase differential quick-break judgment data and a schematic diagram of the high-sampling-rate differential quick-break judgment result when a high-sampling-rate differential quick-break algorithm is adopted according to an embodiment of the present invention;

[0049] Figure 7 2. A schematic diagram of half-wave Fourier differential quick-tripping results when a conventional half-wave Fourier phasor differential quick-tripping algorithm at a low sampling rate is used under an intra-zone fault according to an embodiment of the present invention;

[0050] Figure 8 2. It is a schematic diagram of full-wave Fourier differential quick-tripping results when a full-wave Fourier phasor differential quick-tripping algorithm is used at a conventional low sampling rate under an intra-zone fault according to an embodiment of the present invention;

[0051] Figure 9 Schematic diagram of simulation results of abnormal large number recognition under intra-zone fault according to an embodiment of the present invention;

[0052] Figure 10 Schematic diagram of the overall operation exit of the device under an intra-zone fault according to an embodiment of the present invention;

[0053] Figure 11 (a) and (b) are schematic diagrams of the three-phase current waveforms on the grid side and the three-phase current waveforms on the valve side under an intra-zone fault according to an embodiment of the present invention;

[0054] Figure 12 Schematic diagram of three-phase small differential current under intra-zone fault according to an embodiment of the present invention;

[0055] Figure 13 (a) and (b) are respectively a waveform diagram of the A-phase differential quick-break judgment data and a schematic diagram of the high-sampling-rate differential quick-break judgment result when a high-sampling-rate differential quick-break algorithm is adopted according to an embodiment of the present invention;

[0056] Figure 142. A schematic diagram of half-wave Fourier differential quick-tripping results when a conventional half-wave Fourier phasor differential quick-tripping algorithm at a low sampling rate is used under an intra-zone fault according to an embodiment of the present invention;

[0057] Figure 15 2. It is a schematic diagram of full-wave Fourier differential quick-tripping results when a full-wave Fourier phasor differential quick-tripping algorithm is used at a conventional low sampling rate under an intra-zone fault according to an embodiment of the present invention;

[0058] Figure 16 Schematic diagram of simulation results of abnormal large number recognition under intra-zone fault according to an embodiment of the present invention;

[0059] Figure 17 Schematic diagram of the overall operation exit of the device under an intra-zone fault according to an embodiment of the present invention;

[0060] Figure 18 1 is a schematic structural diagram of a fast differential quick-trip protection system 1800 for a transformer according to an embodiment of the present invention. DETAILED DESCRIPTION

[0061] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to provide a thorough and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments shown in the accompanying drawings is not intended to limit the present invention. In the accompanying drawings, identical elements are denoted by the same reference numerals.

[0062] Unless otherwise specified, the terms used herein (including technical terms) have the meanings commonly understood by those skilled in the art. In addition, it is understood that terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0063] This invention aims to further improve the speed of transformer protection in the event of a severe fault. It proposes a rapid protection method based on the differential current rise rate, addresses the issue of malfunctioning of this protection method due to interference from abnormal sampling data such as lightning strikes and operational errors, and proposes a method to prevent malfunctioning. While the protection method rapidly activates after a severe internal transformer fault, it prevents malfunctions under other circumstances.

[0064] Figure 1 FIG. 1 is a flow chart of a fast differential quick-break protection method 100 for a transformer according to an embodiment of the present invention. Figure 1As shown, the fast differential quick-trip protection method 100 for a transformer provided by an embodiment of the present invention can realize fast protection action in the event of a serious internal fault in the transformer (i.e., when the differential current is greater than the differential quick-trip setting value), with an action time of less than 5ms (excluding the action time of the device output relay); the device does not malfunction in the event of an out-of-zone fault that causes CT saturation; the protection device does not malfunction in the event of any other out-of-zone fault or disturbance; and does not malfunction when abnormal sampling causes an abnormal point in the differential current. The fast differential quick-trip protection method 100 for a transformer provided by an embodiment of the present invention starts at step 101. In step 101, the differential current sampling values ​​of the current differential current sampling point and the N-1 sampling points before it are obtained.

[0065] In step 102, based on the differential current sampling values ​​at the current differential current sampling point and the N-1 sampling points before it, it is determined whether a differential quick-trip protection criterion is met, and a first determination result is obtained.

