CN115166340B - Processing method of sampling data of subway direct current protection device - Google Patents
Processing method of sampling data of subway direct current protection device Download PDFInfo
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- CN115166340B CN115166340B CN202211082415.9A CN202211082415A CN115166340B CN 115166340 B CN115166340 B CN 115166340B CN 202211082415 A CN202211082415 A CN 202211082415A CN 115166340 B CN115166340 B CN 115166340B
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R19/12—Measuring rate of change
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The invention provides a method for processing sampling data of a subway direct-current protection device, which comprises the following steps of: step 1: calculating the number of sampling data of an average value according to the pulse width output by the rectifier unit: step 2: calculating the average value of the N sampling data; and step 3: the average value of the current values is used as a reference current value to calculate di/dt. The invention calculates the average value of all sampling data of each pulse wave, and calculates the current change rate by using the average value, thereby not only keeping the intrinsic characteristic of the current corresponding to the sampling moment, but also solving the interference of periodic pulsation on the current change rate calculation and avoiding unreasonable resetting of the protection function.
Description
Technical Field
The invention belongs to the technical field of subway direct current protection, and particularly relates to a processing method of sampling data of a subway direct current protection device.
Background
Before data acquisition, a DC protection device configured in a subway DC traction system converts high voltage and large current into low-voltage and low-current analog quantity which can be processed by an electronic device, such as a DC protection device
10V,4-20mA or 0-150MV. The continuous analog quantity is input into the direct current protection device, filtered, sampled and stored in a corresponding memory, so that the continuous analog quantity can be used for subsequent digital signal processing and protection calculation. The sampling is generally performed by sampling at equal intervals. After the continuous analog quantity is sampled at equal intervals, discrete sampling data become basic data for subsequent calculation of the direct current protection device.
When the direct current protection device samples at equal intervals, the smaller the sampling period T is, the higher the sampling quality is, and the more accurate the description of the continuous analog quantity is. Discrete sampling points tend to form a continuous analog curve as the sampling period tends to be infinitesimal. However, the unlimited reduction of the sampling period T not only increases the unnecessary calculation load of the dc protection device, but also causes problems when the dc protection device calculates the current change rate di/dt.
As is known, the dc voltage output by a rectifying device has a periodic pulsating characteristic. When the sampling period T is smaller than the width of the commutation pulse, the sampled data of the dc protection device also has corresponding periodic pulsation. In order to more accurately retain the original characteristics of the analog current, improve the fault recording precision, improve the event recording efficiency, facilitate the accident process analysis and the like, and combine the current technical level, the sampling period of the current direct current protection device is generally 0.1 millisecond, namely10 points are sampled every millisecond. In the subway, two 12-pulse rectifier units are generally used in parallel to form equivalent 24-pulse rectification, and 35kV or 33kV 50Hz (20 ms cycle) alternating current is rectified into 1500V direct current. Thus, there are 24 pulses in a 20 millisecond power frequency period, corresponding to a pulse width of
. And if the sampling period T is less than the pulse wave width, the sampling data of the subway direct current protection device has periodic pulsation.
The sampling precision can not affect the calculation of most parameters of the subway direct current protection device, such as the calculation of the current variation
In the case of I, because the protection logic calculation is only related to the sampling data at the starting time and the ending time of the protection, the periodic pulsating sampling data at the middle time cannot cause any influence on the protection logic.
When the subway direct current protection device calculates the current change rate di/dt, the protection logic calculation needs to use all sampling data from the starting time to the ending time, and the sampling precision can generate large influence on the calculation. If the sampled data is used directly, a di/dt value that does not conform to the overall trend of change is calculated, and also has a periodic pulsatility.
The physical definition of the current change rate di/dt is the ratio of the current change to the time used, and is a measure of the current change rate, and is of the DC protection device
An important parameter in I + di/dt protection is to distinguish normal fluctuations in traction load current from rapid increases in short-circuit fault current.
When 0.1 millisecond is taken as a sampling period, for the short-circuit current output by the 24-pulse rectifier unit and shown in fig. 1, the corresponding feed line di/dt is shown in fig. 2. The di/dt curve shown in fig. 2, whose periodic pulsatility does not conform to the general trend of the current change rate of the corresponding current curve, is contrary to the objective of using this parameter in the dc protection device. Especially, when the short-circuit current tends to be stable, the change rate of the short-circuit current is smaller and smaller, the periodic pulsation is more and more obvious, the current change rate di/dt at the stage is just an important criterion for protection resetting, the periodic pulsation easily causes unreasonable resetting after protection starting, and the protection function cannot be realized.
Disclosure of Invention
The invention provides a method for processing sampling data of a subway direct current protection device, which aims at the technical problems in the prior art, calculates the average value of all sampling data of each pulse wave, calculates the current change rate by using the average value, not only retains the intrinsic characteristic of the current corresponding to the sampling moment, but also solves the interference of periodic pulsation on the current change rate calculation, and can not cause unreasonable resetting of the protection function.
