CN104158173A - Method for calculating voltage-drop line loss rate based on load measurement and calculation - Google Patents

Abstract

The invention discloses a method for calculating the voltage-drop line loss rate based on load measurement and calculation, and the method is applied to calculation of the theoretical line loss of 10kV (and lower) power distribution network. The concept of a load gravity-center coefficient is introduced into the method, and steps for calculating the load gravity-center coefficient and the theoretical line loss via synchronous data are illustrated. Tedious preparation for measurement and calculation is not required, influence on aging, temperature, three-phase imbalance and power factor of the lines can be reflected, and accurate real-time dynamic results can be obtained by following real-time dynamic load change and trend. The method can be used to obtain data from a power data system, or embedded to online measuring equipment to realize real-time calculation.

Description

A kind of pressure drop line loss rate computational methods based on load measuring and calculating

Technical field

The present invention is a kind of computational methods of the following distribution network theory wire loss of 10kV (containing 10kV).

Background technology

In power distribution network (the following electric pressure of 10kV and 10kV) supply of electric power process, power distribution network produces inevitable energy loss, and this energy loss is called line loss in power system power supply process.Line loss rate=(line loss ÷ amount of power supply) × 100%, line loss rate is the important economic index of the design of reflection power network planning, operation and management level, is that power supply department must be examined one of important indicator.

Line loss is containing theory wire loss and management line loss.

In the time of power distribution network transferring electric power; electric current can produce inevitable energy loss during by wire; in addition; the requisite equipment such as transformer in power distribution network, protection switch, instrument also can produce power loss, and above energy loss is called theory wire loss (being also referred to as technical loss).Management line loss is that the energy loss causing with other unknown cause is not good in management work.

In power grid operation, management has important references meaning to line losses indices for theory wire loss and Molded Line loss rate, has also reflected economy and the reasonability of the normal operation of electrical network.

Power supply department obtains the main Shi Tai of method district proportion of goods damageds method, software theory calculating, the measuring and calculating of droop loss rate method of power distribution network theory wire loss at present.

Platform district proportion of goods damageds method is to choose harmless Typical Route, by representing that day electricity sales amount of statistics platform district electrical networks at different levels and the difference of power consumption obtain line loss and line loss rate, go to calculate as typical line loss, it is comparatively harsh that this method relies on condition, cycle is long, to represent the simplification computational methods of daily load as sustained load.

Software theory calculates several different methods, as rms current method, average current method, coulometry, these methods first all need to try to achieve substitutional resistance, and substitutional resistance needs mass data to calculate, as topological structure of electric, line parameter circuit value, electric weight, capacity etc.Substitutional resistance has reflected the static result under electrical network normal condition in principle, but is not enough to obtain significant accuracy for circuit actual motion state (as aging circuit, load variations, temperature).

Existing droop loss rate Fa Shitai district electrical network busy hour is surveyed record to circuit first and end voltage, and its voltage difference is loss late with outlet voltage ratio, is aided with power factor (PF), amount of power supply, empirical equation and obtains line loss and line loss rate.This method realization condition is also harsher, and cannot reflect the situation that different load changes, and accuracy is inadequate.

Summary of the invention

In order to overcome the measuring and calculating process complexity of existing line loss, circuit virtual condition to be reflected to deficiency sensitive not, measuring and calculating excessive cycle, the invention provides a kind of pressure drop line loss rate computational methods based on load measuring and calculating, be used for the theoretical line rate of quick, accurate, real-time calculating and theory wire loss.

The model that the present invention adopts power distribution network to simplify, use measurable synchrodata assumed (specified) load barycentric coefficients, synchrodata is the outlet voltage of power distribution network and the voltage of load representative point (load representative point quantity is not less than 5), these voltages are measured at synchronization, calculate equivalent load center of gravity as same group of data, obtain real-time Molded Line loss rate and theory wire loss in conjunction with droop loss rate method.

Fig. 1 power distribution network naive model

The voltage drop of first and last end can be expressed as:

(formula 1)

The voltage drop of resistance R is parallel to electric current the pressure drop ratio electric current and reactance powers on leading 90 °.Voltage drop absolute value is approximately equal to length on real axis:

(formula 2)

Voltage drop percentage is expressed as:

(formula 3)

Electric energy loss power percentage is:

(formula 4)

Represent the ratio of voltage grid line loss electric weight and the loss of voltage with COEFFICIENT K p, can be expressed as:

(formula 5)

Usage factor Kp can measure the line loss electric weight that calculates this net on the basis of the low voltage electric network loss of voltage again.This low voltage electric network head end voltage U of sampling measurement ₁, terminal voltage U ₂and power factor, the voltage drop obtaining:

$\mathrm{\ΔU}=\frac{U_1-U_2}{U_1}\×100\%$ (formula 6)

By a COEFFICIENT K being determined by low voltage electric network (mainly) wire size _pthe line loss rate of estimating this net is:

Δ P _d=K _p× Δ U (formula 7)

Above-mentioned line loss computational process only considers that line end has the situation of a concentrfated load, is equivalent to load gravity center and is distributed in line end.Actual track distributed load day part difference, circuit branch is also not quite similar, and is incorporated herein load gravity center COEFFICIENT K e and solves load actual distribution situation.

Load gravity center COEFFICIENT K e simplifies computation model as shown in Figure 2, circuit head end (in Fig. 2 1) and line end (in Fig. 2 2) voltage difference is U, circuit head end total current is I, circuit all-in resistance is R, be uniformly distributed in situation if circuit is load, resistance is divided into N equal portions, as (in Fig. 2 3), every equal portions resistance is r (r=R/N), and it is I/N that equal portions resistance as every in (in Fig. 2 4) flows out electric current.