[0066] Preferably, the differential quick-trip protection criterion includes: a high sampling rate change sampling value differential quick-trip protection sub-criterion, a normal sampling rate half-wave Fourier differential quick-trip protection sub-criterion, and a normal sampling rate full-wave Fourier differential quick-trip protection sub-criterion; when any one of the high sampling rate change sampling value differential quick-trip protection sub-criterion, the normal sampling rate half-wave Fourier differential quick-trip protection sub-criterion, and the normal sampling rate full-wave Fourier differential quick-trip protection sub-criterion is met, it is determined that the differential quick-trip protection criterion is met.

[0067] Preferably, the high sampling rate variation sampling value differential quick-trip protection sub-criterion is valid within 10ms of the start of the protection starting element, and the high sampling rate variation sampling value differential quick-trip protection sub-criterion includes:

[0068] dicd(k)>s*Ie,

[0069] dicd(k)=i cd (k)-i cd (kN),

[0070] Where, dicd(k) is the differential current sampling value i at the current differential current sampling point k. cd (k) and the differential current sampling value i at the kNth sampling point cd (kN) difference; s is a preset multiple; Ie is the rated current; N is the data window length; when the above formula is satisfied, it is determined that the high sampling rate variation sampling value differential quick-break protection sub-criterion is satisfied.

[0071] Combine Figure 2As shown, the export logic of the method of the present invention is: the entire fast differential quick-break protection includes a starting element, a high sampling rate variation sampling value differential quick-break protection module, a normal sampling rate half-wave Fourier differential quick-break module, a normal sampling rate full-wave Fourier differential quick-break module, an abnormally large number locking module and a CT saturation locking module.

[0072] The main operating elements for the differential quick-trip circuit breaker are the high-sampling-rate differential quick-trip module for the variable sampling value, the normal-sampling-rate half-wave Fourier differential quick-trip module, and the normal-sampling-rate full-wave Fourier differential quick-trip module. The high-sampling-rate module is only active within 10ms of protection activation. Therefore, the high-sampling-rate differential quick-trip module is ANDed with the activation element after a 10ms delay. These three operating elements are implemented using an OR gate. The differential quick-trip operating element, after passing through the OR gate, undergoes abnormally high differential current blocking and CT saturation blocking before being released. Blocking is implemented using the final AND gate.

[0073] Conventional differential quick-trip protection does not undergo CT saturation blocking. However, in actual projects, improper selection of CTs on the low-voltage side may lead to out-of-zone faults, saturation of the low-voltage side CTs, and thus malfunction of the differential quick-trip.

[0074] Therefore, the present invention proposes making the CT saturation blocking criterion optional, allowing the user to select whether to enable or disable the protection based on the short-circuit capacity and CT characteristics in the actual transformer protection application environment. When CT saturation blocking is selected, high-sampling-rate data is processed and calculated for the CT saturation criterion, ensuring compatible blocking for both high-sampling-rate and normal-sampling-rate differential quick-trip elements.

[0075] Specifically, in the present invention, when the sampling value satisfies any one of the high sampling rate variation sampling value differential quick-trip protection sub-criterion, the normal sampling rate half-wave Fourier differential quick-trip protection sub-criterion, and the normal sampling rate full-wave Fourier differential quick-trip protection sub-criterion, it is determined that the differential quick-trip protection criterion is satisfied. The high sampling rate variation sampling value differential quick-trip protection sub-criterion is valid within 10ms of the activation of the protection initiation element, and the high sampling rate variation sampling value differential quick-trip protection sub-criterion includes:

[0076] dicd(k)>s*Ie,

[0077] dicd(k)=i cd (k)-i cd (kN),

[0078] Where, dicd(k) is the differential current sampling value i at the current differential current sampling point k. cd (k) and the differential current sampling value i at the kNth sampling point cd(kN); s is a preset multiple; Ie is the rated current; N is the data window length; when the above formula is satisfied, it is determined that the high sampling rate variation sampling value differential instantaneous protection sub-criterion is satisfied. Wherein, N can be 10 and s can be 3.

[0079] In step 103, based on the differential current sampling values ​​at the current differential current sampling point and the N-1 sampling points before it, it is determined whether a differential current abnormally large number locking criterion is satisfied, and a second judgment result is obtained.

