CN102751725A - Overload risk state identifying method for power distribution network - Google Patents

Abstract

The invention discloses an overload risk state identifying method for a power distribution network. Overload indexes are computed by history load information within a certain period before a certain t point, load real-time measurement information at the t point and load prediction information within a certain period after the t point of the power distribution network in an equivalent load method from the aspects of reality, continuity and foreseeability, overload index severity grades are generated, the overload indexes in the aspects of reality, continuity and foreseeability are analyzed according to the overload index severity grades, whether the power distribution network is in an overload risk state at the t point is judged according to the overload risk state judging steps of the power distribution network, and dynamic and continuous overload risk state tracking and identifying of the power distribution network are carried out. The method is suitable for identifying and warning the overload risk state in the self-healing control process of the power distribution network.

Description

A kind of power distribution network overload risk status discrimination method

Technical field

The present invention relates to distribution system analysis and control technology field, be specifically related to a kind of power distribution network overload risk status discrimination method.

Background technology

In power distribution network self-healing control, power supply capacity is to weigh that power distribution network is high-quality and efficient, an important indicator of economic and reliable operation, and power distribution network whether running overload be to weigh the whether sufficient importance of power supply capacity.Fast development along with local economy; The user power utilization load is also in continuous growth; The burden of grid equipment also constantly increases, and the overload risk has become the important risk type that power distribution network faces, how to find the overload risk early; To avoid the serious running overload of power distribution network, be a research content in the assessment of power distribution network self-healing control running status.

At present, the achievement in research of overload risk assessment aspect is a lot of, but all major side overweights from planning angle, static angular the possibility and the order of severity thereof that the overload risk takes place are carried out analysis-by-synthesis.In practical application, mainly estimate the overload level from overload multiple and permission overload times two aspect, the accuracy of its evaluation result and reliability are all very poor.

Summary of the invention

Deficiency to existing achievement in research; The present invention proposes a kind of overload risk status discrimination method; From operation angle, comprehensively adopt historical load information, actual measurement information on load, load prediction information, the overload risk that power distribution network faces is carried out comprehensively dynamically identification; Can improve accuracy, the reliability of the identification of power distribution network overload risk, initiatively defend to provide foundation for power distribution network carries out the overload risk.

A kind of power distribution network overload risk status discrimination method provided by the invention; Its improvements are; Said method is: adopt power distribution network t constantly before historical load information, t in a certain period load constantly real-time measurement information and t constantly after the load prediction information in the section sometime; With the equivalent load method from the actuality aspect, continuation aspect and foresight aspect calculate the overload index, generates overload index severity grade, and is foundation with said overload index severity grade; Overload index to said actuality aspect, continuation aspect and foresight aspect is analyzed; According to power distribution network overload risk status determining step, judge whether electrical network constantly is in the overload risk status at t, and carry out dynamic Continuous Tracking of power distribution network overload risk status and identification.

Wherein, said actuality is meant the one side that the overload risk has taken place; The overload index step of calculating said actuality aspect is:

According to the historical load information of t in the Δ t1 time before constantly, calculate equivalent load and overload index in the Δ t1 time, to judge the overload situation of t in the Δ t1 time before constantly.

Wherein, said continuation is meant the one side that the overload risk is taking place and will continue; The overload index step of calculating said continuation aspect is:

According to t constantly before a period of time Δ t2 historical load information and with t constantly after the prediction information on load of Δ t3 in a period of time; Calculate equivalent load and overload index in the Δ t2+ Δ t3 time; And combine t actual measurement information on load constantly, to judge t overload constantly and continued case thereof.

Wherein, said foresight is meant the one side that the overload risk takes place in the future or the overload risk can not take place; The overload index step of calculating said foresight aspect is:

According to the prediction information on load of t in the Δ t4 time afterwards constantly, calculate equivalent load and overload index in the Δ t4 time, to judge the overload situation of t in the Δ t4 time afterwards constantly.

Wherein, said power distribution network overload risk status determining step is following:

(1) if actuality overload index, continuation overload index and foresight overload index all do not have the overload phenomenon, judges that then electrical network is in normal operating condition;

(2) if actuality overload index, continuation overload index and foresight overload index have at least a kind of overload phenomenon not serious, the residue index does not all have the overload phenomenon, judges that then electrical network is in normal operating condition;

(3) not serious if the overload phenomenon all appears in actuality overload index, continuation overload index and foresight overload index, judge that then current electrical network is not in the overload risk status, provide overload phenomenon warning message;

(4) if actuality overload index, continuation overload index and foresight overload index have at least a kind of overload phenomenon more serious, judge that then current electrical network is in the overload risk status, provide overload Risk-warning information;

(5) if actuality overload index, continuation overload index and foresight overload index have at least a kind of overload phenomenon serious; Judge that then current electrical network is in the overload risk status; Provide overload Risk-warning information, and formulate overload risk-aversion control strategy.