The technical scheme adopted by the invention is as follows: a processing method of sampling data of a subway direct-current protection device comprises the following steps:
step 1: calculating the number of sampling data taking the average value according to the pulse wave width output by the rectifier unit:
wherein m is the number of rectification pulses of the rectifier unit; t is the sampling interval of the direct current protection device, and the unit is millisecond;
n is the number of the sampled data taking the average value, and the nearest positive integer is selected according to the calculation result;
and 2, step: calculate the average of N sampled data:
wherein N is a sequence forming a group at every N sampling moments;
forming a group of reference moments for every N sampling moments;
the current values corresponding to N sampling moments from the reference moment;
: the average value of the current values corresponding to the N sampling moments of the nth sequence;
and 3, step 3: the average value of the current values was used as a reference current value for di/dt calculation:
wherein, the first and the second end of the pipe are connected with each other,
the average value of the current values corresponding to the N sampling moments of the (N + 1) th sequence is obtained;
di/dt is the current change rate calculated from the average of the current values corresponding to the N sampling instants.
Further, when the rectifier unit outputs multiple pulse wave widths, the number of the rectifier pulses corresponding to the largest pulse wave width is selected as the value of m.
Compared with the prior art, the invention has the beneficial effects that: the invention adopts a pulse wave average value method to process sampling data, wherein the pulse wave width is selected from the maximum rectification pulse wave width generated in the running process of the direct current protection device. The invention uniformly averages the current corresponding to all sampling moments in each pulse period into one value, thereby not only preserving the intrinsic characteristics of the current corresponding to the sampling moments, but also solving the interference of periodic pulse on the calculation of the current change rate and avoiding the unreasonable resetting of the protection function.
Drawings
FIG. 1 is a diagram of output short-circuit current of a 24-pulse rectifier set with a sampling period of 0.1 ms in the prior art;
FIG. 2 is a graph of the rate of change of current resulting from the prior art processing of the short circuit current of FIG. 1;
FIG. 3 is a flow chart of an embodiment of the present invention;
FIG. 4 is a graph of the rate of change of current obtained by processing the short circuit current of FIG. 1 according to the present method of averaging the pulse widths of a 24-pulse rectification in accordance with an embodiment of the present invention;
FIG. 5 is a graph of the output short circuit current of a 12-pulse rectifier set with a sampling period of 0.1 ms;
FIG. 6 is a graph of the rate of change of current obtained by processing the short circuit current of FIG. 5 according to the present method for averaging 12 pulse rectified pulse widths in accordance with an embodiment of the present invention;
FIG. 7 is a graph of the rate of change of current obtained by processing the short circuit current of FIG. 5 according to the present method of averaging the pulse width of a 24-pulse rectification in accordance with an embodiment of the present invention;
fig. 8 is a graph of the rate of change of current resulting from the processing of the short circuit current of fig. 5 by the prior art.
Detailed Description
In order to make the technical solutions of the present invention better understood, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
Example 1
The embodiment of the invention provides a method for processing sampling data of a subway direct-current protection device, which is used for processing a short-circuit current shown in fig. 1, and as shown in fig. 3, the method comprises the following steps:
step 1: calculating the number of the averaged sample data:
wherein, the AC system in China adopts 50Hz power frequency, and the corresponding period is 20 milliseconds.
m is the number of rectification pulses of the rectifier unit, 24 pulses are rectified, and m =24.
T is sampling interval of the direct current protection device, and the unit is millisecond; typically, the sampling period of the dc protection device is 0.1 ms, i.e. T =0.1.
And N is the number of the sampled data with the average value, and the nearest positive integer is selected according to the calculation result, namely N is 8.
Step 2: the average of 8 samples is calculated:
wherein n is a sequence forming a group at every 8 sampling moments;
forming a group of reference moments for every 8 sampling moments;
is from a reference time
The current values corresponding to the first 8 sampling moments;
the average value of the current values corresponding to the 8 sampling moments of the nth sequence is obtained.
Similarly, the 8 sampling instants of the (n + 1) th sequence correspond to the average value of the current values
Is composed of
And calculating the average value of the current values corresponding to the 8 sampling moments of each sequence.
And step 3: the average value of the current values was used as a reference current value for di/dt calculation:
di/dt is a current change rate calculated by an average value of current values corresponding to 8 sampling moments, and a calculation result is shown in fig. 4, so that the current change rate of the output short-circuit current of the 24-pulse rectifier unit is accurately reflected.
Example 2
An embodiment of the present invention provides a method for processing sampling data of a dc protection device for a subway, as shown in fig. 3, the method includes the following steps:
step 1: calculating the number of the averaged sample data:
wherein, the AC system in China adopts 50Hz power frequency, and the corresponding period is 20 milliseconds.
m is the number of rectification pulses of the rectifier unit. Because a single-unit operation mode exists in the subway traction power supply system, the working condition of switching between 24-pulse rectification and 12-pulse rectification is considered according to a larger pulse width, namely the pulse width of 12-pulse rectification output, and m =12.