: I1=I I2=I × (N-1)/N...IN-1=I × 2/N IN=I/N

I.e.: In=I × (N-n)/N (n=[0, N-1])

: any one section of line loss Δ Pn=In × In × r=I ²× R × (N-n) ²/ N ³

: total line loss $\mathrm{\ΔP}=I^2\×R\×\frac{[{\left(\frac{1}{N}\right)}^2+{\left(\frac{2}{N}\right)}^2+...+{\left(\frac{(N-1)}{N}\right)}^2+1]}{N}=U\×I\×\mathrm{Ke}$

Definition $\mathrm{Ke}=[{\left(\frac{1}{N}\right)}^2+{\left(\frac{2}{N}\right)}^2+...+{\left(\frac{(N-1)}{N}\right)}^2+1]/N$ (formula 8)

Be evenly distributed in situation: lim _{n → ∞}ke=1/3

In conjunction with formula 7: Δ P _d=K _p× Δ U × Ke (formula 9)

Power distribution network theory wire loss computational methods provided by the invention comprise following steps:

(1) obtain the synchrodata of data collection cycle, the outlet of packet Han Tai district each meritorious amount of power supply, idle amount of power supply, voltage, electric current, power factor mutually.

(2) obtain each load representative point synchrodata that collection period is synchronizeed with step (1), packet is containing each phase voltage, electric current, power factor.

(3) by the average power factor of separate calculating collection period (have, idle amount of power supply calculate), if collection period is the minimum period, step (3) can be ignored.

(4) calculate each phase K by formula 5 _p.

(5) calculate each phase Ke by formula 8.

(6) calculate each phase Molded Line loss rate by formula 9.

(7) calculate the theory wire loss electric weight of each phase.

(8) cumulative each phase theory wire loss electric weight, obtains the theory wire loss electric weight of this collection period.

(9) the theory wire loss electric weight result of use step (8), in conjunction with the meritorious amount of power supply of three-phase, obtains the Molded Line loss rate of this collection period.

(10) repeating step (1) is to the evaluation work of step (9).

Compared with prior art, the invention has the beneficial effects as follows: method of the present invention can obtain synchrodata and realize calculating in Power SCADA system, also can be embedded in in-situ measurement equipment and realize in real time and calculating.

This method is prepared without loaded down with trivial details measuring and calculating, can reflect aging, temperature, the three-phase imbalance of circuit, the impact of power factor, follows real-time load dynamic change and the flow direction and obtains accurately dynamic result in real time.

Brief description of the drawings

Fig. 1 power distribution network pressure decline method simplified model figure

Fig. 2 assumed (specified) load center of gravity distribution network line simplified model figure

1 circuit model head end in Fig. 2

2 circuit model ends in Fig. 2

Point substitutional resistance such as 3 circuits in Fig. 2

The evenly lower each branch current of 4 load in Fig. 2

Fig. 3 customer group, user, load group relation figure

1 load group in Fig. 3

2 customer groups in Fig. 3

3 users in Fig. 3

In Fig. 3,4 users and load are larger

5 customer groups and load group in Fig. 3

embodiment

Below in conjunction with accompanying drawing, the present invention is further described.

First choosing of load representative point be described: power distribution network actual track complexity, distinguish from the structure of circuit, there is dry, branch line, divide into some customer groups (user concentrates user with circuit and connecting line physical distance) from user's concentration degree, distinguish from the angle of the load of circuit, can be divided into some load groups (be that load is larger, account for more than 15% user or the customer group of actual full payload), customer group, user, load group are as Fig. 3.Load representative point is chosen by following principle:

(1) must choose at main line end, all the other representative points are not less than 4.

(2) as You Duotiaochang branch after egress line, each branches end must be chosen

(3), at the even Selecting Representative Points from A of trunk line, by load group, customer group, user's order are chosen.

Next explanation data synchronous error is collection period ± 0.5%, and collection period is not more than 15 minutes.

There are Power SCADA and online equipment by Data Source.

Power SCADA is implemented

(1) from SCADA system, obtain platform district synchrodata, if system data collection point many (much larger than 5 points) do not need to consider line construction, each main line is directly carried out according to calculation procedure.

(2) from SCADA system, obtain platform district synchrodata, if system acquisition point is few, the load of all collection points is greater than platform district load 80% can be calculated according to step, otherwise cannot calculate.

Online equipment is implemented:

(1) after load representative point is chosen by principle, collecting device is arranged on to load representative point.

(2) must there be clock synchronous each collection point, can adopt satellite synchronization, also can adopt the communication modes lock in time of measurable time delay.

(3) embed calculation procedure of the present invention at the collecting device of power distribution network outlet, obtain, after the data of each collection point, calculating by calculation procedure by communication modes.

Claims (6)

1. the pressure drop line loss rate computational methods based on load measuring and calculating, in the following distribution network theory wire loss of 10kV (containing 10kV), use, it is characterized in that: in collection period, obtain one group of measurable synchrodata assumed (specified) load barycentric coefficients, obtain real-time Molded Line loss rate and theory wire loss in conjunction with droop loss rate method, repeating above said collection computational process, can obtain Molded Line loss rate and the theory wire loss of random time section.

2. the collection period in computational methods as claimed in claim 1, is characterized in that: collection period is not more than 15 minutes.

3. the synchrodata in computational methods as claimed in claim 1, is characterized in that: synchrodata must comprise the outlet voltage of power distribution network.

4. the synchrodata in computational methods as claimed in claim 1, is characterized in that: synchrodata must comprise the voltage that is no less than 5 load representative points.

5. the synchrodata in computational methods as claimed in claim 1, is characterized in that: data synchronous error be not more than collection period ± 0.5%.

6. it is characterized in that as claimed in claim 1: