CN113690859B - Starting and acting method and system for power grid differential protection - Google Patents

Starting and acting method and system for power grid differential protection Download PDF

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CN113690859B
CN113690859B CN202110892722.2A CN202110892722A CN113690859B CN 113690859 B CN113690859 B CN 113690859B CN 202110892722 A CN202110892722 A CN 202110892722A CN 113690859 B CN113690859 B CN 113690859B
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dtw
value
differential protection
starting
current
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CN113690859A (en
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吴通华
濮宏飞
姚刚
洪丰
郑小江
王威威
李新东
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Nari Technology Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured

Abstract

The invention discloses a starting and acting method and a system for power grid differential protection, wherein the method comprises the steps of carrying out DTW calculation on a normalized current sampling sequence, and carrying out unitization processing on an obtained DTW value; aiming at the DTW value after the unitization processing, calculating a starting value of a starting method and a setting value of an action method by combining a short window algorithm; judging whether a fault occurs or not and whether the fault is in a line area or not based on the calculated starting value and setting value; if the judgment result is that the power grid line has a fault, starting differential protection; if the judgment result is that the circuit area is in fault, the differential protection is controlled to immediately output an action signal. The invention can reliably start differential protection when different types of faults occur at different positions of a power grid line, and the system can greatly reduce the oscillation amplitude of the DTW distance waveform of the action method in an alternating current system and enable the differential protection to rapidly output an action signal.

Description

Starting and acting method and system for power grid differential protection
Technical Field
The invention belongs to the technical field of differential protection, and particularly relates to a starting and acting method and system of power grid differential protection.
Background
With the massive access of distributed new energy, the traditional staged current protection of the power distribution network line is not suitable any more. In order to effectively identify faults inside and outside the area and improve the power supply reliability of a power grid, a differential protection principle needs to be introduced and a communication channel capable of meeting the requirement of protecting data transmission is assisted.
At present, both optical fiber and 5G communication technologies can be used for differential protection in data transmission performance. Compared with optical fiber communication, the base station in the 5G network is low in laying difficulty and flexible in site selection, so that the 5G communication is selected as a protection channel, the differential protection is promoted, and the reliability of power grid protection under the condition of high-proportion new energy access is improved. However, to use 5G communication as a data channel for differential protection, the problems of data synchronization and packet loss still need to be solved.
Differential protection based on a Dynamic Time Warping (DTW) algorithm needs to calculate a DTW distance between two sets of time sequences. When the problem of sampling point synchronization error increase or data loss occurs, the DTW distance is less affected, and the DTW algorithm weakens the adverse effect brought by 5G communication in principle.
Journal article "a differential protection algorithm for resisting communication delay and packet loss" provides a differential protection action method based on a DTW algorithm by using a DTW distance between phase currents on two sides. Journal article "positioning method for small current grounding fault section based on dynamic time bending distance" plans a differential protection action method through the DTW distance between the zero sequence currents on both sides, and can effectively detect the small current grounding fault. The Chinese patent application with the application number of 202010369821.8 discloses a method for calculating a DTW value by utilizing a normalized current sequence, which can effectively identify a single-phase earth fault. In the method in the prior art, the length of the data window is greater than or equal to one power frequency period, and in an alternating current system, if the length of the data window is reduced, extreme values occur in the DTW distance near the zero crossing point and the peak valley value of the current, and the corresponding waveform greatly oscillates. In addition, the protection starting method based on the DTW algorithm is not researched in the methods.
Disclosure of Invention
In order to solve the problems, the invention provides a starting and acting method and a system of power grid differential protection, which can realize the function of reliably starting the differential protection when different types of faults occur at different positions of a power grid line, and the system can greatly reduce the oscillation amplitude of a DTW distance waveform of an acting method in an alternating current system and enable the differential protection to rapidly output an acting signal.
In order to achieve the technical purpose and achieve the technical effects, the invention is realized by the following technical scheme:
in a first aspect, the present invention provides a method for starting and operating a power grid differential protection, including:
performing DTW calculation on the normalized current sampling sequence, and performing unitization processing on the obtained DTW value;
aiming at the DTW value after the unitization processing, calculating a starting value of a starting method and a setting value of an action method by combining a short window algorithm;
judging whether a fault occurs and whether the fault is in a line area or not based on the calculated starting value and setting value;
if the judgment result is that the power grid line has a fault, starting differential protection;
if the judgment result is that the circuit area is in fault, the differential protection is controlled to immediately output an action signal.
Optionally, the normalized current sampling sequence is obtained by:
after receiving a phase current sampling sequence of an opposite terminal, processing the phase current sampling sequence of the opposite terminal by using a substitution processing method, wherein the substitution processing method is to use previous effective sampling point data to substitute current abnormal sampling point data;
and selecting two current sampling sequences from all the phase current sampling sequences and the zero sequence current sampling sequences at two ends of the line, and normalizing the two current sampling sequences.
Optionally, the DTW calculation specifically includes:
intercepting the last T of the two normalized current sampling sequences 0 Sampling point data;
and calculating the DTW value between the sampling points of the intercepted parts of the two current sampling sequences by using a DTW algorithm.
