CN112578179B - Power monitoring method - Google Patents
Power monitoring method Download PDFInfo
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- CN112578179B CN112578179B CN202011548359.4A CN202011548359A CN112578179B CN 112578179 B CN112578179 B CN 112578179B CN 202011548359 A CN202011548359 A CN 202011548359A CN 112578179 B CN112578179 B CN 112578179B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R21/00—Arrangements for measuring electric power or power factor
- G01R21/001—Measuring real or reactive component; Measuring apparent energy
- G01R21/002—Measuring real component
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R21/00—Arrangements for measuring electric power or power factor
- G01R21/06—Arrangements for measuring electric power or power factor by measuring current and voltage
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- Remote Monitoring And Control Of Power-Distribution Networks (AREA)
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Abstract
The invention relates to a power monitoring method, which synchronously samples the voltage and the current of each monitoring point, calculates the phasor value of the voltage and the current of each monitoring point, extracts the corresponding positive sequence voltage and the corresponding positive sequence current phasor value and the corresponding negative sequence current phasor value from the voltage and the current phasor values, calculates the positive sequence voltage phasor value and the negative sequence voltage phasor value of each monitoring point by using the positive sequence voltage and the positive sequence current phasor value and each section of impedance of a power supply wire, and finally calculates the positive sequence current phasor value and the negative sequence current phasor value of each monitoring point according to the measurement of each monitoring point to calculate the active power of each power monitoring point. The invention is specially aimed at the occasion that the power consumption and the electric quantity consumption of the medium-high voltage power network need to be investigated, but the voltage measurement is difficult to implement, the power monitoring can be realized when the voltage measurement of the power monitoring point is absent, and the invention is easy to implement and has lower cost.
Description
Technical Field
The invention belongs to the field of power measurement and metering, and particularly relates to a power monitoring method which is particularly suitable for a place needing power measurement on a feed-out line of a high-voltage (10 kV and above) power grid, and is particularly suitable for an occasion needing outdoor temporary measurement of load power or electric quantity consumption investigation.
Background
Measurement of electric power and measurement of electric quantity require simultaneous measurement of voltage and current, however, it is not very convenient to implement monitoring of voltage on the feed-out line of a high voltage (10 kV and above) grid in view of insulation distance, since measurement of voltage requires bridging over two phase feed-out lines, and the voltage difference is the line voltage. For this reason, a power monitoring method is needed when the voltage measurement at the power monitoring point is missing.
Disclosure of Invention
The invention aims to provide a power monitoring method when the voltage measurement of a power monitoring point is absent, which is suitable for power monitoring when the voltage measurement of the power monitoring point is absent on a feed-out line of a high-voltage (10 kV and above) power grid, and is particularly suitable for occasions needing to measure load power or electric quantity consumption investigation outdoors temporarily.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a power monitoring method comprising the steps of:
step 1: monitoring bus voltage at the secondary side of a voltage transformer of the substation, and monitoring current at a feed-out outlet and power monitoring points of the substation;
step 2: synchronously sampling bus voltage, feed-out line outlet current and current of each power monitoring point, calculating phase voltage magnitude according to the sampled bus voltage, calculating feed-out line outlet current magnitude according to the sampled feed-out line outlet current, and calculating corresponding power monitoring point current magnitude according to the sampled power monitoring point current;
step 3: calculating positive sequence voltage vectors and negative sequence voltage vectors of buses according to the phase voltage vector values, calculating positive sequence current vectors and negative sequence current vectors of a feed-out line outlet according to the feed-out line outlet current vector values, and calculating positive sequence current vectors and negative sequence current vectors of the power monitoring points according to the power monitoring point current vector values;
step 4: calculating positive sequence voltage and negative sequence voltage of each power monitoring point according to the positive sequence current vector and the negative sequence current vector of each power monitoring point;
step 5: and calculating the active power of each power monitoring point according to the positive sequence current vector, the negative sequence current vector, the positive sequence voltage and the negative sequence voltage of each power monitoring point.
