CN109449920B - Low-voltage distribution network theoretical line loss calculation method - Google Patents

Low-voltage distribution network theoretical line loss calculation method Download PDF

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CN109449920B
CN109449920B CN201811131187.3A CN201811131187A CN109449920B CN 109449920 B CN109449920 B CN 109449920B CN 201811131187 A CN201811131187 A CN 201811131187A CN 109449920 B CN109449920 B CN 109449920B
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孟珺遐
蒋利民
王毅
代双寅
白士贤
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XI'AN ACTIONPOWER ELECTRIC CO LTD
State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
Electric Power Research Institute of State Grid Henan Electric Power Co Ltd
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State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
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Abstract

The invention provides a method for calculating theoretical line loss of a low-voltage distribution network, which comprises the following steps of: step 1, selecting a typical low-voltage transformer area optionally, and constructing a network topological structure of the typical low-voltage transformer area; step 2, obtaining current, voltage, total active power, total reactive power and phase angle of each branch at a point-in-time moment in the constructed typical low-voltage transformer area network topological structure; step 3, calculating the phase line loss and the neutral line loss of each branch; step 4, calculating phase line additional loss and neutral line additional loss generated by k-th harmonic in each branch; and 5, calculating the phase line equivalent resistance and the middle line equivalent resistance in the constructed network topological structure of the typical low-voltage transformer area, and obtaining the line loss of the typical low-voltage transformer area. The method considers the influence of three typical power quality factors with larger influence on the line loss calculation, calculates the theoretical line loss of the transformer area by adopting a backward forward pushing mode according to the actual measurement load data on the representative day, and considers both the calculation precision and the engineering practicability.

Description

Low-voltage distribution network theoretical line loss calculation method
Technical Field
The invention belongs to the technical field of theoretical line loss calculation of a power distribution network, and particularly relates to a theoretical line loss calculation method of a low-voltage power distribution network.
Background
The reduction of the line loss rate of the power distribution network is an effective measure for improving the economic benefit of power enterprises, and the accuracy of line loss theoretical calculation can enable the line loss theoretical calculation to reflect the loss condition of the power distribution network more objectively, so that the line loss of the power distribution network is managed more effectively and the power distribution network is operated more economically. According to the voltage class of the power distribution network, theoretical line loss calculation methods are also roughly divided into three types, one type is theoretical line loss calculation of a 10kV (20kV) medium-voltage power distribution network, and the theoretical line loss calculation method mainly comprises a distribution line loss part and a distribution transformer loss part; the other part is the theoretical line loss calculation of the 0.4kV low-voltage distribution network and mainly comprises the parts of low-voltage distribution line loss, house-entry cable loss, user electric energy meter loss and the like. The high-voltage power grid of 35kV or above has a clear network structure, high automation degree of the power grid and complete parameters required by line loss theoretical calculation, and some conditional enterprises have realized computer on-line calculation by adopting a load flow calculation method.
The low-voltage distribution network refers to a low-voltage power grid of 0.4kV or below, and the theoretical line loss calculation of the low-voltage distribution network needs distribution network structure parameters and operation data. Generally, the network structure of a research object of the theoretical line loss calculation work of the power distribution network is basically fixed, representative daily load is selected, and a proper calculation method is adopted to obtain the theoretical line loss calculation work.
The theoretical line loss calculation of the low-voltage distribution network has the following characteristics:
(1) uncertainty of external environment
Due to the fact that the network structure of the low-voltage distribution network is complex, differences exist in access load characteristics, load power changes in real time, the external environment conditions have uncertainty, it is difficult to accurately calculate theoretical line loss of the low-voltage distribution network, loss of the low-voltage distribution network needs to be accurately calculated, and factors influencing loss in theoretical analysis are close to actual operation state parameters of the low-voltage distribution network as far as possible.
(2) Approximate simplification of computational conditions
Due to the fact that the network structure of the low-voltage distribution network is complex, a plurality of branch lines exist, monitoring equipment cannot be configured on all nodes, in order to achieve theoretical analysis and calculation, a calculation method needs to be constructed on the assumption of certain preconditions, and due to the fact that approximation and simplification are conducted to a certain degree, calculation results have deviation to a certain degree.
(3) Diversity of computational methods
Effective and reasonable hypothesis calculation is carried out according to the network structure and the load general outline of the low-voltage distribution network, the power distribution network theoretical loss calculation methods are various, and the methods have larger differences.
At present, the common calculation methods for the theoretical line loss of the low-voltage distribution network include a root mean square current method, an average current method (a form factor method), a maximum current method (a loss factor method), a voltage loss rate method, a transformer area loss rate method, an equivalent resistance method, a power flow method, an artificial neural network method and the like. From the source of the data according to calculation, the root mean square current method and the maximum current method and the average current method derived from the root mean square current method are calculated according to the data at the head end of the feeder line; the tide method, the artificial neural network method and the like need to acquire all branch data for calculation; the number of data to be acquired in the distribution room loss rate method, the voltage loss rate method and the equivalent resistance method is between the two methods, and branch and tail end meter data which are easy to acquire are used and combined with feeder line head end data for calculation, so that the method has strong engineering practicability.