Wherein, judge whether power distribution network is in the overload risk status constantly at t, if:

Judge that power distribution network is in normal condition; Then judged whether index exceeding standard; If no index exceeds standard, then obtain again power distribution network t constantly before historical load information, t in a certain period load constantly real-time measurement information and t constantly after the interior load prediction information of section sometime; If index exceeding standard arranged, then add up the index exceeding standard duration, and the index duration is stored and carries out the identification of the risk status of power distribution network overload next time;

Judge that there is the overload phenomenon in power distribution network, but when not reaching risk status, then add up the index exceeding standard duration, and the index duration is stored and carries out the identification of the risk status of power distribution network overload next time;

Judge that there is the overload risk in power distribution network; And according to overload risk class determination methods; Judge that the overload risk is not serious, only carry out the overload risk and report to the police, add up the index exceeding standard duration simultaneously; The index duration is stored, and carry out the identification of the risk status of power distribution network overload next time.

Judge that there is the overload risk in power distribution network, and,, when then carrying out the warning of overload risk, and provide overload risk-aversion control strategy if the overload risk is serious according to overload risk class determination methods; Add up the index exceeding standard duration simultaneously, the index duration is stored, and proceed the continuous identification of overload risk status.

Wherein, said overload index comprises:

1. overload multiple index K---be used to reflect that single load monitoring point surpasses the degree of permissible load, computing formula does;

2. allow overload time index T---be used to reflect overload duration length, with overload multiple index reflection overload degree;

Wherein, the corresponding corresponding overload time index limit value that allows of overload multiple index standard limited value.

3. the overload multiple is to voltage influence index sensitivity index A---and be used to reflect the degree that rate of qualified voltage that overload causes reduces, its calculation expression is:

A＝f(K,ΔR _U)；

Wherein, Δ R _UFor rate of qualified voltage changes; K is the overload multiple;

4. the overload multiple influences index sensitivity index B to line loss---and be used for reflecting the order of severity that line loss rate that overload causes raises, its calculation expression is:

B＝f(K,ΔR _Line-loss)；

Wherein, Δ R _Line-lossFor line loss rate changes; K is the overload multiple;

5. overload rate index R _Over-load---be used to reflect single load monitoring point overload time degree in the monitoring time section, its expression formula is:

6. comprehensive overload rate index CR _Over-load---be used for reflecting the size of part or overall overload scope, its expression formula is:

Wherein, the step of calculating equivalent load is:

If t had n discrete load in the Δ T time before or after the moment, load value is respectively P ₁, P ₂..., P _n, adopt following formula to calculate t equivalent load value P constantly _t:

(1) utilize the arithmetic average method to ask secondary equivalent load P _tComputing formula following:

$P_t=\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{P}_i}{n}=\frac{P_1+P_2+...+P_n}{n}---1)$

(2) utilize the arithmetic average method to ask secondary equivalent load P _tComputing formula following:

$P_t=\sqrt{\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{P}_i^2}{n}}=\sqrt{\frac{P_1^2+P_2^2+...+P_n^2}{n}}---2)$

(3) utilize the geometric mean method to ask secondary equivalent load P _tComputing formula following:

$P_t=\sqrt[n]{P_1\×P_2\×...\×P_n}---3)$ Or

(4) utilize the harmonic-mean method to ask secondary equivalent load P _mComputing formula following:

$P_t=\frac{n}{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\frac{1}{P_i}}=\frac{n}{\frac{1}{P_1}+\frac{1}{P_2}+...+\frac{1}{P_n}}---4).$

Wherein, said load prediction isoeffect curve is according to said formula 1)-formula 4) curve that is linked to be of the different equivalent load values constantly that calculate.The present invention also can first off-line according to formula 1)-4) calculate the equivalent load load prediction isoeffect curve that draws, then the online application of load prediction isoeffect curve (promptly being applied to the equivalent load of foresight aspect) is got final product, saved time in line computation.