Optionally, the calculation formula adopted by the alternative processing method is as follows:
I i '＝I i-1 ,i＝2,3,4...
wherein, I i-1 Is the amplitude of the current at the I-1 th effective sampling point i ' is the magnitude of the current at the ith sample point after the substitution process.
Optionally, the DTW value is calculated by the following formula:
D ij ＝d ij +min{D i,j-1 ,D i-1,j ,D i-1,j-1 }
wherein d is ij Indicating the ohm between the current amplitude of the ith sampling point of the first current sampling sequence and the current amplitude of the jth sampling point of the second current sampling sequenceA distance in degrees; d ij Representing the ith-T of a sequence of samples taken by the first current 0 +1，i-T 0 +2, \8230, the current amplitudes at the i sample points and j-T of the second current sample sequence 0 +1，j-T 0 +2, \8230, DTW values between the current amplitudes of the j sample points.
Optionally, the formula used for unitizing the obtained DTW value is:
Figure BDA0003196583120000021
d is a DTW actual accumulated value between the two current sampling sequences;
Figure BDA0003196583120000022
is the DTW value after the unit.
Optionally, the calculation formula of the short window algorithm is:
Figure BDA0003196583120000023
Figure BDA0003196583120000031
wherein the content of the first and second substances,
Figure BDA0003196583120000032
for the first time after optimization by the short window algorithm
Figure BDA0003196583120000033
The phase DTW differential quantity is the DTW differential quantity at two sampling points separated by 1/4 of power frequency period
Figure BDA0003196583120000034
Average value of (d);
Figure BDA0003196583120000035
for the first time after optimization by the short window algorithm
Figure BDA0003196583120000036
DTW braking amount of phase, which is DTW braking amount
Figure BDA0003196583120000037
Average value of (a); t is the total number of sampling points in a power frequency period, and k is a sampling serial number.
Optionally, the promoter method comprises promoter method 1, promoter method 2, promoter method 3;
the promoter value of the promoter method 1 was calculated by the following steps:
defining a current sampling sequence to be divided into three groups of AB, BC and CA;
for group AB, then:
Figure BDA0003196583120000038
Figure BDA0003196583120000039
Figure BDA00031965831200000310
in the formula (I), the compound is shown in the specification,
Figure BDA00031965831200000311
for the optimized DTW difference between the two phases AB,
Figure BDA00031965831200000312
for the DTW braking quantity between the two phases AB after the optimization of the short window algorithm,
Figure BDA00031965831200000313
and
Figure BDA00031965831200000314
are respectively as
Figure BDA00031965831200000315
And
Figure BDA00031965831200000316
the amount of change in (c); t is the total number of sampling points in a power frequency period, and k is a sampling serial number;
if the starting value is
Figure BDA00031965831200000317
Greater than a threshold value D op1 If yes, the differential protection is started;
for the BC group, then:
Figure BDA00031965831200000318
Figure BDA00031965831200000319
Figure BDA00031965831200000320
in the formula (I), the compound is shown in the specification,
Figure BDA00031965831200000321
for the optimized BC two-phase DTW difference momentum through the short window algorithm,
Figure BDA00031965831200000322
for the optimized BC two-phase DTW braking amount through the short window algorithm,
Figure BDA00031965831200000323
and
Figure BDA00031965831200000324
are respectively as
Figure BDA00031965831200000326
And
Figure BDA00031965831200000325
the amount of change of (c); t is the total number of sampling points in a power frequency period, and k is a sampling serial number;
if the starting value is
Figure BDA00031965831200000327
Greater than a threshold value D op1 If yes, differential protection is started;
for the CA group, then:
Figure BDA00031965831200000328
Figure BDA00031965831200000329
Figure BDA0003196583120000041
in the formula (I), the compound is shown in the specification,
Figure BDA0003196583120000042
for the DTW difference between two phases of CA after the optimization of the short window algorithm,
Figure BDA0003196583120000043
for the DTW braking amount between two phases of CA after the optimization of the short window algorithm,
Figure BDA0003196583120000044
and
Figure BDA0003196583120000045
are respectively as
Figure BDA0003196583120000047
And
Figure BDA0003196583120000046
the amount of change in (c);t is the total number of sampling points in a power frequency period, and k is a sampling serial number;
if the starting value is
Figure BDA0003196583120000048
Greater than a threshold value D op1 If yes, differential protection is started;
promoter method 2 promoter values were calculated by the following steps:
for phase A current, split it into odd sequences I A1 And even sequence I A2 ；
I A1 (k)＝I A (2k-1),k＝1,2...
-I A2 (k)＝-I A (2k),k＝1,2...
Calculation of I A1 and-I A2 DTW value of (1)
Figure BDA0003196583120000049
Calculation of I A1 And I A2 DTW value of
Figure BDA00031965831200000410
Then calculated by short window algorithm
Figure BDA00031965831200000411
And
Figure BDA00031965831200000412
then there are:
Figure BDA00031965831200000413
if the starting value is
Figure BDA00031965831200000414
Greater than a threshold value D op2 If yes, differential protection is started;
for the phase B current, split it into odd sequences I B1 And even sequence I B2 ；
I B1 (k)＝I B (2k-1),k＝1,2...