In the step 2, the method for calculating the phase voltage magnitude, the feed-out line outlet current magnitude and the power monitoring point current magnitude comprises the following steps:
wherein:for the magnitude of the phase voltage, u AB (k)、u CB (k) For sampling the busbar voltage, superscript S, L indicates the supply side and the load side, respectively,/-for example>Is a currentVector value i=0 represents the feed-out line outlet, i=1, 2, …, n represents the serial number of the power monitoring point, +.>And the sampled currents are respectively the busbar voltage, the outlet current of the feed-out line and the sampling points of the current of each power monitoring point in one fundamental wave period.
In the step 3, a positive sequence voltage vector of the bus is calculatedAnd negative sequence voltage vector->The method of (1) is as follows:
in the step 3, a positive sequence current vector is calculatedAnd negative sequence current vector->The method of (1) is as follows:
in the step 4, positive sequence voltage of each power monitoring point is calculatedAnd negative sequence voltage->The method of (1) is as follows:
wherein:the power supply side positive sequence current vector and the negative sequence current vector of the j-th power monitoring point are respectively +.> The j-1 th positive sequence current vector and the negative sequence current vector of the load side of the power monitoring point are respectively R j-1 、X j-1 The resistance and reactance of the lead between the j power monitoring points and the j-1 power monitoring point are respectively shown, j is a serial number, and j=1-i.
In the step 5, the method for calculating the active power of each power monitoring point comprises the following steps:
P i ＝P i S -P i L
wherein: p (P) i S 、P i L The power source side active power and the load side active power of the ith power monitoring point are respectively, P i Active power for the ith power monitoring point,positive sequence and negative sequence power factors of the power source side of the ith power monitoring point respectively,/->And the positive sequence and the negative sequence power factors of the load side of the ith power monitoring point are respectively.
Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages: the invention is specially aimed at the occasion that the power consumption and the electric quantity consumption of the medium-high voltage power network need to be investigated, but the voltage measurement is difficult to implement, the power monitoring can be realized when the voltage measurement of the power monitoring point is absent, and the invention is easy to implement and has lower cost.
Drawings
Fig. 1 is a device installation topology in the practice of the present invention.
Detailed Description
The invention will be further described with reference to examples of embodiments shown in the drawings.
Embodiment one: a power monitoring method comprising the steps of:
step 1: and monitoring the bus voltage at the secondary side of the voltage transformer of the substation, and monitoring the current at the outlet of the feed-out line of the substation and each power monitoring point.
Step 2: sampling bus voltage, feeding-out line outlet current and each power monitoring point current, calculating phase voltage magnitude according to the sampled bus voltage, calculating feeding-out line outlet current magnitude according to the sampled feeding-out line outlet current, and calculating corresponding power monitoring point current magnitude according to the sampled power monitoring point current. Here, the bus voltage and the current at each power monitoring point must be sampled synchronously, although at different locations.
The method for calculating the phase voltage magnitude value, the feed-out line outlet current magnitude value and the power monitoring point current magnitude value comprises the following steps:
in the above formula:for the phase voltage magnitude, u AB (k)、u CB (k) For sampled busbar voltage, superscript S, L indicates the supply side and the load side, respectively, +.>For the current vector value i=0 denotes the feed-out line outlet, i=1, 2, …, n denotes the sequence number of the power monitoring point, +.>The sampling currents are respectively sampled, and N is the sampling point number of the busbar voltage, the outlet current of the feed-out line and the current of each power monitoring point in one fundamental wave period.
Step 3: and calculating positive sequence voltage vectors and negative sequence voltage vectors of the bus according to the phase voltage vector values, calculating positive sequence current vectors and negative sequence current vectors of the outlet of the feed-out line according to the current vector values of the outlet of the feed-out line, and calculating positive sequence current vectors and negative sequence current vectors of all the power monitoring points according to the current vector values of the power monitoring points.