[0080] Preferably, the step of determining whether the differential current sampling values ​​based on the current differential current sampling point and the N-1 sampling points before it meet the abnormally large differential current blocking criterion and obtaining the second judgment result includes:

[0081] Step 1, initialize m=1;

[0082] Step 2: Select m sample value data with the largest absolute value among N sample value data as the first data set, and the remaining data as the second data set;

[0083] Step 3, averaging the absolute values ​​of all sampled data in the second data set, and calculating the ratio of the average value to the maximum absolute value in the sampled data;

[0084] Step 4: If the ratio is less than or equal to the preset threshold value, and the current differential current sampling point is the sampling point corresponding to the data in the first data set, it is determined that there are m abnormally large points in the data window, and the current differential current sampling point is an abnormally large point, and the second judgment result is determined to meet the abnormally large differential current blocking criterion; if the ratio is less than or equal to the preset threshold value, and the current differential current sampling point is not the sampling point corresponding to the data in the first data set, it is determined that there are m abnormally large points in the data window, and the current differential current sampling point is not an abnormally large point, and the second judgment result is determined to meet the abnormally large differential current blocking criterion.

[0085] Preferably, the method further comprises:

[0086] If the ratio is greater than a preset threshold, determine whether m<M is satisfied. If so, update m=m+1 and return to step 2 to recalculate. If not, determine that there are no abnormally large points in the data window, and determine that the second judgment result does not meet the abnormally large differential flow locking criterion; where M is the set maximum number of cycles.

[0087] Combine Figure 3 As shown, in the present invention, the current k-th differential current sampling point and the N-1 points before it, a total of N points of differential current sampling values, are used to determine if the differential current is abnormally large. Figure 2 As shown, the judgment process is:

[0088] First, the N sampling points in the data window are calculated as shown in formula (1). That is, the sampling value with the largest absolute value among the N sampling values ​​is selected, and then the absolute values ​​of all sampling values ​​except this maximum value are averaged. Next, the ratio of this average value to the maximum absolute value is calculated to obtain the ratio λ1. If λ1 is less than a certain value k1, it is determined that there is an abnormally large value among the N differential flow sampling points. Further determine whether the current sampling point is the sampling point with the largest absolute value selected previously. If so, the current sampling point is an abnormally large value. Otherwise, it indicates that there is an abnormally large value in the current data window, but it is not the current differential flow sampling point. If the calculated λ1 is greater than a certain value, it is necessary to determine the two abnormally large values. The ratio λ2 is calculated using formula (2).

[0089] The calculation of λ2 is similar to λ1. When calculating the average value, the maximum and second-largest absolute values ​​are subtracted, and only the average value of N-2 points is calculated. The obtained λ2 is compared with the fixed value k2. If the ratio is less than the fixed value, it is determined that there are two abnormally large values ​​among the N differential flow sampling points. Further judgment is made as to whether the current sampling point belongs to the previously selected sampling point with the largest or second-largest absolute value. If so, it is determined that the current sampling point is one of the two abnormally large values. Otherwise, it indicates that there are two abnormally large values ​​in the current data window, but they are not the current differential flow sampling point. If the calculated λ2 is still greater than a certain value, it is necessary to judge the three abnormally large values. Calculate λ3 using formula (3).

[0090] The calculation of λ3 is similar to that of λ1 and λ2. When calculating the average value, simply subtract the maximum, second-largest, and third-largest values, and only calculate the average value of N-3 points. Comparing λ3 with the constant k3, if the ratio is less than the constant, it is determined that there are three abnormally large values ​​among the N differential flow sampling points. Further determination is made as to whether the current sampling point belongs to the previously selected sampling point with the largest, second-largest, or third-largest absolute value. If so, it is determined that the current sampling point is one of the three abnormally large values. Otherwise, it indicates that there are three abnormally large values ​​in the current data window, but they are not the current differential flow sampling point. If the calculated λ3 is still greater than a certain constant k3, it is determined that there are no abnormally large values ​​among the N sampling points.

[0091] in,

[0092]

[0093]

[0094]

[0095] Where k1, k2, and k3 are preset thresholds, with a recommended value of 0.01. N is the number of sampling points, and k represents the kth sampling point.