The root mean square current method is difficult to estimate the additional loss of the power quality disturbance on the post-stage branch according to the active power, the reactive power, the current effective value and each harmonic current of the head end of the secondary side feeder line of the distribution transformer of the transformer area; when the root mean square current of a branch line or a main line is calculated, the three-phase load data at the head end of the feeder line cannot reflect the distribution situation of the load on the distribution line. When line loss calculation is carried out, the monitoring device is lacked, and the loss of parameters required by line loss theoretical calculation is more. The platform area loss rate method and the voltage loss rate method have rough algorithms and low precision, and do not reflect the influence of power quality disturbance on loss; the equivalent resistance method is derived on the basis of a root mean square current method, the existing equivalent resistance method does not completely consider steady-state power quality factors (including three-phase imbalance, voltage deviation, harmonic waves and the like) influencing line loss, only considers the influence of the three-phase imbalance on the loss, only adopts feeder end data at the head end of a transformer area, does not consider the problem of the three-phase imbalance of a later-stage line, and has large deviation of a calculation result.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a theoretical line loss calculation method for a low-voltage distribution network, and solve the technical problem that the deviation of a calculation result is large due to the fact that steady-state power quality factors influencing line loss are not completely considered in the prior art.
In order to solve the technical problem, the application adopts the following technical scheme:
a low-voltage distribution network theoretical line loss calculation method comprises the following steps:
step 1, selecting a typical low-voltage transformer area optionally, and constructing a network topological structure of the typical low-voltage transformer area;
step 2, obtaining current, voltage, total active power, total reactive power and phase angle of each branch at a point-in-time moment in the constructed typical low-voltage transformer area network topological structure;
assuming that the constructed typical low-voltage distribution area network topology structure comprises I branches, wherein I is a natural number greater than 1; calculating phase line loss and neutral line loss of each branch circuit through current, voltage, total active power, total reactive power and phase angle of each branch circuit at each metering interval time t;
step 3, calculating phase line additional loss and neutral line additional loss generated by k-th harmonic in each branch according to phase line loss and neutral line loss of each branch in the constructed typical low-voltage transformer area network topological structure, wherein k is less than or equal to 50;
and 4, calculating phase line equivalent resistance and neutral line equivalent resistance in the constructed typical low-voltage distribution area network topological structure according to the phase line loss, the phase line additional loss, the neutral line loss and the neutral line additional loss of each branch, and obtaining the theoretical line loss of the low-voltage distribution network.
Further, through electric current, voltage, total active power, total reactive power and the phase angle of each branch road integral point moment, calculate branch road i's phase line loss and well line loss, include:
optionally selecting one branch I, I-1, 2, from the I branches;
if the branch i is a terminal branch, calculating the phase line loss and the neutral line loss of the branch i by using the formula (1):
Figure BDA0001813592740000041
Figure BDA0001813592740000042
in the formula (1), Δ ALiA，ΔALiBAnd Δ ALiCRepresenting the phase losses of phase A, B and C of branch i, respectively, APiA、APiBAnd APiCThe sum of active electric quantity of the A phase, the B phase and the C phase of the branch circuit i is expressed as kWh; a. theQiA、AQiBAnd AQiBThe sum of the reactive electric quantities of the A phase, the B phase and the C phase of the branch circuit i is represented by kvarh; u shapeavgLiA、UavgLiBAnd UavgLiCThe average value of the operating voltage of the A phase, the B phase and the C phase of the branch circuit i in the measurement interval time is represented by kV; t is the measurement interval time, and the unit is h; rLiΦThe phase line impedance of the branch i is in omega;
in the formula (2), Δ ALiNRepresents the centerline loss, I, of branch IavgLiNThe average current of the middle line of the branch i in the metering interval time is A; r isLiNIs the impedance of the midline line of the branch i, with the unit of omega;
if the branch i is not a terminal branch, and the branch i includes a preceding branch i.j, j is 1,2,.., m, and m is the number of preceding branches of the branch i, the phase line loss of the branch i is obtained by equation (3):
Figure BDA0001813592740000051
in the formula (3), Δ ALiA，ΔALiBAnd Δ ALiCPhase line losses of an A phase, a B phase and a C phase of the branch i are respectively represented; a. thePi.jA、APi.jBAnd APi.jCPhase A, phase B and phase C of the preceding branch i.jThe sum of the active electric quantity is expressed in kWh; a. theQi.jA、AQi.jBAnd AQi.jCThe sum of reactive electric quantities of the A phase, the B phase and the C phase of the front-stage branch i.j is represented by kvarh; u shapeavgi.jA、Uavgi.jBAnd Uavgi.jCThe average value of the operating voltages of the phase A, the phase B and the phase C of the preceding branch i.j in the measurement interval time is represented by kV; t is the measurement interval time, and the unit is h; rLiΦThe phase line impedance of the branch i is in omega;
obtaining the effective value of the neutral current of the branch i by the formula (4):
Figure BDA0001813592740000052
in the formula (4), INLiEffective value of neutral current of branch I, IΦLiAn，IΦLiBnAnd IΦLiCnRespectively representing the phase current values of the branch i at n moments, wherein the unit is A;
the neutral line loss of branch i is obtained by equation (5):
Figure BDA0001813592740000053
in the formula (5), Δ ALiNIs the neutral loss of branch I, IavgLiNThe average current of the middle line of the branch i in the metering interval time is A; rLiNThe impedance of the neutral line of branch i is given in Ω.