-I B2 (k)＝-I B (2k),k＝1,2...
Calculation of I B1 and-I B2 DTW value of
Figure BDA00031965831200000415
Calculation of I B1 And I B2 DTW value of
Figure BDA00031965831200000416
Calculated by short window algorithm
Figure BDA00031965831200000417
And
Figure BDA00031965831200000418
then there are:
Figure BDA00031965831200000419
if the starting value is
Figure BDA00031965831200000420
Greater than a threshold value D op2 If yes, the differential protection is started;
for C-phase current, the C-phase current is split into odd sequences I C1 And even sequence I C2 ；
I C1 (k)＝I C (2k-1),k＝1,2...
-I C2 (k)＝-I C (2k),k＝1,2...
Calculation of I C1 and-I C2 DTW value of
Figure BDA00031965831200000421
Calculation of I C1 And I C2 DTW value of
Figure BDA00031965831200000422
Then calculated by short window algorithm
Figure BDA00031965831200000423
And
Figure BDA00031965831200000424
then there are:
Figure BDA00031965831200000425
if the starting value is
Figure BDA00031965831200000426
Greater than a threshold value D op2 If yes, the differential protection is started;
the promoter value for promoter method 3 was calculated by the following steps:
adding the three-phase current sampling sequences and dividing by 3 to obtain zero-sequence current I m0 Is shown by m0 Divided into odd sequences I m01 And even sequence I m02 Calculating I m01 and-I m02 DTW value of
Figure BDA0003196583120000051
Calculating I m01 And I m02 DTW value of
Figure BDA0003196583120000052
Recalculation
Figure BDA0003196583120000053
And
Figure BDA0003196583120000054
then there are:
Figure BDA0003196583120000055
if the starting value is
Figure BDA0003196583120000056
Greater than a threshold value D op3 Then the differential protection is started, m represents one of the two ends of the line, and 0 represents zero sequence.
Optionally, if the determination result is that the power grid line fails, the differential protection is started, specifically:
and if the starting value of any one of the method 1, 2 and 3 is greater than the threshold value, judging that the power grid line has a fault, and starting differential protection.
Optionally, the action method comprises action submethod 1 and action submethod 2;
the setting value of the action sub-method 1 is calculated by the following steps:
obtaining the DTW differential quantity optimized by the short window algorithm by using two current sampling sequences of the same phase at two ends of the line
Figure BDA0003196583120000057
And amount of braking
Figure BDA0003196583120000058
The time interval of two sampling points in the short window algorithm is 1/8 of the power frequency period, and then:
Figure BDA0003196583120000059
if the setting value
Figure BDA00031965831200000510
Greater than a threshold value D op4 Then differential protection is performed, K is the braking coefficient, and K belongs to [0,1]]；
The setting value of the action sub-method 2 is calculated by the following steps:
calculating zero sequence current at two ends of the line, dividing the zero sequence current into odd-even sequences, and obtaining the DTW differential quantity optimized by the short window algorithm
Figure BDA00031965831200000511
And amount of braking
Figure BDA00031965831200000512
The time interval of two sampling points in the short window algorithm is 1/8 of the power frequency period, and then:
Figure BDA00031965831200000513
if the setting value
Figure BDA00031965831200000514
Greater than a threshold value D op5 Then, differential protection is performed.
Optionally, if the determination result is that there is an internal fault of the line area, controlling the differential protection to immediately output the action signal, specifically:
if the setting value of any one of the sub-methods 1 and 2 is larger than the threshold value, the occurrence of the fault in the line area is judged, and the differential protection immediately acts.
In a third aspect, the present invention provides a system for starting and operating a power grid differential protection, including a storage medium and a processor;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the method according to any one of the first aspects.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a starting and acting method and a system of power grid differential protection, which can realize the function of reliably starting the differential protection when different types of faults occur at different positions of a power grid line, and the system can greatly reduce the oscillation amplitude of a DTW distance waveform of an acting method in an alternating current system and enable the differential protection to rapidly output an acting signal.
The short window algorithm can effectively solve the problem that the waveform of the DTW algorithm in the alternating current system greatly vibrates during short window calculation, and realizes differential protection setting based on the DTW algorithm, so that the required data storage capacity is small.
The substitution processing method can greatly reduce the influence of the DTW algorithm on the problem sampling points. When continuous multipoint data loss occurs or frames are lost due to check errors, differential protection can be prevented from malfunction by increasing the threshold value, and reliability is improved.
