CN110907881A - Current calibration method and system for power distribution network overhead line monitoring device - Google Patents
Current calibration method and system for power distribution network overhead line monitoring device Download PDFInfo
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Abstract
The invention provides a method and a system for calibrating the current of a power distribution network overhead line monitoring device, which calibrate the power distribution network monitoring device by twice calibration, and realize coarse tuning by writing calibration coefficients corresponding to 11 calibration gears into an acquisition unit during the once calibration; during secondary calibration, fine adjustment is realized in a sectional calibration mode by adopting a least square method; meanwhile, when the load current sampling value and the current source actual output current sampling value are obtained, abnormal conditions caused by electromagnetic interference are effectively avoided by continuously reading for multiple times and taking an average value, in the calibration process, each calibration gear or calibration current adopts the actual current value rather than the theoretical value, and abnormal conditions caused by instability of the current source are effectively avoided. Through twice calibration, the load current precision of the fault indicator can be controlled within 0.5%, and the accuracy and reliability of fault detection are greatly improved.
Description
Technical Field
The invention relates to the technical field of power supply and distribution, in particular to a method and a system for calibrating current of a power distribution network overhead line monitoring device.
Background
In recent years, the monitoring of the overhead line to ground and short-circuit faults in domestic medium-voltage power distribution networks becomes a key research point for monitoring the power distribution networks. Set up monitoring devices on the distribution lines, monitoring devices comprises acquisition unit and collection unit, installs on the distribution lines, is used for monitoring circuit operating parameter, detects and instructs all kinds of short circuits, ground fault, sends monitoring information, waveform file and fault detection data to the distribution main website simultaneously. Since the fault judgment mainly depends on the change of the load current of the monitoring device, the current precision is directly related to the fault judgment result. Therefore, how to improve the current precision of the power distribution network overhead line monitoring device so as to improve the accuracy and reliability of power distribution network overhead line fault judgment is a technical problem which needs to be solved urgently in the field.
Disclosure of Invention
The invention aims to provide a current calibration method and a current calibration system for an overhead line monitoring device of a power distribution network, which aim to solve the problems of low current precision and large error of the overhead line monitoring device during monitoring in the prior art and improve the accuracy and reliability of fault judgment of the overhead line of the power distribution network.
In order to achieve the technical purpose, the invention provides a current calibration method for a power distribution network overhead line monitoring device, which comprises the following steps of:
s1, setting the output current range of the current source of the distribution line;
s2, controlling the current source to respectively output N calibration gears within the output current range, sequentially recording M continuous load current sampling values and M continuous actual current sampling values in a segment between two adjacent calibration gears, calculating respective average values, calculating a calibration coefficient under each segment, and writing the calibration coefficient into the acquisition unit;
s3, recalibrating the segments of two adjacent calibration gears by using a least square method, fitting a fitted straight line of M continuous actual current sampling values and M continuous load current sampling values in each segment to obtain a slope and an intercept in each segment, and writing the slope and the intercept of each segment into an acquisition unit;
and S4, in the actual monitoring, multiplying the load current value of the monitoring device by the calibration coefficient of the section, judging the section where the multiplication result is positioned, and calculating by using the slope and the intercept in the section to obtain the calibrated final load current value.
Preferably, the fitted straight line formula is:
y＝kx+b
x is the load current sample value and y is the actual current sample value.
Preferably, when the current value to be calibrated in actual measurement is an endpoint value, two adjacent fitting straight lines are adopted for respective calibration, and the current value is averaged to be used as the final actual measurement value.
The invention also provides a current calibration system for the overhead line monitoring device of the power distribution network, which comprises the following components:
the output current range setting module is used for setting the output current range of the current source of the distribution line;
the primary calibration module is used for controlling the current source to output N calibration gears respectively in the output current range, sequentially recording M continuous load current sampling values and M continuous actual current sampling values in a section between two adjacent calibration gears, calculating respective average values, calculating a calibration coefficient under each section, and writing the calibration coefficient into the acquisition unit;
the secondary calibration module is used for carrying out recalibration on the segments of two adjacent calibration gears by using a least square method, fitting a fitting straight line of M continuous actual current sampling values and M continuous load current sampling values in each segment to obtain a slope and an intercept in each segment, and writing the slope and the intercept of each segment into the acquisition unit;
and the current calculation module is used for multiplying the load current value of the monitoring device with the calibration coefficient of the section in which the load current value is positioned in actual monitoring, judging the section in which the multiplication result is positioned, and calculating by utilizing the slope and the intercept in the section to obtain the calibrated final load current value.