Further, the calculating phase line additional loss and neutral line additional loss generated by k-th harmonic in each branch according to phase line loss and neutral line loss of each branch includes:
optionally selecting one branch I, I-1, 2, from the I branches;
if the branch i is a terminal branch, obtaining the phase line additional loss of the branch i generated by the k-th harmonic by the formula (6):
Figure BDA0001813592740000061
formula (6)Middle, Delta AkLiA、ΔAkLiBAnd Δ AkLiCAdditional loss of phase line of A-, B-and C-phases due to k-th harmonic for branch i ηkLiA、ηkLiBAnd ηkLiCThe content of k-th harmonic in the branch i; rkLiΦThe k-th harmonic equivalent impedance of the branch i is in unit of omega;
if branch i is not the terminal branch, and branch i includes branch i.j and branch i.m, then the phase line parasitic loss of branch i due to the k-th harmonic is obtained by equation (7):
Figure BDA0001813592740000062
in the formula (7), IkLiA、IkLiBAnd IkLiCThe effective values of the k-th harmonic current of the A phase, the B phase and the C phase in the branch circuit i are obtained;
Figure BDA0001813592740000063
in the formula (8), IkLi.jA、IkLi.jBAnd IkLi.jCThe effective values of k-th harmonic currents of the A phase, the B phase and the C phase in the branch i.j; i iskLi.mA、IkLi.mBAnd IkLi.mCThe effective values of k-order harmonic currents of an A phase, a B phase and a C phase in a branch i.m;
IkLiNthe effective value of k-th harmonic current in a line in a branch i is as follows:
IkLiN＝||IkLiA∠0°+IkLiB∠-120°+IkLiC∠120°|| (9)
further, the phase line equivalent resistance and the middle line equivalent resistance in the constructed typical low-voltage transformer area network topology are calculated by the formula (10):
Figure BDA0001813592740000071
in the formula (10), RLeqΦIs a phase line equivalent resistor, RLeqNA neutral equivalent resistance; a. thePiAThe sum of the active electric quantity of the branch i is represented by kWh;AQiAthe sum of the reactive electric quantities of the branch i is represented by kvarh; u shapeavgiAThe average value of the operating voltage of the branch i in the measurement interval time is represented by kV; t is the measurement interval time, and the unit is h; rLiPhi is the phase line impedance of the branch i and the unit is omega; delta AkLiΦAdditional loss of phase line due to k-th harmonic for branch i ∑ Δ AkLiΦThe sum of the additional losses of the phase line generated by each subharmonic for the branch i; a. thePΣΦThe total active electric quantity of a typical low-voltage transformer area is the total; a. theQΣΦThe total reactive power quantity of a typical low-voltage transformer area is the sum; u shapeΦΣThe average value of the voltage of the phase line of the typical low-voltage transformer area is shown; sigma Delta ALNTotal parasitic loss of neutral; i isavgNΣAverage value of the total current of the neutral line.
Compared with the prior art, the invention has the beneficial technical effects that:
(1) the method is based on an equivalent resistance method, the influence of three typical power quality problems of a low-voltage power grid, namely three types of unbalanced three phases, voltage deviation and harmonic waves, on line loss is considered, and the improved algorithm accounts for the additional loss of power quality disturbance;
(2) the method utilizes the actually measured load data of the representative day and adopts a backward-stage forward-pushing method to obtain the theoretical line loss of the whole distribution room, thereby having certain innovation value;
(3) the invention considers the complexity of the low-voltage distribution network line structure, and provides a high-precision calculation method based on engineering application requirements, thereby having higher application and popularization values.
Drawings
Fig. 1 is a schematic diagram of a typical low-voltage distribution area network topology.
The details of the present invention are explained in further detail below with reference to the drawings and examples.
Detailed Description
The following embodiments of the present invention are provided, and it should be noted that the present invention is not limited to the following embodiments, and all equivalent changes based on the technical solutions of the present invention are within the protection scope of the present invention.