Calculating positive sequence voltage vector of busAnd negative sequence electricityPressure vector->The method of (1) is as follows:
from the following componentsAnd (3) solving to obtain three-phase voltages: />Positive sequence, negative sequence voltage:and->Wherein: /> Obtaining: />And
calculating positive sequence current vectorAnd negative sequence current vector->The method of (1) is as follows:
from the following componentsAnd->Obtaining:
step 4: and calculating the positive sequence voltage and the negative sequence voltage of each power monitoring point according to the positive sequence current vector and the negative sequence current vector of each power monitoring point.
Calculating positive sequence voltage of each power monitoring pointAnd negative sequence voltage->The method of (1) is as follows:
in the formula (3):the positive sequence current vector and the negative sequence current vector of the power supply side of the j power monitoring point are respectively +.>The positive sequence current vector and the negative sequence current vector of the load side of the j-1 th power monitoring point are respectively R j-1 、X j-1 The resistance and reactance of the wire between the jth power monitoring point and the jth-1 power monitoring point are respectively shown, j is a serial number, and j=1-i.
Step 5: and calculating the active power of each power monitoring point according to the positive sequence current vector and the negative sequence current vector, the positive sequence voltage and the negative sequence voltage of each power monitoring point.
The method for calculating the active power of each power monitoring point comprises the following steps:
P i ＝P i S -P i L (5)
in the formula (4) (5): p (P) i S 、P i L Active power at power source side and active power at load side of ith power monitoring point respectively, P i Active power for the ith power monitoring point,positive sequence and negative sequence power factors of the power supply side of the ith power monitoring point respectively, +.>And the positive sequence and the negative sequence power factors of the load side of the ith power monitoring point are respectively.
Although the current of each load of the operating grid is generally asymmetric, thus making the voltage of each power monitoring point asymmetric, we can split them into 2 symmetric components, namely positive and negative sequence symmetric components. According to the superposition principle of the linear circuit, positive sequence current, negative sequence current and voltage can be respectively and independently calculated in 2 symmetrical circuits, and then the total voltage and current are obtained by adding. The voltage and current of phase a can be expressed as:
by power definition, the voltage and current of a port are the same frequency sinusoids, the instantaneous power of which is the product of the instantaneous values of the voltage and current, i.e. the absorbed power of the a phase is:
p A ＝u A (t)·i A (t)＝[u 1A (t)+u 2A (t)]·[i 1A (t)+i 2A (t)]
＝u 1A (t)·i 1A (t)+u 1A (t)·i 2A (t)+u 2A (t)·i 1A (t)+u 2A (t)·i 2A (t)
the average power for one cycle is:
here:therefore, the three-phase power on the power supply side and the load side of the power monitoring point is:
the power consumed by the branch load of the power monitoring point is the difference between the three-phase power of the power supply side and the load side:
P i ＝P i S -P i L (5)
the above method may be implemented in the installation topology of fig. 1. The secondary voltage of the 10kV bus is obtained at the PT position of the 10kV bus in the substation, a voltage collector is installed, and 2n pairs of current collectors are respectively installed at the feed-out line outlet (i=0) of the substation and the bifurcation points of each current, namely power monitoring points (i=1-n), wherein F is a power monitoring load. In theory, all current bifurcation points should be provided with 2 pairs of current collectors, but in practice, points with smaller bifurcation currents can be skipped, so that the accuracy of power monitoring can be affected a little, but because the average value of the current at the power supply side of the monitoring point and the current at the front pair of load sides is adopted in the formula (3) to correct the voltage of the monitoring point, meanwhile, because the bifurcation currents are small, the influence on the estimated voltage of each monitoring point is small, and therefore, the generated error is small. The voltage and current collectors adopt wireless communication (which can be a Rola communication system, or an NB narrowband communication system, or other communication systems) to transmit collected data to a server, so that the power consumed by each required power monitoring point is calculated according to the formulas (1) to (5) of the method, and meanwhile, the electric quantity consumption of each monitoring point is also measured.