With the prior art ratio, beneficial effect of the present invention is:

The comprehensive historical load information of the method for the invention, actual measurement information on load, load prediction information; Realize attitude, various dimensions, dynamic overload risk identification for a long time; The gained result comprehensively, accurately, reliably realizes that for power distribution network self-healing control the active defence of overload risk provides reliable basis.

The calculating equivalent load that the present invention proposes is converted into an equivalent load point with a plurality of load point in any Δ T period, simplifies the simulation calculating number of times thereby reach, more the purpose of the observation of visual and clear load dynamic trend.And it has utilized arithmetic average method, square mean to count method, geometric mean method and harmonic-mean fado kind average method and has obtained equivalent load, and its amount of calculation is little, and is simple to operate.

Description of drawings

Fig. 1 is a kind of power distribution network overload risk identification flow chart provided by the invention.

Embodiment

Do further to specify below in conjunction with the accompanying drawing specific embodiments of the invention.

A kind of power distribution network overload risk status discrimination method provided by the invention; It is to adopt power distribution network t (this time period user oneself is definite in a certain period before constantly; Be generally 1min ~ historical load information 30min), t and load constantly that (this time period user oneself is definite in the section sometime after constantly for real-time measurement information and t; Be generally the load prediction information of 1min ~ 30min); With the equivalent load method from the actuality aspect, continuation aspect and foresight aspect calculate the overload index, generates overload index severity grade, and is foundation with said overload index severity grade; Overload index to said actuality aspect, continuation aspect and foresight aspect is analyzed; According to power distribution network overload risk status determining step, judge whether electrical network constantly is in the overload risk status at t, and carry out dynamic Continuous Tracking of power distribution network overload risk status and identification.Power distribution network overload risk identification flow process is as shown in Figure 1, specifically comprises the steps:

(1) obtain power distribution network t constantly before historical load information, t in a certain period load constantly real-time measurement information, t constantly after the load prediction information in the section sometime;

(2) calculate needed historical load data and load prediction data with the equivalent load method;

(3) the overload index of calculating actuality, continuation, three aspects of foresight generates overload index severity grade;

(4) be foundation with overload index severity grade, judge actuality, continuation, foresight overload index grade;

(5) according to power distribution network overload risk status identification step, judge whether the current time electrical network is in the overload risk status.

(6) if judge that electrical network is in normal condition, then judged whether index exceeding standard,, then returned step (1) if no index exceeds standard; If index exceeding standard arranged, then add up the index exceeding standard duration, and the index duration is stored, return step (1) simultaneously.

(7) there is the overload phenomenon if judge electrical network, but do not reach the overload risk status, i.e. when overload phenomenon severity grade is 1 grade, the time, then add up the index exceeding standard duration, and the index duration is stored, return step (1) simultaneously.

(8) if judge that there is the overload risk in electrical network; Be that overload phenomenon severity grade is when being 2 grades or 3 grades; When if overload phenomenon severity grade is 2 grades; Continue the accumulative total index exceeding standard duration, and the index duration is stored, return step (1) simultaneously and proceed the continuous identification of overload risk status.

(9) there is the overload risk if judge electrical network, is i.e. when overload phenomenon severity grade is 2 grades or 3 grades,, then carries out the overload risk when reporting to the police, and provide overload risk-aversion control strategy if when overload phenomenon severity grade is 3 grades; Simultaneously, continue the accumulative total index exceeding standard duration, and the index duration is stored, return step (1) simultaneously and proceed the continuous identification of overload risk status.

Wherein:

I. said overload index comprises:

1. overload multiple index K---be used for reflecting that single load monitoring point surpasses the degree of permissible load, computing formula does;

2. allow overload time index T---be used for reflecting overload duration length, with overload multiple index comprehensive reflection overload degree.

Wherein, certain overload multiple index standard limited value correspondence allows overload time index limit value accordingly.

3. the overload multiple is to voltage influence index sensitivity index A---and be used for reflecting the degree that rate of qualified voltage that overload causes reduces, its calculation expression is:

A＝f(K,ΔR _U)

Wherein, Δ R _UFor rate of qualified voltage changes; K is the overload multiple.

4. the overload multiple influences index sensitivity index B to line loss---and be used for reflecting the order of severity that line loss rate that overload causes raises, its calculation expression is:

B＝f(K,ΔR _Line-loss)

Wherein, Δ R _Line-lossFor line loss rate changes; K is the overload multiple.

5. overload rate index R _Over-load---be used for reflecting single load monitoring point overload time degree in the monitoring time section.

6. comprehensive overload rate index CR _Over-load---be used for reflecting the size of part or overall overload scope.