[0096] In the present invention, the identification of 4, 5, 6, ... multiple abnormally large points can be performed according to the set M.

[0097] When it is determined that there are m abnormally large points in the data window, the second judgment result is determined to meet the abnormally large differential current blocking criterion. Figure 2 The abnormally large differential current blocking module will output 1, and then output 0 after negation, and then perform an "AND" operation with the differential quick-break protection and CT saturation blocking protection to output the final action signal.

[0098] In step 104, when the CT saturation blocking condition is set, it is determined whether the CT saturation blocking condition is satisfied, and a third determination result is obtained.

[0099] Combine Figure 2 As shown, in the present invention, when CT saturation lockout is enabled, the switch is set to "1." A determination is then made as to whether the CT saturation lockout condition is met, yielding a third determination result. If the CT saturation lockout condition is met, a 1 is input. If not, a 0 is output. This is then ANDed with the differential instantaneous trip protection and the differential current abnormally high value lockout condition to produce the final action signal.

[0100] In step 105, when the first judgment result indicates that the differential quick-trip protection criterion is met, and the second judgment result indicates that the abnormally large differential current blocking criterion is not met, and the third judgment result indicates that the CT saturation blocking criterion is not met, the protection action exits.

[0101] In the present invention, if the first judgment result indicates that the differential quick-break protection criterion is met, and the second judgment result indicates that the abnormally large differential current blocking criterion is not met, and the third judgment result indicates that the CT saturation blocking criterion is not met, it means that there is a fault and the protection action exit is activated.

[0102] In the present invention, RTDS is used to carry out simulation verification of severe faults within the area.

[0103] 1. Simulation results of faults within the area

[0104] The three-phase current waveforms on the grid side and the valve side under the fault in the area are as follows: Figure 4 As shown in (a) and (b), the three-phase small differential current waveform under the fault in the area is as follows Figure 5 When using the high sampling rate differential quick-break algorithm, the A phase differential quick-break judgment data waveform and high sampling rate differential quick-break judgment results are shown as follows: Figure 6 As shown in the figure, when the conventional low sampling rate half-wave Fourier phasor differential quick trip algorithm is used under the fault in the area, the half-wave Fourier differential quick trip result is as follows: Figure 7 As shown in the figure, when the full-wave Fourier phasor differential quick-break algorithm is used under the conventional low sampling rate under the fault in the area, the full-wave Fourier differential quick-break result is as follows: Figure 8As shown in the figure, the simulation results of abnormal large number identification under fault in the area are as follows Figure 9 As shown, the overall operation output of the device under the fault in the area is as follows Figure 10 As shown. Figure 6 It can be seen that the action time of high sampling rate differential quick break is 3.5ms. Figure 7 It can be seen that the action time of the half-wave Fourier differential quick-break under the normal sampling rate is 16.5ms. Figure 8 It can be seen that the action time of differential quick-break is 18.1ms under normal sampling rate. Figure 9 It can be seen that the result of abnormal large number identification is no abnormal large number. Figure 10 The overall protection operation time is 3.5ms, which is the same as the first high-sampling-rate differential quick-trip protection operation time. Compared with conventional protection, the overall operation speed has been greatly improved.

[0105] 2. Simulation results of faults within the area

[0106] Under out-of-zone fault, the three-phase current waveforms on the grid side and the three-phase current waveforms on the valve side are as follows: Figure 11 As shown in (a) and (b), the three-phase small differential current waveform under the fault outside the zone is as follows Figure 12 When using the high sampling rate differential quick-break algorithm, the A phase differential quick-break judgment data waveform and high sampling rate differential quick-break judgment results are shown as follows: Figure 13 As shown in the figure, when the conventional low sampling rate half-wave Fourier phasor differential quick trip algorithm is used under out-of-zone fault, the half-wave Fourier differential quick trip result is as follows: Figure 14 As shown in the figure, when the full-wave Fourier phasor differential quick-break algorithm is used at a conventional low sampling rate under an out-of-zone fault, the full-wave Fourier differential quick-break result is as follows: Figure 15 As shown in the figure, the simulation results of abnormal large number recognition under out-of-area fault are as follows Figure 16 As shown, the overall action output of the device under out-of-zone fault is as follows Figure 17 As shown. Figures 13 to 17 It can be seen that when there is a fault outside the zone, the high sampling rate sampling value differential quick-break protection and the conventional sampling rate half-wave and full-wave Fourier differential quick-break protection do not operate, and the abnormal large number is identified as no abnormal large number, and finally the differential break does not operate as a whole.