The beneficial effect of this scheme lies in: the measurement of power must obtain information about the voltage and current at the power measurement point, and in the case of medium and high voltages, since the voltage measurement needs to be performed across two points subjected to full voltage, it is difficult to implement or expensive to implement in view of the insulation safety distance, especially in the case of temporary use outdoors. The invention has the advantages of specially aiming at occasions where the power consumption and the electric quantity consumption of the medium-high voltage power network need to be investigated, but the voltage measurement is difficult to implement.
The above embodiments are provided to illustrate the technical concept and features of the present invention and are intended to enable those skilled in the art to understand the content of the present invention and implement the same, and are not intended to limit the scope of the present invention. All equivalent changes or modifications made in accordance with the spirit of the present invention should be construed to be included in the scope of the present invention.
Claims (2)
1. A power monitoring method, characterized by: the power monitoring method comprises the following steps:
step 1: monitoring bus voltage at the secondary side of a voltage transformer of the substation, and monitoring current at a feed-out outlet and power monitoring points of the substation;
step 2: synchronously sampling bus voltage, feed-out line outlet current and current of each power monitoring point, calculating phase voltage magnitude according to the sampled bus voltage, calculating feed-out line outlet current magnitude according to the sampled feed-out line outlet current, and calculating corresponding power monitoring point current magnitude according to the sampled power monitoring point current;
step 3: calculating positive sequence voltage vectors and negative sequence voltage vectors of buses according to the phase voltage vector values, calculating positive sequence current vectors and negative sequence current vectors of a feed-out line outlet according to the feed-out line outlet current vector values, and calculating positive sequence current vectors and negative sequence current vectors of the power monitoring points according to the power monitoring point current vector values;
step 4: calculating positive sequence voltage and negative sequence voltage of each power monitoring point according to the positive sequence current vector and the negative sequence current vector of each power monitoring point;
step 5: calculating the active power of each power monitoring point according to the positive sequence current vector, the negative sequence current vector, the positive sequence voltage and the negative sequence voltage of each power monitoring point;
in the step 2, the method for calculating the phase voltage magnitude, the feed-out line outlet current magnitude and the power monitoring point current magnitude comprises the following steps:
wherein:for the magnitude of the phase voltage magnitude,u AB (k)、u CB (k) For sampling the busbar voltage, superscript S, L indicates the supply side and the load side, respectively,/-for example>For the current vector value, i=0 represents the feed-out line outlet, i=1, 2, …, n represents the sequence number of the power monitoring point, +.>The sampled currents are respectively sampled, and N is the number of sampling points of the busbar voltage, the outlet current of the feed-out line and the current of each power monitoring point in a fundamental wave period;
in the step 3, a positive sequence voltage vector of the bus is calculatedAnd negative sequence voltage vector->The method of (1) is as follows:
in the step 3, a positive sequence current vector is calculatedAnd negative sequence current vector->The method of (1) is as follows:
in the step 4, positive sequence voltage of each power monitoring point is calculatedAnd negative sequence voltage->The method of (1) is as follows:
wherein:the positive sequence current vector and the negative sequence current vector of the power supply side of the j-th power monitoring point are respectively, the j-1 th positive sequence current vector and the negative sequence current vector of the load side of the power monitoring point are respectively R j-1 、X j-1 The resistance and reactance of the lead between the j power monitoring points and the j-1 power monitoring point are respectively shown, j is a serial number, and j=1-i.
2. A method of power monitoring according to claim 1, wherein: in the step 5, the method for calculating the active power of each power monitoring point comprises the following steps:
P i ＝P i S -P i L
wherein: p (P) i S 、P i L The power source side active power and the load side active power of the ith power monitoring point respectivelyRate, P i Active power for the ith power monitoring point,positive sequence and negative sequence power factors of the power source side of the ith power monitoring point respectively,/->And the positive sequence and the negative sequence power factors of the load side of the ith power monitoring point are respectively.
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