T is the sampling interval of the direct current protection device, and the unit is millisecond; typically, the sampling period of the dc protection device is 0.1 ms, i.e. T =0.1.
And N is the number of the averaged sample data, and the nearest positive integer is selected according to the calculation result, namely N is 17.
Step 2: the average of 17 samples is calculated:
wherein n is a sequence forming a group at every 17 sampling moments;
forming a group of reference moments for each 17 sampling moments;
to be from a reference time
Current values corresponding to the first 17 sampling moments;
the average value of the current values corresponding to 17 sampling moments of the nth sequence is shown.
Similarly, the 17 th sampling instant of the (n + 1) th sequence corresponds to the average value of the current values
Is composed of
The average of the corresponding current values for 17 sampling instants of each sequence is calculated.
And step 3: the average value of the current values was used as a reference current value for di/dt calculation:
di/dt is the current rate of change calculated from the average of the current values for 17 sampling instants.
By adopting the method, the short-circuit current which is output by the 12-pulse rectifier unit with the sampling period of 0.1 millisecond and is shown in fig. 5 is processed, and the calculation result is shown in fig. 6.
Fig. 7 is a graph of the current change rate obtained by averaging the pulse widths of 24-pulse rectification, i.e., m =24, and performing data processing on the short-circuit current shown in fig. 5 by the above-described method. Fig. 8 is a graph of a current change rate obtained by data processing of the short-circuit current shown in fig. 5 according to a conventional method. As can be seen from the comparison between fig. 6 and fig. 8, fig. 6 can better reflect the current change rate of the 12-pulse rectifier set output short-circuit current.
Under the sampling level of the current subway direct current protection device, before the current change rate di/dt of the protection device is calculated, a pulse wave average value method can be adopted to process sampling data, wherein the pulse wave width should be the maximum rectification pulse wave width generated in the running process of the direct current protection device. The method keeps the intrinsic characteristic of the current corresponding to the sampling moment, solves the interference of the periodic pulse on the calculation of the current change rate, and cannot cause the unreasonable resetting of the protection function.
The present invention has been described in detail with reference to the embodiments, but the description is only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The scope of the invention is defined by the claims. The technical solutions of the present invention or those skilled in the art, based on the teaching of the technical solutions of the present invention, should be considered to be within the scope of the present invention, and all equivalent changes and modifications made within the scope of the present invention or equivalent technical solutions designed to achieve the above technical effects are also within the scope of the present invention.
Claims (2)
1. A processing method of sampling data of a subway direct current protection device is characterized by comprising the following steps: the method comprises the following steps:
step 1: calculating the number of sampling data of an average value according to the pulse width output by the rectifier unit:
wherein m is the number of rectified pulses of the rectifier unit, and m =12 or m =24; t is sampling interval of the direct current protection device, the unit is millisecond, and T is smaller than pulse wave width;
n is the number of the sampled data taking the average value, and the nearest positive integer is selected according to the calculation result;
step 2: calculate the average of N sampled data:
wherein N is a sequence forming a group at every N sampling moments;
forming a group of reference moments for every N sampling moments;
the current values corresponding to N sampling moments from the reference moment;
: the average value of the current values corresponding to the N sampling moments of the nth sequence;
and step 3: the average value of the current values was used as a reference current value for di/dt calculation:
wherein, the first and the second end of the pipe are connected with each other,
the average value of the current values corresponding to the N sampling moments of the (N + 1) th sequence is obtained;
di/dt is the rate of change of current.
2. The method for processing the sampling data of the subway direct-current protection device as claimed in claim 1, wherein: and when the rectifier unit outputs various pulse wave widths, selecting the number of the rectifier pulses corresponding to the maximum pulse wave width as the value of m.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102842890A (en) * | 2012-09-24 | 2012-12-26 | 国电南瑞科技股份有限公司 | Realizing method of current change rate protection |
| CN111856324A (en) * | 2020-07-30 | 2020-10-30 | 中国联合网络通信集团有限公司 | Fault detection method and device for traction network feeder line |
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| JPS5970120A (en) * | 1982-10-13 | 1984-04-20 | 三菱電機株式会社 | Protecting relay |
| JP4841511B2 (en) * | 2007-07-04 | 2011-12-21 | 三菱電機株式会社 | Frequency change rate protection relay device |
| CN104931758B (en) * | 2014-03-21 | 2018-03-27 | 上海电科电器科技有限公司 | Direct current residual current detection device |
| CN105552831A (en) * | 2016-03-04 | 2016-05-04 | 河南许继智能科技股份有限公司 | DC feeder protection method for subway |
| CN106026702B (en) * | 2016-05-23 | 2019-10-25 | 安徽省金屹电源科技有限公司 | A kind of high power DC plasma electrical source |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102842890A (en) * | 2012-09-24 | 2012-12-26 | 国电南瑞科技股份有限公司 | Realizing method of current change rate protection |
| CN111856324A (en) * | 2020-07-30 | 2020-10-30 | 中国联合网络通信集团有限公司 | Fault detection method and device for traction network feeder line |
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