Example (b):
the embodiment provides a method for calculating theoretical line loss of a low-voltage distribution network, which is characterized by comprising the following steps of:
step 1, selecting a typical low-voltage transformer area optionally, and constructing a network topological structure of the typical low-voltage transformer area;
the typical low-voltage transformer area refers to an area in which any transformer in the prior art supplies power at a low voltage, and fig. 1 shows a network topology structure of the typical low-voltage transformer area constructed in the embodiment;
step 2, obtaining current, voltage, total active power, total reactive power and phase angle of each branch at a point-in-time moment in the constructed typical low-voltage transformer area network topological structure;
as shown in fig. 1, a three-phase smart meter is installed at the head end of a feeder line, a single-phase or three-phase electric energy meter is installed at the load end of each terminal branch, and electric energy data of the smart meter are all time accumulated values, so that the three-phase imbalance degree cannot be estimated. Therefore, data representing 24-hour integral point data of a day needs to be selected, and the branch line power quality monitoring equipment monitors the data to obtain data of the three-phase imbalance degree.
Assuming that the constructed typical low-voltage distribution area network topology structure comprises I branches, wherein I is a natural number greater than 1; calculating phase line loss and neutral line loss of each branch circuit through current, voltage, total active power, total reactive power and phase angle of each branch circuit at each metering interval time t;
optionally selecting one branch I, I-1, 2, from the I branches;
if the branch i is a terminal branch, calculating the phase line loss and the neutral line loss of the branch i by using the formula (1):
Figure BDA0001813592740000091
Figure BDA0001813592740000092
in the formula (1), Δ ALiA，ΔALiBAnd Δ ALiCRespectively representing phase line losses of A phase, B phase and C phase of the branch i,APiA、APiBand APiCThe sum of active electric quantity of the A phase, the B phase and the C phase of the branch circuit i is expressed as kWh; a. theQiA、AQiBAnd AQiBThe sum of the reactive electric quantities of the A phase, the B phase and the C phase of the branch circuit i is represented by kvarh; u shapeavgLiA、UavgLiBAnd UavgLiCThe average value of the operating voltage of the A phase, the B phase and the C phase of the branch circuit i in the measurement interval time is represented by kV; t is the measurement interval time, and the unit is h; rLiΦThe phase line impedance of the branch i is in omega;
in the formula (2), Δ ALiNRepresents the centerline loss, I, of branch IavgLiNThe average current of the middle line of the branch i in the metering interval time is A; r isLiNIs the impedance of the midline line of the branch i, with the unit of omega;
in fig. 1, a branch 2 (typical load 1) is a terminal branch, and a three-phase unbalanced line loss of the branch 2 is calculated by taking the branch 2 as an example, that is, a neutral loss of the branch 2 is:
Figure BDA0001813592740000093
wherein R isL2NThe impedance of the neutral line of the branch 2 is obtained according to cable parameters such as the line diameter and the length of the neutral line conductor.
In the embodiment, load current is transmitted on a transmission cable from a head end to a user end of a distribution area to generate voltage drop, PCC voltage can be increased by the aid of injection power of a distributed power supply along with the fact that distributed new energy is connected into an active power distribution network formed by the distributed new energy, power flow has obvious influence on distribution of line voltage of the distribution area, influence of voltage deviation on line loss is more complicated, line voltage is approximately considered to be equal in a theoretical line loss calculation process of a traditional equivalent resistance method, accuracy of an algorithm is reduced by the aid of the approximation method, and operation is performed according to actual voltage data of key monitoring points of a line.
Branch 2 belongs to a typical three-phase utility load, which is balanced regardless of the additional losses due to three-phase imbalance, namely:
Figure BDA0001813592740000101
wherein A isP2A，AP2B,AP2CA, B, C phases total active power of branch 2,
AQ2A,AQ2B,AQ2Ca, B, C three-phase total reactive power of branch 2; u shapeavgL2A,UavgL2B,UavgL2CThe three-phase load of the branch A, B, C represents the average value of the integral phase voltage at 24 hours a day; t is the metering time; rL2ΦThe phase line impedance for leg 2.
On the other hand, if the branch i is not a terminal branch, and the branch i includes the preceding branches i.j, j is 1,2, and m is the number of preceding branches of the branch i, the phase line loss of the branch i is obtained by equation (3):
Figure BDA0001813592740000111
in the formula (3), Δ ALiA，ΔALiBAnd Δ ALiCPhase line losses of an A phase, a B phase and a C phase of the branch i are respectively represented; a. thePi.jA、APi.jBAnd APi.jCThe sum of active electric quantities of the phase A, the phase B and the phase C of the front branch i.j is expressed in kWh; a. theQi.jA、AQi.jBAnd AQi.jCThe sum of reactive electric quantities of the A phase, the B phase and the C phase of the front-stage branch i.j is represented by kvarh; u shapeavgi.jA、Uavgi.jBAnd Uavgi.jCThe average value of the operating voltages of the phase A, the phase B and the phase C of the preceding branch i.j in the measurement interval time is represented by kV; t is the measurement interval time, and the unit is h; rLiΦThe phase line impedance of the branch i is in omega;
obtaining the effective value of the neutral current of the branch i by the formula (4):
Figure BDA0001813592740000112
in the formula (4), INLiEffective value of neutral current of branch I, IΦLiAn，IΦLiBnAnd IΦLiCnRespectively representing the phase current values of the branch i at n moments, wherein the unit is A;
the neutral line loss of branch i is obtained by equation (5):
Figure BDA0001813592740000113
in the formula (5), Δ ALiNIs the neutral loss of branch I, IavgLiNThe average current of the middle line of the branch i in the metering interval time is A; rLiNThe impedance of the neutral line of branch i is given in Ω.