Drawings
In order that the present disclosure may be more readily and clearly understood, reference is now made to the following detailed description of the present disclosure taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a flow diagram of a differential protection system comprising submethods 1 and 3 of the startup method and the method of action;
FIG. 2 is a flow chart of the differential protection system consisting of submethods 2 and 3 of the startup method and the action method;
FIG. 3 is a schematic diagram of a power distribution network model in which an embodiment is implemented;
FIG. 4 (a) shows a sub-method 1 of the action method without introducing the short window algorithm at f 2 A setting value waveform curve when an ABCG fault occurs;
FIG. 4 (b) shows a sub-method 1 of the action method without introducing the short window algorithm at f 2 A normalized current waveform curve when an ABCG fault occurs;
FIG. 5 is a sub-method 1 of the startup method
Figure BDA0003196583120000061
And
Figure BDA0003196583120000062
at f 4 A waveform curve when an AG fault occurs;
FIG. 6 shows the startup value at f in submethod 2 of the startup method 3 A wave curve when an AB fault occurs;
FIG. 7 is a submethod 3 of the startup method at f 2 A waveform curve when an AG1000 omega fault occurs;
FIG. 8 shows a sub-method 1 of the operation method in the normal state of 5G communication, in which the setting value is f under the introduction and non-introduction of the short window algorithm 4 Waveform when an AB fault occurs;
FIG. 9 shows that the setting value in FIG. 8 is f when continuous 3-point data packet loss occurs 2 A waveform at which an ABG fault occurs;
FIG. 10 shows that the setting values in FIG. 8 are f when continuous 12-point data packet loss occurs 6 Waveform of AB fault；
FIG. 11 shows a sub-method 2 of the method after the short window algorithm is introduced when the 5G communication is normal and continuous 3-point data packet loss occurs, at f 1 At ABG failure.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of the invention.
The following detailed description of the principles of the invention is provided in connection with the accompanying drawings.
Example 1
The embodiment of the invention provides a starting and acting method of power grid differential protection, which specifically comprises the following steps:
performing DTW calculation on the normalized current sampling sequence, and performing unitization processing on the obtained DTW value;
aiming at the DTW value after the unitization processing, calculating a starting value of a starting method and a setting value of an action method by combining a short window algorithm;
judging whether a fault occurs and whether the fault is in a line area or not based on the calculated starting value and setting value;
if the judgment result is that the power grid line has a fault, starting differential protection;
if the judgment result is that the circuit area is in fault, the differential protection is controlled to immediately output an action signal.
Referring to fig. 1-2, the detailed description of the startup and operation method in the embodiment of the present invention is provided in conjunction with the specific implementation process and the power distribution network model in fig. 3.
Step 1: sampling three-phase current values at two ends of a line in real time under a certain sampling frequency, and sending an obtained sampling sequence to a sampling selection device at one end by using a 5G network;
step 2: after receiving the current sampling sequence of the opposite end, carrying out normalization processing on each current sequence, wherein the effect is shown in fig. 4 (b), the current waveform amplitude values are all in the interval of [0,1], a substitution processing method for replacing the current abnormal sampling point with the previous effective sampling point data is used for processing the data packet loss problem, and the lengths of 2 sampling sequences in the subsequent DTW calculation are ensured to be equal; the calculation formula of the alternative processing method is as follows:
I′ i ＝I i-1 ,i＝2,3,4...
wherein, I i-1 Is the amplitude of the current at the I-1 th effective sampling point i ' is the magnitude of the current at the ith sample point after the substitution process.
And step 3: respectively intercepting the last T of 2 sampling sequences required by the subsequent DTW calculation according to the requirements of the differential protection starting and action method 0 Calculating corresponding DTW values by using short window algorithm, as shown in FIG. 6, FIG. 8, FIG. 9, FIG. 10 and FIG. 11, and then performing unitization processing on the obtained DTW values, and listing the starting values of the starting method and the setting values of the action method; the DTW calculation specifically comprises the steps of firstly calculating Euclidean distances d between sampling points in the intercepted parts of 2 current sampling sequences ij Then to d ij Performing regular accumulation to obtain DTW value D ij ：
D ij ＝d ij +min{D i,j-1 ,D i-1,j ,D i-1,j-1 }
Wherein, d ij Representing the Euclidean distance between the current amplitude of the ith sampling point of the first current sampling sequence and the current amplitude of the jth sampling point of the second current sampling sequence; d ij Representing the ith-T sequence sampled by the first current 0 +1，i-T 0 +2, \8230, the current amplitudes of the i sample points and j-T of the second current sample sequence 0 +1，j-T 0 +2, \8230, the DTW values between the current amplitudes of the j sample points.
The short window algorithm is characterized in that the peak-valley value and the zero crossing point of the fault current occur at intervals, the distance between the front and the back is about 1/4 power frequency periods, and the maximum value and the minimum value of the DTW waveform also occur at time intervals of about 1/4 power frequency periods. Therefore, the waveform oscillation can be reduced by a method of first obtaining the DTW values after unitization at two sampling points near the maximum value and the minimum value, and then obtaining the average value of the DTW values:
Figure BDA0003196583120000081
Figure BDA0003196583120000082
wherein the content of the first and second substances,
Figure BDA0003196583120000083
for the first time after optimization by the short window algorithm
Figure BDA0003196583120000084
The DTW difference of the phase is the DTW difference at two sampling points separated by 1/4 of the power frequency period
Figure BDA0003196583120000085
Average value of (a);
Figure BDA0003196583120000086
for the first time after being optimized by a short window algorithm
Figure BDA0003196583120000087
DTW braking amount of phase, which is DTW braking amount
Figure BDA0003196583120000088
Average value of (d); t is the total number of sampling points in a power frequency period, and k is a sampling serial number.