II. in the step (3),

Said actuality is meant the one side that the overload risk has taken place; The overload index step of calculating said actuality aspect is:

Adopt t constantly before Δ t1 (this time period user oneself confirms, is generally the historical load information in the time of 1min ~ 30min), calculates equivalent load and overload index in the Δ t1 time, to weigh the overload situation of t in the Δ t1 time before constantly;

Said continuation is meant that the overload risk is taking place and will the continue a period of time one side of (confirming according to Δ t3); The overload index step of calculating said continuation aspect is:

(this time period user oneself confirms a period of time Δ t2 before the employing t moment; Be generally 1min ~ 30min) historical load information and, t constantly after in a period of time Δ t3 (this time period user oneself is definite; Be generally the prediction information on load of 1min ~ 30min); Calculate equivalent load and overload index in the Δ t2+ Δ t3 time, and with t actual measurement information on load constantly, with comprehensive measurements t moment overload and continued case thereof;

Said foresight is meant the one side that the overload risk takes place in the future or the overload risk can not take place; The overload index step of calculating said foresight aspect is:

Adopt t constantly after Δ t4 (this time period user oneself confirms, is generally the prediction information on load in the time of 1min ~ 30min), calculates equivalent load and overload index in the Δ t4 time, to weigh the overload situation of t in the Δ t4 time afterwards constantly.Wherein, the equivalent load of foresight aspect can also can onlinely calculate according to the said load prediction isoeffect curve value of off-line generation.

III. in step (3), the step of calculating equivalent load is:

Certain is the equivalent load value P of t constantly _tSize and selected time interval Δ T relevant with the Equivalent calculation method that is adopted.If t had n discrete load in the Δ T time before or after the moment, load value is respectively P ₁, P ₂..., P _n, can adopt following 4 kinds of methods to calculate t equivalent load value P constantly _t:

(1) utilize the arithmetic average method to ask secondary equivalent load P _tComputing formula following:

$P_t=\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{P}_i}{n}=\frac{P_1+P_2+...+P_n}{n}---1)$

(2) utilize the arithmetic average method to ask secondary equivalent load P _tComputing formula following:

$P_t=\sqrt{\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{P}_i^2}{n}}=\sqrt{\frac{P_1^2+P_2^2+...+P_n^2}{n}}---2)$

(3) utilize the geometric mean method to ask secondary equivalent load P _tComputing formula following:

$P_t=\sqrt[n]{P_1\×P_2\×...\×P_n}---3)$

(4) utilize the harmonic-mean method to ask secondary equivalent load P _mComputing formula following:

$P_t=\frac{n}{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\frac{1}{P_i}}=\frac{n}{\frac{1}{P_1}+\frac{1}{P_1}+...+\frac{1}{P_n}}---4)$

IV. overload index severity grade is divided into 4 grades, and rank is high more, and the overload phenomenon is serious more, and it is respectively:

(1) no overload phenomenon

Definition: no overload phenomenon, this is 0 grade of overload, power distribution network is in normal operating condition;

Determination methods: all overload indexs are all in normal range (NR), and are no out-of-limit, then are in 0 grade of overload; 0 grade of overload judges that typical case is as shown in table 1.

(2) overload phenomenon is not serious

Definition: the overload phenomenon is not serious, and this is 1 grade of overload, does not think that power distribution network gets into the overload risk status, only carries out overload early-warning;

Determination methods: allow overload multiple index limit value if having only overload multiple index overrun but do not surpass, other overload indexs all in allowable value, then are in 1 grade of overload; 1 grade of overload judges that typical case is as shown in table 1.

(3) overload phenomenon is more serious

Definition: the overload phenomenon is more serious, and this is 2 grades of overloads, thinks that power distribution network gets into the overload risk status, and only carries out the overload Risk-warning, need not to carry out risk-aversion control;

Determination methods: allow overload multiple index limit value if overload multiple index surpasses, and allow the overload time index also to surpass allowable value, other overload index all in allowable value, then is in 2 grades of overloads; 2 grades of overloads judge that typical case is as shown in table 1.

(4) overload phenomenon is serious

Definition: the overload phenomenon is serious, and this is 3 grades of overloads, thinks that power distribution network gets into the overload risk status, and carries out the overload Risk-warning, and formulate overload risk-aversion control strategy;

Determination methods: allow overload multiple index limit value if overload multiple index surpasses, and allow the overload time index also to surpass allowable value, have at least an overload index to exceed allowable value in other overload index, then be in 3 grades of overloads; 4 grade overloads are judged as shown in table 1.