[0107] In summary, the method of the present invention can effectively solve the problem of increasing the protection action speed under severe fault conditions, while preventing malfunction due to abnormal sampling.

[0108] Figure 18 FIG. 1 is a schematic structural diagram of a fast differential quick-break protection system 1800 for a transformer according to an embodiment of the present invention. Figure 18 As shown, the fast differential quick-trip protection system 1800 for a transformer provided in an embodiment of the present invention includes: a data acquisition unit 1801 , a first judgment unit 1802 , a second judgment unit 1803 , a third judgment unit 1804 and an action output unit 1805 .

[0109] Preferably, the data acquisition unit 1801 is configured to acquire differential current sampling values ​​of a current differential current sampling point and N-1 sampling points before the current differential current sampling point.

[0110] Preferably, the first judgment unit 1802 is configured to judge whether a differential quick-trip protection criterion is met based on the differential current sampling values ​​at the current differential current sampling point and the N-1 sampling points before it, and obtain a first judgment result.

[0111] Preferably, the differential quick-trip protection criterion includes: a high sampling rate change sampling value differential quick-trip protection sub-criterion, a normal sampling rate half-wave Fourier differential quick-trip protection sub-criterion, and a normal sampling rate full-wave Fourier differential quick-trip protection sub-criterion; when any one of the high sampling rate change sampling value differential quick-trip protection sub-criterion, the normal sampling rate half-wave Fourier differential quick-trip protection sub-criterion, and the normal sampling rate full-wave Fourier differential quick-trip protection sub-criterion is met, it is determined that the differential quick-trip protection criterion is met.

[0112] Preferably, the high sampling rate variation sampling value differential quick-trip protection sub-criterion is valid within 10ms of the start of the protection starting element, and the high sampling rate variation sampling value differential quick-trip protection sub-criterion includes:

[0113] dicd(k)>s*Ie,

[0114] dicd(k)=i cd (k)-i cd (kN),

[0115] Where, dicd(k) is the differential current sampling value i at the current differential current sampling point k. cd (k) and the differential current sampling value i at the kNth sampling point cd (kN) difference; s is a preset multiple; Ie is the rated current; N is the data window length; when the above formula is satisfied, it is determined that the high sampling rate variation sampling value differential quick-break protection sub-criterion is satisfied.

[0116] Preferably, the second judgment unit 1803 is configured to judge whether a differential current abnormally large number locking criterion is satisfied based on the differential current sampling values ​​at the current differential current sampling point and the N-1 sampling points before it, and obtain a second judgment result.

[0117] Preferably, the second judgment unit 1803 judges whether the differential current abnormally large number locking criterion is met based on the differential current sampling values ​​of the current differential current sampling point and the N-1 sampling points before it, and obtains the second judgment result, including:

[0118] Step 1, initialize m=1;

[0119] Step 2: Select m sample value data with the largest absolute value among N sample value data as the first data set, and the remaining data as the second data set;

[0120] Step 3, averaging the absolute values ​​of all sampled data in the second data set, and calculating the ratio of the average value to the maximum absolute value in the sampled data;

[0121] Step 4: If the ratio is less than or equal to the preset threshold value, and the current differential current sampling point is the sampling point corresponding to the data in the first data set, it is determined that there are m abnormally large points in the data window, and the current differential current sampling point is an abnormally large point, and the second judgment result is determined to meet the abnormally large differential current blocking criterion; if the ratio is less than or equal to the preset threshold value, and the current differential current sampling point is not the sampling point corresponding to the data in the first data set, it is determined that there are m abnormally large points in the data window, and the current differential current sampling point is not an abnormally large point, and the second judgment result is determined to meet the abnormally large differential current blocking criterion.

[0122] Preferably, the second judgment unit 1803 is further configured to:

[0123] If the ratio is greater than a preset threshold, determine whether m<M is satisfied. If so, update m=m+1 and return to step 2 to recalculate. If not, determine that there are no abnormally large points in the data window, and determine that the second judgment result does not meet the abnormally large differential flow locking criterion; where M is the set maximum number of cycles.