Typical loads 2 and 3 connected to the rear stage of a branch 3 in the figure 1 are single-phase power loads, the problem of three-phase imbalance exists in the randomness of power consumption time, and the three-phase imbalance degree and the average current I of an N line are measured based on the daily load data represented by a field power monitoring instrumentavgL3.1NAnd IavgL3.2N。
The line loss of the N line of the load foreline branch 3.1 is as follows:
Figure BDA0001813592740000125
wherein R isL3.1NIs the N line impedance of branch 3.1.
The phase line losses of branch 3.1 are:
Figure BDA0001813592740000121
wherein A isP3.1A，AP3.1B,AP3.1C,AQ3.1A,AQ3.1B,AQ3.1CTotal active electric quantity and reactive electric quantity measured by A, B, C three-phase single-phase electric meters respectively; u shapeavgL3.1A,UavgL3.1B,UavgL3.1CThe actual average voltage of each phase line of the branch 3.1; t is the metering time; rL3.1ΦIs the impedance of a 3.1 phase line of the branch circuit;
the calculation method of the branch 3.2 is the same as that of the branch 3.1.
For branch 3, the current flowing through branch A, B, C, N is the superposition of the corresponding current waveforms of branch 3.1 and branch 3.2.
The phase of the in-phase waveforms of branch 3.1 and branch 3.2 are slightly different, and therefore, the sum can be approximated as a linear sum, that is, the A, B, C phase loss of branch 3 can be expressed as:
Figure BDA0001813592740000122
Figure BDA0001813592740000123
Figure BDA0001813592740000124
wherein R isL3ΦThe line impedance of the phase line of leg 3.
And for the neutral line N, adding the same-phase current effective values of the two branch lines according to the three-phase current effective values of the loads 2 and 3 measured at the 24-hour integral point on the representative day to obtain the A, B, C phase current effective value at the 24-hour integral point on the representative day of the previous branch line 3.
The effective value of the N-line current at the integer point of branch 3 can be easily calculated by A, B, C phase vector addition:
Figure BDA0001813592740000131
wherein n is an integer of 0-24 and represents integer data; i isΦL3An,IΦL3Bn,IΦL3CnRespectively represents effective values of phase currents at n moments of three phases,
Figure BDA0001813592740000132
the phase angle information can be obtained by the electric energy monitoring instrument.
Averaging the integral point data to obtain the effective value I of the average current of the N linesavgL3N. The N line losses for branch 3 are therefore:
Figure BDA0001813592740000133
wherein R isL3NIs the N line impedance of leg 3.
The phase line loss of branch 3 can be calculated by:
Figure BDA0001813592740000134
wherein, IavgL3A,IavgL3B,IavgL3CThe average values of the representative daily integral point phase current effective values of A, B, C three phases in the branch 3 are obtained by averaging after summing according to integral point actual measurement data of the rear-stage loads 2 and 3; rL3ΦIs the phase line impedance of leg 3.
For the system of distributed power supply access, in addition to the same problems as the typical loads 2, 3 and 4, the problem of voltage deviation exists in the power distribution network of distributed new energy access, and the loss calculation method considering the voltage deviation is also discussed in the foregoing. By representing daily integral point data measurement, statistical data of three-phase injection current and three-phase imbalance state can be obtained, and then a backward stage forward pushing method is used for calculating the theoretical line loss of the transformer area.
For the preceding stages of branches 2, 3, 4: for branch 1, the current data and three-phase imbalance depend on the effective value data of three-phase current at 24 hours on day of the next stage. These data are obtained by measurement and calculation in the manner described above. The integral point phase current effective value of the branch 1 can be obtained by superposing the integral point phase current of each phase of each branch. By vector addition, the integral point data of the effective value of the N-line current can be calculated, and the line loss of the branch 1 considering three-phase unbalance and voltage deviation can be further solved.
Step 3, acquiring the k-th harmonic current content of each branch, wherein k is less than or equal to 50, and calculating phase line additional loss and neutral line additional loss generated by k-th harmonic in each branch according to the phase line loss and neutral line loss of each branch;
the problem of steady state power quality influencing line loss of a low-voltage distribution network is that harmonic waves are one of important influencing factors besides three-phase imbalance and voltage deviation.
For any one of the typical loads in fig. 1, by analyzing the load impedance characteristics theoretically, and combining with the harmonic measurement conducted on the representative day site, the harmonic content of A, B, C phase lines and N lines can be estimated. In the embodiment, based on the harmonic content characteristic data of the typical load, the estimation value of the harmonic content of each branch at the front stage is obtained by a backward stage forward-pushing method, so that the loss of the harmonic additional line is calculated.