Preferably, the fitted straight line formula is:
y＝kx+b
x is the load current sample value and y is the actual current sample value.
Preferably, when the current value to be calibrated in actual measurement is an endpoint value, two adjacent fitting straight lines are adopted for respective calibration, and the current value is averaged to be used as the final actual measurement value.
The effect provided in the summary of the invention is only the effect of the embodiment, not all the effects of the invention, and one of the above technical solutions has the following advantages or beneficial effects:
compared with the prior art, the calibration work of the power distribution network monitoring device is realized by twice calibration, and during the once calibration, coarse adjustment is realized by writing calibration coefficients corresponding to 11 calibration gears into the acquisition unit; during secondary calibration, fine adjustment is realized in a sectional calibration mode by adopting a least square method; meanwhile, when the load current sampling value and the current source actual output current sampling value are obtained, abnormal conditions caused by electromagnetic interference are effectively avoided by continuously reading for multiple times and taking an average value, in the calibration process, each calibration gear or calibration current adopts the actual current value rather than the theoretical value, and abnormal conditions caused by instability of the current source are effectively avoided. Through twice calibration, the load current precision of the fault indicator can be controlled within 0.5%, and the accuracy and reliability of fault detection are greatly improved.
Drawings
Fig. 1 is a flowchart of a current calibration method for a power distribution network overhead line monitoring device according to an embodiment of the present invention;
fig. 2 is a block diagram of a current calibration system of a power distribution network overhead line monitoring device provided in an embodiment of the present invention.
Detailed Description
In order to clearly explain the technical features of the present invention, the following detailed description of the present invention is provided with reference to the accompanying drawings. The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. It should be noted that the components illustrated in the figures are not necessarily drawn to scale. Descriptions of well-known components and processing techniques and procedures are omitted so as to not unnecessarily limit the invention.
The following describes a method and a system for calibrating the current of the power distribution network overhead line monitoring device provided by the embodiment of the invention in detail with reference to the accompanying drawings.
As shown in fig. 1, the invention discloses a current calibration method for a power distribution network overhead line monitoring device, which comprises the following steps:
s1, setting the output current range of the current source of the distribution line;
s2, controlling the current source to output N calibration gears respectively in the output current range, recording M continuous load current sampling values and M continuous actual current sampling values between two adjacent calibration gears in sequence, calculating respective average values, calculating a calibration coefficient under each calibration gear, and writing the calibration coefficient into an acquisition unit;
s3, recalibrating the segments of two adjacent calibration gears by using a least square method, fitting a fitted straight line of M continuous actual current sampling values and M continuous load current sampling values in each segment to obtain a slope and an intercept in each segment, and writing the slope and the intercept of each segment into an acquisition unit;
and S4, in the actual monitoring, multiplying the load current value of the monitoring device by the calibration coefficient, judging the section where the multiplication result is located, and calculating by using the slope and the intercept in the section to obtain the calibrated final load current value.
And setting the output current range of the current source of the distribution line to be 0-800A.
The method comprises the steps of installing a collecting unit of the monitoring device on a distribution line, controlling a current source to output 11 calibration gears respectively, enabling current values corresponding to no calibration gear to be 0A, 30A, 70A, 100A, 200A, 300A, 400A, 500A, 600A, 700A and 800A respectively, recording 100 continuous load current sampling values and 100 continuous actual current sampling values between every two calibration gears in sequence, and carrying out averaging calculation on the 100 load current sampling values and the 100 actual current sampling values to obtain an average value of the 100 load current sampling values and the 100 actual current sampling values.
And analyzing the relation between the load current sampling average value of each calibration gear and the actual current sampling average value detected by the ammeter, and calculating to obtain a calibration coefficient S between the load current sampling average value and the actual current sampling average value, wherein each calibration gear corresponds to one calibration coefficient S, and the S value is the ratio of the actual current sampling average value to the load current sampling average value.
And directly writing the load current sampling average value obtained by each gear and the corresponding primary calibration coefficient M into the acquisition unit.