[0124] Preferably, the third judgment unit 1804 is configured to, when setting CT saturation blocking access, judge whether CT saturation blocking is satisfied, and obtain a third judgment result.

[0125] Preferably, the action exit unit 1805 is used to protect the action exit when the first judgment result indicates that the differential quick-trip protection criterion is met, and the second judgment result indicates that the differential current abnormally large number locking criterion is not met, and the third judgment result indicates that the CT saturation locking criterion is not met.

[0126] The fast differential quick-trip protection system 1800 for a transformer according to an embodiment of the present invention corresponds to the fast differential quick-trip protection method 100 for a transformer according to another embodiment of the present invention, and will not be described in detail here.

[0127] The present invention has been described with reference to a few embodiments. However, it is apparent to those skilled in the art that other embodiments than the ones disclosed above are equally within the scope of the present invention.

[0128] Generally, all terms used in this disclosure are to be interpreted according to their ordinary meaning in the art, unless explicitly defined otherwise herein. All references to "a / the / the [device, component, etc.]" are to be interpreted openly as referring to at least one instance of the device, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not necessarily need to be performed in the exact order disclosed, unless explicitly stated otherwise.

[0129] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0130] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0131] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0132] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A fast differential quick-break protection method for a transformer, characterized in that: The method comprises: Obtain the differential current sampling values ​​of the current differential current sampling point and the N-1 sampling points before it; Determine whether a differential quick-trip protection criterion is met based on the differential current sampling values ​​at the current differential current sampling point and the N-1 sampling points before it, and obtain a first judgment result; Determine whether a differential current abnormally large number blocking criterion is met based on the differential current sampling values ​​at the current differential current sampling point and the N-1 sampling points before it, and obtain a second judgment result; When CT saturation lockout access is set, determining whether CT saturation lockout is satisfied, and obtaining a third determination result; When the first judgment result indicates that the differential quick-trip protection criterion is met, and the second judgment result indicates that the differential current abnormally large number blocking criterion is not met, and the third judgment result indicates that the CT saturation blocking criterion is not met, the protection action output is performed; The step of determining whether the differential current sampling values ​​at the current differential current sampling point and the N-1 sampling points before the current differential current sampling point meet the abnormally large differential current blocking criterion and obtaining the second judgment result includes: Step 1, initialize m=1; Step 2: Select m sample value data with the largest absolute value among N sample value data as the first data set, and the remaining data as the second data set; Step 3, averaging the absolute values ​​of all sampled data in the second data set, and calculating the ratio of the average value to the maximum absolute value in the sampled data; Step 4: If the ratio is less than or equal to the preset threshold, and the current differential current sampling point is a sampling point corresponding to the data in the first data set, then it is determined that there are m abnormally large points in the data window, and the current differential current sampling point is an abnormally large point, and the second judgment result is determined to satisfy the abnormally large differential current blocking criterion; if the ratio is less than or equal to the preset threshold, and the current differential current sampling point is not a sampling point corresponding to the data in the first data set, then it is determined that there are m abnormally large points in the data window, and the current differential current sampling point is not an abnormally large point, and the second judgment result is determined to satisfy the abnormally large differential current blocking criterion; The method further comprises: If the ratio is greater than a preset threshold, determine whether m<M is satisfied. If so, update m=m+1 and return to step 2 to recalculate. If not, determine that there are no abnormally large points in the data window, and determine that the second judgment result does not meet the abnormally large differential flow locking criterion; where M is the set maximum number of cycles.

2. The method according to claim 1, characterized in that The differential quick-trip protection criterion includes: a high sampling rate change sampling value differential quick-trip protection sub-criterion, a normal sampling rate half-wave Fourier differential quick-trip protection sub-criterion, and a normal sampling rate full-wave Fourier differential quick-trip protection sub-criterion; when any one of the high sampling rate change sampling value differential quick-trip protection sub-criterion, the normal sampling rate half-wave Fourier differential quick-trip protection sub-criterion, and the normal sampling rate full-wave Fourier differential quick-trip protection sub-criterion is met, it is determined that the differential quick-trip protection criterion is met.