The formula used for unitizing the obtained DTW values is as follows:
Figure BDA0003196583120000089
d is a DTW actual accumulated value between the two current sampling sequences;
Figure BDA00031965831200000810
the DTW values are normalized.
And 4, step 4: as for the starting method, as shown in fig. 5, 6 and 7, if the starting method includes a promoter sub method 1, a promoter sub method 2 and a promoter sub method 3, when the starting value of any one sub method is greater than a threshold value, a fault occurs in a power grid line, and differential protection is started (the starting method of the local terminal starts the differential protection of the local terminal, and the starting method of the opposite terminal starts the differential protection of the opposite terminal);
and 5: as for the operation method, as shown in fig. 8, 9, 10 and 11, if the setting value of any one of the submethods is greater than the threshold value in the operation submethod 1 and the operation submethod 2, a fault in the line area occurs, and the differential protection immediately sends out an operation signal;
and 6: if packet loss occurs to the peer-to-peer data and the number of consecutive packet loss does not exceed 3, as shown in fig. 8, 9 and 11, the threshold values of 2 sub-methods of the action method may be increased to ensure that the action method does not malfunction when the action method fails outside the area; if the number of consecutive lost packets exceeds 3, as shown in fig. 10, the adjustment threshold value cannot be set reliably, so that the differential protection needs to be locked for a short time to prevent malfunction.
As shown in fig. 6, 8, 9, 10 and 11, the starting method sub-method 2 and the operation method sub-method 2 of the present invention calculate the DTW value and then calculate the starting value and the setting value by the short window algorithm.
The starting method comprises a starter method 1, as shown in fig. 5, dividing a three-phase current sequence at the m side of a home terminal into three groups of AB, BC and CA;
for group AB, then:
Figure BDA0003196583120000091
Figure BDA0003196583120000092
Figure BDA0003196583120000093
in the formula (I), the compound is shown in the specification,
Figure BDA0003196583120000094
for the DTW difference between the two phases AB after optimization by the short window algorithm,
Figure BDA0003196583120000095
for the optimized DTW braking amount of the two AB phases through the short window algorithm,
Figure BDA0003196583120000096
and
Figure BDA0003196583120000097
are respectively as
Figure BDA0003196583120000098
And
Figure BDA0003196583120000099
the amount of change in (c);
t is the total number of sampling points in a power frequency period, and k is a sampling serial number;
if the starting value is
Figure BDA00031965831200000910
Greater than a threshold value D op1 If yes, differential protection is started;
for the BC group, then:
Figure BDA00031965831200000911
Figure BDA00031965831200000912
Figure BDA00031965831200000913
in the formula (I), the compound is shown in the specification,
Figure BDA00031965831200000914
for the optimized BC two-phase DTW difference momentum through the short window algorithm,
Figure BDA00031965831200000915
for the optimized BC two-phase DTW braking amount through the short window algorithm,
Figure BDA00031965831200000916
and
Figure BDA00031965831200000917
are respectively as
Figure BDA00031965831200000918
And
Figure BDA00031965831200000919
the amount of change of (c);
t is the total number of sampling points in a power frequency period, and k is a sampling serial number;
if the starting value is
Figure BDA00031965831200000920
Greater than a threshold value D op1 If yes, differential protection is started;
for the CA group, then:
Figure BDA00031965831200000921
Figure BDA00031965831200000922
Figure BDA00031965831200000923
in the formula (I), the compound is shown in the specification,
Figure BDA00031965831200000924
for the DTW difference between two phases of CA after the optimization of the short window algorithm,
Figure BDA00031965831200000925
for the optimized DTW braking amount between two phases of CA by the short window algorithm,
Figure BDA00031965831200000926
and
Figure BDA00031965831200000927
are respectively as
Figure BDA00031965831200000928
And
Figure BDA00031965831200000929
the amount of change in (c); t is the total number of sampling points in a power frequency period, and k is a sampling serial number;
if the starting value is
Figure BDA00031965831200000930
Greater than a threshold value D op1 Then the differential protection is enabled.
The starting method comprises a starter method 2, as shown in fig. 6, splitting a three-phase current sequence at one end into odd-even sequences respectively;
for phase A current, split it into odd sequences I A1 And even sequence I A2 ；
I A1 (k)＝I A (2k-1),k＝1,2...
-I A2 (k)＝-I A (2k),k＝1,2...
Calculating I A1 and-I A2 DTW value of (1)
Figure BDA0003196583120000101
Calculating I A1 And I A2 DTW value of (1)
Figure BDA0003196583120000102
Calculated by short window algorithm
Figure BDA0003196583120000103
And
Figure BDA0003196583120000104
then there are:
Figure BDA0003196583120000105
if the starting value is
Figure BDA0003196583120000106
Greater than a threshold value D op2 If yes, differential protection is started;
for the phase B current, split it into odd sequences I B1 And even sequence I B2 ；
I B1 (k)＝I B (2k-1),k＝1,2...
-I B2 (k)＝-I B (2k),k＝1,2...