After the primary calibration, the acquisition unit is calibrated for the second time, namely, the least square method is adopted for the sectional calibration. Controlling the current output by the current source to sequentially increase from 0A to 800A, increasing the current by 1A each time, sequentially recording 100 continuous load current sampling values and 100 continuous actual current sampling values for each output current value, and calculating the average value of the 100 load current sampling values and the 100 actual current sampling values to obtain 100 load current sampling values xi(i is more than or equal to 0 and less than or equal to 800) and the average value y of 100 actual current sampling valuesi(i is not less than 0 and not more than 800), the slope k and the intercept b of the best fit straight line of each segment are calculated by the least square method, and the corresponding fit straight line y is kx + b. Taking 0A-100A as an example, (xi, y)i) (i is more than or equal to 0 and less than or equal to 100) all 101 groups of data are used for obtaining the slope k of the best fitting straight line of the first segmentiAnd intercept biAnd calculating a corresponding fitted straight line y ═ k1x+b1When the actual current measurement is within 1-100A, the line is used for calibration. When the actual current value is 0, since the fitting straight line does not pass through the origin, special processing needs to be performed on the zero point, that is, the current value after calibration is also set to 0.
Similarly, the other 9 segments of the piecewise calibration fitting straight line y ═ k are respectively obtained2x+b2，y＝k3x+b3，…，y＝k10x+b10。
In the fitting process, the last value of a certain section is the same as the first value of the next section, so that if the current value to be calibrated in a certain actual measurement is an endpoint value, two adjacent fitting straight lines are adopted for respective calibration, and then the average value is taken as the final actual measurement value.
And finally writing the slope k and the intercept b corresponding to each segment into an acquisition unit.
The embodiment of the invention realizes the calibration work of the power distribution network monitoring device through two times of calibration, and during one time of calibration, coarse adjustment is realized by writing calibration coefficients corresponding to 11 calibration gears into the acquisition unit respectively; during secondary calibration, fine adjustment is realized in a sectional calibration mode by adopting a least square method; meanwhile, when the load current sampling value and the current source actual output current sampling value are obtained, abnormal conditions caused by electromagnetic interference are effectively avoided by continuously reading for multiple times and taking an average value, in the calibration process, each calibration gear or calibration current adopts the actual current value rather than the theoretical value, and abnormal conditions caused by instability of the current source are effectively avoided. Through twice calibration, the load current precision of the fault indicator can be controlled within 0.5%, and the accuracy and reliability of fault detection are greatly improved.
As shown in fig. 2, an embodiment of the present invention further discloses a system for calibrating a current of an overhead line monitoring device of a power distribution network, where the system includes:
the output current range setting module is used for setting the output current range of the current source of the distribution line;
the primary calibration module is used for controlling the current source to output N calibration gears respectively in the output current range, sequentially recording M continuous load current sampling values and M continuous actual current sampling values in a section between two adjacent calibration gears, calculating respective average values, calculating a calibration coefficient under each section, and writing the calibration coefficient into the acquisition unit;
the secondary calibration module is used for carrying out recalibration on the segments of two adjacent calibration gears by using a least square method, fitting a fitting straight line of M continuous actual current sampling values and M continuous load current sampling values in each segment to obtain a slope and an intercept in each segment, and writing the slope and the intercept of each segment into the acquisition unit;
and the current calculation module is used for multiplying the load current value of the monitoring device with the calibration coefficient of the section in which the load current value is positioned in actual monitoring, judging the section in which the multiplication result is positioned, and calculating by utilizing the slope and the intercept in the section to obtain the calibrated final load current value.
And setting the output current range of the current source of the distribution line to be 0-800A.
The method comprises the steps of installing a collecting unit of the monitoring device on a distribution line, controlling a current source to output 11 calibration gears respectively, enabling current values corresponding to no calibration gear to be 0A, 30A, 70A, 100A, 200A, 300A, 400A, 500A, 600A, 700A and 800A respectively, recording 100 continuous load current sampling values and 100 continuous actual current sampling values between every two calibration gears in sequence, and carrying out averaging calculation on the 100 load current sampling values and the 100 actual current sampling values to obtain an average value of the 100 load current sampling values and the 100 actual current sampling values.
And analyzing the relation between the load current sampling average value of each calibration gear and the actual current sampling average value detected by the ammeter, and calculating to obtain a calibration coefficient S between the load current sampling average value and the actual current sampling average value, wherein each calibration gear corresponds to one calibration coefficient S, and the S value is the ratio of the actual current sampling average value to the load current sampling average value.
And directly writing the load current sampling average value obtained by each gear and the corresponding primary calibration coefficient M into the acquisition unit.