For the harmonic content of a typical load, only the higher order harmonics are usually taken. The harmonic loss is calculated by an improved equivalent resistance method which is independent of consideration of three-phase unbalance and voltage deviation, and the harmonic line loss of each order with high three-phase content is calculated respectively. In this embodiment, the k-th harmonic is taken as an example to describe a calculation process of the harmonic additional line loss, and the other typical harmonics can be calculated by the same method, and the final results are summed.
Optionally selecting one branch I, I-1, 2, from the I branches;
if the branch i is a terminal branch, obtaining the phase line additional loss of the branch i generated by the k-th harmonic by the formula (6):
Figure BDA0001813592740000151
in the formula (6), Δ AkLiA、ΔAkLiBAnd Δ AkLiCAdditional loss of phase line of A-, B-and C-phases due to k-th harmonic for branch i ηkLiA、ηkLiBAnd ηkLiCThe content of k-th harmonic in the branch i; rkLiΦThe k-th harmonic equivalent impedance of the branch i is in unit of omega;
if branch i is not the terminal branch, and branch i includes branch i.j and branch i.m, then the phase line parasitic loss of branch i due to the k-th harmonic is obtained by equation (7):
Figure BDA0001813592740000152
in the formula (7), IkLiA、IkLiBAnd IkLiCThe effective values of the k-th harmonic current of the A phase, the B phase and the C phase in the branch circuit i are obtained;
Figure BDA0001813592740000153
in the formula (8), IkLi.jA、IkLi.jBAnd IkLi.jCThe effective values of k-th harmonic currents of the A phase, the B phase and the C phase in the branch i.j; i iskLi.mA、IkLi.mBAnd IkLi.mCThe effective values of k-order harmonic currents of an A phase, a B phase and a C phase in a branch i.m;
IkLiNthe effective value of k-th harmonic current in a line in a branch i is as follows:
IkLiN＝||IkLiA∠0°+IkLiB∠-120°+IkLiC∠120°|| (9)。
taking branch 3 and its subsequent stages as an example, the three-phase k-th harmonic content of a typical load 2 and branch 3.1, respectively, is ηkL3.1A,ηkL3.1B,ηkL3.1CAnd then the effective value of the three-phase k-th harmonic is:
Figure BDA0001813592740000161
Figure BDA0001813592740000162
Figure BDA0001813592740000163
the k-th harmonic parasitic loss for leg 3.1 phase can be expressed as:
Figure BDA0001813592740000164
Figure BDA0001813592740000165
Figure BDA0001813592740000166
wherein the content of the first and second substances,
Figure BDA0001813592740000167
is the k harmonic equivalent impedance of branch 3.1; the k-th harmonic parasitic loss expression for branch 3.2 is obtained in the same way.
The k-th harmonic currents of the branches 3.1 and 3.2 are superposed to form the k-th harmonic current of the preceding branch 3. After the two branches are superposed, the three-phase k-th harmonic effective value of the preceding branch 3 is superposed with the k-th harmonic effective value of the following branch:
IkL3A＝IkL3.1A+IkL3.2A
IkL3B＝IkL3.1B+IkL3.2B
IkL3C＝IkL3.1C+IkL3.2C
for the N line k harmonic current of foreline branch 3, A, B, C is the vector sum of the line k harmonic currents. For the phase line k subharmonic component, the effective value of the subharmonic on the N line of branch i can be found by the following formula.
IkLiN＝||IkLiA∠0°+IkLiB∠-120°+IkLiC∠120°||
For k-order harmonic current which is formed into a preceding-stage branch 1 after the harmonic currents of the similar branch 3, the similar branch 2 and the similar branch 4 are superposed, the phase line can be calculated by the method, and the harmonic currents are directly superposed; and calculating the additional line loss of the k-th harmonic of all the lines by forward calculation of the rear-stage branch of the line, calculating other harmonics respectively, and calculating the additional loss of the harmonics as the additional quantity of the total loss of the transformer area into a phase line equivalent resistance calculation formula.
And 4, calculating phase line equivalent resistance and neutral line equivalent resistance in the constructed typical low-voltage distribution area network topological structure according to the phase line loss, the phase line additional loss, the neutral line loss and the neutral line additional loss of each branch, and obtaining the line loss of the typical low-voltage distribution area.
Calculating phase line equivalent resistance and middle line equivalent resistance in the constructed typical low-voltage transformer area network topological structure by the formula (10):
Figure BDA0001813592740000171
in the formula (10), RLeqΦIs a phase line equivalent resistor, RLeqNA neutral equivalent resistance; a. thePiAThe sum of the active electric quantity of the branch i is represented by kWh; a. theQiAThe sum of the reactive electric quantities of the branch i is represented by kvarh; u shapeavgiAThe average value of the operating voltage of the branch i in the measurement interval time is represented by kV; t is the measurement interval time, and the unit is h; rLiΦThe phase line impedance of the branch i is in omega; delta AkLiΦAdditional loss of phase line due to k-th harmonic for branch i ∑ Δ AkLiΦThe sum of the additional losses of the phase line generated by each subharmonic for the branch i; a. thePΣΦThe total active electric quantity of a typical low-voltage transformer area is the total; a. theQΣΦThe total reactive power quantity of a typical low-voltage transformer area is the sum; u shapeΦΣThe average value of the voltage of the phase line of the typical low-voltage transformer area is shown; sigma Delta ALNTotal parasitic loss of neutral; i isavgNΣThe average value of the total current of the neutral line is obtained.