3. The method according to claim 2, characterized in that The high sampling rate variation sampling value differential quick-trip protection sub-criterion is valid within 10ms after the protection starting element is started. The high sampling rate variation sampling value differential quick-trip protection sub-criterion includes: ， ， in, is the differential current sampling value of the current differential current sampling point k and the differential current sampling value of the kNth sampling point The difference; s is the preset multiple; is the rated current; N is the data window length; when the above formula is satisfied, it is determined that the high sampling rate variation sampling value differential quick-break protection sub-criterion is satisfied.

4. A fast differential quick-break protection system for a transformer, characterized in that: The system comprises: A data acquisition unit is used to obtain the differential current sampling values ​​of the current differential current sampling point and the N-1 sampling points before it; a first judgment unit, configured to judge whether a differential quick-trip protection criterion is met based on the differential current sampling values ​​at the current differential current sampling point and the differential current sampling values ​​at the N-1 sampling points before the current differential current sampling point, and obtain a first judgment result; A second judgment unit is used to judge whether a differential current abnormally large number locking criterion is met based on the differential current sampling values ​​of the current differential current sampling point and the N-1 sampling points before it, and obtain a second judgment result; a third judgment unit, configured to, when CT saturation locking access is set, judge whether CT saturation locking is satisfied and obtain a third judgment result; an action output unit, configured to, when the first judgment result indicates that the differential quick-trip protection criterion is satisfied, and the second judgment result indicates that the differential current abnormally large number blocking criterion is not satisfied, and the third judgment result indicates that the CT saturation blocking criterion is not satisfied, perform a protection action output; The second judgment unit judges whether the differential current sampling value satisfies the abnormally large differential current blocking criterion based on the differential current sampling value at the current differential current sampling point and the differential current sampling values ​​at the N-1 sampling points before the current differential current sampling point, and obtains the second judgment result, including: Step 1, initialize m=1; Step 2: Select m sample value data with the largest absolute value among N sample value data as the first data set, and the remaining data as the second data set; Step 3, averaging the absolute values ​​of all sampled data in the second data set, and calculating the ratio of the average value to the maximum absolute value in the sampled data; Step 4: If the ratio is less than or equal to the preset threshold, and the current differential current sampling point is a sampling point corresponding to the data in the first data set, then it is determined that there are m abnormally large points in the data window, and the current differential current sampling point is an abnormally large point, and the second judgment result is determined to satisfy the abnormally large differential current blocking criterion; if the ratio is less than or equal to the preset threshold, and the current differential current sampling point is not a sampling point corresponding to the data in the first data set, then it is determined that there are m abnormally large points in the data window, and the current differential current sampling point is not an abnormally large point, and the second judgment result is determined to satisfy the abnormally large differential current blocking criterion; The second judgment unit is further configured to: If the ratio is greater than a preset threshold, determine whether m<M is satisfied. If so, update m=m+1 and return to step 2 to recalculate. If not, determine that there are no abnormally large points in the data window, and determine that the second judgment result does not meet the abnormally large differential flow locking criterion; where M is the set maximum number of cycles.

5. The system according to claim 4, characterized in that The differential quick-trip protection criterion includes: a high sampling rate change sampling value differential quick-trip protection sub-criterion, a normal sampling rate half-wave Fourier differential quick-trip protection sub-criterion, and a normal sampling rate full-wave Fourier differential quick-trip protection sub-criterion; when any one of the high sampling rate change sampling value differential quick-trip protection sub-criterion, the normal sampling rate half-wave Fourier differential quick-trip protection sub-criterion, and the normal sampling rate full-wave Fourier differential quick-trip protection sub-criterion is met, it is determined that the differential quick-trip protection criterion is met.

6. The system according to claim 5, characterized in that The high sampling rate variation sampling value differential quick-trip protection sub-criterion is valid within 10ms after the protection starting element is started. The high sampling rate variation sampling value differential quick-trip protection sub-criterion includes: ， ， in, is the differential current sampling value of the current differential current sampling point k and the differential current sampling value of the kNth sampling point The difference; s is the preset multiple; is the rated current; N is the data window length; when the above formula is satisfied, it is determined that the high sampling rate variation sampling value differential quick-break protection sub-criterion is satisfied.

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