After the primary calibration, the acquisition unit is calibrated for the second time, namely, the least square method is adopted for the sectional calibration. Controlling the current output by the current source to sequentially increase from 0A to 800A, increasing the current by 1A each time, sequentially recording 100 continuous load current sampling values and 100 continuous actual current sampling values for each output current value, and calculating the average value of the 100 load current sampling values and the 100 actual current sampling values to obtain 100 load current sampling values xi(i is more than or equal to 0 and less than or equal to 800) and the average value y of 100 actual current sampling valuesi(i is not less than 0 and not more than 800), the slope k and the intercept b of the best fit straight line of each segment are calculated by the least square method, and the corresponding fit straight line y is kx + b. Taking 0A-100A as an example, using (x)i，yi) (i is more than or equal to 0 and less than or equal to 100) all 101 groups of data are used for obtaining the slope k of the best fitting straight line of the first segmentiAnd intercept biAnd calculating a corresponding fitted straight line y ═ k1x+b1When the actual current measurement is within 1-100A, the line is used for calibration. When the actual current value is 0, since the fitting straight line does not pass through the origin, special processing needs to be performed on the zero point, that is, the current value after calibration is also set to 0.
Similarly, the other 9 segments of the piecewise calibration fitting straight line y ═ k are respectively obtained2x+b2，y＝k3x+b3，…，y＝k10x+b10。
In the fitting process, the last value of a certain section is the same as the first value of the next section, so that if the current value to be calibrated in a certain actual measurement is an endpoint value, two adjacent fitting straight lines are adopted for respective calibration, and then the average value is taken as the final actual measurement value.
And finally writing the slope k and the intercept b corresponding to each segment into an acquisition unit.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (6)
1. A power distribution network overhead line monitoring device current calibration method is characterized by comprising the following steps:
s1, setting the output current range of the current source of the distribution line;
s2, controlling the current source to respectively output N calibration gears within the output current range, sequentially recording M continuous load current sampling values and M continuous actual current sampling values in a segment between two adjacent calibration gears, calculating respective average values, calculating a calibration coefficient under each segment, and writing the calibration coefficient into the acquisition unit;
s3, recalibrating the segments of two adjacent calibration gears by using a least square method, fitting a fitted straight line of M continuous actual current sampling values and M continuous load current sampling values in each segment to obtain a slope and an intercept in each segment, and writing the slope and the intercept of each segment into an acquisition unit;
and S4, in the actual monitoring, multiplying the load current value of the monitoring device by the calibration coefficient of the section, judging the section where the multiplication result is positioned, and calculating by using the slope and the intercept in the section to obtain the calibrated final load current value.
2. The method for calibrating the current of the power distribution network overhead line monitoring device according to claim 1, wherein the fitting straight line formula is as follows:
y＝kx+b
x is the load current sample value and y is the actual current sample value.
3. The current calibration method for the overhead line monitoring device of the power distribution network according to claim 1, characterized in that when the current value to be calibrated in actual measurement is an endpoint value, two adjacent fitting straight lines are respectively calibrated, and the average value is taken as the final actual measurement value.
4. A power distribution network overhead line monitoring device current calibration system, the system comprising:
the output current range setting module is used for setting the output current range of the current source of the distribution line;
the primary calibration module is used for controlling the current source to output N calibration gears respectively in the output current range, sequentially recording M continuous load current sampling values and M continuous actual current sampling values in a section between two adjacent calibration gears, calculating respective average values, calculating a calibration coefficient under each section, and writing the calibration coefficient into the acquisition unit;
the secondary calibration module is used for carrying out recalibration on the segments of two adjacent calibration gears by using a least square method, fitting a fitting straight line of M continuous actual current sampling values and M continuous load current sampling values in each segment to obtain a slope and an intercept in each segment, and writing the slope and the intercept of each segment into the acquisition unit;
and the current calculation module is used for multiplying the load current value of the monitoring device with the calibration coefficient of the section in which the load current value is positioned in actual monitoring, judging the section in which the multiplication result is positioned, and calculating by utilizing the slope and the intercept in the section to obtain the calibrated final load current value.
5. The power distribution network overhead line monitoring device current calibration system of claim 4, wherein the fitted straight line formula is:
y＝kx+b
x is the load current sample value and y is the actual current sample value.
6. The system according to claim 4, wherein when the current value to be calibrated in actual measurement is an endpoint value, two adjacent fitting straight lines are respectively calibrated, and the average value is taken as the final actual measurement value.
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