In this example APΣΦ、AQΣΦ、UΦΣThe measurement result is directly obtained by a three-phase electric meter arranged on a trunk line in the figure 1.
By means of the formula (10), three-phase imbalance, voltage deviation and harmonic factors are considered in the theoretical line loss calculation, the calculation process is simplified, the speed of calculating the electric energy quality additional line loss is increased, the method is easy to achieve, and compared with a traditional equivalent resistance method and an existing improved algorithm, the method can obtain higher accuracy.

Claims (2)

1. A low-voltage distribution network theoretical line loss calculation method is characterized by comprising the following steps:
step 1, selecting a typical low-voltage transformer area optionally, and constructing a network topological structure of the typical low-voltage transformer area;
step 2, obtaining current, voltage, total active power, total reactive power and phase angle of each branch at a point-in-time moment in the constructed typical low-voltage transformer area network topological structure;
assuming that the constructed typical low-voltage distribution area network topology structure comprises I branches, wherein I is a natural number greater than 1; calculating phase line loss and neutral line loss of each branch circuit through current, voltage, total active power, total reactive power and phase angle of each branch circuit at each metering interval time t;
step 3, calculating phase line additional loss and neutral line additional loss generated by k-th harmonic in each branch according to phase line loss and neutral line loss of each branch in the constructed typical low-voltage transformer area network topological structure, wherein k is less than or equal to 50;
step 4, calculating phase line equivalent resistance and neutral line equivalent resistance in the constructed typical low-voltage transformer area network topological structure according to phase line loss, phase line additional loss, neutral line loss and neutral line additional loss of each branch, and obtaining theoretical line loss of the low-voltage distribution network;
through electric current, voltage, total active power, total reactive power and the phase angle of each branch road integer point moment, calculate the phase line loss and the well line loss of branch road i, include:
optionally selecting one branch I, I-1, 2, from the I branches;
if the branch i is a terminal branch, calculating the phase line loss and the neutral line loss of the branch i by using the formula (1):
Figure FDA0002462782930000021
Figure FDA0002462782930000022
Figure FDA0002462782930000023
Figure FDA0002462782930000024
in the formula (1), Δ ALiA，ΔALiBAnd Δ ALiCRepresenting the phase losses of phase A, B and C of branch i, respectively, APiA、APiBAnd APiCThe sum of active electric quantity of the A phase, the B phase and the C phase of the branch circuit i is expressed as kWh; a. theQiA、AQiBAnd AQiBThe sum of the reactive electric quantities of the A phase, the B phase and the C phase of the branch circuit i is represented by kvarh; u shapeavgLiA、UavgLiBAnd UavgLiCThe average value of the operating voltage of the A phase, the B phase and the C phase of the branch circuit i in the measurement interval time is represented by kV; t is the measurement interval time, and the unit is h; rLiΦThe phase line impedance of the branch i is in omega;
in the formula (2), Δ ALiNRepresents the centerline loss, I, of branch IavgLiNThe average current of the middle line of the branch i in the metering interval time is A; r isLiNIs the impedance of the midline line of the branch i, with the unit of omega;
if the branch i is not a terminal branch, and the branch i includes a preceding branch i.j, j is 1,2,.., m, and m is the number of preceding branches of the branch i, the phase line loss of the branch i is obtained by equation (3):
Figure FDA0002462782930000031
in the formula (3), Δ ALiA，ΔALiBAnd Δ ALiCPhase line losses of an A phase, a B phase and a C phase of the branch i are respectively represented; a. thePi.jA、APi.jBAnd APi.jCThe sum of active electric quantities of the phase A, the phase B and the phase C of the front branch i.j is expressed in kWh; a. theQi.jA、AQi.jBAnd AQi.jCThe sum of reactive electric quantities of the A phase, the B phase and the C phase of the front-stage branch i.j is represented by kvarh; u shapeavgi.jA、Uavgi.jBAnd Uavgi.jCThe average value of the operating voltages of the phase A, the phase B and the phase C of the preceding branch i.j in the measurement interval time is represented by kV; t is the measurement interval time, and the unit is h; rLiΦThe phase line impedance of the branch i is in omega;
obtaining the effective value of the neutral current of the branch i by the formula (4):
Figure FDA0002462782930000032
in the formula (4), INLiEffective value of neutral current of branch I, IΦLiAn，IΦLiBnAnd IΦLiCnRespectively representing the phase current values of the branch i at n moments, wherein the unit is A;
the neutral line loss of branch i is obtained by equation (5):
Figure FDA0002462782930000033