Table 1

V. power distribution network overload risk status identification step comprises in the step (5):

(1) is 0 grade of overload as if actuality overload index, continuation overload index, foresight overload index, thinks that then electrical network is in normal operating condition.

(2) all having a kind of overload index at least as if actuality overload index, continuation overload index, foresight overload index is 1 grade of overload, and all the other indexs are 0 grade of overload, think that then electrical network is in normal operating condition.

(3) be 1 grade of overload as if actuality overload index, continuation overload index, foresight overload index, do not think that then current electrical network is in the overload risk status, at this moment, only provide overload phenomenon warning message, do not think the overload risk.

(4) having a kind of overload index at least as if actuality overload index, continuation overload index, foresight overload index is 2 grades of overloads; Think that then current electrical network is in the overload risk status; Provide overload Risk-warning information simultaneously, but need not to carry out overload risk-aversion control;

(5) having a kind of overload index at least as if actuality overload index, continuation overload index, foresight overload index is 3 grades of overloads; Think that then current electrical network is in the overload risk status; Provide overload Risk-warning information simultaneously; And need to formulate overload risk-aversion control strategy, for the traffic control personnel provide overload risk-aversion control foundation.

In the practical application, can formulate the overload risk determination methods that meets special requirement according to above-mentioned design according to actual needs.

Should be noted that at last: above embodiment is only in order to technical scheme of the present invention to be described but not to its restriction; Although the present invention has been carried out detailed explanation with reference to the foregoing description; Under the those of ordinary skill in field be to be understood that: still can specific embodiments of the invention make amendment or be equal to replacement; And do not break away from any modification of spirit and scope of the invention or be equal to replacement, it all should be encompassed in the middle of the claim scope of the present invention.

Claims (10)

1. power distribution network overload risk status discrimination method; It is characterized in that; Said method is: adopt power distribution network t constantly before historical load information, t in a certain period load constantly real-time measurement information and t constantly after the load prediction information in the section sometime; With the equivalent load method from the actuality aspect, continuation aspect and foresight aspect calculate the overload index, generates overload index severity grade, and is foundation with said overload index severity grade; Overload index to said actuality aspect, continuation aspect and foresight aspect is analyzed; According to power distribution network overload risk status determining step, judge whether electrical network constantly is in the overload risk status at t, and carry out dynamic Continuous Tracking of power distribution network overload risk status and identification.

2. power distribution network overload risk status discrimination method as claimed in claim 1 is characterized in that said actuality is meant the one side that the overload risk has taken place; The overload index step of calculating said actuality aspect is:

According to the historical load information of t in the Δ t1 time before constantly, calculate equivalent load and overload index in the Δ t1 time, to judge the overload situation of t in the Δ t1 time before constantly.

3. power distribution network overload risk status discrimination method as claimed in claim 1 is characterized in that said continuation is meant the one side that the overload risk is taking place and will continue; The overload index step of calculating said continuation aspect is:

According to t constantly before a period of time Δ t2 historical load information and with t constantly after the prediction information on load of Δ t3 in a period of time; Calculate equivalent load and overload index in the Δ t2+ Δ t3 time; And combine t actual measurement information on load constantly, to judge t overload constantly and continued case thereof.

4. power distribution network overload risk status discrimination method as claimed in claim 1 is characterized in that, said foresight is meant the one side that the overload risk takes place in the future or the overload risk can not take place; The overload index step of calculating said foresight aspect is:

According to the prediction information on load of t in the Δ t4 time afterwards constantly, calculate equivalent load and overload index in the Δ t4 time, to judge the overload situation of t in the Δ t4 time afterwards constantly.

5. power distribution network overload risk status discrimination method as claimed in claim 1 is characterized in that, said power distribution network overload risk status determining step is following:

(1) if actuality overload index, continuation overload index and foresight overload index all do not have the overload phenomenon, judges that then electrical network is in normal operating condition;

(2) if actuality overload index, continuation overload index and foresight overload index have at least a kind of overload phenomenon not serious, the residue index does not all have the overload phenomenon, judges that then electrical network is in normal operating condition;

(3) not serious if the overload phenomenon all appears in actuality overload index, continuation overload index and foresight overload index, judge that then current electrical network is not in the overload risk status, provide overload phenomenon warning message;

(4) if actuality overload index, continuation overload index and foresight overload index have at least a kind of overload phenomenon more serious, judge that then current electrical network is in the overload risk status, provide overload Risk-warning information;

(5) if actuality overload index, continuation overload index and foresight overload index have at least a kind of overload phenomenon serious; Judge that then current electrical network is in the overload risk status; Provide overload Risk-warning information, and formulate overload risk-aversion control strategy.