Calculating I B1 and-I B2 DTW value of
Figure BDA0003196583120000107
Calculating I B1 And I B2 DTW value of (1)
Figure BDA0003196583120000108
Calculated by short window algorithm
Figure BDA0003196583120000109
And
Figure BDA00031965831200001010
then there are:
Figure BDA00031965831200001011
if the starting value is
Figure BDA00031965831200001012
Greater than a threshold value D op2 Then make a differential motionStarting protection;
for C-phase current, the C-phase current is split into odd sequences I C1 And even sequence I C2 ；
I C1 (k)＝I C (2k-1),k＝1,2...
-I C2 (k)＝-I C (2k),k＝1,2...
Calculation of I C1 and-I C2 DTW value of
Figure BDA00031965831200001013
Calculation of I C1 And I C2 DTW value of
Figure BDA00031965831200001014
Calculated by short window algorithm
Figure BDA00031965831200001015
And
Figure BDA00031965831200001016
then there are:
Figure BDA00031965831200001017
if the starting value is
Figure BDA00031965831200001018
Greater than a threshold value D op2 Then the differential protection is enabled.
The starting method comprises a starter method 3, as shown in fig. 7, taking the m side of the line as an example, calculating the zero sequence current I of the m side m0 A first reaction of m0 Divided into odd sequences I m01 And even sequence I m02 Calculating I m01 and-I m02 DTW value of
Figure BDA00031965831200001019
Calculation of I m01 And I m02 DTW value of
Figure BDA00031965831200001020
Recalculation
Figure BDA00031965831200001021
And
Figure BDA00031965831200001022
then there are:
Figure BDA00031965831200001023
if the left starting value is larger than the threshold value D op3 Then the differential protection is started.
The action method comprises an action submethod 1, as shown in fig. 8, 9 and 10, and is characterized in that two current sequences of the same phase at two ends of a line are used for obtaining a DTW difference quantity and a braking quantity, and then a short window algorithm is used for obtaining the DTW difference quantity and the braking quantity
Figure BDA0003196583120000111
And
Figure BDA0003196583120000112
the time interval of two sampling points in the short window algorithm is 1/8 of the power frequency period. Then there are:
Figure BDA0003196583120000113
if the upper left setting value is larger than the threshold value D op4 Then the differential protection outlet action signal.
The action method comprises an action submethod 2, as shown in fig. 11, calculating zero sequence current at two ends of the line and dividing the zero sequence current into odd-even sequences, calculating DTW difference and braking quantity, and calculating by using a short window algorithm
Figure BDA0003196583120000114
And
Figure BDA0003196583120000115
the time interval of two sampling points in the short window algorithm is 1/8 of the power frequency period. Then there are:
Figure BDA0003196583120000116
if the upper left setting value is larger than the threshold value D op5 Then the differential protection outlet action signal.
As shown in fig. 5, in steady state, the start value of the sub-method 1 of the start method is a very small positive number and is basically stable, when the line fails, at least one of the two DTW values in the maximum function corresponding to the start value will increase rapidly, and the threshold value D is taken op1 0.003 if the starting value is greater than D op1 Then the differential protection is enabled. Submethod 1 of the startup method can start differential protection within 2ms after the occurrence of a fault and can be used to detect various types of faults other than a high-resistance ground fault.
As shown in FIG. 6, in sub-method 2 of the start-up method, when a line fault occurs, the start-up value increases rapidly, and the threshold value D is taken op2 Is 0.028, if the starting value is greater than D op2 Then the differential protection is enabled. Sub-method 2 of the start-up method can start differential protection within 8ms after the occurrence of a fault and can be used to detect various types of faults other than a single-phase earth fault.
As shown in fig. 7, sub-method 3 of the start-up method also increases the start-up value rapidly when a line fault occurs, taking threshold value D op3 Is 0.02, if the starting value is greater than D op3 Then the differential protection is started. Submethod 2 of the startup method can start differential protection within 2ms after the fault occurs, can be used to detect asymmetric ground faults, and is used as a complement to submethods 1 and 2 of the startup method.
As shown in fig. 8, 9, and 10, in the submethod 1 of the operation method, when an out-of-range fault occurs, the setting value is lower than the threshold value, and the differential protection does not operate. For the faults in the area, a threshold value D is taken except that the high-resistance grounding fault cannot be set op4 And the packet loss is 0.01, and the differential protection can output the action signal within 6.75ms as long as the packet loss is not more than 3 continuously. If the number of the continuous packet loss exceeds 3, the operation speed gradually becomes slow.
As shown in fig. 11, if there are no more than 3 consecutive lost packets, sub-method 2 of the action method can adjust all asymmetric ground faults and can export the action signal within 6.75ms as well.
Example 2
Based on the same inventive concept as embodiment 1, the embodiment of the invention provides a starting and acting system for power grid differential protection, which comprises a storage medium and a processor;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the method of any of embodiment 1.
The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are given by way of illustration of the principles of the present invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention, and such changes and modifications are within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (11)

1. A starting and action method for power grid differential protection is characterized by comprising the following steps:
performing DTW calculation on the normalized current sampling sequence, and performing unitization processing on the obtained DTW value;
aiming at the DTW value after the unitization processing, calculating a starting value of a starting method and a setting value of an action method by combining a short window algorithm;
judging whether a fault occurs and whether the fault is in a line area or not based on the calculated starting value and setting value;
if the judgment result is that the power grid line has a fault, starting differential protection;
if the judgment result is that the circuit area is in fault, controlling the differential protection to immediately output an action signal;
the starting method comprises a promoter method 1, a promoter method 2 and a promoter method 3;
the promoter value of the promoter method 1 was calculated by the following steps:
defining a current sampling sequence to be divided into three groups of AB, BC and CA;
for group AB, then:
Figure FDA0003962815490000011
Figure FDA0003962815490000012
Figure FDA0003962815490000013
in the formula (I), the compound is shown in the specification,
Figure FDA0003962815490000014
for the optimized DTW difference between the two phases AB,
Figure FDA0003962815490000015
for the optimized DTW braking amount of the two AB phases through the short window algorithm,
Figure FDA0003962815490000016
and
Figure FDA0003962815490000017
are respectively as
Figure FDA0003962815490000018
And
Figure FDA0003962815490000019
the amount of change in (c); t is the total number of sampling points in a power frequency period, and k is a sampling serial number;
if the starting value
Figure FDA00039628154900000110
Greater than a threshold value D op1 If yes, differential protection is started;
for the BC group, then:
Figure FDA00039628154900000111
Figure FDA00039628154900000112
Figure FDA00039628154900000113
in the formula (I), the compound is shown in the specification,
Figure FDA00039628154900000114
for the optimized BC two-phase DTW difference momentum through the short window algorithm,
Figure FDA00039628154900000115
for the optimized BC two-phase DTW braking amount through the short window algorithm,
Figure FDA00039628154900000116
and
Figure FDA00039628154900000117
are respectively as
Figure FDA00039628154900000118
And
Figure FDA00039628154900000119
the amount of change of (c); t is the total number of sampling points in a power frequency period, and k is a sampling serial number;
if the starting value is
Figure FDA00039628154900000120
Greater than a threshold value D op1 If yes, differential protection is started;
for the CA group, then:
Figure FDA00039628154900000121
Figure FDA0003962815490000021
Figure FDA0003962815490000022
in the formula (I), the compound is shown in the specification,
Figure FDA0003962815490000023
for the DTW difference between two phases of CA after the optimization of the short window algorithm,
Figure FDA0003962815490000024
for the DTW braking amount between two phases of CA after the optimization of the short window algorithm,
Figure FDA0003962815490000025
and
Figure FDA0003962815490000026
are respectively as
Figure FDA0003962815490000027
And
Figure FDA0003962815490000028
the amount of change of (c); t is the total number of sampling points in a power frequency period, and k is a sampling serial number;
if the starting value
Figure FDA0003962815490000029
Greater than a threshold value D op1 If yes, differential protection is started;
promoter method 2 promoter values were calculated by the following steps:
for the A-phase current, the A-phase current is split into an odd sequence I A1 And even sequence I A2 ；
I A1 (k)＝I A (2k-1),k＝1,2...
-I A2 (k)＝-I A (2k),k＝1,2...
Calculating I A1 and-I A2 DTW value of (1)
Figure FDA00039628154900000210
Calculation of I A1 And I A2 DTW value of
Figure FDA00039628154900000211
Then calculated by short window algorithm
Figure FDA00039628154900000212
And
Figure FDA00039628154900000213
then there are:
Figure FDA00039628154900000214
if the starting value is
Figure FDA00039628154900000215
Greater than a threshold value D op2 If yes, the differential protection is started;
for the phase B current, split it into odd sequences I B1 And even sequence I B2 ；
I B1 (k)＝I B (2k-1),k＝1,2...
-I B2 (k)＝-I B (2k),k＝1,2...
Calculation of I B1 and-I B2 DTW value of
Figure FDA00039628154900000216
Calculation of I B1 And I B2 DTW value of (1)
Figure FDA00039628154900000217
Calculated by short window algorithm
Figure FDA00039628154900000218
And
Figure FDA00039628154900000219
then there are:
Figure FDA00039628154900000220
if the starting value is
Figure FDA00039628154900000221
Greater than a threshold value D op2 If yes, differential protection is started;
for the C-phase current, split it into odd sequences I C1 And even sequence I C2 ；
I C1 (k)＝I C (2k-1),k＝1,2...
-I C2 (k)＝-I C (2k),k＝1,2...
Calculating I C1 and-I C2 DTW value of
Figure FDA00039628154900000222
Calculating I C1 And I C2 DTW value of
Figure FDA00039628154900000223
Then calculated by short window algorithm
Figure FDA00039628154900000224
And
Figure FDA00039628154900000225
then there are:
Figure FDA00039628154900000226
if the starting value is
Figure FDA00039628154900000227
Greater than a threshold value D op2 If yes, the differential protection is started;
the promoter value for promoter method 3 was calculated by the following steps:
adding the three-phase current sampling sequences and dividing by 3 to obtain zero-sequence current I m0 Is shown by m0 Divided into odd sequences I m01 And even sequence I m02 Calculating I m01 and-I m02 DTW value of (1)
Figure FDA0003962815490000031
Calculating I m01 And I m02 DTW value of
Figure FDA0003962815490000032
Recalculation
Figure FDA0003962815490000033
And
Figure FDA0003962815490000034
then there are:
Figure FDA0003962815490000035
if the starting value is
Figure FDA0003962815490000036
Greater than a threshold value D op3 Then the differential protection is started, m represents one of the two ends of the line, and 0 represents zero sequence.