in the formula (5), Δ ALiNIs the neutral loss of branch I, IavgLiNThe average current of the middle line of the branch i in the metering interval time is A; rLiNIs the impedance of the midline line of the branch i, with the unit of omega;
the phase line additional loss and the neutral line additional loss generated by the k-th harmonic in each branch are calculated according to the phase line loss and the neutral line loss of each branch, and the method comprises the following steps:
optionally selecting one branch I, I-1, 2, from the I branches;
if the branch i is a terminal branch, obtaining the phase line additional loss of the branch i generated by the k-th harmonic by the formula (6):
Figure FDA0002462782930000041
in the formula (6), Δ AkLiA、ΔAkLiBAnd Δ AkLiCAdditional loss of phase line of A-, B-and C-phases due to k-th harmonic for branch i ηkLiA、ηkLiBAnd ηkLiCThe content of k-th harmonic in the branch i; rkLiΦThe k-th harmonic equivalent impedance of the branch i is in unit of omega;
if branch i is not the terminal branch, and branch i includes branch i.j and branch i.m, then the phase line parasitic loss of branch i due to the k-th harmonic is obtained by equation (7):
Figure FDA0002462782930000042
in the formula (7), IkLiA、IkLiBAnd IkLiCThe effective values of the k-th harmonic current of the A phase, the B phase and the C phase in the branch circuit i are obtained;
Figure FDA0002462782930000051
in the formula (8), IkLi.jA、IkLi.jBAnd IkLi.jCThe effective values of k-th harmonic currents of the A phase, the B phase and the C phase in the branch i.j; i iskLi.mA、IkLi.mBAnd IkLi.mCThe effective values of k-order harmonic currents of an A phase, a B phase and a C phase in a branch i.m;
IkLiNthe effective value of k-th harmonic current in a line in a branch i is as follows:
IkLiN＝||IkLiA∠0°+IkLiB∠-120°+IkLiC∠120°|| (9)。
2. the theoretical line loss calculation method for the low-voltage distribution network according to claim 1, wherein the phase line equivalent resistance and the middle line equivalent resistance in the constructed typical low-voltage distribution network topology are calculated by the following formula (10):
Figure FDA0002462782930000052
in the formula (10), RLeqΦIs a phase line equivalent resistor, RLeqNA neutral equivalent resistance; a. thePiAThe sum of the active electric quantity of the branch i is represented by kWh; a. theQiAThe sum of the reactive electric quantities of the branch i is represented by kvarh; u shapeavgiAThe average value of the operating voltage of the branch i in the measurement interval time is represented by kV; t is the measurement interval time, and the unit is h; rLiPhi is the phase line impedance of the branch i and the unit is omega; delta AkLiΦAdditional loss of phase line due to k-th harmonic for branch i ∑ Δ AkLiΦThe sum of the additional losses of the phase line generated by each subharmonic for the branch i; a. thePΣΦThe total active electric quantity of a typical low-voltage transformer area is the total; a. theQΣΦThe total reactive power quantity of a typical low-voltage transformer area is the sum; u shapeΦΣThe average value of the voltage of the phase line of the typical low-voltage transformer area is shown; sigma Delta ALNTotal parasitic loss of neutral; i isavgNΣAverage value of the total current of the neutral line.
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CN110780114A (en) * 2019-11-01 2020-02-11 国网重庆市电力公司电力科学研究院 Transformer area theoretical line loss analysis method and readable storage medium
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CN113507108A (en) * 2021-06-08 2021-10-15 西安理工大学 Power distribution network line loss estimation method based on region division
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CN115201742B (en) * 2022-09-16 2023-01-24 北京志翔科技股份有限公司 Method and device for determining error of metering point of low-voltage transformer area and electronic equipment

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106992517A (en) * 2017-04-28 2017-07-28 国网山东省电力公司莱西市供电公司 Electric power line loss analysis method, device and system
CN107046286A (en) * 2017-05-12 2017-08-15 国网上海市电力公司 Low-voltage power distribution station area theoretical line loss caluclation method based on forward-backward sweep method
CN107093897A (en) * 2017-05-13 2017-08-25 国网安徽省电力公司芜湖供电公司 A kind of distribution net platform region low pressure loss analysis method
CN108335229A (en) * 2018-01-25 2018-07-27 国网浙江海宁市供电有限公司 A kind of theoretical line loss caluclation method based on power grid operation data

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106992517A (en) * 2017-04-28 2017-07-28 国网山东省电力公司莱西市供电公司 Electric power line loss analysis method, device and system
CN107046286A (en) * 2017-05-12 2017-08-15 国网上海市电力公司 Low-voltage power distribution station area theoretical line loss caluclation method based on forward-backward sweep method
CN107093897A (en) * 2017-05-13 2017-08-25 国网安徽省电力公司芜湖供电公司 A kind of distribution net platform region low pressure loss analysis method
CN108335229A (en) * 2018-01-25 2018-07-27 国网浙江海宁市供电有限公司 A kind of theoretical line loss caluclation method based on power grid operation data

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