6. power distribution network overload risk status discrimination method as claimed in claim 1 is characterized in that, judges whether power distribution network is in the overload risk status constantly at t, if:

Judge that power distribution network is in normal condition; Then judged whether index exceeding standard; If no index exceeds standard, then obtain again power distribution network t constantly before historical load information, t in a certain period load constantly real-time measurement information and t constantly after the interior load prediction information of section sometime; If index exceeding standard arranged, then add up the index exceeding standard duration, and the index duration is stored and carries out the identification of the risk status of power distribution network overload next time;

Judge that there is the overload phenomenon in power distribution network, but when not reaching risk status, then add up the index exceeding standard duration, and the index duration is stored and carries out the identification of the risk status of power distribution network overload next time;

Judge that there is the overload risk in power distribution network; And according to overload risk class determination methods; Judge that the overload risk is not serious, only carry out the overload risk and report to the police, add up the index exceeding standard duration simultaneously; The index duration is stored, and carry out the identification of the risk status of power distribution network overload next time.

Judge that there is the overload risk in power distribution network, and,, when then carrying out the warning of overload risk, and provide overload risk-aversion control strategy if the overload risk is serious according to overload risk class determination methods; Add up the index exceeding standard duration simultaneously, the index duration is stored, and proceed the continuous identification of overload risk status.

7. power distribution network overload risk status discrimination method as claimed in claim 1 is characterized in that said overload index comprises:

1. overload multiple index K---be used to reflect that single load monitoring point surpasses the degree of permissible load, computing formula does;

2. allow overload time index T---be used to reflect overload duration length, with overload multiple index reflection overload degree;

Wherein, the corresponding corresponding overload time index limit value that allows of overload multiple index standard limited value.

3. the overload multiple is to voltage influence index sensitivity index A---and be used to reflect the degree that rate of qualified voltage that overload causes reduces, its calculation expression is:

A＝f(K,ΔR _U)；

Wherein, Δ R _UFor rate of qualified voltage changes; K is the overload multiple;

4. the overload multiple influences index sensitivity index B to line loss---and be used for reflecting the order of severity that line loss rate that overload causes raises, its calculation expression is:

B＝f(K,ΔR _Line-loss)；

Wherein, Δ R _Line-lossFor line loss rate changes; K is the overload multiple;

5. overload rate index R _Over-load---be used to reflect single load monitoring point overload time degree in the monitoring time section, its expression formula is:

6. comprehensive overload rate index CR _Over-load---be used for reflecting the size of part or overall overload scope, its expression formula is:

8. like the arbitrary described power distribution network overload risk status discrimination method of claim 2-4, it is characterized in that the step of calculating equivalent load is:

If t had n discrete load in the Δ T time before or after the moment, load value is respectively P ₁, P ₂..., P _n, adopt following formula to calculate t equivalent load value P constantly _t:

(1) utilize the arithmetic average method to ask secondary equivalent load P _tComputing formula following:

$P_t=\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{P}_i}{n}=\frac{P_1+P_2+...+P_n}{n}---1)$

(2) utilize the arithmetic average method to ask secondary equivalent load P _tComputing formula following:

$P_t=\sqrt{\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{P}_i^2}{n}}=\sqrt{\frac{P_1^2+P_2^2+...+P_n^2}{n}}---2)$

(3) utilize the geometric mean method to ask secondary equivalent load P _tComputing formula following:

$P_t=\sqrt[n]{P_1\×P_2\×...\×P_n}---3)$ Or

(4) utilize the harmonic-mean method to ask secondary equivalent load P _mComputing formula following:

$P_t=\frac{n}{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\frac{1}{P_i}}=\frac{n}{\frac{1}{P_1}+\frac{1}{P_1}+...+\frac{1}{P_n}}---4)$

9. power distribution network overload risk status discrimination method as claimed in claim 4 is characterized in that, the said load prediction isoeffect curve value that the equivalent load of said foresight aspect generates according to off-line.

10. power distribution network overload risk status discrimination method as claimed in claim 9 is characterized in that said load prediction isoeffect curve is according to said formula 1)-formula 4) curve that is linked to be of the different equivalent load values constantly that calculate.

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