2. A method according to claim 1, wherein the normalized current sampling sequence is obtained by:
after receiving a phase current sampling sequence of an opposite end, processing the phase current sampling sequence of the opposite end by using a substitution processing method, wherein the substitution processing method is to use previous effective sampling point data to substitute current abnormal sampling point data;
and selecting two current sampling sequences from all the phase current sampling sequences and the zero sequence current sampling sequences at two ends of the line, and normalizing the two current sampling sequences.
3. A method according to claim 2, wherein the method further comprises: the DTW calculation specifically comprises the following steps:
intercepting the last T of the two normalized current sampling sequences 0 Sampling point data;
and calculating the DTW value between the sampling points of the intercepted parts of the two current sampling sequences by using a DTW algorithm.
4. A method according to claim 3, wherein the DTW value is processed in units of the formula:
Figure FDA0003962815490000037
d is a DTW actual accumulated value between the two current sampling sequences;
Figure FDA0003962815490000038
is the DTW value after the unit.
5. The method for starting and operating the power grid differential protection according to claim 2, wherein the substitution processing method adopts a calculation formula as follows:
I i '＝I i-1 ,i＝2,3,4...
wherein, I i-1 The amplitude of the current at the I-1 th effective sampling point, I i ' is the magnitude of the current at the ith sample point after the substitution process.
6. The method for starting and operating grid differential protection according to claim 1, wherein the DTW value is calculated by the formula:
D ij ＝d ij +min{D i,j-1 ,D i-1,j ,D i-1,j-1 }
wherein, d ij Representing the Euclidean distance between the current amplitude of the ith sampling point of the first current sampling sequence and the current amplitude of the jth sampling point of the second current sampling sequence; d ij Representing the ith-T of a sequence of samples taken by the first current 0 +1，i-T 0 +2, \8230, the current amplitudes of the i sample points and j-T of the second current sample sequence 0 +1，j-T 0 +2, \8230, DTW values between the current amplitudes of the j sample points.
7. The method for starting and operating the power grid differential protection according to claim 1, wherein the short window algorithm has a calculation formula as follows:
Figure FDA0003962815490000041
Figure FDA0003962815490000042
wherein the content of the first and second substances,
Figure FDA0003962815490000043
is a warpOptimized by short window algorithm
Figure FDA0003962815490000044
The DTW difference of the phase is the DTW difference at two sampling points separated by 1/4 of the power frequency period
Figure FDA0003962815490000045
Average value of (d);
Figure FDA0003962815490000046
for the first time after optimization by the short window algorithm
Figure FDA0003962815490000047
DTW braking amount of phase, which is DTW braking amount
Figure FDA0003962815490000048
Average value of (a); t is the total number of sampling points in a power frequency period, and k is a sampling serial number. .
8. A method according to claim 1, wherein the method comprises the steps of: if the judgment result is that the power grid line fails, starting differential protection, specifically:
and if the starting value of any one of the promoter method 1, the promoter method 2 and the promoter method 3 is greater than the threshold value, judging that the power grid line has a fault, and starting differential protection.
9. A method according to claim 1, wherein the method further comprises the steps of: the action method comprises an action submethod 1 and an action submethod 2;
the setting value of the action sub-method 1 is calculated by the following steps:
two current sampling sequences of the same phase at two ends of the line are used for solving the DTW differential quantity optimized by the short window algorithm
Figure FDA0003962815490000049
And amount of braking
Figure FDA00039628154900000410
The time interval of two sampling points in the short window algorithm is 1/8 of the power frequency period, and then:
Figure FDA00039628154900000411
if the setting value
Figure FDA00039628154900000412
Greater than a threshold value D op4 Then differential protection is performed, K is a braking coefficient, and K belongs to [0,1]]；
The setting value of the action sub-method 2 is calculated by the following steps:
calculating zero sequence current at two ends of the line, dividing the zero sequence current into odd-even sequences, and obtaining the DTW differential quantity optimized by the short window algorithm
Figure FDA00039628154900000413
And amount of braking
Figure FDA00039628154900000414
The time interval of two sampling points in the short window algorithm is 1/8 of the power frequency period, and then:
Figure FDA00039628154900000415
if the setting value
Figure FDA0003962815490000051
Greater than a threshold value D op5 The differential protection is performed.
10. The method according to claim 1, wherein if the determination result is an internal fault of the line area, the method controls an immediate exit operation signal of the differential protection, specifically:
if the setting value of any one of the sub-methods 1 and 2 is larger than the threshold value, the occurrence of the fault in the line area is judged, and the differential protection immediately acts.
11. A starting and action system for power grid differential protection is characterized by comprising a storage medium and a processor;
the storage medium is to store instructions;
the processor is configured to operate in accordance with the instructions to perform the method of any of claims 1-10.
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